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 For the @samp{-s}, @samp{-e}, and @samp{-se} options, and their long
966 form equivalents, the method used to search the file system for the
967 symbol and/or executable file is the same as that used by the
968 @code{file} command. @xref{Files, ,file}.
970 Many options have both long and short forms; both are shown in the
971 following list. @value{GDBN} also recognizes the long forms if you truncate
972 them, so long as enough of the option is present to be unambiguous.
973 (If you prefer, you can flag option arguments with @samp{--} rather
974 than @samp{-}, though we illustrate the more usual convention.)
976 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
977 @c way, both those who look for -foo and --foo in the index, will find
981 @item -symbols @var{file}
983 @cindex @code{--symbols}
985 Read symbol table from file @var{file}.
987 @item -exec @var{file}
989 @cindex @code{--exec}
991 Use file @var{file} as the executable file to execute when appropriate,
992 and for examining pure data in conjunction with a core dump.
996 Read symbol table from file @var{file} and use it as the executable
999 @item -core @var{file}
1000 @itemx -c @var{file}
1001 @cindex @code{--core}
1003 Use file @var{file} as a core dump to examine.
1005 @item -pid @var{number}
1006 @itemx -p @var{number}
1007 @cindex @code{--pid}
1009 Connect to process ID @var{number}, as with the @code{attach} command.
1011 @item -command @var{file}
1012 @itemx -x @var{file}
1013 @cindex @code{--command}
1015 Execute commands from file @var{file}. The contents of this file is
1016 evaluated exactly as the @code{source} command would.
1017 @xref{Command Files,, Command files}.
1019 @item -eval-command @var{command}
1020 @itemx -ex @var{command}
1021 @cindex @code{--eval-command}
1023 Execute a single @value{GDBN} command.
1025 This option may be used multiple times to call multiple commands. It may
1026 also be interleaved with @samp{-command} as required.
1029 @value{GDBP} -ex 'target sim' -ex 'load' \
1030 -x setbreakpoints -ex 'run' a.out
1033 @item -init-command @var{file}
1034 @itemx -ix @var{file}
1035 @cindex @code{--init-command}
1037 Execute commands from file @var{file} before loading the inferior (but
1038 after loading gdbinit files).
1041 @item -init-eval-command @var{command}
1042 @itemx -iex @var{command}
1043 @cindex @code{--init-eval-command}
1045 Execute a single @value{GDBN} command before loading the inferior (but
1046 after loading gdbinit files).
1049 @item -early-init-command @var{file}
1050 @itemx -eix @var{file}
1051 @cindex @code{--early-init-command}
1053 Execute commands from @var{file} very early in the initialization
1054 process, before any output is produced. @xref{Startup}.
1056 @item -early-init-eval-command @var{command}
1057 @itemx -eiex @var{command}
1058 @cindex @code{--early-init-eval-command}
1059 @cindex @code{-eiex}
1060 Execute a single @value{GDBN} command very early in the initialization
1061 process, before any output is produced.
1063 @item -directory @var{directory}
1064 @itemx -d @var{directory}
1065 @cindex @code{--directory}
1067 Add @var{directory} to the path to search for source and script files.
1071 @cindex @code{--readnow}
1073 Read each symbol file's entire symbol table immediately, rather than
1074 the default, which is to read it incrementally as it is needed.
1075 This makes startup slower, but makes future operations faster.
1078 @anchor{--readnever}
1079 @cindex @code{--readnever}, command-line option
1080 Do not read each symbol file's symbolic debug information. This makes
1081 startup faster but at the expense of not being able to perform
1082 symbolic debugging. DWARF unwind information is also not read,
1083 meaning backtraces may become incomplete or inaccurate. One use of
1084 this is when a user simply wants to do the following sequence: attach,
1085 dump core, detach. Loading the debugging information in this case is
1086 an unnecessary cause of delay.
1090 @subsection Choosing Modes
1092 You can run @value{GDBN} in various alternative modes---for example, in
1093 batch mode or quiet mode.
1101 Do not execute commands found in any initialization files
1102 (@pxref{Initialization Files}).
1107 Do not execute commands found in any home directory initialization
1108 file (@pxref{Initialization Files,,Home directory initialization
1109 file}). The system wide and current directory initialization files
1115 @cindex @code{--quiet}
1116 @cindex @code{--silent}
1118 ``Quiet''. Do not print the introductory and copyright messages. These
1119 messages are also suppressed in batch mode.
1121 @kindex set startup-quietly
1122 @kindex show startup-quietly
1123 This can also be enabled using @code{set startup-quietly on}. The
1124 default is @code{off}. Use @code{show startup-quietly} to see the
1125 current setting. Place @code{set startup-quietly on} into your early
1126 initialization file (@pxref{Initialization Files,,Initialization
1127 Files}) to have future @value{GDBN} sessions startup quietly.
1130 @cindex @code{--batch}
1131 Run in batch mode. Exit with status @code{0} after processing all the
1132 command files specified with @samp{-x} (and all commands from
1133 initialization files, if not inhibited with @samp{-n}). Exit with
1134 nonzero status if an error occurs in executing the @value{GDBN} commands
1135 in the command files. Batch mode also disables pagination, sets unlimited
1136 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1137 off} were in effect (@pxref{Messages/Warnings}).
1139 Batch mode may be useful for running @value{GDBN} as a filter, for
1140 example to download and run a program on another computer; in order to
1141 make this more useful, the message
1144 Program exited normally.
1148 (which is ordinarily issued whenever a program running under
1149 @value{GDBN} control terminates) is not issued when running in batch
1153 @cindex @code{--batch-silent}
1154 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1155 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1156 unaffected). This is much quieter than @samp{-silent} and would be useless
1157 for an interactive session.
1159 This is particularly useful when using targets that give @samp{Loading section}
1160 messages, for example.
1162 Note that targets that give their output via @value{GDBN}, as opposed to
1163 writing directly to @code{stdout}, will also be made silent.
1165 @item -return-child-result
1166 @cindex @code{--return-child-result}
1167 The return code from @value{GDBN} will be the return code from the child
1168 process (the process being debugged), with the following exceptions:
1172 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1173 internal error. In this case the exit code is the same as it would have been
1174 without @samp{-return-child-result}.
1176 The user quits with an explicit value. E.g., @samp{quit 1}.
1178 The child process never runs, or is not allowed to terminate, in which case
1179 the exit code will be -1.
1182 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1183 when @value{GDBN} is being used as a remote program loader or simulator
1188 @cindex @code{--nowindows}
1190 ``No windows''. If @value{GDBN} comes with a graphical user interface
1191 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1192 interface. If no GUI is available, this option has no effect.
1196 @cindex @code{--windows}
1198 If @value{GDBN} includes a GUI, then this option requires it to be
1201 @item -cd @var{directory}
1203 Run @value{GDBN} using @var{directory} as its working directory,
1204 instead of the current directory.
1206 @item -data-directory @var{directory}
1207 @itemx -D @var{directory}
1208 @cindex @code{--data-directory}
1210 Run @value{GDBN} using @var{directory} as its data directory.
1211 The data directory is where @value{GDBN} searches for its
1212 auxiliary files. @xref{Data Files}.
1216 @cindex @code{--fullname}
1218 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1219 subprocess. It tells @value{GDBN} to output the full file name and line
1220 number in a standard, recognizable fashion each time a stack frame is
1221 displayed (which includes each time your program stops). This
1222 recognizable format looks like two @samp{\032} characters, followed by
1223 the file name, line number and character position separated by colons,
1224 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1225 @samp{\032} characters as a signal to display the source code for the
1228 @item -annotate @var{level}
1229 @cindex @code{--annotate}
1230 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1231 effect is identical to using @samp{set annotate @var{level}}
1232 (@pxref{Annotations}). The annotation @var{level} controls how much
1233 information @value{GDBN} prints together with its prompt, values of
1234 expressions, source lines, and other types of output. Level 0 is the
1235 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1236 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1237 that control @value{GDBN}, and level 2 has been deprecated.
1239 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1243 @cindex @code{--args}
1244 Change interpretation of command line so that arguments following the
1245 executable file are passed as command line arguments to the inferior.
1246 This option stops option processing.
1248 @item -baud @var{bps}
1250 @cindex @code{--baud}
1252 Set the line speed (baud rate or bits per second) of any serial
1253 interface used by @value{GDBN} for remote debugging.
1255 @item -l @var{timeout}
1257 Set the timeout (in seconds) of any communication used by @value{GDBN}
1258 for remote debugging.
1260 @item -tty @var{device}
1261 @itemx -t @var{device}
1262 @cindex @code{--tty}
1264 Run using @var{device} for your program's standard input and output.
1265 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1267 @c resolve the situation of these eventually
1269 @cindex @code{--tui}
1270 Activate the @dfn{Text User Interface} when starting. The Text User
1271 Interface manages several text windows on the terminal, showing
1272 source, assembly, registers and @value{GDBN} command outputs
1273 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1274 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1275 Using @value{GDBN} under @sc{gnu} Emacs}).
1277 @item -interpreter @var{interp}
1278 @cindex @code{--interpreter}
1279 Use the interpreter @var{interp} for interface with the controlling
1280 program or device. This option is meant to be set by programs which
1281 communicate with @value{GDBN} using it as a back end.
1282 @xref{Interpreters, , Command Interpreters}.
1284 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1285 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1286 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1287 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1288 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1289 interfaces are no longer supported.
1292 @cindex @code{--write}
1293 Open the executable and core files for both reading and writing. This
1294 is equivalent to the @samp{set write on} command inside @value{GDBN}
1298 @cindex @code{--statistics}
1299 This option causes @value{GDBN} to print statistics about time and
1300 memory usage after it completes each command and returns to the prompt.
1303 @cindex @code{--version}
1304 This option causes @value{GDBN} to print its version number and
1305 no-warranty blurb, and exit.
1307 @item -configuration
1308 @cindex @code{--configuration}
1309 This option causes @value{GDBN} to print details about its build-time
1310 configuration parameters, and then exit. These details can be
1311 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1316 @subsection What @value{GDBN} Does During Startup
1317 @cindex @value{GDBN} startup
1319 Here's the description of what @value{GDBN} does during session startup:
1324 Performs minimal setup required to initialize basic internal state.
1327 @cindex early initialization file
1328 Reads commands from the early initialization file (if any) in your
1329 home directory. Only a restricted set of commands can be placed into
1330 an early initialization file, see @ref{Initialization Files}, for
1334 Executes commands and command files specified by the @samp{-eiex} and
1335 @samp{-eix} command line options in their specified order. Only a
1336 restricted set of commands can be used with @samp{-eiex} and
1337 @samp{eix}, see @ref{Initialization Files}, for details.
1340 Sets up the command interpreter as specified by the command line
1341 (@pxref{Mode Options, interpreter}).
1345 Reads the system wide initialization file and the files from the
1346 system wide initialization directory, @pxref{System Wide Init Files}.
1349 Reads the initialization file (if any) in your home directory and
1350 executes all the commands in that file, @pxref{Home Directory Init
1353 @anchor{Option -init-eval-command}
1355 Executes commands and command files specified by the @samp{-iex} and
1356 @samp{-ix} options in their specified order. Usually you should use the
1357 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1358 settings before @value{GDBN} init files get executed and before inferior
1362 Processes command line options and operands.
1365 Reads and executes the commands from the initialization file (if any)
1366 in the current working directory as long as @samp{set auto-load
1367 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1368 Directory}). This is only done if the current directory is different
1369 from your home directory. Thus, you can have more than one init file,
1370 one generic in your home directory, and another, specific to the
1371 program you are debugging, in the directory where you invoke
1372 @value{GDBN}. @xref{Init File in the Current Directory during
1376 If the command line specified a program to debug, or a process to
1377 attach to, or a core file, @value{GDBN} loads any auto-loaded
1378 scripts provided for the program or for its loaded shared libraries.
1379 @xref{Auto-loading}.
1381 If you wish to disable the auto-loading during startup,
1382 you must do something like the following:
1385 $ gdb -iex "set auto-load python-scripts off" myprogram
1388 Option @samp{-ex} does not work because the auto-loading is then turned
1392 Executes commands and command files specified by the @samp{-ex} and
1393 @samp{-x} options in their specified order. @xref{Command Files}, for
1394 more details about @value{GDBN} command files.
1397 Reads the command history recorded in the @dfn{history file}.
1398 @xref{Command History}, for more details about the command history and the
1399 files where @value{GDBN} records it.
1402 @node Initialization Files
1403 @subsection Initialization Files
1404 @cindex init file name
1406 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1407 from several initialization files. These initialization files use the
1408 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1409 processed by @value{GDBN} in the same way.
1411 To display the list of initialization files loaded by @value{GDBN} at
1412 startup, in the order they will be loaded, you can use @kbd{gdb
1415 @cindex early initialization
1416 The @dfn{early initialization} file is loaded very early in
1417 @value{GDBN}'s initialization process, before the interpreter
1418 (@pxref{Interpreters}) has been initialized, and before the default
1419 target (@pxref{Targets}) is initialized. Only @code{set} or
1420 @code{source} commands should be placed into an early initialization
1421 file, and the only @code{set} commands that can be used are those that
1422 control how @value{GDBN} starts up.
1424 Commands that can be placed into an early initialization file will be
1425 documented as such throughout this manual. Any command that is not
1426 documented as being suitable for an early initialization file should
1427 instead be placed into a general initialization file. Command files
1428 passed to @code{--early-init-command} or @code{-eix} are also early
1429 initialization files, with the same command restrictions. Only
1430 commands that can appear in an early initialization file should be
1431 passed to @code{--early-init-eval-command} or @code{-eiex}.
1433 @cindex general initialization
1434 In contrast, the @dfn{general initialization} files are processed
1435 later, after @value{GDBN} has finished its own internal initialization
1436 process, any valid command can be used in these files.
1438 @cindex initialization file
1439 Throughout the rest of this document the term @dfn{initialization
1440 file} refers to one of the general initialization files, not the early
1441 initialization file. Any discussion of the early initialization file
1442 will specifically mention that it is the early initialization file
1445 As the system wide and home directory initialization files are
1446 processed before most command line options, changes to settings
1447 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1448 command line options and operands.
1450 The following sections describe where @value{GDBN} looks for the early
1451 initialization and initialization files, and the order that the files
1454 @subsubsection Home directory early initialization files
1456 @value{GDBN} initially looks for an early initialization file in the
1457 users home directory@footnote{On DOS/Windows systems, the home
1458 directory is the one pointed to by the @env{HOME} environment
1459 variable.}. There are a number of locations that @value{GDBN} will
1460 search in the home directory, these locations are searched in order
1461 and @value{GDBN} will load the first file that it finds, and
1462 subsequent locations will not be checked.
1464 On non-macOS hosts the locations searched are:
1467 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1468 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1470 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1471 by the environment variable @env{HOME}, if it is defined.
1473 The file @file{.gdbearlyinit} within the directory pointed to by the
1474 environment variable @env{HOME}, if it is defined.
1477 By contrast, on macOS hosts the locations searched are:
1480 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1481 directory pointed to by the environment variable @env{HOME}, if it is
1484 The file @file{.gdbearlyinit} within the directory pointed to by the
1485 environment variable @env{HOME}, if it is defined.
1488 It is possible to prevent the home directory early initialization file
1489 from being loaded using the @samp{-nx} or @samp{-nh} command line
1490 options, @pxref{Mode Options,,Choosing Modes}.
1492 @anchor{System Wide Init Files}
1493 @subsubsection System wide initialization files
1495 There are two locations that are searched for system wide
1496 initialization files. Both of these locations are always checked:
1500 @item @file{system.gdbinit}
1501 This is a single system-wide initialization file. Its location is
1502 specified with the @code{--with-system-gdbinit} configure option
1503 (@pxref{System-wide configuration}). It is loaded first when
1504 @value{GDBN} starts, before command line options have been processed.
1506 @item @file{system.gdbinit.d}
1507 This is the system-wide initialization directory. Its location is
1508 specified with the @code{--with-system-gdbinit-dir} configure option
1509 (@pxref{System-wide configuration}). Files in this directory are
1510 loaded in alphabetical order immediately after @file{system.gdbinit}
1511 (if enabled) when @value{GDBN} starts, before command line options
1512 have been processed. Files need to have a recognized scripting
1513 language extension (@file{.py}/@file{.scm}) or be named with a
1514 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1515 commands. @value{GDBN} will not recurse into any subdirectories of
1520 It is possible to prevent the system wide initialization files from
1521 being loaded using the @samp{-nx} command line option, @pxref{Mode
1522 Options,,Choosing Modes}.
1524 @anchor{Home Directory Init File}
1525 @subsubsection Home directory initialization file
1526 @cindex @file{gdbinit}
1527 @cindex @file{.gdbinit}
1528 @cindex @file{gdb.ini}
1530 After loading the system wide initialization files @value{GDBN} will
1531 look for an initialization file in the users home
1532 directory@footnote{On DOS/Windows systems, the home directory is the
1533 one pointed to by the @env{HOME} environment variable.}. There are a
1534 number of locations that @value{GDBN} will search in the home
1535 directory, these locations are searched in order and @value{GDBN} will
1536 load the first file that it finds, and subsequent locations will not
1539 On non-Apple hosts the locations searched are:
1541 @item $XDG_CONFIG_HOME/gdb/gdbinit
1542 @item $HOME/.config/gdb/gdbinit
1543 @item $HOME/.gdbinit
1546 While on Apple hosts the locations searched are:
1548 @item $HOME/Library/Preferences/gdb/gdbinit
1549 @item $HOME/.gdbinit
1552 It is possible to prevent the home directory initialization file from
1553 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1554 @pxref{Mode Options,,Choosing Modes}.
1556 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1557 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1558 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1559 uses the standard name, but if it finds a @file{gdb.ini} file in your
1560 home directory, it warns you about that and suggests to rename the
1561 file to the standard name.
1563 @anchor{Init File in the Current Directory during Startup}
1564 @subsubsection Local directory initialization file
1566 @value{GDBN} will check the current directory for a file called
1567 @file{.gdbinit}. It is loaded last, after command line options
1568 other than @samp{-x} and @samp{-ex} have been processed. The command
1569 line options @samp{-x} and @samp{-ex} are processed last, after
1570 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1573 If the file in the current directory was already loaded as the home
1574 directory initialization file then it will not be loaded a second
1577 It is possible to prevent the local directory initialization file from
1578 being loaded using the @samp{-nx} command line option, @pxref{Mode
1579 Options,,Choosing Modes}.
1582 @section Quitting @value{GDBN}
1583 @cindex exiting @value{GDBN}
1584 @cindex leaving @value{GDBN}
1587 @kindex quit @r{[}@var{expression}@r{]}
1588 @kindex exit @r{[}@var{expression}@r{]}
1589 @kindex q @r{(@code{quit})}
1590 @item quit @r{[}@var{expression}@r{]}
1591 @itemx exit @r{[}@var{expression}@r{]}
1593 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1594 @code{q}), the @code{exit} command, or type an end-of-file
1595 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1596 @value{GDBN} will terminate normally; otherwise it will terminate using
1597 the result of @var{expression} as the error code.
1601 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1602 terminates the action of any @value{GDBN} command that is in progress and
1603 returns to @value{GDBN} command level. It is safe to type the interrupt
1604 character at any time because @value{GDBN} does not allow it to take effect
1605 until a time when it is safe.
1607 If you have been using @value{GDBN} to control an attached process or
1608 device, you can release it with the @code{detach} command
1609 (@pxref{Attach, ,Debugging an Already-running Process}).
1611 @node Shell Commands
1612 @section Shell Commands
1614 If you need to execute occasional shell commands during your
1615 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1616 just use the @code{shell} command.
1621 @cindex shell escape
1622 @item shell @var{command-string}
1623 @itemx !@var{command-string}
1624 Invoke a standard shell to execute @var{command-string}.
1625 Note that no space is needed between @code{!} and @var{command-string}.
1626 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1627 exists, determines which shell to run. Otherwise @value{GDBN} uses
1628 the default shell (@file{/bin/sh} on GNU and Unix systems,
1629 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1632 The utility @code{make} is often needed in development environments.
1633 You do not have to use the @code{shell} command for this purpose in
1638 @cindex calling make
1639 @item make @var{make-args}
1640 Execute the @code{make} program with the specified
1641 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1647 @cindex send the output of a gdb command to a shell command
1649 @item pipe [@var{command}] | @var{shell_command}
1650 @itemx | [@var{command}] | @var{shell_command}
1651 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1652 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1653 Executes @var{command} and sends its output to @var{shell_command}.
1654 Note that no space is needed around @code{|}.
1655 If no @var{command} is provided, the last command executed is repeated.
1657 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1658 can be used to specify an alternate delimiter string @var{delim} that separates
1659 the @var{command} from the @var{shell_command}.
1692 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1693 this contains a PIPE char
1694 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1695 this contains a PIPE char!
1701 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1702 can be used to examine the exit status of the last shell command launched
1703 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1704 @xref{Convenience Vars,, Convenience Variables}.
1706 @node Logging Output
1707 @section Logging Output
1708 @cindex logging @value{GDBN} output
1709 @cindex save @value{GDBN} output to a file
1711 You may want to save the output of @value{GDBN} commands to a file.
1712 There are several commands to control @value{GDBN}'s logging.
1715 @kindex set logging enabled
1716 @item set logging enabled [on|off]
1717 Enable or disable logging.
1718 @cindex logging file name
1719 @item set logging file @var{file}
1720 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1721 @item set logging overwrite [on|off]
1722 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1723 you want @code{set logging enabled on} to overwrite the logfile instead.
1724 @item set logging redirect [on|off]
1725 By default, @value{GDBN} output will go to both the terminal and the logfile.
1726 Set @code{redirect} if you want output to go only to the log file.
1727 @item set logging debugredirect [on|off]
1728 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1729 Set @code{debugredirect} if you want debug output to go only to the log file.
1730 @kindex show logging
1732 Show the current values of the logging settings.
1735 You can also redirect the output of a @value{GDBN} command to a
1736 shell command. @xref{pipe}.
1738 @chapter @value{GDBN} Commands
1740 You can abbreviate a @value{GDBN} command to the first few letters of the command
1741 name, if that abbreviation is unambiguous; and you can repeat certain
1742 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1743 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1744 show you the alternatives available, if there is more than one possibility).
1747 * Command Syntax:: How to give commands to @value{GDBN}
1748 * Command Settings:: How to change default behavior of commands
1749 * Completion:: Command completion
1750 * Command Options:: Command options
1751 * Help:: How to ask @value{GDBN} for help
1754 @node Command Syntax
1755 @section Command Syntax
1757 A @value{GDBN} command is a single line of input. There is no limit on
1758 how long it can be. It starts with a command name, which is followed by
1759 arguments whose meaning depends on the command name. For example, the
1760 command @code{step} accepts an argument which is the number of times to
1761 step, as in @samp{step 5}. You can also use the @code{step} command
1762 with no arguments. Some commands do not allow any arguments.
1764 @cindex abbreviation
1765 @value{GDBN} command names may always be truncated if that abbreviation is
1766 unambiguous. Other possible command abbreviations are listed in the
1767 documentation for individual commands. In some cases, even ambiguous
1768 abbreviations are allowed; for example, @code{s} is specially defined as
1769 equivalent to @code{step} even though there are other commands whose
1770 names start with @code{s}. You can test abbreviations by using them as
1771 arguments to the @code{help} command.
1773 @cindex repeating commands
1774 @kindex RET @r{(repeat last command)}
1775 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1776 repeat the previous command. Certain commands (for example, @code{run})
1777 will not repeat this way; these are commands whose unintentional
1778 repetition might cause trouble and which you are unlikely to want to
1779 repeat. User-defined commands can disable this feature; see
1780 @ref{Define, dont-repeat}.
1782 The @code{list} and @code{x} commands, when you repeat them with
1783 @key{RET}, construct new arguments rather than repeating
1784 exactly as typed. This permits easy scanning of source or memory.
1786 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1787 output, in a way similar to the common utility @code{more}
1788 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1789 @key{RET} too many in this situation, @value{GDBN} disables command
1790 repetition after any command that generates this sort of display.
1792 @kindex # @r{(a comment)}
1794 Any text from a @kbd{#} to the end of the line is a comment; it does
1795 nothing. This is useful mainly in command files (@pxref{Command
1796 Files,,Command Files}).
1798 @cindex repeating command sequences
1799 @kindex Ctrl-o @r{(operate-and-get-next)}
1800 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1801 commands. This command accepts the current line, like @key{RET}, and
1802 then fetches the next line relative to the current line from the history
1806 @node Command Settings
1807 @section Command Settings
1808 @cindex default behavior of commands, changing
1809 @cindex default settings, changing
1811 Many commands change their behavior according to command-specific
1812 variables or settings. These settings can be changed with the
1813 @code{set} subcommands. For example, the @code{print} command
1814 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1815 settings changeable with the commands @code{set print elements
1816 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1818 You can change these settings to your preference in the gdbinit files
1819 loaded at @value{GDBN} startup. @xref{Startup}.
1821 The settings can also be changed interactively during the debugging
1822 session. For example, to change the limit of array elements to print,
1823 you can do the following:
1825 (@value{GDBN}) set print elements 10
1826 (@value{GDBN}) print some_array
1827 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1830 The above @code{set print elements 10} command changes the number of
1831 elements to print from the default of 200 to 10. If you only intend
1832 this limit of 10 to be used for printing @code{some_array}, then you
1833 must restore the limit back to 200, with @code{set print elements
1836 Some commands allow overriding settings with command options. For
1837 example, the @code{print} command supports a number of options that
1838 allow overriding relevant global print settings as set by @code{set
1839 print} subcommands. @xref{print options}. The example above could be
1842 (@value{GDBN}) print -elements 10 -- some_array
1843 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1846 Alternatively, you can use the @code{with} command to change a setting
1847 temporarily, for the duration of a command invocation.
1850 @kindex with command
1851 @kindex w @r{(@code{with})}
1853 @cindex temporarily change settings
1854 @item with @var{setting} [@var{value}] [-- @var{command}]
1855 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1856 Temporarily set @var{setting} to @var{value} for the duration of
1859 @var{setting} is any setting you can change with the @code{set}
1860 subcommands. @var{value} is the value to assign to @code{setting}
1861 while running @code{command}.
1863 If no @var{command} is provided, the last command executed is
1866 If a @var{command} is provided, it must be preceded by a double dash
1867 (@code{--}) separator. This is required because some settings accept
1868 free-form arguments, such as expressions or filenames.
1870 For example, the command
1872 (@value{GDBN}) with print array on -- print some_array
1875 is equivalent to the following 3 commands:
1877 (@value{GDBN}) set print array on
1878 (@value{GDBN}) print some_array
1879 (@value{GDBN}) set print array off
1882 The @code{with} command is particularly useful when you want to
1883 override a setting while running user-defined commands, or commands
1884 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1887 (@value{GDBN}) with print pretty on -- my_complex_command
1890 To change several settings for the same command, you can nest
1891 @code{with} commands. For example, @code{with language ada -- with
1892 print elements 10} temporarily changes the language to Ada and sets a
1893 limit of 10 elements to print for arrays and strings.
1898 @section Command Completion
1901 @cindex word completion
1902 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1903 only one possibility; it can also show you what the valid possibilities
1904 are for the next word in a command, at any time. This works for @value{GDBN}
1905 commands, @value{GDBN} subcommands, command options, and the names of symbols
1908 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1909 of a word. If there is only one possibility, @value{GDBN} fills in the
1910 word, and waits for you to finish the command (or press @key{RET} to
1911 enter it). For example, if you type
1913 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1914 @c complete accuracy in these examples; space introduced for clarity.
1915 @c If texinfo enhancements make it unnecessary, it would be nice to
1916 @c replace " @key" by "@key" in the following...
1918 (@value{GDBP}) info bre@key{TAB}
1922 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1923 the only @code{info} subcommand beginning with @samp{bre}:
1926 (@value{GDBP}) info breakpoints
1930 You can either press @key{RET} at this point, to run the @code{info
1931 breakpoints} command, or backspace and enter something else, if
1932 @samp{breakpoints} does not look like the command you expected. (If you
1933 were sure you wanted @code{info breakpoints} in the first place, you
1934 might as well just type @key{RET} immediately after @samp{info bre},
1935 to exploit command abbreviations rather than command completion).
1937 If there is more than one possibility for the next word when you press
1938 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1939 characters and try again, or just press @key{TAB} a second time;
1940 @value{GDBN} displays all the possible completions for that word. For
1941 example, you might want to set a breakpoint on a subroutine whose name
1942 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1943 just sounds the bell. Typing @key{TAB} again displays all the
1944 function names in your program that begin with those characters, for
1948 (@value{GDBP}) b make_@key{TAB}
1949 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1950 make_a_section_from_file make_environ
1951 make_abs_section make_function_type
1952 make_blockvector make_pointer_type
1953 make_cleanup make_reference_type
1954 make_command make_symbol_completion_list
1955 (@value{GDBP}) b make_
1959 After displaying the available possibilities, @value{GDBN} copies your
1960 partial input (@samp{b make_} in the example) so you can finish the
1963 If the command you are trying to complete expects either a keyword or a
1964 number to follow, then @samp{NUMBER} will be shown among the available
1965 completions, for example:
1968 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1970 (@value{GDBP}) print -elements@tie{}
1974 Here, the option expects a number (e.g., @code{100}), not literal
1975 @code{NUMBER}. Such metasyntactical arguments are always presented in
1978 If you just want to see the list of alternatives in the first place, you
1979 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1980 means @kbd{@key{META} ?}. You can type this either by holding down a
1981 key designated as the @key{META} shift on your keyboard (if there is
1982 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1984 If the number of possible completions is large, @value{GDBN} will
1985 print as much of the list as it has collected, as well as a message
1986 indicating that the list may be truncated.
1989 (@value{GDBP}) b m@key{TAB}@key{TAB}
1991 <... the rest of the possible completions ...>
1992 *** List may be truncated, max-completions reached. ***
1997 This behavior can be controlled with the following commands:
2000 @kindex set max-completions
2001 @item set max-completions @var{limit}
2002 @itemx set max-completions unlimited
2003 Set the maximum number of completion candidates. @value{GDBN} will
2004 stop looking for more completions once it collects this many candidates.
2005 This is useful when completing on things like function names as collecting
2006 all the possible candidates can be time consuming.
2007 The default value is 200. A value of zero disables tab-completion.
2008 Note that setting either no limit or a very large limit can make
2010 @kindex show max-completions
2011 @item show max-completions
2012 Show the maximum number of candidates that @value{GDBN} will collect and show
2016 @cindex quotes in commands
2017 @cindex completion of quoted strings
2018 Sometimes the string you need, while logically a ``word'', may contain
2019 parentheses or other characters that @value{GDBN} normally excludes from
2020 its notion of a word. To permit word completion to work in this
2021 situation, you may enclose words in @code{'} (single quote marks) in
2022 @value{GDBN} commands.
2024 A likely situation where you might need this is in typing an
2025 expression that involves a C@t{++} symbol name with template
2026 parameters. This is because when completing expressions, GDB treats
2027 the @samp{<} character as word delimiter, assuming that it's the
2028 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2031 For example, when you want to call a C@t{++} template function
2032 interactively using the @code{print} or @code{call} commands, you may
2033 need to distinguish whether you mean the version of @code{name} that
2034 was specialized for @code{int}, @code{name<int>()}, or the version
2035 that was specialized for @code{float}, @code{name<float>()}. To use
2036 the word-completion facilities in this situation, type a single quote
2037 @code{'} at the beginning of the function name. This alerts
2038 @value{GDBN} that it may need to consider more information than usual
2039 when you press @key{TAB} or @kbd{M-?} to request word completion:
2042 (@value{GDBP}) p 'func<@kbd{M-?}
2043 func<int>() func<float>()
2044 (@value{GDBP}) p 'func<
2047 When setting breakpoints however (@pxref{Location Specifications}), you don't
2048 usually need to type a quote before the function name, because
2049 @value{GDBN} understands that you want to set a breakpoint on a
2053 (@value{GDBP}) b func<@kbd{M-?}
2054 func<int>() func<float>()
2055 (@value{GDBP}) b func<
2058 This is true even in the case of typing the name of C@t{++} overloaded
2059 functions (multiple definitions of the same function, distinguished by
2060 argument type). For example, when you want to set a breakpoint you
2061 don't need to distinguish whether you mean the version of @code{name}
2062 that takes an @code{int} parameter, @code{name(int)}, or the version
2063 that takes a @code{float} parameter, @code{name(float)}.
2066 (@value{GDBP}) b bubble(@kbd{M-?}
2067 bubble(int) bubble(double)
2068 (@value{GDBP}) b bubble(dou@kbd{M-?}
2072 See @ref{quoting names} for a description of other scenarios that
2075 For more information about overloaded functions, see @ref{C Plus Plus
2076 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2077 overload-resolution off} to disable overload resolution;
2078 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2080 @cindex completion of structure field names
2081 @cindex structure field name completion
2082 @cindex completion of union field names
2083 @cindex union field name completion
2084 When completing in an expression which looks up a field in a
2085 structure, @value{GDBN} also tries@footnote{The completer can be
2086 confused by certain kinds of invalid expressions. Also, it only
2087 examines the static type of the expression, not the dynamic type.} to
2088 limit completions to the field names available in the type of the
2092 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2093 magic to_fputs to_rewind
2094 to_data to_isatty to_write
2095 to_delete to_put to_write_async_safe
2100 This is because the @code{gdb_stdout} is a variable of the type
2101 @code{struct ui_file} that is defined in @value{GDBN} sources as
2108 ui_file_flush_ftype *to_flush;
2109 ui_file_write_ftype *to_write;
2110 ui_file_write_async_safe_ftype *to_write_async_safe;
2111 ui_file_fputs_ftype *to_fputs;
2112 ui_file_read_ftype *to_read;
2113 ui_file_delete_ftype *to_delete;
2114 ui_file_isatty_ftype *to_isatty;
2115 ui_file_rewind_ftype *to_rewind;
2116 ui_file_put_ftype *to_put;
2121 @node Command Options
2122 @section Command options
2124 @cindex command options
2125 Some commands accept options starting with a leading dash. For
2126 example, @code{print -pretty}. Similarly to command names, you can
2127 abbreviate a @value{GDBN} option to the first few letters of the
2128 option name, if that abbreviation is unambiguous, and you can also use
2129 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2130 in an option (or to show you the alternatives available, if there is
2131 more than one possibility).
2133 @cindex command options, raw input
2134 Some commands take raw input as argument. For example, the print
2135 command processes arbitrary expressions in any of the languages
2136 supported by @value{GDBN}. With such commands, because raw input may
2137 start with a leading dash that would be confused with an option or any
2138 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2139 -pretty} or printing negative @code{p}?), if you specify any command
2140 option, then you must use a double-dash (@code{--}) delimiter to
2141 indicate the end of options.
2143 @cindex command options, boolean
2145 Some options are described as accepting an argument which can be
2146 either @code{on} or @code{off}. These are known as @dfn{boolean
2147 options}. Similarly to boolean settings commands---@code{on} and
2148 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2149 @code{enable} can also be used as ``true'' value, and any of @code{0},
2150 @code{no} and @code{disable} can also be used as ``false'' value. You
2151 can also omit a ``true'' value, as it is implied by default.
2153 For example, these are equivalent:
2156 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2157 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2160 You can discover the set of options some command accepts by completing
2161 on @code{-} after the command name. For example:
2164 (@value{GDBP}) print -@key{TAB}@key{TAB}
2165 -address -max-depth -object -static-members
2166 -array -memory-tag-violations -pretty -symbol
2167 -array-indexes -nibbles -raw-values -union
2168 -elements -null-stop -repeats -vtbl
2171 Completion will in some cases guide you with a suggestion of what kind
2172 of argument an option expects. For example:
2175 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2179 Here, the option expects a number (e.g., @code{100}), not literal
2180 @code{NUMBER}. Such metasyntactical arguments are always presented in
2183 (For more on using the @code{print} command, see @ref{Data, ,Examining
2187 @section Getting Help
2188 @cindex online documentation
2191 You can always ask @value{GDBN} itself for information on its commands,
2192 using the command @code{help}.
2195 @kindex h @r{(@code{help})}
2198 You can use @code{help} (abbreviated @code{h}) with no arguments to
2199 display a short list of named classes of commands:
2203 List of classes of commands:
2205 aliases -- User-defined aliases of other commands
2206 breakpoints -- Making program stop at certain points
2207 data -- Examining data
2208 files -- Specifying and examining files
2209 internals -- Maintenance commands
2210 obscure -- Obscure features
2211 running -- Running the program
2212 stack -- Examining the stack
2213 status -- Status inquiries
2214 support -- Support facilities
2215 tracepoints -- Tracing of program execution without
2216 stopping the program
2217 user-defined -- User-defined commands
2219 Type "help" followed by a class name for a list of
2220 commands in that class.
2221 Type "help" followed by command name for full
2223 Command name abbreviations are allowed if unambiguous.
2226 @c the above line break eliminates huge line overfull...
2228 @item help @var{class}
2229 Using one of the general help classes as an argument, you can get a
2230 list of the individual commands in that class. If a command has
2231 aliases, the aliases are given after the command name, separated by
2232 commas. If an alias has default arguments, the full definition of
2233 the alias is given after the first line.
2234 For example, here is the help display for the class @code{status}:
2237 (@value{GDBP}) help status
2242 @c Line break in "show" line falsifies real output, but needed
2243 @c to fit in smallbook page size.
2244 info, inf, i -- Generic command for showing things
2245 about the program being debugged
2246 info address, iamain -- Describe where symbol SYM is stored.
2247 alias iamain = info address main
2248 info all-registers -- List of all registers and their contents,
2249 for selected stack frame.
2251 show, info set -- Generic command for showing things
2254 Type "help" followed by command name for full
2256 Command name abbreviations are allowed if unambiguous.
2260 @item help @var{command}
2261 With a command name as @code{help} argument, @value{GDBN} displays a
2262 short paragraph on how to use that command. If that command has
2263 one or more aliases, @value{GDBN} will display a first line with
2264 the command name and all its aliases separated by commas.
2265 This first line will be followed by the full definition of all aliases
2266 having default arguments.
2269 @item apropos [-v] @var{regexp}
2270 The @code{apropos} command searches through all of the @value{GDBN}
2271 commands, and their documentation, for the regular expression specified in
2272 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2273 which stands for @samp{verbose}, indicates to output the full documentation
2274 of the matching commands and highlight the parts of the documentation
2275 matching @var{regexp}. For example:
2286 alias -- Define a new command that is an alias of an existing command
2287 aliases -- User-defined aliases of other commands
2295 apropos -v cut.*thread apply
2299 results in the below output, where @samp{cut for 'thread apply}
2300 is highlighted if styling is enabled.
2304 taas -- Apply a command to all threads (ignoring errors
2307 shortcut for 'thread apply all -s COMMAND'
2309 tfaas -- Apply a command to all frames of all threads
2310 (ignoring errors and empty output).
2311 Usage: tfaas COMMAND
2312 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2317 @item complete @var{args}
2318 The @code{complete @var{args}} command lists all the possible completions
2319 for the beginning of a command. Use @var{args} to specify the beginning of the
2320 command you want completed. For example:
2326 @noindent results in:
2337 @noindent This is intended for use by @sc{gnu} Emacs.
2340 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2341 and @code{show} to inquire about the state of your program, or the state
2342 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2343 manual introduces each of them in the appropriate context. The listings
2344 under @code{info} and under @code{show} in the Command, Variable, and
2345 Function Index point to all the sub-commands. @xref{Command and Variable
2351 @kindex i @r{(@code{info})}
2353 This command (abbreviated @code{i}) is for describing the state of your
2354 program. For example, you can show the arguments passed to a function
2355 with @code{info args}, list the registers currently in use with @code{info
2356 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2357 You can get a complete list of the @code{info} sub-commands with
2358 @w{@code{help info}}.
2362 You can assign the result of an expression to an environment variable with
2363 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2364 @code{set prompt $}.
2368 In contrast to @code{info}, @code{show} is for describing the state of
2369 @value{GDBN} itself.
2370 You can change most of the things you can @code{show}, by using the
2371 related command @code{set}; for example, you can control what number
2372 system is used for displays with @code{set radix}, or simply inquire
2373 which is currently in use with @code{show radix}.
2376 To display all the settable parameters and their current
2377 values, you can use @code{show} with no arguments; you may also use
2378 @code{info set}. Both commands produce the same display.
2379 @c FIXME: "info set" violates the rule that "info" is for state of
2380 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2381 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2385 Here are several miscellaneous @code{show} subcommands, all of which are
2386 exceptional in lacking corresponding @code{set} commands:
2389 @kindex show version
2390 @cindex @value{GDBN} version number
2392 Show what version of @value{GDBN} is running. You should include this
2393 information in @value{GDBN} bug-reports. If multiple versions of
2394 @value{GDBN} are in use at your site, you may need to determine which
2395 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2396 commands are introduced, and old ones may wither away. Also, many
2397 system vendors ship variant versions of @value{GDBN}, and there are
2398 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2399 The version number is the same as the one announced when you start
2402 @kindex show copying
2403 @kindex info copying
2404 @cindex display @value{GDBN} copyright
2407 Display information about permission for copying @value{GDBN}.
2409 @kindex show warranty
2410 @kindex info warranty
2412 @itemx info warranty
2413 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2414 if your version of @value{GDBN} comes with one.
2416 @kindex show configuration
2417 @item show configuration
2418 Display detailed information about the way @value{GDBN} was configured
2419 when it was built. This displays the optional arguments passed to the
2420 @file{configure} script and also configuration parameters detected
2421 automatically by @command{configure}. When reporting a @value{GDBN}
2422 bug (@pxref{GDB Bugs}), it is important to include this information in
2428 @chapter Running Programs Under @value{GDBN}
2430 When you run a program under @value{GDBN}, you must first generate
2431 debugging information when you compile it.
2433 You may start @value{GDBN} with its arguments, if any, in an environment
2434 of your choice. If you are doing native debugging, you may redirect
2435 your program's input and output, debug an already running process, or
2436 kill a child process.
2439 * Compilation:: Compiling for debugging
2440 * Starting:: Starting your program
2441 * Arguments:: Your program's arguments
2442 * Environment:: Your program's environment
2444 * Working Directory:: Your program's working directory
2445 * Input/Output:: Your program's input and output
2446 * Attach:: Debugging an already-running process
2447 * Kill Process:: Killing the child process
2448 * Inferiors Connections and Programs:: Debugging multiple inferiors
2449 connections and programs
2450 * Threads:: Debugging programs with multiple threads
2451 * Forks:: Debugging forks
2452 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2456 @section Compiling for Debugging
2458 In order to debug a program effectively, you need to generate
2459 debugging information when you compile it. This debugging information
2460 is stored in the object file; it describes the data type of each
2461 variable or function and the correspondence between source line numbers
2462 and addresses in the executable code.
2464 To request debugging information, specify the @samp{-g} option when you run
2467 Programs that are to be shipped to your customers are compiled with
2468 optimizations, using the @samp{-O} compiler option. However, some
2469 compilers are unable to handle the @samp{-g} and @samp{-O} options
2470 together. Using those compilers, you cannot generate optimized
2471 executables containing debugging information.
2473 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2474 without @samp{-O}, making it possible to debug optimized code. We
2475 recommend that you @emph{always} use @samp{-g} whenever you compile a
2476 program. You may think your program is correct, but there is no sense
2477 in pushing your luck. For more information, see @ref{Optimized Code}.
2479 Older versions of the @sc{gnu} C compiler permitted a variant option
2480 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2481 format; if your @sc{gnu} C compiler has this option, do not use it.
2483 @value{GDBN} knows about preprocessor macros and can show you their
2484 expansion (@pxref{Macros}). Most compilers do not include information
2485 about preprocessor macros in the debugging information if you specify
2486 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2487 the @sc{gnu} C compiler, provides macro information if you are using
2488 the DWARF debugging format, and specify the option @option{-g3}.
2490 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2491 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2492 information on @value{NGCC} options affecting debug information.
2494 You will have the best debugging experience if you use the latest
2495 version of the DWARF debugging format that your compiler supports.
2496 DWARF is currently the most expressive and best supported debugging
2497 format in @value{GDBN}.
2501 @section Starting your Program
2507 @kindex r @r{(@code{run})}
2510 Use the @code{run} command to start your program under @value{GDBN}.
2511 You must first specify the program name with an argument to
2512 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2513 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2514 command (@pxref{Files, ,Commands to Specify Files}).
2518 If you are running your program in an execution environment that
2519 supports processes, @code{run} creates an inferior process and makes
2520 that process run your program. In some environments without processes,
2521 @code{run} jumps to the start of your program. Other targets,
2522 like @samp{remote}, are always running. If you get an error
2523 message like this one:
2526 The "remote" target does not support "run".
2527 Try "help target" or "continue".
2531 then use @code{continue} to run your program. You may need @code{load}
2532 first (@pxref{load}).
2534 The execution of a program is affected by certain information it
2535 receives from its superior. @value{GDBN} provides ways to specify this
2536 information, which you must do @emph{before} starting your program. (You
2537 can change it after starting your program, but such changes only affect
2538 your program the next time you start it.) This information may be
2539 divided into four categories:
2542 @item The @emph{arguments.}
2543 Specify the arguments to give your program as the arguments of the
2544 @code{run} command. If a shell is available on your target, the shell
2545 is used to pass the arguments, so that you may use normal conventions
2546 (such as wildcard expansion or variable substitution) in describing
2548 In Unix systems, you can control which shell is used with the
2549 @env{SHELL} environment variable. If you do not define @env{SHELL},
2550 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2551 use of any shell with the @code{set startup-with-shell} command (see
2554 @item The @emph{environment.}
2555 Your program normally inherits its environment from @value{GDBN}, but you can
2556 use the @value{GDBN} commands @code{set environment} and @code{unset
2557 environment} to change parts of the environment that affect
2558 your program. @xref{Environment, ,Your Program's Environment}.
2560 @item The @emph{working directory.}
2561 You can set your program's working directory with the command
2562 @kbd{set cwd}. If you do not set any working directory with this
2563 command, your program will inherit @value{GDBN}'s working directory if
2564 native debugging, or the remote server's working directory if remote
2565 debugging. @xref{Working Directory, ,Your Program's Working
2568 @item The @emph{standard input and output.}
2569 Your program normally uses the same device for standard input and
2570 standard output as @value{GDBN} is using. You can redirect input and output
2571 in the @code{run} command line, or you can use the @code{tty} command to
2572 set a different device for your program.
2573 @xref{Input/Output, ,Your Program's Input and Output}.
2576 @emph{Warning:} While input and output redirection work, you cannot use
2577 pipes to pass the output of the program you are debugging to another
2578 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2582 When you issue the @code{run} command, your program begins to execute
2583 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2584 of how to arrange for your program to stop. Once your program has
2585 stopped, you may call functions in your program, using the @code{print}
2586 or @code{call} commands. @xref{Data, ,Examining Data}.
2588 If the modification time of your symbol file has changed since the last
2589 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2590 table, and reads it again. When it does this, @value{GDBN} tries to retain
2591 your current breakpoints.
2596 @cindex run to main procedure
2597 The name of the main procedure can vary from language to language.
2598 With C or C@t{++}, the main procedure name is always @code{main}, but
2599 other languages such as Ada do not require a specific name for their
2600 main procedure. The debugger provides a convenient way to start the
2601 execution of the program and to stop at the beginning of the main
2602 procedure, depending on the language used.
2604 The @samp{start} command does the equivalent of setting a temporary
2605 breakpoint at the beginning of the main procedure and then invoking
2606 the @samp{run} command.
2608 @cindex elaboration phase
2609 Some programs contain an @dfn{elaboration} phase where some startup code is
2610 executed before the main procedure is called. This depends on the
2611 languages used to write your program. In C@t{++}, for instance,
2612 constructors for static and global objects are executed before
2613 @code{main} is called. It is therefore possible that the debugger stops
2614 before reaching the main procedure. However, the temporary breakpoint
2615 will remain to halt execution.
2617 Specify the arguments to give to your program as arguments to the
2618 @samp{start} command. These arguments will be given verbatim to the
2619 underlying @samp{run} command. Note that the same arguments will be
2620 reused if no argument is provided during subsequent calls to
2621 @samp{start} or @samp{run}.
2623 It is sometimes necessary to debug the program during elaboration. In
2624 these cases, using the @code{start} command would stop the execution
2625 of your program too late, as the program would have already completed
2626 the elaboration phase. Under these circumstances, either insert
2627 breakpoints in your elaboration code before running your program or
2628 use the @code{starti} command.
2632 @cindex run to first instruction
2633 The @samp{starti} command does the equivalent of setting a temporary
2634 breakpoint at the first instruction of a program's execution and then
2635 invoking the @samp{run} command. For programs containing an
2636 elaboration phase, the @code{starti} command will stop execution at
2637 the start of the elaboration phase.
2639 @anchor{set exec-wrapper}
2640 @kindex set exec-wrapper
2641 @item set exec-wrapper @var{wrapper}
2642 @itemx show exec-wrapper
2643 @itemx unset exec-wrapper
2644 When @samp{exec-wrapper} is set, the specified wrapper is used to
2645 launch programs for debugging. @value{GDBN} starts your program
2646 with a shell command of the form @kbd{exec @var{wrapper}
2647 @var{program}}. Quoting is added to @var{program} and its
2648 arguments, but not to @var{wrapper}, so you should add quotes if
2649 appropriate for your shell. The wrapper runs until it executes
2650 your program, and then @value{GDBN} takes control.
2652 You can use any program that eventually calls @code{execve} with
2653 its arguments as a wrapper. Several standard Unix utilities do
2654 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2655 with @code{exec "$@@"} will also work.
2657 For example, you can use @code{env} to pass an environment variable to
2658 the debugged program, without setting the variable in your shell's
2662 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2666 This command is available when debugging locally on most targets, excluding
2667 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2669 @kindex set startup-with-shell
2670 @anchor{set startup-with-shell}
2671 @item set startup-with-shell
2672 @itemx set startup-with-shell on
2673 @itemx set startup-with-shell off
2674 @itemx show startup-with-shell
2675 On Unix systems, by default, if a shell is available on your target,
2676 @value{GDBN}) uses it to start your program. Arguments of the
2677 @code{run} command are passed to the shell, which does variable
2678 substitution, expands wildcard characters and performs redirection of
2679 I/O. In some circumstances, it may be useful to disable such use of a
2680 shell, for example, when debugging the shell itself or diagnosing
2681 startup failures such as:
2685 Starting program: ./a.out
2686 During startup program terminated with signal SIGSEGV, Segmentation fault.
2690 which indicates the shell or the wrapper specified with
2691 @samp{exec-wrapper} crashed, not your program. Most often, this is
2692 caused by something odd in your shell's non-interactive mode
2693 initialization file---such as @file{.cshrc} for C-shell,
2694 $@file{.zshenv} for the Z shell, or the file specified in the
2695 @env{BASH_ENV} environment variable for BASH.
2697 @anchor{set auto-connect-native-target}
2698 @kindex set auto-connect-native-target
2699 @item set auto-connect-native-target
2700 @itemx set auto-connect-native-target on
2701 @itemx set auto-connect-native-target off
2702 @itemx show auto-connect-native-target
2704 By default, if the current inferior is not connected to any target yet
2705 (e.g., with @code{target remote}), the @code{run} command starts your
2706 program as a native process under @value{GDBN}, on your local machine.
2707 If you're sure you don't want to debug programs on your local machine,
2708 you can tell @value{GDBN} to not connect to the native target
2709 automatically with the @code{set auto-connect-native-target off}
2712 If @code{on}, which is the default, and if the current inferior is not
2713 connected to a target already, the @code{run} command automaticaly
2714 connects to the native target, if one is available.
2716 If @code{off}, and if the current inferior is not connected to a
2717 target already, the @code{run} command fails with an error:
2721 Don't know how to run. Try "help target".
2724 If the current inferior is already connected to a target, @value{GDBN}
2725 always uses it with the @code{run} command.
2727 In any case, you can explicitly connect to the native target with the
2728 @code{target native} command. For example,
2731 (@value{GDBP}) set auto-connect-native-target off
2733 Don't know how to run. Try "help target".
2734 (@value{GDBP}) target native
2736 Starting program: ./a.out
2737 [Inferior 1 (process 10421) exited normally]
2740 In case you connected explicitly to the @code{native} target,
2741 @value{GDBN} remains connected even if all inferiors exit, ready for
2742 the next @code{run} command. Use the @code{disconnect} command to
2745 Examples of other commands that likewise respect the
2746 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2747 proc}, @code{info os}.
2749 @kindex set disable-randomization
2750 @item set disable-randomization
2751 @itemx set disable-randomization on
2752 This option (enabled by default in @value{GDBN}) will turn off the native
2753 randomization of the virtual address space of the started program. This option
2754 is useful for multiple debugging sessions to make the execution better
2755 reproducible and memory addresses reusable across debugging sessions.
2757 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2758 On @sc{gnu}/Linux you can get the same behavior using
2761 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2764 @item set disable-randomization off
2765 Leave the behavior of the started executable unchanged. Some bugs rear their
2766 ugly heads only when the program is loaded at certain addresses. If your bug
2767 disappears when you run the program under @value{GDBN}, that might be because
2768 @value{GDBN} by default disables the address randomization on platforms, such
2769 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2770 disable-randomization off} to try to reproduce such elusive bugs.
2772 On targets where it is available, virtual address space randomization
2773 protects the programs against certain kinds of security attacks. In these
2774 cases the attacker needs to know the exact location of a concrete executable
2775 code. Randomizing its location makes it impossible to inject jumps misusing
2776 a code at its expected addresses.
2778 Prelinking shared libraries provides a startup performance advantage but it
2779 makes addresses in these libraries predictable for privileged processes by
2780 having just unprivileged access at the target system. Reading the shared
2781 library binary gives enough information for assembling the malicious code
2782 misusing it. Still even a prelinked shared library can get loaded at a new
2783 random address just requiring the regular relocation process during the
2784 startup. Shared libraries not already prelinked are always loaded at
2785 a randomly chosen address.
2787 Position independent executables (PIE) contain position independent code
2788 similar to the shared libraries and therefore such executables get loaded at
2789 a randomly chosen address upon startup. PIE executables always load even
2790 already prelinked shared libraries at a random address. You can build such
2791 executable using @command{gcc -fPIE -pie}.
2793 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2794 (as long as the randomization is enabled).
2796 @item show disable-randomization
2797 Show the current setting of the explicit disable of the native randomization of
2798 the virtual address space of the started program.
2803 @section Your Program's Arguments
2805 @cindex arguments (to your program)
2806 The arguments to your program can be specified by the arguments of the
2808 They are passed to a shell, which expands wildcard characters and
2809 performs redirection of I/O, and thence to your program. Your
2810 @env{SHELL} environment variable (if it exists) specifies what shell
2811 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2812 the default shell (@file{/bin/sh} on Unix).
2814 On non-Unix systems, the program is usually invoked directly by
2815 @value{GDBN}, which emulates I/O redirection via the appropriate system
2816 calls, and the wildcard characters are expanded by the startup code of
2817 the program, not by the shell.
2819 @code{run} with no arguments uses the same arguments used by the previous
2820 @code{run}, or those set by the @code{set args} command.
2825 Specify the arguments to be used the next time your program is run. If
2826 @code{set args} has no arguments, @code{run} executes your program
2827 with no arguments. Once you have run your program with arguments,
2828 using @code{set args} before the next @code{run} is the only way to run
2829 it again without arguments.
2833 Show the arguments to give your program when it is started.
2837 @section Your Program's Environment
2839 @cindex environment (of your program)
2840 The @dfn{environment} consists of a set of environment variables and
2841 their values. Environment variables conventionally record such things as
2842 your user name, your home directory, your terminal type, and your search
2843 path for programs to run. Usually you set up environment variables with
2844 the shell and they are inherited by all the other programs you run. When
2845 debugging, it can be useful to try running your program with a modified
2846 environment without having to start @value{GDBN} over again.
2850 @item path @var{directory}
2851 Add @var{directory} to the front of the @env{PATH} environment variable
2852 (the search path for executables) that will be passed to your program.
2853 The value of @env{PATH} used by @value{GDBN} does not change.
2854 You may specify several directory names, separated by whitespace or by a
2855 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2856 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2857 is moved to the front, so it is searched sooner.
2859 You can use the string @samp{$cwd} to refer to whatever is the current
2860 working directory at the time @value{GDBN} searches the path. If you
2861 use @samp{.} instead, it refers to the directory where you executed the
2862 @code{path} command. @value{GDBN} replaces @samp{.} in the
2863 @var{directory} argument (with the current path) before adding
2864 @var{directory} to the search path.
2865 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2866 @c document that, since repeating it would be a no-op.
2870 Display the list of search paths for executables (the @env{PATH}
2871 environment variable).
2873 @kindex show environment
2874 @item show environment @r{[}@var{varname}@r{]}
2875 Print the value of environment variable @var{varname} to be given to
2876 your program when it starts. If you do not supply @var{varname},
2877 print the names and values of all environment variables to be given to
2878 your program. You can abbreviate @code{environment} as @code{env}.
2880 @kindex set environment
2881 @anchor{set environment}
2882 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2883 Set environment variable @var{varname} to @var{value}. The value
2884 changes for your program (and the shell @value{GDBN} uses to launch
2885 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2886 values of environment variables are just strings, and any
2887 interpretation is supplied by your program itself. The @var{value}
2888 parameter is optional; if it is eliminated, the variable is set to a
2890 @c "any string" here does not include leading, trailing
2891 @c blanks. Gnu asks: does anyone care?
2893 For example, this command:
2900 tells the debugged program, when subsequently run, that its user is named
2901 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2902 are not actually required.)
2904 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2905 which also inherits the environment set with @code{set environment}.
2906 If necessary, you can avoid that by using the @samp{env} program as a
2907 wrapper instead of using @code{set environment}. @xref{set
2908 exec-wrapper}, for an example doing just that.
2910 Environment variables that are set by the user are also transmitted to
2911 @command{gdbserver} to be used when starting the remote inferior.
2912 @pxref{QEnvironmentHexEncoded}.
2914 @kindex unset environment
2915 @anchor{unset environment}
2916 @item unset environment @var{varname}
2917 Remove variable @var{varname} from the environment to be passed to your
2918 program. This is different from @samp{set env @var{varname} =};
2919 @code{unset environment} removes the variable from the environment,
2920 rather than assigning it an empty value.
2922 Environment variables that are unset by the user are also unset on
2923 @command{gdbserver} when starting the remote inferior.
2924 @pxref{QEnvironmentUnset}.
2927 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2928 the shell indicated by your @env{SHELL} environment variable if it
2929 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2930 names a shell that runs an initialization file when started
2931 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2932 for the Z shell, or the file specified in the @env{BASH_ENV}
2933 environment variable for BASH---any variables you set in that file
2934 affect your program. You may wish to move setting of environment
2935 variables to files that are only run when you sign on, such as
2936 @file{.login} or @file{.profile}.
2938 @node Working Directory
2939 @section Your Program's Working Directory
2941 @cindex working directory (of your program)
2942 Each time you start your program with @code{run}, the inferior will be
2943 initialized with the current working directory specified by the
2944 @kbd{set cwd} command. If no directory has been specified by this
2945 command, then the inferior will inherit @value{GDBN}'s current working
2946 directory as its working directory if native debugging, or it will
2947 inherit the remote server's current working directory if remote
2952 @cindex change inferior's working directory
2953 @anchor{set cwd command}
2954 @item set cwd @r{[}@var{directory}@r{]}
2955 Set the inferior's working directory to @var{directory}, which will be
2956 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2957 argument has been specified, the command clears the setting and resets
2958 it to an empty state. This setting has no effect on @value{GDBN}'s
2959 working directory, and it only takes effect the next time you start
2960 the inferior. The @file{~} in @var{directory} is a short for the
2961 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2962 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2963 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2966 You can also change @value{GDBN}'s current working directory by using
2967 the @code{cd} command.
2971 @cindex show inferior's working directory
2973 Show the inferior's working directory. If no directory has been
2974 specified by @kbd{set cwd}, then the default inferior's working
2975 directory is the same as @value{GDBN}'s working directory.
2978 @cindex change @value{GDBN}'s working directory
2980 @item cd @r{[}@var{directory}@r{]}
2981 Set the @value{GDBN} working directory to @var{directory}. If not
2982 given, @var{directory} uses @file{'~'}.
2984 The @value{GDBN} working directory serves as a default for the
2985 commands that specify files for @value{GDBN} to operate on.
2986 @xref{Files, ,Commands to Specify Files}.
2987 @xref{set cwd command}.
2991 Print the @value{GDBN} working directory.
2994 It is generally impossible to find the current working directory of
2995 the process being debugged (since a program can change its directory
2996 during its run). If you work on a system where @value{GDBN} supports
2997 the @code{info proc} command (@pxref{Process Information}), you can
2998 use the @code{info proc} command to find out the
2999 current working directory of the debuggee.
3002 @section Your Program's Input and Output
3007 By default, the program you run under @value{GDBN} does input and output to
3008 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
3009 to its own terminal modes to interact with you, but it records the terminal
3010 modes your program was using and switches back to them when you continue
3011 running your program.
3014 @kindex info terminal
3016 Displays information recorded by @value{GDBN} about the terminal modes your
3020 You can redirect your program's input and/or output using shell
3021 redirection with the @code{run} command. For example,
3028 starts your program, diverting its output to the file @file{outfile}.
3031 @cindex controlling terminal
3032 Another way to specify where your program should do input and output is
3033 with the @code{tty} command. This command accepts a file name as
3034 argument, and causes this file to be the default for future @code{run}
3035 commands. It also resets the controlling terminal for the child
3036 process, for future @code{run} commands. For example,
3043 directs that processes started with subsequent @code{run} commands
3044 default to do input and output on the terminal @file{/dev/ttyb} and have
3045 that as their controlling terminal.
3047 An explicit redirection in @code{run} overrides the @code{tty} command's
3048 effect on the input/output device, but not its effect on the controlling
3051 When you use the @code{tty} command or redirect input in the @code{run}
3052 command, only the input @emph{for your program} is affected. The input
3053 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3054 for @code{set inferior-tty}.
3056 @cindex inferior tty
3057 @cindex set inferior controlling terminal
3058 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3059 display the name of the terminal that will be used for future runs of your
3063 @item set inferior-tty [ @var{tty} ]
3064 @kindex set inferior-tty
3065 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3066 restores the default behavior, which is to use the same terminal as
3069 @item show inferior-tty
3070 @kindex show inferior-tty
3071 Show the current tty for the program being debugged.
3075 @section Debugging an Already-running Process
3080 @item attach @var{process-id}
3081 This command attaches to a running process---one that was started
3082 outside @value{GDBN}. (@code{info files} shows your active
3083 targets.) The command takes as argument a process ID. The usual way to
3084 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3085 or with the @samp{jobs -l} shell command.
3087 @code{attach} does not repeat if you press @key{RET} a second time after
3088 executing the command.
3091 To use @code{attach}, your program must be running in an environment
3092 which supports processes; for example, @code{attach} does not work for
3093 programs on bare-board targets that lack an operating system. You must
3094 also have permission to send the process a signal.
3096 When you use @code{attach}, the debugger finds the program running in
3097 the process first by looking in the current working directory, then (if
3098 the program is not found) by using the source file search path
3099 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3100 the @code{file} command to load the program. @xref{Files, ,Commands to
3103 @anchor{set exec-file-mismatch}
3104 If the debugger can determine that the executable file running in the
3105 process it is attaching to does not match the current exec-file loaded
3106 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3107 handle the mismatch. @value{GDBN} tries to compare the files by
3108 comparing their build IDs (@pxref{build ID}), if available.
3111 @kindex exec-file-mismatch
3112 @cindex set exec-file-mismatch
3113 @item set exec-file-mismatch @samp{ask|warn|off}
3115 Whether to detect mismatch between the current executable file loaded
3116 by @value{GDBN} and the executable file used to start the process. If
3117 @samp{ask}, the default, display a warning and ask the user whether to
3118 load the process executable file; if @samp{warn}, just display a
3119 warning; if @samp{off}, don't attempt to detect a mismatch.
3120 If the user confirms loading the process executable file, then its symbols
3121 will be loaded as well.
3123 @cindex show exec-file-mismatch
3124 @item show exec-file-mismatch
3125 Show the current value of @code{exec-file-mismatch}.
3129 The first thing @value{GDBN} does after arranging to debug the specified
3130 process is to stop it. You can examine and modify an attached process
3131 with all the @value{GDBN} commands that are ordinarily available when
3132 you start processes with @code{run}. You can insert breakpoints; you
3133 can step and continue; you can modify storage. If you would rather the
3134 process continue running, you may use the @code{continue} command after
3135 attaching @value{GDBN} to the process.
3140 When you have finished debugging the attached process, you can use the
3141 @code{detach} command to release it from @value{GDBN} control. Detaching
3142 the process continues its execution. After the @code{detach} command,
3143 that process and @value{GDBN} become completely independent once more, and you
3144 are ready to @code{attach} another process or start one with @code{run}.
3145 @code{detach} does not repeat if you press @key{RET} again after
3146 executing the command.
3149 If you exit @value{GDBN} while you have an attached process, you detach
3150 that process. If you use the @code{run} command, you kill that process.
3151 By default, @value{GDBN} asks for confirmation if you try to do either of these
3152 things; you can control whether or not you need to confirm by using the
3153 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3157 @section Killing the Child Process
3162 Kill the child process in which your program is running under @value{GDBN}.
3165 This command is useful if you wish to debug a core dump instead of a
3166 running process. @value{GDBN} ignores any core dump file while your program
3169 On some operating systems, a program cannot be executed outside @value{GDBN}
3170 while you have breakpoints set on it inside @value{GDBN}. You can use the
3171 @code{kill} command in this situation to permit running your program
3172 outside the debugger.
3174 The @code{kill} command is also useful if you wish to recompile and
3175 relink your program, since on many systems it is impossible to modify an
3176 executable file while it is running in a process. In this case, when you
3177 next type @code{run}, @value{GDBN} notices that the file has changed, and
3178 reads the symbol table again (while trying to preserve your current
3179 breakpoint settings).
3181 @node Inferiors Connections and Programs
3182 @section Debugging Multiple Inferiors Connections and Programs
3184 @value{GDBN} lets you run and debug multiple programs in a single
3185 session. In addition, @value{GDBN} on some systems may let you run
3186 several programs simultaneously (otherwise you have to exit from one
3187 before starting another). On some systems @value{GDBN} may even let
3188 you debug several programs simultaneously on different remote systems.
3189 In the most general case, you can have multiple threads of execution
3190 in each of multiple processes, launched from multiple executables,
3191 running on different machines.
3194 @value{GDBN} represents the state of each program execution with an
3195 object called an @dfn{inferior}. An inferior typically corresponds to
3196 a process, but is more general and applies also to targets that do not
3197 have processes. Inferiors may be created before a process runs, and
3198 may be retained after a process exits. Inferiors have unique
3199 identifiers that are different from process ids. Usually each
3200 inferior will also have its own distinct address space, although some
3201 embedded targets may have several inferiors running in different parts
3202 of a single address space. Each inferior may in turn have multiple
3203 threads running in it.
3205 To find out what inferiors exist at any moment, use @w{@code{info
3209 @kindex info inferiors [ @var{id}@dots{} ]
3210 @item info inferiors
3211 Print a list of all inferiors currently being managed by @value{GDBN}.
3212 By default all inferiors are printed, but the argument @var{id}@dots{}
3213 -- a space separated list of inferior numbers -- can be used to limit
3214 the display to just the requested inferiors.
3216 @value{GDBN} displays for each inferior (in this order):
3220 the inferior number assigned by @value{GDBN}
3223 the target system's inferior identifier
3226 the target connection the inferior is bound to, including the unique
3227 connection number assigned by @value{GDBN}, and the protocol used by
3231 the name of the executable the inferior is running.
3236 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3237 indicates the current inferior.
3241 @c end table here to get a little more width for example
3244 (@value{GDBP}) info inferiors
3245 Num Description Connection Executable
3246 * 1 process 3401 1 (native) goodbye
3247 2 process 2307 2 (extended-remote host:10000) hello
3250 To get informations about the current inferior, use @code{inferior}:
3255 Shows information about the current inferior.
3259 @c end table here to get a little more width for example
3262 (@value{GDBP}) inferior
3263 [Current inferior is 1 [process 3401] (helloworld)]
3266 To find out what open target connections exist at any moment, use
3267 @w{@code{info connections}}:
3270 @kindex info connections [ @var{id}@dots{} ]
3271 @item info connections
3272 Print a list of all open target connections currently being managed by
3273 @value{GDBN}. By default all connections are printed, but the
3274 argument @var{id}@dots{} -- a space separated list of connections
3275 numbers -- can be used to limit the display to just the requested
3278 @value{GDBN} displays for each connection (in this order):
3282 the connection number assigned by @value{GDBN}.
3285 the protocol used by the connection.
3288 a textual description of the protocol used by the connection.
3293 An asterisk @samp{*} preceding the connection number indicates the
3294 connection of the current inferior.
3298 @c end table here to get a little more width for example
3301 (@value{GDBP}) info connections
3302 Num What Description
3303 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3304 2 native Native process
3305 3 core Local core dump file
3308 To switch focus between inferiors, use the @code{inferior} command:
3311 @kindex inferior @var{infno}
3312 @item inferior @var{infno}
3313 Make inferior number @var{infno} the current inferior. The argument
3314 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3315 in the first field of the @samp{info inferiors} display.
3318 @vindex $_inferior@r{, convenience variable}
3319 The debugger convenience variable @samp{$_inferior} contains the
3320 number of the current inferior. You may find this useful in writing
3321 breakpoint conditional expressions, command scripts, and so forth.
3322 @xref{Convenience Vars,, Convenience Variables}, for general
3323 information on convenience variables.
3325 You can get multiple executables into a debugging session via the
3326 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3327 systems @value{GDBN} can add inferiors to the debug session
3328 automatically by following calls to @code{fork} and @code{exec}. To
3329 remove inferiors from the debugging session use the
3330 @w{@code{remove-inferiors}} command.
3333 @anchor{add_inferior_cli}
3334 @kindex add-inferior
3335 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3336 Adds @var{n} inferiors to be run using @var{executable} as the
3337 executable; @var{n} defaults to 1. If no executable is specified,
3338 the inferiors begins empty, with no program. You can still assign or
3339 change the program assigned to the inferior at any time by using the
3340 @code{file} command with the executable name as its argument.
3342 By default, the new inferior begins connected to the same target
3343 connection as the current inferior. For example, if the current
3344 inferior was connected to @code{gdbserver} with @code{target remote},
3345 then the new inferior will be connected to the same @code{gdbserver}
3346 instance. The @samp{-no-connection} option starts the new inferior
3347 with no connection yet. You can then for example use the @code{target
3348 remote} command to connect to some other @code{gdbserver} instance,
3349 use @code{run} to spawn a local program, etc.
3351 @kindex clone-inferior
3352 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3353 Adds @var{n} inferiors ready to execute the same program as inferior
3354 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3355 number of the current inferior. This command copies the values of the
3356 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3357 current inferior to the new one. It also propagates changes the user
3358 made to environment variables using the @w{@code{set environment}} and
3359 @w{@code{unset environment}} commands. This is a convenient command
3360 when you want to run another instance of the inferior you are debugging.
3363 (@value{GDBP}) info inferiors
3364 Num Description Connection Executable
3365 * 1 process 29964 1 (native) helloworld
3366 (@value{GDBP}) clone-inferior
3369 (@value{GDBP}) info inferiors
3370 Num Description Connection Executable
3371 * 1 process 29964 1 (native) helloworld
3372 2 <null> 1 (native) helloworld
3375 You can now simply switch focus to inferior 2 and run it.
3377 @kindex remove-inferiors
3378 @item remove-inferiors @var{infno}@dots{}
3379 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3380 possible to remove an inferior that is running with this command. For
3381 those, use the @code{kill} or @code{detach} command first.
3385 To quit debugging one of the running inferiors that is not the current
3386 inferior, you can either detach from it by using the @w{@code{detach
3387 inferior}} command (allowing it to run independently), or kill it
3388 using the @w{@code{kill inferiors}} command:
3391 @kindex detach inferiors @var{infno}@dots{}
3392 @item detach inferior @var{infno}@dots{}
3393 Detach from the inferior or inferiors identified by @value{GDBN}
3394 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3395 still stays on the list of inferiors shown by @code{info inferiors},
3396 but its Description will show @samp{<null>}.
3398 @kindex kill inferiors @var{infno}@dots{}
3399 @item kill inferiors @var{infno}@dots{}
3400 Kill the inferior or inferiors identified by @value{GDBN} inferior
3401 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3402 stays on the list of inferiors shown by @code{info inferiors}, but its
3403 Description will show @samp{<null>}.
3406 After the successful completion of a command such as @code{detach},
3407 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3408 a normal process exit, the inferior is still valid and listed with
3409 @code{info inferiors}, ready to be restarted.
3412 To be notified when inferiors are started or exit under @value{GDBN}'s
3413 control use @w{@code{set print inferior-events}}:
3416 @kindex set print inferior-events
3417 @cindex print messages on inferior start and exit
3418 @item set print inferior-events
3419 @itemx set print inferior-events on
3420 @itemx set print inferior-events off
3421 The @code{set print inferior-events} command allows you to enable or
3422 disable printing of messages when @value{GDBN} notices that new
3423 inferiors have started or that inferiors have exited or have been
3424 detached. By default, these messages will be printed.
3426 @kindex show print inferior-events
3427 @item show print inferior-events
3428 Show whether messages will be printed when @value{GDBN} detects that
3429 inferiors have started, exited or have been detached.
3432 Many commands will work the same with multiple programs as with a
3433 single program: e.g., @code{print myglobal} will simply display the
3434 value of @code{myglobal} in the current inferior.
3437 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3438 get more info about the relationship of inferiors, programs, address
3439 spaces in a debug session. You can do that with the @w{@code{maint
3440 info program-spaces}} command.
3443 @kindex maint info program-spaces
3444 @item maint info program-spaces
3445 Print a list of all program spaces currently being managed by
3448 @value{GDBN} displays for each program space (in this order):
3452 the program space number assigned by @value{GDBN}
3455 the name of the executable loaded into the program space, with e.g.,
3456 the @code{file} command.
3461 An asterisk @samp{*} preceding the @value{GDBN} program space number
3462 indicates the current program space.
3464 In addition, below each program space line, @value{GDBN} prints extra
3465 information that isn't suitable to display in tabular form. For
3466 example, the list of inferiors bound to the program space.
3469 (@value{GDBP}) maint info program-spaces
3473 Bound inferiors: ID 1 (process 21561)
3476 Here we can see that no inferior is running the program @code{hello},
3477 while @code{process 21561} is running the program @code{goodbye}. On
3478 some targets, it is possible that multiple inferiors are bound to the
3479 same program space. The most common example is that of debugging both
3480 the parent and child processes of a @code{vfork} call. For example,
3483 (@value{GDBP}) maint info program-spaces
3486 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3489 Here, both inferior 2 and inferior 1 are running in the same program
3490 space as a result of inferior 1 having executed a @code{vfork} call.
3494 @section Debugging Programs with Multiple Threads
3496 @cindex threads of execution
3497 @cindex multiple threads
3498 @cindex switching threads
3499 In some operating systems, such as GNU/Linux and Solaris, a single program
3500 may have more than one @dfn{thread} of execution. The precise semantics
3501 of threads differ from one operating system to another, but in general
3502 the threads of a single program are akin to multiple processes---except
3503 that they share one address space (that is, they can all examine and
3504 modify the same variables). On the other hand, each thread has its own
3505 registers and execution stack, and perhaps private memory.
3507 @value{GDBN} provides these facilities for debugging multi-thread
3511 @item automatic notification of new threads
3512 @item @samp{thread @var{thread-id}}, a command to switch among threads
3513 @item @samp{info threads}, a command to inquire about existing threads
3514 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3515 a command to apply a command to a list of threads
3516 @item thread-specific breakpoints
3517 @item @samp{set print thread-events}, which controls printing of
3518 messages on thread start and exit.
3519 @item @samp{set libthread-db-search-path @var{path}}, which lets
3520 the user specify which @code{libthread_db} to use if the default choice
3521 isn't compatible with the program.
3524 @cindex focus of debugging
3525 @cindex current thread
3526 The @value{GDBN} thread debugging facility allows you to observe all
3527 threads while your program runs---but whenever @value{GDBN} takes
3528 control, one thread in particular is always the focus of debugging.
3529 This thread is called the @dfn{current thread}. Debugging commands show
3530 program information from the perspective of the current thread.
3532 @cindex @code{New} @var{systag} message
3533 @cindex thread identifier (system)
3534 @c FIXME-implementors!! It would be more helpful if the [New...] message
3535 @c included GDB's numeric thread handle, so you could just go to that
3536 @c thread without first checking `info threads'.
3537 Whenever @value{GDBN} detects a new thread in your program, it displays
3538 the target system's identification for the thread with a message in the
3539 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3540 whose form varies depending on the particular system. For example, on
3541 @sc{gnu}/Linux, you might see
3544 [New Thread 0x41e02940 (LWP 25582)]
3548 when @value{GDBN} notices a new thread. In contrast, on other systems,
3549 the @var{systag} is simply something like @samp{process 368}, with no
3552 @c FIXME!! (1) Does the [New...] message appear even for the very first
3553 @c thread of a program, or does it only appear for the
3554 @c second---i.e.@: when it becomes obvious we have a multithread
3556 @c (2) *Is* there necessarily a first thread always? Or do some
3557 @c multithread systems permit starting a program with multiple
3558 @c threads ab initio?
3560 @anchor{thread numbers}
3561 @cindex thread number, per inferior
3562 @cindex thread identifier (GDB)
3563 For debugging purposes, @value{GDBN} associates its own thread number
3564 ---always a single integer---with each thread of an inferior. This
3565 number is unique between all threads of an inferior, but not unique
3566 between threads of different inferiors.
3568 @cindex qualified thread ID
3569 You can refer to a given thread in an inferior using the qualified
3570 @var{inferior-num}.@var{thread-num} syntax, also known as
3571 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3572 number and @var{thread-num} being the thread number of the given
3573 inferior. For example, thread @code{2.3} refers to thread number 3 of
3574 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3575 then @value{GDBN} infers you're referring to a thread of the current
3578 Until you create a second inferior, @value{GDBN} does not show the
3579 @var{inferior-num} part of thread IDs, even though you can always use
3580 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3581 of inferior 1, the initial inferior.
3583 @anchor{thread ID lists}
3584 @cindex thread ID lists
3585 Some commands accept a space-separated @dfn{thread ID list} as
3586 argument. A list element can be:
3590 A thread ID as shown in the first field of the @samp{info threads}
3591 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3595 A range of thread numbers, again with or without an inferior
3596 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3597 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3600 All threads of an inferior, specified with a star wildcard, with or
3601 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3602 @samp{1.*}) or @code{*}. The former refers to all threads of the
3603 given inferior, and the latter form without an inferior qualifier
3604 refers to all threads of the current inferior.
3608 For example, if the current inferior is 1, and inferior 7 has one
3609 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3610 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3611 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3612 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3616 @anchor{global thread numbers}
3617 @cindex global thread number
3618 @cindex global thread identifier (GDB)
3619 In addition to a @emph{per-inferior} number, each thread is also
3620 assigned a unique @emph{global} number, also known as @dfn{global
3621 thread ID}, a single integer. Unlike the thread number component of
3622 the thread ID, no two threads have the same global ID, even when
3623 you're debugging multiple inferiors.
3625 From @value{GDBN}'s perspective, a process always has at least one
3626 thread. In other words, @value{GDBN} assigns a thread number to the
3627 program's ``main thread'' even if the program is not multi-threaded.
3629 @vindex $_thread@r{, convenience variable}
3630 @vindex $_gthread@r{, convenience variable}
3631 The debugger convenience variables @samp{$_thread} and
3632 @samp{$_gthread} contain, respectively, the per-inferior thread number
3633 and the global thread number of the current thread. You may find this
3634 useful in writing breakpoint conditional expressions, command scripts,
3635 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3636 general information on convenience variables.
3638 If @value{GDBN} detects the program is multi-threaded, it augments the
3639 usual message about stopping at a breakpoint with the ID and name of
3640 the thread that hit the breakpoint.
3643 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3646 Likewise when the program receives a signal:
3649 Thread 1 "main" received signal SIGINT, Interrupt.
3653 @anchor{info_threads}
3654 @kindex info threads
3655 @item info threads @r{[}@var{thread-id-list}@r{]}
3657 Display information about one or more threads. With no arguments
3658 displays information about all threads. You can specify the list of
3659 threads that you want to display using the thread ID list syntax
3660 (@pxref{thread ID lists}).
3662 @value{GDBN} displays for each thread (in this order):
3666 the per-inferior thread number assigned by @value{GDBN}
3669 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3670 option was specified
3673 the target system's thread identifier (@var{systag})
3676 the thread's name, if one is known. A thread can either be named by
3677 the user (see @code{thread name}, below), or, in some cases, by the
3681 the current stack frame summary for that thread
3685 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3686 indicates the current thread.
3690 @c end table here to get a little more width for example
3693 (@value{GDBP}) info threads
3695 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3696 2 process 35 thread 23 0x34e5 in sigpause ()
3697 3 process 35 thread 27 0x34e5 in sigpause ()
3701 If you're debugging multiple inferiors, @value{GDBN} displays thread
3702 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3703 Otherwise, only @var{thread-num} is shown.
3705 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3706 indicating each thread's global thread ID:
3709 (@value{GDBP}) info threads
3710 Id GId Target Id Frame
3711 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3712 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3713 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3714 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3717 On Solaris, you can display more information about user threads with a
3718 Solaris-specific command:
3721 @item maint info sol-threads
3722 @kindex maint info sol-threads
3723 @cindex thread info (Solaris)
3724 Display info on Solaris user threads.
3728 @kindex thread @var{thread-id}
3729 @item thread @var{thread-id}
3730 Make thread ID @var{thread-id} the current thread. The command
3731 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3732 the first field of the @samp{info threads} display, with or without an
3733 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3735 @value{GDBN} responds by displaying the system identifier of the
3736 thread you selected, and its current stack frame summary:
3739 (@value{GDBP}) thread 2
3740 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3741 #0 some_function (ignore=0x0) at example.c:8
3742 8 printf ("hello\n");
3746 As with the @samp{[New @dots{}]} message, the form of the text after
3747 @samp{Switching to} depends on your system's conventions for identifying
3750 @anchor{thread apply all}
3751 @kindex thread apply
3752 @cindex apply command to several threads
3753 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3754 The @code{thread apply} command allows you to apply the named
3755 @var{command} to one or more threads. Specify the threads that you
3756 want affected using the thread ID list syntax (@pxref{thread ID
3757 lists}), or specify @code{all} to apply to all threads. To apply a
3758 command to all threads in descending order, type @kbd{thread apply all
3759 @var{command}}. To apply a command to all threads in ascending order,
3760 type @kbd{thread apply all -ascending @var{command}}.
3762 The @var{flag} arguments control what output to produce and how to handle
3763 errors raised when applying @var{command} to a thread. @var{flag}
3764 must start with a @code{-} directly followed by one letter in
3765 @code{qcs}. If several flags are provided, they must be given
3766 individually, such as @code{-c -q}.
3768 By default, @value{GDBN} displays some thread information before the
3769 output produced by @var{command}, and an error raised during the
3770 execution of a @var{command} will abort @code{thread apply}. The
3771 following flags can be used to fine-tune this behavior:
3775 The flag @code{-c}, which stands for @samp{continue}, causes any
3776 errors in @var{command} to be displayed, and the execution of
3777 @code{thread apply} then continues.
3779 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3780 or empty output produced by a @var{command} to be silently ignored.
3781 That is, the execution continues, but the thread information and errors
3784 The flag @code{-q} (@samp{quiet}) disables printing the thread
3788 Flags @code{-c} and @code{-s} cannot be used together.
3791 @cindex apply command to all threads (ignoring errors and empty output)
3792 @item taas [@var{option}]@dots{} @var{command}
3793 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3794 Applies @var{command} on all threads, ignoring errors and empty output.
3796 The @code{taas} command accepts the same options as the @code{thread
3797 apply all} command. @xref{thread apply all}.
3800 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3801 @item tfaas [@var{option}]@dots{} @var{command}
3802 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3803 Applies @var{command} on all frames of all threads, ignoring errors
3804 and empty output. Note that the flag @code{-s} is specified twice:
3805 The first @code{-s} ensures that @code{thread apply} only shows the thread
3806 information of the threads for which @code{frame apply} produces
3807 some output. The second @code{-s} is needed to ensure that @code{frame
3808 apply} shows the frame information of a frame only if the
3809 @var{command} successfully produced some output.
3811 It can for example be used to print a local variable or a function
3812 argument without knowing the thread or frame where this variable or argument
3815 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3818 The @code{tfaas} command accepts the same options as the @code{frame
3819 apply} command. @xref{Frame Apply,,frame apply}.
3822 @cindex name a thread
3823 @item thread name [@var{name}]
3824 This command assigns a name to the current thread. If no argument is
3825 given, any existing user-specified name is removed. The thread name
3826 appears in the @samp{info threads} display.
3828 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3829 determine the name of the thread as given by the OS. On these
3830 systems, a name specified with @samp{thread name} will override the
3831 system-give name, and removing the user-specified name will cause
3832 @value{GDBN} to once again display the system-specified name.
3835 @cindex search for a thread
3836 @item thread find [@var{regexp}]
3837 Search for and display thread ids whose name or @var{systag}
3838 matches the supplied regular expression.
3840 As well as being the complement to the @samp{thread name} command,
3841 this command also allows you to identify a thread by its target
3842 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3846 (@value{GDBN}) thread find 26688
3847 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3848 (@value{GDBN}) info thread 4
3850 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3853 @kindex set print thread-events
3854 @cindex print messages on thread start and exit
3855 @item set print thread-events
3856 @itemx set print thread-events on
3857 @itemx set print thread-events off
3858 The @code{set print thread-events} command allows you to enable or
3859 disable printing of messages when @value{GDBN} notices that new threads have
3860 started or that threads have exited. By default, these messages will
3861 be printed if detection of these events is supported by the target.
3862 Note that these messages cannot be disabled on all targets.
3864 @kindex show print thread-events
3865 @item show print thread-events
3866 Show whether messages will be printed when @value{GDBN} detects that threads
3867 have started and exited.
3870 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3871 more information about how @value{GDBN} behaves when you stop and start
3872 programs with multiple threads.
3874 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3875 watchpoints in programs with multiple threads.
3877 @anchor{set libthread-db-search-path}
3879 @kindex set libthread-db-search-path
3880 @cindex search path for @code{libthread_db}
3881 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3882 If this variable is set, @var{path} is a colon-separated list of
3883 directories @value{GDBN} will use to search for @code{libthread_db}.
3884 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3885 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3886 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3889 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3890 @code{libthread_db} library to obtain information about threads in the
3891 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3892 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3893 specific thread debugging library loading is enabled
3894 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3896 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3897 refers to the default system directories that are
3898 normally searched for loading shared libraries. The @samp{$sdir} entry
3899 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3900 (@pxref{libthread_db.so.1 file}).
3902 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3903 refers to the directory from which @code{libpthread}
3904 was loaded in the inferior process.
3906 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3907 @value{GDBN} attempts to initialize it with the current inferior process.
3908 If this initialization fails (which could happen because of a version
3909 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3910 will unload @code{libthread_db}, and continue with the next directory.
3911 If none of @code{libthread_db} libraries initialize successfully,
3912 @value{GDBN} will issue a warning and thread debugging will be disabled.
3914 Setting @code{libthread-db-search-path} is currently implemented
3915 only on some platforms.
3917 @kindex show libthread-db-search-path
3918 @item show libthread-db-search-path
3919 Display current libthread_db search path.
3921 @kindex set debug libthread-db
3922 @kindex show debug libthread-db
3923 @cindex debugging @code{libthread_db}
3924 @item set debug libthread-db
3925 @itemx show debug libthread-db
3926 Turns on or off display of @code{libthread_db}-related events.
3927 Use @code{1} to enable, @code{0} to disable.
3929 @kindex set debug threads
3930 @kindex show debug threads
3931 @cindex debugging @code{threads}
3932 @item set debug threads @r{[}on@r{|}off@r{]}
3933 @itemx show debug threads
3934 When @samp{on} @value{GDBN} will print additional messages when
3935 threads are created and deleted.
3939 @section Debugging Forks
3941 @cindex fork, debugging programs which call
3942 @cindex multiple processes
3943 @cindex processes, multiple
3944 On most systems, @value{GDBN} has no special support for debugging
3945 programs which create additional processes using the @code{fork}
3946 function. When a program forks, @value{GDBN} will continue to debug the
3947 parent process and the child process will run unimpeded. If you have
3948 set a breakpoint in any code which the child then executes, the child
3949 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3950 will cause it to terminate.
3952 However, if you want to debug the child process there is a workaround
3953 which isn't too painful. Put a call to @code{sleep} in the code which
3954 the child process executes after the fork. It may be useful to sleep
3955 only if a certain environment variable is set, or a certain file exists,
3956 so that the delay need not occur when you don't want to run @value{GDBN}
3957 on the child. While the child is sleeping, use the @code{ps} program to
3958 get its process ID. Then tell @value{GDBN} (a new invocation of
3959 @value{GDBN} if you are also debugging the parent process) to attach to
3960 the child process (@pxref{Attach}). From that point on you can debug
3961 the child process just like any other process which you attached to.
3963 On some systems, @value{GDBN} provides support for debugging programs
3964 that create additional processes using the @code{fork} or @code{vfork}
3965 functions. On @sc{gnu}/Linux platforms, this feature is supported
3966 with kernel version 2.5.46 and later.
3968 The fork debugging commands are supported in native mode and when
3969 connected to @code{gdbserver} in either @code{target remote} mode or
3970 @code{target extended-remote} mode.
3972 By default, when a program forks, @value{GDBN} will continue to debug
3973 the parent process and the child process will run unimpeded.
3975 If you want to follow the child process instead of the parent process,
3976 use the command @w{@code{set follow-fork-mode}}.
3979 @kindex set follow-fork-mode
3980 @item set follow-fork-mode @var{mode}
3981 Set the debugger response to a program call of @code{fork} or
3982 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3983 process. The @var{mode} argument can be:
3987 The original process is debugged after a fork. The child process runs
3988 unimpeded. This is the default.
3991 The new process is debugged after a fork. The parent process runs
3996 @kindex show follow-fork-mode
3997 @item show follow-fork-mode
3998 Display the current debugger response to a @code{fork} or @code{vfork} call.
4001 @cindex debugging multiple processes
4002 On Linux, if you want to debug both the parent and child processes, use the
4003 command @w{@code{set detach-on-fork}}.
4006 @kindex set detach-on-fork
4007 @item set detach-on-fork @var{mode}
4008 Tells gdb whether to detach one of the processes after a fork, or
4009 retain debugger control over them both.
4013 The child process (or parent process, depending on the value of
4014 @code{follow-fork-mode}) will be detached and allowed to run
4015 independently. This is the default.
4018 Both processes will be held under the control of @value{GDBN}.
4019 One process (child or parent, depending on the value of
4020 @code{follow-fork-mode}) is debugged as usual, while the other
4025 @kindex show detach-on-fork
4026 @item show detach-on-fork
4027 Show whether detach-on-fork mode is on/off.
4030 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4031 will retain control of all forked processes (including nested forks).
4032 You can list the forked processes under the control of @value{GDBN} by
4033 using the @w{@code{info inferiors}} command, and switch from one fork
4034 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4035 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4037 To quit debugging one of the forked processes, you can either detach
4038 from it by using the @w{@code{detach inferiors}} command (allowing it
4039 to run independently), or kill it using the @w{@code{kill inferiors}}
4040 command. @xref{Inferiors Connections and Programs, ,Debugging
4041 Multiple Inferiors Connections and Programs}.
4043 If you ask to debug a child process and a @code{vfork} is followed by an
4044 @code{exec}, @value{GDBN} executes the new target up to the first
4045 breakpoint in the new target. If you have a breakpoint set on
4046 @code{main} in your original program, the breakpoint will also be set on
4047 the child process's @code{main}.
4049 On some systems, when a child process is spawned by @code{vfork}, you
4050 cannot debug the child or parent until an @code{exec} call completes.
4052 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4053 call executes, the new target restarts. To restart the parent
4054 process, use the @code{file} command with the parent executable name
4055 as its argument. By default, after an @code{exec} call executes,
4056 @value{GDBN} discards the symbols of the previous executable image.
4057 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4061 @kindex set follow-exec-mode
4062 @item set follow-exec-mode @var{mode}
4064 Set debugger response to a program call of @code{exec}. An
4065 @code{exec} call replaces the program image of a process.
4067 @code{follow-exec-mode} can be:
4071 @value{GDBN} creates a new inferior and rebinds the process to this
4072 new inferior. The program the process was running before the
4073 @code{exec} call can be restarted afterwards by restarting the
4079 (@value{GDBP}) info inferiors
4081 Id Description Executable
4084 process 12020 is executing new program: prog2
4085 Program exited normally.
4086 (@value{GDBP}) info inferiors
4087 Id Description Executable
4093 @value{GDBN} keeps the process bound to the same inferior. The new
4094 executable image replaces the previous executable loaded in the
4095 inferior. Restarting the inferior after the @code{exec} call, with
4096 e.g., the @code{run} command, restarts the executable the process was
4097 running after the @code{exec} call. This is the default mode.
4102 (@value{GDBP}) info inferiors
4103 Id Description Executable
4106 process 12020 is executing new program: prog2
4107 Program exited normally.
4108 (@value{GDBP}) info inferiors
4109 Id Description Executable
4116 @code{follow-exec-mode} is supported in native mode and
4117 @code{target extended-remote} mode.
4119 You can use the @code{catch} command to make @value{GDBN} stop whenever
4120 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4121 Catchpoints, ,Setting Catchpoints}.
4123 @node Checkpoint/Restart
4124 @section Setting a @emph{Bookmark} to Return to Later
4129 @cindex snapshot of a process
4130 @cindex rewind program state
4132 On certain operating systems@footnote{Currently, only
4133 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4134 program's state, called a @dfn{checkpoint}, and come back to it
4137 Returning to a checkpoint effectively undoes everything that has
4138 happened in the program since the @code{checkpoint} was saved. This
4139 includes changes in memory, registers, and even (within some limits)
4140 system state. Effectively, it is like going back in time to the
4141 moment when the checkpoint was saved.
4143 Thus, if you're stepping thru a program and you think you're
4144 getting close to the point where things go wrong, you can save
4145 a checkpoint. Then, if you accidentally go too far and miss
4146 the critical statement, instead of having to restart your program
4147 from the beginning, you can just go back to the checkpoint and
4148 start again from there.
4150 This can be especially useful if it takes a lot of time or
4151 steps to reach the point where you think the bug occurs.
4153 To use the @code{checkpoint}/@code{restart} method of debugging:
4158 Save a snapshot of the debugged program's current execution state.
4159 The @code{checkpoint} command takes no arguments, but each checkpoint
4160 is assigned a small integer id, similar to a breakpoint id.
4162 @kindex info checkpoints
4163 @item info checkpoints
4164 List the checkpoints that have been saved in the current debugging
4165 session. For each checkpoint, the following information will be
4172 @item Source line, or label
4175 @kindex restart @var{checkpoint-id}
4176 @item restart @var{checkpoint-id}
4177 Restore the program state that was saved as checkpoint number
4178 @var{checkpoint-id}. All program variables, registers, stack frames
4179 etc.@: will be returned to the values that they had when the checkpoint
4180 was saved. In essence, gdb will ``wind back the clock'' to the point
4181 in time when the checkpoint was saved.
4183 Note that breakpoints, @value{GDBN} variables, command history etc.
4184 are not affected by restoring a checkpoint. In general, a checkpoint
4185 only restores things that reside in the program being debugged, not in
4188 @kindex delete checkpoint @var{checkpoint-id}
4189 @item delete checkpoint @var{checkpoint-id}
4190 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4194 Returning to a previously saved checkpoint will restore the user state
4195 of the program being debugged, plus a significant subset of the system
4196 (OS) state, including file pointers. It won't ``un-write'' data from
4197 a file, but it will rewind the file pointer to the previous location,
4198 so that the previously written data can be overwritten. For files
4199 opened in read mode, the pointer will also be restored so that the
4200 previously read data can be read again.
4202 Of course, characters that have been sent to a printer (or other
4203 external device) cannot be ``snatched back'', and characters received
4204 from eg.@: a serial device can be removed from internal program buffers,
4205 but they cannot be ``pushed back'' into the serial pipeline, ready to
4206 be received again. Similarly, the actual contents of files that have
4207 been changed cannot be restored (at this time).
4209 However, within those constraints, you actually can ``rewind'' your
4210 program to a previously saved point in time, and begin debugging it
4211 again --- and you can change the course of events so as to debug a
4212 different execution path this time.
4214 @cindex checkpoints and process id
4215 Finally, there is one bit of internal program state that will be
4216 different when you return to a checkpoint --- the program's process
4217 id. Each checkpoint will have a unique process id (or @var{pid}),
4218 and each will be different from the program's original @var{pid}.
4219 If your program has saved a local copy of its process id, this could
4220 potentially pose a problem.
4222 @subsection A Non-obvious Benefit of Using Checkpoints
4224 On some systems such as @sc{gnu}/Linux, address space randomization
4225 is performed on new processes for security reasons. This makes it
4226 difficult or impossible to set a breakpoint, or watchpoint, on an
4227 absolute address if you have to restart the program, since the
4228 absolute location of a symbol will change from one execution to the
4231 A checkpoint, however, is an @emph{identical} copy of a process.
4232 Therefore if you create a checkpoint at (eg.@:) the start of main,
4233 and simply return to that checkpoint instead of restarting the
4234 process, you can avoid the effects of address randomization and
4235 your symbols will all stay in the same place.
4238 @chapter Stopping and Continuing
4240 The principal purposes of using a debugger are so that you can stop your
4241 program before it terminates; or so that, if your program runs into
4242 trouble, you can investigate and find out why.
4244 Inside @value{GDBN}, your program may stop for any of several reasons,
4245 such as a signal, a breakpoint, or reaching a new line after a
4246 @value{GDBN} command such as @code{step}. You may then examine and
4247 change variables, set new breakpoints or remove old ones, and then
4248 continue execution. Usually, the messages shown by @value{GDBN} provide
4249 ample explanation of the status of your program---but you can also
4250 explicitly request this information at any time.
4253 @kindex info program
4255 Display information about the status of your program: whether it is
4256 running or not, what process it is, and why it stopped.
4260 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4261 * Continuing and Stepping:: Resuming execution
4262 * Skipping Over Functions and Files::
4263 Skipping over functions and files
4265 * Thread Stops:: Stopping and starting multi-thread programs
4269 @section Breakpoints, Watchpoints, and Catchpoints
4272 A @dfn{breakpoint} makes your program stop whenever a certain point in
4273 the program is reached. For each breakpoint, you can add conditions to
4274 control in finer detail whether your program stops. You can set
4275 breakpoints with the @code{break} command and its variants (@pxref{Set
4276 Breaks, ,Setting Breakpoints}), to specify the place where your program
4277 should stop by line number, function name or exact address in the
4280 On some systems, you can set breakpoints in shared libraries before
4281 the executable is run.
4284 @cindex data breakpoints
4285 @cindex memory tracing
4286 @cindex breakpoint on memory address
4287 @cindex breakpoint on variable modification
4288 A @dfn{watchpoint} is a special breakpoint that stops your program
4289 when the value of an expression changes. The expression may be a value
4290 of a variable, or it could involve values of one or more variables
4291 combined by operators, such as @samp{a + b}. This is sometimes called
4292 @dfn{data breakpoints}. You must use a different command to set
4293 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4294 from that, you can manage a watchpoint like any other breakpoint: you
4295 enable, disable, and delete both breakpoints and watchpoints using the
4298 You can arrange to have values from your program displayed automatically
4299 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4303 @cindex breakpoint on events
4304 A @dfn{catchpoint} is another special breakpoint that stops your program
4305 when a certain kind of event occurs, such as the throwing of a C@t{++}
4306 exception or the loading of a library. As with watchpoints, you use a
4307 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4308 Catchpoints}), but aside from that, you can manage a catchpoint like any
4309 other breakpoint. (To stop when your program receives a signal, use the
4310 @code{handle} command; see @ref{Signals, ,Signals}.)
4312 @cindex breakpoint numbers
4313 @cindex numbers for breakpoints
4314 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4315 catchpoint when you create it; these numbers are successive integers
4316 starting with one. In many of the commands for controlling various
4317 features of breakpoints you use the breakpoint number to say which
4318 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4319 @dfn{disabled}; if disabled, it has no effect on your program until you
4322 @cindex breakpoint ranges
4323 @cindex breakpoint lists
4324 @cindex ranges of breakpoints
4325 @cindex lists of breakpoints
4326 Some @value{GDBN} commands accept a space-separated list of breakpoints
4327 on which to operate. A list element can be either a single breakpoint number,
4328 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4329 When a breakpoint list is given to a command, all breakpoints in that list
4333 * Set Breaks:: Setting breakpoints
4334 * Set Watchpoints:: Setting watchpoints
4335 * Set Catchpoints:: Setting catchpoints
4336 * Delete Breaks:: Deleting breakpoints
4337 * Disabling:: Disabling breakpoints
4338 * Conditions:: Break conditions
4339 * Break Commands:: Breakpoint command lists
4340 * Dynamic Printf:: Dynamic printf
4341 * Save Breakpoints:: How to save breakpoints in a file
4342 * Static Probe Points:: Listing static probe points
4343 * Error in Breakpoints:: ``Cannot insert breakpoints''
4344 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4348 @subsection Setting Breakpoints
4350 @c FIXME LMB what does GDB do if no code on line of breakpt?
4351 @c consider in particular declaration with/without initialization.
4353 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4356 @kindex b @r{(@code{break})}
4357 @vindex $bpnum@r{, convenience variable}
4358 @cindex latest breakpoint
4359 Breakpoints are set with the @code{break} command (abbreviated
4360 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4361 number of the breakpoint you've set most recently; see @ref{Convenience
4362 Vars,, Convenience Variables}, for a discussion of what you can do with
4363 convenience variables.
4366 @item break @var{locspec}
4367 Set a breakpoint at all the code locations in your program that result
4368 from resolving the given @var{locspec}. @var{locspec} can specify a
4369 function name, a line number, an address of an instruction, and more.
4370 @xref{Location Specifications}, for the various forms of
4371 @var{locspec}. The breakpoint will stop your program just before it
4372 executes the instruction at the address of any of the breakpoint's
4375 When using source languages that permit overloading of symbols, such
4376 as C@t{++}, a function name may refer to more than one symbol, and
4377 thus more than one place to break. @xref{Ambiguous
4378 Expressions,,Ambiguous Expressions}, for a discussion of that
4381 It is also possible to insert a breakpoint that will stop the program
4382 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4383 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4386 When called without any arguments, @code{break} sets a breakpoint at
4387 the next instruction to be executed in the selected stack frame
4388 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4389 innermost, this makes your program stop as soon as control
4390 returns to that frame. This is similar to the effect of a
4391 @code{finish} command in the frame inside the selected frame---except
4392 that @code{finish} does not leave an active breakpoint. If you use
4393 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4394 the next time it reaches the current location; this may be useful
4397 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4398 least one instruction has been executed. If it did not do this, you
4399 would be unable to proceed past a breakpoint without first disabling the
4400 breakpoint. This rule applies whether or not the breakpoint already
4401 existed when your program stopped.
4403 @item break @dots{} if @var{cond}
4404 Set a breakpoint with condition @var{cond}; evaluate the expression
4405 @var{cond} each time the breakpoint is reached, and stop only if the
4406 value is nonzero---that is, if @var{cond} evaluates as true.
4407 @samp{@dots{}} stands for one of the possible arguments described
4408 above (or no argument) specifying where to break. @xref{Conditions,
4409 ,Break Conditions}, for more information on breakpoint conditions.
4411 The breakpoint may be mapped to multiple locations. If the breakpoint
4412 condition @var{cond} is invalid at some but not all of the locations,
4413 the locations for which the condition is invalid are disabled. For
4414 example, @value{GDBN} reports below that two of the three locations
4418 (@value{GDBP}) break func if a == 10
4419 warning: failed to validate condition at location 0x11ce, disabling:
4420 No symbol "a" in current context.
4421 warning: failed to validate condition at location 0x11b6, disabling:
4422 No symbol "a" in current context.
4423 Breakpoint 1 at 0x11b6: func. (3 locations)
4426 Locations that are disabled because of the condition are denoted by an
4427 uppercase @code{N} in the output of the @code{info breakpoints}
4431 (@value{GDBP}) info breakpoints
4432 Num Type Disp Enb Address What
4433 1 breakpoint keep y <MULTIPLE>
4434 stop only if a == 10
4435 1.1 N* 0x00000000000011b6 in ...
4436 1.2 y 0x00000000000011c2 in ...
4437 1.3 N* 0x00000000000011ce in ...
4438 (*): Breakpoint condition is invalid at this location.
4441 If the breakpoint condition @var{cond} is invalid in the context of
4442 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4443 define the breakpoint. For example, if variable @code{foo} is an
4447 (@value{GDBP}) break func if foo
4448 No symbol "foo" in current context.
4451 @item break @dots{} -force-condition if @var{cond}
4452 There may be cases where the condition @var{cond} is invalid at all
4453 the current locations, but the user knows that it will be valid at a
4454 future location; for example, because of a library load. In such
4455 cases, by using the @code{-force-condition} keyword before @samp{if},
4456 @value{GDBN} can be forced to define the breakpoint with the given
4457 condition expression instead of refusing it.
4460 (@value{GDBP}) break func -force-condition if foo
4461 warning: failed to validate condition at location 1, disabling:
4462 No symbol "foo" in current context.
4463 warning: failed to validate condition at location 2, disabling:
4464 No symbol "foo" in current context.
4465 warning: failed to validate condition at location 3, disabling:
4466 No symbol "foo" in current context.
4467 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4470 This causes all the present locations where the breakpoint would
4471 otherwise be inserted, to be disabled, as seen in the example above.
4472 However, if there exist locations at which the condition is valid, the
4473 @code{-force-condition} keyword has no effect.
4476 @item tbreak @var{args}
4477 Set a breakpoint enabled only for one stop. The @var{args} are the
4478 same as for the @code{break} command, and the breakpoint is set in the same
4479 way, but the breakpoint is automatically deleted after the first time your
4480 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4483 @cindex hardware breakpoints
4484 @item hbreak @var{args}
4485 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4486 @code{break} command and the breakpoint is set in the same way, but the
4487 breakpoint requires hardware support and some target hardware may not
4488 have this support. The main purpose of this is EPROM/ROM code
4489 debugging, so you can set a breakpoint at an instruction without
4490 changing the instruction. This can be used with the new trap-generation
4491 provided by SPARClite DSU and most x86-based targets. These targets
4492 will generate traps when a program accesses some data or instruction
4493 address that is assigned to the debug registers. However the hardware
4494 breakpoint registers can take a limited number of breakpoints. For
4495 example, on the DSU, only two data breakpoints can be set at a time, and
4496 @value{GDBN} will reject this command if more than two are used. Delete
4497 or disable unused hardware breakpoints before setting new ones
4498 (@pxref{Disabling, ,Disabling Breakpoints}).
4499 @xref{Conditions, ,Break Conditions}.
4500 For remote targets, you can restrict the number of hardware
4501 breakpoints @value{GDBN} will use, see @ref{set remote
4502 hardware-breakpoint-limit}.
4505 @item thbreak @var{args}
4506 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4507 are the same as for the @code{hbreak} command and the breakpoint is set in
4508 the same way. However, like the @code{tbreak} command,
4509 the breakpoint is automatically deleted after the
4510 first time your program stops there. Also, like the @code{hbreak}
4511 command, the breakpoint requires hardware support and some target hardware
4512 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4513 See also @ref{Conditions, ,Break Conditions}.
4516 @cindex regular expression
4517 @cindex breakpoints at functions matching a regexp
4518 @cindex set breakpoints in many functions
4519 @item rbreak @var{regex}
4520 Set breakpoints on all functions matching the regular expression
4521 @var{regex}. This command sets an unconditional breakpoint on all
4522 matches, printing a list of all breakpoints it set. Once these
4523 breakpoints are set, they are treated just like the breakpoints set with
4524 the @code{break} command. You can delete them, disable them, or make
4525 them conditional the same way as any other breakpoint.
4527 In programs using different languages, @value{GDBN} chooses the syntax
4528 to print the list of all breakpoints it sets according to the
4529 @samp{set language} value: using @samp{set language auto}
4530 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4531 language of the breakpoint's function, other values mean to use
4532 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4534 The syntax of the regular expression is the standard one used with tools
4535 like @file{grep}. Note that this is different from the syntax used by
4536 shells, so for instance @code{foo*} matches all functions that include
4537 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4538 @code{.*} leading and trailing the regular expression you supply, so to
4539 match only functions that begin with @code{foo}, use @code{^foo}.
4541 @cindex non-member C@t{++} functions, set breakpoint in
4542 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4543 breakpoints on overloaded functions that are not members of any special
4546 @cindex set breakpoints on all functions
4547 The @code{rbreak} command can be used to set breakpoints in
4548 @strong{all} the functions in a program, like this:
4551 (@value{GDBP}) rbreak .
4554 @item rbreak @var{file}:@var{regex}
4555 If @code{rbreak} is called with a filename qualification, it limits
4556 the search for functions matching the given regular expression to the
4557 specified @var{file}. This can be used, for example, to set breakpoints on
4558 every function in a given file:
4561 (@value{GDBP}) rbreak file.c:.
4564 The colon separating the filename qualifier from the regex may
4565 optionally be surrounded by spaces.
4567 @kindex info breakpoints
4568 @cindex @code{$_} and @code{info breakpoints}
4569 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4570 @itemx info break @r{[}@var{list}@dots{}@r{]}
4571 Print a table of all breakpoints, watchpoints, and catchpoints set and
4572 not deleted. Optional argument @var{n} means print information only
4573 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4574 For each breakpoint, following columns are printed:
4577 @item Breakpoint Numbers
4579 Breakpoint, watchpoint, or catchpoint.
4581 Whether the breakpoint is marked to be disabled or deleted when hit.
4582 @item Enabled or Disabled
4583 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4584 that are not enabled.
4586 Where the breakpoint is in your program, as a memory address. For a
4587 pending breakpoint whose address is not yet known, this field will
4588 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4589 library that has the symbol or line referred by breakpoint is loaded.
4590 See below for details. A breakpoint with several locations will
4591 have @samp{<MULTIPLE>} in this field---see below for details.
4593 Where the breakpoint is in the source for your program, as a file and
4594 line number. For a pending breakpoint, the original string passed to
4595 the breakpoint command will be listed as it cannot be resolved until
4596 the appropriate shared library is loaded in the future.
4600 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4601 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4602 @value{GDBN} on the host's side. If it is ``target'', then the condition
4603 is evaluated by the target. The @code{info break} command shows
4604 the condition on the line following the affected breakpoint, together with
4605 its condition evaluation mode in between parentheses.
4607 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4608 allowed to have a condition specified for it. The condition is not parsed for
4609 validity until a shared library is loaded that allows the pending
4610 breakpoint to resolve to a valid location.
4613 @code{info break} with a breakpoint
4614 number @var{n} as argument lists only that breakpoint. The
4615 convenience variable @code{$_} and the default examining-address for
4616 the @code{x} command are set to the address of the last breakpoint
4617 listed (@pxref{Memory, ,Examining Memory}).
4620 @code{info break} displays a count of the number of times the breakpoint
4621 has been hit. This is especially useful in conjunction with the
4622 @code{ignore} command. You can ignore a large number of breakpoint
4623 hits, look at the breakpoint info to see how many times the breakpoint
4624 was hit, and then run again, ignoring one less than that number. This
4625 will get you quickly to the last hit of that breakpoint.
4628 For a breakpoints with an enable count (xref) greater than 1,
4629 @code{info break} also displays that count.
4633 @value{GDBN} allows you to set any number of breakpoints at the same place in
4634 your program. There is nothing silly or meaningless about this. When
4635 the breakpoints are conditional, this is even useful
4636 (@pxref{Conditions, ,Break Conditions}).
4638 @cindex multiple locations, breakpoints
4639 @cindex breakpoints, multiple locations
4640 It is possible that a single logical breakpoint is set at several code
4641 locations in your program. @xref{Location Specifications}, for
4644 A breakpoint with multiple code locations is displayed in the
4645 breakpoint table using several rows---one header row, followed by one
4646 row for each code location. The header row has @samp{<MULTIPLE>} in
4647 the address column. Each code location row contains the actual
4648 address, source file, source line and function of its code location.
4649 The number column for a code location is of the form
4650 @var{breakpoint-number}.@var{location-number}.
4655 Num Type Disp Enb Address What
4656 1 breakpoint keep y <MULTIPLE>
4658 breakpoint already hit 1 time
4659 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4660 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4663 You cannot delete the individual locations from a breakpoint. However,
4664 each location can be individually enabled or disabled by passing
4665 @var{breakpoint-number}.@var{location-number} as argument to the
4666 @code{enable} and @code{disable} commands. It's also possible to
4667 @code{enable} and @code{disable} a range of @var{location-number}
4668 locations using a @var{breakpoint-number} and two @var{location-number}s,
4669 in increasing order, separated by a hyphen, like
4670 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4671 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4672 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4673 all of the locations that belong to that breakpoint.
4675 Locations that are enabled while their parent breakpoint is disabled
4676 won't trigger a break, and are denoted by @code{y-} in the @code{Enb}
4677 column. For example:
4680 (@value{GDBP}) info breakpoints
4681 Num Type Disp Enb Address What
4682 1 breakpoint keep n <MULTIPLE>
4683 1.1 y- 0x00000000000011b6 in ...
4684 1.2 y- 0x00000000000011c2 in ...
4685 1.3 n 0x00000000000011ce in ...
4688 @cindex pending breakpoints
4689 It's quite common to have a breakpoint inside a shared library.
4690 Shared libraries can be loaded and unloaded explicitly,
4691 and possibly repeatedly, as the program is executed. To support
4692 this use case, @value{GDBN} updates breakpoint locations whenever
4693 any shared library is loaded or unloaded. Typically, you would
4694 set a breakpoint in a shared library at the beginning of your
4695 debugging session, when the library is not loaded, and when the
4696 symbols from the library are not available. When you try to set
4697 breakpoint, @value{GDBN} will ask you if you want to set
4698 a so called @dfn{pending breakpoint}---breakpoint whose address
4699 is not yet resolved.
4701 After the program is run, whenever a new shared library is loaded,
4702 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4703 shared library contains the symbol or line referred to by some
4704 pending breakpoint, that breakpoint is resolved and becomes an
4705 ordinary breakpoint. When a library is unloaded, all breakpoints
4706 that refer to its symbols or source lines become pending again.
4708 This logic works for breakpoints with multiple locations, too. For
4709 example, if you have a breakpoint in a C@t{++} template function, and
4710 a newly loaded shared library has an instantiation of that template,
4711 a new location is added to the list of locations for the breakpoint.
4713 Except for having unresolved address, pending breakpoints do not
4714 differ from regular breakpoints. You can set conditions or commands,
4715 enable and disable them and perform other breakpoint operations.
4717 @value{GDBN} provides some additional commands for controlling what
4718 happens when the @samp{break} command cannot resolve the location spec
4719 to any code location in your program (@pxref{Location
4722 @kindex set breakpoint pending
4723 @kindex show breakpoint pending
4725 @item set breakpoint pending auto
4726 This is the default behavior. When @value{GDBN} cannot resolve the
4727 location spec, it queries you whether a pending breakpoint should be
4730 @item set breakpoint pending on
4731 This indicates that when @value{GDBN} cannot resolve the location
4732 spec, it should create a pending breakpoint without confirmation.
4734 @item set breakpoint pending off
4735 This indicates that pending breakpoints are not to be created. If
4736 @value{GDBN} cannot resolve the location spec, it aborts the
4737 breakpoint creation with an error. This setting does not affect any
4738 pending breakpoints previously created.
4740 @item show breakpoint pending
4741 Show the current behavior setting for creating pending breakpoints.
4744 The settings above only affect the @code{break} command and its
4745 variants. Once a breakpoint is set, it will be automatically updated
4746 as shared libraries are loaded and unloaded.
4748 @cindex automatic hardware breakpoints
4749 For some targets, @value{GDBN} can automatically decide if hardware or
4750 software breakpoints should be used, depending on whether the
4751 breakpoint address is read-only or read-write. This applies to
4752 breakpoints set with the @code{break} command as well as to internal
4753 breakpoints set by commands like @code{next} and @code{finish}. For
4754 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4757 You can control this automatic behaviour with the following commands:
4759 @kindex set breakpoint auto-hw
4760 @kindex show breakpoint auto-hw
4762 @item set breakpoint auto-hw on
4763 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4764 will try to use the target memory map to decide if software or hardware
4765 breakpoint must be used.
4767 @item set breakpoint auto-hw off
4768 This indicates @value{GDBN} should not automatically select breakpoint
4769 type. If the target provides a memory map, @value{GDBN} will warn when
4770 trying to set software breakpoint at a read-only address.
4773 @value{GDBN} normally implements breakpoints by replacing the program code
4774 at the breakpoint address with a special instruction, which, when
4775 executed, given control to the debugger. By default, the program
4776 code is so modified only when the program is resumed. As soon as
4777 the program stops, @value{GDBN} restores the original instructions. This
4778 behaviour guards against leaving breakpoints inserted in the
4779 target should gdb abrubptly disconnect. However, with slow remote
4780 targets, inserting and removing breakpoint can reduce the performance.
4781 This behavior can be controlled with the following commands::
4783 @kindex set breakpoint always-inserted
4784 @kindex show breakpoint always-inserted
4786 @item set breakpoint always-inserted off
4787 All breakpoints, including newly added by the user, are inserted in
4788 the target only when the target is resumed. All breakpoints are
4789 removed from the target when it stops. This is the default mode.
4791 @item set breakpoint always-inserted on
4792 Causes all breakpoints to be inserted in the target at all times. If
4793 the user adds a new breakpoint, or changes an existing breakpoint, the
4794 breakpoints in the target are updated immediately. A breakpoint is
4795 removed from the target only when breakpoint itself is deleted.
4798 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4799 when a breakpoint breaks. If the condition is true, then the process being
4800 debugged stops, otherwise the process is resumed.
4802 If the target supports evaluating conditions on its end, @value{GDBN} may
4803 download the breakpoint, together with its conditions, to it.
4805 This feature can be controlled via the following commands:
4807 @kindex set breakpoint condition-evaluation
4808 @kindex show breakpoint condition-evaluation
4810 @item set breakpoint condition-evaluation host
4811 This option commands @value{GDBN} to evaluate the breakpoint
4812 conditions on the host's side. Unconditional breakpoints are sent to
4813 the target which in turn receives the triggers and reports them back to GDB
4814 for condition evaluation. This is the standard evaluation mode.
4816 @item set breakpoint condition-evaluation target
4817 This option commands @value{GDBN} to download breakpoint conditions
4818 to the target at the moment of their insertion. The target
4819 is responsible for evaluating the conditional expression and reporting
4820 breakpoint stop events back to @value{GDBN} whenever the condition
4821 is true. Due to limitations of target-side evaluation, some conditions
4822 cannot be evaluated there, e.g., conditions that depend on local data
4823 that is only known to the host. Examples include
4824 conditional expressions involving convenience variables, complex types
4825 that cannot be handled by the agent expression parser and expressions
4826 that are too long to be sent over to the target, specially when the
4827 target is a remote system. In these cases, the conditions will be
4828 evaluated by @value{GDBN}.
4830 @item set breakpoint condition-evaluation auto
4831 This is the default mode. If the target supports evaluating breakpoint
4832 conditions on its end, @value{GDBN} will download breakpoint conditions to
4833 the target (limitations mentioned previously apply). If the target does
4834 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4835 to evaluating all these conditions on the host's side.
4839 @cindex negative breakpoint numbers
4840 @cindex internal @value{GDBN} breakpoints
4841 @value{GDBN} itself sometimes sets breakpoints in your program for
4842 special purposes, such as proper handling of @code{longjmp} (in C
4843 programs). These internal breakpoints are assigned negative numbers,
4844 starting with @code{-1}; @samp{info breakpoints} does not display them.
4845 You can see these breakpoints with the @value{GDBN} maintenance command
4846 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4849 @node Set Watchpoints
4850 @subsection Setting Watchpoints
4852 @cindex setting watchpoints
4853 You can use a watchpoint to stop execution whenever the value of an
4854 expression changes, without having to predict a particular place where
4855 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4856 The expression may be as simple as the value of a single variable, or
4857 as complex as many variables combined by operators. Examples include:
4861 A reference to the value of a single variable.
4864 An address cast to an appropriate data type. For example,
4865 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4866 address (assuming an @code{int} occupies 4 bytes).
4869 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4870 expression can use any operators valid in the program's native
4871 language (@pxref{Languages}).
4874 You can set a watchpoint on an expression even if the expression can
4875 not be evaluated yet. For instance, you can set a watchpoint on
4876 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4877 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4878 the expression produces a valid value. If the expression becomes
4879 valid in some other way than changing a variable (e.g.@: if the memory
4880 pointed to by @samp{*global_ptr} becomes readable as the result of a
4881 @code{malloc} call), @value{GDBN} may not stop until the next time
4882 the expression changes.
4884 @cindex software watchpoints
4885 @cindex hardware watchpoints
4886 Depending on your system, watchpoints may be implemented in software or
4887 hardware. @value{GDBN} does software watchpointing by single-stepping your
4888 program and testing the variable's value each time, which is hundreds of
4889 times slower than normal execution. (But this may still be worth it, to
4890 catch errors where you have no clue what part of your program is the
4893 On some systems, such as most PowerPC or x86-based targets,
4894 @value{GDBN} includes support for hardware watchpoints, which do not
4895 slow down the running of your program.
4899 @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{]}
4900 Set a watchpoint for an expression. @value{GDBN} will break when the
4901 expression @var{expr} is written into by the program and its value
4902 changes. The simplest (and the most popular) use of this command is
4903 to watch the value of a single variable:
4906 (@value{GDBP}) watch foo
4909 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4910 argument, @value{GDBN} breaks only when the thread identified by
4911 @var{thread-id} changes the value of @var{expr}. If any other threads
4912 change the value of @var{expr}, @value{GDBN} will not break. Note
4913 that watchpoints restricted to a single thread in this way only work
4914 with Hardware Watchpoints.
4916 Similarly, if the @code{task} argument is given, then the watchpoint
4917 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
4919 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4920 (see below). The @code{-location} argument tells @value{GDBN} to
4921 instead watch the memory referred to by @var{expr}. In this case,
4922 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4923 and watch the memory at that address. The type of the result is used
4924 to determine the size of the watched memory. If the expression's
4925 result does not have an address, then @value{GDBN} will print an
4928 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4929 of masked watchpoints, if the current architecture supports this
4930 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4931 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4932 to an address to watch. The mask specifies that some bits of an address
4933 (the bits which are reset in the mask) should be ignored when matching
4934 the address accessed by the inferior against the watchpoint address.
4935 Thus, a masked watchpoint watches many addresses simultaneously---those
4936 addresses whose unmasked bits are identical to the unmasked bits in the
4937 watchpoint address. The @code{mask} argument implies @code{-location}.
4941 (@value{GDBP}) watch foo mask 0xffff00ff
4942 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4946 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4947 Set a watchpoint that will break when the value of @var{expr} is read
4951 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4952 Set a watchpoint that will break when @var{expr} is either read from
4953 or written into by the program.
4955 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4956 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4957 This command prints a list of watchpoints, using the same format as
4958 @code{info break} (@pxref{Set Breaks}).
4961 If you watch for a change in a numerically entered address you need to
4962 dereference it, as the address itself is just a constant number which will
4963 never change. @value{GDBN} refuses to create a watchpoint that watches
4964 a never-changing value:
4967 (@value{GDBP}) watch 0x600850
4968 Cannot watch constant value 0x600850.
4969 (@value{GDBP}) watch *(int *) 0x600850
4970 Watchpoint 1: *(int *) 6293584
4973 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4974 watchpoints execute very quickly, and the debugger reports a change in
4975 value at the exact instruction where the change occurs. If @value{GDBN}
4976 cannot set a hardware watchpoint, it sets a software watchpoint, which
4977 executes more slowly and reports the change in value at the next
4978 @emph{statement}, not the instruction, after the change occurs.
4980 @cindex use only software watchpoints
4981 You can force @value{GDBN} to use only software watchpoints with the
4982 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4983 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4984 the underlying system supports them. (Note that hardware-assisted
4985 watchpoints that were set @emph{before} setting
4986 @code{can-use-hw-watchpoints} to zero will still use the hardware
4987 mechanism of watching expression values.)
4990 @item set can-use-hw-watchpoints
4991 @kindex set can-use-hw-watchpoints
4992 Set whether or not to use hardware watchpoints.
4994 @item show can-use-hw-watchpoints
4995 @kindex show can-use-hw-watchpoints
4996 Show the current mode of using hardware watchpoints.
4999 For remote targets, you can restrict the number of hardware
5000 watchpoints @value{GDBN} will use, see @ref{set remote
5001 hardware-breakpoint-limit}.
5003 When you issue the @code{watch} command, @value{GDBN} reports
5006 Hardware watchpoint @var{num}: @var{expr}
5010 if it was able to set a hardware watchpoint.
5012 Currently, the @code{awatch} and @code{rwatch} commands can only set
5013 hardware watchpoints, because accesses to data that don't change the
5014 value of the watched expression cannot be detected without examining
5015 every instruction as it is being executed, and @value{GDBN} does not do
5016 that currently. If @value{GDBN} finds that it is unable to set a
5017 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
5018 will print a message like this:
5021 Expression cannot be implemented with read/access watchpoint.
5024 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5025 data type of the watched expression is wider than what a hardware
5026 watchpoint on the target machine can handle. For example, some systems
5027 can only watch regions that are up to 4 bytes wide; on such systems you
5028 cannot set hardware watchpoints for an expression that yields a
5029 double-precision floating-point number (which is typically 8 bytes
5030 wide). As a work-around, it might be possible to break the large region
5031 into a series of smaller ones and watch them with separate watchpoints.
5033 If you set too many hardware watchpoints, @value{GDBN} might be unable
5034 to insert all of them when you resume the execution of your program.
5035 Since the precise number of active watchpoints is unknown until such
5036 time as the program is about to be resumed, @value{GDBN} might not be
5037 able to warn you about this when you set the watchpoints, and the
5038 warning will be printed only when the program is resumed:
5041 Hardware watchpoint @var{num}: Could not insert watchpoint
5045 If this happens, delete or disable some of the watchpoints.
5047 Watching complex expressions that reference many variables can also
5048 exhaust the resources available for hardware-assisted watchpoints.
5049 That's because @value{GDBN} needs to watch every variable in the
5050 expression with separately allocated resources.
5052 If you call a function interactively using @code{print} or @code{call},
5053 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5054 kind of breakpoint or the call completes.
5056 @value{GDBN} automatically deletes watchpoints that watch local
5057 (automatic) variables, or expressions that involve such variables, when
5058 they go out of scope, that is, when the execution leaves the block in
5059 which these variables were defined. In particular, when the program
5060 being debugged terminates, @emph{all} local variables go out of scope,
5061 and so only watchpoints that watch global variables remain set. If you
5062 rerun the program, you will need to set all such watchpoints again. One
5063 way of doing that would be to set a code breakpoint at the entry to the
5064 @code{main} function and when it breaks, set all the watchpoints.
5066 @cindex watchpoints and threads
5067 @cindex threads and watchpoints
5068 In multi-threaded programs, watchpoints will detect changes to the
5069 watched expression from every thread.
5072 @emph{Warning:} In multi-threaded programs, software watchpoints
5073 have only limited usefulness. If @value{GDBN} creates a software
5074 watchpoint, it can only watch the value of an expression @emph{in a
5075 single thread}. If you are confident that the expression can only
5076 change due to the current thread's activity (and if you are also
5077 confident that no other thread can become current), then you can use
5078 software watchpoints as usual. However, @value{GDBN} may not notice
5079 when a non-current thread's activity changes the expression. (Hardware
5080 watchpoints, in contrast, watch an expression in all threads.)
5083 @xref{set remote hardware-watchpoint-limit}.
5085 @node Set Catchpoints
5086 @subsection Setting Catchpoints
5087 @cindex catchpoints, setting
5088 @cindex exception handlers
5089 @cindex event handling
5091 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5092 kinds of program events, such as C@t{++} exceptions or the loading of a
5093 shared library. Use the @code{catch} command to set a catchpoint.
5097 @item catch @var{event}
5098 Stop when @var{event} occurs. The @var{event} can be any of the following:
5101 @item throw @r{[}@var{regexp}@r{]}
5102 @itemx rethrow @r{[}@var{regexp}@r{]}
5103 @itemx catch @r{[}@var{regexp}@r{]}
5105 @kindex catch rethrow
5107 @cindex stop on C@t{++} exceptions
5108 The throwing, re-throwing, or catching of a C@t{++} exception.
5110 If @var{regexp} is given, then only exceptions whose type matches the
5111 regular expression will be caught.
5113 @vindex $_exception@r{, convenience variable}
5114 The convenience variable @code{$_exception} is available at an
5115 exception-related catchpoint, on some systems. This holds the
5116 exception being thrown.
5118 There are currently some limitations to C@t{++} exception handling in
5123 The support for these commands is system-dependent. Currently, only
5124 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5128 The regular expression feature and the @code{$_exception} convenience
5129 variable rely on the presence of some SDT probes in @code{libstdc++}.
5130 If these probes are not present, then these features cannot be used.
5131 These probes were first available in the GCC 4.8 release, but whether
5132 or not they are available in your GCC also depends on how it was
5136 The @code{$_exception} convenience variable is only valid at the
5137 instruction at which an exception-related catchpoint is set.
5140 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5141 location in the system library which implements runtime exception
5142 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5143 (@pxref{Selection}) to get to your code.
5146 If you call a function interactively, @value{GDBN} normally returns
5147 control to you when the function has finished executing. If the call
5148 raises an exception, however, the call may bypass the mechanism that
5149 returns control to you and cause your program either to abort or to
5150 simply continue running until it hits a breakpoint, catches a signal
5151 that @value{GDBN} is listening for, or exits. This is the case even if
5152 you set a catchpoint for the exception; catchpoints on exceptions are
5153 disabled within interactive calls. @xref{Calling}, for information on
5154 controlling this with @code{set unwind-on-terminating-exception}.
5157 You cannot raise an exception interactively.
5160 You cannot install an exception handler interactively.
5163 @item exception @r{[}@var{name}@r{]}
5164 @kindex catch exception
5165 @cindex Ada exception catching
5166 @cindex catch Ada exceptions
5167 An Ada exception being raised. If an exception name is specified
5168 at the end of the command (eg @code{catch exception Program_Error}),
5169 the debugger will stop only when this specific exception is raised.
5170 Otherwise, the debugger stops execution when any Ada exception is raised.
5172 When inserting an exception catchpoint on a user-defined exception whose
5173 name is identical to one of the exceptions defined by the language, the
5174 fully qualified name must be used as the exception name. Otherwise,
5175 @value{GDBN} will assume that it should stop on the pre-defined exception
5176 rather than the user-defined one. For instance, assuming an exception
5177 called @code{Constraint_Error} is defined in package @code{Pck}, then
5178 the command to use to catch such exceptions is @kbd{catch exception
5179 Pck.Constraint_Error}.
5181 @vindex $_ada_exception@r{, convenience variable}
5182 The convenience variable @code{$_ada_exception} holds the address of
5183 the exception being thrown. This can be useful when setting a
5184 condition for such a catchpoint.
5186 @item exception unhandled
5187 @kindex catch exception unhandled
5188 An exception that was raised but is not handled by the program. The
5189 convenience variable @code{$_ada_exception} is set as for @code{catch
5192 @item handlers @r{[}@var{name}@r{]}
5193 @kindex catch handlers
5194 @cindex Ada exception handlers catching
5195 @cindex catch Ada exceptions when handled
5196 An Ada exception being handled. If an exception name is
5197 specified at the end of the command
5198 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5199 only when this specific exception is handled.
5200 Otherwise, the debugger stops execution when any Ada exception is handled.
5202 When inserting a handlers catchpoint on a user-defined
5203 exception whose name is identical to one of the exceptions
5204 defined by the language, the fully qualified name must be used
5205 as the exception name. Otherwise, @value{GDBN} will assume that it
5206 should stop on the pre-defined exception rather than the
5207 user-defined one. For instance, assuming an exception called
5208 @code{Constraint_Error} is defined in package @code{Pck}, then the
5209 command to use to catch such exceptions handling is
5210 @kbd{catch handlers Pck.Constraint_Error}.
5212 The convenience variable @code{$_ada_exception} is set as for
5213 @code{catch exception}.
5216 @kindex catch assert
5217 A failed Ada assertion. Note that the convenience variable
5218 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5222 @cindex break on fork/exec
5223 A call to @code{exec}.
5225 @anchor{catch syscall}
5227 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5228 @kindex catch syscall
5229 @cindex break on a system call.
5230 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5231 syscall is a mechanism for application programs to request a service
5232 from the operating system (OS) or one of the OS system services.
5233 @value{GDBN} can catch some or all of the syscalls issued by the
5234 debuggee, and show the related information for each syscall. If no
5235 argument is specified, calls to and returns from all system calls
5238 @var{name} can be any system call name that is valid for the
5239 underlying OS. Just what syscalls are valid depends on the OS. On
5240 GNU and Unix systems, you can find the full list of valid syscall
5241 names on @file{/usr/include/asm/unistd.h}.
5243 @c For MS-Windows, the syscall names and the corresponding numbers
5244 @c can be found, e.g., on this URL:
5245 @c http://www.metasploit.com/users/opcode/syscalls.html
5246 @c but we don't support Windows syscalls yet.
5248 Normally, @value{GDBN} knows in advance which syscalls are valid for
5249 each OS, so you can use the @value{GDBN} command-line completion
5250 facilities (@pxref{Completion,, command completion}) to list the
5253 You may also specify the system call numerically. A syscall's
5254 number is the value passed to the OS's syscall dispatcher to
5255 identify the requested service. When you specify the syscall by its
5256 name, @value{GDBN} uses its database of syscalls to convert the name
5257 into the corresponding numeric code, but using the number directly
5258 may be useful if @value{GDBN}'s database does not have the complete
5259 list of syscalls on your system (e.g., because @value{GDBN} lags
5260 behind the OS upgrades).
5262 You may specify a group of related syscalls to be caught at once using
5263 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5264 instance, on some platforms @value{GDBN} allows you to catch all
5265 network related syscalls, by passing the argument @code{group:network}
5266 to @code{catch syscall}. Note that not all syscall groups are
5267 available in every system. You can use the command completion
5268 facilities (@pxref{Completion,, command completion}) to list the
5269 syscall groups available on your environment.
5271 The example below illustrates how this command works if you don't provide
5275 (@value{GDBP}) catch syscall
5276 Catchpoint 1 (syscall)
5278 Starting program: /tmp/catch-syscall
5280 Catchpoint 1 (call to syscall 'close'), \
5281 0xffffe424 in __kernel_vsyscall ()
5285 Catchpoint 1 (returned from syscall 'close'), \
5286 0xffffe424 in __kernel_vsyscall ()
5290 Here is an example of catching a system call by name:
5293 (@value{GDBP}) catch syscall chroot
5294 Catchpoint 1 (syscall 'chroot' [61])
5296 Starting program: /tmp/catch-syscall
5298 Catchpoint 1 (call to syscall 'chroot'), \
5299 0xffffe424 in __kernel_vsyscall ()
5303 Catchpoint 1 (returned from syscall 'chroot'), \
5304 0xffffe424 in __kernel_vsyscall ()
5308 An example of specifying a system call numerically. In the case
5309 below, the syscall number has a corresponding entry in the XML
5310 file, so @value{GDBN} finds its name and prints it:
5313 (@value{GDBP}) catch syscall 252
5314 Catchpoint 1 (syscall(s) 'exit_group')
5316 Starting program: /tmp/catch-syscall
5318 Catchpoint 1 (call to syscall 'exit_group'), \
5319 0xffffe424 in __kernel_vsyscall ()
5323 Program exited normally.
5327 Here is an example of catching a syscall group:
5330 (@value{GDBP}) catch syscall group:process
5331 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5332 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5333 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5335 Starting program: /tmp/catch-syscall
5337 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5338 from /lib64/ld-linux-x86-64.so.2
5344 However, there can be situations when there is no corresponding name
5345 in XML file for that syscall number. In this case, @value{GDBN} prints
5346 a warning message saying that it was not able to find the syscall name,
5347 but the catchpoint will be set anyway. See the example below:
5350 (@value{GDBP}) catch syscall 764
5351 warning: The number '764' does not represent a known syscall.
5352 Catchpoint 2 (syscall 764)
5356 If you configure @value{GDBN} using the @samp{--without-expat} option,
5357 it will not be able to display syscall names. Also, if your
5358 architecture does not have an XML file describing its system calls,
5359 you will not be able to see the syscall names. It is important to
5360 notice that these two features are used for accessing the syscall
5361 name database. In either case, you will see a warning like this:
5364 (@value{GDBP}) catch syscall
5365 warning: Could not open "syscalls/i386-linux.xml"
5366 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5367 GDB will not be able to display syscall names.
5368 Catchpoint 1 (syscall)
5372 Of course, the file name will change depending on your architecture and system.
5374 Still using the example above, you can also try to catch a syscall by its
5375 number. In this case, you would see something like:
5378 (@value{GDBP}) catch syscall 252
5379 Catchpoint 1 (syscall(s) 252)
5382 Again, in this case @value{GDBN} would not be able to display syscall's names.
5386 A call to @code{fork}.
5390 A call to @code{vfork}.
5392 @item load @r{[}@var{regexp}@r{]}
5393 @itemx unload @r{[}@var{regexp}@r{]}
5395 @kindex catch unload
5396 The loading or unloading of a shared library. If @var{regexp} is
5397 given, then the catchpoint will stop only if the regular expression
5398 matches one of the affected libraries.
5400 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5401 @kindex catch signal
5402 The delivery of a signal.
5404 With no arguments, this catchpoint will catch any signal that is not
5405 used internally by @value{GDBN}, specifically, all signals except
5406 @samp{SIGTRAP} and @samp{SIGINT}.
5408 With the argument @samp{all}, all signals, including those used by
5409 @value{GDBN}, will be caught. This argument cannot be used with other
5412 Otherwise, the arguments are a list of signal names as given to
5413 @code{handle} (@pxref{Signals}). Only signals specified in this list
5416 One reason that @code{catch signal} can be more useful than
5417 @code{handle} is that you can attach commands and conditions to the
5420 When a signal is caught by a catchpoint, the signal's @code{stop} and
5421 @code{print} settings, as specified by @code{handle}, are ignored.
5422 However, whether the signal is still delivered to the inferior depends
5423 on the @code{pass} setting; this can be changed in the catchpoint's
5428 @item tcatch @var{event}
5430 Set a catchpoint that is enabled only for one stop. The catchpoint is
5431 automatically deleted after the first time the event is caught.
5435 Use the @code{info break} command to list the current catchpoints.
5439 @subsection Deleting Breakpoints
5441 @cindex clearing breakpoints, watchpoints, catchpoints
5442 @cindex deleting breakpoints, watchpoints, catchpoints
5443 It is often necessary to eliminate a breakpoint, watchpoint, or
5444 catchpoint once it has done its job and you no longer want your program
5445 to stop there. This is called @dfn{deleting} the breakpoint. A
5446 breakpoint that has been deleted no longer exists; it is forgotten.
5448 With the @code{clear} command you can delete breakpoints according to
5449 where they are in your program. With the @code{delete} command you can
5450 delete individual breakpoints, watchpoints, or catchpoints by specifying
5451 their breakpoint numbers.
5453 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5454 automatically ignores breakpoints on the first instruction to be executed
5455 when you continue execution without changing the execution address.
5460 Delete any breakpoints at the next instruction to be executed in the
5461 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5462 the innermost frame is selected, this is a good way to delete a
5463 breakpoint where your program just stopped.
5465 @item clear @var{locspec}
5466 Delete any breakpoint with a code location that corresponds to
5467 @var{locspec}. @xref{Location Specifications}, for the various forms
5468 of @var{locspec}. Which code locations correspond to @var{locspec}
5469 depends on the form used in the location specification @var{locspec}:
5473 @itemx @var{filename}:@var{linenum}
5474 @itemx -line @var{linenum}
5475 @itemx -source @var{filename} -line @var{linenum}
5476 If @var{locspec} specifies a line number, with or without a file name,
5477 the command deletes any breakpoint with a code location that is at or
5478 within the specified line @var{linenum} in files that match the
5479 specified @var{filename}. If @var{filename} is omitted, it defaults
5480 to the current source file.
5482 @item *@var{address}
5483 If @var{locspec} specifies an address, the command deletes any
5484 breakpoint with a code location that is at the given @var{address}.
5486 @item @var{function}
5487 @itemx -function @var{function}
5488 If @var{locspec} specifies a function, the command deletes any
5489 breakpoint with a code location that is at the entry to any function
5490 whose name matches @var{function}.
5493 Ambiguity in names of files and functions can be resolved as described
5494 in @ref{Location Specifications}.
5496 @cindex delete breakpoints
5498 @kindex d @r{(@code{delete})}
5499 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5500 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5501 list specified as argument. If no argument is specified, delete all
5502 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5503 confirm off}). You can abbreviate this command as @code{d}.
5507 @subsection Disabling Breakpoints
5509 @cindex enable/disable a breakpoint
5510 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5511 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5512 it had been deleted, but remembers the information on the breakpoint so
5513 that you can @dfn{enable} it again later.
5515 You disable and enable breakpoints, watchpoints, and catchpoints with
5516 the @code{enable} and @code{disable} commands, optionally specifying
5517 one or more breakpoint numbers as arguments. Use @code{info break} to
5518 print a list of all breakpoints, watchpoints, and catchpoints if you
5519 do not know which numbers to use.
5521 Disabling and enabling a breakpoint that has multiple locations
5522 affects all of its locations.
5524 A breakpoint, watchpoint, or catchpoint can have any of several
5525 different states of enablement:
5529 Enabled. The breakpoint stops your program. A breakpoint set
5530 with the @code{break} command starts out in this state.
5532 Disabled. The breakpoint has no effect on your program.
5534 Enabled once. The breakpoint stops your program, but then becomes
5537 Enabled for a count. The breakpoint stops your program for the next
5538 N times, then becomes disabled.
5540 Enabled for deletion. The breakpoint stops your program, but
5541 immediately after it does so it is deleted permanently. A breakpoint
5542 set with the @code{tbreak} command starts out in this state.
5545 You can use the following commands to enable or disable breakpoints,
5546 watchpoints, and catchpoints:
5550 @kindex dis @r{(@code{disable})}
5551 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5552 Disable the specified breakpoints---or all breakpoints, if none are
5553 listed. A disabled breakpoint has no effect but is not forgotten. All
5554 options such as ignore-counts, conditions and commands are remembered in
5555 case the breakpoint is enabled again later. You may abbreviate
5556 @code{disable} as @code{dis}.
5559 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5560 Enable the specified breakpoints (or all defined breakpoints). They
5561 become effective once again in stopping your program.
5563 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5564 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5565 of these breakpoints immediately after stopping your program.
5567 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5568 Enable the specified breakpoints temporarily. @value{GDBN} records
5569 @var{count} with each of the specified breakpoints, and decrements a
5570 breakpoint's count when it is hit. When any count reaches 0,
5571 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5572 count (@pxref{Conditions, ,Break Conditions}), that will be
5573 decremented to 0 before @var{count} is affected.
5575 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5576 Enable the specified breakpoints to work once, then die. @value{GDBN}
5577 deletes any of these breakpoints as soon as your program stops there.
5578 Breakpoints set by the @code{tbreak} command start out in this state.
5581 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5582 @c confusing: tbreak is also initially enabled.
5583 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5584 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5585 subsequently, they become disabled or enabled only when you use one of
5586 the commands above. (The command @code{until} can set and delete a
5587 breakpoint of its own, but it does not change the state of your other
5588 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5592 @subsection Break Conditions
5593 @cindex conditional breakpoints
5594 @cindex breakpoint conditions
5596 @c FIXME what is scope of break condition expr? Context where wanted?
5597 @c in particular for a watchpoint?
5598 The simplest sort of breakpoint breaks every time your program reaches a
5599 specified place. You can also specify a @dfn{condition} for a
5600 breakpoint. A condition is just a Boolean expression in your
5601 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5602 a condition evaluates the expression each time your program reaches it,
5603 and your program stops only if the condition is @emph{true}.
5605 This is the converse of using assertions for program validation; in that
5606 situation, you want to stop when the assertion is violated---that is,
5607 when the condition is false. In C, if you want to test an assertion expressed
5608 by the condition @var{assert}, you should set the condition
5609 @samp{! @var{assert}} on the appropriate breakpoint.
5611 Conditions are also accepted for watchpoints; you may not need them,
5612 since a watchpoint is inspecting the value of an expression anyhow---but
5613 it might be simpler, say, to just set a watchpoint on a variable name,
5614 and specify a condition that tests whether the new value is an interesting
5617 Break conditions can have side effects, and may even call functions in
5618 your program. This can be useful, for example, to activate functions
5619 that log program progress, or to use your own print functions to
5620 format special data structures. The effects are completely predictable
5621 unless there is another enabled breakpoint at the same address. (In
5622 that case, @value{GDBN} might see the other breakpoint first and stop your
5623 program without checking the condition of this one.) Note that
5624 breakpoint commands are usually more convenient and flexible than break
5626 purpose of performing side effects when a breakpoint is reached
5627 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5629 Breakpoint conditions can also be evaluated on the target's side if
5630 the target supports it. Instead of evaluating the conditions locally,
5631 @value{GDBN} encodes the expression into an agent expression
5632 (@pxref{Agent Expressions}) suitable for execution on the target,
5633 independently of @value{GDBN}. Global variables become raw memory
5634 locations, locals become stack accesses, and so forth.
5636 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5637 when its condition evaluates to true. This mechanism may provide faster
5638 response times depending on the performance characteristics of the target
5639 since it does not need to keep @value{GDBN} informed about
5640 every breakpoint trigger, even those with false conditions.
5642 Break conditions can be specified when a breakpoint is set, by using
5643 @samp{if} in the arguments to the @code{break} command. @xref{Set
5644 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5645 with the @code{condition} command.
5647 You can also use the @code{if} keyword with the @code{watch} command.
5648 The @code{catch} command does not recognize the @code{if} keyword;
5649 @code{condition} is the only way to impose a further condition on a
5654 @item condition @var{bnum} @var{expression}
5655 Specify @var{expression} as the break condition for breakpoint,
5656 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5657 breakpoint @var{bnum} stops your program only if the value of
5658 @var{expression} is true (nonzero, in C). When you use
5659 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5660 syntactic correctness, and to determine whether symbols in it have
5661 referents in the context of your breakpoint. If @var{expression} uses
5662 symbols not referenced in the context of the breakpoint, @value{GDBN}
5663 prints an error message:
5666 No symbol "foo" in current context.
5671 not actually evaluate @var{expression} at the time the @code{condition}
5672 command (or a command that sets a breakpoint with a condition, like
5673 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5675 @item condition -force @var{bnum} @var{expression}
5676 When the @code{-force} flag is used, define the condition even if
5677 @var{expression} is invalid at all the current locations of breakpoint
5678 @var{bnum}. This is similar to the @code{-force-condition} option
5679 of the @code{break} command.
5681 @item condition @var{bnum}
5682 Remove the condition from breakpoint number @var{bnum}. It becomes
5683 an ordinary unconditional breakpoint.
5686 @cindex ignore count (of breakpoint)
5687 A special case of a breakpoint condition is to stop only when the
5688 breakpoint has been reached a certain number of times. This is so
5689 useful that there is a special way to do it, using the @dfn{ignore
5690 count} of the breakpoint. Every breakpoint has an ignore count, which
5691 is an integer. Most of the time, the ignore count is zero, and
5692 therefore has no effect. But if your program reaches a breakpoint whose
5693 ignore count is positive, then instead of stopping, it just decrements
5694 the ignore count by one and continues. As a result, if the ignore count
5695 value is @var{n}, the breakpoint does not stop the next @var{n} times
5696 your program reaches it.
5700 @item ignore @var{bnum} @var{count}
5701 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5702 The next @var{count} times the breakpoint is reached, your program's
5703 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5706 To make the breakpoint stop the next time it is reached, specify
5709 When you use @code{continue} to resume execution of your program from a
5710 breakpoint, you can specify an ignore count directly as an argument to
5711 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5712 Stepping,,Continuing and Stepping}.
5714 If a breakpoint has a positive ignore count and a condition, the
5715 condition is not checked. Once the ignore count reaches zero,
5716 @value{GDBN} resumes checking the condition.
5718 You could achieve the effect of the ignore count with a condition such
5719 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5720 is decremented each time. @xref{Convenience Vars, ,Convenience
5724 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5727 @node Break Commands
5728 @subsection Breakpoint Command Lists
5730 @cindex breakpoint commands
5731 You can give any breakpoint (or watchpoint or catchpoint) a series of
5732 commands to execute when your program stops due to that breakpoint. For
5733 example, you might want to print the values of certain expressions, or
5734 enable other breakpoints.
5738 @kindex end@r{ (breakpoint commands)}
5739 @item commands @r{[}@var{list}@dots{}@r{]}
5740 @itemx @dots{} @var{command-list} @dots{}
5742 Specify a list of commands for the given breakpoints. The commands
5743 themselves appear on the following lines. Type a line containing just
5744 @code{end} to terminate the commands.
5746 To remove all commands from a breakpoint, type @code{commands} and
5747 follow it immediately with @code{end}; that is, give no commands.
5749 With no argument, @code{commands} refers to the last breakpoint,
5750 watchpoint, or catchpoint set (not to the breakpoint most recently
5751 encountered). If the most recent breakpoints were set with a single
5752 command, then the @code{commands} will apply to all the breakpoints
5753 set by that command. This applies to breakpoints set by
5754 @code{rbreak}, and also applies when a single @code{break} command
5755 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5759 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5760 disabled within a @var{command-list}.
5762 You can use breakpoint commands to start your program up again. Simply
5763 use the @code{continue} command, or @code{step}, or any other command
5764 that resumes execution.
5766 Any other commands in the command list, after a command that resumes
5767 execution, are ignored. This is because any time you resume execution
5768 (even with a simple @code{next} or @code{step}), you may encounter
5769 another breakpoint---which could have its own command list, leading to
5770 ambiguities about which list to execute.
5773 If the first command you specify in a command list is @code{silent}, the
5774 usual message about stopping at a breakpoint is not printed. This may
5775 be desirable for breakpoints that are to print a specific message and
5776 then continue. If none of the remaining commands print anything, you
5777 see no sign that the breakpoint was reached. @code{silent} is
5778 meaningful only at the beginning of a breakpoint command list.
5780 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5781 print precisely controlled output, and are often useful in silent
5782 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5784 For example, here is how you could use breakpoint commands to print the
5785 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5791 printf "x is %d\n",x
5796 One application for breakpoint commands is to compensate for one bug so
5797 you can test for another. Put a breakpoint just after the erroneous line
5798 of code, give it a condition to detect the case in which something
5799 erroneous has been done, and give it commands to assign correct values
5800 to any variables that need them. End with the @code{continue} command
5801 so that your program does not stop, and start with the @code{silent}
5802 command so that no output is produced. Here is an example:
5813 @node Dynamic Printf
5814 @subsection Dynamic Printf
5816 @cindex dynamic printf
5818 The dynamic printf command @code{dprintf} combines a breakpoint with
5819 formatted printing of your program's data to give you the effect of
5820 inserting @code{printf} calls into your program on-the-fly, without
5821 having to recompile it.
5823 In its most basic form, the output goes to the GDB console. However,
5824 you can set the variable @code{dprintf-style} for alternate handling.
5825 For instance, you can ask to format the output by calling your
5826 program's @code{printf} function. This has the advantage that the
5827 characters go to the program's output device, so they can recorded in
5828 redirects to files and so forth.
5830 If you are doing remote debugging with a stub or agent, you can also
5831 ask to have the printf handled by the remote agent. In addition to
5832 ensuring that the output goes to the remote program's device along
5833 with any other output the program might produce, you can also ask that
5834 the dprintf remain active even after disconnecting from the remote
5835 target. Using the stub/agent is also more efficient, as it can do
5836 everything without needing to communicate with @value{GDBN}.
5840 @item dprintf @var{locspec},@var{template},@var{expression}[,@var{expression}@dots{}]
5841 Whenever execution reaches a code location that results from resolving
5842 @var{locspec}, print the values of one or more @var{expressions} under
5843 the control of the string @var{template}. To print several values,
5844 separate them with commas.
5846 @item set dprintf-style @var{style}
5847 Set the dprintf output to be handled in one of several different
5848 styles enumerated below. A change of style affects all existing
5849 dynamic printfs immediately. (If you need individual control over the
5850 print commands, simply define normal breakpoints with
5851 explicitly-supplied command lists.)
5855 @kindex dprintf-style gdb
5856 Handle the output using the @value{GDBN} @code{printf} command.
5859 @kindex dprintf-style call
5860 Handle the output by calling a function in your program (normally
5864 @kindex dprintf-style agent
5865 Have the remote debugging agent (such as @code{gdbserver}) handle
5866 the output itself. This style is only available for agents that
5867 support running commands on the target.
5870 @item set dprintf-function @var{function}
5871 Set the function to call if the dprintf style is @code{call}. By
5872 default its value is @code{printf}. You may set it to any expression.
5873 that @value{GDBN} can evaluate to a function, as per the @code{call}
5876 @item set dprintf-channel @var{channel}
5877 Set a ``channel'' for dprintf. If set to a non-empty value,
5878 @value{GDBN} will evaluate it as an expression and pass the result as
5879 a first argument to the @code{dprintf-function}, in the manner of
5880 @code{fprintf} and similar functions. Otherwise, the dprintf format
5881 string will be the first argument, in the manner of @code{printf}.
5883 As an example, if you wanted @code{dprintf} output to go to a logfile
5884 that is a standard I/O stream assigned to the variable @code{mylog},
5885 you could do the following:
5888 (gdb) set dprintf-style call
5889 (gdb) set dprintf-function fprintf
5890 (gdb) set dprintf-channel mylog
5891 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5892 Dprintf 1 at 0x123456: file main.c, line 25.
5894 1 dprintf keep y 0x00123456 in main at main.c:25
5895 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5900 Note that the @code{info break} displays the dynamic printf commands
5901 as normal breakpoint commands; you can thus easily see the effect of
5902 the variable settings.
5904 @item set disconnected-dprintf on
5905 @itemx set disconnected-dprintf off
5906 @kindex set disconnected-dprintf
5907 Choose whether @code{dprintf} commands should continue to run if
5908 @value{GDBN} has disconnected from the target. This only applies
5909 if the @code{dprintf-style} is @code{agent}.
5911 @item show disconnected-dprintf off
5912 @kindex show disconnected-dprintf
5913 Show the current choice for disconnected @code{dprintf}.
5917 @value{GDBN} does not check the validity of function and channel,
5918 relying on you to supply values that are meaningful for the contexts
5919 in which they are being used. For instance, the function and channel
5920 may be the values of local variables, but if that is the case, then
5921 all enabled dynamic prints must be at locations within the scope of
5922 those locals. If evaluation fails, @value{GDBN} will report an error.
5924 @node Save Breakpoints
5925 @subsection How to save breakpoints to a file
5927 To save breakpoint definitions to a file use the @w{@code{save
5928 breakpoints}} command.
5931 @kindex save breakpoints
5932 @cindex save breakpoints to a file for future sessions
5933 @item save breakpoints [@var{filename}]
5934 This command saves all current breakpoint definitions together with
5935 their commands and ignore counts, into a file @file{@var{filename}}
5936 suitable for use in a later debugging session. This includes all
5937 types of breakpoints (breakpoints, watchpoints, catchpoints,
5938 tracepoints). To read the saved breakpoint definitions, use the
5939 @code{source} command (@pxref{Command Files}). Note that watchpoints
5940 with expressions involving local variables may fail to be recreated
5941 because it may not be possible to access the context where the
5942 watchpoint is valid anymore. Because the saved breakpoint definitions
5943 are simply a sequence of @value{GDBN} commands that recreate the
5944 breakpoints, you can edit the file in your favorite editing program,
5945 and remove the breakpoint definitions you're not interested in, or
5946 that can no longer be recreated.
5949 @node Static Probe Points
5950 @subsection Static Probe Points
5952 @cindex static probe point, SystemTap
5953 @cindex static probe point, DTrace
5954 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5955 for Statically Defined Tracing, and the probes are designed to have a tiny
5956 runtime code and data footprint, and no dynamic relocations.
5958 Currently, the following types of probes are supported on
5959 ELF-compatible systems:
5963 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5964 @acronym{SDT} probes@footnote{See
5965 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5966 for more information on how to add @code{SystemTap} @acronym{SDT}
5967 probes in your applications.}. @code{SystemTap} probes are usable
5968 from assembly, C and C@t{++} languages@footnote{See
5969 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5970 for a good reference on how the @acronym{SDT} probes are implemented.}.
5972 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5973 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5977 @cindex semaphores on static probe points
5978 Some @code{SystemTap} probes have an associated semaphore variable;
5979 for instance, this happens automatically if you defined your probe
5980 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5981 @value{GDBN} will automatically enable it when you specify a
5982 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5983 breakpoint at a probe's location by some other method (e.g.,
5984 @code{break file:line}), then @value{GDBN} will not automatically set
5985 the semaphore. @code{DTrace} probes do not support semaphores.
5987 You can examine the available static static probes using @code{info
5988 probes}, with optional arguments:
5992 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5993 If given, @var{type} is either @code{stap} for listing
5994 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5995 probes. If omitted all probes are listed regardless of their types.
5997 If given, @var{provider} is a regular expression used to match against provider
5998 names when selecting which probes to list. If omitted, probes by all
5999 probes from all providers are listed.
6001 If given, @var{name} is a regular expression to match against probe names
6002 when selecting which probes to list. If omitted, probe names are not
6003 considered when deciding whether to display them.
6005 If given, @var{objfile} is a regular expression used to select which
6006 object files (executable or shared libraries) to examine. If not
6007 given, all object files are considered.
6009 @item info probes all
6010 List the available static probes, from all types.
6013 @cindex enabling and disabling probes
6014 Some probe points can be enabled and/or disabled. The effect of
6015 enabling or disabling a probe depends on the type of probe being
6016 handled. Some @code{DTrace} probes can be enabled or
6017 disabled, but @code{SystemTap} probes cannot be disabled.
6019 You can enable (or disable) one or more probes using the following
6020 commands, with optional arguments:
6023 @kindex enable probes
6024 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6025 If given, @var{provider} is a regular expression used to match against
6026 provider names when selecting which probes to enable. If omitted,
6027 all probes from all providers are enabled.
6029 If given, @var{name} is a regular expression to match against probe
6030 names when selecting which probes to enable. If omitted, probe names
6031 are not considered when deciding whether to enable them.
6033 If given, @var{objfile} is a regular expression used to select which
6034 object files (executable or shared libraries) to examine. If not
6035 given, all object files are considered.
6037 @kindex disable probes
6038 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6039 See the @code{enable probes} command above for a description of the
6040 optional arguments accepted by this command.
6043 @vindex $_probe_arg@r{, convenience variable}
6044 A probe may specify up to twelve arguments. These are available at the
6045 point at which the probe is defined---that is, when the current PC is
6046 at the probe's location. The arguments are available using the
6047 convenience variables (@pxref{Convenience Vars})
6048 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6049 probes each probe argument is an integer of the appropriate size;
6050 types are not preserved. In @code{DTrace} probes types are preserved
6051 provided that they are recognized as such by @value{GDBN}; otherwise
6052 the value of the probe argument will be a long integer. The
6053 convenience variable @code{$_probe_argc} holds the number of arguments
6054 at the current probe point.
6056 These variables are always available, but attempts to access them at
6057 any location other than a probe point will cause @value{GDBN} to give
6061 @c @ifclear BARETARGET
6062 @node Error in Breakpoints
6063 @subsection ``Cannot insert breakpoints''
6065 If you request too many active hardware-assisted breakpoints and
6066 watchpoints, you will see this error message:
6068 @c FIXME: the precise wording of this message may change; the relevant
6069 @c source change is not committed yet (Sep 3, 1999).
6071 Stopped; cannot insert breakpoints.
6072 You may have requested too many hardware breakpoints and watchpoints.
6076 This message is printed when you attempt to resume the program, since
6077 only then @value{GDBN} knows exactly how many hardware breakpoints and
6078 watchpoints it needs to insert.
6080 When this message is printed, you need to disable or remove some of the
6081 hardware-assisted breakpoints and watchpoints, and then continue.
6083 @node Breakpoint-related Warnings
6084 @subsection ``Breakpoint address adjusted...''
6085 @cindex breakpoint address adjusted
6087 Some processor architectures place constraints on the addresses at
6088 which breakpoints may be placed. For architectures thus constrained,
6089 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6090 with the constraints dictated by the architecture.
6092 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6093 a VLIW architecture in which a number of RISC-like instructions may be
6094 bundled together for parallel execution. The FR-V architecture
6095 constrains the location of a breakpoint instruction within such a
6096 bundle to the instruction with the lowest address. @value{GDBN}
6097 honors this constraint by adjusting a breakpoint's address to the
6098 first in the bundle.
6100 It is not uncommon for optimized code to have bundles which contain
6101 instructions from different source statements, thus it may happen that
6102 a breakpoint's address will be adjusted from one source statement to
6103 another. Since this adjustment may significantly alter @value{GDBN}'s
6104 breakpoint related behavior from what the user expects, a warning is
6105 printed when the breakpoint is first set and also when the breakpoint
6108 A warning like the one below is printed when setting a breakpoint
6109 that's been subject to address adjustment:
6112 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6115 Such warnings are printed both for user settable and @value{GDBN}'s
6116 internal breakpoints. If you see one of these warnings, you should
6117 verify that a breakpoint set at the adjusted address will have the
6118 desired affect. If not, the breakpoint in question may be removed and
6119 other breakpoints may be set which will have the desired behavior.
6120 E.g., it may be sufficient to place the breakpoint at a later
6121 instruction. A conditional breakpoint may also be useful in some
6122 cases to prevent the breakpoint from triggering too often.
6124 @value{GDBN} will also issue a warning when stopping at one of these
6125 adjusted breakpoints:
6128 warning: Breakpoint 1 address previously adjusted from 0x00010414
6132 When this warning is encountered, it may be too late to take remedial
6133 action except in cases where the breakpoint is hit earlier or more
6134 frequently than expected.
6136 @node Continuing and Stepping
6137 @section Continuing and Stepping
6141 @cindex resuming execution
6142 @dfn{Continuing} means resuming program execution until your program
6143 completes normally. In contrast, @dfn{stepping} means executing just
6144 one more ``step'' of your program, where ``step'' may mean either one
6145 line of source code, or one machine instruction (depending on what
6146 particular command you use). Either when continuing or when stepping,
6147 your program may stop even sooner, due to a breakpoint or a signal. (If
6148 it stops due to a signal, you may want to use @code{handle}, or use
6149 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6150 or you may step into the signal's handler (@pxref{stepping and signal
6155 @kindex c @r{(@code{continue})}
6156 @kindex fg @r{(resume foreground execution)}
6157 @item continue @r{[}@var{ignore-count}@r{]}
6158 @itemx c @r{[}@var{ignore-count}@r{]}
6159 @itemx fg @r{[}@var{ignore-count}@r{]}
6160 Resume program execution, at the address where your program last stopped;
6161 any breakpoints set at that address are bypassed. The optional argument
6162 @var{ignore-count} allows you to specify a further number of times to
6163 ignore a breakpoint at this location; its effect is like that of
6164 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6166 The argument @var{ignore-count} is meaningful only when your program
6167 stopped due to a breakpoint. At other times, the argument to
6168 @code{continue} is ignored.
6170 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6171 debugged program is deemed to be the foreground program) are provided
6172 purely for convenience, and have exactly the same behavior as
6176 To resume execution at a different place, you can use @code{return}
6177 (@pxref{Returning, ,Returning from a Function}) to go back to the
6178 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6179 Different Address}) to go to an arbitrary location in your program.
6181 A typical technique for using stepping is to set a breakpoint
6182 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6183 beginning of the function or the section of your program where a problem
6184 is believed to lie, run your program until it stops at that breakpoint,
6185 and then step through the suspect area, examining the variables that are
6186 interesting, until you see the problem happen.
6190 @kindex s @r{(@code{step})}
6192 Continue running your program until control reaches a different source
6193 line, then stop it and return control to @value{GDBN}. This command is
6194 abbreviated @code{s}.
6197 @c "without debugging information" is imprecise; actually "without line
6198 @c numbers in the debugging information". (gcc -g1 has debugging info but
6199 @c not line numbers). But it seems complex to try to make that
6200 @c distinction here.
6201 @emph{Warning:} If you use the @code{step} command while control is
6202 within a function that was compiled without debugging information,
6203 execution proceeds until control reaches a function that does have
6204 debugging information. Likewise, it will not step into a function which
6205 is compiled without debugging information. To step through functions
6206 without debugging information, use the @code{stepi} command, described
6210 The @code{step} command only stops at the first instruction of a source
6211 line. This prevents the multiple stops that could otherwise occur in
6212 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6213 to stop if a function that has debugging information is called within
6214 the line. In other words, @code{step} @emph{steps inside} any functions
6215 called within the line.
6217 Also, the @code{step} command only enters a function if there is line
6218 number information for the function. Otherwise it acts like the
6219 @code{next} command. This avoids problems when using @code{cc -gl}
6220 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6221 was any debugging information about the routine.
6223 @item step @var{count}
6224 Continue running as in @code{step}, but do so @var{count} times. If a
6225 breakpoint is reached, or a signal not related to stepping occurs before
6226 @var{count} steps, stepping stops right away.
6229 @kindex n @r{(@code{next})}
6230 @item next @r{[}@var{count}@r{]}
6231 Continue to the next source line in the current (innermost) stack frame.
6232 This is similar to @code{step}, but function calls that appear within
6233 the line of code are executed without stopping. Execution stops when
6234 control reaches a different line of code at the original stack level
6235 that was executing when you gave the @code{next} command. This command
6236 is abbreviated @code{n}.
6238 An argument @var{count} is a repeat count, as for @code{step}.
6241 @c FIX ME!! Do we delete this, or is there a way it fits in with
6242 @c the following paragraph? --- Vctoria
6244 @c @code{next} within a function that lacks debugging information acts like
6245 @c @code{step}, but any function calls appearing within the code of the
6246 @c function are executed without stopping.
6248 The @code{next} command only stops at the first instruction of a
6249 source line. This prevents multiple stops that could otherwise occur in
6250 @code{switch} statements, @code{for} loops, etc.
6252 @kindex set step-mode
6254 @cindex functions without line info, and stepping
6255 @cindex stepping into functions with no line info
6256 @itemx set step-mode on
6257 The @code{set step-mode on} command causes the @code{step} command to
6258 stop at the first instruction of a function which contains no debug line
6259 information rather than stepping over it.
6261 This is useful in cases where you may be interested in inspecting the
6262 machine instructions of a function which has no symbolic info and do not
6263 want @value{GDBN} to automatically skip over this function.
6265 @item set step-mode off
6266 Causes the @code{step} command to step over any functions which contains no
6267 debug information. This is the default.
6269 @item show step-mode
6270 Show whether @value{GDBN} will stop in or step over functions without
6271 source line debug information.
6274 @kindex fin @r{(@code{finish})}
6276 Continue running until just after function in the selected stack frame
6277 returns. Print the returned value (if any). This command can be
6278 abbreviated as @code{fin}.
6280 Contrast this with the @code{return} command (@pxref{Returning,
6281 ,Returning from a Function}).
6283 @kindex set print finish
6284 @kindex show print finish
6285 @item set print finish @r{[}on|off@r{]}
6286 @itemx show print finish
6287 By default the @code{finish} command will show the value that is
6288 returned by the function. This can be disabled using @code{set print
6289 finish off}. When disabled, the value is still entered into the value
6290 history (@pxref{Value History}), but not displayed.
6293 @kindex u @r{(@code{until})}
6294 @cindex run until specified location
6297 Continue running until a source line past the current line, in the
6298 current stack frame, is reached. This command is used to avoid single
6299 stepping through a loop more than once. It is like the @code{next}
6300 command, except that when @code{until} encounters a jump, it
6301 automatically continues execution until the program counter is greater
6302 than the address of the jump.
6304 This means that when you reach the end of a loop after single stepping
6305 though it, @code{until} makes your program continue execution until it
6306 exits the loop. In contrast, a @code{next} command at the end of a loop
6307 simply steps back to the beginning of the loop, which forces you to step
6308 through the next iteration.
6310 @code{until} always stops your program if it attempts to exit the current
6313 @code{until} may produce somewhat counterintuitive results if the order
6314 of machine code does not match the order of the source lines. For
6315 example, in the following excerpt from a debugging session, the @code{f}
6316 (@code{frame}) command shows that execution is stopped at line
6317 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6321 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6323 (@value{GDBP}) until
6324 195 for ( ; argc > 0; NEXTARG) @{
6327 This happened because, for execution efficiency, the compiler had
6328 generated code for the loop closure test at the end, rather than the
6329 start, of the loop---even though the test in a C @code{for}-loop is
6330 written before the body of the loop. The @code{until} command appeared
6331 to step back to the beginning of the loop when it advanced to this
6332 expression; however, it has not really gone to an earlier
6333 statement---not in terms of the actual machine code.
6335 @code{until} with no argument works by means of single
6336 instruction stepping, and hence is slower than @code{until} with an
6339 @item until @var{locspec}
6340 @itemx u @var{locspec}
6341 Continue running your program until either it reaches a code location
6342 that results from resolving @var{locspec}, or the current stack frame
6343 returns. @var{locspec} is any of the forms described in @ref{Location
6345 This form of the command uses temporary breakpoints, and
6346 hence is quicker than @code{until} without an argument. The specified
6347 location is actually reached only if it is in the current frame. This
6348 implies that @code{until} can be used to skip over recursive function
6349 invocations. For instance in the code below, if the current location is
6350 line @code{96}, issuing @code{until 99} will execute the program up to
6351 line @code{99} in the same invocation of factorial, i.e., after the inner
6352 invocations have returned.
6355 94 int factorial (int value)
6357 96 if (value > 1) @{
6358 97 value *= factorial (value - 1);
6365 @kindex advance @var{locspec}
6366 @item advance @var{locspec}
6367 Continue running your program until either it reaches a code location
6368 that results from resolving @var{locspec}, or the current stack frame
6369 returns. @var{locspec} is any of the forms described in @ref{Location
6370 Specifications}. This command is similar to @code{until}, but
6371 @code{advance} will not skip over recursive function calls, and the
6372 target code location doesn't have to be in the same frame as the
6377 @kindex si @r{(@code{stepi})}
6379 @itemx stepi @var{arg}
6381 Execute one machine instruction, then stop and return to the debugger.
6383 It is often useful to do @samp{display/i $pc} when stepping by machine
6384 instructions. This makes @value{GDBN} automatically display the next
6385 instruction to be executed, each time your program stops. @xref{Auto
6386 Display,, Automatic Display}.
6388 An argument is a repeat count, as in @code{step}.
6392 @kindex ni @r{(@code{nexti})}
6394 @itemx nexti @var{arg}
6396 Execute one machine instruction, but if it is a function call,
6397 proceed until the function returns.
6399 An argument is a repeat count, as in @code{next}.
6403 @anchor{range stepping}
6404 @cindex range stepping
6405 @cindex target-assisted range stepping
6406 By default, and if available, @value{GDBN} makes use of
6407 target-assisted @dfn{range stepping}. In other words, whenever you
6408 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6409 tells the target to step the corresponding range of instruction
6410 addresses instead of issuing multiple single-steps. This speeds up
6411 line stepping, particularly for remote targets. Ideally, there should
6412 be no reason you would want to turn range stepping off. However, it's
6413 possible that a bug in the debug info, a bug in the remote stub (for
6414 remote targets), or even a bug in @value{GDBN} could make line
6415 stepping behave incorrectly when target-assisted range stepping is
6416 enabled. You can use the following command to turn off range stepping
6420 @kindex set range-stepping
6421 @kindex show range-stepping
6422 @item set range-stepping
6423 @itemx show range-stepping
6424 Control whether range stepping is enabled.
6426 If @code{on}, and the target supports it, @value{GDBN} tells the
6427 target to step a range of addresses itself, instead of issuing
6428 multiple single-steps. If @code{off}, @value{GDBN} always issues
6429 single-steps, even if range stepping is supported by the target. The
6430 default is @code{on}.
6434 @node Skipping Over Functions and Files
6435 @section Skipping Over Functions and Files
6436 @cindex skipping over functions and files
6438 The program you are debugging may contain some functions which are
6439 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6440 skip a function, all functions in a file or a particular function in
6441 a particular file when stepping.
6443 For example, consider the following C function:
6454 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6455 are not interested in stepping through @code{boring}. If you run @code{step}
6456 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6457 step over both @code{foo} and @code{boring}!
6459 One solution is to @code{step} into @code{boring} and use the @code{finish}
6460 command to immediately exit it. But this can become tedious if @code{boring}
6461 is called from many places.
6463 A more flexible solution is to execute @kbd{skip boring}. This instructs
6464 @value{GDBN} never to step into @code{boring}. Now when you execute
6465 @code{step} at line 103, you'll step over @code{boring} and directly into
6468 Functions may be skipped by providing either a function name, linespec
6469 (@pxref{Location Specifications}), regular expression that matches the function's
6470 name, file name or a @code{glob}-style pattern that matches the file name.
6472 On Posix systems the form of the regular expression is
6473 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6474 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6475 expression is whatever is provided by the @code{regcomp} function of
6476 the underlying system.
6477 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6478 description of @code{glob}-style patterns.
6482 @item skip @r{[}@var{options}@r{]}
6483 The basic form of the @code{skip} command takes zero or more options
6484 that specify what to skip.
6485 The @var{options} argument is any useful combination of the following:
6488 @item -file @var{file}
6489 @itemx -fi @var{file}
6490 Functions in @var{file} will be skipped over when stepping.
6492 @item -gfile @var{file-glob-pattern}
6493 @itemx -gfi @var{file-glob-pattern}
6494 @cindex skipping over files via glob-style patterns
6495 Functions in files matching @var{file-glob-pattern} will be skipped
6499 (gdb) skip -gfi utils/*.c
6502 @item -function @var{linespec}
6503 @itemx -fu @var{linespec}
6504 Functions named by @var{linespec} or the function containing the line
6505 named by @var{linespec} will be skipped over when stepping.
6506 @xref{Location Specifications}.
6508 @item -rfunction @var{regexp}
6509 @itemx -rfu @var{regexp}
6510 @cindex skipping over functions via regular expressions
6511 Functions whose name matches @var{regexp} will be skipped over when stepping.
6513 This form is useful for complex function names.
6514 For example, there is generally no need to step into C@t{++} @code{std::string}
6515 constructors or destructors. Plus with C@t{++} templates it can be hard to
6516 write out the full name of the function, and often it doesn't matter what
6517 the template arguments are. Specifying the function to be skipped as a
6518 regular expression makes this easier.
6521 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6524 If you want to skip every templated C@t{++} constructor and destructor
6525 in the @code{std} namespace you can do:
6528 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6532 If no options are specified, the function you're currently debugging
6535 @kindex skip function
6536 @item skip function @r{[}@var{linespec}@r{]}
6537 After running this command, the function named by @var{linespec} or the
6538 function containing the line named by @var{linespec} will be skipped over when
6539 stepping. @xref{Location Specifications}.
6541 If you do not specify @var{linespec}, the function you're currently debugging
6544 (If you have a function called @code{file} that you want to skip, use
6545 @kbd{skip function file}.)
6548 @item skip file @r{[}@var{filename}@r{]}
6549 After running this command, any function whose source lives in @var{filename}
6550 will be skipped over when stepping.
6553 (gdb) skip file boring.c
6554 File boring.c will be skipped when stepping.
6557 If you do not specify @var{filename}, functions whose source lives in the file
6558 you're currently debugging will be skipped.
6561 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6562 These are the commands for managing your list of skips:
6566 @item info skip @r{[}@var{range}@r{]}
6567 Print details about the specified skip(s). If @var{range} is not specified,
6568 print a table with details about all functions and files marked for skipping.
6569 @code{info skip} prints the following information about each skip:
6573 A number identifying this skip.
6574 @item Enabled or Disabled
6575 Enabled skips are marked with @samp{y}.
6576 Disabled skips are marked with @samp{n}.
6578 If the file name is a @samp{glob} pattern this is @samp{y}.
6579 Otherwise it is @samp{n}.
6581 The name or @samp{glob} pattern of the file to be skipped.
6582 If no file is specified this is @samp{<none>}.
6584 If the function name is a @samp{regular expression} this is @samp{y}.
6585 Otherwise it is @samp{n}.
6587 The name or regular expression of the function to skip.
6588 If no function is specified this is @samp{<none>}.
6592 @item skip delete @r{[}@var{range}@r{]}
6593 Delete the specified skip(s). If @var{range} is not specified, delete all
6597 @item skip enable @r{[}@var{range}@r{]}
6598 Enable the specified skip(s). If @var{range} is not specified, enable all
6601 @kindex skip disable
6602 @item skip disable @r{[}@var{range}@r{]}
6603 Disable the specified skip(s). If @var{range} is not specified, disable all
6606 @kindex set debug skip
6607 @item set debug skip @r{[}on|off@r{]}
6608 Set whether to print the debug output about skipping files and functions.
6610 @kindex show debug skip
6611 @item show debug skip
6612 Show whether the debug output about skipping files and functions is printed.
6620 A signal is an asynchronous event that can happen in a program. The
6621 operating system defines the possible kinds of signals, and gives each
6622 kind a name and a number. For example, in Unix @code{SIGINT} is the
6623 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6624 @code{SIGSEGV} is the signal a program gets from referencing a place in
6625 memory far away from all the areas in use; @code{SIGALRM} occurs when
6626 the alarm clock timer goes off (which happens only if your program has
6627 requested an alarm).
6629 @cindex fatal signals
6630 Some signals, including @code{SIGALRM}, are a normal part of the
6631 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6632 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6633 program has not specified in advance some other way to handle the signal.
6634 @code{SIGINT} does not indicate an error in your program, but it is normally
6635 fatal so it can carry out the purpose of the interrupt: to kill the program.
6637 @value{GDBN} has the ability to detect any occurrence of a signal in your
6638 program. You can tell @value{GDBN} in advance what to do for each kind of
6641 @cindex handling signals
6642 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6643 @code{SIGALRM} be silently passed to your program
6644 (so as not to interfere with their role in the program's functioning)
6645 but to stop your program immediately whenever an error signal happens.
6646 You can change these settings with the @code{handle} command.
6649 @kindex info signals
6653 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6654 handle each one. You can use this to see the signal numbers of all
6655 the defined types of signals.
6657 @item info signals @var{sig}
6658 Similar, but print information only about the specified signal number.
6660 @code{info handle} is an alias for @code{info signals}.
6662 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6663 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6664 for details about this command.
6667 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6668 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6669 can be the number of a signal or its name (with or without the
6670 @samp{SIG} at the beginning); a list of signal numbers of the form
6671 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6672 known signals. Optional arguments @var{keywords}, described below,
6673 say what change to make.
6677 The keywords allowed by the @code{handle} command can be abbreviated.
6678 Their full names are:
6682 @value{GDBN} should not stop your program when this signal happens. It may
6683 still print a message telling you that the signal has come in.
6686 @value{GDBN} should stop your program when this signal happens. This implies
6687 the @code{print} keyword as well.
6690 @value{GDBN} should print a message when this signal happens.
6693 @value{GDBN} should not mention the occurrence of the signal at all. This
6694 implies the @code{nostop} keyword as well.
6698 @value{GDBN} should allow your program to see this signal; your program
6699 can handle the signal, or else it may terminate if the signal is fatal
6700 and not handled. @code{pass} and @code{noignore} are synonyms.
6704 @value{GDBN} should not allow your program to see this signal.
6705 @code{nopass} and @code{ignore} are synonyms.
6709 When a signal stops your program, the signal is not visible to the
6711 continue. Your program sees the signal then, if @code{pass} is in
6712 effect for the signal in question @emph{at that time}. In other words,
6713 after @value{GDBN} reports a signal, you can use the @code{handle}
6714 command with @code{pass} or @code{nopass} to control whether your
6715 program sees that signal when you continue.
6717 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6718 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6719 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6722 You can also use the @code{signal} command to prevent your program from
6723 seeing a signal, or cause it to see a signal it normally would not see,
6724 or to give it any signal at any time. For example, if your program stopped
6725 due to some sort of memory reference error, you might store correct
6726 values into the erroneous variables and continue, hoping to see more
6727 execution; but your program would probably terminate immediately as
6728 a result of the fatal signal once it saw the signal. To prevent this,
6729 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6732 @cindex stepping and signal handlers
6733 @anchor{stepping and signal handlers}
6735 @value{GDBN} optimizes for stepping the mainline code. If a signal
6736 that has @code{handle nostop} and @code{handle pass} set arrives while
6737 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6738 in progress, @value{GDBN} lets the signal handler run and then resumes
6739 stepping the mainline code once the signal handler returns. In other
6740 words, @value{GDBN} steps over the signal handler. This prevents
6741 signals that you've specified as not interesting (with @code{handle
6742 nostop}) from changing the focus of debugging unexpectedly. Note that
6743 the signal handler itself may still hit a breakpoint, stop for another
6744 signal that has @code{handle stop} in effect, or for any other event
6745 that normally results in stopping the stepping command sooner. Also
6746 note that @value{GDBN} still informs you that the program received a
6747 signal if @code{handle print} is set.
6749 @anchor{stepping into signal handlers}
6751 If you set @code{handle pass} for a signal, and your program sets up a
6752 handler for it, then issuing a stepping command, such as @code{step}
6753 or @code{stepi}, when your program is stopped due to the signal will
6754 step @emph{into} the signal handler (if the target supports that).
6756 Likewise, if you use the @code{queue-signal} command to queue a signal
6757 to be delivered to the current thread when execution of the thread
6758 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6759 stepping command will step into the signal handler.
6761 Here's an example, using @code{stepi} to step to the first instruction
6762 of @code{SIGUSR1}'s handler:
6765 (@value{GDBP}) handle SIGUSR1
6766 Signal Stop Print Pass to program Description
6767 SIGUSR1 Yes Yes Yes User defined signal 1
6771 Program received signal SIGUSR1, User defined signal 1.
6772 main () sigusr1.c:28
6775 sigusr1_handler () at sigusr1.c:9
6779 The same, but using @code{queue-signal} instead of waiting for the
6780 program to receive the signal first:
6785 (@value{GDBP}) queue-signal SIGUSR1
6787 sigusr1_handler () at sigusr1.c:9
6792 @cindex extra signal information
6793 @anchor{extra signal information}
6795 On some targets, @value{GDBN} can inspect extra signal information
6796 associated with the intercepted signal, before it is actually
6797 delivered to the program being debugged. This information is exported
6798 by the convenience variable @code{$_siginfo}, and consists of data
6799 that is passed by the kernel to the signal handler at the time of the
6800 receipt of a signal. The data type of the information itself is
6801 target dependent. You can see the data type using the @code{ptype
6802 $_siginfo} command. On Unix systems, it typically corresponds to the
6803 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6806 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6807 referenced address that raised a segmentation fault.
6811 (@value{GDBP}) continue
6812 Program received signal SIGSEGV, Segmentation fault.
6813 0x0000000000400766 in main ()
6815 (@value{GDBP}) ptype $_siginfo
6822 struct @{...@} _kill;
6823 struct @{...@} _timer;
6825 struct @{...@} _sigchld;
6826 struct @{...@} _sigfault;
6827 struct @{...@} _sigpoll;
6830 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6834 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6835 $1 = (void *) 0x7ffff7ff7000
6839 Depending on target support, @code{$_siginfo} may also be writable.
6841 @cindex Intel MPX boundary violations
6842 @cindex boundary violations, Intel MPX
6843 On some targets, a @code{SIGSEGV} can be caused by a boundary
6844 violation, i.e., accessing an address outside of the allowed range.
6845 In those cases @value{GDBN} may displays additional information,
6846 depending on how @value{GDBN} has been told to handle the signal.
6847 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6848 kind: "Upper" or "Lower", the memory address accessed and the
6849 bounds, while with @code{handle nostop SIGSEGV} no additional
6850 information is displayed.
6852 The usual output of a segfault is:
6854 Program received signal SIGSEGV, Segmentation fault
6855 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6856 68 value = *(p + len);
6859 While a bound violation is presented as:
6861 Program received signal SIGSEGV, Segmentation fault
6862 Upper bound violation while accessing address 0x7fffffffc3b3
6863 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6864 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6865 68 value = *(p + len);
6869 @section Stopping and Starting Multi-thread Programs
6871 @cindex stopped threads
6872 @cindex threads, stopped
6874 @cindex continuing threads
6875 @cindex threads, continuing
6877 @value{GDBN} supports debugging programs with multiple threads
6878 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6879 are two modes of controlling execution of your program within the
6880 debugger. In the default mode, referred to as @dfn{all-stop mode},
6881 when any thread in your program stops (for example, at a breakpoint
6882 or while being stepped), all other threads in the program are also stopped by
6883 @value{GDBN}. On some targets, @value{GDBN} also supports
6884 @dfn{non-stop mode}, in which other threads can continue to run freely while
6885 you examine the stopped thread in the debugger.
6888 * All-Stop Mode:: All threads stop when GDB takes control
6889 * Non-Stop Mode:: Other threads continue to execute
6890 * Background Execution:: Running your program asynchronously
6891 * Thread-Specific Breakpoints:: Controlling breakpoints
6892 * Interrupted System Calls:: GDB may interfere with system calls
6893 * Observer Mode:: GDB does not alter program behavior
6897 @subsection All-Stop Mode
6899 @cindex all-stop mode
6901 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6902 @emph{all} threads of execution stop, not just the current thread. This
6903 allows you to examine the overall state of the program, including
6904 switching between threads, without worrying that things may change
6907 Conversely, whenever you restart the program, @emph{all} threads start
6908 executing. @emph{This is true even when single-stepping} with commands
6909 like @code{step} or @code{next}.
6911 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6912 Since thread scheduling is up to your debugging target's operating
6913 system (not controlled by @value{GDBN}), other threads may
6914 execute more than one statement while the current thread completes a
6915 single step. Moreover, in general other threads stop in the middle of a
6916 statement, rather than at a clean statement boundary, when the program
6919 You might even find your program stopped in another thread after
6920 continuing or even single-stepping. This happens whenever some other
6921 thread runs into a breakpoint, a signal, or an exception before the
6922 first thread completes whatever you requested.
6924 @cindex automatic thread selection
6925 @cindex switching threads automatically
6926 @cindex threads, automatic switching
6927 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6928 signal, it automatically selects the thread where that breakpoint or
6929 signal happened. @value{GDBN} alerts you to the context switch with a
6930 message such as @samp{[Switching to Thread @var{n}]} to identify the
6933 On some OSes, you can modify @value{GDBN}'s default behavior by
6934 locking the OS scheduler to allow only a single thread to run.
6937 @item set scheduler-locking @var{mode}
6938 @cindex scheduler locking mode
6939 @cindex lock scheduler
6940 Set the scheduler locking mode. It applies to normal execution,
6941 record mode, and replay mode. If it is @code{off}, then there is no
6942 locking and any thread may run at any time. If @code{on}, then only
6943 the current thread may run when the inferior is resumed. The
6944 @code{step} mode optimizes for single-stepping; it prevents other
6945 threads from preempting the current thread while you are stepping, so
6946 that the focus of debugging does not change unexpectedly. Other
6947 threads never get a chance to run when you step, and they are
6948 completely free to run when you use commands like @samp{continue},
6949 @samp{until}, or @samp{finish}. However, unless another thread hits a
6950 breakpoint during its timeslice, @value{GDBN} does not change the
6951 current thread away from the thread that you are debugging. The
6952 @code{replay} mode behaves like @code{off} in record mode and like
6953 @code{on} in replay mode.
6955 @item show scheduler-locking
6956 Display the current scheduler locking mode.
6959 @cindex resume threads of multiple processes simultaneously
6960 By default, when you issue one of the execution commands such as
6961 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6962 threads of the current inferior to run. For example, if @value{GDBN}
6963 is attached to two inferiors, each with two threads, the
6964 @code{continue} command resumes only the two threads of the current
6965 inferior. This is useful, for example, when you debug a program that
6966 forks and you want to hold the parent stopped (so that, for instance,
6967 it doesn't run to exit), while you debug the child. In other
6968 situations, you may not be interested in inspecting the current state
6969 of any of the processes @value{GDBN} is attached to, and you may want
6970 to resume them all until some breakpoint is hit. In the latter case,
6971 you can instruct @value{GDBN} to allow all threads of all the
6972 inferiors to run with the @w{@code{set schedule-multiple}} command.
6975 @kindex set schedule-multiple
6976 @item set schedule-multiple
6977 Set the mode for allowing threads of multiple processes to be resumed
6978 when an execution command is issued. When @code{on}, all threads of
6979 all processes are allowed to run. When @code{off}, only the threads
6980 of the current process are resumed. The default is @code{off}. The
6981 @code{scheduler-locking} mode takes precedence when set to @code{on},
6982 or while you are stepping and set to @code{step}.
6984 @item show schedule-multiple
6985 Display the current mode for resuming the execution of threads of
6990 @subsection Non-Stop Mode
6992 @cindex non-stop mode
6994 @c This section is really only a place-holder, and needs to be expanded
6995 @c with more details.
6997 For some multi-threaded targets, @value{GDBN} supports an optional
6998 mode of operation in which you can examine stopped program threads in
6999 the debugger while other threads continue to execute freely. This
7000 minimizes intrusion when debugging live systems, such as programs
7001 where some threads have real-time constraints or must continue to
7002 respond to external events. This is referred to as @dfn{non-stop} mode.
7004 In non-stop mode, when a thread stops to report a debugging event,
7005 @emph{only} that thread is stopped; @value{GDBN} does not stop other
7006 threads as well, in contrast to the all-stop mode behavior. Additionally,
7007 execution commands such as @code{continue} and @code{step} apply by default
7008 only to the current thread in non-stop mode, rather than all threads as
7009 in all-stop mode. This allows you to control threads explicitly in
7010 ways that are not possible in all-stop mode --- for example, stepping
7011 one thread while allowing others to run freely, stepping
7012 one thread while holding all others stopped, or stepping several threads
7013 independently and simultaneously.
7015 To enter non-stop mode, use this sequence of commands before you run
7016 or attach to your program:
7019 # If using the CLI, pagination breaks non-stop.
7022 # Finally, turn it on!
7026 You can use these commands to manipulate the non-stop mode setting:
7029 @kindex set non-stop
7030 @item set non-stop on
7031 Enable selection of non-stop mode.
7032 @item set non-stop off
7033 Disable selection of non-stop mode.
7034 @kindex show non-stop
7036 Show the current non-stop enablement setting.
7039 Note these commands only reflect whether non-stop mode is enabled,
7040 not whether the currently-executing program is being run in non-stop mode.
7041 In particular, the @code{set non-stop} preference is only consulted when
7042 @value{GDBN} starts or connects to the target program, and it is generally
7043 not possible to switch modes once debugging has started. Furthermore,
7044 since not all targets support non-stop mode, even when you have enabled
7045 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7048 In non-stop mode, all execution commands apply only to the current thread
7049 by default. That is, @code{continue} only continues one thread.
7050 To continue all threads, issue @code{continue -a} or @code{c -a}.
7052 You can use @value{GDBN}'s background execution commands
7053 (@pxref{Background Execution}) to run some threads in the background
7054 while you continue to examine or step others from @value{GDBN}.
7055 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7056 always executed asynchronously in non-stop mode.
7058 Suspending execution is done with the @code{interrupt} command when
7059 running in the background, or @kbd{Ctrl-c} during foreground execution.
7060 In all-stop mode, this stops the whole process;
7061 but in non-stop mode the interrupt applies only to the current thread.
7062 To stop the whole program, use @code{interrupt -a}.
7064 Other execution commands do not currently support the @code{-a} option.
7066 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7067 that thread current, as it does in all-stop mode. This is because the
7068 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7069 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7070 changed to a different thread just as you entered a command to operate on the
7071 previously current thread.
7073 @node Background Execution
7074 @subsection Background Execution
7076 @cindex foreground execution
7077 @cindex background execution
7078 @cindex asynchronous execution
7079 @cindex execution, foreground, background and asynchronous
7081 @value{GDBN}'s execution commands have two variants: the normal
7082 foreground (synchronous) behavior, and a background
7083 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7084 the program to report that some thread has stopped before prompting for
7085 another command. In background execution, @value{GDBN} immediately gives
7086 a command prompt so that you can issue other commands while your program runs.
7088 If the target doesn't support async mode, @value{GDBN} issues an error
7089 message if you attempt to use the background execution commands.
7091 @cindex @code{&}, background execution of commands
7092 To specify background execution, add a @code{&} to the command. For example,
7093 the background form of the @code{continue} command is @code{continue&}, or
7094 just @code{c&}. The execution commands that accept background execution
7100 @xref{Starting, , Starting your Program}.
7104 @xref{Attach, , Debugging an Already-running Process}.
7108 @xref{Continuing and Stepping, step}.
7112 @xref{Continuing and Stepping, stepi}.
7116 @xref{Continuing and Stepping, next}.
7120 @xref{Continuing and Stepping, nexti}.
7124 @xref{Continuing and Stepping, continue}.
7128 @xref{Continuing and Stepping, finish}.
7132 @xref{Continuing and Stepping, until}.
7136 Background execution is especially useful in conjunction with non-stop
7137 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7138 However, you can also use these commands in the normal all-stop mode with
7139 the restriction that you cannot issue another execution command until the
7140 previous one finishes. Examples of commands that are valid in all-stop
7141 mode while the program is running include @code{help} and @code{info break}.
7143 You can interrupt your program while it is running in the background by
7144 using the @code{interrupt} command.
7151 Suspend execution of the running program. In all-stop mode,
7152 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7153 only the current thread. To stop the whole program in non-stop mode,
7154 use @code{interrupt -a}.
7157 @node Thread-Specific Breakpoints
7158 @subsection Thread-Specific Breakpoints
7160 When your program has multiple threads (@pxref{Threads,, Debugging
7161 Programs with Multiple Threads}), you can choose whether to set
7162 breakpoints on all threads, or on a particular thread.
7165 @cindex breakpoints and threads
7166 @cindex thread breakpoints
7167 @kindex break @dots{} thread @var{thread-id}
7168 @item break @var{locspec} thread @var{thread-id}
7169 @itemx break @var{locspec} thread @var{thread-id} if @dots{}
7170 @var{locspec} specifies a code location or locations in your program.
7171 @xref{Location Specifications}, for details.
7173 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7174 to specify that you only want @value{GDBN} to stop the program when a
7175 particular thread reaches this breakpoint. The @var{thread-id} specifier
7176 is one of the thread identifiers assigned by @value{GDBN}, shown
7177 in the first column of the @samp{info threads} display.
7179 If you do not specify @samp{thread @var{thread-id}} when you set a
7180 breakpoint, the breakpoint applies to @emph{all} threads of your
7183 You can use the @code{thread} qualifier on conditional breakpoints as
7184 well; in this case, place @samp{thread @var{thread-id}} before or
7185 after the breakpoint condition, like this:
7188 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7193 Thread-specific breakpoints are automatically deleted when
7194 @value{GDBN} detects the corresponding thread is no longer in the
7195 thread list. For example:
7199 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7202 There are several ways for a thread to disappear, such as a regular
7203 thread exit, but also when you detach from the process with the
7204 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7205 Process}), or if @value{GDBN} loses the remote connection
7206 (@pxref{Remote Debugging}), etc. Note that with some targets,
7207 @value{GDBN} is only able to detect a thread has exited when the user
7208 explictly asks for the thread list with the @code{info threads}
7211 @node Interrupted System Calls
7212 @subsection Interrupted System Calls
7214 @cindex thread breakpoints and system calls
7215 @cindex system calls and thread breakpoints
7216 @cindex premature return from system calls
7217 There is an unfortunate side effect when using @value{GDBN} to debug
7218 multi-threaded programs. If one thread stops for a
7219 breakpoint, or for some other reason, and another thread is blocked in a
7220 system call, then the system call may return prematurely. This is a
7221 consequence of the interaction between multiple threads and the signals
7222 that @value{GDBN} uses to implement breakpoints and other events that
7225 To handle this problem, your program should check the return value of
7226 each system call and react appropriately. This is good programming
7229 For example, do not write code like this:
7235 The call to @code{sleep} will return early if a different thread stops
7236 at a breakpoint or for some other reason.
7238 Instead, write this:
7243 unslept = sleep (unslept);
7246 A system call is allowed to return early, so the system is still
7247 conforming to its specification. But @value{GDBN} does cause your
7248 multi-threaded program to behave differently than it would without
7251 Also, @value{GDBN} uses internal breakpoints in the thread library to
7252 monitor certain events such as thread creation and thread destruction.
7253 When such an event happens, a system call in another thread may return
7254 prematurely, even though your program does not appear to stop.
7257 @subsection Observer Mode
7259 If you want to build on non-stop mode and observe program behavior
7260 without any chance of disruption by @value{GDBN}, you can set
7261 variables to disable all of the debugger's attempts to modify state,
7262 whether by writing memory, inserting breakpoints, etc. These operate
7263 at a low level, intercepting operations from all commands.
7265 When all of these are set to @code{off}, then @value{GDBN} is said to
7266 be @dfn{observer mode}. As a convenience, the variable
7267 @code{observer} can be set to disable these, plus enable non-stop
7270 Note that @value{GDBN} will not prevent you from making nonsensical
7271 combinations of these settings. For instance, if you have enabled
7272 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7273 then breakpoints that work by writing trap instructions into the code
7274 stream will still not be able to be placed.
7279 @item set observer on
7280 @itemx set observer off
7281 When set to @code{on}, this disables all the permission variables
7282 below (except for @code{insert-fast-tracepoints}), plus enables
7283 non-stop debugging. Setting this to @code{off} switches back to
7284 normal debugging, though remaining in non-stop mode.
7287 Show whether observer mode is on or off.
7289 @kindex may-write-registers
7290 @item set may-write-registers on
7291 @itemx set may-write-registers off
7292 This controls whether @value{GDBN} will attempt to alter the values of
7293 registers, such as with assignment expressions in @code{print}, or the
7294 @code{jump} command. It defaults to @code{on}.
7296 @item show may-write-registers
7297 Show the current permission to write registers.
7299 @kindex may-write-memory
7300 @item set may-write-memory on
7301 @itemx set may-write-memory off
7302 This controls whether @value{GDBN} will attempt to alter the contents
7303 of memory, such as with assignment expressions in @code{print}. It
7304 defaults to @code{on}.
7306 @item show may-write-memory
7307 Show the current permission to write memory.
7309 @kindex may-insert-breakpoints
7310 @item set may-insert-breakpoints on
7311 @itemx set may-insert-breakpoints off
7312 This controls whether @value{GDBN} will attempt to insert breakpoints.
7313 This affects all breakpoints, including internal breakpoints defined
7314 by @value{GDBN}. It defaults to @code{on}.
7316 @item show may-insert-breakpoints
7317 Show the current permission to insert breakpoints.
7319 @kindex may-insert-tracepoints
7320 @item set may-insert-tracepoints on
7321 @itemx set may-insert-tracepoints off
7322 This controls whether @value{GDBN} will attempt to insert (regular)
7323 tracepoints at the beginning of a tracing experiment. It affects only
7324 non-fast tracepoints, fast tracepoints being under the control of
7325 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7327 @item show may-insert-tracepoints
7328 Show the current permission to insert tracepoints.
7330 @kindex may-insert-fast-tracepoints
7331 @item set may-insert-fast-tracepoints on
7332 @itemx set may-insert-fast-tracepoints off
7333 This controls whether @value{GDBN} will attempt to insert fast
7334 tracepoints at the beginning of a tracing experiment. It affects only
7335 fast tracepoints, regular (non-fast) tracepoints being under the
7336 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7338 @item show may-insert-fast-tracepoints
7339 Show the current permission to insert fast tracepoints.
7341 @kindex may-interrupt
7342 @item set may-interrupt on
7343 @itemx set may-interrupt off
7344 This controls whether @value{GDBN} will attempt to interrupt or stop
7345 program execution. When this variable is @code{off}, the
7346 @code{interrupt} command will have no effect, nor will
7347 @kbd{Ctrl-c}. It defaults to @code{on}.
7349 @item show may-interrupt
7350 Show the current permission to interrupt or stop the program.
7354 @node Reverse Execution
7355 @chapter Running programs backward
7356 @cindex reverse execution
7357 @cindex running programs backward
7359 When you are debugging a program, it is not unusual to realize that
7360 you have gone too far, and some event of interest has already happened.
7361 If the target environment supports it, @value{GDBN} can allow you to
7362 ``rewind'' the program by running it backward.
7364 A target environment that supports reverse execution should be able
7365 to ``undo'' the changes in machine state that have taken place as the
7366 program was executing normally. Variables, registers etc.@: should
7367 revert to their previous values. Obviously this requires a great
7368 deal of sophistication on the part of the target environment; not
7369 all target environments can support reverse execution.
7371 When a program is executed in reverse, the instructions that
7372 have most recently been executed are ``un-executed'', in reverse
7373 order. The program counter runs backward, following the previous
7374 thread of execution in reverse. As each instruction is ``un-executed'',
7375 the values of memory and/or registers that were changed by that
7376 instruction are reverted to their previous states. After executing
7377 a piece of source code in reverse, all side effects of that code
7378 should be ``undone'', and all variables should be returned to their
7379 prior values@footnote{
7380 Note that some side effects are easier to undo than others. For instance,
7381 memory and registers are relatively easy, but device I/O is hard. Some
7382 targets may be able undo things like device I/O, and some may not.
7384 The contract between @value{GDBN} and the reverse executing target
7385 requires only that the target do something reasonable when
7386 @value{GDBN} tells it to execute backwards, and then report the
7387 results back to @value{GDBN}. Whatever the target reports back to
7388 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7389 assumes that the memory and registers that the target reports are in a
7390 consistent state, but @value{GDBN} accepts whatever it is given.
7393 On some platforms, @value{GDBN} has built-in support for reverse
7394 execution, activated with the @code{record} or @code{record btrace}
7395 commands. @xref{Process Record and Replay}. Some remote targets,
7396 typically full system emulators, support reverse execution directly
7397 without requiring any special command.
7399 If you are debugging in a target environment that supports
7400 reverse execution, @value{GDBN} provides the following commands.
7403 @kindex reverse-continue
7404 @kindex rc @r{(@code{reverse-continue})}
7405 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7406 @itemx rc @r{[}@var{ignore-count}@r{]}
7407 Beginning at the point where your program last stopped, start executing
7408 in reverse. Reverse execution will stop for breakpoints and synchronous
7409 exceptions (signals), just like normal execution. Behavior of
7410 asynchronous signals depends on the target environment.
7412 @kindex reverse-step
7413 @kindex rs @r{(@code{step})}
7414 @item reverse-step @r{[}@var{count}@r{]}
7415 Run the program backward until control reaches the start of a
7416 different source line; then stop it, and return control to @value{GDBN}.
7418 Like the @code{step} command, @code{reverse-step} will only stop
7419 at the beginning of a source line. It ``un-executes'' the previously
7420 executed source line. If the previous source line included calls to
7421 debuggable functions, @code{reverse-step} will step (backward) into
7422 the called function, stopping at the beginning of the @emph{last}
7423 statement in the called function (typically a return statement).
7425 Also, as with the @code{step} command, if non-debuggable functions are
7426 called, @code{reverse-step} will run thru them backward without stopping.
7428 @kindex reverse-stepi
7429 @kindex rsi @r{(@code{reverse-stepi})}
7430 @item reverse-stepi @r{[}@var{count}@r{]}
7431 Reverse-execute one machine instruction. Note that the instruction
7432 to be reverse-executed is @emph{not} the one pointed to by the program
7433 counter, but the instruction executed prior to that one. For instance,
7434 if the last instruction was a jump, @code{reverse-stepi} will take you
7435 back from the destination of the jump to the jump instruction itself.
7437 @kindex reverse-next
7438 @kindex rn @r{(@code{reverse-next})}
7439 @item reverse-next @r{[}@var{count}@r{]}
7440 Run backward to the beginning of the previous line executed in
7441 the current (innermost) stack frame. If the line contains function
7442 calls, they will be ``un-executed'' without stopping. Starting from
7443 the first line of a function, @code{reverse-next} will take you back
7444 to the caller of that function, @emph{before} the function was called,
7445 just as the normal @code{next} command would take you from the last
7446 line of a function back to its return to its caller
7447 @footnote{Unless the code is too heavily optimized.}.
7449 @kindex reverse-nexti
7450 @kindex rni @r{(@code{reverse-nexti})}
7451 @item reverse-nexti @r{[}@var{count}@r{]}
7452 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7453 in reverse, except that called functions are ``un-executed'' atomically.
7454 That is, if the previously executed instruction was a return from
7455 another function, @code{reverse-nexti} will continue to execute
7456 in reverse until the call to that function (from the current stack
7459 @kindex reverse-finish
7460 @item reverse-finish
7461 Just as the @code{finish} command takes you to the point where the
7462 current function returns, @code{reverse-finish} takes you to the point
7463 where it was called. Instead of ending up at the end of the current
7464 function invocation, you end up at the beginning.
7466 @kindex set exec-direction
7467 @item set exec-direction
7468 Set the direction of target execution.
7469 @item set exec-direction reverse
7470 @cindex execute forward or backward in time
7471 @value{GDBN} will perform all execution commands in reverse, until the
7472 exec-direction mode is changed to ``forward''. Affected commands include
7473 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7474 command cannot be used in reverse mode.
7475 @item set exec-direction forward
7476 @value{GDBN} will perform all execution commands in the normal fashion.
7477 This is the default.
7481 @node Process Record and Replay
7482 @chapter Recording Inferior's Execution and Replaying It
7483 @cindex process record and replay
7484 @cindex recording inferior's execution and replaying it
7486 On some platforms, @value{GDBN} provides a special @dfn{process record
7487 and replay} target that can record a log of the process execution, and
7488 replay it later with both forward and reverse execution commands.
7491 When this target is in use, if the execution log includes the record
7492 for the next instruction, @value{GDBN} will debug in @dfn{replay
7493 mode}. In the replay mode, the inferior does not really execute code
7494 instructions. Instead, all the events that normally happen during
7495 code execution are taken from the execution log. While code is not
7496 really executed in replay mode, the values of registers (including the
7497 program counter register) and the memory of the inferior are still
7498 changed as they normally would. Their contents are taken from the
7502 If the record for the next instruction is not in the execution log,
7503 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7504 inferior executes normally, and @value{GDBN} records the execution log
7507 The process record and replay target supports reverse execution
7508 (@pxref{Reverse Execution}), even if the platform on which the
7509 inferior runs does not. However, the reverse execution is limited in
7510 this case by the range of the instructions recorded in the execution
7511 log. In other words, reverse execution on platforms that don't
7512 support it directly can only be done in the replay mode.
7514 When debugging in the reverse direction, @value{GDBN} will work in
7515 replay mode as long as the execution log includes the record for the
7516 previous instruction; otherwise, it will work in record mode, if the
7517 platform supports reverse execution, or stop if not.
7519 Currently, process record and replay is supported on ARM, Aarch64,
7520 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7521 GNU/Linux. Process record and replay can be used both when native
7522 debugging, and when remote debugging via @code{gdbserver}.
7524 For architecture environments that support process record and replay,
7525 @value{GDBN} provides the following commands:
7528 @kindex target record
7529 @kindex target record-full
7530 @kindex target record-btrace
7533 @kindex record btrace
7534 @kindex record btrace bts
7535 @kindex record btrace pt
7541 @kindex rec btrace bts
7542 @kindex rec btrace pt
7545 @item record @var{method}
7546 This command starts the process record and replay target. The
7547 recording method can be specified as parameter. Without a parameter
7548 the command uses the @code{full} recording method. The following
7549 recording methods are available:
7553 Full record/replay recording using @value{GDBN}'s software record and
7554 replay implementation. This method allows replaying and reverse
7557 @item btrace @var{format}
7558 Hardware-supported instruction recording, supported on Intel
7559 processors. This method does not record data. Further, the data is
7560 collected in a ring buffer so old data will be overwritten when the
7561 buffer is full. It allows limited reverse execution. Variables and
7562 registers are not available during reverse execution. In remote
7563 debugging, recording continues on disconnect. Recorded data can be
7564 inspected after reconnecting. The recording may be stopped using
7567 The recording format can be specified as parameter. Without a parameter
7568 the command chooses the recording format. The following recording
7569 formats are available:
7573 @cindex branch trace store
7574 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7575 this format, the processor stores a from/to record for each executed
7576 branch in the btrace ring buffer.
7579 @cindex Intel Processor Trace
7580 Use the @dfn{Intel Processor Trace} recording format. In this
7581 format, the processor stores the execution trace in a compressed form
7582 that is afterwards decoded by @value{GDBN}.
7584 The trace can be recorded with very low overhead. The compressed
7585 trace format also allows small trace buffers to already contain a big
7586 number of instructions compared to @acronym{BTS}.
7588 Decoding the recorded execution trace, on the other hand, is more
7589 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7590 increased number of instructions to process. You should increase the
7591 buffer-size with care.
7594 Not all recording formats may be available on all processors.
7597 The process record and replay target can only debug a process that is
7598 already running. Therefore, you need first to start the process with
7599 the @kbd{run} or @kbd{start} commands, and then start the recording
7600 with the @kbd{record @var{method}} command.
7602 @cindex displaced stepping, and process record and replay
7603 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7604 will be automatically disabled when process record and replay target
7605 is started. That's because the process record and replay target
7606 doesn't support displaced stepping.
7608 @cindex non-stop mode, and process record and replay
7609 @cindex asynchronous execution, and process record and replay
7610 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7611 the asynchronous execution mode (@pxref{Background Execution}), not
7612 all recording methods are available. The @code{full} recording method
7613 does not support these two modes.
7618 Stop the process record and replay target. When process record and
7619 replay target stops, the entire execution log will be deleted and the
7620 inferior will either be terminated, or will remain in its final state.
7622 When you stop the process record and replay target in record mode (at
7623 the end of the execution log), the inferior will be stopped at the
7624 next instruction that would have been recorded. In other words, if
7625 you record for a while and then stop recording, the inferior process
7626 will be left in the same state as if the recording never happened.
7628 On the other hand, if the process record and replay target is stopped
7629 while in replay mode (that is, not at the end of the execution log,
7630 but at some earlier point), the inferior process will become ``live''
7631 at that earlier state, and it will then be possible to continue the
7632 usual ``live'' debugging of the process from that state.
7634 When the inferior process exits, or @value{GDBN} detaches from it,
7635 process record and replay target will automatically stop itself.
7639 Go to a specific location in the execution log. There are several
7640 ways to specify the location to go to:
7643 @item record goto begin
7644 @itemx record goto start
7645 Go to the beginning of the execution log.
7647 @item record goto end
7648 Go to the end of the execution log.
7650 @item record goto @var{n}
7651 Go to instruction number @var{n} in the execution log.
7655 @item record save @var{filename}
7656 Save the execution log to a file @file{@var{filename}}.
7657 Default filename is @file{gdb_record.@var{process_id}}, where
7658 @var{process_id} is the process ID of the inferior.
7660 This command may not be available for all recording methods.
7662 @kindex record restore
7663 @item record restore @var{filename}
7664 Restore the execution log from a file @file{@var{filename}}.
7665 File must have been created with @code{record save}.
7667 @kindex set record full
7668 @item set record full insn-number-max @var{limit}
7669 @itemx set record full insn-number-max unlimited
7670 Set the limit of instructions to be recorded for the @code{full}
7671 recording method. Default value is 200000.
7673 If @var{limit} is a positive number, then @value{GDBN} will start
7674 deleting instructions from the log once the number of the record
7675 instructions becomes greater than @var{limit}. For every new recorded
7676 instruction, @value{GDBN} will delete the earliest recorded
7677 instruction to keep the number of recorded instructions at the limit.
7678 (Since deleting recorded instructions loses information, @value{GDBN}
7679 lets you control what happens when the limit is reached, by means of
7680 the @code{stop-at-limit} option, described below.)
7682 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7683 delete recorded instructions from the execution log. The number of
7684 recorded instructions is limited only by the available memory.
7686 @kindex show record full
7687 @item show record full insn-number-max
7688 Show the limit of instructions to be recorded with the @code{full}
7691 @item set record full stop-at-limit
7692 Control the behavior of the @code{full} recording method when the
7693 number of recorded instructions reaches the limit. If ON (the
7694 default), @value{GDBN} will stop when the limit is reached for the
7695 first time and ask you whether you want to stop the inferior or
7696 continue running it and recording the execution log. If you decide
7697 to continue recording, each new recorded instruction will cause the
7698 oldest one to be deleted.
7700 If this option is OFF, @value{GDBN} will automatically delete the
7701 oldest record to make room for each new one, without asking.
7703 @item show record full stop-at-limit
7704 Show the current setting of @code{stop-at-limit}.
7706 @item set record full memory-query
7707 Control the behavior when @value{GDBN} is unable to record memory
7708 changes caused by an instruction for the @code{full} recording method.
7709 If ON, @value{GDBN} will query whether to stop the inferior in that
7712 If this option is OFF (the default), @value{GDBN} will automatically
7713 ignore the effect of such instructions on memory. Later, when
7714 @value{GDBN} replays this execution log, it will mark the log of this
7715 instruction as not accessible, and it will not affect the replay
7718 @item show record full memory-query
7719 Show the current setting of @code{memory-query}.
7721 @kindex set record btrace
7722 The @code{btrace} record target does not trace data. As a
7723 convenience, when replaying, @value{GDBN} reads read-only memory off
7724 the live program directly, assuming that the addresses of the
7725 read-only areas don't change. This for example makes it possible to
7726 disassemble code while replaying, but not to print variables.
7727 In some cases, being able to inspect variables might be useful.
7728 You can use the following command for that:
7730 @item set record btrace replay-memory-access
7731 Control the behavior of the @code{btrace} recording method when
7732 accessing memory during replay. If @code{read-only} (the default),
7733 @value{GDBN} will only allow accesses to read-only memory.
7734 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7735 and to read-write memory. Beware that the accessed memory corresponds
7736 to the live target and not necessarily to the current replay
7739 @item set record btrace cpu @var{identifier}
7740 Set the processor to be used for enabling workarounds for processor
7741 errata when decoding the trace.
7743 Processor errata are defects in processor operation, caused by its
7744 design or manufacture. They can cause a trace not to match the
7745 specification. This, in turn, may cause trace decode to fail.
7746 @value{GDBN} can detect erroneous trace packets and correct them, thus
7747 avoiding the decoding failures. These corrections are known as
7748 @dfn{errata workarounds}, and are enabled based on the processor on
7749 which the trace was recorded.
7751 By default, @value{GDBN} attempts to detect the processor
7752 automatically, and apply the necessary workarounds for it. However,
7753 you may need to specify the processor if @value{GDBN} does not yet
7754 support it. This command allows you to do that, and also allows to
7755 disable the workarounds.
7757 The argument @var{identifier} identifies the @sc{cpu} and is of the
7758 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7759 there are two special identifiers, @code{none} and @code{auto}
7762 The following vendor identifiers and corresponding processor
7763 identifiers are currently supported:
7765 @multitable @columnfractions .1 .9
7768 @tab @var{family}/@var{model}[/@var{stepping}]
7772 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7773 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7775 If @var{identifier} is @code{auto}, enable errata workarounds for the
7776 processor on which the trace was recorded. If @var{identifier} is
7777 @code{none}, errata workarounds are disabled.
7779 For example, when using an old @value{GDBN} on a new system, decode
7780 may fail because @value{GDBN} does not support the new processor. It
7781 often suffices to specify an older processor that @value{GDBN}
7786 Active record target: record-btrace
7787 Recording format: Intel Processor Trace.
7789 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7790 (gdb) set record btrace cpu intel:6/158
7792 Active record target: record-btrace
7793 Recording format: Intel Processor Trace.
7795 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7798 @kindex show record btrace
7799 @item show record btrace replay-memory-access
7800 Show the current setting of @code{replay-memory-access}.
7802 @item show record btrace cpu
7803 Show the processor to be used for enabling trace decode errata
7806 @kindex set record btrace bts
7807 @item set record btrace bts buffer-size @var{size}
7808 @itemx set record btrace bts buffer-size unlimited
7809 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7810 format. Default is 64KB.
7812 If @var{size} is a positive number, then @value{GDBN} will try to
7813 allocate a buffer of at least @var{size} bytes for each new thread
7814 that uses the btrace recording method and the @acronym{BTS} format.
7815 The actually obtained buffer size may differ from the requested
7816 @var{size}. Use the @code{info record} command to see the actual
7817 buffer size for each thread that uses the btrace recording method and
7818 the @acronym{BTS} format.
7820 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7821 allocate a buffer of 4MB.
7823 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7824 also need longer to process the branch trace data before it can be used.
7826 @item show record btrace bts buffer-size @var{size}
7827 Show the current setting of the requested ring buffer size for branch
7828 tracing in @acronym{BTS} format.
7830 @kindex set record btrace pt
7831 @item set record btrace pt buffer-size @var{size}
7832 @itemx set record btrace pt buffer-size unlimited
7833 Set the requested ring buffer size for branch tracing in Intel
7834 Processor Trace format. Default is 16KB.
7836 If @var{size} is a positive number, then @value{GDBN} will try to
7837 allocate a buffer of at least @var{size} bytes for each new thread
7838 that uses the btrace recording method and the Intel Processor Trace
7839 format. The actually obtained buffer size may differ from the
7840 requested @var{size}. Use the @code{info record} command to see the
7841 actual buffer size for each thread.
7843 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7844 allocate a buffer of 4MB.
7846 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7847 also need longer to process the branch trace data before it can be used.
7849 @item show record btrace pt buffer-size @var{size}
7850 Show the current setting of the requested ring buffer size for branch
7851 tracing in Intel Processor Trace format.
7855 Show various statistics about the recording depending on the recording
7860 For the @code{full} recording method, it shows the state of process
7861 record and its in-memory execution log buffer, including:
7865 Whether in record mode or replay mode.
7867 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7869 Highest recorded instruction number.
7871 Current instruction about to be replayed (if in replay mode).
7873 Number of instructions contained in the execution log.
7875 Maximum number of instructions that may be contained in the execution log.
7879 For the @code{btrace} recording method, it shows:
7885 Number of instructions that have been recorded.
7887 Number of blocks of sequential control-flow formed by the recorded
7890 Whether in record mode or replay mode.
7893 For the @code{bts} recording format, it also shows:
7896 Size of the perf ring buffer.
7899 For the @code{pt} recording format, it also shows:
7902 Size of the perf ring buffer.
7906 @kindex record delete
7909 When record target runs in replay mode (``in the past''), delete the
7910 subsequent execution log and begin to record a new execution log starting
7911 from the current address. This means you will abandon the previously
7912 recorded ``future'' and begin recording a new ``future''.
7914 @kindex record instruction-history
7915 @kindex rec instruction-history
7916 @item record instruction-history
7917 Disassembles instructions from the recorded execution log. By
7918 default, ten instructions are disassembled. This can be changed using
7919 the @code{set record instruction-history-size} command. Instructions
7920 are printed in execution order.
7922 It can also print mixed source+disassembly if you specify the the
7923 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7924 as well as in symbolic form by specifying the @code{/r} modifier.
7926 The current position marker is printed for the instruction at the
7927 current program counter value. This instruction can appear multiple
7928 times in the trace and the current position marker will be printed
7929 every time. To omit the current position marker, specify the
7932 To better align the printed instructions when the trace contains
7933 instructions from more than one function, the function name may be
7934 omitted by specifying the @code{/f} modifier.
7936 Speculatively executed instructions are prefixed with @samp{?}. This
7937 feature is not available for all recording formats.
7939 There are several ways to specify what part of the execution log to
7943 @item record instruction-history @var{insn}
7944 Disassembles ten instructions starting from instruction number
7947 @item record instruction-history @var{insn}, +/-@var{n}
7948 Disassembles @var{n} instructions around instruction number
7949 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7950 @var{n} instructions after instruction number @var{insn}. If
7951 @var{n} is preceded with @code{-}, disassembles @var{n}
7952 instructions before instruction number @var{insn}.
7954 @item record instruction-history
7955 Disassembles ten more instructions after the last disassembly.
7957 @item record instruction-history -
7958 Disassembles ten more instructions before the last disassembly.
7960 @item record instruction-history @var{begin}, @var{end}
7961 Disassembles instructions beginning with instruction number
7962 @var{begin} until instruction number @var{end}. The instruction
7963 number @var{end} is included.
7966 This command may not be available for all recording methods.
7969 @item set record instruction-history-size @var{size}
7970 @itemx set record instruction-history-size unlimited
7971 Define how many instructions to disassemble in the @code{record
7972 instruction-history} command. The default value is 10.
7973 A @var{size} of @code{unlimited} means unlimited instructions.
7976 @item show record instruction-history-size
7977 Show how many instructions to disassemble in the @code{record
7978 instruction-history} command.
7980 @kindex record function-call-history
7981 @kindex rec function-call-history
7982 @item record function-call-history
7983 Prints the execution history at function granularity. For each sequence
7984 of instructions that belong to the same function, it prints the name of
7985 that function, the source lines for this instruction sequence (if the
7986 @code{/l} modifier is specified), and the instructions numbers that form
7987 the sequence (if the @code{/i} modifier is specified). The function names
7988 are indented to reflect the call stack depth if the @code{/c} modifier is
7989 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
7993 (@value{GDBP}) @b{list 1, 10}
8004 (@value{GDBP}) @b{record function-call-history /ilc}
8005 1 bar inst 1,4 at foo.c:6,8
8006 2 foo inst 5,10 at foo.c:2,3
8007 3 bar inst 11,13 at foo.c:9,10
8010 By default, ten functions are printed. This can be changed using the
8011 @code{set record function-call-history-size} command. Functions are
8012 printed in execution order. There are several ways to specify what
8016 @item record function-call-history @var{func}
8017 Prints ten functions starting from function number @var{func}.
8019 @item record function-call-history @var{func}, +/-@var{n}
8020 Prints @var{n} functions around function number @var{func}. If
8021 @var{n} is preceded with @code{+}, prints @var{n} functions after
8022 function number @var{func}. If @var{n} is preceded with @code{-},
8023 prints @var{n} functions before function number @var{func}.
8025 @item record function-call-history
8026 Prints ten more functions after the last ten-function print.
8028 @item record function-call-history -
8029 Prints ten more functions before the last ten-function print.
8031 @item record function-call-history @var{begin}, @var{end}
8032 Prints functions beginning with function number @var{begin} until
8033 function number @var{end}. The function number @var{end} is included.
8036 This command may not be available for all recording methods.
8038 @item set record function-call-history-size @var{size}
8039 @itemx set record function-call-history-size unlimited
8040 Define how many functions to print in the
8041 @code{record function-call-history} command. The default value is 10.
8042 A size of @code{unlimited} means unlimited functions.
8044 @item show record function-call-history-size
8045 Show how many functions to print in the
8046 @code{record function-call-history} command.
8051 @chapter Examining the Stack
8053 When your program has stopped, the first thing you need to know is where it
8054 stopped and how it got there.
8057 Each time your program performs a function call, information about the call
8059 That information includes the location of the call in your program,
8060 the arguments of the call,
8061 and the local variables of the function being called.
8062 The information is saved in a block of data called a @dfn{stack frame}.
8063 The stack frames are allocated in a region of memory called the @dfn{call
8066 When your program stops, the @value{GDBN} commands for examining the
8067 stack allow you to see all of this information.
8069 @cindex selected frame
8070 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8071 @value{GDBN} commands refer implicitly to the selected frame. In
8072 particular, whenever you ask @value{GDBN} for the value of a variable in
8073 your program, the value is found in the selected frame. There are
8074 special @value{GDBN} commands to select whichever frame you are
8075 interested in. @xref{Selection, ,Selecting a Frame}.
8077 When your program stops, @value{GDBN} automatically selects the
8078 currently executing frame and describes it briefly, similar to the
8079 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8082 * Frames:: Stack frames
8083 * Backtrace:: Backtraces
8084 * Selection:: Selecting a frame
8085 * Frame Info:: Information on a frame
8086 * Frame Apply:: Applying a command to several frames
8087 * Frame Filter Management:: Managing frame filters
8092 @section Stack Frames
8094 @cindex frame, definition
8096 The call stack is divided up into contiguous pieces called @dfn{stack
8097 frames}, or @dfn{frames} for short; each frame is the data associated
8098 with one call to one function. The frame contains the arguments given
8099 to the function, the function's local variables, and the address at
8100 which the function is executing.
8102 @cindex initial frame
8103 @cindex outermost frame
8104 @cindex innermost frame
8105 When your program is started, the stack has only one frame, that of the
8106 function @code{main}. This is called the @dfn{initial} frame or the
8107 @dfn{outermost} frame. Each time a function is called, a new frame is
8108 made. Each time a function returns, the frame for that function invocation
8109 is eliminated. If a function is recursive, there can be many frames for
8110 the same function. The frame for the function in which execution is
8111 actually occurring is called the @dfn{innermost} frame. This is the most
8112 recently created of all the stack frames that still exist.
8114 @cindex frame pointer
8115 Inside your program, stack frames are identified by their addresses. A
8116 stack frame consists of many bytes, each of which has its own address; each
8117 kind of computer has a convention for choosing one byte whose
8118 address serves as the address of the frame. Usually this address is kept
8119 in a register called the @dfn{frame pointer register}
8120 (@pxref{Registers, $fp}) while execution is going on in that frame.
8123 @cindex frame number
8124 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8125 number that is zero for the innermost frame, one for the frame that
8126 called it, and so on upward. These level numbers give you a way of
8127 designating stack frames in @value{GDBN} commands. The terms
8128 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8129 describe this number.
8131 @c The -fomit-frame-pointer below perennially causes hbox overflow
8132 @c underflow problems.
8133 @cindex frameless execution
8134 Some compilers provide a way to compile functions so that they operate
8135 without stack frames. (For example, the @value{NGCC} option
8137 @samp{-fomit-frame-pointer}
8139 generates functions without a frame.)
8140 This is occasionally done with heavily used library functions to save
8141 the frame setup time. @value{GDBN} has limited facilities for dealing
8142 with these function invocations. If the innermost function invocation
8143 has no stack frame, @value{GDBN} nevertheless regards it as though
8144 it had a separate frame, which is numbered zero as usual, allowing
8145 correct tracing of the function call chain. However, @value{GDBN} has
8146 no provision for frameless functions elsewhere in the stack.
8152 @cindex call stack traces
8153 A backtrace is a summary of how your program got where it is. It shows one
8154 line per frame, for many frames, starting with the currently executing
8155 frame (frame zero), followed by its caller (frame one), and on up the
8158 @anchor{backtrace-command}
8160 @kindex bt @r{(@code{backtrace})}
8161 To print a backtrace of the entire stack, use the @code{backtrace}
8162 command, or its alias @code{bt}. This command will print one line per
8163 frame for frames in the stack. By default, all stack frames are
8164 printed. You can stop the backtrace at any time by typing the system
8165 interrupt character, normally @kbd{Ctrl-c}.
8168 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8169 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8170 Print the backtrace of the entire stack.
8172 The optional @var{count} can be one of the following:
8177 Print only the innermost @var{n} frames, where @var{n} is a positive
8182 Print only the outermost @var{n} frames, where @var{n} is a positive
8190 Print the values of the local variables also. This can be combined
8191 with the optional @var{count} to limit the number of frames shown.
8194 Do not run Python frame filters on this backtrace. @xref{Frame
8195 Filter API}, for more information. Additionally use @ref{disable
8196 frame-filter all} to turn off all frame filters. This is only
8197 relevant when @value{GDBN} has been configured with @code{Python}
8201 A Python frame filter might decide to ``elide'' some frames. Normally
8202 such elided frames are still printed, but they are indented relative
8203 to the filtered frames that cause them to be elided. The @code{-hide}
8204 option causes elided frames to not be printed at all.
8207 The @code{backtrace} command also supports a number of options that
8208 allow overriding relevant global print settings as set by @code{set
8209 backtrace} and @code{set print} subcommands:
8212 @item -past-main [@code{on}|@code{off}]
8213 Set whether backtraces should continue past @code{main}. Related setting:
8214 @ref{set backtrace past-main}.
8216 @item -past-entry [@code{on}|@code{off}]
8217 Set whether backtraces should continue past the entry point of a program.
8218 Related setting: @ref{set backtrace past-entry}.
8220 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8221 Set printing of function arguments at function entry.
8222 Related setting: @ref{set print entry-values}.
8224 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8225 Set printing of non-scalar frame arguments.
8226 Related setting: @ref{set print frame-arguments}.
8228 @item -raw-frame-arguments [@code{on}|@code{off}]
8229 Set whether to print frame arguments in raw form.
8230 Related setting: @ref{set print raw-frame-arguments}.
8232 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8233 Set printing of frame information.
8234 Related setting: @ref{set print frame-info}.
8237 The optional @var{qualifier} is maintained for backward compatibility.
8238 It can be one of the following:
8242 Equivalent to the @code{-full} option.
8245 Equivalent to the @code{-no-filters} option.
8248 Equivalent to the @code{-hide} option.
8255 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8256 are additional aliases for @code{backtrace}.
8258 @cindex multiple threads, backtrace
8259 In a multi-threaded program, @value{GDBN} by default shows the
8260 backtrace only for the current thread. To display the backtrace for
8261 several or all of the threads, use the command @code{thread apply}
8262 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8263 apply all backtrace}, @value{GDBN} will display the backtrace for all
8264 the threads; this is handy when you debug a core dump of a
8265 multi-threaded program.
8267 Each line in the backtrace shows the frame number and the function name.
8268 The program counter value is also shown---unless you use @code{set
8269 print address off}. The backtrace also shows the source file name and
8270 line number, as well as the arguments to the function. The program
8271 counter value is omitted if it is at the beginning of the code for that
8274 Here is an example of a backtrace. It was made with the command
8275 @samp{bt 3}, so it shows the innermost three frames.
8279 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8281 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8282 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8284 (More stack frames follow...)
8289 The display for frame zero does not begin with a program counter
8290 value, indicating that your program has stopped at the beginning of the
8291 code for line @code{993} of @code{builtin.c}.
8294 The value of parameter @code{data} in frame 1 has been replaced by
8295 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8296 only if it is a scalar (integer, pointer, enumeration, etc). See command
8297 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8298 on how to configure the way function parameter values are printed.
8299 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8300 what frame information is printed.
8302 @cindex optimized out, in backtrace
8303 @cindex function call arguments, optimized out
8304 If your program was compiled with optimizations, some compilers will
8305 optimize away arguments passed to functions if those arguments are
8306 never used after the call. Such optimizations generate code that
8307 passes arguments through registers, but doesn't store those arguments
8308 in the stack frame. @value{GDBN} has no way of displaying such
8309 arguments in stack frames other than the innermost one. Here's what
8310 such a backtrace might look like:
8314 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8316 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8317 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8319 (More stack frames follow...)
8324 The values of arguments that were not saved in their stack frames are
8325 shown as @samp{<optimized out>}.
8327 If you need to display the values of such optimized-out arguments,
8328 either deduce that from other variables whose values depend on the one
8329 you are interested in, or recompile without optimizations.
8331 @cindex backtrace beyond @code{main} function
8332 @cindex program entry point
8333 @cindex startup code, and backtrace
8334 Most programs have a standard user entry point---a place where system
8335 libraries and startup code transition into user code. For C this is
8336 @code{main}@footnote{
8337 Note that embedded programs (the so-called ``free-standing''
8338 environment) are not required to have a @code{main} function as the
8339 entry point. They could even have multiple entry points.}.
8340 When @value{GDBN} finds the entry function in a backtrace
8341 it will terminate the backtrace, to avoid tracing into highly
8342 system-specific (and generally uninteresting) code.
8344 If you need to examine the startup code, or limit the number of levels
8345 in a backtrace, you can change this behavior:
8348 @item set backtrace past-main
8349 @itemx set backtrace past-main on
8350 @anchor{set backtrace past-main}
8351 @kindex set backtrace
8352 Backtraces will continue past the user entry point.
8354 @item set backtrace past-main off
8355 Backtraces will stop when they encounter the user entry point. This is the
8358 @item show backtrace past-main
8359 @kindex show backtrace
8360 Display the current user entry point backtrace policy.
8362 @item set backtrace past-entry
8363 @itemx set backtrace past-entry on
8364 @anchor{set backtrace past-entry}
8365 Backtraces will continue past the internal entry point of an application.
8366 This entry point is encoded by the linker when the application is built,
8367 and is likely before the user entry point @code{main} (or equivalent) is called.
8369 @item set backtrace past-entry off
8370 Backtraces will stop when they encounter the internal entry point of an
8371 application. This is the default.
8373 @item show backtrace past-entry
8374 Display the current internal entry point backtrace policy.
8376 @item set backtrace limit @var{n}
8377 @itemx set backtrace limit 0
8378 @itemx set backtrace limit unlimited
8379 @anchor{set backtrace limit}
8380 @cindex backtrace limit
8381 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8382 or zero means unlimited levels.
8384 @item show backtrace limit
8385 Display the current limit on backtrace levels.
8388 You can control how file names are displayed.
8391 @item set filename-display
8392 @itemx set filename-display relative
8393 @cindex filename-display
8394 Display file names relative to the compilation directory. This is the default.
8396 @item set filename-display basename
8397 Display only basename of a filename.
8399 @item set filename-display absolute
8400 Display an absolute filename.
8402 @item show filename-display
8403 Show the current way to display filenames.
8407 @section Selecting a Frame
8409 Most commands for examining the stack and other data in your program work on
8410 whichever stack frame is selected at the moment. Here are the commands for
8411 selecting a stack frame; all of them finish by printing a brief description
8412 of the stack frame just selected.
8415 @kindex frame@r{, selecting}
8416 @kindex f @r{(@code{frame})}
8417 @item frame @r{[} @var{frame-selection-spec} @r{]}
8418 @item f @r{[} @var{frame-selection-spec} @r{]}
8419 The @command{frame} command allows different stack frames to be
8420 selected. The @var{frame-selection-spec} can be any of the following:
8425 @item level @var{num}
8426 Select frame level @var{num}. Recall that frame zero is the innermost
8427 (currently executing) frame, frame one is the frame that called the
8428 innermost one, and so on. The highest level frame is usually the one
8431 As this is the most common method of navigating the frame stack, the
8432 string @command{level} can be omitted. For example, the following two
8433 commands are equivalent:
8436 (@value{GDBP}) frame 3
8437 (@value{GDBP}) frame level 3
8440 @kindex frame address
8441 @item address @var{stack-address}
8442 Select the frame with stack address @var{stack-address}. The
8443 @var{stack-address} for a frame can be seen in the output of
8444 @command{info frame}, for example:
8448 Stack level 1, frame at 0x7fffffffda30:
8449 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8450 tail call frame, caller of frame at 0x7fffffffda30
8451 source language c++.
8452 Arglist at unknown address.
8453 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8456 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8457 indicated by the line:
8460 Stack level 1, frame at 0x7fffffffda30:
8463 @kindex frame function
8464 @item function @var{function-name}
8465 Select the stack frame for function @var{function-name}. If there are
8466 multiple stack frames for function @var{function-name} then the inner
8467 most stack frame is selected.
8470 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8471 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8472 viewed has stack address @var{stack-addr}, and optionally, a program
8473 counter address of @var{pc-addr}.
8475 This is useful mainly if the chaining of stack frames has been
8476 damaged by a bug, making it impossible for @value{GDBN} to assign
8477 numbers properly to all frames. In addition, this can be useful
8478 when your program has multiple stacks and switches between them.
8480 When viewing a frame outside the current backtrace using
8481 @command{frame view} then you can always return to the original
8482 stack using one of the previous stack frame selection instructions,
8483 for example @command{frame level 0}.
8489 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8490 numbers @var{n}, this advances toward the outermost frame, to higher
8491 frame numbers, to frames that have existed longer.
8494 @kindex do @r{(@code{down})}
8496 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8497 positive numbers @var{n}, this advances toward the innermost frame, to
8498 lower frame numbers, to frames that were created more recently.
8499 You may abbreviate @code{down} as @code{do}.
8502 All of these commands end by printing two lines of output describing the
8503 frame. The first line shows the frame number, the function name, the
8504 arguments, and the source file and line number of execution in that
8505 frame. The second line shows the text of that source line.
8513 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8515 10 read_input_file (argv[i]);
8519 After such a printout, the @code{list} command with no arguments
8520 prints ten lines centered on the point of execution in the frame.
8521 You can also edit the program at the point of execution with your favorite
8522 editing program by typing @code{edit}.
8523 @xref{List, ,Printing Source Lines},
8527 @kindex select-frame
8528 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8529 The @code{select-frame} command is a variant of @code{frame} that does
8530 not display the new frame after selecting it. This command is
8531 intended primarily for use in @value{GDBN} command scripts, where the
8532 output might be unnecessary and distracting. The
8533 @var{frame-selection-spec} is as for the @command{frame} command
8534 described in @ref{Selection, ,Selecting a Frame}.
8536 @kindex down-silently
8538 @item up-silently @var{n}
8539 @itemx down-silently @var{n}
8540 These two commands are variants of @code{up} and @code{down},
8541 respectively; they differ in that they do their work silently, without
8542 causing display of the new frame. They are intended primarily for use
8543 in @value{GDBN} command scripts, where the output might be unnecessary and
8548 @section Information About a Frame
8550 There are several other commands to print information about the selected
8556 When used without any argument, this command does not change which
8557 frame is selected, but prints a brief description of the currently
8558 selected stack frame. It can be abbreviated @code{f}. With an
8559 argument, this command is used to select a stack frame.
8560 @xref{Selection, ,Selecting a Frame}.
8563 @kindex info f @r{(@code{info frame})}
8566 This command prints a verbose description of the selected stack frame,
8571 the address of the frame
8573 the address of the next frame down (called by this frame)
8575 the address of the next frame up (caller of this frame)
8577 the language in which the source code corresponding to this frame is written
8579 the address of the frame's arguments
8581 the address of the frame's local variables
8583 the program counter saved in it (the address of execution in the caller frame)
8585 which registers were saved in the frame
8588 @noindent The verbose description is useful when
8589 something has gone wrong that has made the stack format fail to fit
8590 the usual conventions.
8592 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8593 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8594 Print a verbose description of the frame selected by
8595 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8596 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8597 a Frame}). The selected frame remains unchanged by this command.
8600 @item info args [-q]
8601 Print the arguments of the selected frame, each on a separate line.
8603 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8604 printing header information and messages explaining why no argument
8607 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8608 Like @kbd{info args}, but only print the arguments selected
8609 with the provided regexp(s).
8611 If @var{regexp} is provided, print only the arguments whose names
8612 match the regular expression @var{regexp}.
8614 If @var{type_regexp} is provided, print only the arguments whose
8615 types, as printed by the @code{whatis} command, match
8616 the regular expression @var{type_regexp}.
8617 If @var{type_regexp} contains space(s), it should be enclosed in
8618 quote characters. If needed, use backslash to escape the meaning
8619 of special characters or quotes.
8621 If both @var{regexp} and @var{type_regexp} are provided, an argument
8622 is printed only if its name matches @var{regexp} and its type matches
8625 @item info locals [-q]
8627 Print the local variables of the selected frame, each on a separate
8628 line. These are all variables (declared either static or automatic)
8629 accessible at the point of execution of the selected frame.
8631 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8632 printing header information and messages explaining why no local variables
8635 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8636 Like @kbd{info locals}, but only print the local variables selected
8637 with the provided regexp(s).
8639 If @var{regexp} is provided, print only the local variables whose names
8640 match the regular expression @var{regexp}.
8642 If @var{type_regexp} is provided, print only the local variables whose
8643 types, as printed by the @code{whatis} command, match
8644 the regular expression @var{type_regexp}.
8645 If @var{type_regexp} contains space(s), it should be enclosed in
8646 quote characters. If needed, use backslash to escape the meaning
8647 of special characters or quotes.
8649 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8650 is printed only if its name matches @var{regexp} and its type matches
8653 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8654 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8655 For example, your program might use Resource Acquisition Is
8656 Initialization types (RAII) such as @code{lock_something_t}: each
8657 local variable of type @code{lock_something_t} automatically places a
8658 lock that is destroyed when the variable goes out of scope. You can
8659 then list all acquired locks in your program by doing
8661 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8664 or the equivalent shorter form
8666 tfaas i lo -q -t lock_something_t
8672 @section Applying a Command to Several Frames.
8674 @cindex apply command to several frames
8676 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8677 The @code{frame apply} command allows you to apply the named
8678 @var{command} to one or more frames.
8682 Specify @code{all} to apply @var{command} to all frames.
8685 Use @var{count} to apply @var{command} to the innermost @var{count}
8686 frames, where @var{count} is a positive number.
8689 Use @var{-count} to apply @var{command} to the outermost @var{count}
8690 frames, where @var{count} is a positive number.
8693 Use @code{level} to apply @var{command} to the set of frames identified
8694 by the @var{level} list. @var{level} is a frame level or a range of frame
8695 levels as @var{level1}-@var{level2}. The frame level is the number shown
8696 in the first field of the @samp{backtrace} command output.
8697 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8698 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8702 Note that the frames on which @code{frame apply} applies a command are
8703 also influenced by the @code{set backtrace} settings such as @code{set
8704 backtrace past-main} and @code{set backtrace limit N}.
8705 @xref{Backtrace,,Backtraces}.
8707 The @code{frame apply} command also supports a number of options that
8708 allow overriding relevant @code{set backtrace} settings:
8711 @item -past-main [@code{on}|@code{off}]
8712 Whether backtraces should continue past @code{main}.
8713 Related setting: @ref{set backtrace past-main}.
8715 @item -past-entry [@code{on}|@code{off}]
8716 Whether backtraces should continue past the entry point of a program.
8717 Related setting: @ref{set backtrace past-entry}.
8720 By default, @value{GDBN} displays some frame information before the
8721 output produced by @var{command}, and an error raised during the
8722 execution of a @var{command} will abort @code{frame apply}. The
8723 following options can be used to fine-tune these behaviors:
8727 The flag @code{-c}, which stands for @samp{continue}, causes any
8728 errors in @var{command} to be displayed, and the execution of
8729 @code{frame apply} then continues.
8731 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8732 or empty output produced by a @var{command} to be silently ignored.
8733 That is, the execution continues, but the frame information and errors
8736 The flag @code{-q} (@samp{quiet}) disables printing the frame
8740 The following example shows how the flags @code{-c} and @code{-s} are
8741 working when applying the command @code{p j} to all frames, where
8742 variable @code{j} can only be successfully printed in the outermost
8743 @code{#1 main} frame.
8747 (gdb) frame apply all p j
8748 #0 some_function (i=5) at fun.c:4
8749 No symbol "j" in current context.
8750 (gdb) frame apply all -c p j
8751 #0 some_function (i=5) at fun.c:4
8752 No symbol "j" in current context.
8753 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8755 (gdb) frame apply all -s p j
8756 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8762 By default, @samp{frame apply}, prints the frame location
8763 information before the command output:
8767 (gdb) frame apply all p $sp
8768 #0 some_function (i=5) at fun.c:4
8769 $4 = (void *) 0xffffd1e0
8770 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8771 $5 = (void *) 0xffffd1f0
8776 If the flag @code{-q} is given, no frame information is printed:
8779 (gdb) frame apply all -q p $sp
8780 $12 = (void *) 0xffffd1e0
8781 $13 = (void *) 0xffffd1f0
8791 @cindex apply a command to all frames (ignoring errors and empty output)
8792 @item faas @var{command}
8793 Shortcut for @code{frame apply all -s @var{command}}.
8794 Applies @var{command} on all frames, ignoring errors and empty output.
8796 It can for example be used to print a local variable or a function
8797 argument without knowing the frame where this variable or argument
8800 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8803 The @code{faas} command accepts the same options as the @code{frame
8804 apply} command. @xref{Frame Apply,,frame apply}.
8806 Note that the command @code{tfaas @var{command}} applies @var{command}
8807 on all frames of all threads. See @xref{Threads,,Threads}.
8811 @node Frame Filter Management
8812 @section Management of Frame Filters.
8813 @cindex managing frame filters
8815 Frame filters are Python based utilities to manage and decorate the
8816 output of frames. @xref{Frame Filter API}, for further information.
8818 Managing frame filters is performed by several commands available
8819 within @value{GDBN}, detailed here.
8822 @kindex info frame-filter
8823 @item info frame-filter
8824 Print a list of installed frame filters from all dictionaries, showing
8825 their name, priority and enabled status.
8827 @kindex disable frame-filter
8828 @anchor{disable frame-filter all}
8829 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8830 Disable a frame filter in the dictionary matching
8831 @var{filter-dictionary} and @var{filter-name}. The
8832 @var{filter-dictionary} may be @code{all}, @code{global},
8833 @code{progspace}, or the name of the object file where the frame filter
8834 dictionary resides. When @code{all} is specified, all frame filters
8835 across all dictionaries are disabled. The @var{filter-name} is the name
8836 of the frame filter and is used when @code{all} is not the option for
8837 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8838 may be enabled again later.
8840 @kindex enable frame-filter
8841 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8842 Enable a frame filter in the dictionary matching
8843 @var{filter-dictionary} and @var{filter-name}. The
8844 @var{filter-dictionary} may be @code{all}, @code{global},
8845 @code{progspace} or the name of the object file where the frame filter
8846 dictionary resides. When @code{all} is specified, all frame filters across
8847 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8848 filter and is used when @code{all} is not the option for
8849 @var{filter-dictionary}.
8854 (gdb) info frame-filter
8856 global frame-filters:
8857 Priority Enabled Name
8858 1000 No PrimaryFunctionFilter
8861 progspace /build/test frame-filters:
8862 Priority Enabled Name
8863 100 Yes ProgspaceFilter
8865 objfile /build/test frame-filters:
8866 Priority Enabled Name
8867 999 Yes BuildProgramFilter
8869 (gdb) disable frame-filter /build/test BuildProgramFilter
8870 (gdb) info frame-filter
8872 global frame-filters:
8873 Priority Enabled Name
8874 1000 No PrimaryFunctionFilter
8877 progspace /build/test frame-filters:
8878 Priority Enabled Name
8879 100 Yes ProgspaceFilter
8881 objfile /build/test frame-filters:
8882 Priority Enabled Name
8883 999 No BuildProgramFilter
8885 (gdb) enable frame-filter global PrimaryFunctionFilter
8886 (gdb) info frame-filter
8888 global frame-filters:
8889 Priority Enabled Name
8890 1000 Yes PrimaryFunctionFilter
8893 progspace /build/test frame-filters:
8894 Priority Enabled Name
8895 100 Yes ProgspaceFilter
8897 objfile /build/test frame-filters:
8898 Priority Enabled Name
8899 999 No BuildProgramFilter
8902 @kindex set frame-filter priority
8903 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8904 Set the @var{priority} of a frame filter in the dictionary matching
8905 @var{filter-dictionary}, and the frame filter name matching
8906 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8907 @code{progspace} or the name of the object file where the frame filter
8908 dictionary resides. The @var{priority} is an integer.
8910 @kindex show frame-filter priority
8911 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8912 Show the @var{priority} of a frame filter in the dictionary matching
8913 @var{filter-dictionary}, and the frame filter name matching
8914 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8915 @code{progspace} or the name of the object file where the frame filter
8921 (gdb) info frame-filter
8923 global frame-filters:
8924 Priority Enabled Name
8925 1000 Yes PrimaryFunctionFilter
8928 progspace /build/test frame-filters:
8929 Priority Enabled Name
8930 100 Yes ProgspaceFilter
8932 objfile /build/test frame-filters:
8933 Priority Enabled Name
8934 999 No BuildProgramFilter
8936 (gdb) set frame-filter priority global Reverse 50
8937 (gdb) info frame-filter
8939 global frame-filters:
8940 Priority Enabled Name
8941 1000 Yes PrimaryFunctionFilter
8944 progspace /build/test frame-filters:
8945 Priority Enabled Name
8946 100 Yes ProgspaceFilter
8948 objfile /build/test frame-filters:
8949 Priority Enabled Name
8950 999 No BuildProgramFilter
8955 @chapter Examining Source Files
8957 @value{GDBN} can print parts of your program's source, since the debugging
8958 information recorded in the program tells @value{GDBN} what source files were
8959 used to build it. When your program stops, @value{GDBN} spontaneously prints
8960 the line where it stopped. Likewise, when you select a stack frame
8961 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8962 execution in that frame has stopped. You can print other portions of
8963 source files by explicit command.
8965 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8966 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8967 @value{GDBN} under @sc{gnu} Emacs}.
8970 * List:: Printing source lines
8971 * Location Specifications:: How to specify code locations
8972 * Edit:: Editing source files
8973 * Search:: Searching source files
8974 * Source Path:: Specifying source directories
8975 * Machine Code:: Source and machine code
8976 * Disable Reading Source:: Disable Reading Source Code
8980 @section Printing Source Lines
8983 @kindex l @r{(@code{list})}
8984 To print lines from a source file, use the @code{list} command
8985 (abbreviated @code{l}). By default, ten lines are printed.
8986 There are several ways to specify what part of the file you want to
8987 print; see @ref{Location Specifications}, for the full list.
8989 Here are the forms of the @code{list} command most commonly used:
8992 @item list @var{linenum}
8993 Print lines centered around line number @var{linenum} in the
8994 current source file.
8996 @item list @var{function}
8997 Print lines centered around the beginning of function
9001 Print more lines. If the last lines printed were printed with a
9002 @code{list} command, this prints lines following the last lines
9003 printed; however, if the last line printed was a solitary line printed
9004 as part of displaying a stack frame (@pxref{Stack, ,Examining the
9005 Stack}), this prints lines centered around that line.
9008 Print lines just before the lines last printed.
9011 @cindex @code{list}, how many lines to display
9012 By default, @value{GDBN} prints ten source lines with any of these forms of
9013 the @code{list} command. You can change this using @code{set listsize}:
9016 @kindex set listsize
9017 @item set listsize @var{count}
9018 @itemx set listsize unlimited
9019 Make the @code{list} command display @var{count} source lines (unless
9020 the @code{list} argument explicitly specifies some other number).
9021 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
9023 @kindex show listsize
9025 Display the number of lines that @code{list} prints.
9028 Repeating a @code{list} command with @key{RET} discards the argument,
9029 so it is equivalent to typing just @code{list}. This is more useful
9030 than listing the same lines again. An exception is made for an
9031 argument of @samp{-}; that argument is preserved in repetition so that
9032 each repetition moves up in the source file.
9034 In general, the @code{list} command expects you to supply zero, one or
9035 two location specs. These location specs are interpreted to resolve
9036 to source code lines; there are several ways of writing them
9037 (@pxref{Location Specifications}), but the effect is always to resolve
9038 to some source lines to display.
9040 Here is a complete description of the possible arguments for @code{list}:
9043 @item list @var{locspec}
9044 Print lines centered around the line or lines of all the code
9045 locations that result from resolving @var{locspec}.
9047 @item list @var{first},@var{last}
9048 Print lines from @var{first} to @var{last}. Both arguments are
9049 location specs. When a @code{list} command has two location specs,
9050 and the source file of the second location spec is omitted, this
9051 refers to the same source file as the first location spec. If either
9052 @var{first} or @var{last} resolve to more than one source line in the
9053 program, then the list command shows the list of resolved source
9054 lines and does not proceed with the source code listing.
9056 @item list ,@var{last}
9057 Print lines ending with @var{last}.
9059 Likewise, if @var{last} resolves to more than one source line in the
9060 program, then the list command prints the list of resolved source
9061 lines and does not proceed with the source code listing.
9063 @item list @var{first},
9064 Print lines starting with @var{first}.
9067 Print lines just after the lines last printed.
9070 Print lines just before the lines last printed.
9073 As described in the preceding table.
9076 @node Location Specifications
9077 @section Location Specifications
9078 @cindex specifying location
9080 @cindex source location
9081 @cindex code location
9083 @cindex location spec
9084 Several @value{GDBN} commands accept arguments that specify a location
9085 or locations of your program's code. Many times locations are
9086 specified using a source line number, but they can also be specified
9087 by a function name, an address, a label, etc. The different
9088 forms of specifying a location that @value{GDBN} recognizes are
9089 collectively known as forms of @dfn{location specification}, or
9090 @dfn{location spec}. This section documents the forms of specifying
9091 locations that @value{GDBN} recognizes.
9093 @cindex location resolution
9094 @cindex resolution of location spec
9095 When you specify a location, @value{GDBN} needs to find the place in
9096 your program, known as @dfn{code location}, that corresponds to the
9097 given location spec. We call this process of finding actual code
9098 locations corresponding to a location spec @dfn{location resolution}.
9100 A concrete code location in your program is uniquely identifiable by a
9101 set of several attributes: its source line number, the name of its
9102 source file, the fully-qualified and prototyped function in which it
9103 is defined, and an instruction address. Because each inferior has its
9104 own address space, the inferior number is also a necessary part of
9107 By contrast, location specs you type will many times omit some of
9108 these attributes. For example, it is customary to specify just the
9109 source line number to mean a line in the current source file, or
9110 specify just the basename of the file, omitting its directories. In
9111 other words, a location spec is usually incomplete, a kind of
9112 blueprint, and @value{GDBN} needs to complete the missing attributes
9113 by using the implied defaults, and by considering the source code and
9114 the debug information available to it. This is what location
9115 resolution is about.
9117 The resolution of an incomplete location spec can produce more than a
9118 single code location, if the spec doesn't allow distinguishing between
9119 them. Here are some examples of situations that result in a location
9120 spec matching multiple code locations in your program:
9124 The location spec specifies a function name, and there are several
9125 functions in the program which have that name. (To distinguish
9126 between them, you can specify a fully-qualified and prototyped
9127 function name, such as @code{A::func(int)} instead of just
9131 The location spec specifies a source file name, and there are several
9132 source files in the program that share the same name, for example
9133 several files with the same basename in different subdirectories. (To
9134 distinguish between them, specify enough leading directories with the
9138 For a C@t{++} constructor, the @value{NGCC} compiler generates several
9139 instances of the function body, used in different cases, but their
9140 source-level names are identical.
9143 For a C@t{++} template function, a given line in the function can
9144 correspond to any number of instantiations.
9147 For an inlined function, a given source line can correspond to several
9148 actual code locations with that function's inlined code.
9151 Resolution of a location spec can also fail to produce a complete code
9152 location, or even fail to produce any code location. Here are some
9153 examples of such situations:
9157 Some parts of the program lack detailed enough debug info, so the
9158 resolved code location lacks some attributes, like source file name
9159 and line number, leaving just the instruction address and perhaps also
9160 a function name. Such an incomplete code location is only usable in
9161 contexts that work with addresses and/or function names. Some
9162 commands can only work with complete code locations.
9165 The location spec specifies a function name, and there are no
9166 functions in the program by that name, or they only exist in a
9167 yet-unloaded shared library.
9170 The location spec specifies a source file name, and there are no
9171 source files in the program by that name, or they only exist in a
9172 yet-unloaded shared library.
9175 The location spec specifies both a source file name and a source line
9176 number, and even though there are source files in the program that
9177 match the file name, none of those files has the specified line
9181 Locations may be specified using three different formats: linespec
9182 locations, explicit locations, or address locations. The following
9183 subsections describe these formats.
9186 * Linespec Locations:: Linespec locations
9187 * Explicit Locations:: Explicit locations
9188 * Address Locations:: Address locations
9191 @node Linespec Locations
9192 @subsection Linespec Locations
9193 @cindex linespec locations
9195 A @dfn{linespec} is a colon-separated list of source location parameters such
9196 as file name, function name, etc. Here are all the different ways of
9197 specifying a linespec:
9201 Specifies the line number @var{linenum} of the current source file.
9204 @itemx +@var{offset}
9205 Specifies the line @var{offset} lines before or after the @dfn{current
9206 line}. For the @code{list} command, the current line is the last one
9207 printed; for the breakpoint commands, this is the line at which
9208 execution stopped in the currently selected @dfn{stack frame}
9209 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9210 used as the second of the two linespecs in a @code{list} command,
9211 this specifies the line @var{offset} lines up or down from the first
9214 @item @var{filename}:@var{linenum}
9215 Specifies the line @var{linenum} in the source file @var{filename}.
9216 If @var{filename} is a relative file name, then it will match any
9217 source file name with the same trailing components. For example, if
9218 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9219 name of @file{/build/trunk/gcc/expr.c}, but not
9220 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9222 @item @var{function}
9223 Specifies the line that begins the body of the function @var{function}.
9224 For example, in C, this is the line with the open brace.
9226 By default, in C@t{++} and Ada, @var{function} is interpreted as
9227 specifying all functions named @var{function} in all scopes. For
9228 C@t{++}, this means in all namespaces and classes. For Ada, this
9229 means in all packages.
9231 For example, assuming a program with C@t{++} symbols named
9232 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9233 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9235 Commands that accept a linespec let you override this with the
9236 @code{-qualified} option. For example, @w{@kbd{break -qualified
9237 func}} sets a breakpoint on a free-function named @code{func} ignoring
9238 any C@t{++} class methods and namespace functions called @code{func}.
9240 @xref{Explicit Locations}.
9242 @item @var{function}:@var{label}
9243 Specifies the line where @var{label} appears in @var{function}.
9245 @item @var{filename}:@var{function}
9246 Specifies the line that begins the body of the function @var{function}
9247 in the file @var{filename}. You only need the file name with a
9248 function name to avoid ambiguity when there are identically named
9249 functions in different source files.
9252 Specifies the line at which the label named @var{label} appears
9253 in the function corresponding to the currently selected stack frame.
9254 If there is no current selected stack frame (for instance, if the inferior
9255 is not running), then @value{GDBN} will not search for a label.
9257 @cindex breakpoint at static probe point
9258 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9259 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9260 applications to embed static probes. @xref{Static Probe Points}, for more
9261 information on finding and using static probes. This form of linespec
9262 specifies the location of such a static probe.
9264 If @var{objfile} is given, only probes coming from that shared library
9265 or executable matching @var{objfile} as a regular expression are considered.
9266 If @var{provider} is given, then only probes from that provider are considered.
9267 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9268 each one of those probes.
9271 @node Explicit Locations
9272 @subsection Explicit Locations
9273 @cindex explicit locations
9275 @dfn{Explicit locations} allow the user to directly specify the source
9276 location's parameters using option-value pairs.
9278 Explicit locations are useful when several functions, labels, or
9279 file names have the same name (base name for files) in the program's
9280 sources. In these cases, explicit locations point to the source
9281 line you meant more accurately and unambiguously. Also, using
9282 explicit locations might be faster in large programs.
9284 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9285 defined in the file named @file{foo} or the label @code{bar} in a function
9286 named @code{foo}. @value{GDBN} must search either the file system or
9287 the symbol table to know.
9289 The list of valid explicit location options is summarized in the
9293 @item -source @var{filename}
9294 The value specifies the source file name. To differentiate between
9295 files with the same base name, prepend as many directories as is necessary
9296 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9297 @value{GDBN} will use the first file it finds with the given base
9298 name. This option requires the use of either @code{-function} or @code{-line}.
9300 @item -function @var{function}
9301 The value specifies the name of a function. Operations
9302 on function locations unmodified by other options (such as @code{-label}
9303 or @code{-line}) refer to the line that begins the body of the function.
9304 In C, for example, this is the line with the open brace.
9306 By default, in C@t{++} and Ada, @var{function} is interpreted as
9307 specifying all functions named @var{function} in all scopes. For
9308 C@t{++}, this means in all namespaces and classes. For Ada, this
9309 means in all packages.
9311 For example, assuming a program with C@t{++} symbols named
9312 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9313 -function func}} and @w{@kbd{break -function B::func}} set a
9314 breakpoint on both symbols.
9316 You can use the @kbd{-qualified} flag to override this (see below).
9320 This flag makes @value{GDBN} interpret a function name specified with
9321 @kbd{-function} as a complete fully-qualified name.
9323 For example, assuming a C@t{++} program with symbols named
9324 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9325 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9327 (Note: the @kbd{-qualified} option can precede a linespec as well
9328 (@pxref{Linespec Locations}), so the particular example above could be
9329 simplified as @w{@kbd{break -qualified B::func}}.)
9331 @item -label @var{label}
9332 The value specifies the name of a label. When the function
9333 name is not specified, the label is searched in the function of the currently
9334 selected stack frame.
9336 @item -line @var{number}
9337 The value specifies a line offset for the location. The offset may either
9338 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9339 the command. When specified without any other options, the line offset is
9340 relative to the current line.
9343 Explicit location options may be abbreviated by omitting any non-unique
9344 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9346 @node Address Locations
9347 @subsection Address Locations
9348 @cindex address locations
9350 @dfn{Address locations} indicate a specific program address. They have
9351 the generalized form *@var{address}.
9353 For line-oriented commands, such as @code{list} and @code{edit}, this
9354 specifies a source line that contains @var{address}. For @code{break} and
9355 other breakpoint-oriented commands, this can be used to set breakpoints in
9356 parts of your program which do not have debugging information or
9359 Here @var{address} may be any expression valid in the current working
9360 language (@pxref{Languages, working language}) that specifies a code
9361 address. In addition, as a convenience, @value{GDBN} extends the
9362 semantics of expressions used in locations to cover several situations
9363 that frequently occur during debugging. Here are the various forms
9367 @item @var{expression}
9368 Any expression valid in the current working language.
9370 @item @var{funcaddr}
9371 An address of a function or procedure derived from its name. In C,
9372 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9373 simply the function's name @var{function} (and actually a special case
9374 of a valid expression). In Pascal and Modula-2, this is
9375 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9376 (although the Pascal form also works).
9378 This form specifies the address of the function's first instruction,
9379 before the stack frame and arguments have been set up.
9381 @item '@var{filename}':@var{funcaddr}
9382 Like @var{funcaddr} above, but also specifies the name of the source
9383 file explicitly. This is useful if the name of the function does not
9384 specify the function unambiguously, e.g., if there are several
9385 functions with identical names in different source files.
9389 @section Editing Source Files
9390 @cindex editing source files
9393 @kindex e @r{(@code{edit})}
9394 To edit the lines in a source file, use the @code{edit} command.
9395 The editing program of your choice
9396 is invoked with the current line set to
9397 the active line in the program.
9398 Alternatively, there are several ways to specify what part of the file you
9399 want to print if you want to see other parts of the program:
9402 @item edit @var{locspec}
9403 Edit the source file of the code location that results from resolving
9404 @code{locspec}. Editing starts at the source file and source line
9405 @code{locspec} resolves to.
9406 @xref{Location Specifications}, for all the possible forms of the
9407 @var{locspec} argument.
9409 If @code{locspec} resolves to more than one source line in your
9410 program, then the command prints the list of resolved source lines and
9411 does not proceed with the editing.
9413 Here are the forms of the @code{edit} command most commonly used:
9416 @item edit @var{number}
9417 Edit the current source file with @var{number} as the active line number.
9419 @item edit @var{function}
9420 Edit the file containing @var{function} at the beginning of its definition.
9425 @subsection Choosing your Editor
9426 You can customize @value{GDBN} to use any editor you want
9428 The only restriction is that your editor (say @code{ex}), recognizes the
9429 following command-line syntax:
9431 ex +@var{number} file
9433 The optional numeric value +@var{number} specifies the number of the line in
9434 the file where to start editing.}.
9435 By default, it is @file{@value{EDITOR}}, but you can change this
9436 by setting the environment variable @env{EDITOR} before using
9437 @value{GDBN}. For example, to configure @value{GDBN} to use the
9438 @code{vi} editor, you could use these commands with the @code{sh} shell:
9444 or in the @code{csh} shell,
9446 setenv EDITOR /usr/bin/vi
9451 @section Searching Source Files
9452 @cindex searching source files
9454 There are two commands for searching through the current source file for a
9459 @kindex forward-search
9460 @kindex fo @r{(@code{forward-search})}
9461 @item forward-search @var{regexp}
9462 @itemx search @var{regexp}
9463 The command @samp{forward-search @var{regexp}} checks each line,
9464 starting with the one following the last line listed, for a match for
9465 @var{regexp}. It lists the line that is found. You can use the
9466 synonym @samp{search @var{regexp}} or abbreviate the command name as
9469 @kindex reverse-search
9470 @item reverse-search @var{regexp}
9471 The command @samp{reverse-search @var{regexp}} checks each line, starting
9472 with the one before the last line listed and going backward, for a match
9473 for @var{regexp}. It lists the line that is found. You can abbreviate
9474 this command as @code{rev}.
9478 @section Specifying Source Directories
9481 @cindex directories for source files
9482 Executable programs sometimes do not record the directories of the source
9483 files from which they were compiled, just the names. Even when they do,
9484 the directories could be moved between the compilation and your debugging
9485 session. @value{GDBN} has a list of directories to search for source files;
9486 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9487 it tries all the directories in the list, in the order they are present
9488 in the list, until it finds a file with the desired name.
9490 For example, suppose an executable references the file
9491 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9492 directory, and the @dfn{source path} is @file{/mnt/cross}.
9493 @value{GDBN} would look for the source file in the following
9498 @item @file{/usr/src/foo-1.0/lib/foo.c}
9499 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9500 @item @file{/mnt/cross/foo.c}
9504 If the source file is not present at any of the above locations then
9505 an error is printed. @value{GDBN} does not look up the parts of the
9506 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9507 Likewise, the subdirectories of the source path are not searched: if
9508 the source path is @file{/mnt/cross}, and the binary refers to
9509 @file{foo.c}, @value{GDBN} would not find it under
9510 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9512 Plain file names, relative file names with leading directories, file
9513 names containing dots, etc.@: are all treated as described above,
9514 except that non-absolute file names are not looked up literally. If
9515 the @dfn{source path} is @file{/mnt/cross}, the source file is
9516 recorded as @file{../lib/foo.c}, and no compilation directory is
9517 recorded, then @value{GDBN} will search in the following locations:
9521 @item @file{/mnt/cross/../lib/foo.c}
9522 @item @file{/mnt/cross/foo.c}
9528 @vindex $cdir@r{, convenience variable}
9529 @vindex $cwd@r{, convenience variable}
9530 @cindex compilation directory
9531 @cindex current directory
9532 @cindex working directory
9533 @cindex directory, current
9534 @cindex directory, compilation
9535 The @dfn{source path} will always include two special entries
9536 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9537 (if one is recorded) and the current working directory respectively.
9539 @samp{$cdir} causes @value{GDBN} to search within the compilation
9540 directory, if one is recorded in the debug information. If no
9541 compilation directory is recorded in the debug information then
9542 @samp{$cdir} is ignored.
9544 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9545 current working directory as it changes during your @value{GDBN}
9546 session, while the latter is immediately expanded to the current
9547 directory at the time you add an entry to the source path.
9549 If a compilation directory is recorded in the debug information, and
9550 @value{GDBN} has not found the source file after the first search
9551 using @dfn{source path}, then @value{GDBN} will combine the
9552 compilation directory and the filename, and then search for the source
9553 file again using the @dfn{source path}.
9555 For example, if the executable records the source file as
9556 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9557 recorded as @file{/project/build}, and the @dfn{source path} is
9558 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9559 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9560 search for the source file in the following locations:
9564 @item @file{/usr/src/foo-1.0/lib/foo.c}
9565 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9566 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9567 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9568 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9569 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9570 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9571 @item @file{/mnt/cross/foo.c}
9572 @item @file{/project/build/foo.c}
9573 @item @file{/home/user/foo.c}
9577 If the file name in the previous example had been recorded in the
9578 executable as a relative path rather than an absolute path, then the
9579 first look up would not have occurred, but all of the remaining steps
9582 When searching for source files on MS-DOS and MS-Windows, where
9583 absolute paths start with a drive letter (e.g.@:
9584 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9585 from the file name before appending it to a search directory from
9586 @dfn{source path}; for instance if the executable references the
9587 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9588 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9589 locations for the source file:
9593 @item @file{C:/project/foo.c}
9594 @item @file{D:/mnt/cross/project/foo.c}
9595 @item @file{D:/mnt/cross/foo.c}
9599 Note that the executable search path is @emph{not} used to locate the
9602 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9603 any information it has cached about where source files are found and where
9604 each line is in the file.
9608 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9609 and @samp{$cwd}, in that order.
9610 To add other directories, use the @code{directory} command.
9612 The search path is used to find both program source files and @value{GDBN}
9613 script files (read using the @samp{-command} option and @samp{source} command).
9615 In addition to the source path, @value{GDBN} provides a set of commands
9616 that manage a list of source path substitution rules. A @dfn{substitution
9617 rule} specifies how to rewrite source directories stored in the program's
9618 debug information in case the sources were moved to a different
9619 directory between compilation and debugging. A rule is made of
9620 two strings, the first specifying what needs to be rewritten in
9621 the path, and the second specifying how it should be rewritten.
9622 In @ref{set substitute-path}, we name these two parts @var{from} and
9623 @var{to} respectively. @value{GDBN} does a simple string replacement
9624 of @var{from} with @var{to} at the start of the directory part of the
9625 source file name, and uses that result instead of the original file
9626 name to look up the sources.
9628 Using the previous example, suppose the @file{foo-1.0} tree has been
9629 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9630 @value{GDBN} to replace @file{/usr/src} in all source path names with
9631 @file{/mnt/cross}. The first lookup will then be
9632 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9633 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9634 substitution rule, use the @code{set substitute-path} command
9635 (@pxref{set substitute-path}).
9637 To avoid unexpected substitution results, a rule is applied only if the
9638 @var{from} part of the directory name ends at a directory separator.
9639 For instance, a rule substituting @file{/usr/source} into
9640 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9641 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9642 is applied only at the beginning of the directory name, this rule will
9643 not be applied to @file{/root/usr/source/baz.c} either.
9645 In many cases, you can achieve the same result using the @code{directory}
9646 command. However, @code{set substitute-path} can be more efficient in
9647 the case where the sources are organized in a complex tree with multiple
9648 subdirectories. With the @code{directory} command, you need to add each
9649 subdirectory of your project. If you moved the entire tree while
9650 preserving its internal organization, then @code{set substitute-path}
9651 allows you to direct the debugger to all the sources with one single
9654 @code{set substitute-path} is also more than just a shortcut command.
9655 The source path is only used if the file at the original location no
9656 longer exists. On the other hand, @code{set substitute-path} modifies
9657 the debugger behavior to look at the rewritten location instead. So, if
9658 for any reason a source file that is not relevant to your executable is
9659 located at the original location, a substitution rule is the only
9660 method available to point @value{GDBN} at the new location.
9662 @cindex @samp{--with-relocated-sources}
9663 @cindex default source path substitution
9664 You can configure a default source path substitution rule by
9665 configuring @value{GDBN} with the
9666 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9667 should be the name of a directory under @value{GDBN}'s configured
9668 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9669 directory names in debug information under @var{dir} will be adjusted
9670 automatically if the installed @value{GDBN} is moved to a new
9671 location. This is useful if @value{GDBN}, libraries or executables
9672 with debug information and corresponding source code are being moved
9676 @item directory @var{dirname} @dots{}
9677 @item dir @var{dirname} @dots{}
9678 Add directory @var{dirname} to the front of the source path. Several
9679 directory names may be given to this command, separated by @samp{:}
9680 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9681 part of absolute file names) or
9682 whitespace. You may specify a directory that is already in the source
9683 path; this moves it forward, so @value{GDBN} searches it sooner.
9685 The special strings @samp{$cdir} (to refer to the compilation
9686 directory, if one is recorded), and @samp{$cwd} (to refer to the
9687 current working directory) can also be included in the list of
9688 directories @var{dirname}. Though these will already be in the source
9689 path they will be moved forward in the list so @value{GDBN} searches
9693 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9695 @c RET-repeat for @code{directory} is explicitly disabled, but since
9696 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9698 @item set directories @var{path-list}
9699 @kindex set directories
9700 Set the source path to @var{path-list}.
9701 @samp{$cdir:$cwd} are added if missing.
9703 @item show directories
9704 @kindex show directories
9705 Print the source path: show which directories it contains.
9707 @anchor{set substitute-path}
9708 @item set substitute-path @var{from} @var{to}
9709 @kindex set substitute-path
9710 Define a source path substitution rule, and add it at the end of the
9711 current list of existing substitution rules. If a rule with the same
9712 @var{from} was already defined, then the old rule is also deleted.
9714 For example, if the file @file{/foo/bar/baz.c} was moved to
9715 @file{/mnt/cross/baz.c}, then the command
9718 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9722 will tell @value{GDBN} to replace @samp{/foo/bar} with
9723 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9724 @file{baz.c} even though it was moved.
9726 In the case when more than one substitution rule have been defined,
9727 the rules are evaluated one by one in the order where they have been
9728 defined. The first one matching, if any, is selected to perform
9731 For instance, if we had entered the following commands:
9734 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9735 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9739 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9740 @file{/mnt/include/defs.h} by using the first rule. However, it would
9741 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9742 @file{/mnt/src/lib/foo.c}.
9745 @item unset substitute-path [path]
9746 @kindex unset substitute-path
9747 If a path is specified, search the current list of substitution rules
9748 for a rule that would rewrite that path. Delete that rule if found.
9749 A warning is emitted by the debugger if no rule could be found.
9751 If no path is specified, then all substitution rules are deleted.
9753 @item show substitute-path [path]
9754 @kindex show substitute-path
9755 If a path is specified, then print the source path substitution rule
9756 which would rewrite that path, if any.
9758 If no path is specified, then print all existing source path substitution
9763 If your source path is cluttered with directories that are no longer of
9764 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9765 versions of source. You can correct the situation as follows:
9769 Use @code{directory} with no argument to reset the source path to its default value.
9772 Use @code{directory} with suitable arguments to reinstall the
9773 directories you want in the source path. You can add all the
9774 directories in one command.
9778 @section Source and Machine Code
9779 @cindex source line and its code address
9781 You can use the command @code{info line} to map source lines to program
9782 addresses (and vice versa), and the command @code{disassemble} to display
9783 a range of addresses as machine instructions. You can use the command
9784 @code{set disassemble-next-line} to set whether to disassemble next
9785 source line when execution stops. When run under @sc{gnu} Emacs
9786 mode, the @code{info line} command causes the arrow to point to the
9787 line specified. Also, @code{info line} prints addresses in symbolic form as
9793 @itemx info line @var{locspec}
9794 Print the starting and ending addresses of the compiled code for the
9795 source lines of the code locations that result from resolving
9796 @var{locspec}. @xref{Location Specifications}, for the various forms
9798 With no @var{locspec}, information about the current source line is
9802 For example, we can use @code{info line} to discover the location of
9803 the object code for the first line of function
9804 @code{m4_changequote}:
9807 (@value{GDBP}) info line m4_changequote
9808 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9809 ends at 0x6350 <m4_changequote+4>.
9813 @cindex code address and its source line
9814 We can also inquire, using @code{*@var{addr}} as the form for
9815 @var{locspec}, what source line covers a particular address
9818 (@value{GDBP}) info line *0x63ff
9819 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9820 ends at 0x6404 <m4_changequote+184>.
9823 @cindex @code{$_} and @code{info line}
9824 @cindex @code{x} command, default address
9825 @kindex x@r{(examine), and} info line
9826 After @code{info line}, the default address for the @code{x} command
9827 is changed to the starting address of the line, so that @samp{x/i} is
9828 sufficient to begin examining the machine code (@pxref{Memory,
9829 ,Examining Memory}). Also, this address is saved as the value of the
9830 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9833 @cindex info line, repeated calls
9834 After @code{info line}, using @code{info line} again without
9835 specifying a location will display information about the next source
9840 @cindex assembly instructions
9841 @cindex instructions, assembly
9842 @cindex machine instructions
9843 @cindex listing machine instructions
9845 @itemx disassemble /m
9846 @itemx disassemble /s
9847 @itemx disassemble /r
9848 This specialized command dumps a range of memory as machine
9849 instructions. It can also print mixed source+disassembly by specifying
9850 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9851 as well as in symbolic form by specifying the @code{/r} modifier.
9852 The default memory range is the function surrounding the
9853 program counter of the selected frame. A single argument to this
9854 command is a program counter value; @value{GDBN} dumps the function
9855 surrounding this value. When two arguments are given, they should
9856 be separated by a comma, possibly surrounded by whitespace. The
9857 arguments specify a range of addresses to dump, in one of two forms:
9860 @item @var{start},@var{end}
9861 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9862 @item @var{start},+@var{length}
9863 the addresses from @var{start} (inclusive) to
9864 @code{@var{start}+@var{length}} (exclusive).
9868 When 2 arguments are specified, the name of the function is also
9869 printed (since there could be several functions in the given range).
9871 The argument(s) can be any expression yielding a numeric value, such as
9872 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9874 If the range of memory being disassembled contains current program counter,
9875 the instruction at that location is shown with a @code{=>} marker.
9878 The following example shows the disassembly of a range of addresses of
9879 HP PA-RISC 2.0 code:
9882 (@value{GDBP}) disas 0x32c4, 0x32e4
9883 Dump of assembler code from 0x32c4 to 0x32e4:
9884 0x32c4 <main+204>: addil 0,dp
9885 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9886 0x32cc <main+212>: ldil 0x3000,r31
9887 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9888 0x32d4 <main+220>: ldo 0(r31),rp
9889 0x32d8 <main+224>: addil -0x800,dp
9890 0x32dc <main+228>: ldo 0x588(r1),r26
9891 0x32e0 <main+232>: ldil 0x3000,r31
9892 End of assembler dump.
9895 Here is an example showing mixed source+assembly for Intel x86
9896 with @code{/m} or @code{/s}, when the program is stopped just after
9897 function prologue in a non-optimized function with no inline code.
9900 (@value{GDBP}) disas /m main
9901 Dump of assembler code for function main:
9903 0x08048330 <+0>: push %ebp
9904 0x08048331 <+1>: mov %esp,%ebp
9905 0x08048333 <+3>: sub $0x8,%esp
9906 0x08048336 <+6>: and $0xfffffff0,%esp
9907 0x08048339 <+9>: sub $0x10,%esp
9909 6 printf ("Hello.\n");
9910 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9911 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9915 0x08048348 <+24>: mov $0x0,%eax
9916 0x0804834d <+29>: leave
9917 0x0804834e <+30>: ret
9919 End of assembler dump.
9922 The @code{/m} option is deprecated as its output is not useful when
9923 there is either inlined code or re-ordered code.
9924 The @code{/s} option is the preferred choice.
9925 Here is an example for AMD x86-64 showing the difference between
9926 @code{/m} output and @code{/s} output.
9927 This example has one inline function defined in a header file,
9928 and the code is compiled with @samp{-O2} optimization.
9929 Note how the @code{/m} output is missing the disassembly of
9930 several instructions that are present in the @code{/s} output.
9960 (@value{GDBP}) disas /m main
9961 Dump of assembler code for function main:
9965 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9966 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9970 0x000000000040041d <+29>: xor %eax,%eax
9971 0x000000000040041f <+31>: retq
9972 0x0000000000400420 <+32>: add %eax,%eax
9973 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9975 End of assembler dump.
9976 (@value{GDBP}) disas /s main
9977 Dump of assembler code for function main:
9981 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9985 0x0000000000400406 <+6>: test %eax,%eax
9986 0x0000000000400408 <+8>: js 0x400420 <main+32>
9991 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9992 0x000000000040040d <+13>: test %eax,%eax
9993 0x000000000040040f <+15>: mov $0x1,%eax
9994 0x0000000000400414 <+20>: cmovne %edx,%eax
9998 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10002 0x000000000040041d <+29>: xor %eax,%eax
10003 0x000000000040041f <+31>: retq
10007 0x0000000000400420 <+32>: add %eax,%eax
10008 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10009 End of assembler dump.
10012 Here is another example showing raw instructions in hex for AMD x86-64,
10015 (gdb) disas /r 0x400281,+10
10016 Dump of assembler code from 0x400281 to 0x40028b:
10017 0x0000000000400281: 38 36 cmp %dh,(%rsi)
10018 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
10019 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
10020 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
10021 End of assembler dump.
10024 Note that the @samp{disassemble} command's address arguments are
10025 specified using expressions in your programming language
10026 (@pxref{Expressions, ,Expressions}), not location specs
10027 (@pxref{Location Specifications}). So, for example, if you want to
10028 disassemble function @code{bar} in file @file{foo.c}, you must type
10029 @samp{disassemble 'foo.c'::bar} and not @samp{disassemble foo.c:bar}.
10031 Some architectures have more than one commonly-used set of instruction
10032 mnemonics or other syntax.
10034 For programs that were dynamically linked and use shared libraries,
10035 instructions that call functions or branch to locations in the shared
10036 libraries might show a seemingly bogus location---it's actually a
10037 location of the relocation table. On some architectures, @value{GDBN}
10038 might be able to resolve these to actual function names.
10041 @kindex set disassembler-options
10042 @cindex disassembler options
10043 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
10044 This command controls the passing of target specific information to
10045 the disassembler. For a list of valid options, please refer to the
10046 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
10047 manual and/or the output of @kbd{objdump --help}
10048 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
10049 The default value is the empty string.
10051 If it is necessary to specify more than one disassembler option, then
10052 multiple options can be placed together into a comma separated list.
10053 Currently this command is only supported on targets ARC, ARM, MIPS,
10056 @kindex show disassembler-options
10057 @item show disassembler-options
10058 Show the current setting of the disassembler options.
10062 @kindex set disassembly-flavor
10063 @cindex Intel disassembly flavor
10064 @cindex AT&T disassembly flavor
10065 @item set disassembly-flavor @var{instruction-set}
10066 Select the instruction set to use when disassembling the
10067 program via the @code{disassemble} or @code{x/i} commands.
10069 Currently this command is only defined for the Intel x86 family. You
10070 can set @var{instruction-set} to either @code{intel} or @code{att}.
10071 The default is @code{att}, the AT&T flavor used by default by Unix
10072 assemblers for x86-based targets.
10074 @kindex show disassembly-flavor
10075 @item show disassembly-flavor
10076 Show the current setting of the disassembly flavor.
10080 @kindex set disassemble-next-line
10081 @kindex show disassemble-next-line
10082 @item set disassemble-next-line
10083 @itemx show disassemble-next-line
10084 Control whether or not @value{GDBN} will disassemble the next source
10085 line or instruction when execution stops. If ON, @value{GDBN} will
10086 display disassembly of the next source line when execution of the
10087 program being debugged stops. This is @emph{in addition} to
10088 displaying the source line itself, which @value{GDBN} always does if
10089 possible. If the next source line cannot be displayed for some reason
10090 (e.g., if @value{GDBN} cannot find the source file, or there's no line
10091 info in the debug info), @value{GDBN} will display disassembly of the
10092 next @emph{instruction} instead of showing the next source line. If
10093 AUTO, @value{GDBN} will display disassembly of next instruction only
10094 if the source line cannot be displayed. This setting causes
10095 @value{GDBN} to display some feedback when you step through a function
10096 with no line info or whose source file is unavailable. The default is
10097 OFF, which means never display the disassembly of the next line or
10101 @node Disable Reading Source
10102 @section Disable Reading Source Code
10103 @cindex source code, disable access
10105 In some cases it can be desirable to prevent @value{GDBN} from
10106 accessing source code files. One case where this might be desirable
10107 is if the source code files are located over a slow network
10110 The following command can be used to control whether @value{GDBN}
10111 should access source code files or not:
10114 @kindex set source open
10115 @kindex show source open
10116 @item set source open @r{[}on@r{|}off@r{]}
10117 @itemx show source open
10118 When this option is @code{on}, which is the default, @value{GDBN} will
10119 access source code files when needed, for example to print source
10120 lines when @value{GDBN} stops, or in response to the @code{list}
10123 When this option is @code{off}, @value{GDBN} will not access source
10128 @chapter Examining Data
10130 @cindex printing data
10131 @cindex examining data
10134 The usual way to examine data in your program is with the @code{print}
10135 command (abbreviated @code{p}), or its synonym @code{inspect}. It
10136 evaluates and prints the value of an expression of the language your
10137 program is written in (@pxref{Languages, ,Using @value{GDBN} with
10138 Different Languages}). It may also print the expression using a
10139 Python-based pretty-printer (@pxref{Pretty Printing}).
10142 @item print [[@var{options}] --] @var{expr}
10143 @itemx print [[@var{options}] --] /@var{f} @var{expr}
10144 @var{expr} is an expression (in the source language). By default the
10145 value of @var{expr} is printed in a format appropriate to its data type;
10146 you can choose a different format by specifying @samp{/@var{f}}, where
10147 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
10150 @anchor{print options}
10151 The @code{print} command supports a number of options that allow
10152 overriding relevant global print settings as set by @code{set print}
10156 @item -address [@code{on}|@code{off}]
10157 Set printing of addresses.
10158 Related setting: @ref{set print address}.
10160 @item -array [@code{on}|@code{off}]
10161 Pretty formatting of arrays.
10162 Related setting: @ref{set print array}.
10164 @item -array-indexes [@code{on}|@code{off}]
10165 Set printing of array indexes.
10166 Related setting: @ref{set print array-indexes}.
10168 @item -elements @var{number-of-elements}|@code{unlimited}
10169 Set limit on string chars or array elements to print. The value
10170 @code{unlimited} causes there to be no limit. Related setting:
10171 @ref{set print elements}.
10173 @item -max-depth @var{depth}|@code{unlimited}
10174 Set the threshold after which nested structures are replaced with
10175 ellipsis. Related setting: @ref{set print max-depth}.
10177 @item -nibbles [@code{on}|@code{off}]
10178 Set whether to print binary values in groups of four bits, known
10179 as ``nibbles''. @xref{set print nibbles}.
10181 @item -memory-tag-violations [@code{on}|@code{off}]
10182 Set printing of additional information about memory tag violations.
10183 @xref{set print memory-tag-violations}.
10185 @item -null-stop [@code{on}|@code{off}]
10186 Set printing of char arrays to stop at first null char. Related
10187 setting: @ref{set print null-stop}.
10189 @item -object [@code{on}|@code{off}]
10190 Set printing C@t{++} virtual function tables. Related setting:
10191 @ref{set print object}.
10193 @item -pretty [@code{on}|@code{off}]
10194 Set pretty formatting of structures. Related setting: @ref{set print
10197 @item -raw-values [@code{on}|@code{off}]
10198 Set whether to print values in raw form, bypassing any
10199 pretty-printers for that value. Related setting: @ref{set print
10202 @item -repeats @var{number-of-repeats}|@code{unlimited}
10203 Set threshold for repeated print elements. @code{unlimited} causes
10204 all elements to be individually printed. Related setting: @ref{set
10207 @item -static-members [@code{on}|@code{off}]
10208 Set printing C@t{++} static members. Related setting: @ref{set print
10211 @item -symbol [@code{on}|@code{off}]
10212 Set printing of symbol names when printing pointers. Related setting:
10213 @ref{set print symbol}.
10215 @item -union [@code{on}|@code{off}]
10216 Set printing of unions interior to structures. Related setting:
10217 @ref{set print union}.
10219 @item -vtbl [@code{on}|@code{off}]
10220 Set printing of C++ virtual function tables. Related setting:
10221 @ref{set print vtbl}.
10224 Because the @code{print} command accepts arbitrary expressions which
10225 may look like options (including abbreviations), if you specify any
10226 command option, then you must use a double dash (@code{--}) to mark
10227 the end of option processing.
10229 For example, this prints the value of the @code{-p} expression:
10232 (@value{GDBP}) print -p
10235 While this repeats the last value in the value history (see below)
10236 with the @code{-pretty} option in effect:
10239 (@value{GDBP}) print -p --
10242 Here is an example including both on option and an expression:
10246 (@value{GDBP}) print -pretty -- *myptr
10258 @item print [@var{options}]
10259 @itemx print [@var{options}] /@var{f}
10260 @cindex reprint the last value
10261 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10262 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10263 conveniently inspect the same value in an alternative format.
10266 If the architecture supports memory tagging, the @code{print} command will
10267 display pointer/memory tag mismatches if what is being printed is a pointer
10268 or reference type. @xref{Memory Tagging}.
10270 A more low-level way of examining data is with the @code{x} command.
10271 It examines data in memory at a specified address and prints it in a
10272 specified format. @xref{Memory, ,Examining Memory}.
10274 If you are interested in information about types, or about how the
10275 fields of a struct or a class are declared, use the @code{ptype @var{expr}}
10276 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10279 @cindex exploring hierarchical data structures
10281 Another way of examining values of expressions and type information is
10282 through the Python extension command @code{explore} (available only if
10283 the @value{GDBN} build is configured with @code{--with-python}). It
10284 offers an interactive way to start at the highest level (or, the most
10285 abstract level) of the data type of an expression (or, the data type
10286 itself) and explore all the way down to leaf scalar values/fields
10287 embedded in the higher level data types.
10290 @item explore @var{arg}
10291 @var{arg} is either an expression (in the source language), or a type
10292 visible in the current context of the program being debugged.
10295 The working of the @code{explore} command can be illustrated with an
10296 example. If a data type @code{struct ComplexStruct} is defined in your
10300 struct SimpleStruct
10306 struct ComplexStruct
10308 struct SimpleStruct *ss_p;
10314 followed by variable declarations as
10317 struct SimpleStruct ss = @{ 10, 1.11 @};
10318 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10322 then, the value of the variable @code{cs} can be explored using the
10323 @code{explore} command as follows.
10327 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10328 the following fields:
10330 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10331 arr = <Enter 1 to explore this field of type `int [10]'>
10333 Enter the field number of choice:
10337 Since the fields of @code{cs} are not scalar values, you are being
10338 prompted to chose the field you want to explore. Let's say you choose
10339 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10340 pointer, you will be asked if it is pointing to a single value. From
10341 the declaration of @code{cs} above, it is indeed pointing to a single
10342 value, hence you enter @code{y}. If you enter @code{n}, then you will
10343 be asked if it were pointing to an array of values, in which case this
10344 field will be explored as if it were an array.
10347 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10348 Continue exploring it as a pointer to a single value [y/n]: y
10349 The value of `*(cs.ss_p)' is a struct/class of type `struct
10350 SimpleStruct' with the following fields:
10352 i = 10 .. (Value of type `int')
10353 d = 1.1100000000000001 .. (Value of type `double')
10355 Press enter to return to parent value:
10359 If the field @code{arr} of @code{cs} was chosen for exploration by
10360 entering @code{1} earlier, then since it is as array, you will be
10361 prompted to enter the index of the element in the array that you want
10365 `cs.arr' is an array of `int'.
10366 Enter the index of the element you want to explore in `cs.arr': 5
10368 `(cs.arr)[5]' is a scalar value of type `int'.
10372 Press enter to return to parent value:
10375 In general, at any stage of exploration, you can go deeper towards the
10376 leaf values by responding to the prompts appropriately, or hit the
10377 return key to return to the enclosing data structure (the @i{higher}
10378 level data structure).
10380 Similar to exploring values, you can use the @code{explore} command to
10381 explore types. Instead of specifying a value (which is typically a
10382 variable name or an expression valid in the current context of the
10383 program being debugged), you specify a type name. If you consider the
10384 same example as above, your can explore the type
10385 @code{struct ComplexStruct} by passing the argument
10386 @code{struct ComplexStruct} to the @code{explore} command.
10389 (gdb) explore struct ComplexStruct
10393 By responding to the prompts appropriately in the subsequent interactive
10394 session, you can explore the type @code{struct ComplexStruct} in a
10395 manner similar to how the value @code{cs} was explored in the above
10398 The @code{explore} command also has two sub-commands,
10399 @code{explore value} and @code{explore type}. The former sub-command is
10400 a way to explicitly specify that value exploration of the argument is
10401 being invoked, while the latter is a way to explicitly specify that type
10402 exploration of the argument is being invoked.
10405 @item explore value @var{expr}
10406 @cindex explore value
10407 This sub-command of @code{explore} explores the value of the
10408 expression @var{expr} (if @var{expr} is an expression valid in the
10409 current context of the program being debugged). The behavior of this
10410 command is identical to that of the behavior of the @code{explore}
10411 command being passed the argument @var{expr}.
10413 @item explore type @var{arg}
10414 @cindex explore type
10415 This sub-command of @code{explore} explores the type of @var{arg} (if
10416 @var{arg} is a type visible in the current context of program being
10417 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10418 is an expression valid in the current context of the program being
10419 debugged). If @var{arg} is a type, then the behavior of this command is
10420 identical to that of the @code{explore} command being passed the
10421 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10422 this command will be identical to that of the @code{explore} command
10423 being passed the type of @var{arg} as the argument.
10427 * Expressions:: Expressions
10428 * Ambiguous Expressions:: Ambiguous Expressions
10429 * Variables:: Program variables
10430 * Arrays:: Artificial arrays
10431 * Output Formats:: Output formats
10432 * Memory:: Examining memory
10433 * Memory Tagging:: Memory Tagging
10434 * Auto Display:: Automatic display
10435 * Print Settings:: Print settings
10436 * Pretty Printing:: Python pretty printing
10437 * Value History:: Value history
10438 * Convenience Vars:: Convenience variables
10439 * Convenience Funs:: Convenience functions
10440 * Registers:: Registers
10441 * Floating Point Hardware:: Floating point hardware
10442 * Vector Unit:: Vector Unit
10443 * OS Information:: Auxiliary data provided by operating system
10444 * Memory Region Attributes:: Memory region attributes
10445 * Dump/Restore Files:: Copy between memory and a file
10446 * Core File Generation:: Cause a program dump its core
10447 * Character Sets:: Debugging programs that use a different
10448 character set than GDB does
10449 * Caching Target Data:: Data caching for targets
10450 * Searching Memory:: Searching memory for a sequence of bytes
10451 * Value Sizes:: Managing memory allocated for values
10455 @section Expressions
10457 @cindex expressions
10458 @code{print} and many other @value{GDBN} commands accept an expression and
10459 compute its value. Any kind of constant, variable or operator defined
10460 by the programming language you are using is valid in an expression in
10461 @value{GDBN}. This includes conditional expressions, function calls,
10462 casts, and string constants. It also includes preprocessor macros, if
10463 you compiled your program to include this information; see
10466 @cindex arrays in expressions
10467 @value{GDBN} supports array constants in expressions input by
10468 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10469 you can use the command @code{print @{1, 2, 3@}} to create an array
10470 of three integers. If you pass an array to a function or assign it
10471 to a program variable, @value{GDBN} copies the array to memory that
10472 is @code{malloc}ed in the target program.
10474 Because C is so widespread, most of the expressions shown in examples in
10475 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10476 Languages}, for information on how to use expressions in other
10479 In this section, we discuss operators that you can use in @value{GDBN}
10480 expressions regardless of your programming language.
10482 @cindex casts, in expressions
10483 Casts are supported in all languages, not just in C, because it is so
10484 useful to cast a number into a pointer in order to examine a structure
10485 at that address in memory.
10486 @c FIXME: casts supported---Mod2 true?
10488 @value{GDBN} supports these operators, in addition to those common
10489 to programming languages:
10493 @samp{@@} is a binary operator for treating parts of memory as arrays.
10494 @xref{Arrays, ,Artificial Arrays}, for more information.
10497 @samp{::} allows you to specify a variable in terms of the file or
10498 function where it is defined. @xref{Variables, ,Program Variables}.
10500 @cindex @{@var{type}@}
10501 @cindex type casting memory
10502 @cindex memory, viewing as typed object
10503 @cindex casts, to view memory
10504 @item @{@var{type}@} @var{addr}
10505 Refers to an object of type @var{type} stored at address @var{addr} in
10506 memory. The address @var{addr} may be any expression whose value is
10507 an integer or pointer (but parentheses are required around binary
10508 operators, just as in a cast). This construct is allowed regardless
10509 of what kind of data is normally supposed to reside at @var{addr}.
10512 @node Ambiguous Expressions
10513 @section Ambiguous Expressions
10514 @cindex ambiguous expressions
10516 Expressions can sometimes contain some ambiguous elements. For instance,
10517 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10518 a single function name to be defined several times, for application in
10519 different contexts. This is called @dfn{overloading}. Another example
10520 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10521 templates and is typically instantiated several times, resulting in
10522 the same function name being defined in different contexts.
10524 In some cases and depending on the language, it is possible to adjust
10525 the expression to remove the ambiguity. For instance in C@t{++}, you
10526 can specify the signature of the function you want to break on, as in
10527 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10528 qualified name of your function often makes the expression unambiguous
10531 When an ambiguity that needs to be resolved is detected, the debugger
10532 has the capability to display a menu of numbered choices for each
10533 possibility, and then waits for the selection with the prompt @samp{>}.
10534 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10535 aborts the current command. If the command in which the expression was
10536 used allows more than one choice to be selected, the next option in the
10537 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10540 For example, the following session excerpt shows an attempt to set a
10541 breakpoint at the overloaded symbol @code{String::after}.
10542 We choose three particular definitions of that function name:
10544 @c FIXME! This is likely to change to show arg type lists, at least
10547 (@value{GDBP}) b String::after
10550 [2] file:String.cc; line number:867
10551 [3] file:String.cc; line number:860
10552 [4] file:String.cc; line number:875
10553 [5] file:String.cc; line number:853
10554 [6] file:String.cc; line number:846
10555 [7] file:String.cc; line number:735
10557 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10558 Breakpoint 2 at 0xb344: file String.cc, line 875.
10559 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10560 Multiple breakpoints were set.
10561 Use the "delete" command to delete unwanted
10568 @kindex set multiple-symbols
10569 @item set multiple-symbols @var{mode}
10570 @cindex multiple-symbols menu
10572 This option allows you to adjust the debugger behavior when an expression
10575 By default, @var{mode} is set to @code{all}. If the command with which
10576 the expression is used allows more than one choice, then @value{GDBN}
10577 automatically selects all possible choices. For instance, inserting
10578 a breakpoint on a function using an ambiguous name results in a breakpoint
10579 inserted on each possible match. However, if a unique choice must be made,
10580 then @value{GDBN} uses the menu to help you disambiguate the expression.
10581 For instance, printing the address of an overloaded function will result
10582 in the use of the menu.
10584 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10585 when an ambiguity is detected.
10587 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10588 an error due to the ambiguity and the command is aborted.
10590 @kindex show multiple-symbols
10591 @item show multiple-symbols
10592 Show the current value of the @code{multiple-symbols} setting.
10596 @section Program Variables
10598 The most common kind of expression to use is the name of a variable
10601 Variables in expressions are understood in the selected stack frame
10602 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10606 global (or file-static)
10613 visible according to the scope rules of the
10614 programming language from the point of execution in that frame
10617 @noindent This means that in the function
10632 you can examine and use the variable @code{a} whenever your program is
10633 executing within the function @code{foo}, but you can only use or
10634 examine the variable @code{b} while your program is executing inside
10635 the block where @code{b} is declared.
10637 @cindex variable name conflict
10638 There is an exception: you can refer to a variable or function whose
10639 scope is a single source file even if the current execution point is not
10640 in this file. But it is possible to have more than one such variable or
10641 function with the same name (in different source files). If that
10642 happens, referring to that name has unpredictable effects. If you wish,
10643 you can specify a static variable in a particular function or file by
10644 using the colon-colon (@code{::}) notation:
10646 @cindex colon-colon, context for variables/functions
10648 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10649 @cindex @code{::}, context for variables/functions
10652 @var{file}::@var{variable}
10653 @var{function}::@var{variable}
10657 Here @var{file} or @var{function} is the name of the context for the
10658 static @var{variable}. In the case of file names, you can use quotes to
10659 make sure @value{GDBN} parses the file name as a single word---for example,
10660 to print a global value of @code{x} defined in @file{f2.c}:
10663 (@value{GDBP}) p 'f2.c'::x
10666 The @code{::} notation is normally used for referring to
10667 static variables, since you typically disambiguate uses of local variables
10668 in functions by selecting the appropriate frame and using the
10669 simple name of the variable. However, you may also use this notation
10670 to refer to local variables in frames enclosing the selected frame:
10679 process (a); /* Stop here */
10690 For example, if there is a breakpoint at the commented line,
10691 here is what you might see
10692 when the program stops after executing the call @code{bar(0)}:
10697 (@value{GDBP}) p bar::a
10699 (@value{GDBP}) up 2
10700 #2 0x080483d0 in foo (a=5) at foobar.c:12
10703 (@value{GDBP}) p bar::a
10707 @cindex C@t{++} scope resolution
10708 These uses of @samp{::} are very rarely in conflict with the very
10709 similar use of the same notation in C@t{++}. When they are in
10710 conflict, the C@t{++} meaning takes precedence; however, this can be
10711 overridden by quoting the file or function name with single quotes.
10713 For example, suppose the program is stopped in a method of a class
10714 that has a field named @code{includefile}, and there is also an
10715 include file named @file{includefile} that defines a variable,
10716 @code{some_global}.
10719 (@value{GDBP}) p includefile
10721 (@value{GDBP}) p includefile::some_global
10722 A syntax error in expression, near `'.
10723 (@value{GDBP}) p 'includefile'::some_global
10727 @cindex wrong values
10728 @cindex variable values, wrong
10729 @cindex function entry/exit, wrong values of variables
10730 @cindex optimized code, wrong values of variables
10732 @emph{Warning:} Occasionally, a local variable may appear to have the
10733 wrong value at certain points in a function---just after entry to a new
10734 scope, and just before exit.
10736 You may see this problem when you are stepping by machine instructions.
10737 This is because, on most machines, it takes more than one instruction to
10738 set up a stack frame (including local variable definitions); if you are
10739 stepping by machine instructions, variables may appear to have the wrong
10740 values until the stack frame is completely built. On exit, it usually
10741 also takes more than one machine instruction to destroy a stack frame;
10742 after you begin stepping through that group of instructions, local
10743 variable definitions may be gone.
10745 This may also happen when the compiler does significant optimizations.
10746 To be sure of always seeing accurate values, turn off all optimization
10749 @cindex ``No symbol "foo" in current context''
10750 Another possible effect of compiler optimizations is to optimize
10751 unused variables out of existence, or assign variables to registers (as
10752 opposed to memory addresses). Depending on the support for such cases
10753 offered by the debug info format used by the compiler, @value{GDBN}
10754 might not be able to display values for such local variables. If that
10755 happens, @value{GDBN} will print a message like this:
10758 No symbol "foo" in current context.
10761 To solve such problems, either recompile without optimizations, or use a
10762 different debug info format, if the compiler supports several such
10763 formats. @xref{Compilation}, for more information on choosing compiler
10764 options. @xref{C, ,C and C@t{++}}, for more information about debug
10765 info formats that are best suited to C@t{++} programs.
10767 If you ask to print an object whose contents are unknown to
10768 @value{GDBN}, e.g., because its data type is not completely specified
10769 by the debug information, @value{GDBN} will say @samp{<incomplete
10770 type>}. @xref{Symbols, incomplete type}, for more about this.
10772 @cindex no debug info variables
10773 If you try to examine or use the value of a (global) variable for
10774 which @value{GDBN} has no type information, e.g., because the program
10775 includes no debug information, @value{GDBN} displays an error message.
10776 @xref{Symbols, unknown type}, for more about unknown types. If you
10777 cast the variable to its declared type, @value{GDBN} gets the
10778 variable's value using the cast-to type as the variable's type. For
10779 example, in a C program:
10782 (@value{GDBP}) p var
10783 'var' has unknown type; cast it to its declared type
10784 (@value{GDBP}) p (float) var
10788 If you append @kbd{@@entry} string to a function parameter name you get its
10789 value at the time the function got called. If the value is not available an
10790 error message is printed. Entry values are available only with some compilers.
10791 Entry values are normally also printed at the function parameter list according
10792 to @ref{set print entry-values}.
10795 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10801 (gdb) print i@@entry
10805 Strings are identified as arrays of @code{char} values without specified
10806 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10807 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10808 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10809 defines literal string type @code{"char"} as @code{char} without a sign.
10814 signed char var1[] = "A";
10817 You get during debugging
10822 $2 = @{65 'A', 0 '\0'@}
10826 @section Artificial Arrays
10828 @cindex artificial array
10830 @kindex @@@r{, referencing memory as an array}
10831 It is often useful to print out several successive objects of the
10832 same type in memory; a section of an array, or an array of
10833 dynamically determined size for which only a pointer exists in the
10836 You can do this by referring to a contiguous span of memory as an
10837 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10838 operand of @samp{@@} should be the first element of the desired array
10839 and be an individual object. The right operand should be the desired length
10840 of the array. The result is an array value whose elements are all of
10841 the type of the left argument. The first element is actually the left
10842 argument; the second element comes from bytes of memory immediately
10843 following those that hold the first element, and so on. Here is an
10844 example. If a program says
10847 int *array = (int *) malloc (len * sizeof (int));
10851 you can print the contents of @code{array} with
10857 The left operand of @samp{@@} must reside in memory. Array values made
10858 with @samp{@@} in this way behave just like other arrays in terms of
10859 subscripting, and are coerced to pointers when used in expressions.
10860 Artificial arrays most often appear in expressions via the value history
10861 (@pxref{Value History, ,Value History}), after printing one out.
10863 Another way to create an artificial array is to use a cast.
10864 This re-interprets a value as if it were an array.
10865 The value need not be in memory:
10867 (@value{GDBP}) p/x (short[2])0x12345678
10868 $1 = @{0x1234, 0x5678@}
10871 As a convenience, if you leave the array length out (as in
10872 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10873 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10875 (@value{GDBP}) p/x (short[])0x12345678
10876 $2 = @{0x1234, 0x5678@}
10879 Sometimes the artificial array mechanism is not quite enough; in
10880 moderately complex data structures, the elements of interest may not
10881 actually be adjacent---for example, if you are interested in the values
10882 of pointers in an array. One useful work-around in this situation is
10883 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10884 Variables}) as a counter in an expression that prints the first
10885 interesting value, and then repeat that expression via @key{RET}. For
10886 instance, suppose you have an array @code{dtab} of pointers to
10887 structures, and you are interested in the values of a field @code{fv}
10888 in each structure. Here is an example of what you might type:
10898 @node Output Formats
10899 @section Output Formats
10901 @cindex formatted output
10902 @cindex output formats
10903 By default, @value{GDBN} prints a value according to its data type. Sometimes
10904 this is not what you want. For example, you might want to print a number
10905 in hex, or a pointer in decimal. Or you might want to view data in memory
10906 at a certain address as a character string or as an instruction. To do
10907 these things, specify an @dfn{output format} when you print a value.
10909 The simplest use of output formats is to say how to print a value
10910 already computed. This is done by starting the arguments of the
10911 @code{print} command with a slash and a format letter. The format
10912 letters supported are:
10916 Print the binary representation of the value in hexadecimal.
10919 Print the binary representation of the value in decimal.
10922 Print the binary representation of the value as an decimal, as if it
10926 Print the binary representation of the value in octal.
10929 Print the binary representation of the value in binary. The letter
10930 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
10931 because these format letters are also used with the @code{x} command,
10932 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
10936 @cindex unknown address, locating
10937 @cindex locate address
10938 Print as an address, both absolute in hexadecimal and as an offset from
10939 the nearest preceding symbol. You can use this format used to discover
10940 where (in what function) an unknown address is located:
10943 (@value{GDBP}) p/a 0x54320
10944 $3 = 0x54320 <_initialize_vx+396>
10948 The command @code{info symbol 0x54320} yields similar results.
10949 @xref{Symbols, info symbol}.
10952 Cast the value to an integer (unlike other formats, this does not just
10953 reinterpret the underlying bits) and print it as a character constant.
10954 This prints both the numerical value and its character representation.
10955 The character representation is replaced with the octal escape
10956 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
10958 Without this format, @value{GDBN} displays @code{char},
10959 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10960 constants. Single-byte members of vectors are displayed as integer
10964 Regard the bits of the value as a floating point number and print
10965 using typical floating point syntax.
10968 @cindex printing strings
10969 @cindex printing byte arrays
10970 Regard as a string, if possible. With this format, pointers to single-byte
10971 data are displayed as null-terminated strings and arrays of single-byte data
10972 are displayed as fixed-length strings. Other values are displayed in their
10975 Without this format, @value{GDBN} displays pointers to and arrays of
10976 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10977 strings. Single-byte members of a vector are displayed as an integer
10981 Like @samp{x} formatting, the value is treated as an integer and
10982 printed as hexadecimal, but leading zeros are printed to pad the value
10983 to the size of the integer type.
10986 @cindex raw printing
10987 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10988 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10989 Printing}). This typically results in a higher-level display of the
10990 value's contents. The @samp{r} format bypasses any Python
10991 pretty-printer which might exist.
10994 For example, to print the program counter in hex (@pxref{Registers}), type
11001 Note that no space is required before the slash; this is because command
11002 names in @value{GDBN} cannot contain a slash.
11004 To reprint the last value in the value history with a different format,
11005 you can use the @code{print} command with just a format and no
11006 expression. For example, @samp{p/x} reprints the last value in hex.
11009 @section Examining Memory
11011 You can use the command @code{x} (for ``examine'') to examine memory in
11012 any of several formats, independently of your program's data types.
11014 @cindex examining memory
11016 @kindex x @r{(examine memory)}
11017 @item x/@var{nfu} @var{addr}
11018 @itemx x @var{addr}
11020 Use the @code{x} command to examine memory.
11023 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
11024 much memory to display and how to format it; @var{addr} is an
11025 expression giving the address where you want to start displaying memory.
11026 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
11027 Several commands set convenient defaults for @var{addr}.
11030 @item @var{n}, the repeat count
11031 The repeat count is a decimal integer; the default is 1. It specifies
11032 how much memory (counting by units @var{u}) to display. If a negative
11033 number is specified, memory is examined backward from @var{addr}.
11034 @c This really is **decimal**; unaffected by 'set radix' as of GDB
11037 @item @var{f}, the display format
11038 The display format is one of the formats used by @code{print}
11039 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
11040 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
11041 @samp{m} (for displaying memory tags).
11042 The default is @samp{x} (hexadecimal) initially. The default changes
11043 each time you use either @code{x} or @code{print}.
11045 @item @var{u}, the unit size
11046 The unit size is any of
11052 Halfwords (two bytes).
11054 Words (four bytes). This is the initial default.
11056 Giant words (eight bytes).
11059 Each time you specify a unit size with @code{x}, that size becomes the
11060 default unit the next time you use @code{x}. For the @samp{i} format,
11061 the unit size is ignored and is normally not written. For the @samp{s} format,
11062 the unit size defaults to @samp{b}, unless it is explicitly given.
11063 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
11064 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
11065 Note that the results depend on the programming language of the
11066 current compilation unit. If the language is C, the @samp{s}
11067 modifier will use the UTF-16 encoding while @samp{w} will use
11068 UTF-32. The encoding is set by the programming language and cannot
11071 @item @var{addr}, starting display address
11072 @var{addr} is the address where you want @value{GDBN} to begin displaying
11073 memory. The expression need not have a pointer value (though it may);
11074 it is always interpreted as an integer address of a byte of memory.
11075 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
11076 @var{addr} is usually just after the last address examined---but several
11077 other commands also set the default address: @code{info breakpoints} (to
11078 the address of the last breakpoint listed), @code{info line} (to the
11079 starting address of a line), and @code{print} (if you use it to display
11080 a value from memory).
11083 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
11084 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
11085 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
11086 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
11087 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
11089 You can also specify a negative repeat count to examine memory backward
11090 from the given address. For example, @samp{x/-3uh 0x54320} prints three
11091 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
11093 Since the letters indicating unit sizes are all distinct from the
11094 letters specifying output formats, you do not have to remember whether
11095 unit size or format comes first; either order works. The output
11096 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
11097 (However, the count @var{n} must come first; @samp{wx4} does not work.)
11099 Even though the unit size @var{u} is ignored for the formats @samp{s}
11100 and @samp{i}, you might still want to use a count @var{n}; for example,
11101 @samp{3i} specifies that you want to see three machine instructions,
11102 including any operands. For convenience, especially when used with
11103 the @code{display} command, the @samp{i} format also prints branch delay
11104 slot instructions, if any, beyond the count specified, which immediately
11105 follow the last instruction that is within the count. The command
11106 @code{disassemble} gives an alternative way of inspecting machine
11107 instructions; see @ref{Machine Code,,Source and Machine Code}.
11109 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
11110 the command displays null-terminated strings or instructions before the given
11111 address as many as the absolute value of the given number. For the @samp{i}
11112 format, we use line number information in the debug info to accurately locate
11113 instruction boundaries while disassembling backward. If line info is not
11114 available, the command stops examining memory with an error message.
11116 All the defaults for the arguments to @code{x} are designed to make it
11117 easy to continue scanning memory with minimal specifications each time
11118 you use @code{x}. For example, after you have inspected three machine
11119 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
11120 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
11121 the repeat count @var{n} is used again; the other arguments default as
11122 for successive uses of @code{x}.
11124 When examining machine instructions, the instruction at current program
11125 counter is shown with a @code{=>} marker. For example:
11128 (@value{GDBP}) x/5i $pc-6
11129 0x804837f <main+11>: mov %esp,%ebp
11130 0x8048381 <main+13>: push %ecx
11131 0x8048382 <main+14>: sub $0x4,%esp
11132 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
11133 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
11136 If the architecture supports memory tagging, the tags can be displayed by
11137 using @samp{m}. @xref{Memory Tagging}.
11139 The information will be displayed once per granule size
11140 (the amount of bytes a particular memory tag covers). For example, AArch64
11141 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
11143 Due to the way @value{GDBN} prints information with the @code{x} command (not
11144 aligned to a particular boundary), the tag information will refer to the
11145 initial address displayed on a particular line. If a memory tag boundary
11146 is crossed in the middle of a line displayed by the @code{x} command, it
11147 will be displayed on the next line.
11149 The @samp{m} format doesn't affect any other specified formats that were
11150 passed to the @code{x} command.
11152 @cindex @code{$_}, @code{$__}, and value history
11153 The addresses and contents printed by the @code{x} command are not saved
11154 in the value history because there is often too much of them and they
11155 would get in the way. Instead, @value{GDBN} makes these values available for
11156 subsequent use in expressions as values of the convenience variables
11157 @code{$_} and @code{$__}. After an @code{x} command, the last address
11158 examined is available for use in expressions in the convenience variable
11159 @code{$_}. The contents of that address, as examined, are available in
11160 the convenience variable @code{$__}.
11162 If the @code{x} command has a repeat count, the address and contents saved
11163 are from the last memory unit printed; this is not the same as the last
11164 address printed if several units were printed on the last line of output.
11166 @anchor{addressable memory unit}
11167 @cindex addressable memory unit
11168 Most targets have an addressable memory unit size of 8 bits. This means
11169 that to each memory address are associated 8 bits of data. Some
11170 targets, however, have other addressable memory unit sizes.
11171 Within @value{GDBN} and this document, the term
11172 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11173 when explicitly referring to a chunk of data of that size. The word
11174 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11175 the addressable memory unit size of the target. For most systems,
11176 addressable memory unit is a synonym of byte.
11178 @cindex remote memory comparison
11179 @cindex target memory comparison
11180 @cindex verify remote memory image
11181 @cindex verify target memory image
11182 When you are debugging a program running on a remote target machine
11183 (@pxref{Remote Debugging}), you may wish to verify the program's image
11184 in the remote machine's memory against the executable file you
11185 downloaded to the target. Or, on any target, you may want to check
11186 whether the program has corrupted its own read-only sections. The
11187 @code{compare-sections} command is provided for such situations.
11190 @kindex compare-sections
11191 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11192 Compare the data of a loadable section @var{section-name} in the
11193 executable file of the program being debugged with the same section in
11194 the target machine's memory, and report any mismatches. With no
11195 arguments, compares all loadable sections. With an argument of
11196 @code{-r}, compares all loadable read-only sections.
11198 Note: for remote targets, this command can be accelerated if the
11199 target supports computing the CRC checksum of a block of memory
11200 (@pxref{qCRC packet}).
11203 @node Memory Tagging
11204 @section Memory Tagging
11206 Memory tagging is a memory protection technology that uses a pair of tags to
11207 validate memory accesses through pointers. The tags are integer values
11208 usually comprised of a few bits, depending on the architecture.
11210 There are two types of tags that are used in this setup: logical and
11211 allocation. A logical tag is stored in the pointers themselves, usually at the
11212 higher bits of the pointers. An allocation tag is the tag associated
11213 with particular ranges of memory in the physical address space, against which
11214 the logical tags from pointers are compared.
11216 The pointer tag (logical tag) must match the memory tag (allocation tag)
11217 for the memory access to be valid. If the logical tag does not match the
11218 allocation tag, that will raise a memory violation.
11220 Allocation tags cover multiple contiguous bytes of physical memory. This
11221 range of bytes is called a memory tag granule and is architecture-specific.
11222 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11223 tag spans 16 bytes of memory.
11225 If the underlying architecture supports memory tagging, like AArch64 MTE
11226 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11227 against memory allocation tags.
11229 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11230 display tag information when appropriate, and a command prefix of
11231 @code{memory-tag} gives access to the various memory tagging commands.
11233 The @code{memory-tag} commands are the following:
11236 @kindex memory-tag print-logical-tag
11237 @item memory-tag print-logical-tag @var{pointer_expression}
11238 Print the logical tag stored in @var{pointer_expression}.
11239 @kindex memory-tag with-logical-tag
11240 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11241 Print the pointer given by @var{pointer_expression}, augmented with a logical
11242 tag of @var{tag_bytes}.
11243 @kindex memory-tag print-allocation-tag
11244 @item memory-tag print-allocation-tag @var{address_expression}
11245 Print the allocation tag associated with the memory address given by
11246 @var{address_expression}.
11247 @kindex memory-tag setatag
11248 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11249 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11250 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11251 @kindex memory-tag check
11252 @item memory-tag check @var{pointer_expression}
11253 Check if the logical tag in the pointer given by @var{pointer_expression}
11254 matches the allocation tag for the memory referenced by the pointer.
11256 This essentially emulates the hardware validation that is done when tagged
11257 memory is accessed through a pointer, but does not cause a memory fault as
11258 it would during hardware validation.
11260 It can be used to inspect potential memory tagging violations in the running
11261 process, before any faults get triggered.
11265 @section Automatic Display
11266 @cindex automatic display
11267 @cindex display of expressions
11269 If you find that you want to print the value of an expression frequently
11270 (to see how it changes), you might want to add it to the @dfn{automatic
11271 display list} so that @value{GDBN} prints its value each time your program stops.
11272 Each expression added to the list is given a number to identify it;
11273 to remove an expression from the list, you specify that number.
11274 The automatic display looks like this:
11278 3: bar[5] = (struct hack *) 0x3804
11282 This display shows item numbers, expressions and their current values. As with
11283 displays you request manually using @code{x} or @code{print}, you can
11284 specify the output format you prefer; in fact, @code{display} decides
11285 whether to use @code{print} or @code{x} depending your format
11286 specification---it uses @code{x} if you specify either the @samp{i}
11287 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11291 @item display @var{expr}
11292 Add the expression @var{expr} to the list of expressions to display
11293 each time your program stops. @xref{Expressions, ,Expressions}.
11295 @code{display} does not repeat if you press @key{RET} again after using it.
11297 @item display/@var{fmt} @var{expr}
11298 For @var{fmt} specifying only a display format and not a size or
11299 count, add the expression @var{expr} to the auto-display list but
11300 arrange to display it each time in the specified format @var{fmt}.
11301 @xref{Output Formats,,Output Formats}.
11303 @item display/@var{fmt} @var{addr}
11304 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11305 number of units, add the expression @var{addr} as a memory address to
11306 be examined each time your program stops. Examining means in effect
11307 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11310 For example, @samp{display/i $pc} can be helpful, to see the machine
11311 instruction about to be executed each time execution stops (@samp{$pc}
11312 is a common name for the program counter; @pxref{Registers, ,Registers}).
11315 @kindex delete display
11317 @item undisplay @var{dnums}@dots{}
11318 @itemx delete display @var{dnums}@dots{}
11319 Remove items from the list of expressions to display. Specify the
11320 numbers of the displays that you want affected with the command
11321 argument @var{dnums}. It can be a single display number, one of the
11322 numbers shown in the first field of the @samp{info display} display;
11323 or it could be a range of display numbers, as in @code{2-4}.
11325 @code{undisplay} does not repeat if you press @key{RET} after using it.
11326 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11328 @kindex disable display
11329 @item disable display @var{dnums}@dots{}
11330 Disable the display of item numbers @var{dnums}. A disabled display
11331 item is not printed automatically, but is not forgotten. It may be
11332 enabled again later. Specify the numbers of the displays that you
11333 want affected with the command argument @var{dnums}. It can be a
11334 single display number, one of the numbers shown in the first field of
11335 the @samp{info display} display; or it could be a range of display
11336 numbers, as in @code{2-4}.
11338 @kindex enable display
11339 @item enable display @var{dnums}@dots{}
11340 Enable display of item numbers @var{dnums}. It becomes effective once
11341 again in auto display of its expression, until you specify otherwise.
11342 Specify the numbers of the displays that you want affected with the
11343 command argument @var{dnums}. It can be a single display number, one
11344 of the numbers shown in the first field of the @samp{info display}
11345 display; or it could be a range of display numbers, as in @code{2-4}.
11348 Display the current values of the expressions on the list, just as is
11349 done when your program stops.
11351 @kindex info display
11353 Print the list of expressions previously set up to display
11354 automatically, each one with its item number, but without showing the
11355 values. This includes disabled expressions, which are marked as such.
11356 It also includes expressions which would not be displayed right now
11357 because they refer to automatic variables not currently available.
11360 @cindex display disabled out of scope
11361 If a display expression refers to local variables, then it does not make
11362 sense outside the lexical context for which it was set up. Such an
11363 expression is disabled when execution enters a context where one of its
11364 variables is not defined. For example, if you give the command
11365 @code{display last_char} while inside a function with an argument
11366 @code{last_char}, @value{GDBN} displays this argument while your program
11367 continues to stop inside that function. When it stops elsewhere---where
11368 there is no variable @code{last_char}---the display is disabled
11369 automatically. The next time your program stops where @code{last_char}
11370 is meaningful, you can enable the display expression once again.
11372 @node Print Settings
11373 @section Print Settings
11375 @cindex format options
11376 @cindex print settings
11377 @value{GDBN} provides the following ways to control how arrays, structures,
11378 and symbols are printed.
11381 These settings are useful for debugging programs in any language:
11385 @anchor{set print address}
11386 @item set print address
11387 @itemx set print address on
11388 @cindex print/don't print memory addresses
11389 @value{GDBN} prints memory addresses showing the location of stack
11390 traces, structure values, pointer values, breakpoints, and so forth,
11391 even when it also displays the contents of those addresses. The default
11392 is @code{on}. For example, this is what a stack frame display looks like with
11393 @code{set print address on}:
11398 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11400 530 if (lquote != def_lquote)
11404 @item set print address off
11405 Do not print addresses when displaying their contents. For example,
11406 this is the same stack frame displayed with @code{set print address off}:
11410 (@value{GDBP}) set print addr off
11412 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11413 530 if (lquote != def_lquote)
11417 You can use @samp{set print address off} to eliminate all machine
11418 dependent displays from the @value{GDBN} interface. For example, with
11419 @code{print address off}, you should get the same text for backtraces on
11420 all machines---whether or not they involve pointer arguments.
11423 @item show print address
11424 Show whether or not addresses are to be printed.
11427 When @value{GDBN} prints a symbolic address, it normally prints the
11428 closest earlier symbol plus an offset. If that symbol does not uniquely
11429 identify the address (for example, it is a name whose scope is a single
11430 source file), you may need to clarify. One way to do this is with
11431 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11432 you can set @value{GDBN} to print the source file and line number when
11433 it prints a symbolic address:
11436 @item set print symbol-filename on
11437 @cindex source file and line of a symbol
11438 @cindex symbol, source file and line
11439 Tell @value{GDBN} to print the source file name and line number of a
11440 symbol in the symbolic form of an address.
11442 @item set print symbol-filename off
11443 Do not print source file name and line number of a symbol. This is the
11446 @item show print symbol-filename
11447 Show whether or not @value{GDBN} will print the source file name and
11448 line number of a symbol in the symbolic form of an address.
11451 Another situation where it is helpful to show symbol filenames and line
11452 numbers is when disassembling code; @value{GDBN} shows you the line
11453 number and source file that corresponds to each instruction.
11455 Also, you may wish to see the symbolic form only if the address being
11456 printed is reasonably close to the closest earlier symbol:
11459 @item set print max-symbolic-offset @var{max-offset}
11460 @itemx set print max-symbolic-offset unlimited
11461 @cindex maximum value for offset of closest symbol
11462 Tell @value{GDBN} to only display the symbolic form of an address if the
11463 offset between the closest earlier symbol and the address is less than
11464 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11465 to always print the symbolic form of an address if any symbol precedes
11466 it. Zero is equivalent to @code{unlimited}.
11468 @item show print max-symbolic-offset
11469 Ask how large the maximum offset is that @value{GDBN} prints in a
11473 @cindex wild pointer, interpreting
11474 @cindex pointer, finding referent
11475 If you have a pointer and you are not sure where it points, try
11476 @samp{set print symbol-filename on}. Then you can determine the name
11477 and source file location of the variable where it points, using
11478 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11479 For example, here @value{GDBN} shows that a variable @code{ptt} points
11480 at another variable @code{t}, defined in @file{hi2.c}:
11483 (@value{GDBP}) set print symbol-filename on
11484 (@value{GDBP}) p/a ptt
11485 $4 = 0xe008 <t in hi2.c>
11489 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11490 does not show the symbol name and filename of the referent, even with
11491 the appropriate @code{set print} options turned on.
11494 You can also enable @samp{/a}-like formatting all the time using
11495 @samp{set print symbol on}:
11497 @anchor{set print symbol}
11499 @item set print symbol on
11500 Tell @value{GDBN} to print the symbol corresponding to an address, if
11503 @item set print symbol off
11504 Tell @value{GDBN} not to print the symbol corresponding to an
11505 address. In this mode, @value{GDBN} will still print the symbol
11506 corresponding to pointers to functions. This is the default.
11508 @item show print symbol
11509 Show whether @value{GDBN} will display the symbol corresponding to an
11513 Other settings control how different kinds of objects are printed:
11516 @anchor{set print array}
11517 @item set print array
11518 @itemx set print array on
11519 @cindex pretty print arrays
11520 Pretty print arrays. This format is more convenient to read,
11521 but uses more space. The default is off.
11523 @item set print array off
11524 Return to compressed format for arrays.
11526 @item show print array
11527 Show whether compressed or pretty format is selected for displaying
11530 @cindex print array indexes
11531 @anchor{set print array-indexes}
11532 @item set print array-indexes
11533 @itemx set print array-indexes on
11534 Print the index of each element when displaying arrays. May be more
11535 convenient to locate a given element in the array or quickly find the
11536 index of a given element in that printed array. The default is off.
11538 @item set print array-indexes off
11539 Stop printing element indexes when displaying arrays.
11541 @item show print array-indexes
11542 Show whether the index of each element is printed when displaying
11545 @anchor{set print nibbles}
11546 @item set print nibbles
11547 @itemx set print nibbles on
11548 @cindex print binary values in groups of four bits
11549 Print binary values in groups of four bits, known as @dfn{nibbles},
11550 when using the print command of @value{GDBN} with the option @samp{/t}.
11551 For example, this is what it looks like with @code{set print nibbles on}:
11555 (@value{GDBP}) print val_flags
11557 (@value{GDBP}) print/t val_flags
11558 $2 = 0100 1100 1110
11562 @item set print nibbles off
11563 Don't printing binary values in groups. This is the default.
11565 @item show print nibbles
11566 Show whether to print binary values in groups of four bits.
11568 @anchor{set print elements}
11569 @item set print elements @var{number-of-elements}
11570 @itemx set print elements unlimited
11571 @cindex number of array elements to print
11572 @cindex limit on number of printed array elements
11573 Set a limit on how many elements of an array @value{GDBN} will print.
11574 If @value{GDBN} is printing a large array, it stops printing after it has
11575 printed the number of elements set by the @code{set print elements} command.
11576 This limit also applies to the display of strings.
11577 When @value{GDBN} starts, this limit is set to 200.
11578 Setting @var{number-of-elements} to @code{unlimited} or zero means
11579 that the number of elements to print is unlimited.
11581 @item show print elements
11582 Display the number of elements of a large array that @value{GDBN} will print.
11584 @anchor{set print frame-arguments}
11585 @item set print frame-arguments @var{value}
11586 @kindex set print frame-arguments
11587 @cindex printing frame argument values
11588 @cindex print all frame argument values
11589 @cindex print frame argument values for scalars only
11590 @cindex do not print frame arguments
11591 This command allows to control how the values of arguments are printed
11592 when the debugger prints a frame (@pxref{Frames}). The possible
11597 The values of all arguments are printed.
11600 Print the value of an argument only if it is a scalar. The value of more
11601 complex arguments such as arrays, structures, unions, etc, is replaced
11602 by @code{@dots{}}. This is the default. Here is an example where
11603 only scalar arguments are shown:
11606 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11611 None of the argument values are printed. Instead, the value of each argument
11612 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11615 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11620 Only the presence of arguments is indicated by @code{@dots{}}.
11621 The @code{@dots{}} are not printed for function without any arguments.
11622 None of the argument names and values are printed.
11623 In this case, the example above now becomes:
11626 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11631 By default, only scalar arguments are printed. This command can be used
11632 to configure the debugger to print the value of all arguments, regardless
11633 of their type. However, it is often advantageous to not print the value
11634 of more complex parameters. For instance, it reduces the amount of
11635 information printed in each frame, making the backtrace more readable.
11636 Also, it improves performance when displaying Ada frames, because
11637 the computation of large arguments can sometimes be CPU-intensive,
11638 especially in large applications. Setting @code{print frame-arguments}
11639 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11640 this computation, thus speeding up the display of each Ada frame.
11642 @item show print frame-arguments
11643 Show how the value of arguments should be displayed when printing a frame.
11645 @anchor{set print raw-frame-arguments}
11646 @item set print raw-frame-arguments on
11647 Print frame arguments in raw, non pretty-printed, form.
11649 @item set print raw-frame-arguments off
11650 Print frame arguments in pretty-printed form, if there is a pretty-printer
11651 for the value (@pxref{Pretty Printing}),
11652 otherwise print the value in raw form.
11653 This is the default.
11655 @item show print raw-frame-arguments
11656 Show whether to print frame arguments in raw form.
11658 @anchor{set print entry-values}
11659 @item set print entry-values @var{value}
11660 @kindex set print entry-values
11661 Set printing of frame argument values at function entry. In some cases
11662 @value{GDBN} can determine the value of function argument which was passed by
11663 the function caller, even if the value was modified inside the called function
11664 and therefore is different. With optimized code, the current value could be
11665 unavailable, but the entry value may still be known.
11667 The default value is @code{default} (see below for its description). Older
11668 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11669 this feature will behave in the @code{default} setting the same way as with the
11672 This functionality is currently supported only by DWARF 2 debugging format and
11673 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11674 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11677 The @var{value} parameter can be one of the following:
11681 Print only actual parameter values, never print values from function entry
11685 #0 different (val=6)
11686 #0 lost (val=<optimized out>)
11688 #0 invalid (val=<optimized out>)
11692 Print only parameter values from function entry point. The actual parameter
11693 values are never printed.
11695 #0 equal (val@@entry=5)
11696 #0 different (val@@entry=5)
11697 #0 lost (val@@entry=5)
11698 #0 born (val@@entry=<optimized out>)
11699 #0 invalid (val@@entry=<optimized out>)
11703 Print only parameter values from function entry point. If value from function
11704 entry point is not known while the actual value is known, print the actual
11705 value for such parameter.
11707 #0 equal (val@@entry=5)
11708 #0 different (val@@entry=5)
11709 #0 lost (val@@entry=5)
11711 #0 invalid (val@@entry=<optimized out>)
11715 Print actual parameter values. If actual parameter value is not known while
11716 value from function entry point is known, print the entry point value for such
11720 #0 different (val=6)
11721 #0 lost (val@@entry=5)
11723 #0 invalid (val=<optimized out>)
11727 Always print both the actual parameter value and its value from function entry
11728 point, even if values of one or both are not available due to compiler
11731 #0 equal (val=5, val@@entry=5)
11732 #0 different (val=6, val@@entry=5)
11733 #0 lost (val=<optimized out>, val@@entry=5)
11734 #0 born (val=10, val@@entry=<optimized out>)
11735 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11739 Print the actual parameter value if it is known and also its value from
11740 function entry point if it is known. If neither is known, print for the actual
11741 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11742 values are known and identical, print the shortened
11743 @code{param=param@@entry=VALUE} notation.
11745 #0 equal (val=val@@entry=5)
11746 #0 different (val=6, val@@entry=5)
11747 #0 lost (val@@entry=5)
11749 #0 invalid (val=<optimized out>)
11753 Always print the actual parameter value. Print also its value from function
11754 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11755 if both values are known and identical, print the shortened
11756 @code{param=param@@entry=VALUE} notation.
11758 #0 equal (val=val@@entry=5)
11759 #0 different (val=6, val@@entry=5)
11760 #0 lost (val=<optimized out>, val@@entry=5)
11762 #0 invalid (val=<optimized out>)
11766 For analysis messages on possible failures of frame argument values at function
11767 entry resolution see @ref{set debug entry-values}.
11769 @item show print entry-values
11770 Show the method being used for printing of frame argument values at function
11773 @anchor{set print frame-info}
11774 @item set print frame-info @var{value}
11775 @kindex set print frame-info
11776 @cindex printing frame information
11777 @cindex frame information, printing
11778 This command allows to control the information printed when
11779 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11780 for a general explanation about frames and frame information.
11781 Note that some other settings (such as @code{set print frame-arguments}
11782 and @code{set print address}) are also influencing if and how some frame
11783 information is displayed. In particular, the frame program counter is never
11784 printed if @code{set print address} is off.
11786 The possible values for @code{set print frame-info} are:
11788 @item short-location
11789 Print the frame level, the program counter (if not at the
11790 beginning of the location source line), the function, the function
11793 Same as @code{short-location} but also print the source file and source line
11795 @item location-and-address
11796 Same as @code{location} but print the program counter even if located at the
11797 beginning of the location source line.
11799 Print the program counter (if not at the beginning of the location
11800 source line), the line number and the source line.
11801 @item source-and-location
11802 Print what @code{location} and @code{source-line} are printing.
11804 The information printed for a frame is decided automatically
11805 by the @value{GDBN} command that prints a frame.
11806 For example, @code{frame} prints the information printed by
11807 @code{source-and-location} while @code{stepi} will switch between
11808 @code{source-line} and @code{source-and-location} depending on the program
11810 The default value is @code{auto}.
11813 @anchor{set print repeats}
11814 @item set print repeats @var{number-of-repeats}
11815 @itemx set print repeats unlimited
11816 @cindex repeated array elements
11817 Set the threshold for suppressing display of repeated array
11818 elements. When the number of consecutive identical elements of an
11819 array exceeds the threshold, @value{GDBN} prints the string
11820 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11821 identical repetitions, instead of displaying the identical elements
11822 themselves. Setting the threshold to @code{unlimited} or zero will
11823 cause all elements to be individually printed. The default threshold
11826 @item show print repeats
11827 Display the current threshold for printing repeated identical
11830 @anchor{set print max-depth}
11831 @item set print max-depth @var{depth}
11832 @item set print max-depth unlimited
11833 @cindex printing nested structures
11834 Set the threshold after which nested structures are replaced with
11835 ellipsis, this can make visualising deeply nested structures easier.
11837 For example, given this C code
11840 typedef struct s1 @{ int a; @} s1;
11841 typedef struct s2 @{ s1 b; @} s2;
11842 typedef struct s3 @{ s2 c; @} s3;
11843 typedef struct s4 @{ s3 d; @} s4;
11845 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11848 The following table shows how different values of @var{depth} will
11849 effect how @code{var} is printed by @value{GDBN}:
11851 @multitable @columnfractions .3 .7
11852 @headitem @var{depth} setting @tab Result of @samp{p var}
11854 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11856 @tab @code{$1 = @{...@}}
11858 @tab @code{$1 = @{d = @{...@}@}}
11860 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11862 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11864 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11867 To see the contents of structures that have been hidden the user can
11868 either increase the print max-depth, or they can print the elements of
11869 the structure that are visible, for example
11872 (gdb) set print max-depth 2
11874 $1 = @{d = @{c = @{...@}@}@}
11876 $2 = @{c = @{b = @{...@}@}@}
11878 $3 = @{b = @{a = 3@}@}
11881 The pattern used to replace nested structures varies based on
11882 language, for most languages @code{@{...@}} is used, but Fortran uses
11885 @item show print max-depth
11886 Display the current threshold after which nested structures are
11887 replaces with ellipsis.
11889 @anchor{set print memory-tag-violations}
11890 @cindex printing memory tag violation information
11891 @item set print memory-tag-violations
11892 @itemx set print memory-tag-violations on
11893 Cause @value{GDBN} to display additional information about memory tag violations
11894 when printing pointers and addresses.
11896 @item set print memory-tag-violations off
11897 Stop printing memory tag violation information.
11899 @item show print memory-tag-violations
11900 Show whether memory tag violation information is displayed when printing
11901 pointers and addresses.
11903 @anchor{set print null-stop}
11904 @item set print null-stop
11905 @cindex @sc{null} elements in arrays
11906 Cause @value{GDBN} to stop printing the characters of an array when the first
11907 @sc{null} is encountered. This is useful when large arrays actually
11908 contain only short strings.
11909 The default is off.
11911 @item show print null-stop
11912 Show whether @value{GDBN} stops printing an array on the first
11913 @sc{null} character.
11915 @anchor{set print pretty}
11916 @item set print pretty on
11917 @cindex print structures in indented form
11918 @cindex indentation in structure display
11919 Cause @value{GDBN} to print structures in an indented format with one member
11920 per line, like this:
11935 @item set print pretty off
11936 Cause @value{GDBN} to print structures in a compact format, like this:
11940 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11941 meat = 0x54 "Pork"@}
11946 This is the default format.
11948 @item show print pretty
11949 Show which format @value{GDBN} is using to print structures.
11951 @anchor{set print raw-values}
11952 @item set print raw-values on
11953 Print values in raw form, without applying the pretty
11954 printers for the value.
11956 @item set print raw-values off
11957 Print values in pretty-printed form, if there is a pretty-printer
11958 for the value (@pxref{Pretty Printing}),
11959 otherwise print the value in raw form.
11961 The default setting is ``off''.
11963 @item show print raw-values
11964 Show whether to print values in raw form.
11966 @item set print sevenbit-strings on
11967 @cindex eight-bit characters in strings
11968 @cindex octal escapes in strings
11969 Print using only seven-bit characters; if this option is set,
11970 @value{GDBN} displays any eight-bit characters (in strings or
11971 character values) using the notation @code{\}@var{nnn}. This setting is
11972 best if you are working in English (@sc{ascii}) and you use the
11973 high-order bit of characters as a marker or ``meta'' bit.
11975 @item set print sevenbit-strings off
11976 Print full eight-bit characters. This allows the use of more
11977 international character sets, and is the default.
11979 @item show print sevenbit-strings
11980 Show whether or not @value{GDBN} is printing only seven-bit characters.
11982 @anchor{set print union}
11983 @item set print union on
11984 @cindex unions in structures, printing
11985 Tell @value{GDBN} to print unions which are contained in structures
11986 and other unions. This is the default setting.
11988 @item set print union off
11989 Tell @value{GDBN} not to print unions which are contained in
11990 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11993 @item show print union
11994 Ask @value{GDBN} whether or not it will print unions which are contained in
11995 structures and other unions.
11997 For example, given the declarations
12000 typedef enum @{Tree, Bug@} Species;
12001 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
12002 typedef enum @{Caterpillar, Cocoon, Butterfly@}
12013 struct thing foo = @{Tree, @{Acorn@}@};
12017 with @code{set print union on} in effect @samp{p foo} would print
12020 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
12024 and with @code{set print union off} in effect it would print
12027 $1 = @{it = Tree, form = @{...@}@}
12031 @code{set print union} affects programs written in C-like languages
12037 These settings are of interest when debugging C@t{++} programs:
12040 @cindex demangling C@t{++} names
12041 @item set print demangle
12042 @itemx set print demangle on
12043 Print C@t{++} names in their source form rather than in the encoded
12044 (``mangled'') form passed to the assembler and linker for type-safe
12045 linkage. The default is on.
12047 @item show print demangle
12048 Show whether C@t{++} names are printed in mangled or demangled form.
12050 @item set print asm-demangle
12051 @itemx set print asm-demangle on
12052 Print C@t{++} names in their source form rather than their mangled form, even
12053 in assembler code printouts such as instruction disassemblies.
12054 The default is off.
12056 @item show print asm-demangle
12057 Show whether C@t{++} names in assembly listings are printed in mangled
12060 @cindex C@t{++} symbol decoding style
12061 @cindex symbol decoding style, C@t{++}
12062 @kindex set demangle-style
12063 @item set demangle-style @var{style}
12064 Choose among several encoding schemes used by different compilers to represent
12065 C@t{++} names. If you omit @var{style}, you will see a list of possible
12066 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
12067 decoding style by inspecting your program.
12069 @item show demangle-style
12070 Display the encoding style currently in use for decoding C@t{++} symbols.
12072 @anchor{set print object}
12073 @item set print object
12074 @itemx set print object on
12075 @cindex derived type of an object, printing
12076 @cindex display derived types
12077 When displaying a pointer to an object, identify the @emph{actual}
12078 (derived) type of the object rather than the @emph{declared} type, using
12079 the virtual function table. Note that the virtual function table is
12080 required---this feature can only work for objects that have run-time
12081 type identification; a single virtual method in the object's declared
12082 type is sufficient. Note that this setting is also taken into account when
12083 working with variable objects via MI (@pxref{GDB/MI}).
12085 @item set print object off
12086 Display only the declared type of objects, without reference to the
12087 virtual function table. This is the default setting.
12089 @item show print object
12090 Show whether actual, or declared, object types are displayed.
12092 @anchor{set print static-members}
12093 @item set print static-members
12094 @itemx set print static-members on
12095 @cindex static members of C@t{++} objects
12096 Print static members when displaying a C@t{++} object. The default is on.
12098 @item set print static-members off
12099 Do not print static members when displaying a C@t{++} object.
12101 @item show print static-members
12102 Show whether C@t{++} static members are printed or not.
12104 @item set print pascal_static-members
12105 @itemx set print pascal_static-members on
12106 @cindex static members of Pascal objects
12107 @cindex Pascal objects, static members display
12108 Print static members when displaying a Pascal object. The default is on.
12110 @item set print pascal_static-members off
12111 Do not print static members when displaying a Pascal object.
12113 @item show print pascal_static-members
12114 Show whether Pascal static members are printed or not.
12116 @c These don't work with HP ANSI C++ yet.
12117 @anchor{set print vtbl}
12118 @item set print vtbl
12119 @itemx set print vtbl on
12120 @cindex pretty print C@t{++} virtual function tables
12121 @cindex virtual functions (C@t{++}) display
12122 @cindex VTBL display
12123 Pretty print C@t{++} virtual function tables. The default is off.
12124 (The @code{vtbl} commands do not work on programs compiled with the HP
12125 ANSI C@t{++} compiler (@code{aCC}).)
12127 @item set print vtbl off
12128 Do not pretty print C@t{++} virtual function tables.
12130 @item show print vtbl
12131 Show whether C@t{++} virtual function tables are pretty printed, or not.
12134 @node Pretty Printing
12135 @section Pretty Printing
12137 @value{GDBN} provides a mechanism to allow pretty-printing of values using
12138 Python code. It greatly simplifies the display of complex objects. This
12139 mechanism works for both MI and the CLI.
12142 * Pretty-Printer Introduction:: Introduction to pretty-printers
12143 * Pretty-Printer Example:: An example pretty-printer
12144 * Pretty-Printer Commands:: Pretty-printer commands
12147 @node Pretty-Printer Introduction
12148 @subsection Pretty-Printer Introduction
12150 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
12151 registered for the value. If there is then @value{GDBN} invokes the
12152 pretty-printer to print the value. Otherwise the value is printed normally.
12154 Pretty-printers are normally named. This makes them easy to manage.
12155 The @samp{info pretty-printer} command will list all the installed
12156 pretty-printers with their names.
12157 If a pretty-printer can handle multiple data types, then its
12158 @dfn{subprinters} are the printers for the individual data types.
12159 Each such subprinter has its own name.
12160 The format of the name is @var{printer-name};@var{subprinter-name}.
12162 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
12163 Typically they are automatically loaded and registered when the corresponding
12164 debug information is loaded, thus making them available without having to
12165 do anything special.
12167 There are three places where a pretty-printer can be registered.
12171 Pretty-printers registered globally are available when debugging
12175 Pretty-printers registered with a program space are available only
12176 when debugging that program.
12177 @xref{Progspaces In Python}, for more details on program spaces in Python.
12180 Pretty-printers registered with an objfile are loaded and unloaded
12181 with the corresponding objfile (e.g., shared library).
12182 @xref{Objfiles In Python}, for more details on objfiles in Python.
12185 @xref{Selecting Pretty-Printers}, for further information on how
12186 pretty-printers are selected,
12188 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12191 @node Pretty-Printer Example
12192 @subsection Pretty-Printer Example
12194 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12197 (@value{GDBP}) print s
12199 static npos = 4294967295,
12201 <std::allocator<char>> = @{
12202 <__gnu_cxx::new_allocator<char>> = @{
12203 <No data fields>@}, <No data fields>
12205 members of std::basic_string<char, std::char_traits<char>,
12206 std::allocator<char> >::_Alloc_hider:
12207 _M_p = 0x804a014 "abcd"
12212 With a pretty-printer for @code{std::string} only the contents are printed:
12215 (@value{GDBP}) print s
12219 @node Pretty-Printer Commands
12220 @subsection Pretty-Printer Commands
12221 @cindex pretty-printer commands
12224 @kindex info pretty-printer
12225 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12226 Print the list of installed pretty-printers.
12227 This includes disabled pretty-printers, which are marked as such.
12229 @var{object-regexp} is a regular expression matching the objects
12230 whose pretty-printers to list.
12231 Objects can be @code{global}, the program space's file
12232 (@pxref{Progspaces In Python}),
12233 and the object files within that program space (@pxref{Objfiles In Python}).
12234 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12235 looks up a printer from these three objects.
12237 @var{name-regexp} is a regular expression matching the name of the printers
12240 @kindex disable pretty-printer
12241 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12242 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12243 A disabled pretty-printer is not forgotten, it may be enabled again later.
12245 @kindex enable pretty-printer
12246 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12247 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12252 Suppose we have three pretty-printers installed: one from library1.so
12253 named @code{foo} that prints objects of type @code{foo}, and
12254 another from library2.so named @code{bar} that prints two types of objects,
12255 @code{bar1} and @code{bar2}.
12259 (@value{GDBP}) info pretty-printer
12268 (@value{GDBP}) info pretty-printer library2
12275 (@value{GDBP}) disable pretty-printer library1
12277 2 of 3 printers enabled
12278 (@value{GDBP}) info pretty-printer
12287 (@value{GDBP}) disable pretty-printer library2 bar;bar1
12289 1 of 3 printers enabled
12290 (@value{GDBP}) info pretty-printer library2
12297 (@value{GDBP}) disable pretty-printer library2 bar
12299 0 of 3 printers enabled
12300 (@value{GDBP}) info pretty-printer
12310 Note that for @code{bar} the entire printer can be disabled,
12311 as can each individual subprinter.
12313 Printing values and frame arguments is done by default using
12314 the enabled pretty printers.
12316 The print option @code{-raw-values} and @value{GDBN} setting
12317 @code{set print raw-values} (@pxref{set print raw-values}) can be
12318 used to print values without applying the enabled pretty printers.
12320 Similarly, the backtrace option @code{-raw-frame-arguments} and
12321 @value{GDBN} setting @code{set print raw-frame-arguments}
12322 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12323 enabled pretty printers when printing frame argument values.
12325 @node Value History
12326 @section Value History
12328 @cindex value history
12329 @cindex history of values printed by @value{GDBN}
12330 Values printed by the @code{print} command are saved in the @value{GDBN}
12331 @dfn{value history}. This allows you to refer to them in other expressions.
12332 Values are kept until the symbol table is re-read or discarded
12333 (for example with the @code{file} or @code{symbol-file} commands).
12334 When the symbol table changes, the value history is discarded,
12335 since the values may contain pointers back to the types defined in the
12340 @cindex history number
12341 The values printed are given @dfn{history numbers} by which you can
12342 refer to them. These are successive integers starting with one.
12343 @code{print} shows you the history number assigned to a value by
12344 printing @samp{$@var{num} = } before the value; here @var{num} is the
12347 To refer to any previous value, use @samp{$} followed by the value's
12348 history number. The way @code{print} labels its output is designed to
12349 remind you of this. Just @code{$} refers to the most recent value in
12350 the history, and @code{$$} refers to the value before that.
12351 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12352 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12353 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12355 For example, suppose you have just printed a pointer to a structure and
12356 want to see the contents of the structure. It suffices to type
12362 If you have a chain of structures where the component @code{next} points
12363 to the next one, you can print the contents of the next one with this:
12370 You can print successive links in the chain by repeating this
12371 command---which you can do by just typing @key{RET}.
12373 Note that the history records values, not expressions. If the value of
12374 @code{x} is 4 and you type these commands:
12382 then the value recorded in the value history by the @code{print} command
12383 remains 4 even though the value of @code{x} has changed.
12386 @kindex show values
12388 Print the last ten values in the value history, with their item numbers.
12389 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12390 values} does not change the history.
12392 @item show values @var{n}
12393 Print ten history values centered on history item number @var{n}.
12395 @item show values +
12396 Print ten history values just after the values last printed. If no more
12397 values are available, @code{show values +} produces no display.
12400 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12401 same effect as @samp{show values +}.
12403 @node Convenience Vars
12404 @section Convenience Variables
12406 @cindex convenience variables
12407 @cindex user-defined variables
12408 @value{GDBN} provides @dfn{convenience variables} that you can use within
12409 @value{GDBN} to hold on to a value and refer to it later. These variables
12410 exist entirely within @value{GDBN}; they are not part of your program, and
12411 setting a convenience variable has no direct effect on further execution
12412 of your program. That is why you can use them freely.
12414 Convenience variables are prefixed with @samp{$}. Any name preceded by
12415 @samp{$} can be used for a convenience variable, unless it is one of
12416 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12417 (Value history references, in contrast, are @emph{numbers} preceded
12418 by @samp{$}. @xref{Value History, ,Value History}.)
12420 You can save a value in a convenience variable with an assignment
12421 expression, just as you would set a variable in your program.
12425 set $foo = *object_ptr
12429 would save in @code{$foo} the value contained in the object pointed to by
12432 Using a convenience variable for the first time creates it, but its
12433 value is @code{void} until you assign a new value. You can alter the
12434 value with another assignment at any time.
12436 Convenience variables have no fixed types. You can assign a convenience
12437 variable any type of value, including structures and arrays, even if
12438 that variable already has a value of a different type. The convenience
12439 variable, when used as an expression, has the type of its current value.
12442 @kindex show convenience
12443 @cindex show all user variables and functions
12444 @item show convenience
12445 Print a list of convenience variables used so far, and their values,
12446 as well as a list of the convenience functions.
12447 Abbreviated @code{show conv}.
12449 @kindex init-if-undefined
12450 @cindex convenience variables, initializing
12451 @item init-if-undefined $@var{variable} = @var{expression}
12452 Set a convenience variable if it has not already been set. This is useful
12453 for user-defined commands that keep some state. It is similar, in concept,
12454 to using local static variables with initializers in C (except that
12455 convenience variables are global). It can also be used to allow users to
12456 override default values used in a command script.
12458 If the variable is already defined then the expression is not evaluated so
12459 any side-effects do not occur.
12462 One of the ways to use a convenience variable is as a counter to be
12463 incremented or a pointer to be advanced. For example, to print
12464 a field from successive elements of an array of structures:
12468 print bar[$i++]->contents
12472 Repeat that command by typing @key{RET}.
12474 Some convenience variables are created automatically by @value{GDBN} and given
12475 values likely to be useful.
12478 @vindex $_@r{, convenience variable}
12480 The variable @code{$_} is automatically set by the @code{x} command to
12481 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12482 commands which provide a default address for @code{x} to examine also
12483 set @code{$_} to that address; these commands include @code{info line}
12484 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12485 except when set by the @code{x} command, in which case it is a pointer
12486 to the type of @code{$__}.
12488 @vindex $__@r{, convenience variable}
12490 The variable @code{$__} is automatically set by the @code{x} command
12491 to the value found in the last address examined. Its type is chosen
12492 to match the format in which the data was printed.
12495 @vindex $_exitcode@r{, convenience variable}
12496 When the program being debugged terminates normally, @value{GDBN}
12497 automatically sets this variable to the exit code of the program, and
12498 resets @code{$_exitsignal} to @code{void}.
12501 @vindex $_exitsignal@r{, convenience variable}
12502 When the program being debugged dies due to an uncaught signal,
12503 @value{GDBN} automatically sets this variable to that signal's number,
12504 and resets @code{$_exitcode} to @code{void}.
12506 To distinguish between whether the program being debugged has exited
12507 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12508 @code{$_exitsignal} is not @code{void}), the convenience function
12509 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12510 Functions}). For example, considering the following source code:
12513 #include <signal.h>
12516 main (int argc, char *argv[])
12523 A valid way of telling whether the program being debugged has exited
12524 or signalled would be:
12527 (@value{GDBP}) define has_exited_or_signalled
12528 Type commands for definition of ``has_exited_or_signalled''.
12529 End with a line saying just ``end''.
12530 >if $_isvoid ($_exitsignal)
12531 >echo The program has exited\n
12533 >echo The program has signalled\n
12539 Program terminated with signal SIGALRM, Alarm clock.
12540 The program no longer exists.
12541 (@value{GDBP}) has_exited_or_signalled
12542 The program has signalled
12545 As can be seen, @value{GDBN} correctly informs that the program being
12546 debugged has signalled, since it calls @code{raise} and raises a
12547 @code{SIGALRM} signal. If the program being debugged had not called
12548 @code{raise}, then @value{GDBN} would report a normal exit:
12551 (@value{GDBP}) has_exited_or_signalled
12552 The program has exited
12556 The variable @code{$_exception} is set to the exception object being
12557 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12559 @item $_ada_exception
12560 The variable @code{$_ada_exception} is set to the address of the
12561 exception being caught or thrown at an Ada exception-related
12562 catchpoint. @xref{Set Catchpoints}.
12565 @itemx $_probe_arg0@dots{}$_probe_arg11
12566 Arguments to a static probe. @xref{Static Probe Points}.
12569 @vindex $_sdata@r{, inspect, convenience variable}
12570 The variable @code{$_sdata} contains extra collected static tracepoint
12571 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12572 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12573 if extra static tracepoint data has not been collected.
12576 @vindex $_siginfo@r{, convenience variable}
12577 The variable @code{$_siginfo} contains extra signal information
12578 (@pxref{extra signal information}). Note that @code{$_siginfo}
12579 could be empty, if the application has not yet received any signals.
12580 For example, it will be empty before you execute the @code{run} command.
12583 @vindex $_tlb@r{, convenience variable}
12584 The variable @code{$_tlb} is automatically set when debugging
12585 applications running on MS-Windows in native mode or connected to
12586 gdbserver that supports the @code{qGetTIBAddr} request.
12587 @xref{General Query Packets}.
12588 This variable contains the address of the thread information block.
12591 The number of the current inferior. @xref{Inferiors Connections and
12592 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12595 The thread number of the current thread. @xref{thread numbers}.
12598 The global number of the current thread. @xref{global thread numbers}.
12602 @vindex $_gdb_major@r{, convenience variable}
12603 @vindex $_gdb_minor@r{, convenience variable}
12604 The major and minor version numbers of the running @value{GDBN}.
12605 Development snapshots and pretest versions have their minor version
12606 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12607 the value 12 for @code{$_gdb_minor}. These variables allow you to
12608 write scripts that work with different versions of @value{GDBN}
12609 without errors caused by features unavailable in some of those
12612 @item $_shell_exitcode
12613 @itemx $_shell_exitsignal
12614 @vindex $_shell_exitcode@r{, convenience variable}
12615 @vindex $_shell_exitsignal@r{, convenience variable}
12616 @cindex shell command, exit code
12617 @cindex shell command, exit signal
12618 @cindex exit status of shell commands
12619 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12620 shell commands. When a launched command terminates, @value{GDBN}
12621 automatically maintains the variables @code{$_shell_exitcode}
12622 and @code{$_shell_exitsignal} according to the exit status of the last
12623 launched command. These variables are set and used similarly to
12624 the variables @code{$_exitcode} and @code{$_exitsignal}.
12628 @node Convenience Funs
12629 @section Convenience Functions
12631 @cindex convenience functions
12632 @value{GDBN} also supplies some @dfn{convenience functions}. These
12633 have a syntax similar to convenience variables. A convenience
12634 function can be used in an expression just like an ordinary function;
12635 however, a convenience function is implemented internally to
12638 These functions do not require @value{GDBN} to be configured with
12639 @code{Python} support, which means that they are always available.
12643 @item $_isvoid (@var{expr})
12644 @findex $_isvoid@r{, convenience function}
12645 Return one if the expression @var{expr} is @code{void}. Otherwise it
12648 A @code{void} expression is an expression where the type of the result
12649 is @code{void}. For example, you can examine a convenience variable
12650 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12654 (@value{GDBP}) print $_exitcode
12656 (@value{GDBP}) print $_isvoid ($_exitcode)
12659 Starting program: ./a.out
12660 [Inferior 1 (process 29572) exited normally]
12661 (@value{GDBP}) print $_exitcode
12663 (@value{GDBP}) print $_isvoid ($_exitcode)
12667 In the example above, we used @code{$_isvoid} to check whether
12668 @code{$_exitcode} is @code{void} before and after the execution of the
12669 program being debugged. Before the execution there is no exit code to
12670 be examined, therefore @code{$_exitcode} is @code{void}. After the
12671 execution the program being debugged returned zero, therefore
12672 @code{$_exitcode} is zero, which means that it is not @code{void}
12675 The @code{void} expression can also be a call of a function from the
12676 program being debugged. For example, given the following function:
12685 The result of calling it inside @value{GDBN} is @code{void}:
12688 (@value{GDBP}) print foo ()
12690 (@value{GDBP}) print $_isvoid (foo ())
12692 (@value{GDBP}) set $v = foo ()
12693 (@value{GDBP}) print $v
12695 (@value{GDBP}) print $_isvoid ($v)
12699 @item $_gdb_setting_str (@var{setting})
12700 @findex $_gdb_setting_str@r{, convenience function}
12701 Return the value of the @value{GDBN} @var{setting} as a string.
12702 @var{setting} is any setting that can be used in a @code{set} or
12703 @code{show} command (@pxref{Controlling GDB}).
12706 (@value{GDBP}) show print frame-arguments
12707 Printing of non-scalar frame arguments is "scalars".
12708 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12710 (@value{GDBP}) p $_gdb_setting_str("height")
12715 @item $_gdb_setting (@var{setting})
12716 @findex $_gdb_setting@r{, convenience function}
12717 Return the value of the @value{GDBN} @var{setting}.
12718 The type of the returned value depends on the setting.
12720 The value type for boolean and auto boolean settings is @code{int}.
12721 The boolean values @code{off} and @code{on} are converted to
12722 the integer values @code{0} and @code{1}. The value @code{auto} is
12723 converted to the value @code{-1}.
12725 The value type for integer settings is either @code{unsigned int}
12726 or @code{int}, depending on the setting.
12728 Some integer settings accept an @code{unlimited} value.
12729 Depending on the setting, the @code{set} command also accepts
12730 the value @code{0} or the value @code{@minus{}1} as a synonym for
12732 For example, @code{set height unlimited} is equivalent to
12733 @code{set height 0}.
12735 Some other settings that accept the @code{unlimited} value
12736 use the value @code{0} to literally mean zero.
12737 For example, @code{set history size 0} indicates to not
12738 record any @value{GDBN} commands in the command history.
12739 For such settings, @code{@minus{}1} is the synonym
12740 for @code{unlimited}.
12742 See the documentation of the corresponding @code{set} command for
12743 the numerical value equivalent to @code{unlimited}.
12745 The @code{$_gdb_setting} function converts the unlimited value
12746 to a @code{0} or a @code{@minus{}1} value according to what the
12747 @code{set} command uses.
12751 (@value{GDBP}) p $_gdb_setting_str("height")
12753 (@value{GDBP}) p $_gdb_setting("height")
12755 (@value{GDBP}) set height unlimited
12756 (@value{GDBP}) p $_gdb_setting_str("height")
12758 (@value{GDBP}) p $_gdb_setting("height")
12762 (@value{GDBP}) p $_gdb_setting_str("history size")
12764 (@value{GDBP}) p $_gdb_setting("history size")
12766 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12768 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12774 Other setting types (enum, filename, optional filename, string, string noescape)
12775 are returned as string values.
12778 @item $_gdb_maint_setting_str (@var{setting})
12779 @findex $_gdb_maint_setting_str@r{, convenience function}
12780 Like the @code{$_gdb_setting_str} function, but works with
12781 @code{maintenance set} variables.
12783 @item $_gdb_maint_setting (@var{setting})
12784 @findex $_gdb_maint_setting@r{, convenience function}
12785 Like the @code{$_gdb_setting} function, but works with
12786 @code{maintenance set} variables.
12790 The following functions require @value{GDBN} to be configured with
12791 @code{Python} support.
12795 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12796 @findex $_memeq@r{, convenience function}
12797 Returns one if the @var{length} bytes at the addresses given by
12798 @var{buf1} and @var{buf2} are equal.
12799 Otherwise it returns zero.
12801 @item $_regex(@var{str}, @var{regex})
12802 @findex $_regex@r{, convenience function}
12803 Returns one if the string @var{str} matches the regular expression
12804 @var{regex}. Otherwise it returns zero.
12805 The syntax of the regular expression is that specified by @code{Python}'s
12806 regular expression support.
12808 @item $_streq(@var{str1}, @var{str2})
12809 @findex $_streq@r{, convenience function}
12810 Returns one if the strings @var{str1} and @var{str2} are equal.
12811 Otherwise it returns zero.
12813 @item $_strlen(@var{str})
12814 @findex $_strlen@r{, convenience function}
12815 Returns the length of string @var{str}.
12817 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12818 @findex $_caller_is@r{, convenience function}
12819 Returns one if the calling function's name is equal to @var{name}.
12820 Otherwise it returns zero.
12822 If the optional argument @var{number_of_frames} is provided,
12823 it is the number of frames up in the stack to look.
12831 at testsuite/gdb.python/py-caller-is.c:21
12832 #1 0x00000000004005a0 in middle_func ()
12833 at testsuite/gdb.python/py-caller-is.c:27
12834 #2 0x00000000004005ab in top_func ()
12835 at testsuite/gdb.python/py-caller-is.c:33
12836 #3 0x00000000004005b6 in main ()
12837 at testsuite/gdb.python/py-caller-is.c:39
12838 (gdb) print $_caller_is ("middle_func")
12840 (gdb) print $_caller_is ("top_func", 2)
12844 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12845 @findex $_caller_matches@r{, convenience function}
12846 Returns one if the calling function's name matches the regular expression
12847 @var{regexp}. Otherwise it returns zero.
12849 If the optional argument @var{number_of_frames} is provided,
12850 it is the number of frames up in the stack to look.
12853 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12854 @findex $_any_caller_is@r{, convenience function}
12855 Returns one if any calling function's name is equal to @var{name}.
12856 Otherwise it returns zero.
12858 If the optional argument @var{number_of_frames} is provided,
12859 it is the number of frames up in the stack to look.
12862 This function differs from @code{$_caller_is} in that this function
12863 checks all stack frames from the immediate caller to the frame specified
12864 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12865 frame specified by @var{number_of_frames}.
12867 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12868 @findex $_any_caller_matches@r{, convenience function}
12869 Returns one if any calling function's name matches the regular expression
12870 @var{regexp}. Otherwise it returns zero.
12872 If the optional argument @var{number_of_frames} is provided,
12873 it is the number of frames up in the stack to look.
12876 This function differs from @code{$_caller_matches} in that this function
12877 checks all stack frames from the immediate caller to the frame specified
12878 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12879 frame specified by @var{number_of_frames}.
12881 @item $_as_string(@var{value})
12882 @findex $_as_string@r{, convenience function}
12883 Return the string representation of @var{value}.
12885 This function is useful to obtain the textual label (enumerator) of an
12886 enumeration value. For example, assuming the variable @var{node} is of
12887 an enumerated type:
12890 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12891 Visiting node of type NODE_INTEGER
12894 @item $_cimag(@var{value})
12895 @itemx $_creal(@var{value})
12896 @findex $_cimag@r{, convenience function}
12897 @findex $_creal@r{, convenience function}
12898 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12899 the complex number @var{value}.
12901 The type of the imaginary or real part depends on the type of the
12902 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12903 will return an imaginary part of type @code{float}.
12907 @value{GDBN} provides the ability to list and get help on
12908 convenience functions.
12911 @item help function
12912 @kindex help function
12913 @cindex show all convenience functions
12914 Print a list of all convenience functions.
12921 You can refer to machine register contents, in expressions, as variables
12922 with names starting with @samp{$}. The names of registers are different
12923 for each machine; use @code{info registers} to see the names used on
12927 @kindex info registers
12928 @item info registers
12929 Print the names and values of all registers except floating-point
12930 and vector registers (in the selected stack frame).
12932 @kindex info all-registers
12933 @cindex floating point registers
12934 @item info all-registers
12935 Print the names and values of all registers, including floating-point
12936 and vector registers (in the selected stack frame).
12938 @anchor{info_registers_reggroup}
12939 @item info registers @var{reggroup} @dots{}
12940 Print the name and value of the registers in each of the specified
12941 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12942 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12944 @item info registers @var{regname} @dots{}
12945 Print the @dfn{relativized} value of each specified register @var{regname}.
12946 As discussed in detail below, register values are normally relative to
12947 the selected stack frame. The @var{regname} may be any register name valid on
12948 the machine you are using, with or without the initial @samp{$}.
12951 @anchor{standard registers}
12952 @cindex stack pointer register
12953 @cindex program counter register
12954 @cindex process status register
12955 @cindex frame pointer register
12956 @cindex standard registers
12957 @value{GDBN} has four ``standard'' register names that are available (in
12958 expressions) on most machines---whenever they do not conflict with an
12959 architecture's canonical mnemonics for registers. The register names
12960 @code{$pc} and @code{$sp} are used for the program counter register and
12961 the stack pointer. @code{$fp} is used for a register that contains a
12962 pointer to the current stack frame, and @code{$ps} is used for a
12963 register that contains the processor status. For example,
12964 you could print the program counter in hex with
12971 or print the instruction to be executed next with
12978 or add four to the stack pointer@footnote{This is a way of removing
12979 one word from the stack, on machines where stacks grow downward in
12980 memory (most machines, nowadays). This assumes that the innermost
12981 stack frame is selected; setting @code{$sp} is not allowed when other
12982 stack frames are selected. To pop entire frames off the stack,
12983 regardless of machine architecture, use @code{return};
12984 see @ref{Returning, ,Returning from a Function}.} with
12990 Whenever possible, these four standard register names are available on
12991 your machine even though the machine has different canonical mnemonics,
12992 so long as there is no conflict. The @code{info registers} command
12993 shows the canonical names. For example, on the SPARC, @code{info
12994 registers} displays the processor status register as @code{$psr} but you
12995 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12996 is an alias for the @sc{eflags} register.
12998 @value{GDBN} always considers the contents of an ordinary register as an
12999 integer when the register is examined in this way. Some machines have
13000 special registers which can hold nothing but floating point; these
13001 registers are considered to have floating point values. There is no way
13002 to refer to the contents of an ordinary register as floating point value
13003 (although you can @emph{print} it as a floating point value with
13004 @samp{print/f $@var{regname}}).
13006 Some registers have distinct ``raw'' and ``virtual'' data formats. This
13007 means that the data format in which the register contents are saved by
13008 the operating system is not the same one that your program normally
13009 sees. For example, the registers of the 68881 floating point
13010 coprocessor are always saved in ``extended'' (raw) format, but all C
13011 programs expect to work with ``double'' (virtual) format. In such
13012 cases, @value{GDBN} normally works with the virtual format only (the format
13013 that makes sense for your program), but the @code{info registers} command
13014 prints the data in both formats.
13016 @cindex SSE registers (x86)
13017 @cindex MMX registers (x86)
13018 Some machines have special registers whose contents can be interpreted
13019 in several different ways. For example, modern x86-based machines
13020 have SSE and MMX registers that can hold several values packed
13021 together in several different formats. @value{GDBN} refers to such
13022 registers in @code{struct} notation:
13025 (@value{GDBP}) print $xmm1
13027 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
13028 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
13029 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
13030 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
13031 v4_int32 = @{0, 20657912, 11, 13@},
13032 v2_int64 = @{88725056443645952, 55834574859@},
13033 uint128 = 0x0000000d0000000b013b36f800000000
13038 To set values of such registers, you need to tell @value{GDBN} which
13039 view of the register you wish to change, as if you were assigning
13040 value to a @code{struct} member:
13043 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
13046 Normally, register values are relative to the selected stack frame
13047 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
13048 value that the register would contain if all stack frames farther in
13049 were exited and their saved registers restored. In order to see the
13050 true contents of hardware registers, you must select the innermost
13051 frame (with @samp{frame 0}).
13053 @cindex caller-saved registers
13054 @cindex call-clobbered registers
13055 @cindex volatile registers
13056 @cindex <not saved> values
13057 Usually ABIs reserve some registers as not needed to be saved by the
13058 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
13059 registers). It may therefore not be possible for @value{GDBN} to know
13060 the value a register had before the call (in other words, in the outer
13061 frame), if the register value has since been changed by the callee.
13062 @value{GDBN} tries to deduce where the inner frame saved
13063 (``callee-saved'') registers, from the debug info, unwind info, or the
13064 machine code generated by your compiler. If some register is not
13065 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
13066 its own knowledge of the ABI, or because the debug/unwind info
13067 explicitly says the register's value is undefined), @value{GDBN}
13068 displays @w{@samp{<not saved>}} as the register's value. With targets
13069 that @value{GDBN} has no knowledge of the register saving convention,
13070 if a register was not saved by the callee, then its value and location
13071 in the outer frame are assumed to be the same of the inner frame.
13072 This is usually harmless, because if the register is call-clobbered,
13073 the caller either does not care what is in the register after the
13074 call, or has code to restore the value that it does care about. Note,
13075 however, that if you change such a register in the outer frame, you
13076 may also be affecting the inner frame. Also, the more ``outer'' the
13077 frame is you're looking at, the more likely a call-clobbered
13078 register's value is to be wrong, in the sense that it doesn't actually
13079 represent the value the register had just before the call.
13081 @node Floating Point Hardware
13082 @section Floating Point Hardware
13083 @cindex floating point
13085 Depending on the configuration, @value{GDBN} may be able to give
13086 you more information about the status of the floating point hardware.
13091 Display hardware-dependent information about the floating
13092 point unit. The exact contents and layout vary depending on the
13093 floating point chip. Currently, @samp{info float} is supported on
13094 the ARM and x86 machines.
13098 @section Vector Unit
13099 @cindex vector unit
13101 Depending on the configuration, @value{GDBN} may be able to give you
13102 more information about the status of the vector unit.
13105 @kindex info vector
13107 Display information about the vector unit. The exact contents and
13108 layout vary depending on the hardware.
13111 @node OS Information
13112 @section Operating System Auxiliary Information
13113 @cindex OS information
13115 @value{GDBN} provides interfaces to useful OS facilities that can help
13116 you debug your program.
13118 @cindex auxiliary vector
13119 @cindex vector, auxiliary
13120 Some operating systems supply an @dfn{auxiliary vector} to programs at
13121 startup. This is akin to the arguments and environment that you
13122 specify for a program, but contains a system-dependent variety of
13123 binary values that tell system libraries important details about the
13124 hardware, operating system, and process. Each value's purpose is
13125 identified by an integer tag; the meanings are well-known but system-specific.
13126 Depending on the configuration and operating system facilities,
13127 @value{GDBN} may be able to show you this information. For remote
13128 targets, this functionality may further depend on the remote stub's
13129 support of the @samp{qXfer:auxv:read} packet, see
13130 @ref{qXfer auxiliary vector read}.
13135 Display the auxiliary vector of the inferior, which can be either a
13136 live process or a core dump file. @value{GDBN} prints each tag value
13137 numerically, and also shows names and text descriptions for recognized
13138 tags. Some values in the vector are numbers, some bit masks, and some
13139 pointers to strings or other data. @value{GDBN} displays each value in the
13140 most appropriate form for a recognized tag, and in hexadecimal for
13141 an unrecognized tag.
13144 On some targets, @value{GDBN} can access operating system-specific
13145 information and show it to you. The types of information available
13146 will differ depending on the type of operating system running on the
13147 target. The mechanism used to fetch the data is described in
13148 @ref{Operating System Information}. For remote targets, this
13149 functionality depends on the remote stub's support of the
13150 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
13154 @item info os @var{infotype}
13156 Display OS information of the requested type.
13158 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
13160 @anchor{linux info os infotypes}
13162 @kindex info os cpus
13164 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
13165 the available fields from /proc/cpuinfo. For each supported architecture
13166 different fields are available. Two common entries are processor which gives
13167 CPU number and bogomips; a system constant that is calculated during
13168 kernel initialization.
13170 @kindex info os files
13172 Display the list of open file descriptors on the target. For each
13173 file descriptor, @value{GDBN} prints the identifier of the process
13174 owning the descriptor, the command of the owning process, the value
13175 of the descriptor, and the target of the descriptor.
13177 @kindex info os modules
13179 Display the list of all loaded kernel modules on the target. For each
13180 module, @value{GDBN} prints the module name, the size of the module in
13181 bytes, the number of times the module is used, the dependencies of the
13182 module, the status of the module, and the address of the loaded module
13185 @kindex info os msg
13187 Display the list of all System V message queues on the target. For each
13188 message queue, @value{GDBN} prints the message queue key, the message
13189 queue identifier, the access permissions, the current number of bytes
13190 on the queue, the current number of messages on the queue, the processes
13191 that last sent and received a message on the queue, the user and group
13192 of the owner and creator of the message queue, the times at which a
13193 message was last sent and received on the queue, and the time at which
13194 the message queue was last changed.
13196 @kindex info os processes
13198 Display the list of processes on the target. For each process,
13199 @value{GDBN} prints the process identifier, the name of the user, the
13200 command corresponding to the process, and the list of processor cores
13201 that the process is currently running on. (To understand what these
13202 properties mean, for this and the following info types, please consult
13203 the general @sc{gnu}/Linux documentation.)
13205 @kindex info os procgroups
13207 Display the list of process groups on the target. For each process,
13208 @value{GDBN} prints the identifier of the process group that it belongs
13209 to, the command corresponding to the process group leader, the process
13210 identifier, and the command line of the process. The list is sorted
13211 first by the process group identifier, then by the process identifier,
13212 so that processes belonging to the same process group are grouped together
13213 and the process group leader is listed first.
13215 @kindex info os semaphores
13217 Display the list of all System V semaphore sets on the target. For each
13218 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13219 set identifier, the access permissions, the number of semaphores in the
13220 set, the user and group of the owner and creator of the semaphore set,
13221 and the times at which the semaphore set was operated upon and changed.
13223 @kindex info os shm
13225 Display the list of all System V shared-memory regions on the target.
13226 For each shared-memory region, @value{GDBN} prints the region key,
13227 the shared-memory identifier, the access permissions, the size of the
13228 region, the process that created the region, the process that last
13229 attached to or detached from the region, the current number of live
13230 attaches to the region, and the times at which the region was last
13231 attached to, detach from, and changed.
13233 @kindex info os sockets
13235 Display the list of Internet-domain sockets on the target. For each
13236 socket, @value{GDBN} prints the address and port of the local and
13237 remote endpoints, the current state of the connection, the creator of
13238 the socket, the IP address family of the socket, and the type of the
13241 @kindex info os threads
13243 Display the list of threads running on the target. For each thread,
13244 @value{GDBN} prints the identifier of the process that the thread
13245 belongs to, the command of the process, the thread identifier, and the
13246 processor core that it is currently running on. The main thread of a
13247 process is not listed.
13251 If @var{infotype} is omitted, then list the possible values for
13252 @var{infotype} and the kind of OS information available for each
13253 @var{infotype}. If the target does not return a list of possible
13254 types, this command will report an error.
13257 @node Memory Region Attributes
13258 @section Memory Region Attributes
13259 @cindex memory region attributes
13261 @dfn{Memory region attributes} allow you to describe special handling
13262 required by regions of your target's memory. @value{GDBN} uses
13263 attributes to determine whether to allow certain types of memory
13264 accesses; whether to use specific width accesses; and whether to cache
13265 target memory. By default the description of memory regions is
13266 fetched from the target (if the current target supports this), but the
13267 user can override the fetched regions.
13269 Defined memory regions can be individually enabled and disabled. When a
13270 memory region is disabled, @value{GDBN} uses the default attributes when
13271 accessing memory in that region. Similarly, if no memory regions have
13272 been defined, @value{GDBN} uses the default attributes when accessing
13275 When a memory region is defined, it is given a number to identify it;
13276 to enable, disable, or remove a memory region, you specify that number.
13280 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13281 Define a memory region bounded by @var{lower} and @var{upper} with
13282 attributes @var{attributes}@dots{}, and add it to the list of regions
13283 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13284 case: it is treated as the target's maximum memory address.
13285 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13288 Discard any user changes to the memory regions and use target-supplied
13289 regions, if available, or no regions if the target does not support.
13292 @item delete mem @var{nums}@dots{}
13293 Remove memory regions @var{nums}@dots{} from the list of regions
13294 monitored by @value{GDBN}.
13296 @kindex disable mem
13297 @item disable mem @var{nums}@dots{}
13298 Disable monitoring of memory regions @var{nums}@dots{}.
13299 A disabled memory region is not forgotten.
13300 It may be enabled again later.
13303 @item enable mem @var{nums}@dots{}
13304 Enable monitoring of memory regions @var{nums}@dots{}.
13308 Print a table of all defined memory regions, with the following columns
13312 @item Memory Region Number
13313 @item Enabled or Disabled.
13314 Enabled memory regions are marked with @samp{y}.
13315 Disabled memory regions are marked with @samp{n}.
13318 The address defining the inclusive lower bound of the memory region.
13321 The address defining the exclusive upper bound of the memory region.
13324 The list of attributes set for this memory region.
13329 @subsection Attributes
13331 @subsubsection Memory Access Mode
13332 The access mode attributes set whether @value{GDBN} may make read or
13333 write accesses to a memory region.
13335 While these attributes prevent @value{GDBN} from performing invalid
13336 memory accesses, they do nothing to prevent the target system, I/O DMA,
13337 etc.@: from accessing memory.
13341 Memory is read only.
13343 Memory is write only.
13345 Memory is read/write. This is the default.
13348 @subsubsection Memory Access Size
13349 The access size attribute tells @value{GDBN} to use specific sized
13350 accesses in the memory region. Often memory mapped device registers
13351 require specific sized accesses. If no access size attribute is
13352 specified, @value{GDBN} may use accesses of any size.
13356 Use 8 bit memory accesses.
13358 Use 16 bit memory accesses.
13360 Use 32 bit memory accesses.
13362 Use 64 bit memory accesses.
13365 @c @subsubsection Hardware/Software Breakpoints
13366 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13367 @c will use hardware or software breakpoints for the internal breakpoints
13368 @c used by the step, next, finish, until, etc. commands.
13372 @c Always use hardware breakpoints
13373 @c @item swbreak (default)
13376 @subsubsection Data Cache
13377 The data cache attributes set whether @value{GDBN} will cache target
13378 memory. While this generally improves performance by reducing debug
13379 protocol overhead, it can lead to incorrect results because @value{GDBN}
13380 does not know about volatile variables or memory mapped device
13385 Enable @value{GDBN} to cache target memory.
13387 Disable @value{GDBN} from caching target memory. This is the default.
13390 @subsection Memory Access Checking
13391 @value{GDBN} can be instructed to refuse accesses to memory that is
13392 not explicitly described. This can be useful if accessing such
13393 regions has undesired effects for a specific target, or to provide
13394 better error checking. The following commands control this behaviour.
13397 @kindex set mem inaccessible-by-default
13398 @item set mem inaccessible-by-default [on|off]
13399 If @code{on} is specified, make @value{GDBN} treat memory not
13400 explicitly described by the memory ranges as non-existent and refuse accesses
13401 to such memory. The checks are only performed if there's at least one
13402 memory range defined. If @code{off} is specified, make @value{GDBN}
13403 treat the memory not explicitly described by the memory ranges as RAM.
13404 The default value is @code{on}.
13405 @kindex show mem inaccessible-by-default
13406 @item show mem inaccessible-by-default
13407 Show the current handling of accesses to unknown memory.
13411 @c @subsubsection Memory Write Verification
13412 @c The memory write verification attributes set whether @value{GDBN}
13413 @c will re-reads data after each write to verify the write was successful.
13417 @c @item noverify (default)
13420 @node Dump/Restore Files
13421 @section Copy Between Memory and a File
13422 @cindex dump/restore files
13423 @cindex append data to a file
13424 @cindex dump data to a file
13425 @cindex restore data from a file
13427 You can use the commands @code{dump}, @code{append}, and
13428 @code{restore} to copy data between target memory and a file. The
13429 @code{dump} and @code{append} commands write data to a file, and the
13430 @code{restore} command reads data from a file back into the inferior's
13431 memory. Files may be in binary, Motorola S-record, Intel hex,
13432 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13433 append to binary files, and cannot read from Verilog Hex files.
13438 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13439 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13440 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13441 or the value of @var{expr}, to @var{filename} in the given format.
13443 The @var{format} parameter may be any one of:
13450 Motorola S-record format.
13452 Tektronix Hex format.
13454 Verilog Hex format.
13457 @value{GDBN} uses the same definitions of these formats as the
13458 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13459 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13463 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13464 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13465 Append the contents of memory from @var{start_addr} to @var{end_addr},
13466 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13467 (@value{GDBN} can only append data to files in raw binary form.)
13470 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13471 Restore the contents of file @var{filename} into memory. The
13472 @code{restore} command can automatically recognize any known @sc{bfd}
13473 file format, except for raw binary. To restore a raw binary file you
13474 must specify the optional keyword @code{binary} after the filename.
13476 If @var{bias} is non-zero, its value will be added to the addresses
13477 contained in the file. Binary files always start at address zero, so
13478 they will be restored at address @var{bias}. Other bfd files have
13479 a built-in location; they will be restored at offset @var{bias}
13480 from that location.
13482 If @var{start} and/or @var{end} are non-zero, then only data between
13483 file offset @var{start} and file offset @var{end} will be restored.
13484 These offsets are relative to the addresses in the file, before
13485 the @var{bias} argument is applied.
13489 @node Core File Generation
13490 @section How to Produce a Core File from Your Program
13491 @cindex dump core from inferior
13493 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13494 image of a running process and its process status (register values
13495 etc.). Its primary use is post-mortem debugging of a program that
13496 crashed while it ran outside a debugger. A program that crashes
13497 automatically produces a core file, unless this feature is disabled by
13498 the user. @xref{Files}, for information on invoking @value{GDBN} in
13499 the post-mortem debugging mode.
13501 Occasionally, you may wish to produce a core file of the program you
13502 are debugging in order to preserve a snapshot of its state.
13503 @value{GDBN} has a special command for that.
13507 @kindex generate-core-file
13508 @item generate-core-file [@var{file}]
13509 @itemx gcore [@var{file}]
13510 Produce a core dump of the inferior process. The optional argument
13511 @var{file} specifies the file name where to put the core dump. If not
13512 specified, the file name defaults to @file{core.@var{pid}}, where
13513 @var{pid} is the inferior process ID.
13515 Note that this command is implemented only for some systems (as of
13516 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13518 On @sc{gnu}/Linux, this command can take into account the value of the
13519 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13520 dump (@pxref{set use-coredump-filter}), and by default honors the
13521 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13522 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13524 @kindex set use-coredump-filter
13525 @anchor{set use-coredump-filter}
13526 @item set use-coredump-filter on
13527 @itemx set use-coredump-filter off
13528 Enable or disable the use of the file
13529 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13530 files. This file is used by the Linux kernel to decide what types of
13531 memory mappings will be dumped or ignored when generating a core dump
13532 file. @var{pid} is the process ID of a currently running process.
13534 To make use of this feature, you have to write in the
13535 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13536 which is a bit mask representing the memory mapping types. If a bit
13537 is set in the bit mask, then the memory mappings of the corresponding
13538 types will be dumped; otherwise, they will be ignored. This
13539 configuration is inherited by child processes. For more information
13540 about the bits that can be set in the
13541 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13542 manpage of @code{core(5)}.
13544 By default, this option is @code{on}. If this option is turned
13545 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13546 and instead uses the same default value as the Linux kernel in order
13547 to decide which pages will be dumped in the core dump file. This
13548 value is currently @code{0x33}, which means that bits @code{0}
13549 (anonymous private mappings), @code{1} (anonymous shared mappings),
13550 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13551 This will cause these memory mappings to be dumped automatically.
13553 @kindex set dump-excluded-mappings
13554 @anchor{set dump-excluded-mappings}
13555 @item set dump-excluded-mappings on
13556 @itemx set dump-excluded-mappings off
13557 If @code{on} is specified, @value{GDBN} will dump memory mappings
13558 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13559 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13561 The default value is @code{off}.
13564 @node Character Sets
13565 @section Character Sets
13566 @cindex character sets
13568 @cindex translating between character sets
13569 @cindex host character set
13570 @cindex target character set
13572 If the program you are debugging uses a different character set to
13573 represent characters and strings than the one @value{GDBN} uses itself,
13574 @value{GDBN} can automatically translate between the character sets for
13575 you. The character set @value{GDBN} uses we call the @dfn{host
13576 character set}; the one the inferior program uses we call the
13577 @dfn{target character set}.
13579 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13580 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13581 remote protocol (@pxref{Remote Debugging}) to debug a program
13582 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13583 then the host character set is Latin-1, and the target character set is
13584 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13585 target-charset EBCDIC-US}, then @value{GDBN} translates between
13586 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13587 character and string literals in expressions.
13589 @value{GDBN} has no way to automatically recognize which character set
13590 the inferior program uses; you must tell it, using the @code{set
13591 target-charset} command, described below.
13593 Here are the commands for controlling @value{GDBN}'s character set
13597 @item set target-charset @var{charset}
13598 @kindex set target-charset
13599 Set the current target character set to @var{charset}. To display the
13600 list of supported target character sets, type
13601 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13603 @item set host-charset @var{charset}
13604 @kindex set host-charset
13605 Set the current host character set to @var{charset}.
13607 By default, @value{GDBN} uses a host character set appropriate to the
13608 system it is running on; you can override that default using the
13609 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13610 automatically determine the appropriate host character set. In this
13611 case, @value{GDBN} uses @samp{UTF-8}.
13613 @value{GDBN} can only use certain character sets as its host character
13614 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13615 @value{GDBN} will list the host character sets it supports.
13617 @item set charset @var{charset}
13618 @kindex set charset
13619 Set the current host and target character sets to @var{charset}. As
13620 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13621 @value{GDBN} will list the names of the character sets that can be used
13622 for both host and target.
13625 @kindex show charset
13626 Show the names of the current host and target character sets.
13628 @item show host-charset
13629 @kindex show host-charset
13630 Show the name of the current host character set.
13632 @item show target-charset
13633 @kindex show target-charset
13634 Show the name of the current target character set.
13636 @item set target-wide-charset @var{charset}
13637 @kindex set target-wide-charset
13638 Set the current target's wide character set to @var{charset}. This is
13639 the character set used by the target's @code{wchar_t} type. To
13640 display the list of supported wide character sets, type
13641 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13643 @item show target-wide-charset
13644 @kindex show target-wide-charset
13645 Show the name of the current target's wide character set.
13648 Here is an example of @value{GDBN}'s character set support in action.
13649 Assume that the following source code has been placed in the file
13650 @file{charset-test.c}:
13656 = @{72, 101, 108, 108, 111, 44, 32, 119,
13657 111, 114, 108, 100, 33, 10, 0@};
13658 char ibm1047_hello[]
13659 = @{200, 133, 147, 147, 150, 107, 64, 166,
13660 150, 153, 147, 132, 90, 37, 0@};
13664 printf ("Hello, world!\n");
13668 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13669 containing the string @samp{Hello, world!} followed by a newline,
13670 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13672 We compile the program, and invoke the debugger on it:
13675 $ gcc -g charset-test.c -o charset-test
13676 $ gdb -nw charset-test
13677 GNU gdb 2001-12-19-cvs
13678 Copyright 2001 Free Software Foundation, Inc.
13683 We can use the @code{show charset} command to see what character sets
13684 @value{GDBN} is currently using to interpret and display characters and
13688 (@value{GDBP}) show charset
13689 The current host and target character set is `ISO-8859-1'.
13693 For the sake of printing this manual, let's use @sc{ascii} as our
13694 initial character set:
13696 (@value{GDBP}) set charset ASCII
13697 (@value{GDBP}) show charset
13698 The current host and target character set is `ASCII'.
13702 Let's assume that @sc{ascii} is indeed the correct character set for our
13703 host system --- in other words, let's assume that if @value{GDBN} prints
13704 characters using the @sc{ascii} character set, our terminal will display
13705 them properly. Since our current target character set is also
13706 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13709 (@value{GDBP}) print ascii_hello
13710 $1 = 0x401698 "Hello, world!\n"
13711 (@value{GDBP}) print ascii_hello[0]
13716 @value{GDBN} uses the target character set for character and string
13717 literals you use in expressions:
13720 (@value{GDBP}) print '+'
13725 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13728 @value{GDBN} relies on the user to tell it which character set the
13729 target program uses. If we print @code{ibm1047_hello} while our target
13730 character set is still @sc{ascii}, we get jibberish:
13733 (@value{GDBP}) print ibm1047_hello
13734 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13735 (@value{GDBP}) print ibm1047_hello[0]
13740 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13741 @value{GDBN} tells us the character sets it supports:
13744 (@value{GDBP}) set target-charset
13745 ASCII EBCDIC-US IBM1047 ISO-8859-1
13746 (@value{GDBP}) set target-charset
13749 We can select @sc{ibm1047} as our target character set, and examine the
13750 program's strings again. Now the @sc{ascii} string is wrong, but
13751 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13752 target character set, @sc{ibm1047}, to the host character set,
13753 @sc{ascii}, and they display correctly:
13756 (@value{GDBP}) set target-charset IBM1047
13757 (@value{GDBP}) show charset
13758 The current host character set is `ASCII'.
13759 The current target character set is `IBM1047'.
13760 (@value{GDBP}) print ascii_hello
13761 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13762 (@value{GDBP}) print ascii_hello[0]
13764 (@value{GDBP}) print ibm1047_hello
13765 $8 = 0x4016a8 "Hello, world!\n"
13766 (@value{GDBP}) print ibm1047_hello[0]
13771 As above, @value{GDBN} uses the target character set for character and
13772 string literals you use in expressions:
13775 (@value{GDBP}) print '+'
13780 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13783 @node Caching Target Data
13784 @section Caching Data of Targets
13785 @cindex caching data of targets
13787 @value{GDBN} caches data exchanged between the debugger and a target.
13788 Each cache is associated with the address space of the inferior.
13789 @xref{Inferiors Connections and Programs}, about inferior and address space.
13790 Such caching generally improves performance in remote debugging
13791 (@pxref{Remote Debugging}), because it reduces the overhead of the
13792 remote protocol by bundling memory reads and writes into large chunks.
13793 Unfortunately, simply caching everything would lead to incorrect results,
13794 since @value{GDBN} does not necessarily know anything about volatile
13795 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13796 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13798 Therefore, by default, @value{GDBN} only caches data
13799 known to be on the stack@footnote{In non-stop mode, it is moderately
13800 rare for a running thread to modify the stack of a stopped thread
13801 in a way that would interfere with a backtrace, and caching of
13802 stack reads provides a significant speed up of remote backtraces.} or
13803 in the code segment.
13804 Other regions of memory can be explicitly marked as
13805 cacheable; @pxref{Memory Region Attributes}.
13808 @kindex set remotecache
13809 @item set remotecache on
13810 @itemx set remotecache off
13811 This option no longer does anything; it exists for compatibility
13814 @kindex show remotecache
13815 @item show remotecache
13816 Show the current state of the obsolete remotecache flag.
13818 @kindex set stack-cache
13819 @item set stack-cache on
13820 @itemx set stack-cache off
13821 Enable or disable caching of stack accesses. When @code{on}, use
13822 caching. By default, this option is @code{on}.
13824 @kindex show stack-cache
13825 @item show stack-cache
13826 Show the current state of data caching for memory accesses.
13828 @kindex set code-cache
13829 @item set code-cache on
13830 @itemx set code-cache off
13831 Enable or disable caching of code segment accesses. When @code{on},
13832 use caching. By default, this option is @code{on}. This improves
13833 performance of disassembly in remote debugging.
13835 @kindex show code-cache
13836 @item show code-cache
13837 Show the current state of target memory cache for code segment
13840 @kindex info dcache
13841 @item info dcache @r{[}line@r{]}
13842 Print the information about the performance of data cache of the
13843 current inferior's address space. The information displayed
13844 includes the dcache width and depth, and for each cache line, its
13845 number, address, and how many times it was referenced. This
13846 command is useful for debugging the data cache operation.
13848 If a line number is specified, the contents of that line will be
13851 @item set dcache size @var{size}
13852 @cindex dcache size
13853 @kindex set dcache size
13854 Set maximum number of entries in dcache (dcache depth above).
13856 @item set dcache line-size @var{line-size}
13857 @cindex dcache line-size
13858 @kindex set dcache line-size
13859 Set number of bytes each dcache entry caches (dcache width above).
13860 Must be a power of 2.
13862 @item show dcache size
13863 @kindex show dcache size
13864 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13866 @item show dcache line-size
13867 @kindex show dcache line-size
13868 Show default size of dcache lines.
13870 @item maint flush dcache
13871 @cindex dcache, flushing
13872 @kindex maint flush dcache
13873 Flush the contents (if any) of the dcache. This maintainer command is
13874 useful when debugging the dcache implementation.
13878 @node Searching Memory
13879 @section Search Memory
13880 @cindex searching memory
13882 Memory can be searched for a particular sequence of bytes with the
13883 @code{find} command.
13887 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13888 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13889 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13890 etc. The search begins at address @var{start_addr} and continues for either
13891 @var{len} bytes or through to @var{end_addr} inclusive.
13894 @var{s} and @var{n} are optional parameters.
13895 They may be specified in either order, apart or together.
13898 @item @var{s}, search query size
13899 The size of each search query value.
13905 halfwords (two bytes)
13909 giant words (eight bytes)
13912 All values are interpreted in the current language.
13913 This means, for example, that if the current source language is C/C@t{++}
13914 then searching for the string ``hello'' includes the trailing '\0'.
13915 The null terminator can be removed from searching by using casts,
13916 e.g.: @samp{@{char[5]@}"hello"}.
13918 If the value size is not specified, it is taken from the
13919 value's type in the current language.
13920 This is useful when one wants to specify the search
13921 pattern as a mixture of types.
13922 Note that this means, for example, that in the case of C-like languages
13923 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13924 which is typically four bytes.
13926 @item @var{n}, maximum number of finds
13927 The maximum number of matches to print. The default is to print all finds.
13930 You can use strings as search values. Quote them with double-quotes
13932 The string value is copied into the search pattern byte by byte,
13933 regardless of the endianness of the target and the size specification.
13935 The address of each match found is printed as well as a count of the
13936 number of matches found.
13938 The address of the last value found is stored in convenience variable
13940 A count of the number of matches is stored in @samp{$numfound}.
13942 For example, if stopped at the @code{printf} in this function:
13948 static char hello[] = "hello-hello";
13949 static struct @{ char c; short s; int i; @}
13950 __attribute__ ((packed)) mixed
13951 = @{ 'c', 0x1234, 0x87654321 @};
13952 printf ("%s\n", hello);
13957 you get during debugging:
13960 (gdb) find &hello[0], +sizeof(hello), "hello"
13961 0x804956d <hello.1620+6>
13963 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13964 0x8049567 <hello.1620>
13965 0x804956d <hello.1620+6>
13967 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13968 0x8049567 <hello.1620>
13969 0x804956d <hello.1620+6>
13971 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13972 0x8049567 <hello.1620>
13974 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13975 0x8049560 <mixed.1625>
13977 (gdb) print $numfound
13980 $2 = (void *) 0x8049560
13984 @section Value Sizes
13986 Whenever @value{GDBN} prints a value memory will be allocated within
13987 @value{GDBN} to hold the contents of the value. It is possible in
13988 some languages with dynamic typing systems, that an invalid program
13989 may indicate a value that is incorrectly large, this in turn may cause
13990 @value{GDBN} to try and allocate an overly large amount of memory.
13993 @kindex set max-value-size
13994 @item set max-value-size @var{bytes}
13995 @itemx set max-value-size unlimited
13996 Set the maximum size of memory that @value{GDBN} will allocate for the
13997 contents of a value to @var{bytes}, trying to display a value that
13998 requires more memory than that will result in an error.
14000 Setting this variable does not effect values that have already been
14001 allocated within @value{GDBN}, only future allocations.
14003 There's a minimum size that @code{max-value-size} can be set to in
14004 order that @value{GDBN} can still operate correctly, this minimum is
14005 currently 16 bytes.
14007 The limit applies to the results of some subexpressions as well as to
14008 complete expressions. For example, an expression denoting a simple
14009 integer component, such as @code{x.y.z}, may fail if the size of
14010 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
14011 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
14012 @var{A} is an array variable with non-constant size, will generally
14013 succeed regardless of the bounds on @var{A}, as long as the component
14014 size is less than @var{bytes}.
14016 The default value of @code{max-value-size} is currently 64k.
14018 @kindex show max-value-size
14019 @item show max-value-size
14020 Show the maximum size of memory, in bytes, that @value{GDBN} will
14021 allocate for the contents of a value.
14024 @node Optimized Code
14025 @chapter Debugging Optimized Code
14026 @cindex optimized code, debugging
14027 @cindex debugging optimized code
14029 Almost all compilers support optimization. With optimization
14030 disabled, the compiler generates assembly code that corresponds
14031 directly to your source code, in a simplistic way. As the compiler
14032 applies more powerful optimizations, the generated assembly code
14033 diverges from your original source code. With help from debugging
14034 information generated by the compiler, @value{GDBN} can map from
14035 the running program back to constructs from your original source.
14037 @value{GDBN} is more accurate with optimization disabled. If you
14038 can recompile without optimization, it is easier to follow the
14039 progress of your program during debugging. But, there are many cases
14040 where you may need to debug an optimized version.
14042 When you debug a program compiled with @samp{-g -O}, remember that the
14043 optimizer has rearranged your code; the debugger shows you what is
14044 really there. Do not be too surprised when the execution path does not
14045 exactly match your source file! An extreme example: if you define a
14046 variable, but never use it, @value{GDBN} never sees that
14047 variable---because the compiler optimizes it out of existence.
14049 Some things do not work as well with @samp{-g -O} as with just
14050 @samp{-g}, particularly on machines with instruction scheduling. If in
14051 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
14052 please report it to us as a bug (including a test case!).
14053 @xref{Variables}, for more information about debugging optimized code.
14056 * Inline Functions:: How @value{GDBN} presents inlining
14057 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
14060 @node Inline Functions
14061 @section Inline Functions
14062 @cindex inline functions, debugging
14064 @dfn{Inlining} is an optimization that inserts a copy of the function
14065 body directly at each call site, instead of jumping to a shared
14066 routine. @value{GDBN} displays inlined functions just like
14067 non-inlined functions. They appear in backtraces. You can view their
14068 arguments and local variables, step into them with @code{step}, skip
14069 them with @code{next}, and escape from them with @code{finish}.
14070 You can check whether a function was inlined by using the
14071 @code{info frame} command.
14073 For @value{GDBN} to support inlined functions, the compiler must
14074 record information about inlining in the debug information ---
14075 @value{NGCC} using the @sc{dwarf 2} format does this, and several
14076 other compilers do also. @value{GDBN} only supports inlined functions
14077 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
14078 do not emit two required attributes (@samp{DW_AT_call_file} and
14079 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
14080 function calls with earlier versions of @value{NGCC}. It instead
14081 displays the arguments and local variables of inlined functions as
14082 local variables in the caller.
14084 The body of an inlined function is directly included at its call site;
14085 unlike a non-inlined function, there are no instructions devoted to
14086 the call. @value{GDBN} still pretends that the call site and the
14087 start of the inlined function are different instructions. Stepping to
14088 the call site shows the call site, and then stepping again shows
14089 the first line of the inlined function, even though no additional
14090 instructions are executed.
14092 This makes source-level debugging much clearer; you can see both the
14093 context of the call and then the effect of the call. Only stepping by
14094 a single instruction using @code{stepi} or @code{nexti} does not do
14095 this; single instruction steps always show the inlined body.
14097 There are some ways that @value{GDBN} does not pretend that inlined
14098 function calls are the same as normal calls:
14102 Setting breakpoints at the call site of an inlined function may not
14103 work, because the call site does not contain any code. @value{GDBN}
14104 may incorrectly move the breakpoint to the next line of the enclosing
14105 function, after the call. This limitation will be removed in a future
14106 version of @value{GDBN}; until then, set a breakpoint on an earlier line
14107 or inside the inlined function instead.
14110 @value{GDBN} cannot locate the return value of inlined calls after
14111 using the @code{finish} command. This is a limitation of compiler-generated
14112 debugging information; after @code{finish}, you can step to the next line
14113 and print a variable where your program stored the return value.
14117 @node Tail Call Frames
14118 @section Tail Call Frames
14119 @cindex tail call frames, debugging
14121 Function @code{B} can call function @code{C} in its very last statement. In
14122 unoptimized compilation the call of @code{C} is immediately followed by return
14123 instruction at the end of @code{B} code. Optimizing compiler may replace the
14124 call and return in function @code{B} into one jump to function @code{C}
14125 instead. Such use of a jump instruction is called @dfn{tail call}.
14127 During execution of function @code{C}, there will be no indication in the
14128 function call stack frames that it was tail-called from @code{B}. If function
14129 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
14130 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
14131 some cases @value{GDBN} can determine that @code{C} was tail-called from
14132 @code{B}, and it will then create fictitious call frame for that, with the
14133 return address set up as if @code{B} called @code{C} normally.
14135 This functionality is currently supported only by DWARF 2 debugging format and
14136 the compiler has to produce @samp{DW_TAG_call_site} tags. With
14137 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
14140 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
14141 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
14145 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
14147 Stack level 1, frame at 0x7fffffffda30:
14148 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
14149 tail call frame, caller of frame at 0x7fffffffda30
14150 source language c++.
14151 Arglist at unknown address.
14152 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
14155 The detection of all the possible code path executions can find them ambiguous.
14156 There is no execution history stored (possible @ref{Reverse Execution} is never
14157 used for this purpose) and the last known caller could have reached the known
14158 callee by multiple different jump sequences. In such case @value{GDBN} still
14159 tries to show at least all the unambiguous top tail callers and all the
14160 unambiguous bottom tail calees, if any.
14163 @anchor{set debug entry-values}
14164 @item set debug entry-values
14165 @kindex set debug entry-values
14166 When set to on, enables printing of analysis messages for both frame argument
14167 values at function entry and tail calls. It will show all the possible valid
14168 tail calls code paths it has considered. It will also print the intersection
14169 of them with the final unambiguous (possibly partial or even empty) code path
14172 @item show debug entry-values
14173 @kindex show debug entry-values
14174 Show the current state of analysis messages printing for both frame argument
14175 values at function entry and tail calls.
14178 The analysis messages for tail calls can for example show why the virtual tail
14179 call frame for function @code{c} has not been recognized (due to the indirect
14180 reference by variable @code{x}):
14183 static void __attribute__((noinline, noclone)) c (void);
14184 void (*x) (void) = c;
14185 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14186 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
14187 int main (void) @{ x (); return 0; @}
14189 Breakpoint 1, DW_OP_entry_value resolving cannot find
14190 DW_TAG_call_site 0x40039a in main
14192 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14195 #1 0x000000000040039a in main () at t.c:5
14198 Another possibility is an ambiguous virtual tail call frames resolution:
14202 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14203 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14204 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14205 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14206 static void __attribute__((noinline, noclone)) b (void)
14207 @{ if (i) c (); else e (); @}
14208 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14209 int main (void) @{ a (); return 0; @}
14211 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14212 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14213 tailcall: reduced: 0x4004d2(a) |
14216 #1 0x00000000004004d2 in a () at t.c:8
14217 #2 0x0000000000400395 in main () at t.c:9
14220 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14221 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14223 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14224 @ifset HAVE_MAKEINFO_CLICK
14225 @set ARROW @click{}
14226 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14227 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14229 @ifclear HAVE_MAKEINFO_CLICK
14231 @set CALLSEQ1B @value{CALLSEQ1A}
14232 @set CALLSEQ2B @value{CALLSEQ2A}
14235 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14236 The code can have possible execution paths @value{CALLSEQ1B} or
14237 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14239 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14240 has found. It then finds another possible calling sequence - that one is
14241 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14242 printed as the @code{reduced:} calling sequence. That one could have many
14243 further @code{compare:} and @code{reduced:} statements as long as there remain
14244 any non-ambiguous sequence entries.
14246 For the frame of function @code{b} in both cases there are different possible
14247 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14248 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14249 therefore this one is displayed to the user while the ambiguous frames are
14252 There can be also reasons why printing of frame argument values at function
14257 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14258 static void __attribute__((noinline, noclone)) a (int i);
14259 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14260 static void __attribute__((noinline, noclone)) a (int i)
14261 @{ if (i) b (i - 1); else c (0); @}
14262 int main (void) @{ a (5); return 0; @}
14265 #0 c (i=i@@entry=0) at t.c:2
14266 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14267 function "a" at 0x400420 can call itself via tail calls
14268 i=<optimized out>) at t.c:6
14269 #2 0x000000000040036e in main () at t.c:7
14272 @value{GDBN} cannot find out from the inferior state if and how many times did
14273 function @code{a} call itself (via function @code{b}) as these calls would be
14274 tail calls. Such tail calls would modify the @code{i} variable, therefore
14275 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14276 prints @code{<optimized out>} instead.
14279 @chapter C Preprocessor Macros
14281 Some languages, such as C and C@t{++}, provide a way to define and invoke
14282 ``preprocessor macros'' which expand into strings of tokens.
14283 @value{GDBN} can evaluate expressions containing macro invocations, show
14284 the result of macro expansion, and show a macro's definition, including
14285 where it was defined.
14287 You may need to compile your program specially to provide @value{GDBN}
14288 with information about preprocessor macros. Most compilers do not
14289 include macros in their debugging information, even when you compile
14290 with the @option{-g} flag. @xref{Compilation}.
14292 A program may define a macro at one point, remove that definition later,
14293 and then provide a different definition after that. Thus, at different
14294 points in the program, a macro may have different definitions, or have
14295 no definition at all. If there is a current stack frame, @value{GDBN}
14296 uses the macros in scope at that frame's source code line. Otherwise,
14297 @value{GDBN} uses the macros in scope at the current listing location;
14300 Whenever @value{GDBN} evaluates an expression, it always expands any
14301 macro invocations present in the expression. @value{GDBN} also provides
14302 the following commands for working with macros explicitly.
14306 @kindex macro expand
14307 @cindex macro expansion, showing the results of preprocessor
14308 @cindex preprocessor macro expansion, showing the results of
14309 @cindex expanding preprocessor macros
14310 @item macro expand @var{expression}
14311 @itemx macro exp @var{expression}
14312 Show the results of expanding all preprocessor macro invocations in
14313 @var{expression}. Since @value{GDBN} simply expands macros, but does
14314 not parse the result, @var{expression} need not be a valid expression;
14315 it can be any string of tokens.
14318 @item macro expand-once @var{expression}
14319 @itemx macro exp1 @var{expression}
14320 @cindex expand macro once
14321 @i{(This command is not yet implemented.)} Show the results of
14322 expanding those preprocessor macro invocations that appear explicitly in
14323 @var{expression}. Macro invocations appearing in that expansion are
14324 left unchanged. This command allows you to see the effect of a
14325 particular macro more clearly, without being confused by further
14326 expansions. Since @value{GDBN} simply expands macros, but does not
14327 parse the result, @var{expression} need not be a valid expression; it
14328 can be any string of tokens.
14331 @cindex macro definition, showing
14332 @cindex definition of a macro, showing
14333 @cindex macros, from debug info
14334 @item info macro [-a|-all] [--] @var{macro}
14335 Show the current definition or all definitions of the named @var{macro},
14336 and describe the source location or compiler command-line where that
14337 definition was established. The optional double dash is to signify the end of
14338 argument processing and the beginning of @var{macro} for non C-like macros where
14339 the macro may begin with a hyphen.
14341 @kindex info macros
14342 @item info macros @var{locspec}
14343 Show all macro definitions that are in effect at the source line of
14344 the code location that results from resolving @var{locspec}, and
14345 describe the source location or compiler command-line where those
14346 definitions were established.
14348 @kindex macro define
14349 @cindex user-defined macros
14350 @cindex defining macros interactively
14351 @cindex macros, user-defined
14352 @item macro define @var{macro} @var{replacement-list}
14353 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14354 Introduce a definition for a preprocessor macro named @var{macro},
14355 invocations of which are replaced by the tokens given in
14356 @var{replacement-list}. The first form of this command defines an
14357 ``object-like'' macro, which takes no arguments; the second form
14358 defines a ``function-like'' macro, which takes the arguments given in
14361 A definition introduced by this command is in scope in every
14362 expression evaluated in @value{GDBN}, until it is removed with the
14363 @code{macro undef} command, described below. The definition overrides
14364 all definitions for @var{macro} present in the program being debugged,
14365 as well as any previous user-supplied definition.
14367 @kindex macro undef
14368 @item macro undef @var{macro}
14369 Remove any user-supplied definition for the macro named @var{macro}.
14370 This command only affects definitions provided with the @code{macro
14371 define} command, described above; it cannot remove definitions present
14372 in the program being debugged.
14376 List all the macros defined using the @code{macro define} command.
14379 @cindex macros, example of debugging with
14380 Here is a transcript showing the above commands in action. First, we
14381 show our source files:
14386 #include "sample.h"
14389 #define ADD(x) (M + x)
14394 printf ("Hello, world!\n");
14396 printf ("We're so creative.\n");
14398 printf ("Goodbye, world!\n");
14405 Now, we compile the program using the @sc{gnu} C compiler,
14406 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14407 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14408 and @option{-gdwarf-4}; we recommend always choosing the most recent
14409 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14410 includes information about preprocessor macros in the debugging
14414 $ gcc -gdwarf-2 -g3 sample.c -o sample
14418 Now, we start @value{GDBN} on our sample program:
14422 GNU gdb 2002-05-06-cvs
14423 Copyright 2002 Free Software Foundation, Inc.
14424 GDB is free software, @dots{}
14428 We can expand macros and examine their definitions, even when the
14429 program is not running. @value{GDBN} uses the current listing position
14430 to decide which macro definitions are in scope:
14433 (@value{GDBP}) list main
14436 5 #define ADD(x) (M + x)
14441 10 printf ("Hello, world!\n");
14443 12 printf ("We're so creative.\n");
14444 (@value{GDBP}) info macro ADD
14445 Defined at /home/jimb/gdb/macros/play/sample.c:5
14446 #define ADD(x) (M + x)
14447 (@value{GDBP}) info macro Q
14448 Defined at /home/jimb/gdb/macros/play/sample.h:1
14449 included at /home/jimb/gdb/macros/play/sample.c:2
14451 (@value{GDBP}) macro expand ADD(1)
14452 expands to: (42 + 1)
14453 (@value{GDBP}) macro expand-once ADD(1)
14454 expands to: once (M + 1)
14458 In the example above, note that @code{macro expand-once} expands only
14459 the macro invocation explicit in the original text --- the invocation of
14460 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14461 which was introduced by @code{ADD}.
14463 Once the program is running, @value{GDBN} uses the macro definitions in
14464 force at the source line of the current stack frame:
14467 (@value{GDBP}) break main
14468 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14470 Starting program: /home/jimb/gdb/macros/play/sample
14472 Breakpoint 1, main () at sample.c:10
14473 10 printf ("Hello, world!\n");
14477 At line 10, the definition of the macro @code{N} at line 9 is in force:
14480 (@value{GDBP}) info macro N
14481 Defined at /home/jimb/gdb/macros/play/sample.c:9
14483 (@value{GDBP}) macro expand N Q M
14484 expands to: 28 < 42
14485 (@value{GDBP}) print N Q M
14490 As we step over directives that remove @code{N}'s definition, and then
14491 give it a new definition, @value{GDBN} finds the definition (or lack
14492 thereof) in force at each point:
14495 (@value{GDBP}) next
14497 12 printf ("We're so creative.\n");
14498 (@value{GDBP}) info macro N
14499 The symbol `N' has no definition as a C/C++ preprocessor macro
14500 at /home/jimb/gdb/macros/play/sample.c:12
14501 (@value{GDBP}) next
14503 14 printf ("Goodbye, world!\n");
14504 (@value{GDBP}) info macro N
14505 Defined at /home/jimb/gdb/macros/play/sample.c:13
14507 (@value{GDBP}) macro expand N Q M
14508 expands to: 1729 < 42
14509 (@value{GDBP}) print N Q M
14514 In addition to source files, macros can be defined on the compilation command
14515 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14516 such a way, @value{GDBN} displays the location of their definition as line zero
14517 of the source file submitted to the compiler.
14520 (@value{GDBP}) info macro __STDC__
14521 Defined at /home/jimb/gdb/macros/play/sample.c:0
14528 @chapter Tracepoints
14529 @c This chapter is based on the documentation written by Michael
14530 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14532 @cindex tracepoints
14533 In some applications, it is not feasible for the debugger to interrupt
14534 the program's execution long enough for the developer to learn
14535 anything helpful about its behavior. If the program's correctness
14536 depends on its real-time behavior, delays introduced by a debugger
14537 might cause the program to change its behavior drastically, or perhaps
14538 fail, even when the code itself is correct. It is useful to be able
14539 to observe the program's behavior without interrupting it.
14541 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14542 specify locations in the program, called @dfn{tracepoints}, and
14543 arbitrary expressions to evaluate when those tracepoints are reached.
14544 Later, using the @code{tfind} command, you can examine the values
14545 those expressions had when the program hit the tracepoints. The
14546 expressions may also denote objects in memory---structures or arrays,
14547 for example---whose values @value{GDBN} should record; while visiting
14548 a particular tracepoint, you may inspect those objects as if they were
14549 in memory at that moment. However, because @value{GDBN} records these
14550 values without interacting with you, it can do so quickly and
14551 unobtrusively, hopefully not disturbing the program's behavior.
14553 The tracepoint facility is currently available only for remote
14554 targets. @xref{Targets}. In addition, your remote target must know
14555 how to collect trace data. This functionality is implemented in the
14556 remote stub; however, none of the stubs distributed with @value{GDBN}
14557 support tracepoints as of this writing. The format of the remote
14558 packets used to implement tracepoints are described in @ref{Tracepoint
14561 It is also possible to get trace data from a file, in a manner reminiscent
14562 of corefiles; you specify the filename, and use @code{tfind} to search
14563 through the file. @xref{Trace Files}, for more details.
14565 This chapter describes the tracepoint commands and features.
14568 * Set Tracepoints::
14569 * Analyze Collected Data::
14570 * Tracepoint Variables::
14574 @node Set Tracepoints
14575 @section Commands to Set Tracepoints
14577 Before running such a @dfn{trace experiment}, an arbitrary number of
14578 tracepoints can be set. A tracepoint is actually a special type of
14579 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14580 standard breakpoint commands. For instance, as with breakpoints,
14581 tracepoint numbers are successive integers starting from one, and many
14582 of the commands associated with tracepoints take the tracepoint number
14583 as their argument, to identify which tracepoint to work on.
14585 For each tracepoint, you can specify, in advance, some arbitrary set
14586 of data that you want the target to collect in the trace buffer when
14587 it hits that tracepoint. The collected data can include registers,
14588 local variables, or global data. Later, you can use @value{GDBN}
14589 commands to examine the values these data had at the time the
14590 tracepoint was hit.
14592 Tracepoints do not support every breakpoint feature. Ignore counts on
14593 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14594 commands when they are hit. Tracepoints may not be thread-specific
14597 @cindex fast tracepoints
14598 Some targets may support @dfn{fast tracepoints}, which are inserted in
14599 a different way (such as with a jump instead of a trap), that is
14600 faster but possibly restricted in where they may be installed.
14602 @cindex static tracepoints
14603 @cindex markers, static tracepoints
14604 @cindex probing markers, static tracepoints
14605 Regular and fast tracepoints are dynamic tracing facilities, meaning
14606 that they can be used to insert tracepoints at (almost) any location
14607 in the target. Some targets may also support controlling @dfn{static
14608 tracepoints} from @value{GDBN}. With static tracing, a set of
14609 instrumentation points, also known as @dfn{markers}, are embedded in
14610 the target program, and can be activated or deactivated by name or
14611 address. These are usually placed at locations which facilitate
14612 investigating what the target is actually doing. @value{GDBN}'s
14613 support for static tracing includes being able to list instrumentation
14614 points, and attach them with @value{GDBN} defined high level
14615 tracepoints that expose the whole range of convenience of
14616 @value{GDBN}'s tracepoints support. Namely, support for collecting
14617 registers values and values of global or local (to the instrumentation
14618 point) variables; tracepoint conditions and trace state variables.
14619 The act of installing a @value{GDBN} static tracepoint on an
14620 instrumentation point, or marker, is referred to as @dfn{probing} a
14621 static tracepoint marker.
14623 @code{gdbserver} supports tracepoints on some target systems.
14624 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14626 This section describes commands to set tracepoints and associated
14627 conditions and actions.
14630 * Create and Delete Tracepoints::
14631 * Enable and Disable Tracepoints::
14632 * Tracepoint Passcounts::
14633 * Tracepoint Conditions::
14634 * Trace State Variables::
14635 * Tracepoint Actions::
14636 * Listing Tracepoints::
14637 * Listing Static Tracepoint Markers::
14638 * Starting and Stopping Trace Experiments::
14639 * Tracepoint Restrictions::
14642 @node Create and Delete Tracepoints
14643 @subsection Create and Delete Tracepoints
14646 @cindex set tracepoint
14648 @item trace @var{locspec}
14649 The @code{trace} command is very similar to the @code{break} command.
14650 Its argument @var{locspec} can be any valid location specification.
14651 @xref{Location Specifications}. The @code{trace} command defines a tracepoint,
14652 which is a point in the target program where the debugger will briefly stop,
14653 collect some data, and then allow the program to continue. Setting a tracepoint
14654 or changing its actions takes effect immediately if the remote stub
14655 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14657 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14658 these changes don't take effect until the next @code{tstart}
14659 command, and once a trace experiment is running, further changes will
14660 not have any effect until the next trace experiment starts. In addition,
14661 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14662 address is not yet resolved. (This is similar to pending breakpoints.)
14663 Pending tracepoints are not downloaded to the target and not installed
14664 until they are resolved. The resolution of pending tracepoints requires
14665 @value{GDBN} support---when debugging with the remote target, and
14666 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14667 tracing}), pending tracepoints can not be resolved (and downloaded to
14668 the remote stub) while @value{GDBN} is disconnected.
14670 Here are some examples of using the @code{trace} command:
14673 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14675 (@value{GDBP}) @b{trace +2} // 2 lines forward
14677 (@value{GDBP}) @b{trace my_function} // first source line of function
14679 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14681 (@value{GDBP}) @b{trace *0x2117c4} // an address
14685 You can abbreviate @code{trace} as @code{tr}.
14687 @item trace @var{locspec} if @var{cond}
14688 Set a tracepoint with condition @var{cond}; evaluate the expression
14689 @var{cond} each time the tracepoint is reached, and collect data only
14690 if the value is nonzero---that is, if @var{cond} evaluates as true.
14691 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14692 information on tracepoint conditions.
14694 @item ftrace @var{locspec} [ if @var{cond} ]
14695 @cindex set fast tracepoint
14696 @cindex fast tracepoints, setting
14698 The @code{ftrace} command sets a fast tracepoint. For targets that
14699 support them, fast tracepoints will use a more efficient but possibly
14700 less general technique to trigger data collection, such as a jump
14701 instruction instead of a trap, or some sort of hardware support. It
14702 may not be possible to create a fast tracepoint at the desired
14703 location, in which case the command will exit with an explanatory
14706 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14709 On 32-bit x86-architecture systems, fast tracepoints normally need to
14710 be placed at an instruction that is 5 bytes or longer, but can be
14711 placed at 4-byte instructions if the low 64K of memory of the target
14712 program is available to install trampolines. Some Unix-type systems,
14713 such as @sc{gnu}/Linux, exclude low addresses from the program's
14714 address space; but for instance with the Linux kernel it is possible
14715 to let @value{GDBN} use this area by doing a @command{sysctl} command
14716 to set the @code{mmap_min_addr} kernel parameter, as in
14719 sudo sysctl -w vm.mmap_min_addr=32768
14723 which sets the low address to 32K, which leaves plenty of room for
14724 trampolines. The minimum address should be set to a page boundary.
14726 @item strace [@var{locspec} | -m @var{marker}] [ if @var{cond} ]
14727 @cindex set static tracepoint
14728 @cindex static tracepoints, setting
14729 @cindex probe static tracepoint marker
14731 The @code{strace} command sets a static tracepoint. For targets that
14732 support it, setting a static tracepoint probes a static
14733 instrumentation point, or marker, found at the code locations that
14734 result from resolving @var{locspec}. It may not be possible to set a
14735 static tracepoint at the desired code location, in which case the
14736 command will exit with an explanatory message.
14738 @value{GDBN} handles arguments to @code{strace} exactly as for
14739 @code{trace}, with the addition that the user can also specify
14740 @code{-m @var{marker}} instead of a location spec. This probes the marker
14741 identified by the @var{marker} string identifier. This identifier
14742 depends on the static tracepoint backend library your program is
14743 using. You can find all the marker identifiers in the @samp{ID} field
14744 of the @code{info static-tracepoint-markers} command output.
14745 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14746 Markers}. For example, in the following small program using the UST
14752 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14757 the marker id is composed of joining the first two arguments to the
14758 @code{trace_mark} call with a slash, which translates to:
14761 (@value{GDBP}) info static-tracepoint-markers
14762 Cnt Enb ID Address What
14763 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14769 so you may probe the marker above with:
14772 (@value{GDBP}) strace -m ust/bar33
14775 Static tracepoints accept an extra collect action --- @code{collect
14776 $_sdata}. This collects arbitrary user data passed in the probe point
14777 call to the tracing library. In the UST example above, you'll see
14778 that the third argument to @code{trace_mark} is a printf-like format
14779 string. The user data is then the result of running that formatting
14780 string against the following arguments. Note that @code{info
14781 static-tracepoint-markers} command output lists that format string in
14782 the @samp{Data:} field.
14784 You can inspect this data when analyzing the trace buffer, by printing
14785 the $_sdata variable like any other variable available to
14786 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14789 @cindex last tracepoint number
14790 @cindex recent tracepoint number
14791 @cindex tracepoint number
14792 The convenience variable @code{$tpnum} records the tracepoint number
14793 of the most recently set tracepoint.
14795 @kindex delete tracepoint
14796 @cindex tracepoint deletion
14797 @item delete tracepoint @r{[}@var{num}@r{]}
14798 Permanently delete one or more tracepoints. With no argument, the
14799 default is to delete all tracepoints. Note that the regular
14800 @code{delete} command can remove tracepoints also.
14805 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14807 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14811 You can abbreviate this command as @code{del tr}.
14814 @node Enable and Disable Tracepoints
14815 @subsection Enable and Disable Tracepoints
14817 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14820 @kindex disable tracepoint
14821 @item disable tracepoint @r{[}@var{num}@r{]}
14822 Disable tracepoint @var{num}, or all tracepoints if no argument
14823 @var{num} is given. A disabled tracepoint will have no effect during
14824 a trace experiment, but it is not forgotten. You can re-enable
14825 a disabled tracepoint using the @code{enable tracepoint} command.
14826 If the command is issued during a trace experiment and the debug target
14827 has support for disabling tracepoints during a trace experiment, then the
14828 change will be effective immediately. Otherwise, it will be applied to the
14829 next trace experiment.
14831 @kindex enable tracepoint
14832 @item enable tracepoint @r{[}@var{num}@r{]}
14833 Enable tracepoint @var{num}, or all tracepoints. If this command is
14834 issued during a trace experiment and the debug target supports enabling
14835 tracepoints during a trace experiment, then the enabled tracepoints will
14836 become effective immediately. Otherwise, they will become effective the
14837 next time a trace experiment is run.
14840 @node Tracepoint Passcounts
14841 @subsection Tracepoint Passcounts
14845 @cindex tracepoint pass count
14846 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14847 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14848 automatically stop a trace experiment. If a tracepoint's passcount is
14849 @var{n}, then the trace experiment will be automatically stopped on
14850 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14851 @var{num} is not specified, the @code{passcount} command sets the
14852 passcount of the most recently defined tracepoint. If no passcount is
14853 given, the trace experiment will run until stopped explicitly by the
14859 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14860 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14862 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14863 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14864 (@value{GDBP}) @b{trace foo}
14865 (@value{GDBP}) @b{pass 3}
14866 (@value{GDBP}) @b{trace bar}
14867 (@value{GDBP}) @b{pass 2}
14868 (@value{GDBP}) @b{trace baz}
14869 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14870 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14871 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14872 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14876 @node Tracepoint Conditions
14877 @subsection Tracepoint Conditions
14878 @cindex conditional tracepoints
14879 @cindex tracepoint conditions
14881 The simplest sort of tracepoint collects data every time your program
14882 reaches a specified place. You can also specify a @dfn{condition} for
14883 a tracepoint. A condition is just a Boolean expression in your
14884 programming language (@pxref{Expressions, ,Expressions}). A
14885 tracepoint with a condition evaluates the expression each time your
14886 program reaches it, and data collection happens only if the condition
14889 Tracepoint conditions can be specified when a tracepoint is set, by
14890 using @samp{if} in the arguments to the @code{trace} command.
14891 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14892 also be set or changed at any time with the @code{condition} command,
14893 just as with breakpoints.
14895 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14896 the conditional expression itself. Instead, @value{GDBN} encodes the
14897 expression into an agent expression (@pxref{Agent Expressions})
14898 suitable for execution on the target, independently of @value{GDBN}.
14899 Global variables become raw memory locations, locals become stack
14900 accesses, and so forth.
14902 For instance, suppose you have a function that is usually called
14903 frequently, but should not be called after an error has occurred. You
14904 could use the following tracepoint command to collect data about calls
14905 of that function that happen while the error code is propagating
14906 through the program; an unconditional tracepoint could end up
14907 collecting thousands of useless trace frames that you would have to
14911 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14914 @node Trace State Variables
14915 @subsection Trace State Variables
14916 @cindex trace state variables
14918 A @dfn{trace state variable} is a special type of variable that is
14919 created and managed by target-side code. The syntax is the same as
14920 that for GDB's convenience variables (a string prefixed with ``$''),
14921 but they are stored on the target. They must be created explicitly,
14922 using a @code{tvariable} command. They are always 64-bit signed
14925 Trace state variables are remembered by @value{GDBN}, and downloaded
14926 to the target along with tracepoint information when the trace
14927 experiment starts. There are no intrinsic limits on the number of
14928 trace state variables, beyond memory limitations of the target.
14930 @cindex convenience variables, and trace state variables
14931 Although trace state variables are managed by the target, you can use
14932 them in print commands and expressions as if they were convenience
14933 variables; @value{GDBN} will get the current value from the target
14934 while the trace experiment is running. Trace state variables share
14935 the same namespace as other ``$'' variables, which means that you
14936 cannot have trace state variables with names like @code{$23} or
14937 @code{$pc}, nor can you have a trace state variable and a convenience
14938 variable with the same name.
14942 @item tvariable $@var{name} [ = @var{expression} ]
14944 The @code{tvariable} command creates a new trace state variable named
14945 @code{$@var{name}}, and optionally gives it an initial value of
14946 @var{expression}. The @var{expression} is evaluated when this command is
14947 entered; the result will be converted to an integer if possible,
14948 otherwise @value{GDBN} will report an error. A subsequent
14949 @code{tvariable} command specifying the same name does not create a
14950 variable, but instead assigns the supplied initial value to the
14951 existing variable of that name, overwriting any previous initial
14952 value. The default initial value is 0.
14954 @item info tvariables
14955 @kindex info tvariables
14956 List all the trace state variables along with their initial values.
14957 Their current values may also be displayed, if the trace experiment is
14960 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14961 @kindex delete tvariable
14962 Delete the given trace state variables, or all of them if no arguments
14967 @node Tracepoint Actions
14968 @subsection Tracepoint Action Lists
14972 @cindex tracepoint actions
14973 @item actions @r{[}@var{num}@r{]}
14974 This command will prompt for a list of actions to be taken when the
14975 tracepoint is hit. If the tracepoint number @var{num} is not
14976 specified, this command sets the actions for the one that was most
14977 recently defined (so that you can define a tracepoint and then say
14978 @code{actions} without bothering about its number). You specify the
14979 actions themselves on the following lines, one action at a time, and
14980 terminate the actions list with a line containing just @code{end}. So
14981 far, the only defined actions are @code{collect}, @code{teval}, and
14982 @code{while-stepping}.
14984 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14985 Commands, ,Breakpoint Command Lists}), except that only the defined
14986 actions are allowed; any other @value{GDBN} command is rejected.
14988 @cindex remove actions from a tracepoint
14989 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14990 and follow it immediately with @samp{end}.
14993 (@value{GDBP}) @b{collect @var{data}} // collect some data
14995 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14997 (@value{GDBP}) @b{end} // signals the end of actions.
15000 In the following example, the action list begins with @code{collect}
15001 commands indicating the things to be collected when the tracepoint is
15002 hit. Then, in order to single-step and collect additional data
15003 following the tracepoint, a @code{while-stepping} command is used,
15004 followed by the list of things to be collected after each step in a
15005 sequence of single steps. The @code{while-stepping} command is
15006 terminated by its own separate @code{end} command. Lastly, the action
15007 list is terminated by an @code{end} command.
15010 (@value{GDBP}) @b{trace foo}
15011 (@value{GDBP}) @b{actions}
15012 Enter actions for tracepoint 1, one per line:
15015 > while-stepping 12
15016 > collect $pc, arr[i]
15021 @kindex collect @r{(tracepoints)}
15022 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
15023 Collect values of the given expressions when the tracepoint is hit.
15024 This command accepts a comma-separated list of any valid expressions.
15025 In addition to global, static, or local variables, the following
15026 special arguments are supported:
15030 Collect all registers.
15033 Collect all function arguments.
15036 Collect all local variables.
15039 Collect the return address. This is helpful if you want to see more
15042 @emph{Note:} The return address location can not always be reliably
15043 determined up front, and the wrong address / registers may end up
15044 collected instead. On some architectures the reliability is higher
15045 for tracepoints at function entry, while on others it's the opposite.
15046 When this happens, backtracing will stop because the return address is
15047 found unavailable (unless another collect rule happened to match it).
15050 Collects the number of arguments from the static probe at which the
15051 tracepoint is located.
15052 @xref{Static Probe Points}.
15054 @item $_probe_arg@var{n}
15055 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
15056 from the static probe at which the tracepoint is located.
15057 @xref{Static Probe Points}.
15060 @vindex $_sdata@r{, collect}
15061 Collect static tracepoint marker specific data. Only available for
15062 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
15063 Lists}. On the UST static tracepoints library backend, an
15064 instrumentation point resembles a @code{printf} function call. The
15065 tracing library is able to collect user specified data formatted to a
15066 character string using the format provided by the programmer that
15067 instrumented the program. Other backends have similar mechanisms.
15068 Here's an example of a UST marker call:
15071 const char master_name[] = "$your_name";
15072 trace_mark(channel1, marker1, "hello %s", master_name)
15075 In this case, collecting @code{$_sdata} collects the string
15076 @samp{hello $yourname}. When analyzing the trace buffer, you can
15077 inspect @samp{$_sdata} like any other variable available to
15081 You can give several consecutive @code{collect} commands, each one
15082 with a single argument, or one @code{collect} command with several
15083 arguments separated by commas; the effect is the same.
15085 The optional @var{mods} changes the usual handling of the arguments.
15086 @code{s} requests that pointers to chars be handled as strings, in
15087 particular collecting the contents of the memory being pointed at, up
15088 to the first zero. The upper bound is by default the value of the
15089 @code{print elements} variable; if @code{s} is followed by a decimal
15090 number, that is the upper bound instead. So for instance
15091 @samp{collect/s25 mystr} collects as many as 25 characters at
15094 The command @code{info scope} (@pxref{Symbols, info scope}) is
15095 particularly useful for figuring out what data to collect.
15097 @kindex teval @r{(tracepoints)}
15098 @item teval @var{expr1}, @var{expr2}, @dots{}
15099 Evaluate the given expressions when the tracepoint is hit. This
15100 command accepts a comma-separated list of expressions. The results
15101 are discarded, so this is mainly useful for assigning values to trace
15102 state variables (@pxref{Trace State Variables}) without adding those
15103 values to the trace buffer, as would be the case if the @code{collect}
15106 @kindex while-stepping @r{(tracepoints)}
15107 @item while-stepping @var{n}
15108 Perform @var{n} single-step instruction traces after the tracepoint,
15109 collecting new data after each step. The @code{while-stepping}
15110 command is followed by the list of what to collect while stepping
15111 (followed by its own @code{end} command):
15114 > while-stepping 12
15115 > collect $regs, myglobal
15121 Note that @code{$pc} is not automatically collected by
15122 @code{while-stepping}; you need to explicitly collect that register if
15123 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
15126 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
15127 @kindex set default-collect
15128 @cindex default collection action
15129 This variable is a list of expressions to collect at each tracepoint
15130 hit. It is effectively an additional @code{collect} action prepended
15131 to every tracepoint action list. The expressions are parsed
15132 individually for each tracepoint, so for instance a variable named
15133 @code{xyz} may be interpreted as a global for one tracepoint, and a
15134 local for another, as appropriate to the tracepoint's location.
15136 @item show default-collect
15137 @kindex show default-collect
15138 Show the list of expressions that are collected by default at each
15143 @node Listing Tracepoints
15144 @subsection Listing Tracepoints
15147 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
15148 @kindex info tp @r{[}@var{n}@dots{}@r{]}
15149 @cindex information about tracepoints
15150 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
15151 Display information about the tracepoint @var{num}. If you don't
15152 specify a tracepoint number, displays information about all the
15153 tracepoints defined so far. The format is similar to that used for
15154 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
15155 command, simply restricting itself to tracepoints.
15157 A tracepoint's listing may include additional information specific to
15162 its passcount as given by the @code{passcount @var{n}} command
15165 the state about installed on target of each location
15169 (@value{GDBP}) @b{info trace}
15170 Num Type Disp Enb Address What
15171 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
15173 collect globfoo, $regs
15178 2 tracepoint keep y <MULTIPLE>
15180 2.1 y 0x0804859c in func4 at change-loc.h:35
15181 installed on target
15182 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
15183 installed on target
15184 2.3 y <PENDING> set_tracepoint
15185 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
15186 not installed on target
15191 This command can be abbreviated @code{info tp}.
15194 @node Listing Static Tracepoint Markers
15195 @subsection Listing Static Tracepoint Markers
15198 @kindex info static-tracepoint-markers
15199 @cindex information about static tracepoint markers
15200 @item info static-tracepoint-markers
15201 Display information about all static tracepoint markers defined in the
15204 For each marker, the following columns are printed:
15208 An incrementing counter, output to help readability. This is not a
15211 The marker ID, as reported by the target.
15212 @item Enabled or Disabled
15213 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15214 that are not enabled.
15216 Where the marker is in your program, as a memory address.
15218 Where the marker is in the source for your program, as a file and line
15219 number. If the debug information included in the program does not
15220 allow @value{GDBN} to locate the source of the marker, this column
15221 will be left blank.
15225 In addition, the following information may be printed for each marker:
15229 User data passed to the tracing library by the marker call. In the
15230 UST backend, this is the format string passed as argument to the
15232 @item Static tracepoints probing the marker
15233 The list of static tracepoints attached to the marker.
15237 (@value{GDBP}) info static-tracepoint-markers
15238 Cnt ID Enb Address What
15239 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15240 Data: number1 %d number2 %d
15241 Probed by static tracepoints: #2
15242 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15248 @node Starting and Stopping Trace Experiments
15249 @subsection Starting and Stopping Trace Experiments
15252 @kindex tstart [ @var{notes} ]
15253 @cindex start a new trace experiment
15254 @cindex collected data discarded
15256 This command starts the trace experiment, and begins collecting data.
15257 It has the side effect of discarding all the data collected in the
15258 trace buffer during the previous trace experiment. If any arguments
15259 are supplied, they are taken as a note and stored with the trace
15260 experiment's state. The notes may be arbitrary text, and are
15261 especially useful with disconnected tracing in a multi-user context;
15262 the notes can explain what the trace is doing, supply user contact
15263 information, and so forth.
15265 @kindex tstop [ @var{notes} ]
15266 @cindex stop a running trace experiment
15268 This command stops the trace experiment. If any arguments are
15269 supplied, they are recorded with the experiment as a note. This is
15270 useful if you are stopping a trace started by someone else, for
15271 instance if the trace is interfering with the system's behavior and
15272 needs to be stopped quickly.
15274 @strong{Note}: a trace experiment and data collection may stop
15275 automatically if any tracepoint's passcount is reached
15276 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15279 @cindex status of trace data collection
15280 @cindex trace experiment, status of
15282 This command displays the status of the current trace data
15286 Here is an example of the commands we described so far:
15289 (@value{GDBP}) @b{trace gdb_c_test}
15290 (@value{GDBP}) @b{actions}
15291 Enter actions for tracepoint #1, one per line.
15292 > collect $regs,$locals,$args
15293 > while-stepping 11
15297 (@value{GDBP}) @b{tstart}
15298 [time passes @dots{}]
15299 (@value{GDBP}) @b{tstop}
15302 @anchor{disconnected tracing}
15303 @cindex disconnected tracing
15304 You can choose to continue running the trace experiment even if
15305 @value{GDBN} disconnects from the target, voluntarily or
15306 involuntarily. For commands such as @code{detach}, the debugger will
15307 ask what you want to do with the trace. But for unexpected
15308 terminations (@value{GDBN} crash, network outage), it would be
15309 unfortunate to lose hard-won trace data, so the variable
15310 @code{disconnected-tracing} lets you decide whether the trace should
15311 continue running without @value{GDBN}.
15314 @item set disconnected-tracing on
15315 @itemx set disconnected-tracing off
15316 @kindex set disconnected-tracing
15317 Choose whether a tracing run should continue to run if @value{GDBN}
15318 has disconnected from the target. Note that @code{detach} or
15319 @code{quit} will ask you directly what to do about a running trace no
15320 matter what this variable's setting, so the variable is mainly useful
15321 for handling unexpected situations, such as loss of the network.
15323 @item show disconnected-tracing
15324 @kindex show disconnected-tracing
15325 Show the current choice for disconnected tracing.
15329 When you reconnect to the target, the trace experiment may or may not
15330 still be running; it might have filled the trace buffer in the
15331 meantime, or stopped for one of the other reasons. If it is running,
15332 it will continue after reconnection.
15334 Upon reconnection, the target will upload information about the
15335 tracepoints in effect. @value{GDBN} will then compare that
15336 information to the set of tracepoints currently defined, and attempt
15337 to match them up, allowing for the possibility that the numbers may
15338 have changed due to creation and deletion in the meantime. If one of
15339 the target's tracepoints does not match any in @value{GDBN}, the
15340 debugger will create a new tracepoint, so that you have a number with
15341 which to specify that tracepoint. This matching-up process is
15342 necessarily heuristic, and it may result in useless tracepoints being
15343 created; you may simply delete them if they are of no use.
15345 @cindex circular trace buffer
15346 If your target agent supports a @dfn{circular trace buffer}, then you
15347 can run a trace experiment indefinitely without filling the trace
15348 buffer; when space runs out, the agent deletes already-collected trace
15349 frames, oldest first, until there is enough room to continue
15350 collecting. This is especially useful if your tracepoints are being
15351 hit too often, and your trace gets terminated prematurely because the
15352 buffer is full. To ask for a circular trace buffer, simply set
15353 @samp{circular-trace-buffer} to on. You can set this at any time,
15354 including during tracing; if the agent can do it, it will change
15355 buffer handling on the fly, otherwise it will not take effect until
15359 @item set circular-trace-buffer on
15360 @itemx set circular-trace-buffer off
15361 @kindex set circular-trace-buffer
15362 Choose whether a tracing run should use a linear or circular buffer
15363 for trace data. A linear buffer will not lose any trace data, but may
15364 fill up prematurely, while a circular buffer will discard old trace
15365 data, but it will have always room for the latest tracepoint hits.
15367 @item show circular-trace-buffer
15368 @kindex show circular-trace-buffer
15369 Show the current choice for the trace buffer. Note that this may not
15370 match the agent's current buffer handling, nor is it guaranteed to
15371 match the setting that might have been in effect during a past run,
15372 for instance if you are looking at frames from a trace file.
15377 @item set trace-buffer-size @var{n}
15378 @itemx set trace-buffer-size unlimited
15379 @kindex set trace-buffer-size
15380 Request that the target use a trace buffer of @var{n} bytes. Not all
15381 targets will honor the request; they may have a compiled-in size for
15382 the trace buffer, or some other limitation. Set to a value of
15383 @code{unlimited} or @code{-1} to let the target use whatever size it
15384 likes. This is also the default.
15386 @item show trace-buffer-size
15387 @kindex show trace-buffer-size
15388 Show the current requested size for the trace buffer. Note that this
15389 will only match the actual size if the target supports size-setting,
15390 and was able to handle the requested size. For instance, if the
15391 target can only change buffer size between runs, this variable will
15392 not reflect the change until the next run starts. Use @code{tstatus}
15393 to get a report of the actual buffer size.
15397 @item set trace-user @var{text}
15398 @kindex set trace-user
15400 @item show trace-user
15401 @kindex show trace-user
15403 @item set trace-notes @var{text}
15404 @kindex set trace-notes
15405 Set the trace run's notes.
15407 @item show trace-notes
15408 @kindex show trace-notes
15409 Show the trace run's notes.
15411 @item set trace-stop-notes @var{text}
15412 @kindex set trace-stop-notes
15413 Set the trace run's stop notes. The handling of the note is as for
15414 @code{tstop} arguments; the set command is convenient way to fix a
15415 stop note that is mistaken or incomplete.
15417 @item show trace-stop-notes
15418 @kindex show trace-stop-notes
15419 Show the trace run's stop notes.
15423 @node Tracepoint Restrictions
15424 @subsection Tracepoint Restrictions
15426 @cindex tracepoint restrictions
15427 There are a number of restrictions on the use of tracepoints. As
15428 described above, tracepoint data gathering occurs on the target
15429 without interaction from @value{GDBN}. Thus the full capabilities of
15430 the debugger are not available during data gathering, and then at data
15431 examination time, you will be limited by only having what was
15432 collected. The following items describe some common problems, but it
15433 is not exhaustive, and you may run into additional difficulties not
15439 Tracepoint expressions are intended to gather objects (lvalues). Thus
15440 the full flexibility of GDB's expression evaluator is not available.
15441 You cannot call functions, cast objects to aggregate types, access
15442 convenience variables or modify values (except by assignment to trace
15443 state variables). Some language features may implicitly call
15444 functions (for instance Objective-C fields with accessors), and therefore
15445 cannot be collected either.
15448 Collection of local variables, either individually or in bulk with
15449 @code{$locals} or @code{$args}, during @code{while-stepping} may
15450 behave erratically. The stepping action may enter a new scope (for
15451 instance by stepping into a function), or the location of the variable
15452 may change (for instance it is loaded into a register). The
15453 tracepoint data recorded uses the location information for the
15454 variables that is correct for the tracepoint location. When the
15455 tracepoint is created, it is not possible, in general, to determine
15456 where the steps of a @code{while-stepping} sequence will advance the
15457 program---particularly if a conditional branch is stepped.
15460 Collection of an incompletely-initialized or partially-destroyed object
15461 may result in something that @value{GDBN} cannot display, or displays
15462 in a misleading way.
15465 When @value{GDBN} displays a pointer to character it automatically
15466 dereferences the pointer to also display characters of the string
15467 being pointed to. However, collecting the pointer during tracing does
15468 not automatically collect the string. You need to explicitly
15469 dereference the pointer and provide size information if you want to
15470 collect not only the pointer, but the memory pointed to. For example,
15471 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15475 It is not possible to collect a complete stack backtrace at a
15476 tracepoint. Instead, you may collect the registers and a few hundred
15477 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15478 (adjust to use the name of the actual stack pointer register on your
15479 target architecture, and the amount of stack you wish to capture).
15480 Then the @code{backtrace} command will show a partial backtrace when
15481 using a trace frame. The number of stack frames that can be examined
15482 depends on the sizes of the frames in the collected stack. Note that
15483 if you ask for a block so large that it goes past the bottom of the
15484 stack, the target agent may report an error trying to read from an
15488 If you do not collect registers at a tracepoint, @value{GDBN} can
15489 infer that the value of @code{$pc} must be the same as the address of
15490 the tracepoint and use that when you are looking at a trace frame
15491 for that tracepoint. However, this cannot work if the tracepoint has
15492 multiple locations (for instance if it was set in a function that was
15493 inlined), or if it has a @code{while-stepping} loop. In those cases
15494 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15499 @node Analyze Collected Data
15500 @section Using the Collected Data
15502 After the tracepoint experiment ends, you use @value{GDBN} commands
15503 for examining the trace data. The basic idea is that each tracepoint
15504 collects a trace @dfn{snapshot} every time it is hit and another
15505 snapshot every time it single-steps. All these snapshots are
15506 consecutively numbered from zero and go into a buffer, and you can
15507 examine them later. The way you examine them is to @dfn{focus} on a
15508 specific trace snapshot. When the remote stub is focused on a trace
15509 snapshot, it will respond to all @value{GDBN} requests for memory and
15510 registers by reading from the buffer which belongs to that snapshot,
15511 rather than from @emph{real} memory or registers of the program being
15512 debugged. This means that @strong{all} @value{GDBN} commands
15513 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15514 behave as if we were currently debugging the program state as it was
15515 when the tracepoint occurred. Any requests for data that are not in
15516 the buffer will fail.
15519 * tfind:: How to select a trace snapshot
15520 * tdump:: How to display all data for a snapshot
15521 * save tracepoints:: How to save tracepoints for a future run
15525 @subsection @code{tfind @var{n}}
15528 @cindex select trace snapshot
15529 @cindex find trace snapshot
15530 The basic command for selecting a trace snapshot from the buffer is
15531 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15532 counting from zero. If no argument @var{n} is given, the next
15533 snapshot is selected.
15535 Here are the various forms of using the @code{tfind} command.
15539 Find the first snapshot in the buffer. This is a synonym for
15540 @code{tfind 0} (since 0 is the number of the first snapshot).
15543 Stop debugging trace snapshots, resume @emph{live} debugging.
15546 Same as @samp{tfind none}.
15549 No argument means find the next trace snapshot or find the first
15550 one if no trace snapshot is selected.
15553 Find the previous trace snapshot before the current one. This permits
15554 retracing earlier steps.
15556 @item tfind tracepoint @var{num}
15557 Find the next snapshot associated with tracepoint @var{num}. Search
15558 proceeds forward from the last examined trace snapshot. If no
15559 argument @var{num} is given, it means find the next snapshot collected
15560 for the same tracepoint as the current snapshot.
15562 @item tfind pc @var{addr}
15563 Find the next snapshot associated with the value @var{addr} of the
15564 program counter. Search proceeds forward from the last examined trace
15565 snapshot. If no argument @var{addr} is given, it means find the next
15566 snapshot with the same value of PC as the current snapshot.
15568 @item tfind outside @var{addr1}, @var{addr2}
15569 Find the next snapshot whose PC is outside the given range of
15570 addresses (exclusive).
15572 @item tfind range @var{addr1}, @var{addr2}
15573 Find the next snapshot whose PC is between @var{addr1} and
15574 @var{addr2} (inclusive).
15576 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15577 Find the next snapshot associated with the source line @var{n}. If
15578 the optional argument @var{file} is given, refer to line @var{n} in
15579 that source file. Search proceeds forward from the last examined
15580 trace snapshot. If no argument @var{n} is given, it means find the
15581 next line other than the one currently being examined; thus saying
15582 @code{tfind line} repeatedly can appear to have the same effect as
15583 stepping from line to line in a @emph{live} debugging session.
15586 The default arguments for the @code{tfind} commands are specifically
15587 designed to make it easy to scan through the trace buffer. For
15588 instance, @code{tfind} with no argument selects the next trace
15589 snapshot, and @code{tfind -} with no argument selects the previous
15590 trace snapshot. So, by giving one @code{tfind} command, and then
15591 simply hitting @key{RET} repeatedly you can examine all the trace
15592 snapshots in order. Or, by saying @code{tfind -} and then hitting
15593 @key{RET} repeatedly you can examine the snapshots in reverse order.
15594 The @code{tfind line} command with no argument selects the snapshot
15595 for the next source line executed. The @code{tfind pc} command with
15596 no argument selects the next snapshot with the same program counter
15597 (PC) as the current frame. The @code{tfind tracepoint} command with
15598 no argument selects the next trace snapshot collected by the same
15599 tracepoint as the current one.
15601 In addition to letting you scan through the trace buffer manually,
15602 these commands make it easy to construct @value{GDBN} scripts that
15603 scan through the trace buffer and print out whatever collected data
15604 you are interested in. Thus, if we want to examine the PC, FP, and SP
15605 registers from each trace frame in the buffer, we can say this:
15608 (@value{GDBP}) @b{tfind start}
15609 (@value{GDBP}) @b{while ($trace_frame != -1)}
15610 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15611 $trace_frame, $pc, $sp, $fp
15615 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15616 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15617 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15618 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15619 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15620 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15621 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15622 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15623 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15624 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15625 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15628 Or, if we want to examine the variable @code{X} at each source line in
15632 (@value{GDBP}) @b{tfind start}
15633 (@value{GDBP}) @b{while ($trace_frame != -1)}
15634 > printf "Frame %d, X == %d\n", $trace_frame, X
15644 @subsection @code{tdump}
15646 @cindex dump all data collected at tracepoint
15647 @cindex tracepoint data, display
15649 This command takes no arguments. It prints all the data collected at
15650 the current trace snapshot.
15653 (@value{GDBP}) @b{trace 444}
15654 (@value{GDBP}) @b{actions}
15655 Enter actions for tracepoint #2, one per line:
15656 > collect $regs, $locals, $args, gdb_long_test
15659 (@value{GDBP}) @b{tstart}
15661 (@value{GDBP}) @b{tfind line 444}
15662 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15664 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15666 (@value{GDBP}) @b{tdump}
15667 Data collected at tracepoint 2, trace frame 1:
15668 d0 0xc4aa0085 -995491707
15672 d4 0x71aea3d 119204413
15675 d7 0x380035 3670069
15676 a0 0x19e24a 1696330
15677 a1 0x3000668 50333288
15679 a3 0x322000 3284992
15680 a4 0x3000698 50333336
15681 a5 0x1ad3cc 1758156
15682 fp 0x30bf3c 0x30bf3c
15683 sp 0x30bf34 0x30bf34
15685 pc 0x20b2c8 0x20b2c8
15689 p = 0x20e5b4 "gdb-test"
15696 gdb_long_test = 17 '\021'
15701 @code{tdump} works by scanning the tracepoint's current collection
15702 actions and printing the value of each expression listed. So
15703 @code{tdump} can fail, if after a run, you change the tracepoint's
15704 actions to mention variables that were not collected during the run.
15706 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15707 uses the collected value of @code{$pc} to distinguish between trace
15708 frames that were collected at the tracepoint hit, and frames that were
15709 collected while stepping. This allows it to correctly choose whether
15710 to display the basic list of collections, or the collections from the
15711 body of the while-stepping loop. However, if @code{$pc} was not collected,
15712 then @code{tdump} will always attempt to dump using the basic collection
15713 list, and may fail if a while-stepping frame does not include all the
15714 same data that is collected at the tracepoint hit.
15715 @c This is getting pretty arcane, example would be good.
15717 @node save tracepoints
15718 @subsection @code{save tracepoints @var{filename}}
15719 @kindex save tracepoints
15720 @kindex save-tracepoints
15721 @cindex save tracepoints for future sessions
15723 This command saves all current tracepoint definitions together with
15724 their actions and passcounts, into a file @file{@var{filename}}
15725 suitable for use in a later debugging session. To read the saved
15726 tracepoint definitions, use the @code{source} command (@pxref{Command
15727 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15728 alias for @w{@code{save tracepoints}}
15730 @node Tracepoint Variables
15731 @section Convenience Variables for Tracepoints
15732 @cindex tracepoint variables
15733 @cindex convenience variables for tracepoints
15736 @vindex $trace_frame
15737 @item (int) $trace_frame
15738 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15739 snapshot is selected.
15741 @vindex $tracepoint
15742 @item (int) $tracepoint
15743 The tracepoint for the current trace snapshot.
15745 @vindex $trace_line
15746 @item (int) $trace_line
15747 The line number for the current trace snapshot.
15749 @vindex $trace_file
15750 @item (char []) $trace_file
15751 The source file for the current trace snapshot.
15753 @vindex $trace_func
15754 @item (char []) $trace_func
15755 The name of the function containing @code{$tracepoint}.
15758 Note: @code{$trace_file} is not suitable for use in @code{printf},
15759 use @code{output} instead.
15761 Here's a simple example of using these convenience variables for
15762 stepping through all the trace snapshots and printing some of their
15763 data. Note that these are not the same as trace state variables,
15764 which are managed by the target.
15767 (@value{GDBP}) @b{tfind start}
15769 (@value{GDBP}) @b{while $trace_frame != -1}
15770 > output $trace_file
15771 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15777 @section Using Trace Files
15778 @cindex trace files
15780 In some situations, the target running a trace experiment may no
15781 longer be available; perhaps it crashed, or the hardware was needed
15782 for a different activity. To handle these cases, you can arrange to
15783 dump the trace data into a file, and later use that file as a source
15784 of trace data, via the @code{target tfile} command.
15789 @item tsave [ -r ] @var{filename}
15790 @itemx tsave [-ctf] @var{dirname}
15791 Save the trace data to @var{filename}. By default, this command
15792 assumes that @var{filename} refers to the host filesystem, so if
15793 necessary @value{GDBN} will copy raw trace data up from the target and
15794 then save it. If the target supports it, you can also supply the
15795 optional argument @code{-r} (``remote'') to direct the target to save
15796 the data directly into @var{filename} in its own filesystem, which may be
15797 more efficient if the trace buffer is very large. (Note, however, that
15798 @code{target tfile} can only read from files accessible to the host.)
15799 By default, this command will save trace frame in tfile format.
15800 You can supply the optional argument @code{-ctf} to save data in CTF
15801 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15802 that can be shared by multiple debugging and tracing tools. Please go to
15803 @indicateurl{http://www.efficios.com/ctf} to get more information.
15805 @kindex target tfile
15809 @item target tfile @var{filename}
15810 @itemx target ctf @var{dirname}
15811 Use the file named @var{filename} or directory named @var{dirname} as
15812 a source of trace data. Commands that examine data work as they do with
15813 a live target, but it is not possible to run any new trace experiments.
15814 @code{tstatus} will report the state of the trace run at the moment
15815 the data was saved, as well as the current trace frame you are examining.
15816 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15820 (@value{GDBP}) target ctf ctf.ctf
15821 (@value{GDBP}) tfind
15822 Found trace frame 0, tracepoint 2
15823 39 ++a; /* set tracepoint 1 here */
15824 (@value{GDBP}) tdump
15825 Data collected at tracepoint 2, trace frame 0:
15829 c = @{"123", "456", "789", "123", "456", "789"@}
15830 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15838 @chapter Debugging Programs That Use Overlays
15841 If your program is too large to fit completely in your target system's
15842 memory, you can sometimes use @dfn{overlays} to work around this
15843 problem. @value{GDBN} provides some support for debugging programs that
15847 * How Overlays Work:: A general explanation of overlays.
15848 * Overlay Commands:: Managing overlays in @value{GDBN}.
15849 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15850 mapped by asking the inferior.
15851 * Overlay Sample Program:: A sample program using overlays.
15854 @node How Overlays Work
15855 @section How Overlays Work
15856 @cindex mapped overlays
15857 @cindex unmapped overlays
15858 @cindex load address, overlay's
15859 @cindex mapped address
15860 @cindex overlay area
15862 Suppose you have a computer whose instruction address space is only 64
15863 kilobytes long, but which has much more memory which can be accessed by
15864 other means: special instructions, segment registers, or memory
15865 management hardware, for example. Suppose further that you want to
15866 adapt a program which is larger than 64 kilobytes to run on this system.
15868 One solution is to identify modules of your program which are relatively
15869 independent, and need not call each other directly; call these modules
15870 @dfn{overlays}. Separate the overlays from the main program, and place
15871 their machine code in the larger memory. Place your main program in
15872 instruction memory, but leave at least enough space there to hold the
15873 largest overlay as well.
15875 Now, to call a function located in an overlay, you must first copy that
15876 overlay's machine code from the large memory into the space set aside
15877 for it in the instruction memory, and then jump to its entry point
15880 @c NB: In the below the mapped area's size is greater or equal to the
15881 @c size of all overlays. This is intentional to remind the developer
15882 @c that overlays don't necessarily need to be the same size.
15886 Data Instruction Larger
15887 Address Space Address Space Address Space
15888 +-----------+ +-----------+ +-----------+
15890 +-----------+ +-----------+ +-----------+<-- overlay 1
15891 | program | | main | .----| overlay 1 | load address
15892 | variables | | program | | +-----------+
15893 | and heap | | | | | |
15894 +-----------+ | | | +-----------+<-- overlay 2
15895 | | +-----------+ | | | load address
15896 +-----------+ | | | .-| overlay 2 |
15898 mapped --->+-----------+ | | +-----------+
15899 address | | | | | |
15900 | overlay | <-' | | |
15901 | area | <---' +-----------+<-- overlay 3
15902 | | <---. | | load address
15903 +-----------+ `--| overlay 3 |
15910 @anchor{A code overlay}A code overlay
15914 The diagram (@pxref{A code overlay}) shows a system with separate data
15915 and instruction address spaces. To map an overlay, the program copies
15916 its code from the larger address space to the instruction address space.
15917 Since the overlays shown here all use the same mapped address, only one
15918 may be mapped at a time. For a system with a single address space for
15919 data and instructions, the diagram would be similar, except that the
15920 program variables and heap would share an address space with the main
15921 program and the overlay area.
15923 An overlay loaded into instruction memory and ready for use is called a
15924 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15925 instruction memory. An overlay not present (or only partially present)
15926 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15927 is its address in the larger memory. The mapped address is also called
15928 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15929 called the @dfn{load memory address}, or @dfn{LMA}.
15931 Unfortunately, overlays are not a completely transparent way to adapt a
15932 program to limited instruction memory. They introduce a new set of
15933 global constraints you must keep in mind as you design your program:
15938 Before calling or returning to a function in an overlay, your program
15939 must make sure that overlay is actually mapped. Otherwise, the call or
15940 return will transfer control to the right address, but in the wrong
15941 overlay, and your program will probably crash.
15944 If the process of mapping an overlay is expensive on your system, you
15945 will need to choose your overlays carefully to minimize their effect on
15946 your program's performance.
15949 The executable file you load onto your system must contain each
15950 overlay's instructions, appearing at the overlay's load address, not its
15951 mapped address. However, each overlay's instructions must be relocated
15952 and its symbols defined as if the overlay were at its mapped address.
15953 You can use GNU linker scripts to specify different load and relocation
15954 addresses for pieces of your program; see @ref{Overlay Description,,,
15955 ld.info, Using ld: the GNU linker}.
15958 The procedure for loading executable files onto your system must be able
15959 to load their contents into the larger address space as well as the
15960 instruction and data spaces.
15964 The overlay system described above is rather simple, and could be
15965 improved in many ways:
15970 If your system has suitable bank switch registers or memory management
15971 hardware, you could use those facilities to make an overlay's load area
15972 contents simply appear at their mapped address in instruction space.
15973 This would probably be faster than copying the overlay to its mapped
15974 area in the usual way.
15977 If your overlays are small enough, you could set aside more than one
15978 overlay area, and have more than one overlay mapped at a time.
15981 You can use overlays to manage data, as well as instructions. In
15982 general, data overlays are even less transparent to your design than
15983 code overlays: whereas code overlays only require care when you call or
15984 return to functions, data overlays require care every time you access
15985 the data. Also, if you change the contents of a data overlay, you
15986 must copy its contents back out to its load address before you can copy a
15987 different data overlay into the same mapped area.
15992 @node Overlay Commands
15993 @section Overlay Commands
15995 To use @value{GDBN}'s overlay support, each overlay in your program must
15996 correspond to a separate section of the executable file. The section's
15997 virtual memory address and load memory address must be the overlay's
15998 mapped and load addresses. Identifying overlays with sections allows
15999 @value{GDBN} to determine the appropriate address of a function or
16000 variable, depending on whether the overlay is mapped or not.
16002 @value{GDBN}'s overlay commands all start with the word @code{overlay};
16003 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
16008 Disable @value{GDBN}'s overlay support. When overlay support is
16009 disabled, @value{GDBN} assumes that all functions and variables are
16010 always present at their mapped addresses. By default, @value{GDBN}'s
16011 overlay support is disabled.
16013 @item overlay manual
16014 @cindex manual overlay debugging
16015 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
16016 relies on you to tell it which overlays are mapped, and which are not,
16017 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
16018 commands described below.
16020 @item overlay map-overlay @var{overlay}
16021 @itemx overlay map @var{overlay}
16022 @cindex map an overlay
16023 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
16024 be the name of the object file section containing the overlay. When an
16025 overlay is mapped, @value{GDBN} assumes it can find the overlay's
16026 functions and variables at their mapped addresses. @value{GDBN} assumes
16027 that any other overlays whose mapped ranges overlap that of
16028 @var{overlay} are now unmapped.
16030 @item overlay unmap-overlay @var{overlay}
16031 @itemx overlay unmap @var{overlay}
16032 @cindex unmap an overlay
16033 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
16034 must be the name of the object file section containing the overlay.
16035 When an overlay is unmapped, @value{GDBN} assumes it can find the
16036 overlay's functions and variables at their load addresses.
16039 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
16040 consults a data structure the overlay manager maintains in the inferior
16041 to see which overlays are mapped. For details, see @ref{Automatic
16042 Overlay Debugging}.
16044 @item overlay load-target
16045 @itemx overlay load
16046 @cindex reloading the overlay table
16047 Re-read the overlay table from the inferior. Normally, @value{GDBN}
16048 re-reads the table @value{GDBN} automatically each time the inferior
16049 stops, so this command should only be necessary if you have changed the
16050 overlay mapping yourself using @value{GDBN}. This command is only
16051 useful when using automatic overlay debugging.
16053 @item overlay list-overlays
16054 @itemx overlay list
16055 @cindex listing mapped overlays
16056 Display a list of the overlays currently mapped, along with their mapped
16057 addresses, load addresses, and sizes.
16061 Normally, when @value{GDBN} prints a code address, it includes the name
16062 of the function the address falls in:
16065 (@value{GDBP}) print main
16066 $3 = @{int ()@} 0x11a0 <main>
16069 When overlay debugging is enabled, @value{GDBN} recognizes code in
16070 unmapped overlays, and prints the names of unmapped functions with
16071 asterisks around them. For example, if @code{foo} is a function in an
16072 unmapped overlay, @value{GDBN} prints it this way:
16075 (@value{GDBP}) overlay list
16076 No sections are mapped.
16077 (@value{GDBP}) print foo
16078 $5 = @{int (int)@} 0x100000 <*foo*>
16081 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
16085 (@value{GDBP}) overlay list
16086 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
16087 mapped at 0x1016 - 0x104a
16088 (@value{GDBP}) print foo
16089 $6 = @{int (int)@} 0x1016 <foo>
16092 When overlay debugging is enabled, @value{GDBN} can find the correct
16093 address for functions and variables in an overlay, whether or not the
16094 overlay is mapped. This allows most @value{GDBN} commands, like
16095 @code{break} and @code{disassemble}, to work normally, even on unmapped
16096 code. However, @value{GDBN}'s breakpoint support has some limitations:
16100 @cindex breakpoints in overlays
16101 @cindex overlays, setting breakpoints in
16102 You can set breakpoints in functions in unmapped overlays, as long as
16103 @value{GDBN} can write to the overlay at its load address.
16105 @value{GDBN} can not set hardware or simulator-based breakpoints in
16106 unmapped overlays. However, if you set a breakpoint at the end of your
16107 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
16108 you are using manual overlay management), @value{GDBN} will re-set its
16109 breakpoints properly.
16113 @node Automatic Overlay Debugging
16114 @section Automatic Overlay Debugging
16115 @cindex automatic overlay debugging
16117 @value{GDBN} can automatically track which overlays are mapped and which
16118 are not, given some simple co-operation from the overlay manager in the
16119 inferior. If you enable automatic overlay debugging with the
16120 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
16121 looks in the inferior's memory for certain variables describing the
16122 current state of the overlays.
16124 Here are the variables your overlay manager must define to support
16125 @value{GDBN}'s automatic overlay debugging:
16129 @item @code{_ovly_table}:
16130 This variable must be an array of the following structures:
16135 /* The overlay's mapped address. */
16138 /* The size of the overlay, in bytes. */
16139 unsigned long size;
16141 /* The overlay's load address. */
16144 /* Non-zero if the overlay is currently mapped;
16146 unsigned long mapped;
16150 @item @code{_novlys}:
16151 This variable must be a four-byte signed integer, holding the total
16152 number of elements in @code{_ovly_table}.
16156 To decide whether a particular overlay is mapped or not, @value{GDBN}
16157 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
16158 @code{lma} members equal the VMA and LMA of the overlay's section in the
16159 executable file. When @value{GDBN} finds a matching entry, it consults
16160 the entry's @code{mapped} member to determine whether the overlay is
16163 In addition, your overlay manager may define a function called
16164 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
16165 will silently set a breakpoint there. If the overlay manager then
16166 calls this function whenever it has changed the overlay table, this
16167 will enable @value{GDBN} to accurately keep track of which overlays
16168 are in program memory, and update any breakpoints that may be set
16169 in overlays. This will allow breakpoints to work even if the
16170 overlays are kept in ROM or other non-writable memory while they
16171 are not being executed.
16173 @node Overlay Sample Program
16174 @section Overlay Sample Program
16175 @cindex overlay example program
16177 When linking a program which uses overlays, you must place the overlays
16178 at their load addresses, while relocating them to run at their mapped
16179 addresses. To do this, you must write a linker script (@pxref{Overlay
16180 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
16181 since linker scripts are specific to a particular host system, target
16182 architecture, and target memory layout, this manual cannot provide
16183 portable sample code demonstrating @value{GDBN}'s overlay support.
16185 However, the @value{GDBN} source distribution does contain an overlaid
16186 program, with linker scripts for a few systems, as part of its test
16187 suite. The program consists of the following files from
16188 @file{gdb/testsuite/gdb.base}:
16192 The main program file.
16194 A simple overlay manager, used by @file{overlays.c}.
16199 Overlay modules, loaded and used by @file{overlays.c}.
16202 Linker scripts for linking the test program on the @code{d10v-elf}
16203 and @code{m32r-elf} targets.
16206 You can build the test program using the @code{d10v-elf} GCC
16207 cross-compiler like this:
16210 $ d10v-elf-gcc -g -c overlays.c
16211 $ d10v-elf-gcc -g -c ovlymgr.c
16212 $ d10v-elf-gcc -g -c foo.c
16213 $ d10v-elf-gcc -g -c bar.c
16214 $ d10v-elf-gcc -g -c baz.c
16215 $ d10v-elf-gcc -g -c grbx.c
16216 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16217 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16220 The build process is identical for any other architecture, except that
16221 you must substitute the appropriate compiler and linker script for the
16222 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16226 @chapter Using @value{GDBN} with Different Languages
16229 Although programming languages generally have common aspects, they are
16230 rarely expressed in the same manner. For instance, in ANSI C,
16231 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16232 Modula-2, it is accomplished by @code{p^}. Values can also be
16233 represented (and displayed) differently. Hex numbers in C appear as
16234 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16236 @cindex working language
16237 Language-specific information is built into @value{GDBN} for some languages,
16238 allowing you to express operations like the above in your program's
16239 native language, and allowing @value{GDBN} to output values in a manner
16240 consistent with the syntax of your program's native language. The
16241 language you use to build expressions is called the @dfn{working
16245 * Setting:: Switching between source languages
16246 * Show:: Displaying the language
16247 * Checks:: Type and range checks
16248 * Supported Languages:: Supported languages
16249 * Unsupported Languages:: Unsupported languages
16253 @section Switching Between Source Languages
16255 There are two ways to control the working language---either have @value{GDBN}
16256 set it automatically, or select it manually yourself. You can use the
16257 @code{set language} command for either purpose. On startup, @value{GDBN}
16258 defaults to setting the language automatically. The working language is
16259 used to determine how expressions you type are interpreted, how values
16262 In addition to the working language, every source file that
16263 @value{GDBN} knows about has its own working language. For some object
16264 file formats, the compiler might indicate which language a particular
16265 source file is in. However, most of the time @value{GDBN} infers the
16266 language from the name of the file. The language of a source file
16267 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16268 show each frame appropriately for its own language. There is no way to
16269 set the language of a source file from within @value{GDBN}, but you can
16270 set the language associated with a filename extension. @xref{Show, ,
16271 Displaying the Language}.
16273 This is most commonly a problem when you use a program, such
16274 as @code{cfront} or @code{f2c}, that generates C but is written in
16275 another language. In that case, make the
16276 program use @code{#line} directives in its C output; that way
16277 @value{GDBN} will know the correct language of the source code of the original
16278 program, and will display that source code, not the generated C code.
16281 * Filenames:: Filename extensions and languages.
16282 * Manually:: Setting the working language manually
16283 * Automatically:: Having @value{GDBN} infer the source language
16287 @subsection List of Filename Extensions and Languages
16289 If a source file name ends in one of the following extensions, then
16290 @value{GDBN} infers that its language is the one indicated.
16308 C@t{++} source file
16314 Objective-C source file
16318 Fortran source file
16321 Modula-2 source file
16325 Assembler source file. This actually behaves almost like C, but
16326 @value{GDBN} does not skip over function prologues when stepping.
16329 In addition, you may set the language associated with a filename
16330 extension. @xref{Show, , Displaying the Language}.
16333 @subsection Setting the Working Language
16335 If you allow @value{GDBN} to set the language automatically,
16336 expressions are interpreted the same way in your debugging session and
16339 @kindex set language
16340 If you wish, you may set the language manually. To do this, issue the
16341 command @samp{set language @var{lang}}, where @var{lang} is the name of
16342 a language, such as
16343 @code{c} or @code{modula-2}.
16344 For a list of the supported languages, type @samp{set language}.
16346 Setting the language manually prevents @value{GDBN} from updating the working
16347 language automatically. This can lead to confusion if you try
16348 to debug a program when the working language is not the same as the
16349 source language, when an expression is acceptable to both
16350 languages---but means different things. For instance, if the current
16351 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16359 might not have the effect you intended. In C, this means to add
16360 @code{b} and @code{c} and place the result in @code{a}. The result
16361 printed would be the value of @code{a}. In Modula-2, this means to compare
16362 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16364 @node Automatically
16365 @subsection Having @value{GDBN} Infer the Source Language
16367 To have @value{GDBN} set the working language automatically, use
16368 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16369 then infers the working language. That is, when your program stops in a
16370 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16371 working language to the language recorded for the function in that
16372 frame. If the language for a frame is unknown (that is, if the function
16373 or block corresponding to the frame was defined in a source file that
16374 does not have a recognized extension), the current working language is
16375 not changed, and @value{GDBN} issues a warning.
16377 This may not seem necessary for most programs, which are written
16378 entirely in one source language. However, program modules and libraries
16379 written in one source language can be used by a main program written in
16380 a different source language. Using @samp{set language auto} in this
16381 case frees you from having to set the working language manually.
16384 @section Displaying the Language
16386 The following commands help you find out which language is the
16387 working language, and also what language source files were written in.
16390 @item show language
16391 @anchor{show language}
16392 @kindex show language
16393 Display the current working language. This is the
16394 language you can use with commands such as @code{print} to
16395 build and compute expressions that may involve variables in your program.
16398 @kindex info frame@r{, show the source language}
16399 Display the source language for this frame. This language becomes the
16400 working language if you use an identifier from this frame.
16401 @xref{Frame Info, ,Information about a Frame}, to identify the other
16402 information listed here.
16405 @kindex info source@r{, show the source language}
16406 Display the source language of this source file.
16407 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16408 information listed here.
16411 In unusual circumstances, you may have source files with extensions
16412 not in the standard list. You can then set the extension associated
16413 with a language explicitly:
16416 @item set extension-language @var{ext} @var{language}
16417 @kindex set extension-language
16418 Tell @value{GDBN} that source files with extension @var{ext} are to be
16419 assumed as written in the source language @var{language}.
16421 @item info extensions
16422 @kindex info extensions
16423 List all the filename extensions and the associated languages.
16427 @section Type and Range Checking
16429 Some languages are designed to guard you against making seemingly common
16430 errors through a series of compile- and run-time checks. These include
16431 checking the type of arguments to functions and operators and making
16432 sure mathematical overflows are caught at run time. Checks such as
16433 these help to ensure a program's correctness once it has been compiled
16434 by eliminating type mismatches and providing active checks for range
16435 errors when your program is running.
16437 By default @value{GDBN} checks for these errors according to the
16438 rules of the current source language. Although @value{GDBN} does not check
16439 the statements in your program, it can check expressions entered directly
16440 into @value{GDBN} for evaluation via the @code{print} command, for example.
16443 * Type Checking:: An overview of type checking
16444 * Range Checking:: An overview of range checking
16447 @cindex type checking
16448 @cindex checks, type
16449 @node Type Checking
16450 @subsection An Overview of Type Checking
16452 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16453 arguments to operators and functions have to be of the correct type,
16454 otherwise an error occurs. These checks prevent type mismatch
16455 errors from ever causing any run-time problems. For example,
16458 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16460 (@value{GDBP}) print obj.my_method (0)
16463 (@value{GDBP}) print obj.my_method (0x1234)
16464 Cannot resolve method klass::my_method to any overloaded instance
16467 The second example fails because in C@t{++} the integer constant
16468 @samp{0x1234} is not type-compatible with the pointer parameter type.
16470 For the expressions you use in @value{GDBN} commands, you can tell
16471 @value{GDBN} to not enforce strict type checking or
16472 to treat any mismatches as errors and abandon the expression;
16473 When type checking is disabled, @value{GDBN} successfully evaluates
16474 expressions like the second example above.
16476 Even if type checking is off, there may be other reasons
16477 related to type that prevent @value{GDBN} from evaluating an expression.
16478 For instance, @value{GDBN} does not know how to add an @code{int} and
16479 a @code{struct foo}. These particular type errors have nothing to do
16480 with the language in use and usually arise from expressions which make
16481 little sense to evaluate anyway.
16483 @value{GDBN} provides some additional commands for controlling type checking:
16485 @kindex set check type
16486 @kindex show check type
16488 @item set check type on
16489 @itemx set check type off
16490 Set strict type checking on or off. If any type mismatches occur in
16491 evaluating an expression while type checking is on, @value{GDBN} prints a
16492 message and aborts evaluation of the expression.
16494 @item show check type
16495 Show the current setting of type checking and whether @value{GDBN}
16496 is enforcing strict type checking rules.
16499 @cindex range checking
16500 @cindex checks, range
16501 @node Range Checking
16502 @subsection An Overview of Range Checking
16504 In some languages (such as Modula-2), it is an error to exceed the
16505 bounds of a type; this is enforced with run-time checks. Such range
16506 checking is meant to ensure program correctness by making sure
16507 computations do not overflow, or indices on an array element access do
16508 not exceed the bounds of the array.
16510 For expressions you use in @value{GDBN} commands, you can tell
16511 @value{GDBN} to treat range errors in one of three ways: ignore them,
16512 always treat them as errors and abandon the expression, or issue
16513 warnings but evaluate the expression anyway.
16515 A range error can result from numerical overflow, from exceeding an
16516 array index bound, or when you type a constant that is not a member
16517 of any type. Some languages, however, do not treat overflows as an
16518 error. In many implementations of C, mathematical overflow causes the
16519 result to ``wrap around'' to lower values---for example, if @var{m} is
16520 the largest integer value, and @var{s} is the smallest, then
16523 @var{m} + 1 @result{} @var{s}
16526 This, too, is specific to individual languages, and in some cases
16527 specific to individual compilers or machines. @xref{Supported Languages, ,
16528 Supported Languages}, for further details on specific languages.
16530 @value{GDBN} provides some additional commands for controlling the range checker:
16532 @kindex set check range
16533 @kindex show check range
16535 @item set check range auto
16536 Set range checking on or off based on the current working language.
16537 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16540 @item set check range on
16541 @itemx set check range off
16542 Set range checking on or off, overriding the default setting for the
16543 current working language. A warning is issued if the setting does not
16544 match the language default. If a range error occurs and range checking is on,
16545 then a message is printed and evaluation of the expression is aborted.
16547 @item set check range warn
16548 Output messages when the @value{GDBN} range checker detects a range error,
16549 but attempt to evaluate the expression anyway. Evaluating the
16550 expression may still be impossible for other reasons, such as accessing
16551 memory that the process does not own (a typical example from many Unix
16554 @item show check range
16555 Show the current setting of the range checker, and whether or not it is
16556 being set automatically by @value{GDBN}.
16559 @node Supported Languages
16560 @section Supported Languages
16562 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16563 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16564 @c This is false ...
16565 Some @value{GDBN} features may be used in expressions regardless of the
16566 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16567 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16568 ,Expressions}) can be used with the constructs of any supported
16571 The following sections detail to what degree each source language is
16572 supported by @value{GDBN}. These sections are not meant to be language
16573 tutorials or references, but serve only as a reference guide to what the
16574 @value{GDBN} expression parser accepts, and what input and output
16575 formats should look like for different languages. There are many good
16576 books written on each of these languages; please look to these for a
16577 language reference or tutorial.
16580 * C:: C and C@t{++}
16583 * Objective-C:: Objective-C
16584 * OpenCL C:: OpenCL C
16585 * Fortran:: Fortran
16588 * Modula-2:: Modula-2
16593 @subsection C and C@t{++}
16595 @cindex C and C@t{++}
16596 @cindex expressions in C or C@t{++}
16598 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16599 to both languages. Whenever this is the case, we discuss those languages
16603 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16604 @cindex @sc{gnu} C@t{++}
16605 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16606 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16607 effectively, you must compile your C@t{++} programs with a supported
16608 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16609 compiler (@code{aCC}).
16612 * C Operators:: C and C@t{++} operators
16613 * C Constants:: C and C@t{++} constants
16614 * C Plus Plus Expressions:: C@t{++} expressions
16615 * C Defaults:: Default settings for C and C@t{++}
16616 * C Checks:: C and C@t{++} type and range checks
16617 * Debugging C:: @value{GDBN} and C
16618 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16619 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16623 @subsubsection C and C@t{++} Operators
16625 @cindex C and C@t{++} operators
16627 Operators must be defined on values of specific types. For instance,
16628 @code{+} is defined on numbers, but not on structures. Operators are
16629 often defined on groups of types.
16631 For the purposes of C and C@t{++}, the following definitions hold:
16636 @emph{Integral types} include @code{int} with any of its storage-class
16637 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16640 @emph{Floating-point types} include @code{float}, @code{double}, and
16641 @code{long double} (if supported by the target platform).
16644 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16647 @emph{Scalar types} include all of the above.
16652 The following operators are supported. They are listed here
16653 in order of increasing precedence:
16657 The comma or sequencing operator. Expressions in a comma-separated list
16658 are evaluated from left to right, with the result of the entire
16659 expression being the last expression evaluated.
16662 Assignment. The value of an assignment expression is the value
16663 assigned. Defined on scalar types.
16666 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16667 and translated to @w{@code{@var{a} = @var{a op b}}}.
16668 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16669 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16670 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16673 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16674 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16675 should be of an integral type.
16678 Logical @sc{or}. Defined on integral types.
16681 Logical @sc{and}. Defined on integral types.
16684 Bitwise @sc{or}. Defined on integral types.
16687 Bitwise exclusive-@sc{or}. Defined on integral types.
16690 Bitwise @sc{and}. Defined on integral types.
16693 Equality and inequality. Defined on scalar types. The value of these
16694 expressions is 0 for false and non-zero for true.
16696 @item <@r{, }>@r{, }<=@r{, }>=
16697 Less than, greater than, less than or equal, greater than or equal.
16698 Defined on scalar types. The value of these expressions is 0 for false
16699 and non-zero for true.
16702 left shift, and right shift. Defined on integral types.
16705 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16708 Addition and subtraction. Defined on integral types, floating-point types and
16711 @item *@r{, }/@r{, }%
16712 Multiplication, division, and modulus. Multiplication and division are
16713 defined on integral and floating-point types. Modulus is defined on
16717 Increment and decrement. When appearing before a variable, the
16718 operation is performed before the variable is used in an expression;
16719 when appearing after it, the variable's value is used before the
16720 operation takes place.
16723 Pointer dereferencing. Defined on pointer types. Same precedence as
16727 Address operator. Defined on variables. Same precedence as @code{++}.
16729 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16730 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16731 to examine the address
16732 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16736 Negative. Defined on integral and floating-point types. Same
16737 precedence as @code{++}.
16740 Logical negation. Defined on integral types. Same precedence as
16744 Bitwise complement operator. Defined on integral types. Same precedence as
16749 Structure member, and pointer-to-structure member. For convenience,
16750 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16751 pointer based on the stored type information.
16752 Defined on @code{struct} and @code{union} data.
16755 Dereferences of pointers to members.
16758 Array indexing. @code{@var{a}[@var{i}]} is defined as
16759 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16762 Function parameter list. Same precedence as @code{->}.
16765 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16766 and @code{class} types.
16769 Doubled colons also represent the @value{GDBN} scope operator
16770 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16774 If an operator is redefined in the user code, @value{GDBN} usually
16775 attempts to invoke the redefined version instead of using the operator's
16776 predefined meaning.
16779 @subsubsection C and C@t{++} Constants
16781 @cindex C and C@t{++} constants
16783 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16788 Integer constants are a sequence of digits. Octal constants are
16789 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16790 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16791 @samp{l}, specifying that the constant should be treated as a
16795 Floating point constants are a sequence of digits, followed by a decimal
16796 point, followed by a sequence of digits, and optionally followed by an
16797 exponent. An exponent is of the form:
16798 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16799 sequence of digits. The @samp{+} is optional for positive exponents.
16800 A floating-point constant may also end with a letter @samp{f} or
16801 @samp{F}, specifying that the constant should be treated as being of
16802 the @code{float} (as opposed to the default @code{double}) type; or with
16803 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16807 Enumerated constants consist of enumerated identifiers, or their
16808 integral equivalents.
16811 Character constants are a single character surrounded by single quotes
16812 (@code{'}), or a number---the ordinal value of the corresponding character
16813 (usually its @sc{ascii} value). Within quotes, the single character may
16814 be represented by a letter or by @dfn{escape sequences}, which are of
16815 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16816 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16817 @samp{@var{x}} is a predefined special character---for example,
16818 @samp{\n} for newline.
16820 Wide character constants can be written by prefixing a character
16821 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16822 form of @samp{x}. The target wide character set is used when
16823 computing the value of this constant (@pxref{Character Sets}).
16826 String constants are a sequence of character constants surrounded by
16827 double quotes (@code{"}). Any valid character constant (as described
16828 above) may appear. Double quotes within the string must be preceded by
16829 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16832 Wide string constants can be written by prefixing a string constant
16833 with @samp{L}, as in C. The target wide character set is used when
16834 computing the value of this constant (@pxref{Character Sets}).
16837 Pointer constants are an integral value. You can also write pointers
16838 to constants using the C operator @samp{&}.
16841 Array constants are comma-separated lists surrounded by braces @samp{@{}
16842 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16843 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16844 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16847 @node C Plus Plus Expressions
16848 @subsubsection C@t{++} Expressions
16850 @cindex expressions in C@t{++}
16851 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16853 @cindex debugging C@t{++} programs
16854 @cindex C@t{++} compilers
16855 @cindex debug formats and C@t{++}
16856 @cindex @value{NGCC} and C@t{++}
16858 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16859 the proper compiler and the proper debug format. Currently,
16860 @value{GDBN} works best when debugging C@t{++} code that is compiled
16861 with the most recent version of @value{NGCC} possible. The DWARF
16862 debugging format is preferred; @value{NGCC} defaults to this on most
16863 popular platforms. Other compilers and/or debug formats are likely to
16864 work badly or not at all when using @value{GDBN} to debug C@t{++}
16865 code. @xref{Compilation}.
16870 @cindex member functions
16872 Member function calls are allowed; you can use expressions like
16875 count = aml->GetOriginal(x, y)
16878 @vindex this@r{, inside C@t{++} member functions}
16879 @cindex namespace in C@t{++}
16881 While a member function is active (in the selected stack frame), your
16882 expressions have the same namespace available as the member function;
16883 that is, @value{GDBN} allows implicit references to the class instance
16884 pointer @code{this} following the same rules as C@t{++}. @code{using}
16885 declarations in the current scope are also respected by @value{GDBN}.
16887 @cindex call overloaded functions
16888 @cindex overloaded functions, calling
16889 @cindex type conversions in C@t{++}
16891 You can call overloaded functions; @value{GDBN} resolves the function
16892 call to the right definition, with some restrictions. @value{GDBN} does not
16893 perform overload resolution involving user-defined type conversions,
16894 calls to constructors, or instantiations of templates that do not exist
16895 in the program. It also cannot handle ellipsis argument lists or
16898 It does perform integral conversions and promotions, floating-point
16899 promotions, arithmetic conversions, pointer conversions, conversions of
16900 class objects to base classes, and standard conversions such as those of
16901 functions or arrays to pointers; it requires an exact match on the
16902 number of function arguments.
16904 Overload resolution is always performed, unless you have specified
16905 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16906 ,@value{GDBN} Features for C@t{++}}.
16908 You must specify @code{set overload-resolution off} in order to use an
16909 explicit function signature to call an overloaded function, as in
16911 p 'foo(char,int)'('x', 13)
16914 The @value{GDBN} command-completion facility can simplify this;
16915 see @ref{Completion, ,Command Completion}.
16917 @cindex reference declarations
16919 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16920 references; you can use them in expressions just as you do in C@t{++}
16921 source---they are automatically dereferenced.
16923 In the parameter list shown when @value{GDBN} displays a frame, the values of
16924 reference variables are not displayed (unlike other variables); this
16925 avoids clutter, since references are often used for large structures.
16926 The @emph{address} of a reference variable is always shown, unless
16927 you have specified @samp{set print address off}.
16930 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16931 expressions can use it just as expressions in your program do. Since
16932 one scope may be defined in another, you can use @code{::} repeatedly if
16933 necessary, for example in an expression like
16934 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16935 resolving name scope by reference to source files, in both C and C@t{++}
16936 debugging (@pxref{Variables, ,Program Variables}).
16939 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16944 @subsubsection C and C@t{++} Defaults
16946 @cindex C and C@t{++} defaults
16948 If you allow @value{GDBN} to set range checking automatically, it
16949 defaults to @code{off} whenever the working language changes to
16950 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16951 selects the working language.
16953 If you allow @value{GDBN} to set the language automatically, it
16954 recognizes source files whose names end with @file{.c}, @file{.C}, or
16955 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16956 these files, it sets the working language to C or C@t{++}.
16957 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16958 for further details.
16961 @subsubsection C and C@t{++} Type and Range Checks
16963 @cindex C and C@t{++} checks
16965 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16966 checking is used. However, if you turn type checking off, @value{GDBN}
16967 will allow certain non-standard conversions, such as promoting integer
16968 constants to pointers.
16970 Range checking, if turned on, is done on mathematical operations. Array
16971 indices are not checked, since they are often used to index a pointer
16972 that is not itself an array.
16975 @subsubsection @value{GDBN} and C
16977 The @code{set print union} and @code{show print union} commands apply to
16978 the @code{union} type. When set to @samp{on}, any @code{union} that is
16979 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16980 appears as @samp{@{...@}}.
16982 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16983 with pointers and a memory allocation function. @xref{Expressions,
16986 @node Debugging C Plus Plus
16987 @subsubsection @value{GDBN} Features for C@t{++}
16989 @cindex commands for C@t{++}
16991 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16992 designed specifically for use with C@t{++}. Here is a summary:
16995 @cindex break in overloaded functions
16996 @item @r{breakpoint menus}
16997 When you want a breakpoint in a function whose name is overloaded,
16998 @value{GDBN} has the capability to display a menu of possible breakpoint
16999 locations to help you specify which function definition you want.
17000 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
17002 @cindex overloading in C@t{++}
17003 @item rbreak @var{regex}
17004 Setting breakpoints using regular expressions is helpful for setting
17005 breakpoints on overloaded functions that are not members of any special
17007 @xref{Set Breaks, ,Setting Breakpoints}.
17009 @cindex C@t{++} exception handling
17011 @itemx catch rethrow
17013 Debug C@t{++} exception handling using these commands. @xref{Set
17014 Catchpoints, , Setting Catchpoints}.
17016 @cindex inheritance
17017 @item ptype @var{typename}
17018 Print inheritance relationships as well as other information for type
17020 @xref{Symbols, ,Examining the Symbol Table}.
17022 @item info vtbl @var{expression}.
17023 The @code{info vtbl} command can be used to display the virtual
17024 method tables of the object computed by @var{expression}. This shows
17025 one entry per virtual table; there may be multiple virtual tables when
17026 multiple inheritance is in use.
17028 @cindex C@t{++} demangling
17029 @item demangle @var{name}
17030 Demangle @var{name}.
17031 @xref{Symbols}, for a more complete description of the @code{demangle} command.
17033 @cindex C@t{++} symbol display
17034 @item set print demangle
17035 @itemx show print demangle
17036 @itemx set print asm-demangle
17037 @itemx show print asm-demangle
17038 Control whether C@t{++} symbols display in their source form, both when
17039 displaying code as C@t{++} source and when displaying disassemblies.
17040 @xref{Print Settings, ,Print Settings}.
17042 @item set print object
17043 @itemx show print object
17044 Choose whether to print derived (actual) or declared types of objects.
17045 @xref{Print Settings, ,Print Settings}.
17047 @item set print vtbl
17048 @itemx show print vtbl
17049 Control the format for printing virtual function tables.
17050 @xref{Print Settings, ,Print Settings}.
17051 (The @code{vtbl} commands do not work on programs compiled with the HP
17052 ANSI C@t{++} compiler (@code{aCC}).)
17054 @kindex set overload-resolution
17055 @cindex overloaded functions, overload resolution
17056 @item set overload-resolution on
17057 Enable overload resolution for C@t{++} expression evaluation. The default
17058 is on. For overloaded functions, @value{GDBN} evaluates the arguments
17059 and searches for a function whose signature matches the argument types,
17060 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
17061 Expressions, ,C@t{++} Expressions}, for details).
17062 If it cannot find a match, it emits a message.
17064 @item set overload-resolution off
17065 Disable overload resolution for C@t{++} expression evaluation. For
17066 overloaded functions that are not class member functions, @value{GDBN}
17067 chooses the first function of the specified name that it finds in the
17068 symbol table, whether or not its arguments are of the correct type. For
17069 overloaded functions that are class member functions, @value{GDBN}
17070 searches for a function whose signature @emph{exactly} matches the
17073 @kindex show overload-resolution
17074 @item show overload-resolution
17075 Show the current setting of overload resolution.
17077 @item @r{Overloaded symbol names}
17078 You can specify a particular definition of an overloaded symbol, using
17079 the same notation that is used to declare such symbols in C@t{++}: type
17080 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
17081 also use the @value{GDBN} command-line word completion facilities to list the
17082 available choices, or to finish the type list for you.
17083 @xref{Completion,, Command Completion}, for details on how to do this.
17085 @item @r{Breakpoints in template functions}
17087 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
17088 template parameter lists when it encounters a symbol which includes a
17089 C@t{++} template. This permits setting breakpoints on families of template functions
17090 or functions whose parameters include template types.
17092 The @kbd{-qualified} flag may be used to override this behavior, causing
17093 @value{GDBN} to search for a specific function or type.
17095 The @value{GDBN} command-line word completion facility also understands
17096 template parameters and may be used to list available choices or finish
17097 template parameter lists for you. @xref{Completion,, Command Completion}, for
17098 details on how to do this.
17100 @item @r{Breakpoints in functions with ABI tags}
17102 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
17103 correspond to changes in the ABI of a type, function, or variable that
17104 would not otherwise be reflected in a mangled name. See
17105 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
17108 The ABI tags are visible in C@t{++} demangled names. For example, a
17109 function that returns a std::string:
17112 std::string function(int);
17116 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
17117 tag, and @value{GDBN} displays the symbol like this:
17120 function[abi:cxx11](int)
17123 You can set a breakpoint on such functions simply as if they had no
17127 (gdb) b function(int)
17128 Breakpoint 2 at 0x40060d: file main.cc, line 10.
17129 (gdb) info breakpoints
17130 Num Type Disp Enb Address What
17131 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
17135 On the rare occasion you need to disambiguate between different ABI
17136 tags, you can do so by simply including the ABI tag in the function
17140 (@value{GDBP}) b ambiguous[abi:other_tag](int)
17144 @node Decimal Floating Point
17145 @subsubsection Decimal Floating Point format
17146 @cindex decimal floating point format
17148 @value{GDBN} can examine, set and perform computations with numbers in
17149 decimal floating point format, which in the C language correspond to the
17150 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
17151 specified by the extension to support decimal floating-point arithmetic.
17153 There are two encodings in use, depending on the architecture: BID (Binary
17154 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
17155 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
17158 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
17159 to manipulate decimal floating point numbers, it is not possible to convert
17160 (using a cast, for example) integers wider than 32-bit to decimal float.
17162 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
17163 point computations, error checking in decimal float operations ignores
17164 underflow, overflow and divide by zero exceptions.
17166 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
17167 to inspect @code{_Decimal128} values stored in floating point registers.
17168 See @ref{PowerPC,,PowerPC} for more details.
17174 @value{GDBN} can be used to debug programs written in D and compiled with
17175 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
17176 specific feature --- dynamic arrays.
17181 @cindex Go (programming language)
17182 @value{GDBN} can be used to debug programs written in Go and compiled with
17183 @file{gccgo} or @file{6g} compilers.
17185 Here is a summary of the Go-specific features and restrictions:
17188 @cindex current Go package
17189 @item The current Go package
17190 The name of the current package does not need to be specified when
17191 specifying global variables and functions.
17193 For example, given the program:
17197 var myglob = "Shall we?"
17203 When stopped inside @code{main} either of these work:
17207 (gdb) p main.myglob
17210 @cindex builtin Go types
17211 @item Builtin Go types
17212 The @code{string} type is recognized by @value{GDBN} and is printed
17215 @cindex builtin Go functions
17216 @item Builtin Go functions
17217 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17218 function and handles it internally.
17220 @cindex restrictions on Go expressions
17221 @item Restrictions on Go expressions
17222 All Go operators are supported except @code{&^}.
17223 The Go @code{_} ``blank identifier'' is not supported.
17224 Automatic dereferencing of pointers is not supported.
17228 @subsection Objective-C
17230 @cindex Objective-C
17231 This section provides information about some commands and command
17232 options that are useful for debugging Objective-C code. See also
17233 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17234 few more commands specific to Objective-C support.
17237 * Method Names in Commands::
17238 * The Print Command with Objective-C::
17241 @node Method Names in Commands
17242 @subsubsection Method Names in Commands
17244 The following commands have been extended to accept Objective-C method
17245 names as line specifications:
17247 @kindex clear@r{, and Objective-C}
17248 @kindex break@r{, and Objective-C}
17249 @kindex info line@r{, and Objective-C}
17250 @kindex jump@r{, and Objective-C}
17251 @kindex list@r{, and Objective-C}
17255 @item @code{info line}
17260 A fully qualified Objective-C method name is specified as
17263 -[@var{Class} @var{methodName}]
17266 where the minus sign is used to indicate an instance method and a
17267 plus sign (not shown) is used to indicate a class method. The class
17268 name @var{Class} and method name @var{methodName} are enclosed in
17269 brackets, similar to the way messages are specified in Objective-C
17270 source code. For example, to set a breakpoint at the @code{create}
17271 instance method of class @code{Fruit} in the program currently being
17275 break -[Fruit create]
17278 To list ten program lines around the @code{initialize} class method,
17282 list +[NSText initialize]
17285 In the current version of @value{GDBN}, the plus or minus sign is
17286 required. In future versions of @value{GDBN}, the plus or minus
17287 sign will be optional, but you can use it to narrow the search. It
17288 is also possible to specify just a method name:
17294 You must specify the complete method name, including any colons. If
17295 your program's source files contain more than one @code{create} method,
17296 you'll be presented with a numbered list of classes that implement that
17297 method. Indicate your choice by number, or type @samp{0} to exit if
17300 As another example, to clear a breakpoint established at the
17301 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17304 clear -[NSWindow makeKeyAndOrderFront:]
17307 @node The Print Command with Objective-C
17308 @subsubsection The Print Command With Objective-C
17309 @cindex Objective-C, print objects
17310 @kindex print-object
17311 @kindex po @r{(@code{print-object})}
17313 The print command has also been extended to accept methods. For example:
17316 print -[@var{object} hash]
17319 @cindex print an Objective-C object description
17320 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17322 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17323 and print the result. Also, an additional command has been added,
17324 @code{print-object} or @code{po} for short, which is meant to print
17325 the description of an object. However, this command may only work
17326 with certain Objective-C libraries that have a particular hook
17327 function, @code{_NSPrintForDebugger}, defined.
17330 @subsection OpenCL C
17333 This section provides information about @value{GDBN}s OpenCL C support.
17336 * OpenCL C Datatypes::
17337 * OpenCL C Expressions::
17338 * OpenCL C Operators::
17341 @node OpenCL C Datatypes
17342 @subsubsection OpenCL C Datatypes
17344 @cindex OpenCL C Datatypes
17345 @value{GDBN} supports the builtin scalar and vector datatypes specified
17346 by OpenCL 1.1. In addition the half- and double-precision floating point
17347 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17348 extensions are also known to @value{GDBN}.
17350 @node OpenCL C Expressions
17351 @subsubsection OpenCL C Expressions
17353 @cindex OpenCL C Expressions
17354 @value{GDBN} supports accesses to vector components including the access as
17355 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17356 supported by @value{GDBN} can be used as well.
17358 @node OpenCL C Operators
17359 @subsubsection OpenCL C Operators
17361 @cindex OpenCL C Operators
17362 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17366 @subsection Fortran
17367 @cindex Fortran-specific support in @value{GDBN}
17369 @value{GDBN} can be used to debug programs written in Fortran. Note, that not
17370 all Fortran language features are available yet.
17372 @cindex trailing underscore, in Fortran symbols
17373 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17374 among them) append an underscore to the names of variables and
17375 functions. When you debug programs compiled by those compilers, you
17376 will need to refer to variables and functions with a trailing
17379 @cindex Fortran Defaults
17380 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17381 default uses case-insensitive matching for Fortran symbols. You can
17382 change that with the @samp{set case-insensitive} command, see
17383 @ref{Symbols}, for the details.
17386 * Fortran Types:: Fortran builtin types
17387 * Fortran Operators:: Fortran operators and expressions
17388 * Fortran Intrinsics:: Fortran intrinsic functions
17389 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17392 @node Fortran Types
17393 @subsubsection Fortran Types
17395 @cindex Fortran Types
17397 In Fortran the primitive data-types have an associated @code{KIND} type
17398 parameter, written as @samp{@var{type}*@var{kindparam}},
17399 @samp{@var{type}*@var{kindparam}}, or in the @value{GDBN}-only dialect
17400 @samp{@var{type}_@var{kindparam}}. A concrete example would be
17401 @samp{@code{Real*4}}, @samp{@code{Real(kind=4)}}, and @samp{@code{Real_4}}.
17402 The kind of a type can be retrieved by using the intrinsic function
17403 @code{KIND}, see @ref{Fortran Intrinsics}.
17405 Generally, the actual implementation of the @code{KIND} type parameter is
17406 compiler specific. In @value{GDBN} the kind parameter is implemented in
17407 accordance with its use in the @sc{gnu} @command{gfortran} compiler. Here, the
17408 kind parameter for a given @var{type} specifies its size in memory --- a
17409 Fortran @code{Integer*4} or @code{Integer(kind=4)} would be an integer type
17410 occupying 4 bytes of memory. An exception to this rule is the @code{Complex}
17411 type for which the kind of the type does not specify its entire size, but
17412 the size of each of the two @code{Real}'s it is composed of. A
17413 @code{Complex*4} would thus consist of two @code{Real*4}s and occupy 8 bytes
17416 For every type there is also a default kind associated with it, e.g.@
17417 @code{Integer} in @value{GDBN} will internally be an @code{Integer*4} (see the
17418 table below for default types). The default types are the same as in @sc{gnu}
17419 compilers but note, that the @sc{gnu} default types can actually be changed by
17420 compiler flags such as @option{-fdefault-integer-8} and
17421 @option{-fdefault-real-8}.
17423 Not every kind parameter is valid for every type and in @value{GDBN} the
17424 following type kinds are available.
17428 @code{Integer*1}, @code{Integer*2}, @code{Integer*4}, @code{Integer*8}, and
17429 @code{Integer} = @code{Integer*4}.
17432 @code{Logical*1}, @code{Logical*2}, @code{Logical*4}, @code{Logical*8}, and
17433 @code{Logical} = @code{Logical*4}.
17436 @code{Real*4}, @code{Real*8}, @code{Real*16}, and @code{Real} = @code{Real*4}.
17439 @code{Complex*4}, @code{Complex*8}, @code{Complex*16}, and @code{Complex} =
17444 @node Fortran Operators
17445 @subsubsection Fortran Operators and Expressions
17447 @cindex Fortran operators and expressions
17449 Operators must be defined on values of specific types. For instance,
17450 @code{+} is defined on numbers, but not on characters or other non-
17451 arithmetic types. Operators are often defined on groups of types.
17455 The exponentiation operator. It raises the first operand to the power
17459 The range operator. Normally used in the form of array(low:high) to
17460 represent a section of array.
17463 The access component operator. Normally used to access elements in derived
17464 types. Also suitable for unions. As unions aren't part of regular Fortran,
17465 this can only happen when accessing a register that uses a gdbarch-defined
17468 The scope operator. Normally used to access variables in modules or
17469 to set breakpoints on subroutines nested in modules or in other
17470 subroutines (internal subroutines).
17473 @node Fortran Intrinsics
17474 @subsubsection Fortran Intrinsics
17476 @cindex Fortran Intrinsics
17478 Fortran provides a large set of intrinsic procedures. @value{GDBN} implements
17479 an incomplete subset of those procedures and their overloads. Some of these
17480 procedures take an optional @code{KIND} parameter, see @ref{Fortran Types}.
17484 Computes the absolute value of its argument @var{a}. Currently not supported
17485 for @code{Complex} arguments.
17487 @item ALLOCATE(@var{array})
17488 Returns whether @var{array} is allocated or not.
17490 @item ASSOCIATED(@var{pointer} [, @var{target}])
17491 Returns the association status of the pointer @var{pointer} or, if @var{target}
17492 is present, whether @var{pointer} is associated with the target @var{target}.
17494 @item CEILING(@var{a} [, @var{kind}])
17495 Computes the least integer greater than or equal to @var{a}. The optional
17496 parameter @var{kind} specifies the kind of the return type
17497 @code{Integer(@var{kind})}.
17499 @item CMPLX(@var{x} [, @var{y} [, @var{kind}]])
17500 Returns a complex number where @var{x} is converted to the real component. If
17501 @var{y} is present it is converted to the imaginary component. If @var{y} is
17502 not present then the imaginary component is set to @code{0.0} except if @var{x}
17503 itself is of @code{Complex} type. The optional parameter @var{kind} specifies
17504 the kind of the return type @code{Complex(@var{kind})}.
17506 @item FLOOR(@var{a} [, @var{kind}])
17507 Computes the greatest integer less than or equal to @var{a}. The optional
17508 parameter @var{kind} specifies the kind of the return type
17509 @code{Integer(@var{kind})}.
17511 @item KIND(@var{a})
17512 Returns the kind value of the argument @var{a}, see @ref{Fortran Types}.
17514 @item LBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17515 Returns the lower bounds of an @var{array}, or a single lower bound along the
17516 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17517 the kind of the return type @code{Integer(@var{kind})}.
17520 Returns the address of @var{x} as an @code{Integer}.
17522 @item MOD(@var{a}, @var{p})
17523 Computes the remainder of the division of @var{a} by @var{p}.
17525 @item MODULO(@var{a}, @var{p})
17526 Computes the @var{a} modulo @var{p}.
17528 @item RANK(@var{a})
17529 Returns the rank of a scalar or array (scalars have rank @code{0}).
17531 @item SHAPE(@var{a})
17532 Returns the shape of a scalar or array (scalars have shape @samp{()}).
17534 @item SIZE(@var{array}[, @var{dim} [, @var{kind}]])
17535 Returns the extent of @var{array} along a specified dimension @var{dim}, or the
17536 total number of elements in @var{array} if @var{dim} is absent. The optional
17537 parameter @var{kind} specifies the kind of the return type
17538 @code{Integer(@var{kind})}.
17540 @item UBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17541 Returns the upper bounds of an @var{array}, or a single upper bound along the
17542 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17543 the kind of the return type @code{Integer(@var{kind})}.
17547 @node Special Fortran Commands
17548 @subsubsection Special Fortran Commands
17550 @cindex Special Fortran commands
17552 @value{GDBN} has some commands to support Fortran-specific features,
17553 such as displaying common blocks.
17556 @cindex @code{COMMON} blocks, Fortran
17557 @kindex info common
17558 @item info common @r{[}@var{common-name}@r{]}
17559 This command prints the values contained in the Fortran @code{COMMON}
17560 block whose name is @var{common-name}. With no argument, the names of
17561 all @code{COMMON} blocks visible at the current program location are
17563 @cindex arrays slices (Fortran)
17564 @kindex set fortran repack-array-slices
17565 @kindex show fortran repack-array-slices
17566 @item set fortran repack-array-slices [on|off]
17567 @item show fortran repack-array-slices
17568 When taking a slice from an array, a Fortran compiler can choose to
17569 either produce an array descriptor that describes the slice in place,
17570 or it may repack the slice, copying the elements of the slice into a
17571 new region of memory.
17573 When this setting is on, then @value{GDBN} will also repack array
17574 slices in some situations. When this setting is off, then
17575 @value{GDBN} will create array descriptors for slices that reference
17576 the original data in place.
17578 @value{GDBN} will never repack an array slice if the data for the
17579 slice is contiguous within the original array.
17581 @value{GDBN} will always repack string slices if the data for the
17582 slice is non-contiguous within the original string as @value{GDBN}
17583 does not support printing non-contiguous strings.
17585 The default for this setting is @code{off}.
17591 @cindex Pascal support in @value{GDBN}, limitations
17592 Debugging Pascal programs which use sets, subranges, file variables, or
17593 nested functions does not currently work. @value{GDBN} does not support
17594 entering expressions, printing values, or similar features using Pascal
17597 The Pascal-specific command @code{set print pascal_static-members}
17598 controls whether static members of Pascal objects are displayed.
17599 @xref{Print Settings, pascal_static-members}.
17604 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17605 Programming Language}. Type- and value-printing, and expression
17606 parsing, are reasonably complete. However, there are a few
17607 peculiarities and holes to be aware of.
17611 Linespecs (@pxref{Location Specifications}) are never relative to the
17612 current crate. Instead, they act as if there were a global namespace
17613 of crates, somewhat similar to the way @code{extern crate} behaves.
17615 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17616 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17617 to set a breakpoint in a function named @samp{f} in a crate named
17620 As a consequence of this approach, linespecs also cannot refer to
17621 items using @samp{self::} or @samp{super::}.
17624 Because @value{GDBN} implements Rust name-lookup semantics in
17625 expressions, it will sometimes prepend the current crate to a name.
17626 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17627 @samp{K}, then @code{print ::x::y} will try to find the symbol
17630 However, since it is useful to be able to refer to other crates when
17631 debugging, @value{GDBN} provides the @code{extern} extension to
17632 circumvent this. To use the extension, just put @code{extern} before
17633 a path expression to refer to the otherwise unavailable ``global''
17636 In the above example, if you wanted to refer to the symbol @samp{y} in
17637 the crate @samp{x}, you would use @code{print extern x::y}.
17640 The Rust expression evaluator does not support ``statement-like''
17641 expressions such as @code{if} or @code{match}, or lambda expressions.
17644 Tuple expressions are not implemented.
17647 The Rust expression evaluator does not currently implement the
17648 @code{Drop} trait. Objects that may be created by the evaluator will
17649 never be destroyed.
17652 @value{GDBN} does not implement type inference for generics. In order
17653 to call generic functions or otherwise refer to generic items, you
17654 will have to specify the type parameters manually.
17657 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17658 cases this does not cause any problems. However, in an expression
17659 context, completing a generic function name will give syntactically
17660 invalid results. This happens because Rust requires the @samp{::}
17661 operator between the function name and its generic arguments. For
17662 example, @value{GDBN} might provide a completion like
17663 @code{crate::f<u32>}, where the parser would require
17664 @code{crate::f::<u32>}.
17667 As of this writing, the Rust compiler (version 1.8) has a few holes in
17668 the debugging information it generates. These holes prevent certain
17669 features from being implemented by @value{GDBN}:
17673 Method calls cannot be made via traits.
17676 Operator overloading is not implemented.
17679 When debugging in a monomorphized function, you cannot use the generic
17683 The type @code{Self} is not available.
17686 @code{use} statements are not available, so some names may not be
17687 available in the crate.
17692 @subsection Modula-2
17694 @cindex Modula-2, @value{GDBN} support
17696 The extensions made to @value{GDBN} to support Modula-2 only support
17697 output from the @sc{gnu} Modula-2 compiler (which is currently being
17698 developed). Other Modula-2 compilers are not currently supported, and
17699 attempting to debug executables produced by them is most likely
17700 to give an error as @value{GDBN} reads in the executable's symbol
17703 @cindex expressions in Modula-2
17705 * M2 Operators:: Built-in operators
17706 * Built-In Func/Proc:: Built-in functions and procedures
17707 * M2 Constants:: Modula-2 constants
17708 * M2 Types:: Modula-2 types
17709 * M2 Defaults:: Default settings for Modula-2
17710 * Deviations:: Deviations from standard Modula-2
17711 * M2 Checks:: Modula-2 type and range checks
17712 * M2 Scope:: The scope operators @code{::} and @code{.}
17713 * GDB/M2:: @value{GDBN} and Modula-2
17717 @subsubsection Operators
17718 @cindex Modula-2 operators
17720 Operators must be defined on values of specific types. For instance,
17721 @code{+} is defined on numbers, but not on structures. Operators are
17722 often defined on groups of types. For the purposes of Modula-2, the
17723 following definitions hold:
17728 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17732 @emph{Character types} consist of @code{CHAR} and its subranges.
17735 @emph{Floating-point types} consist of @code{REAL}.
17738 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17742 @emph{Scalar types} consist of all of the above.
17745 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17748 @emph{Boolean types} consist of @code{BOOLEAN}.
17752 The following operators are supported, and appear in order of
17753 increasing precedence:
17757 Function argument or array index separator.
17760 Assignment. The value of @var{var} @code{:=} @var{value} is
17764 Less than, greater than on integral, floating-point, or enumerated
17768 Less than or equal to, greater than or equal to
17769 on integral, floating-point and enumerated types, or set inclusion on
17770 set types. Same precedence as @code{<}.
17772 @item =@r{, }<>@r{, }#
17773 Equality and two ways of expressing inequality, valid on scalar types.
17774 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17775 available for inequality, since @code{#} conflicts with the script
17779 Set membership. Defined on set types and the types of their members.
17780 Same precedence as @code{<}.
17783 Boolean disjunction. Defined on boolean types.
17786 Boolean conjunction. Defined on boolean types.
17789 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17792 Addition and subtraction on integral and floating-point types, or union
17793 and difference on set types.
17796 Multiplication on integral and floating-point types, or set intersection
17800 Division on floating-point types, or symmetric set difference on set
17801 types. Same precedence as @code{*}.
17804 Integer division and remainder. Defined on integral types. Same
17805 precedence as @code{*}.
17808 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17811 Pointer dereferencing. Defined on pointer types.
17814 Boolean negation. Defined on boolean types. Same precedence as
17818 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17819 precedence as @code{^}.
17822 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17825 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17829 @value{GDBN} and Modula-2 scope operators.
17833 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17834 treats the use of the operator @code{IN}, or the use of operators
17835 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17836 @code{<=}, and @code{>=} on sets as an error.
17840 @node Built-In Func/Proc
17841 @subsubsection Built-in Functions and Procedures
17842 @cindex Modula-2 built-ins
17844 Modula-2 also makes available several built-in procedures and functions.
17845 In describing these, the following metavariables are used:
17850 represents an @code{ARRAY} variable.
17853 represents a @code{CHAR} constant or variable.
17856 represents a variable or constant of integral type.
17859 represents an identifier that belongs to a set. Generally used in the
17860 same function with the metavariable @var{s}. The type of @var{s} should
17861 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17864 represents a variable or constant of integral or floating-point type.
17867 represents a variable or constant of floating-point type.
17873 represents a variable.
17876 represents a variable or constant of one of many types. See the
17877 explanation of the function for details.
17880 All Modula-2 built-in procedures also return a result, described below.
17884 Returns the absolute value of @var{n}.
17887 If @var{c} is a lower case letter, it returns its upper case
17888 equivalent, otherwise it returns its argument.
17891 Returns the character whose ordinal value is @var{i}.
17894 Decrements the value in the variable @var{v} by one. Returns the new value.
17896 @item DEC(@var{v},@var{i})
17897 Decrements the value in the variable @var{v} by @var{i}. Returns the
17900 @item EXCL(@var{m},@var{s})
17901 Removes the element @var{m} from the set @var{s}. Returns the new
17904 @item FLOAT(@var{i})
17905 Returns the floating point equivalent of the integer @var{i}.
17907 @item HIGH(@var{a})
17908 Returns the index of the last member of @var{a}.
17911 Increments the value in the variable @var{v} by one. Returns the new value.
17913 @item INC(@var{v},@var{i})
17914 Increments the value in the variable @var{v} by @var{i}. Returns the
17917 @item INCL(@var{m},@var{s})
17918 Adds the element @var{m} to the set @var{s} if it is not already
17919 there. Returns the new set.
17922 Returns the maximum value of the type @var{t}.
17925 Returns the minimum value of the type @var{t}.
17928 Returns boolean TRUE if @var{i} is an odd number.
17931 Returns the ordinal value of its argument. For example, the ordinal
17932 value of a character is its @sc{ascii} value (on machines supporting
17933 the @sc{ascii} character set). The argument @var{x} must be of an
17934 ordered type, which include integral, character and enumerated types.
17936 @item SIZE(@var{x})
17937 Returns the size of its argument. The argument @var{x} can be a
17938 variable or a type.
17940 @item TRUNC(@var{r})
17941 Returns the integral part of @var{r}.
17943 @item TSIZE(@var{x})
17944 Returns the size of its argument. The argument @var{x} can be a
17945 variable or a type.
17947 @item VAL(@var{t},@var{i})
17948 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17952 @emph{Warning:} Sets and their operations are not yet supported, so
17953 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17957 @cindex Modula-2 constants
17959 @subsubsection Constants
17961 @value{GDBN} allows you to express the constants of Modula-2 in the following
17967 Integer constants are simply a sequence of digits. When used in an
17968 expression, a constant is interpreted to be type-compatible with the
17969 rest of the expression. Hexadecimal integers are specified by a
17970 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17973 Floating point constants appear as a sequence of digits, followed by a
17974 decimal point and another sequence of digits. An optional exponent can
17975 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17976 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17977 digits of the floating point constant must be valid decimal (base 10)
17981 Character constants consist of a single character enclosed by a pair of
17982 like quotes, either single (@code{'}) or double (@code{"}). They may
17983 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17984 followed by a @samp{C}.
17987 String constants consist of a sequence of characters enclosed by a
17988 pair of like quotes, either single (@code{'}) or double (@code{"}).
17989 Escape sequences in the style of C are also allowed. @xref{C
17990 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17994 Enumerated constants consist of an enumerated identifier.
17997 Boolean constants consist of the identifiers @code{TRUE} and
18001 Pointer constants consist of integral values only.
18004 Set constants are not yet supported.
18008 @subsubsection Modula-2 Types
18009 @cindex Modula-2 types
18011 Currently @value{GDBN} can print the following data types in Modula-2
18012 syntax: array types, record types, set types, pointer types, procedure
18013 types, enumerated types, subrange types and base types. You can also
18014 print the contents of variables declared using these type.
18015 This section gives a number of simple source code examples together with
18016 sample @value{GDBN} sessions.
18018 The first example contains the following section of code:
18027 and you can request @value{GDBN} to interrogate the type and value of
18028 @code{r} and @code{s}.
18031 (@value{GDBP}) print s
18033 (@value{GDBP}) ptype s
18035 (@value{GDBP}) print r
18037 (@value{GDBP}) ptype r
18042 Likewise if your source code declares @code{s} as:
18046 s: SET ['A'..'Z'] ;
18050 then you may query the type of @code{s} by:
18053 (@value{GDBP}) ptype s
18054 type = SET ['A'..'Z']
18058 Note that at present you cannot interactively manipulate set
18059 expressions using the debugger.
18061 The following example shows how you might declare an array in Modula-2
18062 and how you can interact with @value{GDBN} to print its type and contents:
18066 s: ARRAY [-10..10] OF CHAR ;
18070 (@value{GDBP}) ptype s
18071 ARRAY [-10..10] OF CHAR
18074 Note that the array handling is not yet complete and although the type
18075 is printed correctly, expression handling still assumes that all
18076 arrays have a lower bound of zero and not @code{-10} as in the example
18079 Here are some more type related Modula-2 examples:
18083 colour = (blue, red, yellow, green) ;
18084 t = [blue..yellow] ;
18092 The @value{GDBN} interaction shows how you can query the data type
18093 and value of a variable.
18096 (@value{GDBP}) print s
18098 (@value{GDBP}) ptype t
18099 type = [blue..yellow]
18103 In this example a Modula-2 array is declared and its contents
18104 displayed. Observe that the contents are written in the same way as
18105 their @code{C} counterparts.
18109 s: ARRAY [1..5] OF CARDINAL ;
18115 (@value{GDBP}) print s
18116 $1 = @{1, 0, 0, 0, 0@}
18117 (@value{GDBP}) ptype s
18118 type = ARRAY [1..5] OF CARDINAL
18121 The Modula-2 language interface to @value{GDBN} also understands
18122 pointer types as shown in this example:
18126 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
18133 and you can request that @value{GDBN} describes the type of @code{s}.
18136 (@value{GDBP}) ptype s
18137 type = POINTER TO ARRAY [1..5] OF CARDINAL
18140 @value{GDBN} handles compound types as we can see in this example.
18141 Here we combine array types, record types, pointer types and subrange
18152 myarray = ARRAY myrange OF CARDINAL ;
18153 myrange = [-2..2] ;
18155 s: POINTER TO ARRAY myrange OF foo ;
18159 and you can ask @value{GDBN} to describe the type of @code{s} as shown
18163 (@value{GDBP}) ptype s
18164 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
18167 f3 : ARRAY [-2..2] OF CARDINAL;
18172 @subsubsection Modula-2 Defaults
18173 @cindex Modula-2 defaults
18175 If type and range checking are set automatically by @value{GDBN}, they
18176 both default to @code{on} whenever the working language changes to
18177 Modula-2. This happens regardless of whether you or @value{GDBN}
18178 selected the working language.
18180 If you allow @value{GDBN} to set the language automatically, then entering
18181 code compiled from a file whose name ends with @file{.mod} sets the
18182 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
18183 Infer the Source Language}, for further details.
18186 @subsubsection Deviations from Standard Modula-2
18187 @cindex Modula-2, deviations from
18189 A few changes have been made to make Modula-2 programs easier to debug.
18190 This is done primarily via loosening its type strictness:
18194 Unlike in standard Modula-2, pointer constants can be formed by
18195 integers. This allows you to modify pointer variables during
18196 debugging. (In standard Modula-2, the actual address contained in a
18197 pointer variable is hidden from you; it can only be modified
18198 through direct assignment to another pointer variable or expression that
18199 returned a pointer.)
18202 C escape sequences can be used in strings and characters to represent
18203 non-printable characters. @value{GDBN} prints out strings with these
18204 escape sequences embedded. Single non-printable characters are
18205 printed using the @samp{CHR(@var{nnn})} format.
18208 The assignment operator (@code{:=}) returns the value of its right-hand
18212 All built-in procedures both modify @emph{and} return their argument.
18216 @subsubsection Modula-2 Type and Range Checks
18217 @cindex Modula-2 checks
18220 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
18223 @c FIXME remove warning when type/range checks added
18225 @value{GDBN} considers two Modula-2 variables type equivalent if:
18229 They are of types that have been declared equivalent via a @code{TYPE
18230 @var{t1} = @var{t2}} statement
18233 They have been declared on the same line. (Note: This is true of the
18234 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
18237 As long as type checking is enabled, any attempt to combine variables
18238 whose types are not equivalent is an error.
18240 Range checking is done on all mathematical operations, assignment, array
18241 index bounds, and all built-in functions and procedures.
18244 @subsubsection The Scope Operators @code{::} and @code{.}
18246 @cindex @code{.}, Modula-2 scope operator
18247 @cindex colon, doubled as scope operator
18249 @vindex colon-colon@r{, in Modula-2}
18250 @c Info cannot handle :: but TeX can.
18253 @vindex ::@r{, in Modula-2}
18256 There are a few subtle differences between the Modula-2 scope operator
18257 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
18262 @var{module} . @var{id}
18263 @var{scope} :: @var{id}
18267 where @var{scope} is the name of a module or a procedure,
18268 @var{module} the name of a module, and @var{id} is any declared
18269 identifier within your program, except another module.
18271 Using the @code{::} operator makes @value{GDBN} search the scope
18272 specified by @var{scope} for the identifier @var{id}. If it is not
18273 found in the specified scope, then @value{GDBN} searches all scopes
18274 enclosing the one specified by @var{scope}.
18276 Using the @code{.} operator makes @value{GDBN} search the current scope for
18277 the identifier specified by @var{id} that was imported from the
18278 definition module specified by @var{module}. With this operator, it is
18279 an error if the identifier @var{id} was not imported from definition
18280 module @var{module}, or if @var{id} is not an identifier in
18284 @subsubsection @value{GDBN} and Modula-2
18286 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
18287 Five subcommands of @code{set print} and @code{show print} apply
18288 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
18289 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
18290 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
18291 analogue in Modula-2.
18293 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
18294 with any language, is not useful with Modula-2. Its
18295 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
18296 created in Modula-2 as they can in C or C@t{++}. However, because an
18297 address can be specified by an integral constant, the construct
18298 @samp{@{@var{type}@}@var{adrexp}} is still useful.
18300 @cindex @code{#} in Modula-2
18301 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
18302 interpreted as the beginning of a comment. Use @code{<>} instead.
18308 The extensions made to @value{GDBN} for Ada only support
18309 output from the @sc{gnu} Ada (GNAT) compiler.
18310 Other Ada compilers are not currently supported, and
18311 attempting to debug executables produced by them is most likely
18315 @cindex expressions in Ada
18317 * Ada Mode Intro:: General remarks on the Ada syntax
18318 and semantics supported by Ada mode
18320 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18321 * Additions to Ada:: Extensions of the Ada expression syntax.
18322 * Overloading support for Ada:: Support for expressions involving overloaded
18324 * Stopping Before Main Program:: Debugging the program during elaboration.
18325 * Ada Exceptions:: Ada Exceptions
18326 * Ada Tasks:: Listing and setting breakpoints in tasks.
18327 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18328 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18330 * Ada Source Character Set:: Character set of Ada source files.
18331 * Ada Glitches:: Known peculiarities of Ada mode.
18334 @node Ada Mode Intro
18335 @subsubsection Introduction
18336 @cindex Ada mode, general
18338 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18339 syntax, with some extensions.
18340 The philosophy behind the design of this subset is
18344 That @value{GDBN} should provide basic literals and access to operations for
18345 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18346 leaving more sophisticated computations to subprograms written into the
18347 program (which therefore may be called from @value{GDBN}).
18350 That type safety and strict adherence to Ada language restrictions
18351 are not particularly important to the @value{GDBN} user.
18354 That brevity is important to the @value{GDBN} user.
18357 Thus, for brevity, the debugger acts as if all names declared in
18358 user-written packages are directly visible, even if they are not visible
18359 according to Ada rules, thus making it unnecessary to fully qualify most
18360 names with their packages, regardless of context. Where this causes
18361 ambiguity, @value{GDBN} asks the user's intent.
18363 The debugger will start in Ada mode if it detects an Ada main program.
18364 As for other languages, it will enter Ada mode when stopped in a program that
18365 was translated from an Ada source file.
18367 While in Ada mode, you may use `@t{--}' for comments. This is useful
18368 mostly for documenting command files. The standard @value{GDBN} comment
18369 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18370 middle (to allow based literals).
18372 @node Omissions from Ada
18373 @subsubsection Omissions from Ada
18374 @cindex Ada, omissions from
18376 Here are the notable omissions from the subset:
18380 Only a subset of the attributes are supported:
18384 @t{'First}, @t{'Last}, and @t{'Length}
18385 on array objects (not on types and subtypes).
18388 @t{'Min} and @t{'Max}.
18391 @t{'Pos} and @t{'Val}.
18397 @t{'Range} on array objects (not subtypes), but only as the right
18398 operand of the membership (@code{in}) operator.
18401 @t{'Access}, @t{'Unchecked_Access}, and
18402 @t{'Unrestricted_Access} (a GNAT extension).
18409 The names in @code{Characters.Latin_1} are not available.
18412 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18413 equality of representations. They will generally work correctly
18414 for strings and arrays whose elements have integer or enumeration types.
18415 They may not work correctly for arrays whose element
18416 types have user-defined equality, for arrays of real values
18417 (in particular, IEEE-conformant floating point, because of negative
18418 zeroes and NaNs), and for arrays whose elements contain unused bits with
18419 indeterminate values.
18422 The other component-by-component array operations (@code{and}, @code{or},
18423 @code{xor}, @code{not}, and relational tests other than equality)
18424 are not implemented.
18427 @cindex array aggregates (Ada)
18428 @cindex record aggregates (Ada)
18429 @cindex aggregates (Ada)
18430 There is limited support for array and record aggregates. They are
18431 permitted only on the right sides of assignments, as in these examples:
18434 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18435 (@value{GDBP}) set An_Array := (1, others => 0)
18436 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18437 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18438 (@value{GDBP}) set A_Record := (1, "Peter", True);
18439 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18443 discriminant's value by assigning an aggregate has an
18444 undefined effect if that discriminant is used within the record.
18445 However, you can first modify discriminants by directly assigning to
18446 them (which normally would not be allowed in Ada), and then performing an
18447 aggregate assignment. For example, given a variable @code{A_Rec}
18448 declared to have a type such as:
18451 type Rec (Len : Small_Integer := 0) is record
18453 Vals : IntArray (1 .. Len);
18457 you can assign a value with a different size of @code{Vals} with two
18461 (@value{GDBP}) set A_Rec.Len := 4
18462 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18465 As this example also illustrates, @value{GDBN} is very loose about the usual
18466 rules concerning aggregates. You may leave out some of the
18467 components of an array or record aggregate (such as the @code{Len}
18468 component in the assignment to @code{A_Rec} above); they will retain their
18469 original values upon assignment. You may freely use dynamic values as
18470 indices in component associations. You may even use overlapping or
18471 redundant component associations, although which component values are
18472 assigned in such cases is not defined.
18475 Calls to dispatching subprograms are not implemented.
18478 The overloading algorithm is much more limited (i.e., less selective)
18479 than that of real Ada. It makes only limited use of the context in
18480 which a subexpression appears to resolve its meaning, and it is much
18481 looser in its rules for allowing type matches. As a result, some
18482 function calls will be ambiguous, and the user will be asked to choose
18483 the proper resolution.
18486 The @code{new} operator is not implemented.
18489 Entry calls are not implemented.
18492 Aside from printing, arithmetic operations on the native VAX floating-point
18493 formats are not supported.
18496 It is not possible to slice a packed array.
18499 The names @code{True} and @code{False}, when not part of a qualified name,
18500 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18502 Should your program
18503 redefine these names in a package or procedure (at best a dubious practice),
18504 you will have to use fully qualified names to access their new definitions.
18507 Based real literals are not implemented.
18510 @node Additions to Ada
18511 @subsubsection Additions to Ada
18512 @cindex Ada, deviations from
18514 As it does for other languages, @value{GDBN} makes certain generic
18515 extensions to Ada (@pxref{Expressions}):
18519 If the expression @var{E} is a variable residing in memory (typically
18520 a local variable or array element) and @var{N} is a positive integer,
18521 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18522 @var{N}-1 adjacent variables following it in memory as an array. In
18523 Ada, this operator is generally not necessary, since its prime use is
18524 in displaying parts of an array, and slicing will usually do this in
18525 Ada. However, there are occasional uses when debugging programs in
18526 which certain debugging information has been optimized away.
18529 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18530 appears in function or file @var{B}.'' When @var{B} is a file name,
18531 you must typically surround it in single quotes.
18534 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18535 @var{type} that appears at address @var{addr}.''
18538 A name starting with @samp{$} is a convenience variable
18539 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18542 In addition, @value{GDBN} provides a few other shortcuts and outright
18543 additions specific to Ada:
18547 The assignment statement is allowed as an expression, returning
18548 its right-hand operand as its value. Thus, you may enter
18551 (@value{GDBP}) set x := y + 3
18552 (@value{GDBP}) print A(tmp := y + 1)
18556 The semicolon is allowed as an ``operator,'' returning as its value
18557 the value of its right-hand operand.
18558 This allows, for example,
18559 complex conditional breaks:
18562 (@value{GDBP}) break f
18563 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18567 An extension to based literals can be used to specify the exact byte
18568 contents of a floating-point literal. After the base, you can use
18569 from zero to two @samp{l} characters, followed by an @samp{f}. The
18570 number of @samp{l} characters controls the width of the resulting real
18571 constant: zero means @code{Float} is used, one means
18572 @code{Long_Float}, and two means @code{Long_Long_Float}.
18575 (@value{GDBP}) print 16f#41b80000#
18580 Rather than use catenation and symbolic character names to introduce special
18581 characters into strings, one may instead use a special bracket notation,
18582 which is also used to print strings. A sequence of characters of the form
18583 @samp{["@var{XX}"]} within a string or character literal denotes the
18584 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18585 sequence of characters @samp{["""]} also denotes a single quotation mark
18586 in strings. For example,
18588 "One line.["0a"]Next line.["0a"]"
18591 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18595 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18596 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18600 (@value{GDBP}) print 'max(x, y)
18604 When printing arrays, @value{GDBN} uses positional notation when the
18605 array has a lower bound of 1, and uses a modified named notation otherwise.
18606 For example, a one-dimensional array of three integers with a lower bound
18607 of 3 might print as
18614 That is, in contrast to valid Ada, only the first component has a @code{=>}
18618 You may abbreviate attributes in expressions with any unique,
18619 multi-character subsequence of
18620 their names (an exact match gets preference).
18621 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18622 in place of @t{a'length}.
18625 @cindex quoting Ada internal identifiers
18626 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18627 to lower case. The GNAT compiler uses upper-case characters for
18628 some of its internal identifiers, which are normally of no interest to users.
18629 For the rare occasions when you actually have to look at them,
18630 enclose them in angle brackets to avoid the lower-case mapping.
18633 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18637 Printing an object of class-wide type or dereferencing an
18638 access-to-class-wide value will display all the components of the object's
18639 specific type (as indicated by its run-time tag). Likewise, component
18640 selection on such a value will operate on the specific type of the
18645 @node Overloading support for Ada
18646 @subsubsection Overloading support for Ada
18647 @cindex overloading, Ada
18649 The debugger supports limited overloading. Given a subprogram call in which
18650 the function symbol has multiple definitions, it will use the number of
18651 actual parameters and some information about their types to attempt to narrow
18652 the set of definitions. It also makes very limited use of context, preferring
18653 procedures to functions in the context of the @code{call} command, and
18654 functions to procedures elsewhere.
18656 If, after narrowing, the set of matching definitions still contains more than
18657 one definition, @value{GDBN} will display a menu to query which one it should
18661 (@value{GDBP}) print f(1)
18662 Multiple matches for f
18664 [1] foo.f (integer) return boolean at foo.adb:23
18665 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18669 In this case, just select one menu entry either to cancel expression evaluation
18670 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18671 instance (type the corresponding number and press @key{RET}).
18673 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18678 @kindex set ada print-signatures
18679 @item set ada print-signatures
18680 Control whether parameter types and return types are displayed in overloads
18681 selection menus. It is @code{on} by default.
18682 @xref{Overloading support for Ada}.
18684 @kindex show ada print-signatures
18685 @item show ada print-signatures
18686 Show the current setting for displaying parameter types and return types in
18687 overloads selection menu.
18688 @xref{Overloading support for Ada}.
18692 @node Stopping Before Main Program
18693 @subsubsection Stopping at the Very Beginning
18695 @cindex breakpointing Ada elaboration code
18696 It is sometimes necessary to debug the program during elaboration, and
18697 before reaching the main procedure.
18698 As defined in the Ada Reference
18699 Manual, the elaboration code is invoked from a procedure called
18700 @code{adainit}. To run your program up to the beginning of
18701 elaboration, simply use the following two commands:
18702 @code{tbreak adainit} and @code{run}.
18704 @node Ada Exceptions
18705 @subsubsection Ada Exceptions
18707 A command is provided to list all Ada exceptions:
18710 @kindex info exceptions
18711 @item info exceptions
18712 @itemx info exceptions @var{regexp}
18713 The @code{info exceptions} command allows you to list all Ada exceptions
18714 defined within the program being debugged, as well as their addresses.
18715 With a regular expression, @var{regexp}, as argument, only those exceptions
18716 whose names match @var{regexp} are listed.
18719 Below is a small example, showing how the command can be used, first
18720 without argument, and next with a regular expression passed as an
18724 (@value{GDBP}) info exceptions
18725 All defined Ada exceptions:
18726 constraint_error: 0x613da0
18727 program_error: 0x613d20
18728 storage_error: 0x613ce0
18729 tasking_error: 0x613ca0
18730 const.aint_global_e: 0x613b00
18731 (@value{GDBP}) info exceptions const.aint
18732 All Ada exceptions matching regular expression "const.aint":
18733 constraint_error: 0x613da0
18734 const.aint_global_e: 0x613b00
18737 It is also possible to ask @value{GDBN} to stop your program's execution
18738 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18741 @subsubsection Extensions for Ada Tasks
18742 @cindex Ada, tasking
18744 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18745 @value{GDBN} provides the following task-related commands:
18750 This command shows a list of current Ada tasks, as in the following example:
18757 (@value{GDBP}) info tasks
18758 ID TID P-ID Pri State Name
18759 1 8088000 0 15 Child Activation Wait main_task
18760 2 80a4000 1 15 Accept Statement b
18761 3 809a800 1 15 Child Activation Wait a
18762 * 4 80ae800 3 15 Runnable c
18767 In this listing, the asterisk before the last task indicates it to be the
18768 task currently being inspected.
18772 Represents @value{GDBN}'s internal task number.
18778 The parent's task ID (@value{GDBN}'s internal task number).
18781 The base priority of the task.
18784 Current state of the task.
18788 The task has been created but has not been activated. It cannot be
18792 The task is not blocked for any reason known to Ada. (It may be waiting
18793 for a mutex, though.) It is conceptually "executing" in normal mode.
18796 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18797 that were waiting on terminate alternatives have been awakened and have
18798 terminated themselves.
18800 @item Child Activation Wait
18801 The task is waiting for created tasks to complete activation.
18803 @item Accept Statement
18804 The task is waiting on an accept or selective wait statement.
18806 @item Waiting on entry call
18807 The task is waiting on an entry call.
18809 @item Async Select Wait
18810 The task is waiting to start the abortable part of an asynchronous
18814 The task is waiting on a select statement with only a delay
18817 @item Child Termination Wait
18818 The task is sleeping having completed a master within itself, and is
18819 waiting for the tasks dependent on that master to become terminated or
18820 waiting on a terminate Phase.
18822 @item Wait Child in Term Alt
18823 The task is sleeping waiting for tasks on terminate alternatives to
18824 finish terminating.
18826 @item Accepting RV with @var{taskno}
18827 The task is accepting a rendez-vous with the task @var{taskno}.
18831 Name of the task in the program.
18835 @kindex info task @var{taskno}
18836 @item info task @var{taskno}
18837 This command shows detailed informations on the specified task, as in
18838 the following example:
18843 (@value{GDBP}) info tasks
18844 ID TID P-ID Pri State Name
18845 1 8077880 0 15 Child Activation Wait main_task
18846 * 2 807c468 1 15 Runnable task_1
18847 (@value{GDBP}) info task 2
18848 Ada Task: 0x807c468
18852 Parent: 1 ("main_task")
18858 @kindex task@r{ (Ada)}
18859 @cindex current Ada task ID
18860 This command prints the ID and name of the current task.
18866 (@value{GDBP}) info tasks
18867 ID TID P-ID Pri State Name
18868 1 8077870 0 15 Child Activation Wait main_task
18869 * 2 807c458 1 15 Runnable some_task
18870 (@value{GDBP}) task
18871 [Current task is 2 "some_task"]
18874 @item task @var{taskno}
18875 @cindex Ada task switching
18876 This command is like the @code{thread @var{thread-id}}
18877 command (@pxref{Threads}). It switches the context of debugging
18878 from the current task to the given task.
18884 (@value{GDBP}) info tasks
18885 ID TID P-ID Pri State Name
18886 1 8077870 0 15 Child Activation Wait main_task
18887 * 2 807c458 1 15 Runnable some_task
18888 (@value{GDBP}) task 1
18889 [Switching to task 1 "main_task"]
18890 #0 0x8067726 in pthread_cond_wait ()
18892 #0 0x8067726 in pthread_cond_wait ()
18893 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18894 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18895 #3 0x806153e in system.tasking.stages.activate_tasks ()
18896 #4 0x804aacc in un () at un.adb:5
18899 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
18900 The @code{task apply} command is the Ada tasking analogue of
18901 @code{thread apply} (@pxref{Threads}). It allows you to apply the
18902 named @var{command} to one or more tasks. Specify the tasks that you
18903 want affected using a list of task IDs, or specify @code{all} to apply
18906 The @var{flag} arguments control what output to produce and how to
18907 handle errors raised when applying @var{command} to a task.
18908 @var{flag} must start with a @code{-} directly followed by one letter
18909 in @code{qcs}. If several flags are provided, they must be given
18910 individually, such as @code{-c -q}.
18912 By default, @value{GDBN} displays some task information before the
18913 output produced by @var{command}, and an error raised during the
18914 execution of a @var{command} will abort @code{task apply}. The
18915 following flags can be used to fine-tune this behavior:
18919 The flag @code{-c}, which stands for @samp{continue}, causes any
18920 errors in @var{command} to be displayed, and the execution of
18921 @code{task apply} then continues.
18923 The flag @code{-s}, which stands for @samp{silent}, causes any errors
18924 or empty output produced by a @var{command} to be silently ignored.
18925 That is, the execution continues, but the task information and errors
18928 The flag @code{-q} (@samp{quiet}) disables printing the task
18932 Flags @code{-c} and @code{-s} cannot be used together.
18934 @item break @var{locspec} task @var{taskno}
18935 @itemx break @var{locspec} task @var{taskno} if @dots{}
18936 @cindex breakpoints and tasks, in Ada
18937 @cindex task breakpoints, in Ada
18938 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18939 These commands are like the @code{break @dots{} thread @dots{}}
18940 command (@pxref{Thread Stops}). @xref{Location Specifications}, for
18941 the various forms of @var{locspec}.
18943 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18944 to specify that you only want @value{GDBN} to stop the program when a
18945 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18946 numeric task identifiers assigned by @value{GDBN}, shown in the first
18947 column of the @samp{info tasks} display.
18949 If you do not specify @samp{task @var{taskno}} when you set a
18950 breakpoint, the breakpoint applies to @emph{all} tasks of your
18953 You can use the @code{task} qualifier on conditional breakpoints as
18954 well; in this case, place @samp{task @var{taskno}} before the
18955 breakpoint condition (before the @code{if}).
18963 (@value{GDBP}) info tasks
18964 ID TID P-ID Pri State Name
18965 1 140022020 0 15 Child Activation Wait main_task
18966 2 140045060 1 15 Accept/Select Wait t2
18967 3 140044840 1 15 Runnable t1
18968 * 4 140056040 1 15 Runnable t3
18969 (@value{GDBP}) b 15 task 2
18970 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18971 (@value{GDBP}) cont
18976 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18978 (@value{GDBP}) info tasks
18979 ID TID P-ID Pri State Name
18980 1 140022020 0 15 Child Activation Wait main_task
18981 * 2 140045060 1 15 Runnable t2
18982 3 140044840 1 15 Runnable t1
18983 4 140056040 1 15 Delay Sleep t3
18987 @node Ada Tasks and Core Files
18988 @subsubsection Tasking Support when Debugging Core Files
18989 @cindex Ada tasking and core file debugging
18991 When inspecting a core file, as opposed to debugging a live program,
18992 tasking support may be limited or even unavailable, depending on
18993 the platform being used.
18994 For instance, on x86-linux, the list of tasks is available, but task
18995 switching is not supported.
18997 On certain platforms, the debugger needs to perform some
18998 memory writes in order to provide Ada tasking support. When inspecting
18999 a core file, this means that the core file must be opened with read-write
19000 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
19001 Under these circumstances, you should make a backup copy of the core
19002 file before inspecting it with @value{GDBN}.
19004 @node Ravenscar Profile
19005 @subsubsection Tasking Support when using the Ravenscar Profile
19006 @cindex Ravenscar Profile
19008 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
19009 specifically designed for systems with safety-critical real-time
19013 @kindex set ravenscar task-switching on
19014 @cindex task switching with program using Ravenscar Profile
19015 @item set ravenscar task-switching on
19016 Allows task switching when debugging a program that uses the Ravenscar
19017 Profile. This is the default.
19019 @kindex set ravenscar task-switching off
19020 @item set ravenscar task-switching off
19021 Turn off task switching when debugging a program that uses the Ravenscar
19022 Profile. This is mostly intended to disable the code that adds support
19023 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
19024 the Ravenscar runtime is preventing @value{GDBN} from working properly.
19025 To be effective, this command should be run before the program is started.
19027 @kindex show ravenscar task-switching
19028 @item show ravenscar task-switching
19029 Show whether it is possible to switch from task to task in a program
19030 using the Ravenscar Profile.
19034 @cindex Ravenscar thread
19035 When Ravenscar task-switching is enabled, Ravenscar tasks are
19036 announced by @value{GDBN} as if they were threads:
19040 [New Ravenscar Thread 0x2b8f0]
19043 Both Ravenscar tasks and the underlying CPU threads will show up in
19044 the output of @code{info threads}:
19049 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
19050 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
19051 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
19052 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
19053 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
19054 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
19057 One known limitation of the Ravenscar support in @value{GDBN} is that
19058 it isn't currently possible to single-step through the runtime
19059 initialization sequence. If you need to debug this code, you should
19060 use @code{set ravenscar task-switching off}.
19062 @node Ada Source Character Set
19063 @subsubsection Ada Source Character Set
19064 @cindex Ada, source character set
19066 The GNAT compiler supports a number of character sets for source
19067 files. @xref{Character Set Control, , Character Set Control,
19068 gnat_ugn}. @value{GDBN} includes support for this as well.
19071 @item set ada source-charset @var{charset}
19072 @kindex set ada source-charset
19073 Set the source character set for Ada. The character set must be
19074 supported by GNAT. Because this setting affects the decoding of
19075 symbols coming from the debug information in your program, the setting
19076 should be set as early as possible. The default is @code{ISO-8859-1},
19077 because that is also GNAT's default.
19079 @item show ada source-charset
19080 @kindex show ada source-charset
19081 Show the current source character set for Ada.
19085 @subsubsection Known Peculiarities of Ada Mode
19086 @cindex Ada, problems
19088 Besides the omissions listed previously (@pxref{Omissions from Ada}),
19089 we know of several problems with and limitations of Ada mode in
19091 some of which will be fixed with planned future releases of the debugger
19092 and the GNU Ada compiler.
19096 Static constants that the compiler chooses not to materialize as objects in
19097 storage are invisible to the debugger.
19100 Named parameter associations in function argument lists are ignored (the
19101 argument lists are treated as positional).
19104 Many useful library packages are currently invisible to the debugger.
19107 Fixed-point arithmetic, conversions, input, and output is carried out using
19108 floating-point arithmetic, and may give results that only approximate those on
19112 The GNAT compiler never generates the prefix @code{Standard} for any of
19113 the standard symbols defined by the Ada language. @value{GDBN} knows about
19114 this: it will strip the prefix from names when you use it, and will never
19115 look for a name you have so qualified among local symbols, nor match against
19116 symbols in other packages or subprograms. If you have
19117 defined entities anywhere in your program other than parameters and
19118 local variables whose simple names match names in @code{Standard},
19119 GNAT's lack of qualification here can cause confusion. When this happens,
19120 you can usually resolve the confusion
19121 by qualifying the problematic names with package
19122 @code{Standard} explicitly.
19125 Older versions of the compiler sometimes generate erroneous debugging
19126 information, resulting in the debugger incorrectly printing the value
19127 of affected entities. In some cases, the debugger is able to work
19128 around an issue automatically. In other cases, the debugger is able
19129 to work around the issue, but the work-around has to be specifically
19132 @kindex set ada trust-PAD-over-XVS
19133 @kindex show ada trust-PAD-over-XVS
19136 @item set ada trust-PAD-over-XVS on
19137 Configure GDB to strictly follow the GNAT encoding when computing the
19138 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
19139 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
19140 a complete description of the encoding used by the GNAT compiler).
19141 This is the default.
19143 @item set ada trust-PAD-over-XVS off
19144 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
19145 sometimes prints the wrong value for certain entities, changing @code{ada
19146 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
19147 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
19148 @code{off}, but this incurs a slight performance penalty, so it is
19149 recommended to leave this setting to @code{on} unless necessary.
19153 @cindex GNAT descriptive types
19154 @cindex GNAT encoding
19155 Internally, the debugger also relies on the compiler following a number
19156 of conventions known as the @samp{GNAT Encoding}, all documented in
19157 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
19158 how the debugging information should be generated for certain types.
19159 In particular, this convention makes use of @dfn{descriptive types},
19160 which are artificial types generated purely to help the debugger.
19162 These encodings were defined at a time when the debugging information
19163 format used was not powerful enough to describe some of the more complex
19164 types available in Ada. Since DWARF allows us to express nearly all
19165 Ada features, the long-term goal is to slowly replace these descriptive
19166 types by their pure DWARF equivalent. To facilitate that transition,
19167 a new maintenance option is available to force the debugger to ignore
19168 those descriptive types. It allows the user to quickly evaluate how
19169 well @value{GDBN} works without them.
19173 @kindex maint ada set ignore-descriptive-types
19174 @item maintenance ada set ignore-descriptive-types [on|off]
19175 Control whether the debugger should ignore descriptive types.
19176 The default is not to ignore descriptives types (@code{off}).
19178 @kindex maint ada show ignore-descriptive-types
19179 @item maintenance ada show ignore-descriptive-types
19180 Show if descriptive types are ignored by @value{GDBN}.
19184 @node Unsupported Languages
19185 @section Unsupported Languages
19187 @cindex unsupported languages
19188 @cindex minimal language
19189 In addition to the other fully-supported programming languages,
19190 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
19191 It does not represent a real programming language, but provides a set
19192 of capabilities close to what the C or assembly languages provide.
19193 This should allow most simple operations to be performed while debugging
19194 an application that uses a language currently not supported by @value{GDBN}.
19196 If the language is set to @code{auto}, @value{GDBN} will automatically
19197 select this language if the current frame corresponds to an unsupported
19201 @chapter Examining the Symbol Table
19203 The commands described in this chapter allow you to inquire about the
19204 symbols (names of variables, functions and types) defined in your
19205 program. This information is inherent in the text of your program and
19206 does not change as your program executes. @value{GDBN} finds it in your
19207 program's symbol table, in the file indicated when you started @value{GDBN}
19208 (@pxref{File Options, ,Choosing Files}), or by one of the
19209 file-management commands (@pxref{Files, ,Commands to Specify Files}).
19211 @cindex symbol names
19212 @cindex names of symbols
19213 @cindex quoting names
19214 @anchor{quoting names}
19215 Occasionally, you may need to refer to symbols that contain unusual
19216 characters, which @value{GDBN} ordinarily treats as word delimiters. The
19217 most frequent case is in referring to static variables in other
19218 source files (@pxref{Variables,,Program Variables}). File names
19219 are recorded in object files as debugging symbols, but @value{GDBN} would
19220 ordinarily parse a typical file name, like @file{foo.c}, as the three words
19221 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
19222 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
19229 looks up the value of @code{x} in the scope of the file @file{foo.c}.
19232 @cindex case-insensitive symbol names
19233 @cindex case sensitivity in symbol names
19234 @kindex set case-sensitive
19235 @item set case-sensitive on
19236 @itemx set case-sensitive off
19237 @itemx set case-sensitive auto
19238 Normally, when @value{GDBN} looks up symbols, it matches their names
19239 with case sensitivity determined by the current source language.
19240 Occasionally, you may wish to control that. The command @code{set
19241 case-sensitive} lets you do that by specifying @code{on} for
19242 case-sensitive matches or @code{off} for case-insensitive ones. If
19243 you specify @code{auto}, case sensitivity is reset to the default
19244 suitable for the source language. The default is case-sensitive
19245 matches for all languages except for Fortran, for which the default is
19246 case-insensitive matches.
19248 @kindex show case-sensitive
19249 @item show case-sensitive
19250 This command shows the current setting of case sensitivity for symbols
19253 @kindex set print type methods
19254 @item set print type methods
19255 @itemx set print type methods on
19256 @itemx set print type methods off
19257 Normally, when @value{GDBN} prints a class, it displays any methods
19258 declared in that class. You can control this behavior either by
19259 passing the appropriate flag to @code{ptype}, or using @command{set
19260 print type methods}. Specifying @code{on} will cause @value{GDBN} to
19261 display the methods; this is the default. Specifying @code{off} will
19262 cause @value{GDBN} to omit the methods.
19264 @kindex show print type methods
19265 @item show print type methods
19266 This command shows the current setting of method display when printing
19269 @kindex set print type nested-type-limit
19270 @item set print type nested-type-limit @var{limit}
19271 @itemx set print type nested-type-limit unlimited
19272 Set the limit of displayed nested types that the type printer will
19273 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
19274 nested definitions. By default, the type printer will not show any nested
19275 types defined in classes.
19277 @kindex show print type nested-type-limit
19278 @item show print type nested-type-limit
19279 This command shows the current display limit of nested types when
19282 @kindex set print type typedefs
19283 @item set print type typedefs
19284 @itemx set print type typedefs on
19285 @itemx set print type typedefs off
19287 Normally, when @value{GDBN} prints a class, it displays any typedefs
19288 defined in that class. You can control this behavior either by
19289 passing the appropriate flag to @code{ptype}, or using @command{set
19290 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19291 display the typedef definitions; this is the default. Specifying
19292 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19293 Note that this controls whether the typedef definition itself is
19294 printed, not whether typedef names are substituted when printing other
19297 @kindex show print type typedefs
19298 @item show print type typedefs
19299 This command shows the current setting of typedef display when
19302 @kindex set print type hex
19303 @item set print type hex
19304 @itemx set print type hex on
19305 @itemx set print type hex off
19307 When @value{GDBN} prints sizes and offsets of struct members, it can use
19308 either the decimal or hexadecimal notation. You can select one or the
19309 other either by passing the appropriate flag to @code{ptype}, or by using
19310 the @command{set print type hex} command.
19312 @kindex show print type hex
19313 @item show print type hex
19314 This command shows whether the sizes and offsets of struct members are
19315 printed in decimal or hexadecimal notation.
19317 @kindex info address
19318 @cindex address of a symbol
19319 @item info address @var{symbol}
19320 Describe where the data for @var{symbol} is stored. For a register
19321 variable, this says which register it is kept in. For a non-register
19322 local variable, this prints the stack-frame offset at which the variable
19325 Note the contrast with @samp{print &@var{symbol}}, which does not work
19326 at all for a register variable, and for a stack local variable prints
19327 the exact address of the current instantiation of the variable.
19329 @kindex info symbol
19330 @cindex symbol from address
19331 @cindex closest symbol and offset for an address
19332 @item info symbol @var{addr}
19333 Print the name of a symbol which is stored at the address @var{addr}.
19334 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19335 nearest symbol and an offset from it:
19338 (@value{GDBP}) info symbol 0x54320
19339 _initialize_vx + 396 in section .text
19343 This is the opposite of the @code{info address} command. You can use
19344 it to find out the name of a variable or a function given its address.
19346 For dynamically linked executables, the name of executable or shared
19347 library containing the symbol is also printed:
19350 (@value{GDBP}) info symbol 0x400225
19351 _start + 5 in section .text of /tmp/a.out
19352 (@value{GDBP}) info symbol 0x2aaaac2811cf
19353 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19358 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19359 Demangle @var{name}.
19360 If @var{language} is provided it is the name of the language to demangle
19361 @var{name} in. Otherwise @var{name} is demangled in the current language.
19363 The @samp{--} option specifies the end of options,
19364 and is useful when @var{name} begins with a dash.
19366 The parameter @code{demangle-style} specifies how to interpret the kind
19367 of mangling used. @xref{Print Settings}.
19370 @item whatis[/@var{flags}] [@var{arg}]
19371 Print the data type of @var{arg}, which can be either an expression
19372 or a name of a data type. With no argument, print the data type of
19373 @code{$}, the last value in the value history.
19375 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19376 is not actually evaluated, and any side-effecting operations (such as
19377 assignments or function calls) inside it do not take place.
19379 If @var{arg} is a variable or an expression, @code{whatis} prints its
19380 literal type as it is used in the source code. If the type was
19381 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19382 the data type underlying the @code{typedef}. If the type of the
19383 variable or the expression is a compound data type, such as
19384 @code{struct} or @code{class}, @code{whatis} never prints their
19385 fields or methods. It just prints the @code{struct}/@code{class}
19386 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19387 such a compound data type, use @code{ptype}.
19389 If @var{arg} is a type name that was defined using @code{typedef},
19390 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19391 Unrolling means that @code{whatis} will show the underlying type used
19392 in the @code{typedef} declaration of @var{arg}. However, if that
19393 underlying type is also a @code{typedef}, @code{whatis} will not
19396 For C code, the type names may also have the form @samp{class
19397 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19398 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19400 @var{flags} can be used to modify how the type is displayed.
19401 Available flags are:
19405 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19406 parameters and typedefs defined in a class when printing the class'
19407 members. The @code{/r} flag disables this.
19410 Do not print methods defined in the class.
19413 Print methods defined in the class. This is the default, but the flag
19414 exists in case you change the default with @command{set print type methods}.
19417 Do not print typedefs defined in the class. Note that this controls
19418 whether the typedef definition itself is printed, not whether typedef
19419 names are substituted when printing other types.
19422 Print typedefs defined in the class. This is the default, but the flag
19423 exists in case you change the default with @command{set print type typedefs}.
19426 Print the offsets and sizes of fields in a struct, similar to what the
19427 @command{pahole} tool does. This option implies the @code{/tm} flags.
19430 Use hexadecimal notation when printing offsets and sizes of fields in a
19434 Use decimal notation when printing offsets and sizes of fields in a
19437 For example, given the following declarations:
19473 Issuing a @kbd{ptype /o struct tuv} command would print:
19476 (@value{GDBP}) ptype /o struct tuv
19477 /* offset | size */ type = struct tuv @{
19478 /* 0 | 4 */ int a1;
19479 /* XXX 4-byte hole */
19480 /* 8 | 8 */ char *a2;
19481 /* 16 | 4 */ int a3;
19483 /* total size (bytes): 24 */
19487 Notice the format of the first column of comments. There, you can
19488 find two parts separated by the @samp{|} character: the @emph{offset},
19489 which indicates where the field is located inside the struct, in
19490 bytes, and the @emph{size} of the field. Another interesting line is
19491 the marker of a @emph{hole} in the struct, indicating that it may be
19492 possible to pack the struct and make it use less space by reorganizing
19495 It is also possible to print offsets inside an union:
19498 (@value{GDBP}) ptype /o union qwe
19499 /* offset | size */ type = union qwe @{
19500 /* 24 */ struct tuv @{
19501 /* 0 | 4 */ int a1;
19502 /* XXX 4-byte hole */
19503 /* 8 | 8 */ char *a2;
19504 /* 16 | 4 */ int a3;
19506 /* total size (bytes): 24 */
19508 /* 40 */ struct xyz @{
19509 /* 0 | 4 */ int f1;
19510 /* 4 | 1 */ char f2;
19511 /* XXX 3-byte hole */
19512 /* 8 | 8 */ void *f3;
19513 /* 16 | 24 */ struct tuv @{
19514 /* 16 | 4 */ int a1;
19515 /* XXX 4-byte hole */
19516 /* 24 | 8 */ char *a2;
19517 /* 32 | 4 */ int a3;
19519 /* total size (bytes): 24 */
19522 /* total size (bytes): 40 */
19525 /* total size (bytes): 40 */
19529 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19530 same space (because we are dealing with an union), the offset is not
19531 printed for them. However, you can still examine the offset of each
19532 of these structures' fields.
19534 Another useful scenario is printing the offsets of a struct containing
19538 (@value{GDBP}) ptype /o struct tyu
19539 /* offset | size */ type = struct tyu @{
19540 /* 0:31 | 4 */ int a1 : 1;
19541 /* 0:28 | 4 */ int a2 : 3;
19542 /* 0: 5 | 4 */ int a3 : 23;
19543 /* 3: 3 | 1 */ signed char a4 : 2;
19544 /* XXX 3-bit hole */
19545 /* XXX 4-byte hole */
19546 /* 8 | 8 */ int64_t a5;
19547 /* 16: 0 | 4 */ int a6 : 5;
19548 /* 16: 5 | 8 */ int64_t a7 : 3;
19549 /* XXX 7-byte padding */
19551 /* total size (bytes): 24 */
19555 Note how the offset information is now extended to also include the
19556 first bit of the bitfield.
19560 @item ptype[/@var{flags}] [@var{arg}]
19561 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19562 detailed description of the type, instead of just the name of the type.
19563 @xref{Expressions, ,Expressions}.
19565 Contrary to @code{whatis}, @code{ptype} always unrolls any
19566 @code{typedef}s in its argument declaration, whether the argument is
19567 a variable, expression, or a data type. This means that @code{ptype}
19568 of a variable or an expression will not print literally its type as
19569 present in the source code---use @code{whatis} for that. @code{typedef}s at
19570 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19571 fields, methods and inner @code{class typedef}s of @code{struct}s,
19572 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19574 For example, for this variable declaration:
19577 typedef double real_t;
19578 struct complex @{ real_t real; double imag; @};
19579 typedef struct complex complex_t;
19581 real_t *real_pointer_var;
19585 the two commands give this output:
19589 (@value{GDBP}) whatis var
19591 (@value{GDBP}) ptype var
19592 type = struct complex @{
19596 (@value{GDBP}) whatis complex_t
19597 type = struct complex
19598 (@value{GDBP}) whatis struct complex
19599 type = struct complex
19600 (@value{GDBP}) ptype struct complex
19601 type = struct complex @{
19605 (@value{GDBP}) whatis real_pointer_var
19607 (@value{GDBP}) ptype real_pointer_var
19613 As with @code{whatis}, using @code{ptype} without an argument refers to
19614 the type of @code{$}, the last value in the value history.
19616 @cindex incomplete type
19617 Sometimes, programs use opaque data types or incomplete specifications
19618 of complex data structure. If the debug information included in the
19619 program does not allow @value{GDBN} to display a full declaration of
19620 the data type, it will say @samp{<incomplete type>}. For example,
19621 given these declarations:
19625 struct foo *fooptr;
19629 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19632 (@value{GDBP}) ptype foo
19633 $1 = <incomplete type>
19637 ``Incomplete type'' is C terminology for data types that are not
19638 completely specified.
19640 @cindex unknown type
19641 Othertimes, information about a variable's type is completely absent
19642 from the debug information included in the program. This most often
19643 happens when the program or library where the variable is defined
19644 includes no debug information at all. @value{GDBN} knows the variable
19645 exists from inspecting the linker/loader symbol table (e.g., the ELF
19646 dynamic symbol table), but such symbols do not contain type
19647 information. Inspecting the type of a (global) variable for which
19648 @value{GDBN} has no type information shows:
19651 (@value{GDBP}) ptype var
19652 type = <data variable, no debug info>
19655 @xref{Variables, no debug info variables}, for how to print the values
19659 @item info types [-q] [@var{regexp}]
19660 Print a brief description of all types whose names match the regular
19661 expression @var{regexp} (or all types in your program, if you supply
19662 no argument). Each complete typename is matched as though it were a
19663 complete line; thus, @samp{i type value} gives information on all
19664 types in your program whose names include the string @code{value}, but
19665 @samp{i type ^value$} gives information only on types whose complete
19666 name is @code{value}.
19668 In programs using different languages, @value{GDBN} chooses the syntax
19669 to print the type description according to the
19670 @samp{set language} value: using @samp{set language auto}
19671 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19672 language of the type, other values mean to use
19673 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19675 This command differs from @code{ptype} in two ways: first, like
19676 @code{whatis}, it does not print a detailed description; second, it
19677 lists all source files and line numbers where a type is defined.
19679 The output from @samp{into types} is proceeded with a header line
19680 describing what types are being listed. The optional flag @samp{-q},
19681 which stands for @samp{quiet}, disables printing this header
19684 @kindex info type-printers
19685 @item info type-printers
19686 Versions of @value{GDBN} that ship with Python scripting enabled may
19687 have ``type printers'' available. When using @command{ptype} or
19688 @command{whatis}, these printers are consulted when the name of a type
19689 is needed. @xref{Type Printing API}, for more information on writing
19692 @code{info type-printers} displays all the available type printers.
19694 @kindex enable type-printer
19695 @kindex disable type-printer
19696 @item enable type-printer @var{name}@dots{}
19697 @item disable type-printer @var{name}@dots{}
19698 These commands can be used to enable or disable type printers.
19701 @cindex local variables
19702 @item info scope @var{locspec}
19703 List all the variables local to the lexical scope of the code location
19704 that results from resolving @var{locspec}. @xref{Location
19705 Specifications}, for details about supported forms of @var{locspec}.
19709 (@value{GDBP}) @b{info scope command_line_handler}
19710 Scope for command_line_handler:
19711 Symbol rl is an argument at stack/frame offset 8, length 4.
19712 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19713 Symbol linelength is in static storage at address 0x150a1c, length 4.
19714 Symbol p is a local variable in register $esi, length 4.
19715 Symbol p1 is a local variable in register $ebx, length 4.
19716 Symbol nline is a local variable in register $edx, length 4.
19717 Symbol repeat is a local variable at frame offset -8, length 4.
19721 This command is especially useful for determining what data to collect
19722 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19725 @kindex info source
19727 Show information about the current source file---that is, the source file for
19728 the function containing the current point of execution:
19731 the name of the source file, and the directory containing it,
19733 the directory it was compiled in,
19735 its length, in lines,
19737 which programming language it is written in,
19739 if the debug information provides it, the program that compiled the file
19740 (which may include, e.g., the compiler version and command line arguments),
19742 whether the executable includes debugging information for that file, and
19743 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19745 whether the debugging information includes information about
19746 preprocessor macros.
19750 @kindex info sources
19751 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19754 With no options @samp{info sources} prints the names of all source
19755 files in your program for which there is debugging information. The
19756 source files are presented based on a list of object files
19757 (executables and libraries) currently loaded into @value{GDBN}. For
19758 each object file all of the associated source files are listed.
19760 Each source file will only be printed once for each object file, but a
19761 single source file can be repeated in the output if it is part of
19762 multiple object files.
19764 If the optional @var{regexp} is provided, then only source files that
19765 match the regular expression will be printed. The matching is
19766 case-sensitive, except on operating systems that have case-insensitive
19767 filesystem (e.g., MS-Windows). @samp{--} can be used before
19768 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19769 command option (e.g. if @var{regexp} starts with @samp{-}).
19771 By default, the @var{regexp} is used to match anywhere in the
19772 filename. If @code{-dirname}, only files having a dirname matching
19773 @var{regexp} are shown. If @code{-basename}, only files having a
19774 basename matching @var{regexp} are shown.
19776 It is possible that an object file may be printed in the list with no
19777 associated source files. This can happen when either no source files
19778 match @var{regexp}, or, the object file was compiled without debug
19779 information and so @value{GDBN} is unable to find any source file
19782 @kindex info functions
19783 @item info functions [-q] [-n]
19784 Print the names and data types of all defined functions.
19785 Similarly to @samp{info types}, this command groups its output by source
19786 files and annotates each function definition with its source line
19789 In programs using different languages, @value{GDBN} chooses the syntax
19790 to print the function name and type according to the
19791 @samp{set language} value: using @samp{set language auto}
19792 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19793 language of the function, other values mean to use
19794 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19796 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19797 results. A non-debugging symbol is a symbol that comes from the
19798 executable's symbol table, not from the debug information (for
19799 example, DWARF) associated with the executable.
19801 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19802 printing header information and messages explaining why no functions
19805 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19806 Like @samp{info functions}, but only print the names and data types
19807 of the functions selected with the provided regexp(s).
19809 If @var{regexp} is provided, print only the functions whose names
19810 match the regular expression @var{regexp}.
19811 Thus, @samp{info fun step} finds all functions whose
19812 names include @code{step}; @samp{info fun ^step} finds those whose names
19813 start with @code{step}. If a function name contains characters that
19814 conflict with the regular expression language (e.g.@:
19815 @samp{operator*()}), they may be quoted with a backslash.
19817 If @var{type_regexp} is provided, print only the functions whose
19818 types, as printed by the @code{whatis} command, match
19819 the regular expression @var{type_regexp}.
19820 If @var{type_regexp} contains space(s), it should be enclosed in
19821 quote characters. If needed, use backslash to escape the meaning
19822 of special characters or quotes.
19823 Thus, @samp{info fun -t '^int ('} finds the functions that return
19824 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19825 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19826 finds the functions whose names start with @code{step} and that return
19829 If both @var{regexp} and @var{type_regexp} are provided, a function
19830 is printed only if its name matches @var{regexp} and its type matches
19834 @kindex info variables
19835 @item info variables [-q] [-n]
19836 Print the names and data types of all variables that are defined
19837 outside of functions (i.e.@: excluding local variables).
19838 The printed variables are grouped by source files and annotated with
19839 their respective source line numbers.
19841 In programs using different languages, @value{GDBN} chooses the syntax
19842 to print the variable name and type according to the
19843 @samp{set language} value: using @samp{set language auto}
19844 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19845 language of the variable, other values mean to use
19846 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19848 The @samp{-n} flag excludes non-debugging symbols from the results.
19850 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19851 printing header information and messages explaining why no variables
19854 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19855 Like @kbd{info variables}, but only print the variables selected
19856 with the provided regexp(s).
19858 If @var{regexp} is provided, print only the variables whose names
19859 match the regular expression @var{regexp}.
19861 If @var{type_regexp} is provided, print only the variables whose
19862 types, as printed by the @code{whatis} command, match
19863 the regular expression @var{type_regexp}.
19864 If @var{type_regexp} contains space(s), it should be enclosed in
19865 quote characters. If needed, use backslash to escape the meaning
19866 of special characters or quotes.
19868 If both @var{regexp} and @var{type_regexp} are provided, an argument
19869 is printed only if its name matches @var{regexp} and its type matches
19872 @kindex info modules
19874 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19875 List all Fortran modules in the program, or all modules matching the
19876 optional regular expression @var{regexp}.
19878 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19879 printing header information and messages explaining why no modules
19882 @kindex info module
19883 @cindex Fortran modules, information about
19884 @cindex functions and variables by Fortran module
19885 @cindex module functions and variables
19886 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19887 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19888 List all functions or variables within all Fortran modules. The set
19889 of functions or variables listed can be limited by providing some or
19890 all of the optional regular expressions. If @var{module-regexp} is
19891 provided, then only Fortran modules matching @var{module-regexp} will
19892 be searched. Only functions or variables whose type matches the
19893 optional regular expression @var{type-regexp} will be listed. And
19894 only functions or variables whose name matches the optional regular
19895 expression @var{regexp} will be listed.
19897 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19898 printing header information and messages explaining why no functions
19899 or variables have been printed.
19901 @kindex info classes
19902 @cindex Objective-C, classes and selectors
19904 @itemx info classes @var{regexp}
19905 Display all Objective-C classes in your program, or
19906 (with the @var{regexp} argument) all those matching a particular regular
19909 @kindex info selectors
19910 @item info selectors
19911 @itemx info selectors @var{regexp}
19912 Display all Objective-C selectors in your program, or
19913 (with the @var{regexp} argument) all those matching a particular regular
19917 This was never implemented.
19918 @kindex info methods
19920 @itemx info methods @var{regexp}
19921 The @code{info methods} command permits the user to examine all defined
19922 methods within C@t{++} program, or (with the @var{regexp} argument) a
19923 specific set of methods found in the various C@t{++} classes. Many
19924 C@t{++} classes provide a large number of methods. Thus, the output
19925 from the @code{ptype} command can be overwhelming and hard to use. The
19926 @code{info-methods} command filters the methods, printing only those
19927 which match the regular-expression @var{regexp}.
19930 @cindex opaque data types
19931 @kindex set opaque-type-resolution
19932 @item set opaque-type-resolution on
19933 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19934 declared as a pointer to a @code{struct}, @code{class}, or
19935 @code{union}---for example, @code{struct MyType *}---that is used in one
19936 source file although the full declaration of @code{struct MyType} is in
19937 another source file. The default is on.
19939 A change in the setting of this subcommand will not take effect until
19940 the next time symbols for a file are loaded.
19942 @item set opaque-type-resolution off
19943 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19944 is printed as follows:
19946 @{<no data fields>@}
19949 @kindex show opaque-type-resolution
19950 @item show opaque-type-resolution
19951 Show whether opaque types are resolved or not.
19953 @kindex set print symbol-loading
19954 @cindex print messages when symbols are loaded
19955 @item set print symbol-loading
19956 @itemx set print symbol-loading full
19957 @itemx set print symbol-loading brief
19958 @itemx set print symbol-loading off
19959 The @code{set print symbol-loading} command allows you to control the
19960 printing of messages when @value{GDBN} loads symbol information.
19961 By default a message is printed for the executable and one for each
19962 shared library, and normally this is what you want. However, when
19963 debugging apps with large numbers of shared libraries these messages
19965 When set to @code{brief} a message is printed for each executable,
19966 and when @value{GDBN} loads a collection of shared libraries at once
19967 it will only print one message regardless of the number of shared
19968 libraries. When set to @code{off} no messages are printed.
19970 @kindex show print symbol-loading
19971 @item show print symbol-loading
19972 Show whether messages will be printed when a @value{GDBN} command
19973 entered from the keyboard causes symbol information to be loaded.
19975 @kindex maint print symbols
19976 @cindex symbol dump
19977 @kindex maint print psymbols
19978 @cindex partial symbol dump
19979 @kindex maint print msymbols
19980 @cindex minimal symbol dump
19981 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19982 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19983 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19984 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19985 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19986 Write a dump of debugging symbol data into the file @var{filename} or
19987 the terminal if @var{filename} is unspecified.
19988 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19990 If @code{-pc @var{address}} is specified, only dump symbols for the file
19991 with code at that address. Note that @var{address} may be a symbol like
19993 If @code{-source @var{source}} is specified, only dump symbols for that
19996 These commands are used to debug the @value{GDBN} symbol-reading code.
19997 These commands do not modify internal @value{GDBN} state, therefore
19998 @samp{maint print symbols} will only print symbols for already expanded symbol
20000 You can use the command @code{info sources} to find out which files these are.
20001 If you use @samp{maint print psymbols} instead, the dump shows information
20002 about symbols that @value{GDBN} only knows partially---that is, symbols
20003 defined in files that @value{GDBN} has skimmed, but not yet read completely.
20004 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
20007 @xref{Files, ,Commands to Specify Files}, for a discussion of how
20008 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
20010 @kindex maint info symtabs
20011 @kindex maint info psymtabs
20012 @cindex listing @value{GDBN}'s internal symbol tables
20013 @cindex symbol tables, listing @value{GDBN}'s internal
20014 @cindex full symbol tables, listing @value{GDBN}'s internal
20015 @cindex partial symbol tables, listing @value{GDBN}'s internal
20016 @item maint info symtabs @r{[} @var{regexp} @r{]}
20017 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
20019 List the @code{struct symtab} or @code{struct partial_symtab}
20020 structures whose names match @var{regexp}. If @var{regexp} is not
20021 given, list them all. The output includes expressions which you can
20022 copy into a @value{GDBN} debugging this one to examine a particular
20023 structure in more detail. For example:
20026 (@value{GDBP}) maint info psymtabs dwarf2read
20027 @{ objfile /home/gnu/build/gdb/gdb
20028 ((struct objfile *) 0x82e69d0)
20029 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
20030 ((struct partial_symtab *) 0x8474b10)
20033 text addresses 0x814d3c8 -- 0x8158074
20034 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
20035 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
20036 dependencies (none)
20039 (@value{GDBP}) maint info symtabs
20043 We see that there is one partial symbol table whose filename contains
20044 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
20045 and we see that @value{GDBN} has not read in any symtabs yet at all.
20046 If we set a breakpoint on a function, that will cause @value{GDBN} to
20047 read the symtab for the compilation unit containing that function:
20050 (@value{GDBP}) break dwarf2_psymtab_to_symtab
20051 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
20053 (@value{GDBP}) maint info symtabs
20054 @{ objfile /home/gnu/build/gdb/gdb
20055 ((struct objfile *) 0x82e69d0)
20056 @{ symtab /home/gnu/src/gdb/dwarf2read.c
20057 ((struct symtab *) 0x86c1f38)
20060 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
20061 linetable ((struct linetable *) 0x8370fa0)
20062 debugformat DWARF 2
20068 @kindex maint info line-table
20069 @cindex listing @value{GDBN}'s internal line tables
20070 @cindex line tables, listing @value{GDBN}'s internal
20071 @item maint info line-table @r{[} @var{regexp} @r{]}
20073 List the @code{struct linetable} from all @code{struct symtab}
20074 instances whose name matches @var{regexp}. If @var{regexp} is not
20075 given, list the @code{struct linetable} from all @code{struct symtab}.
20079 (@value{GDBP}) maint info line-table
20080 objfile: /home/gnu/build/a.out ((struct objfile *) 0x6120000e0d40)
20081 compunit_symtab: simple.cpp ((struct compunit_symtab *) 0x6210000ff450)
20082 symtab: /home/gnu/src/simple.cpp ((struct symtab *) 0x6210000ff4d0)
20083 linetable: ((struct linetable *) 0x62100012b760):
20084 INDEX LINE ADDRESS IS-STMT PROLOGUE-END
20085 0 3 0x0000000000401110 Y
20086 1 4 0x0000000000401114 Y Y
20087 2 9 0x0000000000401120 Y
20088 3 10 0x0000000000401124 Y Y
20089 4 10 0x0000000000401129
20090 5 15 0x0000000000401130 Y
20091 6 16 0x0000000000401134 Y Y
20092 7 16 0x0000000000401139
20093 8 21 0x0000000000401140 Y
20094 9 22 0x000000000040114f Y Y
20095 10 22 0x0000000000401154
20096 11 END 0x000000000040115a Y
20099 The @samp{IS-STMT} column indicates if the address is a recommended breakpoint
20100 location to represent a line or a statement. The @samp{PROLOGUE-END} column
20101 indicates that a given address is an adequate place to set a breakpoint at the
20102 first instruction following a function prologue.
20104 @kindex maint set symbol-cache-size
20105 @cindex symbol cache size
20106 @item maint set symbol-cache-size @var{size}
20107 Set the size of the symbol cache to @var{size}.
20108 The default size is intended to be good enough for debugging
20109 most applications. This option exists to allow for experimenting
20110 with different sizes.
20112 @kindex maint show symbol-cache-size
20113 @item maint show symbol-cache-size
20114 Show the size of the symbol cache.
20116 @kindex maint print symbol-cache
20117 @cindex symbol cache, printing its contents
20118 @item maint print symbol-cache
20119 Print the contents of the symbol cache.
20120 This is useful when debugging symbol cache issues.
20122 @kindex maint print symbol-cache-statistics
20123 @cindex symbol cache, printing usage statistics
20124 @item maint print symbol-cache-statistics
20125 Print symbol cache usage statistics.
20126 This helps determine how well the cache is being utilized.
20128 @kindex maint flush symbol-cache
20129 @kindex maint flush-symbol-cache
20130 @cindex symbol cache, flushing
20131 @item maint flush symbol-cache
20132 @itemx maint flush-symbol-cache
20133 Flush the contents of the symbol cache, all entries are removed. This
20134 command is useful when debugging the symbol cache. It is also useful
20135 when collecting performance data. The command @code{maint
20136 flush-symbol-cache} is deprecated in favor of @code{maint flush
20139 @kindex maint set ignore-prologue-end-flag
20140 @cindex prologue-end
20141 @item maint set ignore-prologue-end-flag [on|off]
20142 Enable or disable the use of the @samp{PROLOGUE-END} flag from the line-table.
20143 When @samp{off} (the default), @value{GDBN} uses the @samp{PROLOGUE-END} flag
20144 to place breakpoints past the end of a function prologue. When @samp{on},
20145 @value{GDBN} ignores the flag and relies on prologue analyzers to skip function
20148 @kindex maint show ignore-prologue-end-flag
20149 @item maint show ignore-prologue-end-flag
20150 Show whether @value{GDBN} will ignore the @samp{PROLOGUE-END} flag.
20155 @chapter Altering Execution
20157 Once you think you have found an error in your program, you might want to
20158 find out for certain whether correcting the apparent error would lead to
20159 correct results in the rest of the run. You can find the answer by
20160 experiment, using the @value{GDBN} features for altering execution of the
20163 For example, you can store new values into variables or memory
20164 locations, give your program a signal, restart it at a different
20165 address, or even return prematurely from a function.
20168 * Assignment:: Assignment to variables
20169 * Jumping:: Continuing at a different address
20170 * Signaling:: Giving your program a signal
20171 * Returning:: Returning from a function
20172 * Calling:: Calling your program's functions
20173 * Patching:: Patching your program
20174 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
20178 @section Assignment to Variables
20181 @cindex setting variables
20182 To alter the value of a variable, evaluate an assignment expression.
20183 @xref{Expressions, ,Expressions}. For example,
20190 stores the value 4 into the variable @code{x}, and then prints the
20191 value of the assignment expression (which is 4).
20192 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
20193 information on operators in supported languages.
20195 @kindex set variable
20196 @cindex variables, setting
20197 If you are not interested in seeing the value of the assignment, use the
20198 @code{set} command instead of the @code{print} command. @code{set} is
20199 really the same as @code{print} except that the expression's value is
20200 not printed and is not put in the value history (@pxref{Value History,
20201 ,Value History}). The expression is evaluated only for its effects.
20203 If the beginning of the argument string of the @code{set} command
20204 appears identical to a @code{set} subcommand, use the @code{set
20205 variable} command instead of just @code{set}. This command is identical
20206 to @code{set} except for its lack of subcommands. For example, if your
20207 program has a variable @code{width}, you get an error if you try to set
20208 a new value with just @samp{set width=13}, because @value{GDBN} has the
20209 command @code{set width}:
20212 (@value{GDBP}) whatis width
20214 (@value{GDBP}) p width
20216 (@value{GDBP}) set width=47
20217 Invalid syntax in expression.
20221 The invalid expression, of course, is @samp{=47}. In
20222 order to actually set the program's variable @code{width}, use
20225 (@value{GDBP}) set var width=47
20228 Because the @code{set} command has many subcommands that can conflict
20229 with the names of program variables, it is a good idea to use the
20230 @code{set variable} command instead of just @code{set}. For example, if
20231 your program has a variable @code{g}, you run into problems if you try
20232 to set a new value with just @samp{set g=4}, because @value{GDBN} has
20233 the command @code{set gnutarget}, abbreviated @code{set g}:
20237 (@value{GDBP}) whatis g
20241 (@value{GDBP}) set g=4
20245 The program being debugged has been started already.
20246 Start it from the beginning? (y or n) y
20247 Starting program: /home/smith/cc_progs/a.out
20248 "/home/smith/cc_progs/a.out": can't open to read symbols:
20249 Invalid bfd target.
20250 (@value{GDBP}) show g
20251 The current BFD target is "=4".
20256 The program variable @code{g} did not change, and you silently set the
20257 @code{gnutarget} to an invalid value. In order to set the variable
20261 (@value{GDBP}) set var g=4
20264 @value{GDBN} allows more implicit conversions in assignments than C; you can
20265 freely store an integer value into a pointer variable or vice versa,
20266 and you can convert any structure to any other structure that is the
20267 same length or shorter.
20268 @comment FIXME: how do structs align/pad in these conversions?
20269 @comment /doc@cygnus.com 18dec1990
20271 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
20272 construct to generate a value of specified type at a specified address
20273 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
20274 to memory location @code{0x83040} as an integer (which implies a certain size
20275 and representation in memory), and
20278 set @{int@}0x83040 = 4
20282 stores the value 4 into that memory location.
20285 @section Continuing at a Different Address
20287 Ordinarily, when you continue your program, you do so at the place where
20288 it stopped, with the @code{continue} command. You can instead continue at
20289 an address of your own choosing, with the following commands:
20293 @kindex j @r{(@code{jump})}
20294 @item jump @var{locspec}
20295 @itemx j @var{locspec}
20296 Resume execution at the address of the code location that results from
20297 resolving @var{locspec}.
20298 @xref{Location Specifications}, for a description of the different
20299 forms of @var{locspec}. If @var{locspec} resolves to more than one
20300 address, the command aborts before jumping.
20301 Execution stops again immediately if there is a breakpoint there. It
20302 is common practice to use the @code{tbreak} command in conjunction
20303 with @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
20305 The @code{jump} command does not change the current stack frame, or
20306 the stack pointer, or the contents of any memory location or any
20307 register other than the program counter. If @var{locspec} resolves to
20308 an address in a different function from the one currently executing, the
20309 results may be bizarre if the two functions expect different patterns
20310 of arguments or of local variables. For this reason, the @code{jump}
20311 command requests confirmation if the jump address is not in the
20312 function currently executing. However, even bizarre results are
20313 predictable if you are well acquainted with the machine-language code
20317 On many systems, you can get much the same effect as the @code{jump}
20318 command by storing a new value into the register @code{$pc}. The
20319 difference is that this does not start your program running; it only
20320 changes the address of where it @emph{will} run when you continue. For
20328 makes the next @code{continue} command or stepping command execute at
20329 address @code{0x485}, rather than at the address where your program stopped.
20330 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20332 The most common occasion to use the @code{jump} command is to back
20333 up---perhaps with more breakpoints set---over a portion of a program
20334 that has already executed, in order to examine its execution in more
20339 @section Giving your Program a Signal
20340 @cindex deliver a signal to a program
20344 @item signal @var{signal}
20345 Resume execution where your program is stopped, but immediately give it the
20346 signal @var{signal}. The @var{signal} can be the name or the number of a
20347 signal. For example, on many systems @code{signal 2} and @code{signal
20348 SIGINT} are both ways of sending an interrupt signal.
20350 Alternatively, if @var{signal} is zero, continue execution without
20351 giving a signal. This is useful when your program stopped on account of
20352 a signal and would ordinarily see the signal when resumed with the
20353 @code{continue} command; @samp{signal 0} causes it to resume without a
20356 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20357 delivered to the currently selected thread, not the thread that last
20358 reported a stop. This includes the situation where a thread was
20359 stopped due to a signal. So if you want to continue execution
20360 suppressing the signal that stopped a thread, you should select that
20361 same thread before issuing the @samp{signal 0} command. If you issue
20362 the @samp{signal 0} command with another thread as the selected one,
20363 @value{GDBN} detects that and asks for confirmation.
20365 Invoking the @code{signal} command is not the same as invoking the
20366 @code{kill} utility from the shell. Sending a signal with @code{kill}
20367 causes @value{GDBN} to decide what to do with the signal depending on
20368 the signal handling tables (@pxref{Signals}). The @code{signal} command
20369 passes the signal directly to your program.
20371 @code{signal} does not repeat when you press @key{RET} a second time
20372 after executing the command.
20374 @kindex queue-signal
20375 @item queue-signal @var{signal}
20376 Queue @var{signal} to be delivered immediately to the current thread
20377 when execution of the thread resumes. The @var{signal} can be the name or
20378 the number of a signal. For example, on many systems @code{signal 2} and
20379 @code{signal SIGINT} are both ways of sending an interrupt signal.
20380 The handling of the signal must be set to pass the signal to the program,
20381 otherwise @value{GDBN} will report an error.
20382 You can control the handling of signals from @value{GDBN} with the
20383 @code{handle} command (@pxref{Signals}).
20385 Alternatively, if @var{signal} is zero, any currently queued signal
20386 for the current thread is discarded and when execution resumes no signal
20387 will be delivered. This is useful when your program stopped on account
20388 of a signal and would ordinarily see the signal when resumed with the
20389 @code{continue} command.
20391 This command differs from the @code{signal} command in that the signal
20392 is just queued, execution is not resumed. And @code{queue-signal} cannot
20393 be used to pass a signal whose handling state has been set to @code{nopass}
20398 @xref{stepping into signal handlers}, for information on how stepping
20399 commands behave when the thread has a signal queued.
20402 @section Returning from a Function
20405 @cindex returning from a function
20408 @itemx return @var{expression}
20409 You can cancel execution of a function call with the @code{return}
20410 command. If you give an
20411 @var{expression} argument, its value is used as the function's return
20415 When you use @code{return}, @value{GDBN} discards the selected stack frame
20416 (and all frames within it). You can think of this as making the
20417 discarded frame return prematurely. If you wish to specify a value to
20418 be returned, give that value as the argument to @code{return}.
20420 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20421 Frame}), and any other frames inside of it, leaving its caller as the
20422 innermost remaining frame. That frame becomes selected. The
20423 specified value is stored in the registers used for returning values
20426 The @code{return} command does not resume execution; it leaves the
20427 program stopped in the state that would exist if the function had just
20428 returned. In contrast, the @code{finish} command (@pxref{Continuing
20429 and Stepping, ,Continuing and Stepping}) resumes execution until the
20430 selected stack frame returns naturally.
20432 @value{GDBN} needs to know how the @var{expression} argument should be set for
20433 the inferior. The concrete registers assignment depends on the OS ABI and the
20434 type being returned by the selected stack frame. For example it is common for
20435 OS ABI to return floating point values in FPU registers while integer values in
20436 CPU registers. Still some ABIs return even floating point values in CPU
20437 registers. Larger integer widths (such as @code{long long int}) also have
20438 specific placement rules. @value{GDBN} already knows the OS ABI from its
20439 current target so it needs to find out also the type being returned to make the
20440 assignment into the right register(s).
20442 Normally, the selected stack frame has debug info. @value{GDBN} will always
20443 use the debug info instead of the implicit type of @var{expression} when the
20444 debug info is available. For example, if you type @kbd{return -1}, and the
20445 function in the current stack frame is declared to return a @code{long long
20446 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20447 into a @code{long long int}:
20450 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20452 (@value{GDBP}) return -1
20453 Make func return now? (y or n) y
20454 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20455 43 printf ("result=%lld\n", func ());
20459 However, if the selected stack frame does not have a debug info, e.g., if the
20460 function was compiled without debug info, @value{GDBN} has to find out the type
20461 to return from user. Specifying a different type by mistake may set the value
20462 in different inferior registers than the caller code expects. For example,
20463 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20464 of a @code{long long int} result for a debug info less function (on 32-bit
20465 architectures). Therefore the user is required to specify the return type by
20466 an appropriate cast explicitly:
20469 Breakpoint 2, 0x0040050b in func ()
20470 (@value{GDBP}) return -1
20471 Return value type not available for selected stack frame.
20472 Please use an explicit cast of the value to return.
20473 (@value{GDBP}) return (long long int) -1
20474 Make selected stack frame return now? (y or n) y
20475 #0 0x00400526 in main ()
20480 @section Calling Program Functions
20483 @cindex calling functions
20484 @cindex inferior functions, calling
20485 @item print @var{expr}
20486 Evaluate the expression @var{expr} and display the resulting value.
20487 The expression may include calls to functions in the program being
20491 @item call @var{expr}
20492 Evaluate the expression @var{expr} without displaying @code{void}
20495 You can use this variant of the @code{print} command if you want to
20496 execute a function from your program that does not return anything
20497 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20498 with @code{void} returned values that @value{GDBN} will otherwise
20499 print. If the result is not void, it is printed and saved in the
20503 It is possible for the function you call via the @code{print} or
20504 @code{call} command to generate a signal (e.g., if there's a bug in
20505 the function, or if you passed it incorrect arguments). What happens
20506 in that case is controlled by the @code{set unwindonsignal} command.
20508 Similarly, with a C@t{++} program it is possible for the function you
20509 call via the @code{print} or @code{call} command to generate an
20510 exception that is not handled due to the constraints of the dummy
20511 frame. In this case, any exception that is raised in the frame, but has
20512 an out-of-frame exception handler will not be found. GDB builds a
20513 dummy-frame for the inferior function call, and the unwinder cannot
20514 seek for exception handlers outside of this dummy-frame. What happens
20515 in that case is controlled by the
20516 @code{set unwind-on-terminating-exception} command.
20519 @item set unwindonsignal
20520 @kindex set unwindonsignal
20521 @cindex unwind stack in called functions
20522 @cindex call dummy stack unwinding
20523 Set unwinding of the stack if a signal is received while in a function
20524 that @value{GDBN} called in the program being debugged. If set to on,
20525 @value{GDBN} unwinds the stack it created for the call and restores
20526 the context to what it was before the call. If set to off (the
20527 default), @value{GDBN} stops in the frame where the signal was
20530 @item show unwindonsignal
20531 @kindex show unwindonsignal
20532 Show the current setting of stack unwinding in the functions called by
20535 @item set unwind-on-terminating-exception
20536 @kindex set unwind-on-terminating-exception
20537 @cindex unwind stack in called functions with unhandled exceptions
20538 @cindex call dummy stack unwinding on unhandled exception.
20539 Set unwinding of the stack if a C@t{++} exception is raised, but left
20540 unhandled while in a function that @value{GDBN} called in the program being
20541 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20542 it created for the call and restores the context to what it was before
20543 the call. If set to off, @value{GDBN} the exception is delivered to
20544 the default C@t{++} exception handler and the inferior terminated.
20546 @item show unwind-on-terminating-exception
20547 @kindex show unwind-on-terminating-exception
20548 Show the current setting of stack unwinding in the functions called by
20551 @item set may-call-functions
20552 @kindex set may-call-functions
20553 @cindex disabling calling functions in the program
20554 @cindex calling functions in the program, disabling
20555 Set permission to call functions in the program.
20556 This controls whether @value{GDBN} will attempt to call functions in
20557 the program, such as with expressions in the @code{print} command. It
20558 defaults to @code{on}.
20560 To call a function in the program, @value{GDBN} has to temporarily
20561 modify the state of the inferior. This has potentially undesired side
20562 effects. Also, having @value{GDBN} call nested functions is likely to
20563 be erroneous and may even crash the program being debugged. You can
20564 avoid such hazards by forbidding @value{GDBN} from calling functions
20565 in the program being debugged. If calling functions in the program
20566 is forbidden, GDB will throw an error when a command (such as printing
20567 an expression) starts a function call in the program.
20569 @item show may-call-functions
20570 @kindex show may-call-functions
20571 Show permission to call functions in the program.
20575 @subsection Calling functions with no debug info
20577 @cindex no debug info functions
20578 Sometimes, a function you wish to call is missing debug information.
20579 In such case, @value{GDBN} does not know the type of the function,
20580 including the types of the function's parameters. To avoid calling
20581 the inferior function incorrectly, which could result in the called
20582 function functioning erroneously and even crash, @value{GDBN} refuses
20583 to call the function unless you tell it the type of the function.
20585 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20586 to do that. The simplest is to cast the call to the function's
20587 declared return type. For example:
20590 (@value{GDBP}) p getenv ("PATH")
20591 'getenv' has unknown return type; cast the call to its declared return type
20592 (@value{GDBP}) p (char *) getenv ("PATH")
20593 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20596 Casting the return type of a no-debug function is equivalent to
20597 casting the function to a pointer to a prototyped function that has a
20598 prototype that matches the types of the passed-in arguments, and
20599 calling that. I.e., the call above is equivalent to:
20602 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20606 and given this prototyped C or C++ function with float parameters:
20609 float multiply (float v1, float v2) @{ return v1 * v2; @}
20613 these calls are equivalent:
20616 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20617 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20620 If the function you wish to call is declared as unprototyped (i.e.@:
20621 old K&R style), you must use the cast-to-function-pointer syntax, so
20622 that @value{GDBN} knows that it needs to apply default argument
20623 promotions (promote float arguments to double). @xref{ABI, float
20624 promotion}. For example, given this unprototyped C function with
20625 float parameters, and no debug info:
20629 multiply_noproto (v1, v2)
20637 you call it like this:
20640 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20644 @section Patching Programs
20646 @cindex patching binaries
20647 @cindex writing into executables
20648 @cindex writing into corefiles
20650 By default, @value{GDBN} opens the file containing your program's
20651 executable code (or the corefile) read-only. This prevents accidental
20652 alterations to machine code; but it also prevents you from intentionally
20653 patching your program's binary.
20655 If you'd like to be able to patch the binary, you can specify that
20656 explicitly with the @code{set write} command. For example, you might
20657 want to turn on internal debugging flags, or even to make emergency
20663 @itemx set write off
20664 If you specify @samp{set write on}, @value{GDBN} opens executable and
20665 core files for both reading and writing; if you specify @kbd{set write
20666 off} (the default), @value{GDBN} opens them read-only.
20668 If you have already loaded a file, you must load it again (using the
20669 @code{exec-file} or @code{core-file} command) after changing @code{set
20670 write}, for your new setting to take effect.
20674 Display whether executable files and core files are opened for writing
20675 as well as reading.
20678 @node Compiling and Injecting Code
20679 @section Compiling and injecting code in @value{GDBN}
20680 @cindex injecting code
20681 @cindex writing into executables
20682 @cindex compiling code
20684 @value{GDBN} supports on-demand compilation and code injection into
20685 programs running under @value{GDBN}. GCC 5.0 or higher built with
20686 @file{libcc1.so} must be installed for this functionality to be enabled.
20687 This functionality is implemented with the following commands.
20690 @kindex compile code
20691 @item compile code @var{source-code}
20692 @itemx compile code -raw @var{--} @var{source-code}
20693 Compile @var{source-code} with the compiler language found as the current
20694 language in @value{GDBN} (@pxref{Languages}). If compilation and
20695 injection is not supported with the current language specified in
20696 @value{GDBN}, or the compiler does not support this feature, an error
20697 message will be printed. If @var{source-code} compiles and links
20698 successfully, @value{GDBN} will load the object-code emitted,
20699 and execute it within the context of the currently selected inferior.
20700 It is important to note that the compiled code is executed immediately.
20701 After execution, the compiled code is removed from @value{GDBN} and any
20702 new types or variables you have defined will be deleted.
20704 The command allows you to specify @var{source-code} in two ways.
20705 The simplest method is to provide a single line of code to the command.
20709 compile code printf ("hello world\n");
20712 If you specify options on the command line as well as source code, they
20713 may conflict. The @samp{--} delimiter can be used to separate options
20714 from actual source code. E.g.:
20717 compile code -r -- printf ("hello world\n");
20720 Alternatively you can enter source code as multiple lines of text. To
20721 enter this mode, invoke the @samp{compile code} command without any text
20722 following the command. This will start the multiple-line editor and
20723 allow you to type as many lines of source code as required. When you
20724 have completed typing, enter @samp{end} on its own line to exit the
20729 >printf ("hello\n");
20730 >printf ("world\n");
20734 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20735 provided @var{source-code} in a callable scope. In this case, you must
20736 specify the entry point of the code by defining a function named
20737 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20738 inferior. Using @samp{-raw} option may be needed for example when
20739 @var{source-code} requires @samp{#include} lines which may conflict with
20740 inferior symbols otherwise.
20742 @kindex compile file
20743 @item compile file @var{filename}
20744 @itemx compile file -raw @var{filename}
20745 Like @code{compile code}, but take the source code from @var{filename}.
20748 compile file /home/user/example.c
20753 @item compile print [[@var{options}] --] @var{expr}
20754 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20755 Compile and execute @var{expr} with the compiler language found as the
20756 current language in @value{GDBN} (@pxref{Languages}). By default the
20757 value of @var{expr} is printed in a format appropriate to its data type;
20758 you can choose a different format by specifying @samp{/@var{f}}, where
20759 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20760 Formats}. The @code{compile print} command accepts the same options
20761 as the @code{print} command; see @ref{print options}.
20763 @item compile print [[@var{options}] --]
20764 @itemx compile print [[@var{options}] --] /@var{f}
20765 @cindex reprint the last value
20766 Alternatively you can enter the expression (source code producing it) as
20767 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20768 command without any text following the command. This will start the
20769 multiple-line editor.
20773 The process of compiling and injecting the code can be inspected using:
20776 @anchor{set debug compile}
20777 @item set debug compile
20778 @cindex compile command debugging info
20779 Turns on or off display of @value{GDBN} process of compiling and
20780 injecting the code. The default is off.
20782 @item show debug compile
20783 Displays the current state of displaying @value{GDBN} process of
20784 compiling and injecting the code.
20786 @anchor{set debug compile-cplus-types}
20787 @item set debug compile-cplus-types
20788 @cindex compile C@t{++} type conversion
20789 Turns on or off the display of C@t{++} type conversion debugging information.
20790 The default is off.
20792 @item show debug compile-cplus-types
20793 Displays the current state of displaying debugging information for
20794 C@t{++} type conversion.
20797 @subsection Compilation options for the @code{compile} command
20799 @value{GDBN} needs to specify the right compilation options for the code
20800 to be injected, in part to make its ABI compatible with the inferior
20801 and in part to make the injected code compatible with @value{GDBN}'s
20805 The options used, in increasing precedence:
20808 @item target architecture and OS options (@code{gdbarch})
20809 These options depend on target processor type and target operating
20810 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20811 (@code{-m64}) compilation option.
20813 @item compilation options recorded in the target
20814 @value{NGCC} (since version 4.7) stores the options used for compilation
20815 into @code{DW_AT_producer} part of DWARF debugging information according
20816 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20817 explicitly specify @code{-g} during inferior compilation otherwise
20818 @value{NGCC} produces no DWARF. This feature is only relevant for
20819 platforms where @code{-g} produces DWARF by default, otherwise one may
20820 try to enforce DWARF by using @code{-gdwarf-4}.
20822 @item compilation options set by @code{set compile-args}
20826 You can override compilation options using the following command:
20829 @item set compile-args
20830 @cindex compile command options override
20831 Set compilation options used for compiling and injecting code with the
20832 @code{compile} commands. These options override any conflicting ones
20833 from the target architecture and/or options stored during inferior
20836 @item show compile-args
20837 Displays the current state of compilation options override.
20838 This does not show all the options actually used during compilation,
20839 use @ref{set debug compile} for that.
20842 @subsection Caveats when using the @code{compile} command
20844 There are a few caveats to keep in mind when using the @code{compile}
20845 command. As the caveats are different per language, the table below
20846 highlights specific issues on a per language basis.
20849 @item C code examples and caveats
20850 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20851 attempt to compile the source code with a @samp{C} compiler. The source
20852 code provided to the @code{compile} command will have much the same
20853 access to variables and types as it normally would if it were part of
20854 the program currently being debugged in @value{GDBN}.
20856 Below is a sample program that forms the basis of the examples that
20857 follow. This program has been compiled and loaded into @value{GDBN},
20858 much like any other normal debugging session.
20861 void function1 (void)
20864 printf ("function 1\n");
20867 void function2 (void)
20882 For the purposes of the examples in this section, the program above has
20883 been compiled, loaded into @value{GDBN}, stopped at the function
20884 @code{main}, and @value{GDBN} is awaiting input from the user.
20886 To access variables and types for any program in @value{GDBN}, the
20887 program must be compiled and packaged with debug information. The
20888 @code{compile} command is not an exception to this rule. Without debug
20889 information, you can still use the @code{compile} command, but you will
20890 be very limited in what variables and types you can access.
20892 So with that in mind, the example above has been compiled with debug
20893 information enabled. The @code{compile} command will have access to
20894 all variables and types (except those that may have been optimized
20895 out). Currently, as @value{GDBN} has stopped the program in the
20896 @code{main} function, the @code{compile} command would have access to
20897 the variable @code{k}. You could invoke the @code{compile} command
20898 and type some source code to set the value of @code{k}. You can also
20899 read it, or do anything with that variable you would normally do in
20900 @code{C}. Be aware that changes to inferior variables in the
20901 @code{compile} command are persistent. In the following example:
20904 compile code k = 3;
20908 the variable @code{k} is now 3. It will retain that value until
20909 something else in the example program changes it, or another
20910 @code{compile} command changes it.
20912 Normal scope and access rules apply to source code compiled and
20913 injected by the @code{compile} command. In the example, the variables
20914 @code{j} and @code{k} are not accessible yet, because the program is
20915 currently stopped in the @code{main} function, where these variables
20916 are not in scope. Therefore, the following command
20919 compile code j = 3;
20923 will result in a compilation error message.
20925 Once the program is continued, execution will bring these variables in
20926 scope, and they will become accessible; then the code you specify via
20927 the @code{compile} command will be able to access them.
20929 You can create variables and types with the @code{compile} command as
20930 part of your source code. Variables and types that are created as part
20931 of the @code{compile} command are not visible to the rest of the program for
20932 the duration of its run. This example is valid:
20935 compile code int ff = 5; printf ("ff is %d\n", ff);
20938 However, if you were to type the following into @value{GDBN} after that
20939 command has completed:
20942 compile code printf ("ff is %d\n'', ff);
20946 a compiler error would be raised as the variable @code{ff} no longer
20947 exists. Object code generated and injected by the @code{compile}
20948 command is removed when its execution ends. Caution is advised
20949 when assigning to program variables values of variables created by the
20950 code submitted to the @code{compile} command. This example is valid:
20953 compile code int ff = 5; k = ff;
20956 The value of the variable @code{ff} is assigned to @code{k}. The variable
20957 @code{k} does not require the existence of @code{ff} to maintain the value
20958 it has been assigned. However, pointers require particular care in
20959 assignment. If the source code compiled with the @code{compile} command
20960 changed the address of a pointer in the example program, perhaps to a
20961 variable created in the @code{compile} command, that pointer would point
20962 to an invalid location when the command exits. The following example
20963 would likely cause issues with your debugged program:
20966 compile code int ff = 5; p = &ff;
20969 In this example, @code{p} would point to @code{ff} when the
20970 @code{compile} command is executing the source code provided to it.
20971 However, as variables in the (example) program persist with their
20972 assigned values, the variable @code{p} would point to an invalid
20973 location when the command exists. A general rule should be followed
20974 in that you should either assign @code{NULL} to any assigned pointers,
20975 or restore a valid location to the pointer before the command exits.
20977 Similar caution must be exercised with any structs, unions, and typedefs
20978 defined in @code{compile} command. Types defined in the @code{compile}
20979 command will no longer be available in the next @code{compile} command.
20980 Therefore, if you cast a variable to a type defined in the
20981 @code{compile} command, care must be taken to ensure that any future
20982 need to resolve the type can be achieved.
20985 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20986 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20987 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20988 Compilation failed.
20989 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20993 Variables that have been optimized away by the compiler are not
20994 accessible to the code submitted to the @code{compile} command.
20995 Access to those variables will generate a compiler error which @value{GDBN}
20996 will print to the console.
20999 @subsection Compiler search for the @code{compile} command
21001 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
21002 which may not be obvious for remote targets of different architecture
21003 than where @value{GDBN} is running. Environment variable @env{PATH} on
21004 @value{GDBN} host is searched for @value{NGCC} binary matching the
21005 target architecture and operating system. This search can be overriden
21006 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
21007 taken from shell that executed @value{GDBN}, it is not the value set by
21008 @value{GDBN} command @code{set environment}). @xref{Environment}.
21011 Specifically @env{PATH} is searched for binaries matching regular expression
21012 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
21013 debugged. @var{arch} is processor name --- multiarch is supported, so for
21014 example both @code{i386} and @code{x86_64} targets look for pattern
21015 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
21016 for pattern @code{s390x?}. @var{os} is currently supported only for
21017 pattern @code{linux(-gnu)?}.
21019 On Posix hosts the compiler driver @value{GDBN} needs to find also
21020 shared library @file{libcc1.so} from the compiler. It is searched in
21021 default shared library search path (overridable with usual environment
21022 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
21023 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
21024 according to the installation of the found compiler --- as possibly
21025 specified by the @code{set compile-gcc} command.
21028 @item set compile-gcc
21029 @cindex compile command driver filename override
21030 Set compilation command used for compiling and injecting code with the
21031 @code{compile} commands. If this option is not set (it is set to
21032 an empty string), the search described above will occur --- that is the
21035 @item show compile-gcc
21036 Displays the current compile command @value{NGCC} driver filename.
21037 If set, it is the main command @command{gcc}, found usually for example
21038 under name @file{x86_64-linux-gnu-gcc}.
21042 @chapter @value{GDBN} Files
21044 @value{GDBN} needs to know the file name of the program to be debugged,
21045 both in order to read its symbol table and in order to start your
21046 program. To debug a core dump of a previous run, you must also tell
21047 @value{GDBN} the name of the core dump file.
21050 * Files:: Commands to specify files
21051 * File Caching:: Information about @value{GDBN}'s file caching
21052 * Separate Debug Files:: Debugging information in separate files
21053 * MiniDebugInfo:: Debugging information in a special section
21054 * Index Files:: Index files speed up GDB
21055 * Symbol Errors:: Errors reading symbol files
21056 * Data Files:: GDB data files
21060 @section Commands to Specify Files
21062 @cindex symbol table
21063 @cindex core dump file
21065 You may want to specify executable and core dump file names. The usual
21066 way to do this is at start-up time, using the arguments to
21067 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
21068 Out of @value{GDBN}}).
21070 Occasionally it is necessary to change to a different file during a
21071 @value{GDBN} session. Or you may run @value{GDBN} and forget to
21072 specify a file you want to use. Or you are debugging a remote target
21073 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
21074 Program}). In these situations the @value{GDBN} commands to specify
21075 new files are useful.
21078 @cindex executable file
21080 @item file @var{filename}
21081 Use @var{filename} as the program to be debugged. It is read for its
21082 symbols and for the contents of pure memory. It is also the program
21083 executed when you use the @code{run} command. If you do not specify a
21084 directory and the file is not found in the @value{GDBN} working directory,
21085 @value{GDBN} uses the environment variable @env{PATH} as a list of
21086 directories to search, just as the shell does when looking for a program
21087 to run. You can change the value of this variable, for both @value{GDBN}
21088 and your program, using the @code{path} command.
21090 @cindex unlinked object files
21091 @cindex patching object files
21092 You can load unlinked object @file{.o} files into @value{GDBN} using
21093 the @code{file} command. You will not be able to ``run'' an object
21094 file, but you can disassemble functions and inspect variables. Also,
21095 if the underlying BFD functionality supports it, you could use
21096 @kbd{gdb -write} to patch object files using this technique. Note
21097 that @value{GDBN} can neither interpret nor modify relocations in this
21098 case, so branches and some initialized variables will appear to go to
21099 the wrong place. But this feature is still handy from time to time.
21102 @code{file} with no argument makes @value{GDBN} discard any information it
21103 has on both executable file and the symbol table.
21106 @item exec-file @r{[} @var{filename} @r{]}
21107 Specify that the program to be run (but not the symbol table) is found
21108 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
21109 if necessary to locate your program. Omitting @var{filename} means to
21110 discard information on the executable file.
21112 @kindex symbol-file
21113 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
21114 Read symbol table information from file @var{filename}. @env{PATH} is
21115 searched when necessary. Use the @code{file} command to get both symbol
21116 table and program to run from the same file.
21118 If an optional @var{offset} is specified, it is added to the start
21119 address of each section in the symbol file. This is useful if the
21120 program is relocated at runtime, such as the Linux kernel with kASLR
21123 @code{symbol-file} with no argument clears out @value{GDBN} information on your
21124 program's symbol table.
21126 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
21127 some breakpoints and auto-display expressions. This is because they may
21128 contain pointers to the internal data recording symbols and data types,
21129 which are part of the old symbol table data being discarded inside
21132 @code{symbol-file} does not repeat if you press @key{RET} again after
21135 When @value{GDBN} is configured for a particular environment, it
21136 understands debugging information in whatever format is the standard
21137 generated for that environment; you may use either a @sc{gnu} compiler, or
21138 other compilers that adhere to the local conventions.
21139 Best results are usually obtained from @sc{gnu} compilers; for example,
21140 using @code{@value{NGCC}} you can generate debugging information for
21143 For most kinds of object files, with the exception of old SVR3 systems
21144 using COFF, the @code{symbol-file} command does not normally read the
21145 symbol table in full right away. Instead, it scans the symbol table
21146 quickly to find which source files and which symbols are present. The
21147 details are read later, one source file at a time, as they are needed.
21149 The purpose of this two-stage reading strategy is to make @value{GDBN}
21150 start up faster. For the most part, it is invisible except for
21151 occasional pauses while the symbol table details for a particular source
21152 file are being read. (The @code{set verbose} command can turn these
21153 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
21154 Warnings and Messages}.)
21156 We have not implemented the two-stage strategy for COFF yet. When the
21157 symbol table is stored in COFF format, @code{symbol-file} reads the
21158 symbol table data in full right away. Note that ``stabs-in-COFF''
21159 still does the two-stage strategy, since the debug info is actually
21163 @cindex reading symbols immediately
21164 @cindex symbols, reading immediately
21165 @item symbol-file @r{[} -readnow @r{]} @var{filename}
21166 @itemx file @r{[} -readnow @r{]} @var{filename}
21167 You can override the @value{GDBN} two-stage strategy for reading symbol
21168 tables by using the @samp{-readnow} option with any of the commands that
21169 load symbol table information, if you want to be sure @value{GDBN} has the
21170 entire symbol table available.
21172 @cindex @code{-readnever}, option for symbol-file command
21173 @cindex never read symbols
21174 @cindex symbols, never read
21175 @item symbol-file @r{[} -readnever @r{]} @var{filename}
21176 @itemx file @r{[} -readnever @r{]} @var{filename}
21177 You can instruct @value{GDBN} to never read the symbolic information
21178 contained in @var{filename} by using the @samp{-readnever} option.
21179 @xref{--readnever}.
21181 @c FIXME: for now no mention of directories, since this seems to be in
21182 @c flux. 13mar1992 status is that in theory GDB would look either in
21183 @c current dir or in same dir as myprog; but issues like competing
21184 @c GDB's, or clutter in system dirs, mean that in practice right now
21185 @c only current dir is used. FFish says maybe a special GDB hierarchy
21186 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
21190 @item core-file @r{[}@var{filename}@r{]}
21192 Specify the whereabouts of a core dump file to be used as the ``contents
21193 of memory''. Traditionally, core files contain only some parts of the
21194 address space of the process that generated them; @value{GDBN} can access the
21195 executable file itself for other parts.
21197 @code{core-file} with no argument specifies that no core file is
21200 Note that the core file is ignored when your program is actually running
21201 under @value{GDBN}. So, if you have been running your program and you
21202 wish to debug a core file instead, you must kill the subprocess in which
21203 the program is running. To do this, use the @code{kill} command
21204 (@pxref{Kill Process, ,Killing the Child Process}).
21206 @kindex add-symbol-file
21207 @cindex dynamic linking
21208 @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{]}
21209 The @code{add-symbol-file} command reads additional symbol table
21210 information from the file @var{filename}. You would use this command
21211 when @var{filename} has been dynamically loaded (by some other means)
21212 into the program that is running. The @var{textaddress} parameter gives
21213 the memory address at which the file's text section has been loaded.
21214 You can additionally specify the base address of other sections using
21215 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
21216 If a section is omitted, @value{GDBN} will use its default addresses
21217 as found in @var{filename}. Any @var{address} or @var{textaddress}
21218 can be given as an expression.
21220 If an optional @var{offset} is specified, it is added to the start
21221 address of each section, except those for which the address was
21222 specified explicitly.
21224 The symbol table of the file @var{filename} is added to the symbol table
21225 originally read with the @code{symbol-file} command. You can use the
21226 @code{add-symbol-file} command any number of times; the new symbol data
21227 thus read is kept in addition to the old.
21229 Changes can be reverted using the command @code{remove-symbol-file}.
21231 @cindex relocatable object files, reading symbols from
21232 @cindex object files, relocatable, reading symbols from
21233 @cindex reading symbols from relocatable object files
21234 @cindex symbols, reading from relocatable object files
21235 @cindex @file{.o} files, reading symbols from
21236 Although @var{filename} is typically a shared library file, an
21237 executable file, or some other object file which has been fully
21238 relocated for loading into a process, you can also load symbolic
21239 information from relocatable @file{.o} files, as long as:
21243 the file's symbolic information refers only to linker symbols defined in
21244 that file, not to symbols defined by other object files,
21246 every section the file's symbolic information refers to has actually
21247 been loaded into the inferior, as it appears in the file, and
21249 you can determine the address at which every section was loaded, and
21250 provide these to the @code{add-symbol-file} command.
21254 Some embedded operating systems, like Sun Chorus and VxWorks, can load
21255 relocatable files into an already running program; such systems
21256 typically make the requirements above easy to meet. However, it's
21257 important to recognize that many native systems use complex link
21258 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
21259 assembly, for example) that make the requirements difficult to meet. In
21260 general, one cannot assume that using @code{add-symbol-file} to read a
21261 relocatable object file's symbolic information will have the same effect
21262 as linking the relocatable object file into the program in the normal
21265 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
21267 @kindex remove-symbol-file
21268 @item remove-symbol-file @var{filename}
21269 @item remove-symbol-file -a @var{address}
21270 Remove a symbol file added via the @code{add-symbol-file} command. The
21271 file to remove can be identified by its @var{filename} or by an @var{address}
21272 that lies within the boundaries of this symbol file in memory. Example:
21275 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
21276 add symbol table from file "/home/user/gdb/mylib.so" at
21277 .text_addr = 0x7ffff7ff9480
21279 Reading symbols from /home/user/gdb/mylib.so...
21280 (gdb) remove-symbol-file -a 0x7ffff7ff9480
21281 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
21286 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
21288 @kindex add-symbol-file-from-memory
21289 @cindex @code{syscall DSO}
21290 @cindex load symbols from memory
21291 @item add-symbol-file-from-memory @var{address}
21292 Load symbols from the given @var{address} in a dynamically loaded
21293 object file whose image is mapped directly into the inferior's memory.
21294 For example, the Linux kernel maps a @code{syscall DSO} into each
21295 process's address space; this DSO provides kernel-specific code for
21296 some system calls. The argument can be any expression whose
21297 evaluation yields the address of the file's shared object file header.
21298 For this command to work, you must have used @code{symbol-file} or
21299 @code{exec-file} commands in advance.
21302 @item section @var{section} @var{addr}
21303 The @code{section} command changes the base address of the named
21304 @var{section} of the exec file to @var{addr}. This can be used if the
21305 exec file does not contain section addresses, (such as in the
21306 @code{a.out} format), or when the addresses specified in the file
21307 itself are wrong. Each section must be changed separately. The
21308 @code{info files} command, described below, lists all the sections and
21312 @kindex info target
21315 @code{info files} and @code{info target} are synonymous; both print the
21316 current target (@pxref{Targets, ,Specifying a Debugging Target}),
21317 including the names of the executable and core dump files currently in
21318 use by @value{GDBN}, and the files from which symbols were loaded. The
21319 command @code{help target} lists all possible targets rather than
21322 @kindex maint info sections
21323 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21324 Another command that can give you extra information about program sections
21325 is @code{maint info sections}. In addition to the section information
21326 displayed by @code{info files}, this command displays the flags and file
21327 offset of each section in the executable and core dump files.
21329 When @samp{-all-objects} is passed then sections from all loaded object
21330 files, including shared libraries, are printed.
21332 The optional @var{filter-list} is a space separated list of filter
21333 keywords. Sections that match any one of the filter criteria will be
21334 printed. There are two types of filter:
21337 @item @var{section-name}
21338 Display information about any section named @var{section-name}.
21339 @item @var{section-flag}
21340 Display information for any section with @var{section-flag}. The
21341 section flags that @value{GDBN} currently knows about are:
21344 Section will have space allocated in the process when loaded.
21345 Set for all sections except those containing debug information.
21347 Section will be loaded from the file into the child process memory.
21348 Set for pre-initialized code and data, clear for @code{.bss} sections.
21350 Section needs to be relocated before loading.
21352 Section cannot be modified by the child process.
21354 Section contains executable code only.
21356 Section contains data only (no executable code).
21358 Section will reside in ROM.
21360 Section contains data for constructor/destructor lists.
21362 Section is not empty.
21364 An instruction to the linker to not output the section.
21365 @item COFF_SHARED_LIBRARY
21366 A notification to the linker that the section contains
21367 COFF shared library information.
21369 Section contains common symbols.
21373 @kindex maint info target-sections
21374 @item maint info target-sections
21375 This command prints @value{GDBN}'s internal section table. For each
21376 target @value{GDBN} maintains a table containing the allocatable
21377 sections from all currently mapped objects, along with information
21378 about where the section is mapped.
21380 @kindex set trust-readonly-sections
21381 @cindex read-only sections
21382 @item set trust-readonly-sections on
21383 Tell @value{GDBN} that readonly sections in your object file
21384 really are read-only (i.e.@: that their contents will not change).
21385 In that case, @value{GDBN} can fetch values from these sections
21386 out of the object file, rather than from the target program.
21387 For some targets (notably embedded ones), this can be a significant
21388 enhancement to debugging performance.
21390 The default is off.
21392 @item set trust-readonly-sections off
21393 Tell @value{GDBN} not to trust readonly sections. This means that
21394 the contents of the section might change while the program is running,
21395 and must therefore be fetched from the target when needed.
21397 @item show trust-readonly-sections
21398 Show the current setting of trusting readonly sections.
21401 All file-specifying commands allow both absolute and relative file names
21402 as arguments. @value{GDBN} always converts the file name to an absolute file
21403 name and remembers it that way.
21405 @cindex shared libraries
21406 @anchor{Shared Libraries}
21407 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21408 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21409 DSBT (TIC6X) shared libraries.
21411 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21412 shared libraries. @xref{Expat}.
21414 @value{GDBN} automatically loads symbol definitions from shared libraries
21415 when you use the @code{run} command, or when you examine a core file.
21416 (Before you issue the @code{run} command, @value{GDBN} does not understand
21417 references to a function in a shared library, however---unless you are
21418 debugging a core file).
21420 @c FIXME: some @value{GDBN} release may permit some refs to undef
21421 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21422 @c FIXME...lib; check this from time to time when updating manual
21424 There are times, however, when you may wish to not automatically load
21425 symbol definitions from shared libraries, such as when they are
21426 particularly large or there are many of them.
21428 To control the automatic loading of shared library symbols, use the
21432 @kindex set auto-solib-add
21433 @item set auto-solib-add @var{mode}
21434 If @var{mode} is @code{on}, symbols from all shared object libraries
21435 will be loaded automatically when the inferior begins execution, you
21436 attach to an independently started inferior, or when the dynamic linker
21437 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21438 is @code{off}, symbols must be loaded manually, using the
21439 @code{sharedlibrary} command. The default value is @code{on}.
21441 @cindex memory used for symbol tables
21442 If your program uses lots of shared libraries with debug info that
21443 takes large amounts of memory, you can decrease the @value{GDBN}
21444 memory footprint by preventing it from automatically loading the
21445 symbols from shared libraries. To that end, type @kbd{set
21446 auto-solib-add off} before running the inferior, then load each
21447 library whose debug symbols you do need with @kbd{sharedlibrary
21448 @var{regexp}}, where @var{regexp} is a regular expression that matches
21449 the libraries whose symbols you want to be loaded.
21451 @kindex show auto-solib-add
21452 @item show auto-solib-add
21453 Display the current autoloading mode.
21456 @cindex load shared library
21457 To explicitly load shared library symbols, use the @code{sharedlibrary}
21461 @kindex info sharedlibrary
21463 @item info share @var{regex}
21464 @itemx info sharedlibrary @var{regex}
21465 Print the names of the shared libraries which are currently loaded
21466 that match @var{regex}. If @var{regex} is omitted then print
21467 all shared libraries that are loaded.
21470 @item info dll @var{regex}
21471 This is an alias of @code{info sharedlibrary}.
21473 @kindex sharedlibrary
21475 @item sharedlibrary @var{regex}
21476 @itemx share @var{regex}
21477 Load shared object library symbols for files matching a
21478 Unix regular expression.
21479 As with files loaded automatically, it only loads shared libraries
21480 required by your program for a core file or after typing @code{run}. If
21481 @var{regex} is omitted all shared libraries required by your program are
21484 @item nosharedlibrary
21485 @kindex nosharedlibrary
21486 @cindex unload symbols from shared libraries
21487 Unload all shared object library symbols. This discards all symbols
21488 that have been loaded from all shared libraries. Symbols from shared
21489 libraries that were loaded by explicit user requests are not
21493 Sometimes you may wish that @value{GDBN} stops and gives you control
21494 when any of shared library events happen. The best way to do this is
21495 to use @code{catch load} and @code{catch unload} (@pxref{Set
21498 @value{GDBN} also supports the @code{set stop-on-solib-events}
21499 command for this. This command exists for historical reasons. It is
21500 less useful than setting a catchpoint, because it does not allow for
21501 conditions or commands as a catchpoint does.
21504 @item set stop-on-solib-events
21505 @kindex set stop-on-solib-events
21506 This command controls whether @value{GDBN} should give you control
21507 when the dynamic linker notifies it about some shared library event.
21508 The most common event of interest is loading or unloading of a new
21511 @item show stop-on-solib-events
21512 @kindex show stop-on-solib-events
21513 Show whether @value{GDBN} stops and gives you control when shared
21514 library events happen.
21517 Shared libraries are also supported in many cross or remote debugging
21518 configurations. @value{GDBN} needs to have access to the target's libraries;
21519 this can be accomplished either by providing copies of the libraries
21520 on the host system, or by asking @value{GDBN} to automatically retrieve the
21521 libraries from the target. If copies of the target libraries are
21522 provided, they need to be the same as the target libraries, although the
21523 copies on the target can be stripped as long as the copies on the host are
21526 @cindex where to look for shared libraries
21527 For remote debugging, you need to tell @value{GDBN} where the target
21528 libraries are, so that it can load the correct copies---otherwise, it
21529 may try to load the host's libraries. @value{GDBN} has two variables
21530 to specify the search directories for target libraries.
21533 @cindex prefix for executable and shared library file names
21534 @cindex system root, alternate
21535 @kindex set solib-absolute-prefix
21536 @kindex set sysroot
21537 @item set sysroot @var{path}
21538 Use @var{path} as the system root for the program being debugged. Any
21539 absolute shared library paths will be prefixed with @var{path}; many
21540 runtime loaders store the absolute paths to the shared library in the
21541 target program's memory. When starting processes remotely, and when
21542 attaching to already-running processes (local or remote), their
21543 executable filenames will be prefixed with @var{path} if reported to
21544 @value{GDBN} as absolute by the operating system. If you use
21545 @code{set sysroot} to find executables and shared libraries, they need
21546 to be laid out in the same way that they are on the target, with
21547 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21550 If @var{path} starts with the sequence @file{target:} and the target
21551 system is remote then @value{GDBN} will retrieve the target binaries
21552 from the remote system. This is only supported when using a remote
21553 target that supports the @code{remote get} command (@pxref{File
21554 Transfer,,Sending files to a remote system}). The part of @var{path}
21555 following the initial @file{target:} (if present) is used as system
21556 root prefix on the remote file system. If @var{path} starts with the
21557 sequence @file{remote:} this is converted to the sequence
21558 @file{target:} by @code{set sysroot}@footnote{Historically the
21559 functionality to retrieve binaries from the remote system was
21560 provided by prefixing @var{path} with @file{remote:}}. If you want
21561 to specify a local system root using a directory that happens to be
21562 named @file{target:} or @file{remote:}, you need to use some
21563 equivalent variant of the name like @file{./target:}.
21565 For targets with an MS-DOS based filesystem, such as MS-Windows,
21566 @value{GDBN} tries prefixing a few variants of the target
21567 absolute file name with @var{path}. But first, on Unix hosts,
21568 @value{GDBN} converts all backslash directory separators into forward
21569 slashes, because the backslash is not a directory separator on Unix:
21572 c:\foo\bar.dll @result{} c:/foo/bar.dll
21575 Then, @value{GDBN} attempts prefixing the target file name with
21576 @var{path}, and looks for the resulting file name in the host file
21580 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21583 If that does not find the binary, @value{GDBN} tries removing
21584 the @samp{:} character from the drive spec, both for convenience, and,
21585 for the case of the host file system not supporting file names with
21589 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21592 This makes it possible to have a system root that mirrors a target
21593 with more than one drive. E.g., you may want to setup your local
21594 copies of the target system shared libraries like so (note @samp{c} vs
21598 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21599 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21600 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21604 and point the system root at @file{/path/to/sysroot}, so that
21605 @value{GDBN} can find the correct copies of both
21606 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21608 If that still does not find the binary, @value{GDBN} tries
21609 removing the whole drive spec from the target file name:
21612 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21615 This last lookup makes it possible to not care about the drive name,
21616 if you don't want or need to.
21618 The @code{set solib-absolute-prefix} command is an alias for @code{set
21621 @cindex default system root
21622 @cindex @samp{--with-sysroot}
21623 You can set the default system root by using the configure-time
21624 @samp{--with-sysroot} option. If the system root is inside
21625 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21626 @samp{--exec-prefix}), then the default system root will be updated
21627 automatically if the installed @value{GDBN} is moved to a new
21630 @kindex show sysroot
21632 Display the current executable and shared library prefix.
21634 @kindex set solib-search-path
21635 @item set solib-search-path @var{path}
21636 If this variable is set, @var{path} is a colon-separated list of
21637 directories to search for shared libraries. @samp{solib-search-path}
21638 is used after @samp{sysroot} fails to locate the library, or if the
21639 path to the library is relative instead of absolute. If you want to
21640 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21641 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21642 finding your host's libraries. @samp{sysroot} is preferred; setting
21643 it to a nonexistent directory may interfere with automatic loading
21644 of shared library symbols.
21646 @kindex show solib-search-path
21647 @item show solib-search-path
21648 Display the current shared library search path.
21650 @cindex DOS file-name semantics of file names.
21651 @kindex set target-file-system-kind (unix|dos-based|auto)
21652 @kindex show target-file-system-kind
21653 @item set target-file-system-kind @var{kind}
21654 Set assumed file system kind for target reported file names.
21656 Shared library file names as reported by the target system may not
21657 make sense as is on the system @value{GDBN} is running on. For
21658 example, when remote debugging a target that has MS-DOS based file
21659 system semantics, from a Unix host, the target may be reporting to
21660 @value{GDBN} a list of loaded shared libraries with file names such as
21661 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21662 drive letters, so the @samp{c:\} prefix is not normally understood as
21663 indicating an absolute file name, and neither is the backslash
21664 normally considered a directory separator character. In that case,
21665 the native file system would interpret this whole absolute file name
21666 as a relative file name with no directory components. This would make
21667 it impossible to point @value{GDBN} at a copy of the remote target's
21668 shared libraries on the host using @code{set sysroot}, and impractical
21669 with @code{set solib-search-path}. Setting
21670 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21671 to interpret such file names similarly to how the target would, and to
21672 map them to file names valid on @value{GDBN}'s native file system
21673 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21674 to one of the supported file system kinds. In that case, @value{GDBN}
21675 tries to determine the appropriate file system variant based on the
21676 current target's operating system (@pxref{ABI, ,Configuring the
21677 Current ABI}). The supported file system settings are:
21681 Instruct @value{GDBN} to assume the target file system is of Unix
21682 kind. Only file names starting the forward slash (@samp{/}) character
21683 are considered absolute, and the directory separator character is also
21687 Instruct @value{GDBN} to assume the target file system is DOS based.
21688 File names starting with either a forward slash, or a drive letter
21689 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21690 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21691 considered directory separators.
21694 Instruct @value{GDBN} to use the file system kind associated with the
21695 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21696 This is the default.
21700 @cindex file name canonicalization
21701 @cindex base name differences
21702 When processing file names provided by the user, @value{GDBN}
21703 frequently needs to compare them to the file names recorded in the
21704 program's debug info. Normally, @value{GDBN} compares just the
21705 @dfn{base names} of the files as strings, which is reasonably fast
21706 even for very large programs. (The base name of a file is the last
21707 portion of its name, after stripping all the leading directories.)
21708 This shortcut in comparison is based upon the assumption that files
21709 cannot have more than one base name. This is usually true, but
21710 references to files that use symlinks or similar filesystem
21711 facilities violate that assumption. If your program records files
21712 using such facilities, or if you provide file names to @value{GDBN}
21713 using symlinks etc., you can set @code{basenames-may-differ} to
21714 @code{true} to instruct @value{GDBN} to completely canonicalize each
21715 pair of file names it needs to compare. This will make file-name
21716 comparisons accurate, but at a price of a significant slowdown.
21719 @item set basenames-may-differ
21720 @kindex set basenames-may-differ
21721 Set whether a source file may have multiple base names.
21723 @item show basenames-may-differ
21724 @kindex show basenames-may-differ
21725 Show whether a source file may have multiple base names.
21729 @section File Caching
21730 @cindex caching of opened files
21731 @cindex caching of bfd objects
21733 To speed up file loading, and reduce memory usage, @value{GDBN} will
21734 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21735 BFD, bfd, The Binary File Descriptor Library}. The following commands
21736 allow visibility and control of the caching behavior.
21739 @kindex maint info bfds
21740 @item maint info bfds
21741 This prints information about each @code{bfd} object that is known to
21744 @kindex maint set bfd-sharing
21745 @kindex maint show bfd-sharing
21746 @kindex bfd caching
21747 @item maint set bfd-sharing
21748 @item maint show bfd-sharing
21749 Control whether @code{bfd} objects can be shared. When sharing is
21750 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21751 than reopening the same file. Turning sharing off does not cause
21752 already shared @code{bfd} objects to be unshared, but all future files
21753 that are opened will create a new @code{bfd} object. Similarly,
21754 re-enabling sharing does not cause multiple existing @code{bfd}
21755 objects to be collapsed into a single shared @code{bfd} object.
21757 @kindex set debug bfd-cache @var{level}
21758 @kindex bfd caching
21759 @item set debug bfd-cache @var{level}
21760 Turns on debugging of the bfd cache, setting the level to @var{level}.
21762 @kindex show debug bfd-cache
21763 @kindex bfd caching
21764 @item show debug bfd-cache
21765 Show the current debugging level of the bfd cache.
21768 @node Separate Debug Files
21769 @section Debugging Information in Separate Files
21770 @cindex separate debugging information files
21771 @cindex debugging information in separate files
21772 @cindex @file{.debug} subdirectories
21773 @cindex debugging information directory, global
21774 @cindex global debugging information directories
21775 @cindex build ID, and separate debugging files
21776 @cindex @file{.build-id} directory
21778 @value{GDBN} allows you to put a program's debugging information in a
21779 file separate from the executable itself, in a way that allows
21780 @value{GDBN} to find and load the debugging information automatically.
21781 Since debugging information can be very large---sometimes larger
21782 than the executable code itself---some systems distribute debugging
21783 information for their executables in separate files, which users can
21784 install only when they need to debug a problem.
21786 @value{GDBN} supports two ways of specifying the separate debug info
21791 The executable contains a @dfn{debug link} that specifies the name of
21792 the separate debug info file. The separate debug file's name is
21793 usually @file{@var{executable}.debug}, where @var{executable} is the
21794 name of the corresponding executable file without leading directories
21795 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21796 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21797 checksum for the debug file, which @value{GDBN} uses to validate that
21798 the executable and the debug file came from the same build.
21802 The executable contains a @dfn{build ID}, a unique bit string that is
21803 also present in the corresponding debug info file. (This is supported
21804 only on some operating systems, when using the ELF or PE file formats
21805 for binary files and the @sc{gnu} Binutils.) For more details about
21806 this feature, see the description of the @option{--build-id}
21807 command-line option in @ref{Options, , Command Line Options, ld,
21808 The GNU Linker}. The debug info file's name is not specified
21809 explicitly by the build ID, but can be computed from the build ID, see
21813 Depending on the way the debug info file is specified, @value{GDBN}
21814 uses two different methods of looking for the debug file:
21818 For the ``debug link'' method, @value{GDBN} looks up the named file in
21819 the directory of the executable file, then in a subdirectory of that
21820 directory named @file{.debug}, and finally under each one of the
21821 global debug directories, in a subdirectory whose name is identical to
21822 the leading directories of the executable's absolute file name. (On
21823 MS-Windows/MS-DOS, the drive letter of the executable's leading
21824 directories is converted to a one-letter subdirectory, i.e.@:
21825 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21826 filesystems disallow colons in file names.)
21829 For the ``build ID'' method, @value{GDBN} looks in the
21830 @file{.build-id} subdirectory of each one of the global debug directories for
21831 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21832 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21833 are the rest of the bit string. (Real build ID strings are 32 or more
21834 hex characters, not 10.) @value{GDBN} can automatically query
21835 @code{debuginfod} servers using build IDs in order to download separate debug
21836 files that cannot be found locally. For more information see @ref{Debuginfod}.
21839 So, for example, suppose you ask @value{GDBN} to debug
21840 @file{/usr/bin/ls}, which has a debug link that specifies the
21841 file @file{ls.debug}, and a build ID whose value in hex is
21842 @code{abcdef1234}. If the list of the global debug directories includes
21843 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21844 debug information files, in the indicated order:
21848 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21850 @file{/usr/bin/ls.debug}
21852 @file{/usr/bin/.debug/ls.debug}
21854 @file{/usr/lib/debug/usr/bin/ls.debug}.
21857 If the debug file still has not been found and @code{debuginfod}
21858 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
21859 file from @code{debuginfod} servers.
21861 @anchor{debug-file-directory}
21862 Global debugging info directories default to what is set by @value{GDBN}
21863 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21864 you can also set the global debugging info directories, and view the list
21865 @value{GDBN} is currently using.
21869 @kindex set debug-file-directory
21870 @item set debug-file-directory @var{directories}
21871 Set the directories which @value{GDBN} searches for separate debugging
21872 information files to @var{directory}. Multiple path components can be set
21873 concatenating them by a path separator.
21875 @kindex show debug-file-directory
21876 @item show debug-file-directory
21877 Show the directories @value{GDBN} searches for separate debugging
21882 @cindex @code{.gnu_debuglink} sections
21883 @cindex debug link sections
21884 A debug link is a special section of the executable file named
21885 @code{.gnu_debuglink}. The section must contain:
21889 A filename, with any leading directory components removed, followed by
21892 zero to three bytes of padding, as needed to reach the next four-byte
21893 boundary within the section, and
21895 a four-byte CRC checksum, stored in the same endianness used for the
21896 executable file itself. The checksum is computed on the debugging
21897 information file's full contents by the function given below, passing
21898 zero as the @var{crc} argument.
21901 Any executable file format can carry a debug link, as long as it can
21902 contain a section named @code{.gnu_debuglink} with the contents
21905 @cindex @code{.note.gnu.build-id} sections
21906 @cindex build ID sections
21907 The build ID is a special section in the executable file (and in other
21908 ELF binary files that @value{GDBN} may consider). This section is
21909 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21910 It contains unique identification for the built files---the ID remains
21911 the same across multiple builds of the same build tree. The default
21912 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21913 content for the build ID string. The same section with an identical
21914 value is present in the original built binary with symbols, in its
21915 stripped variant, and in the separate debugging information file.
21917 The debugging information file itself should be an ordinary
21918 executable, containing a full set of linker symbols, sections, and
21919 debugging information. The sections of the debugging information file
21920 should have the same names, addresses, and sizes as the original file,
21921 but they need not contain any data---much like a @code{.bss} section
21922 in an ordinary executable.
21924 The @sc{gnu} binary utilities (Binutils) package includes the
21925 @samp{objcopy} utility that can produce
21926 the separated executable / debugging information file pairs using the
21927 following commands:
21930 @kbd{objcopy --only-keep-debug foo foo.debug}
21935 These commands remove the debugging
21936 information from the executable file @file{foo} and place it in the file
21937 @file{foo.debug}. You can use the first, second or both methods to link the
21942 The debug link method needs the following additional command to also leave
21943 behind a debug link in @file{foo}:
21946 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21949 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21950 a version of the @code{strip} command such that the command @kbd{strip foo -f
21951 foo.debug} has the same functionality as the two @code{objcopy} commands and
21952 the @code{ln -s} command above, together.
21955 Build ID gets embedded into the main executable using @code{ld --build-id} or
21956 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21957 compatibility fixes for debug files separation are present in @sc{gnu} binary
21958 utilities (Binutils) package since version 2.18.
21963 @cindex CRC algorithm definition
21964 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21965 IEEE 802.3 using the polynomial:
21967 @c TexInfo requires naked braces for multi-digit exponents for Tex
21968 @c output, but this causes HTML output to barf. HTML has to be set using
21969 @c raw commands. So we end up having to specify this equation in 2
21974 <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>
21975 + <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
21981 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21982 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21986 The function is computed byte at a time, taking the least
21987 significant bit of each byte first. The initial pattern
21988 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21989 the final result is inverted to ensure trailing zeros also affect the
21992 @emph{Note:} This is the same CRC polynomial as used in handling the
21993 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21994 However in the case of the Remote Serial Protocol, the CRC is computed
21995 @emph{most} significant bit first, and the result is not inverted, so
21996 trailing zeros have no effect on the CRC value.
21998 To complete the description, we show below the code of the function
21999 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
22000 initially supplied @code{crc} argument means that an initial call to
22001 this function passing in zero will start computing the CRC using
22004 @kindex gnu_debuglink_crc32
22007 gnu_debuglink_crc32 (unsigned long crc,
22008 unsigned char *buf, size_t len)
22010 static const unsigned long crc32_table[256] =
22012 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
22013 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
22014 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
22015 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
22016 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
22017 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
22018 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
22019 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
22020 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
22021 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
22022 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
22023 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
22024 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
22025 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
22026 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
22027 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
22028 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
22029 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
22030 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
22031 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
22032 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
22033 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
22034 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
22035 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
22036 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
22037 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
22038 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
22039 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
22040 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
22041 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
22042 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
22043 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
22044 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
22045 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
22046 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
22047 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
22048 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
22049 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
22050 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
22051 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
22052 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
22053 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
22054 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
22055 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
22056 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
22057 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
22058 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
22059 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
22060 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
22061 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
22062 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
22065 unsigned char *end;
22067 crc = ~crc & 0xffffffff;
22068 for (end = buf + len; buf < end; ++buf)
22069 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
22070 return ~crc & 0xffffffff;
22075 This computation does not apply to the ``build ID'' method.
22077 @node MiniDebugInfo
22078 @section Debugging information in a special section
22079 @cindex separate debug sections
22080 @cindex @samp{.gnu_debugdata} section
22082 Some systems ship pre-built executables and libraries that have a
22083 special @samp{.gnu_debugdata} section. This feature is called
22084 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
22085 is used to supply extra symbols for backtraces.
22087 The intent of this section is to provide extra minimal debugging
22088 information for use in simple backtraces. It is not intended to be a
22089 replacement for full separate debugging information (@pxref{Separate
22090 Debug Files}). The example below shows the intended use; however,
22091 @value{GDBN} does not currently put restrictions on what sort of
22092 debugging information might be included in the section.
22094 @value{GDBN} has support for this extension. If the section exists,
22095 then it is used provided that no other source of debugging information
22096 can be found, and that @value{GDBN} was configured with LZMA support.
22098 This section can be easily created using @command{objcopy} and other
22099 standard utilities:
22102 # Extract the dynamic symbols from the main binary, there is no need
22103 # to also have these in the normal symbol table.
22104 nm -D @var{binary} --format=posix --defined-only \
22105 | awk '@{ print $1 @}' | sort > dynsyms
22107 # Extract all the text (i.e. function) symbols from the debuginfo.
22108 # (Note that we actually also accept "D" symbols, for the benefit
22109 # of platforms like PowerPC64 that use function descriptors.)
22110 nm @var{binary} --format=posix --defined-only \
22111 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
22114 # Keep all the function symbols not already in the dynamic symbol
22116 comm -13 dynsyms funcsyms > keep_symbols
22118 # Separate full debug info into debug binary.
22119 objcopy --only-keep-debug @var{binary} debug
22121 # Copy the full debuginfo, keeping only a minimal set of symbols and
22122 # removing some unnecessary sections.
22123 objcopy -S --remove-section .gdb_index --remove-section .comment \
22124 --keep-symbols=keep_symbols debug mini_debuginfo
22126 # Drop the full debug info from the original binary.
22127 strip --strip-all -R .comment @var{binary}
22129 # Inject the compressed data into the .gnu_debugdata section of the
22132 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
22136 @section Index Files Speed Up @value{GDBN}
22137 @cindex index files
22138 @cindex @samp{.gdb_index} section
22140 When @value{GDBN} finds a symbol file, it scans the symbols in the
22141 file in order to construct an internal symbol table. This lets most
22142 @value{GDBN} operations work quickly---at the cost of a delay early
22143 on. For large programs, this delay can be quite lengthy, so
22144 @value{GDBN} provides a way to build an index, which speeds up
22147 For convenience, @value{GDBN} comes with a program,
22148 @command{gdb-add-index}, which can be used to add the index to a
22149 symbol file. It takes the symbol file as its only argument:
22152 $ gdb-add-index symfile
22155 @xref{gdb-add-index}.
22157 It is also possible to do the work manually. Here is what
22158 @command{gdb-add-index} does behind the curtains.
22160 The index is stored as a section in the symbol file. @value{GDBN} can
22161 write the index to a file, then you can put it into the symbol file
22162 using @command{objcopy}.
22164 To create an index file, use the @code{save gdb-index} command:
22167 @item save gdb-index [-dwarf-5] @var{directory}
22168 @kindex save gdb-index
22169 Create index files for all symbol files currently known by
22170 @value{GDBN}. For each known @var{symbol-file}, this command by
22171 default creates it produces a single file
22172 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
22173 the @option{-dwarf-5} option, it produces 2 files:
22174 @file{@var{symbol-file}.debug_names} and
22175 @file{@var{symbol-file}.debug_str}. The files are created in the
22176 given @var{directory}.
22179 Once you have created an index file you can merge it into your symbol
22180 file, here named @file{symfile}, using @command{objcopy}:
22183 $ objcopy --add-section .gdb_index=symfile.gdb-index \
22184 --set-section-flags .gdb_index=readonly symfile symfile
22187 Or for @code{-dwarf-5}:
22190 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
22191 $ cat symfile.debug_str >>symfile.debug_str.new
22192 $ objcopy --add-section .debug_names=symfile.gdb-index \
22193 --set-section-flags .debug_names=readonly \
22194 --update-section .debug_str=symfile.debug_str.new symfile symfile
22197 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
22198 sections that have been deprecated. Usually they are deprecated because
22199 they are missing a new feature or have performance issues.
22200 To tell @value{GDBN} to use a deprecated index section anyway
22201 specify @code{set use-deprecated-index-sections on}.
22202 The default is @code{off}.
22203 This can speed up startup, but may result in some functionality being lost.
22204 @xref{Index Section Format}.
22206 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
22207 must be done before gdb reads the file. The following will not work:
22210 $ gdb -ex "set use-deprecated-index-sections on" <program>
22213 Instead you must do, for example,
22216 $ gdb -iex "set use-deprecated-index-sections on" <program>
22219 Indices only work when using DWARF debugging information, not stabs.
22221 @subsection Automatic symbol index cache
22223 @cindex automatic symbol index cache
22224 It is possible for @value{GDBN} to automatically save a copy of this index in a
22225 cache on disk and retrieve it from there when loading the same binary in the
22226 future. This feature can be turned on with @kbd{set index-cache enabled on}.
22227 The following commands can be used to tweak the behavior of the index cache.
22231 @kindex set index-cache
22232 @item set index-cache enabled on
22233 @itemx set index-cache enabled off
22234 Enable or disable the use of the symbol index cache.
22236 @item set index-cache directory @var{directory}
22237 @kindex show index-cache
22238 @itemx show index-cache directory
22239 Set/show the directory where index files will be saved.
22241 The default value for this directory depends on the host platform. On
22242 most systems, the index is cached in the @file{gdb} subdirectory of
22243 the directory pointed to by the @env{XDG_CACHE_HOME} environment
22244 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
22245 of your home directory. However, on some systems, the default may
22246 differ according to local convention.
22248 There is no limit on the disk space used by index cache. It is perfectly safe
22249 to delete the content of that directory to free up disk space.
22251 @item show index-cache stats
22252 Print the number of cache hits and misses since the launch of @value{GDBN}.
22256 @node Symbol Errors
22257 @section Errors Reading Symbol Files
22259 While reading a symbol file, @value{GDBN} occasionally encounters problems,
22260 such as symbol types it does not recognize, or known bugs in compiler
22261 output. By default, @value{GDBN} does not notify you of such problems, since
22262 they are relatively common and primarily of interest to people
22263 debugging compilers. If you are interested in seeing information
22264 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
22265 only one message about each such type of problem, no matter how many
22266 times the problem occurs; or you can ask @value{GDBN} to print more messages,
22267 to see how many times the problems occur, with the @code{set
22268 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
22271 The messages currently printed, and their meanings, include:
22274 @item inner block not inside outer block in @var{symbol}
22276 The symbol information shows where symbol scopes begin and end
22277 (such as at the start of a function or a block of statements). This
22278 error indicates that an inner scope block is not fully contained
22279 in its outer scope blocks.
22281 @value{GDBN} circumvents the problem by treating the inner block as if it had
22282 the same scope as the outer block. In the error message, @var{symbol}
22283 may be shown as ``@code{(don't know)}'' if the outer block is not a
22286 @item block at @var{address} out of order
22288 The symbol information for symbol scope blocks should occur in
22289 order of increasing addresses. This error indicates that it does not
22292 @value{GDBN} does not circumvent this problem, and has trouble
22293 locating symbols in the source file whose symbols it is reading. (You
22294 can often determine what source file is affected by specifying
22295 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
22298 @item bad block start address patched
22300 The symbol information for a symbol scope block has a start address
22301 smaller than the address of the preceding source line. This is known
22302 to occur in the SunOS 4.1.1 (and earlier) C compiler.
22304 @value{GDBN} circumvents the problem by treating the symbol scope block as
22305 starting on the previous source line.
22307 @item bad string table offset in symbol @var{n}
22310 Symbol number @var{n} contains a pointer into the string table which is
22311 larger than the size of the string table.
22313 @value{GDBN} circumvents the problem by considering the symbol to have the
22314 name @code{foo}, which may cause other problems if many symbols end up
22317 @item unknown symbol type @code{0x@var{nn}}
22319 The symbol information contains new data types that @value{GDBN} does
22320 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
22321 uncomprehended information, in hexadecimal.
22323 @value{GDBN} circumvents the error by ignoring this symbol information.
22324 This usually allows you to debug your program, though certain symbols
22325 are not accessible. If you encounter such a problem and feel like
22326 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22327 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22328 and examine @code{*bufp} to see the symbol.
22330 @item stub type has NULL name
22332 @value{GDBN} could not find the full definition for a struct or class.
22334 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22335 The symbol information for a C@t{++} member function is missing some
22336 information that recent versions of the compiler should have output for
22339 @item info mismatch between compiler and debugger
22341 @value{GDBN} could not parse a type specification output by the compiler.
22346 @section GDB Data Files
22348 @cindex prefix for data files
22349 @value{GDBN} will sometimes read an auxiliary data file. These files
22350 are kept in a directory known as the @dfn{data directory}.
22352 You can set the data directory's name, and view the name @value{GDBN}
22353 is currently using.
22356 @kindex set data-directory
22357 @item set data-directory @var{directory}
22358 Set the directory which @value{GDBN} searches for auxiliary data files
22359 to @var{directory}.
22361 @kindex show data-directory
22362 @item show data-directory
22363 Show the directory @value{GDBN} searches for auxiliary data files.
22366 @cindex default data directory
22367 @cindex @samp{--with-gdb-datadir}
22368 You can set the default data directory by using the configure-time
22369 @samp{--with-gdb-datadir} option. If the data directory is inside
22370 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22371 @samp{--exec-prefix}), then the default data directory will be updated
22372 automatically if the installed @value{GDBN} is moved to a new
22375 The data directory may also be specified with the
22376 @code{--data-directory} command line option.
22377 @xref{Mode Options}.
22380 @chapter Specifying a Debugging Target
22382 @cindex debugging target
22383 A @dfn{target} is the execution environment occupied by your program.
22385 Often, @value{GDBN} runs in the same host environment as your program;
22386 in that case, the debugging target is specified as a side effect when
22387 you use the @code{file} or @code{core} commands. When you need more
22388 flexibility---for example, running @value{GDBN} on a physically separate
22389 host, or controlling a standalone system over a serial port or a
22390 realtime system over a TCP/IP connection---you can use the @code{target}
22391 command to specify one of the target types configured for @value{GDBN}
22392 (@pxref{Target Commands, ,Commands for Managing Targets}).
22394 @cindex target architecture
22395 It is possible to build @value{GDBN} for several different @dfn{target
22396 architectures}. When @value{GDBN} is built like that, you can choose
22397 one of the available architectures with the @kbd{set architecture}
22401 @kindex set architecture
22402 @kindex show architecture
22403 @item set architecture @var{arch}
22404 This command sets the current target architecture to @var{arch}. The
22405 value of @var{arch} can be @code{"auto"}, in addition to one of the
22406 supported architectures.
22408 @item show architecture
22409 Show the current target architecture.
22411 @item set processor
22413 @kindex set processor
22414 @kindex show processor
22415 These are alias commands for, respectively, @code{set architecture}
22416 and @code{show architecture}.
22420 * Active Targets:: Active targets
22421 * Target Commands:: Commands for managing targets
22422 * Byte Order:: Choosing target byte order
22425 @node Active Targets
22426 @section Active Targets
22428 @cindex stacking targets
22429 @cindex active targets
22430 @cindex multiple targets
22432 There are multiple classes of targets such as: processes, executable files or
22433 recording sessions. Core files belong to the process class, making core file
22434 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22435 on multiple active targets, one in each class. This allows you to (for
22436 example) start a process and inspect its activity, while still having access to
22437 the executable file after the process finishes. Or if you start process
22438 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22439 presented a virtual layer of the recording target, while the process target
22440 remains stopped at the chronologically last point of the process execution.
22442 Use the @code{core-file} and @code{exec-file} commands to select a new core
22443 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22444 specify as a target a process that is already running, use the @code{attach}
22445 command (@pxref{Attach, ,Debugging an Already-running Process}).
22447 @node Target Commands
22448 @section Commands for Managing Targets
22451 @item target @var{type} @var{parameters}
22452 Connects the @value{GDBN} host environment to a target machine or
22453 process. A target is typically a protocol for talking to debugging
22454 facilities. You use the argument @var{type} to specify the type or
22455 protocol of the target machine.
22457 Further @var{parameters} are interpreted by the target protocol, but
22458 typically include things like device names or host names to connect
22459 with, process numbers, and baud rates.
22461 The @code{target} command does not repeat if you press @key{RET} again
22462 after executing the command.
22464 @kindex help target
22466 Displays the names of all targets available. To display targets
22467 currently selected, use either @code{info target} or @code{info files}
22468 (@pxref{Files, ,Commands to Specify Files}).
22470 @item help target @var{name}
22471 Describe a particular target, including any parameters necessary to
22474 @kindex set gnutarget
22475 @item set gnutarget @var{args}
22476 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22477 knows whether it is reading an @dfn{executable},
22478 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22479 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22480 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22483 @emph{Warning:} To specify a file format with @code{set gnutarget},
22484 you must know the actual BFD name.
22488 @xref{Files, , Commands to Specify Files}.
22490 @kindex show gnutarget
22491 @item show gnutarget
22492 Use the @code{show gnutarget} command to display what file format
22493 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22494 @value{GDBN} will determine the file format for each file automatically,
22495 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22498 @cindex common targets
22499 Here are some common targets (available, or not, depending on the GDB
22504 @item target exec @var{program}
22505 @cindex executable file target
22506 An executable file. @samp{target exec @var{program}} is the same as
22507 @samp{exec-file @var{program}}.
22509 @item target core @var{filename}
22510 @cindex core dump file target
22511 A core dump file. @samp{target core @var{filename}} is the same as
22512 @samp{core-file @var{filename}}.
22514 @item target remote @var{medium}
22515 @cindex remote target
22516 A remote system connected to @value{GDBN} via a serial line or network
22517 connection. This command tells @value{GDBN} to use its own remote
22518 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22520 For example, if you have a board connected to @file{/dev/ttya} on the
22521 machine running @value{GDBN}, you could say:
22524 target remote /dev/ttya
22527 @code{target remote} supports the @code{load} command. This is only
22528 useful if you have some other way of getting the stub to the target
22529 system, and you can put it somewhere in memory where it won't get
22530 clobbered by the download.
22532 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22533 @cindex built-in simulator target
22534 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22542 works; however, you cannot assume that a specific memory map, device
22543 drivers, or even basic I/O is available, although some simulators do
22544 provide these. For info about any processor-specific simulator details,
22545 see the appropriate section in @ref{Embedded Processors, ,Embedded
22548 @item target native
22549 @cindex native target
22550 Setup for local/native process debugging. Useful to make the
22551 @code{run} command spawn native processes (likewise @code{attach},
22552 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22553 (@pxref{set auto-connect-native-target}).
22557 Different targets are available on different configurations of @value{GDBN};
22558 your configuration may have more or fewer targets.
22560 Many remote targets require you to download the executable's code once
22561 you've successfully established a connection. You may wish to control
22562 various aspects of this process.
22567 @kindex set hash@r{, for remote monitors}
22568 @cindex hash mark while downloading
22569 This command controls whether a hash mark @samp{#} is displayed while
22570 downloading a file to the remote monitor. If on, a hash mark is
22571 displayed after each S-record is successfully downloaded to the
22575 @kindex show hash@r{, for remote monitors}
22576 Show the current status of displaying the hash mark.
22578 @item set debug monitor
22579 @kindex set debug monitor
22580 @cindex display remote monitor communications
22581 Enable or disable display of communications messages between
22582 @value{GDBN} and the remote monitor.
22584 @item show debug monitor
22585 @kindex show debug monitor
22586 Show the current status of displaying communications between
22587 @value{GDBN} and the remote monitor.
22592 @kindex load @var{filename} @var{offset}
22593 @item load @var{filename} @var{offset}
22595 Depending on what remote debugging facilities are configured into
22596 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22597 is meant to make @var{filename} (an executable) available for debugging
22598 on the remote system---by downloading, or dynamic linking, for example.
22599 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22600 the @code{add-symbol-file} command.
22602 If your @value{GDBN} does not have a @code{load} command, attempting to
22603 execute it gets the error message ``@code{You can't do that when your
22604 target is @dots{}}''
22606 The file is loaded at whatever address is specified in the executable.
22607 For some object file formats, you can specify the load address when you
22608 link the program; for other formats, like a.out, the object file format
22609 specifies a fixed address.
22610 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22612 It is also possible to tell @value{GDBN} to load the executable file at a
22613 specific offset described by the optional argument @var{offset}. When
22614 @var{offset} is provided, @var{filename} must also be provided.
22616 Depending on the remote side capabilities, @value{GDBN} may be able to
22617 load programs into flash memory.
22619 @code{load} does not repeat if you press @key{RET} again after using it.
22624 @kindex flash-erase
22626 @anchor{flash-erase}
22628 Erases all known flash memory regions on the target.
22633 @section Choosing Target Byte Order
22635 @cindex choosing target byte order
22636 @cindex target byte order
22638 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22639 offer the ability to run either big-endian or little-endian byte
22640 orders. Usually the executable or symbol will include a bit to
22641 designate the endian-ness, and you will not need to worry about
22642 which to use. However, you may still find it useful to adjust
22643 @value{GDBN}'s idea of processor endian-ness manually.
22647 @item set endian big
22648 Instruct @value{GDBN} to assume the target is big-endian.
22650 @item set endian little
22651 Instruct @value{GDBN} to assume the target is little-endian.
22653 @item set endian auto
22654 Instruct @value{GDBN} to use the byte order associated with the
22658 Display @value{GDBN}'s current idea of the target byte order.
22662 If the @code{set endian auto} mode is in effect and no executable has
22663 been selected, then the endianness used is the last one chosen either
22664 by one of the @code{set endian big} and @code{set endian little}
22665 commands or by inferring from the last executable used. If no
22666 endianness has been previously chosen, then the default for this mode
22667 is inferred from the target @value{GDBN} has been built for, and is
22668 @code{little} if the name of the target CPU has an @code{el} suffix
22669 and @code{big} otherwise.
22671 Note that these commands merely adjust interpretation of symbolic
22672 data on the host, and that they have absolutely no effect on the
22676 @node Remote Debugging
22677 @chapter Debugging Remote Programs
22678 @cindex remote debugging
22680 If you are trying to debug a program running on a machine that cannot run
22681 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22682 For example, you might use remote debugging on an operating system kernel,
22683 or on a small system which does not have a general purpose operating system
22684 powerful enough to run a full-featured debugger.
22686 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22687 to make this work with particular debugging targets. In addition,
22688 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22689 but not specific to any particular target system) which you can use if you
22690 write the remote stubs---the code that runs on the remote system to
22691 communicate with @value{GDBN}.
22693 Other remote targets may be available in your
22694 configuration of @value{GDBN}; use @code{help target} to list them.
22697 * Connecting:: Connecting to a remote target
22698 * File Transfer:: Sending files to a remote system
22699 * Server:: Using the gdbserver program
22700 * Remote Configuration:: Remote configuration
22701 * Remote Stub:: Implementing a remote stub
22705 @section Connecting to a Remote Target
22706 @cindex remote debugging, connecting
22707 @cindex @code{gdbserver}, connecting
22708 @cindex remote debugging, types of connections
22709 @cindex @code{gdbserver}, types of connections
22710 @cindex @code{gdbserver}, @code{target remote} mode
22711 @cindex @code{gdbserver}, @code{target extended-remote} mode
22713 This section describes how to connect to a remote target, including the
22714 types of connections and their differences, how to set up executable and
22715 symbol files on the host and target, and the commands used for
22716 connecting to and disconnecting from the remote target.
22718 @subsection Types of Remote Connections
22720 @value{GDBN} supports two types of remote connections, @code{target remote}
22721 mode and @code{target extended-remote} mode. Note that many remote targets
22722 support only @code{target remote} mode. There are several major
22723 differences between the two types of connections, enumerated here:
22727 @cindex remote debugging, detach and program exit
22728 @item Result of detach or program exit
22729 @strong{With target remote mode:} When the debugged program exits or you
22730 detach from it, @value{GDBN} disconnects from the target. When using
22731 @code{gdbserver}, @code{gdbserver} will exit.
22733 @strong{With target extended-remote mode:} When the debugged program exits or
22734 you detach from it, @value{GDBN} remains connected to the target, even
22735 though no program is running. You can rerun the program, attach to a
22736 running program, or use @code{monitor} commands specific to the target.
22738 When using @code{gdbserver} in this case, it does not exit unless it was
22739 invoked using the @option{--once} option. If the @option{--once} option
22740 was not used, you can ask @code{gdbserver} to exit using the
22741 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22743 @item Specifying the program to debug
22744 For both connection types you use the @code{file} command to specify the
22745 program on the host system. If you are using @code{gdbserver} there are
22746 some differences in how to specify the location of the program on the
22749 @strong{With target remote mode:} You must either specify the program to debug
22750 on the @code{gdbserver} command line or use the @option{--attach} option
22751 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22753 @cindex @option{--multi}, @code{gdbserver} option
22754 @strong{With target extended-remote mode:} You may specify the program to debug
22755 on the @code{gdbserver} command line, or you can load the program or attach
22756 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22758 @anchor{--multi Option in Types of Remote Connnections}
22759 You can start @code{gdbserver} without supplying an initial command to run
22760 or process ID to attach. To do this, use the @option{--multi} command line
22761 option. Then you can connect using @code{target extended-remote} and start
22762 the program you want to debug (see below for details on using the
22763 @code{run} command in this scenario). Note that the conditions under which
22764 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22765 (@code{target remote} or @code{target extended-remote}). The
22766 @option{--multi} option to @code{gdbserver} has no influence on that.
22768 @item The @code{run} command
22769 @strong{With target remote mode:} The @code{run} command is not
22770 supported. Once a connection has been established, you can use all
22771 the usual @value{GDBN} commands to examine and change data. The
22772 remote program is already running, so you can use commands like
22773 @kbd{step} and @kbd{continue}.
22775 @strong{With target extended-remote mode:} The @code{run} command is
22776 supported. The @code{run} command uses the value set by
22777 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22778 the program to run. Command line arguments are supported, except for
22779 wildcard expansion and I/O redirection (@pxref{Arguments}).
22781 If you specify the program to debug on the command line, then the
22782 @code{run} command is not required to start execution, and you can
22783 resume using commands like @kbd{step} and @kbd{continue} as with
22784 @code{target remote} mode.
22786 @anchor{Attaching in Types of Remote Connections}
22788 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22789 not supported. To attach to a running program using @code{gdbserver}, you
22790 must use the @option{--attach} option (@pxref{Running gdbserver}).
22792 @strong{With target extended-remote mode:} To attach to a running program,
22793 you may use the @code{attach} command after the connection has been
22794 established. If you are using @code{gdbserver}, you may also invoke
22795 @code{gdbserver} using the @option{--attach} option
22796 (@pxref{Running gdbserver}).
22798 Some remote targets allow @value{GDBN} to determine the executable file running
22799 in the process the debugger is attaching to. In such a case, @value{GDBN}
22800 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22801 between the executable file name running in the process and the name of the
22802 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22806 @anchor{Host and target files}
22807 @subsection Host and Target Files
22808 @cindex remote debugging, symbol files
22809 @cindex symbol files, remote debugging
22811 @value{GDBN}, running on the host, needs access to symbol and debugging
22812 information for your program running on the target. This requires
22813 access to an unstripped copy of your program, and possibly any associated
22814 symbol files. Note that this section applies equally to both @code{target
22815 remote} mode and @code{target extended-remote} mode.
22817 Some remote targets (@pxref{qXfer executable filename read}, and
22818 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22819 the same connection used to communicate with @value{GDBN}. With such a
22820 target, if the remote program is unstripped, the only command you need is
22821 @code{target remote} (or @code{target extended-remote}).
22823 If the remote program is stripped, or the target does not support remote
22824 program file access, start up @value{GDBN} using the name of the local
22825 unstripped copy of your program as the first argument, or use the
22826 @code{file} command. Use @code{set sysroot} to specify the location (on
22827 the host) of target libraries (unless your @value{GDBN} was compiled with
22828 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22829 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22832 The symbol file and target libraries must exactly match the executable
22833 and libraries on the target, with one exception: the files on the host
22834 system should not be stripped, even if the files on the target system
22835 are. Mismatched or missing files will lead to confusing results
22836 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22837 files may also prevent @code{gdbserver} from debugging multi-threaded
22840 @subsection Remote Connection Commands
22841 @cindex remote connection commands
22842 @value{GDBN} can communicate with the target over a serial line, a
22843 local Unix domain socket, or
22844 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22845 each case, @value{GDBN} uses the same protocol for debugging your
22846 program; only the medium carrying the debugging packets varies. The
22847 @code{target remote} and @code{target extended-remote} commands
22848 establish a connection to the target. Both commands accept the same
22849 arguments, which indicate the medium to use:
22853 @item target remote @var{serial-device}
22854 @itemx target extended-remote @var{serial-device}
22855 @cindex serial line, @code{target remote}
22856 Use @var{serial-device} to communicate with the target. For example,
22857 to use a serial line connected to the device named @file{/dev/ttyb}:
22860 target remote /dev/ttyb
22863 If you're using a serial line, you may want to give @value{GDBN} the
22864 @samp{--baud} option, or use the @code{set serial baud} command
22865 (@pxref{Remote Configuration, set serial baud}) before the
22866 @code{target} command.
22868 @item target remote @var{local-socket}
22869 @itemx target extended-remote @var{local-socket}
22870 @cindex local socket, @code{target remote}
22871 @cindex Unix domain socket
22872 Use @var{local-socket} to communicate with the target. For example,
22873 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22876 target remote /tmp/gdb-socket0
22879 Note that this command has the same form as the command to connect
22880 to a serial line. @value{GDBN} will automatically determine which
22881 kind of file you have specified and will make the appropriate kind
22883 This feature is not available if the host system does not support
22884 Unix domain sockets.
22886 @item target remote @code{@var{host}:@var{port}}
22887 @itemx target remote @code{[@var{host}]:@var{port}}
22888 @itemx target remote @code{tcp:@var{host}:@var{port}}
22889 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22890 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22891 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22892 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22893 @itemx target extended-remote @code{@var{host}:@var{port}}
22894 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22895 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22896 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22897 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22898 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22899 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22900 @cindex @acronym{TCP} port, @code{target remote}
22901 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22902 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22903 address, or a numeric @acronym{IPv6} address (with or without the
22904 square brackets to separate the address from the port); @var{port}
22905 must be a decimal number. The @var{host} could be the target machine
22906 itself, if it is directly connected to the net, or it might be a
22907 terminal server which in turn has a serial line to the target.
22909 For example, to connect to port 2828 on a terminal server named
22913 target remote manyfarms:2828
22916 To connect to port 2828 on a terminal server whose address is
22917 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22918 square bracket syntax:
22921 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22925 or explicitly specify the @acronym{IPv6} protocol:
22928 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22931 This last example may be confusing to the reader, because there is no
22932 visible separation between the hostname and the port number.
22933 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22934 using square brackets for clarity. However, it is important to
22935 mention that for @value{GDBN} there is no ambiguity: the number after
22936 the last colon is considered to be the port number.
22938 If your remote target is actually running on the same machine as your
22939 debugger session (e.g.@: a simulator for your target running on the
22940 same host), you can omit the hostname. For example, to connect to
22941 port 1234 on your local machine:
22944 target remote :1234
22948 Note that the colon is still required here.
22950 @item target remote @code{udp:@var{host}:@var{port}}
22951 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22952 @itemx target remote @code{udp4:@var{host}:@var{port}}
22953 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22954 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22955 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22956 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22957 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22958 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22959 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22960 @cindex @acronym{UDP} port, @code{target remote}
22961 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22962 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22965 target remote udp:manyfarms:2828
22968 When using a @acronym{UDP} connection for remote debugging, you should
22969 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22970 can silently drop packets on busy or unreliable networks, which will
22971 cause havoc with your debugging session.
22973 @item target remote | @var{command}
22974 @itemx target extended-remote | @var{command}
22975 @cindex pipe, @code{target remote} to
22976 Run @var{command} in the background and communicate with it using a
22977 pipe. The @var{command} is a shell command, to be parsed and expanded
22978 by the system's command shell, @code{/bin/sh}; it should expect remote
22979 protocol packets on its standard input, and send replies on its
22980 standard output. You could use this to run a stand-alone simulator
22981 that speaks the remote debugging protocol, to make net connections
22982 using programs like @code{ssh}, or for other similar tricks.
22984 If @var{command} closes its standard output (perhaps by exiting),
22985 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22986 program has already exited, this will have no effect.)
22990 @cindex interrupting remote programs
22991 @cindex remote programs, interrupting
22992 Whenever @value{GDBN} is waiting for the remote program, if you type the
22993 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22994 program. This may or may not succeed, depending in part on the hardware
22995 and the serial drivers the remote system uses. If you type the
22996 interrupt character once again, @value{GDBN} displays this prompt:
22999 Interrupted while waiting for the program.
23000 Give up (and stop debugging it)? (y or n)
23003 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
23004 the remote debugging session. (If you decide you want to try again later,
23005 you can use @kbd{target remote} again to connect once more.) If you type
23006 @kbd{n}, @value{GDBN} goes back to waiting.
23008 In @code{target extended-remote} mode, typing @kbd{n} will leave
23009 @value{GDBN} connected to the target.
23012 @kindex detach (remote)
23014 When you have finished debugging the remote program, you can use the
23015 @code{detach} command to release it from @value{GDBN} control.
23016 Detaching from the target normally resumes its execution, but the results
23017 will depend on your particular remote stub. After the @code{detach}
23018 command in @code{target remote} mode, @value{GDBN} is free to connect to
23019 another target. In @code{target extended-remote} mode, @value{GDBN} is
23020 still connected to the target.
23024 The @code{disconnect} command closes the connection to the target, and
23025 the target is generally not resumed. It will wait for @value{GDBN}
23026 (this instance or another one) to connect and continue debugging. After
23027 the @code{disconnect} command, @value{GDBN} is again free to connect to
23030 @cindex send command to remote monitor
23031 @cindex extend @value{GDBN} for remote targets
23032 @cindex add new commands for external monitor
23034 @item monitor @var{cmd}
23035 This command allows you to send arbitrary commands directly to the
23036 remote monitor. Since @value{GDBN} doesn't care about the commands it
23037 sends like this, this command is the way to extend @value{GDBN}---you
23038 can add new commands that only the external monitor will understand
23042 @node File Transfer
23043 @section Sending files to a remote system
23044 @cindex remote target, file transfer
23045 @cindex file transfer
23046 @cindex sending files to remote systems
23048 Some remote targets offer the ability to transfer files over the same
23049 connection used to communicate with @value{GDBN}. This is convenient
23050 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
23051 running @code{gdbserver} over a network interface. For other targets,
23052 e.g.@: embedded devices with only a single serial port, this may be
23053 the only way to upload or download files.
23055 Not all remote targets support these commands.
23059 @item remote put @var{hostfile} @var{targetfile}
23060 Copy file @var{hostfile} from the host system (the machine running
23061 @value{GDBN}) to @var{targetfile} on the target system.
23064 @item remote get @var{targetfile} @var{hostfile}
23065 Copy file @var{targetfile} from the target system to @var{hostfile}
23066 on the host system.
23068 @kindex remote delete
23069 @item remote delete @var{targetfile}
23070 Delete @var{targetfile} from the target system.
23075 @section Using the @code{gdbserver} Program
23078 @cindex remote connection without stubs
23079 @code{gdbserver} is a control program for Unix-like systems, which
23080 allows you to connect your program with a remote @value{GDBN} via
23081 @code{target remote} or @code{target extended-remote}---but without
23082 linking in the usual debugging stub.
23084 @code{gdbserver} is not a complete replacement for the debugging stubs,
23085 because it requires essentially the same operating-system facilities
23086 that @value{GDBN} itself does. In fact, a system that can run
23087 @code{gdbserver} to connect to a remote @value{GDBN} could also run
23088 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
23089 because it is a much smaller program than @value{GDBN} itself. It is
23090 also easier to port than all of @value{GDBN}, so you may be able to get
23091 started more quickly on a new system by using @code{gdbserver}.
23092 Finally, if you develop code for real-time systems, you may find that
23093 the tradeoffs involved in real-time operation make it more convenient to
23094 do as much development work as possible on another system, for example
23095 by cross-compiling. You can use @code{gdbserver} to make a similar
23096 choice for debugging.
23098 @value{GDBN} and @code{gdbserver} communicate via either a serial line
23099 or a TCP connection, using the standard @value{GDBN} remote serial
23103 @emph{Warning:} @code{gdbserver} does not have any built-in security.
23104 Do not run @code{gdbserver} connected to any public network; a
23105 @value{GDBN} connection to @code{gdbserver} provides access to the
23106 target system with the same privileges as the user running
23110 @anchor{Running gdbserver}
23111 @subsection Running @code{gdbserver}
23112 @cindex arguments, to @code{gdbserver}
23113 @cindex @code{gdbserver}, command-line arguments
23115 Run @code{gdbserver} on the target system. You need a copy of the
23116 program you want to debug, including any libraries it requires.
23117 @code{gdbserver} does not need your program's symbol table, so you can
23118 strip the program if necessary to save space. @value{GDBN} on the host
23119 system does all the symbol handling.
23121 To use the server, you must tell it how to communicate with @value{GDBN};
23122 the name of your program; and the arguments for your program. The usual
23126 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
23129 @var{comm} is either a device name (to use a serial line), or a TCP
23130 hostname and portnumber, or @code{-} or @code{stdio} to use
23131 stdin/stdout of @code{gdbserver}.
23132 For example, to debug Emacs with the argument
23133 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
23137 target> gdbserver /dev/com1 emacs foo.txt
23140 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
23143 To use a TCP connection instead of a serial line:
23146 target> gdbserver host:2345 emacs foo.txt
23149 The only difference from the previous example is the first argument,
23150 specifying that you are communicating with the host @value{GDBN} via
23151 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
23152 expect a TCP connection from machine @samp{host} to local TCP port 2345.
23153 (Currently, the @samp{host} part is ignored.) You can choose any number
23154 you want for the port number as long as it does not conflict with any
23155 TCP ports already in use on the target system (for example, @code{23} is
23156 reserved for @code{telnet}).@footnote{If you choose a port number that
23157 conflicts with another service, @code{gdbserver} prints an error message
23158 and exits.} You must use the same port number with the host @value{GDBN}
23159 @code{target remote} command.
23161 The @code{stdio} connection is useful when starting @code{gdbserver}
23165 (gdb) target remote | ssh -T hostname gdbserver - hello
23168 The @samp{-T} option to ssh is provided because we don't need a remote pty,
23169 and we don't want escape-character handling. Ssh does this by default when
23170 a command is provided, the flag is provided to make it explicit.
23171 You could elide it if you want to.
23173 Programs started with stdio-connected gdbserver have @file{/dev/null} for
23174 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
23175 display through a pipe connected to gdbserver.
23176 Both @code{stdout} and @code{stderr} use the same pipe.
23178 @anchor{Attaching to a program}
23179 @subsubsection Attaching to a Running Program
23180 @cindex attach to a program, @code{gdbserver}
23181 @cindex @option{--attach}, @code{gdbserver} option
23183 On some targets, @code{gdbserver} can also attach to running programs.
23184 This is accomplished via the @code{--attach} argument. The syntax is:
23187 target> gdbserver --attach @var{comm} @var{pid}
23190 @var{pid} is the process ID of a currently running process. It isn't
23191 necessary to point @code{gdbserver} at a binary for the running process.
23193 In @code{target extended-remote} mode, you can also attach using the
23194 @value{GDBN} attach command
23195 (@pxref{Attaching in Types of Remote Connections}).
23198 You can debug processes by name instead of process ID if your target has the
23199 @code{pidof} utility:
23202 target> gdbserver --attach @var{comm} `pidof @var{program}`
23205 In case more than one copy of @var{program} is running, or @var{program}
23206 has multiple threads, most versions of @code{pidof} support the
23207 @code{-s} option to only return the first process ID.
23209 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
23211 This section applies only when @code{gdbserver} is run to listen on a TCP
23214 @code{gdbserver} normally terminates after all of its debugged processes have
23215 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
23216 extended-remote}, @code{gdbserver} stays running even with no processes left.
23217 @value{GDBN} normally terminates the spawned debugged process on its exit,
23218 which normally also terminates @code{gdbserver} in the @kbd{target remote}
23219 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
23220 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
23221 stays running even in the @kbd{target remote} mode.
23223 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
23224 Such reconnecting is useful for features like @ref{disconnected tracing}. For
23225 completeness, at most one @value{GDBN} can be connected at a time.
23227 @cindex @option{--once}, @code{gdbserver} option
23228 By default, @code{gdbserver} keeps the listening TCP port open, so that
23229 subsequent connections are possible. However, if you start @code{gdbserver}
23230 with the @option{--once} option, it will stop listening for any further
23231 connection attempts after connecting to the first @value{GDBN} session. This
23232 means no further connections to @code{gdbserver} will be possible after the
23233 first one. It also means @code{gdbserver} will terminate after the first
23234 connection with remote @value{GDBN} has closed, even for unexpectedly closed
23235 connections and even in the @kbd{target extended-remote} mode. The
23236 @option{--once} option allows reusing the same port number for connecting to
23237 multiple instances of @code{gdbserver} running on the same host, since each
23238 instance closes its port after the first connection.
23240 @anchor{Other Command-Line Arguments for gdbserver}
23241 @subsubsection Other Command-Line Arguments for @code{gdbserver}
23243 You can use the @option{--multi} option to start @code{gdbserver} without
23244 specifying a program to debug or a process to attach to. Then you can
23245 attach in @code{target extended-remote} mode and run or attach to a
23246 program. For more information,
23247 @pxref{--multi Option in Types of Remote Connnections}.
23249 @cindex @option{--debug}, @code{gdbserver} option
23250 The @option{--debug} option tells @code{gdbserver} to display extra
23251 status information about the debugging process.
23252 @cindex @option{--remote-debug}, @code{gdbserver} option
23253 The @option{--remote-debug} option tells @code{gdbserver} to display
23254 remote protocol debug output.
23255 @cindex @option{--debug-file}, @code{gdbserver} option
23256 @cindex @code{gdbserver}, send all debug output to a single file
23257 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
23258 write any debug output to the given @var{filename}. These options are intended
23259 for @code{gdbserver} development and for bug reports to the developers.
23261 @cindex @option{--debug-format}, @code{gdbserver} option
23262 The @option{--debug-format=option1[,option2,...]} option tells
23263 @code{gdbserver} to include additional information in each output.
23264 Possible options are:
23268 Turn off all extra information in debugging output.
23270 Turn on all extra information in debugging output.
23272 Include a timestamp in each line of debugging output.
23275 Options are processed in order. Thus, for example, if @option{none}
23276 appears last then no additional information is added to debugging output.
23278 @cindex @option{--wrapper}, @code{gdbserver} option
23279 The @option{--wrapper} option specifies a wrapper to launch programs
23280 for debugging. The option should be followed by the name of the
23281 wrapper, then any command-line arguments to pass to the wrapper, then
23282 @kbd{--} indicating the end of the wrapper arguments.
23284 @code{gdbserver} runs the specified wrapper program with a combined
23285 command line including the wrapper arguments, then the name of the
23286 program to debug, then any arguments to the program. The wrapper
23287 runs until it executes your program, and then @value{GDBN} gains control.
23289 You can use any program that eventually calls @code{execve} with
23290 its arguments as a wrapper. Several standard Unix utilities do
23291 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
23292 with @code{exec "$@@"} will also work.
23294 For example, you can use @code{env} to pass an environment variable to
23295 the debugged program, without setting the variable in @code{gdbserver}'s
23299 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
23302 @cindex @option{--selftest}
23303 The @option{--selftest} option runs the self tests in @code{gdbserver}:
23306 $ gdbserver --selftest
23307 Ran 2 unit tests, 0 failed
23310 These tests are disabled in release.
23311 @subsection Connecting to @code{gdbserver}
23313 The basic procedure for connecting to the remote target is:
23317 Run @value{GDBN} on the host system.
23320 Make sure you have the necessary symbol files
23321 (@pxref{Host and target files}).
23322 Load symbols for your application using the @code{file} command before you
23323 connect. Use @code{set sysroot} to locate target libraries (unless your
23324 @value{GDBN} was compiled with the correct sysroot using
23325 @code{--with-sysroot}).
23328 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23329 For TCP connections, you must start up @code{gdbserver} prior to using
23330 the @code{target} command. Otherwise you may get an error whose
23331 text depends on the host system, but which usually looks something like
23332 @samp{Connection refused}. Don't use the @code{load}
23333 command in @value{GDBN} when using @code{target remote} mode, since the
23334 program is already on the target.
23338 @anchor{Monitor Commands for gdbserver}
23339 @subsection Monitor Commands for @code{gdbserver}
23340 @cindex monitor commands, for @code{gdbserver}
23342 During a @value{GDBN} session using @code{gdbserver}, you can use the
23343 @code{monitor} command to send special requests to @code{gdbserver}.
23344 Here are the available commands.
23348 List the available monitor commands.
23350 @item monitor set debug 0
23351 @itemx monitor set debug 1
23352 Disable or enable general debugging messages.
23354 @item monitor set remote-debug 0
23355 @itemx monitor set remote-debug 1
23356 Disable or enable specific debugging messages associated with the remote
23357 protocol (@pxref{Remote Protocol}).
23359 @item monitor set debug-file filename
23360 @itemx monitor set debug-file
23361 Send any debug output to the given file, or to stderr.
23363 @item monitor set debug-format option1@r{[},option2,...@r{]}
23364 Specify additional text to add to debugging messages.
23365 Possible options are:
23369 Turn off all extra information in debugging output.
23371 Turn on all extra information in debugging output.
23373 Include a timestamp in each line of debugging output.
23376 Options are processed in order. Thus, for example, if @option{none}
23377 appears last then no additional information is added to debugging output.
23379 @item monitor set libthread-db-search-path [PATH]
23380 @cindex gdbserver, search path for @code{libthread_db}
23381 When this command is issued, @var{path} is a colon-separated list of
23382 directories to search for @code{libthread_db} (@pxref{Threads,,set
23383 libthread-db-search-path}). If you omit @var{path},
23384 @samp{libthread-db-search-path} will be reset to its default value.
23386 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23387 not supported in @code{gdbserver}.
23390 Tell gdbserver to exit immediately. This command should be followed by
23391 @code{disconnect} to close the debugging session. @code{gdbserver} will
23392 detach from any attached processes and kill any processes it created.
23393 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23394 of a multi-process mode debug session.
23398 @subsection Tracepoints support in @code{gdbserver}
23399 @cindex tracepoints support in @code{gdbserver}
23401 On some targets, @code{gdbserver} supports tracepoints, fast
23402 tracepoints and static tracepoints.
23404 For fast or static tracepoints to work, a special library called the
23405 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23406 This library is built and distributed as an integral part of
23407 @code{gdbserver}. In addition, support for static tracepoints
23408 requires building the in-process agent library with static tracepoints
23409 support. At present, the UST (LTTng Userspace Tracer,
23410 @url{http://lttng.org/ust}) tracing engine is supported. This support
23411 is automatically available if UST development headers are found in the
23412 standard include path when @code{gdbserver} is built, or if
23413 @code{gdbserver} was explicitly configured using @option{--with-ust}
23414 to point at such headers. You can explicitly disable the support
23415 using @option{--with-ust=no}.
23417 There are several ways to load the in-process agent in your program:
23420 @item Specifying it as dependency at link time
23422 You can link your program dynamically with the in-process agent
23423 library. On most systems, this is accomplished by adding
23424 @code{-linproctrace} to the link command.
23426 @item Using the system's preloading mechanisms
23428 You can force loading the in-process agent at startup time by using
23429 your system's support for preloading shared libraries. Many Unixes
23430 support the concept of preloading user defined libraries. In most
23431 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23432 in the environment. See also the description of @code{gdbserver}'s
23433 @option{--wrapper} command line option.
23435 @item Using @value{GDBN} to force loading the agent at run time
23437 On some systems, you can force the inferior to load a shared library,
23438 by calling a dynamic loader function in the inferior that takes care
23439 of dynamically looking up and loading a shared library. On most Unix
23440 systems, the function is @code{dlopen}. You'll use the @code{call}
23441 command for that. For example:
23444 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23447 Note that on most Unix systems, for the @code{dlopen} function to be
23448 available, the program needs to be linked with @code{-ldl}.
23451 On systems that have a userspace dynamic loader, like most Unix
23452 systems, when you connect to @code{gdbserver} using @code{target
23453 remote}, you'll find that the program is stopped at the dynamic
23454 loader's entry point, and no shared library has been loaded in the
23455 program's address space yet, including the in-process agent. In that
23456 case, before being able to use any of the fast or static tracepoints
23457 features, you need to let the loader run and load the shared
23458 libraries. The simplest way to do that is to run the program to the
23459 main procedure. E.g., if debugging a C or C@t{++} program, start
23460 @code{gdbserver} like so:
23463 $ gdbserver :9999 myprogram
23466 Start GDB and connect to @code{gdbserver} like so, and run to main:
23470 (@value{GDBP}) target remote myhost:9999
23471 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23472 (@value{GDBP}) b main
23473 (@value{GDBP}) continue
23476 The in-process tracing agent library should now be loaded into the
23477 process; you can confirm it with the @code{info sharedlibrary}
23478 command, which will list @file{libinproctrace.so} as loaded in the
23479 process. You are now ready to install fast tracepoints, list static
23480 tracepoint markers, probe static tracepoints markers, and start
23483 @node Remote Configuration
23484 @section Remote Configuration
23487 @kindex show remote
23488 This section documents the configuration options available when
23489 debugging remote programs. For the options related to the File I/O
23490 extensions of the remote protocol, see @ref{system,
23491 system-call-allowed}.
23494 @item set remoteaddresssize @var{bits}
23495 @cindex address size for remote targets
23496 @cindex bits in remote address
23497 Set the maximum size of address in a memory packet to the specified
23498 number of bits. @value{GDBN} will mask off the address bits above
23499 that number, when it passes addresses to the remote target. The
23500 default value is the number of bits in the target's address.
23502 @item show remoteaddresssize
23503 Show the current value of remote address size in bits.
23505 @item set serial baud @var{n}
23506 @cindex baud rate for remote targets
23507 Set the baud rate for the remote serial I/O to @var{n} baud. The
23508 value is used to set the speed of the serial port used for debugging
23511 @item show serial baud
23512 Show the current speed of the remote connection.
23514 @item set serial parity @var{parity}
23515 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23516 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23518 @item show serial parity
23519 Show the current parity of the serial port.
23521 @item set remotebreak
23522 @cindex interrupt remote programs
23523 @cindex BREAK signal instead of Ctrl-C
23524 @anchor{set remotebreak}
23525 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23526 when you type @kbd{Ctrl-c} to interrupt the program running
23527 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23528 character instead. The default is off, since most remote systems
23529 expect to see @samp{Ctrl-C} as the interrupt signal.
23531 @item show remotebreak
23532 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23533 interrupt the remote program.
23535 @item set remoteflow on
23536 @itemx set remoteflow off
23537 @kindex set remoteflow
23538 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23539 on the serial port used to communicate to the remote target.
23541 @item show remoteflow
23542 @kindex show remoteflow
23543 Show the current setting of hardware flow control.
23545 @item set remotelogbase @var{base}
23546 Set the base (a.k.a.@: radix) of logging serial protocol
23547 communications to @var{base}. Supported values of @var{base} are:
23548 @code{ascii}, @code{octal}, and @code{hex}. The default is
23551 @item show remotelogbase
23552 Show the current setting of the radix for logging remote serial
23555 @item set remotelogfile @var{file}
23556 @cindex record serial communications on file
23557 Record remote serial communications on the named @var{file}. The
23558 default is not to record at all.
23560 @item show remotelogfile
23561 Show the current setting of the file name on which to record the
23562 serial communications.
23564 @item set remotetimeout @var{num}
23565 @cindex timeout for serial communications
23566 @cindex remote timeout
23567 Set the timeout limit to wait for the remote target to respond to
23568 @var{num} seconds. The default is 2 seconds.
23570 @item show remotetimeout
23571 Show the current number of seconds to wait for the remote target
23574 @cindex limit hardware breakpoints and watchpoints
23575 @cindex remote target, limit break- and watchpoints
23576 @anchor{set remote hardware-watchpoint-limit}
23577 @anchor{set remote hardware-breakpoint-limit}
23578 @item set remote hardware-watchpoint-limit @var{limit}
23579 @itemx set remote hardware-breakpoint-limit @var{limit}
23580 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23581 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23582 watchpoints or breakpoints, and @code{unlimited} for unlimited
23583 watchpoints or breakpoints.
23585 @item show remote hardware-watchpoint-limit
23586 @itemx show remote hardware-breakpoint-limit
23587 Show the current limit for the number of hardware watchpoints or
23588 breakpoints that @value{GDBN} can use.
23590 @cindex limit hardware watchpoints length
23591 @cindex remote target, limit watchpoints length
23592 @anchor{set remote hardware-watchpoint-length-limit}
23593 @item set remote hardware-watchpoint-length-limit @var{limit}
23594 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23595 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23596 hardware watchpoints and @code{unlimited} allows watchpoints of any
23599 @item show remote hardware-watchpoint-length-limit
23600 Show the current limit (in bytes) of the maximum length of
23601 a remote hardware watchpoint.
23603 @item set remote exec-file @var{filename}
23604 @itemx show remote exec-file
23605 @anchor{set remote exec-file}
23606 @cindex executable file, for remote target
23607 Select the file used for @code{run} with @code{target
23608 extended-remote}. This should be set to a filename valid on the
23609 target system. If it is not set, the target will use a default
23610 filename (e.g.@: the last program run).
23612 @item set remote interrupt-sequence
23613 @cindex interrupt remote programs
23614 @cindex select Ctrl-C, BREAK or BREAK-g
23615 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23616 @samp{BREAK-g} as the
23617 sequence to the remote target in order to interrupt the execution.
23618 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23619 is high level of serial line for some certain time.
23620 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23621 It is @code{BREAK} signal followed by character @code{g}.
23623 @item show remote interrupt-sequence
23624 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23625 is sent by @value{GDBN} to interrupt the remote program.
23626 @code{BREAK-g} is BREAK signal followed by @code{g} and
23627 also known as Magic SysRq g.
23629 @item set remote interrupt-on-connect
23630 @cindex send interrupt-sequence on start
23631 Specify whether interrupt-sequence is sent to remote target when
23632 @value{GDBN} connects to it. This is mostly needed when you debug
23633 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23634 which is known as Magic SysRq g in order to connect @value{GDBN}.
23636 @item show remote interrupt-on-connect
23637 Show whether interrupt-sequence is sent
23638 to remote target when @value{GDBN} connects to it.
23642 @item set tcp auto-retry on
23643 @cindex auto-retry, for remote TCP target
23644 Enable auto-retry for remote TCP connections. This is useful if the remote
23645 debugging agent is launched in parallel with @value{GDBN}; there is a race
23646 condition because the agent may not become ready to accept the connection
23647 before @value{GDBN} attempts to connect. When auto-retry is
23648 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23649 to establish the connection using the timeout specified by
23650 @code{set tcp connect-timeout}.
23652 @item set tcp auto-retry off
23653 Do not auto-retry failed TCP connections.
23655 @item show tcp auto-retry
23656 Show the current auto-retry setting.
23658 @item set tcp connect-timeout @var{seconds}
23659 @itemx set tcp connect-timeout unlimited
23660 @cindex connection timeout, for remote TCP target
23661 @cindex timeout, for remote target connection
23662 Set the timeout for establishing a TCP connection to the remote target to
23663 @var{seconds}. The timeout affects both polling to retry failed connections
23664 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23665 that are merely slow to complete, and represents an approximate cumulative
23666 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23667 @value{GDBN} will keep attempting to establish a connection forever,
23668 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23670 @item show tcp connect-timeout
23671 Show the current connection timeout setting.
23674 @cindex remote packets, enabling and disabling
23675 The @value{GDBN} remote protocol autodetects the packets supported by
23676 your debugging stub. If you need to override the autodetection, you
23677 can use these commands to enable or disable individual packets. Each
23678 packet can be set to @samp{on} (the remote target supports this
23679 packet), @samp{off} (the remote target does not support this packet),
23680 or @samp{auto} (detect remote target support for this packet). They
23681 all default to @samp{auto}. For more information about each packet,
23682 see @ref{Remote Protocol}.
23684 During normal use, you should not have to use any of these commands.
23685 If you do, that may be a bug in your remote debugging stub, or a bug
23686 in @value{GDBN}. You may want to report the problem to the
23687 @value{GDBN} developers.
23689 For each packet @var{name}, the command to enable or disable the
23690 packet is @code{set remote @var{name}-packet}. The available settings
23693 @multitable @columnfractions 0.28 0.32 0.25
23696 @tab Related Features
23698 @item @code{fetch-register}
23700 @tab @code{info registers}
23702 @item @code{set-register}
23706 @item @code{binary-download}
23708 @tab @code{load}, @code{set}
23710 @item @code{read-aux-vector}
23711 @tab @code{qXfer:auxv:read}
23712 @tab @code{info auxv}
23714 @item @code{symbol-lookup}
23715 @tab @code{qSymbol}
23716 @tab Detecting multiple threads
23718 @item @code{attach}
23719 @tab @code{vAttach}
23722 @item @code{verbose-resume}
23724 @tab Stepping or resuming multiple threads
23730 @item @code{software-breakpoint}
23734 @item @code{hardware-breakpoint}
23738 @item @code{write-watchpoint}
23742 @item @code{read-watchpoint}
23746 @item @code{access-watchpoint}
23750 @item @code{pid-to-exec-file}
23751 @tab @code{qXfer:exec-file:read}
23752 @tab @code{attach}, @code{run}
23754 @item @code{target-features}
23755 @tab @code{qXfer:features:read}
23756 @tab @code{set architecture}
23758 @item @code{library-info}
23759 @tab @code{qXfer:libraries:read}
23760 @tab @code{info sharedlibrary}
23762 @item @code{memory-map}
23763 @tab @code{qXfer:memory-map:read}
23764 @tab @code{info mem}
23766 @item @code{read-sdata-object}
23767 @tab @code{qXfer:sdata:read}
23768 @tab @code{print $_sdata}
23770 @item @code{read-siginfo-object}
23771 @tab @code{qXfer:siginfo:read}
23772 @tab @code{print $_siginfo}
23774 @item @code{write-siginfo-object}
23775 @tab @code{qXfer:siginfo:write}
23776 @tab @code{set $_siginfo}
23778 @item @code{threads}
23779 @tab @code{qXfer:threads:read}
23780 @tab @code{info threads}
23782 @item @code{get-thread-local-@*storage-address}
23783 @tab @code{qGetTLSAddr}
23784 @tab Displaying @code{__thread} variables
23786 @item @code{get-thread-information-block-address}
23787 @tab @code{qGetTIBAddr}
23788 @tab Display MS-Windows Thread Information Block.
23790 @item @code{search-memory}
23791 @tab @code{qSearch:memory}
23794 @item @code{supported-packets}
23795 @tab @code{qSupported}
23796 @tab Remote communications parameters
23798 @item @code{catch-syscalls}
23799 @tab @code{QCatchSyscalls}
23800 @tab @code{catch syscall}
23802 @item @code{pass-signals}
23803 @tab @code{QPassSignals}
23804 @tab @code{handle @var{signal}}
23806 @item @code{program-signals}
23807 @tab @code{QProgramSignals}
23808 @tab @code{handle @var{signal}}
23810 @item @code{hostio-close-packet}
23811 @tab @code{vFile:close}
23812 @tab @code{remote get}, @code{remote put}
23814 @item @code{hostio-open-packet}
23815 @tab @code{vFile:open}
23816 @tab @code{remote get}, @code{remote put}
23818 @item @code{hostio-pread-packet}
23819 @tab @code{vFile:pread}
23820 @tab @code{remote get}, @code{remote put}
23822 @item @code{hostio-pwrite-packet}
23823 @tab @code{vFile:pwrite}
23824 @tab @code{remote get}, @code{remote put}
23826 @item @code{hostio-unlink-packet}
23827 @tab @code{vFile:unlink}
23828 @tab @code{remote delete}
23830 @item @code{hostio-readlink-packet}
23831 @tab @code{vFile:readlink}
23834 @item @code{hostio-fstat-packet}
23835 @tab @code{vFile:fstat}
23838 @item @code{hostio-setfs-packet}
23839 @tab @code{vFile:setfs}
23842 @item @code{noack-packet}
23843 @tab @code{QStartNoAckMode}
23844 @tab Packet acknowledgment
23846 @item @code{osdata}
23847 @tab @code{qXfer:osdata:read}
23848 @tab @code{info os}
23850 @item @code{query-attached}
23851 @tab @code{qAttached}
23852 @tab Querying remote process attach state.
23854 @item @code{trace-buffer-size}
23855 @tab @code{QTBuffer:size}
23856 @tab @code{set trace-buffer-size}
23858 @item @code{trace-status}
23859 @tab @code{qTStatus}
23860 @tab @code{tstatus}
23862 @item @code{traceframe-info}
23863 @tab @code{qXfer:traceframe-info:read}
23864 @tab Traceframe info
23866 @item @code{install-in-trace}
23867 @tab @code{InstallInTrace}
23868 @tab Install tracepoint in tracing
23870 @item @code{disable-randomization}
23871 @tab @code{QDisableRandomization}
23872 @tab @code{set disable-randomization}
23874 @item @code{startup-with-shell}
23875 @tab @code{QStartupWithShell}
23876 @tab @code{set startup-with-shell}
23878 @item @code{environment-hex-encoded}
23879 @tab @code{QEnvironmentHexEncoded}
23880 @tab @code{set environment}
23882 @item @code{environment-unset}
23883 @tab @code{QEnvironmentUnset}
23884 @tab @code{unset environment}
23886 @item @code{environment-reset}
23887 @tab @code{QEnvironmentReset}
23888 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23890 @item @code{set-working-dir}
23891 @tab @code{QSetWorkingDir}
23892 @tab @code{set cwd}
23894 @item @code{conditional-breakpoints-packet}
23895 @tab @code{Z0 and Z1}
23896 @tab @code{Support for target-side breakpoint condition evaluation}
23898 @item @code{multiprocess-extensions}
23899 @tab @code{multiprocess extensions}
23900 @tab Debug multiple processes and remote process PID awareness
23902 @item @code{swbreak-feature}
23903 @tab @code{swbreak stop reason}
23906 @item @code{hwbreak-feature}
23907 @tab @code{hwbreak stop reason}
23910 @item @code{fork-event-feature}
23911 @tab @code{fork stop reason}
23914 @item @code{vfork-event-feature}
23915 @tab @code{vfork stop reason}
23918 @item @code{exec-event-feature}
23919 @tab @code{exec stop reason}
23922 @item @code{thread-events}
23923 @tab @code{QThreadEvents}
23924 @tab Tracking thread lifetime.
23926 @item @code{no-resumed-stop-reply}
23927 @tab @code{no resumed thread left stop reply}
23928 @tab Tracking thread lifetime.
23933 @section Implementing a Remote Stub
23935 @cindex debugging stub, example
23936 @cindex remote stub, example
23937 @cindex stub example, remote debugging
23938 The stub files provided with @value{GDBN} implement the target side of the
23939 communication protocol, and the @value{GDBN} side is implemented in the
23940 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23941 these subroutines to communicate, and ignore the details. (If you're
23942 implementing your own stub file, you can still ignore the details: start
23943 with one of the existing stub files. @file{sparc-stub.c} is the best
23944 organized, and therefore the easiest to read.)
23946 @cindex remote serial debugging, overview
23947 To debug a program running on another machine (the debugging
23948 @dfn{target} machine), you must first arrange for all the usual
23949 prerequisites for the program to run by itself. For example, for a C
23954 A startup routine to set up the C runtime environment; these usually
23955 have a name like @file{crt0}. The startup routine may be supplied by
23956 your hardware supplier, or you may have to write your own.
23959 A C subroutine library to support your program's
23960 subroutine calls, notably managing input and output.
23963 A way of getting your program to the other machine---for example, a
23964 download program. These are often supplied by the hardware
23965 manufacturer, but you may have to write your own from hardware
23969 The next step is to arrange for your program to use a serial port to
23970 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23971 machine). In general terms, the scheme looks like this:
23975 @value{GDBN} already understands how to use this protocol; when everything
23976 else is set up, you can simply use the @samp{target remote} command
23977 (@pxref{Targets,,Specifying a Debugging Target}).
23979 @item On the target,
23980 you must link with your program a few special-purpose subroutines that
23981 implement the @value{GDBN} remote serial protocol. The file containing these
23982 subroutines is called a @dfn{debugging stub}.
23984 On certain remote targets, you can use an auxiliary program
23985 @code{gdbserver} instead of linking a stub into your program.
23986 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23989 The debugging stub is specific to the architecture of the remote
23990 machine; for example, use @file{sparc-stub.c} to debug programs on
23993 @cindex remote serial stub list
23994 These working remote stubs are distributed with @value{GDBN}:
23999 @cindex @file{i386-stub.c}
24002 For Intel 386 and compatible architectures.
24005 @cindex @file{m68k-stub.c}
24006 @cindex Motorola 680x0
24008 For Motorola 680x0 architectures.
24011 @cindex @file{sh-stub.c}
24014 For Renesas SH architectures.
24017 @cindex @file{sparc-stub.c}
24019 For @sc{sparc} architectures.
24021 @item sparcl-stub.c
24022 @cindex @file{sparcl-stub.c}
24025 For Fujitsu @sc{sparclite} architectures.
24029 The @file{README} file in the @value{GDBN} distribution may list other
24030 recently added stubs.
24033 * Stub Contents:: What the stub can do for you
24034 * Bootstrapping:: What you must do for the stub
24035 * Debug Session:: Putting it all together
24038 @node Stub Contents
24039 @subsection What the Stub Can Do for You
24041 @cindex remote serial stub
24042 The debugging stub for your architecture supplies these three
24046 @item set_debug_traps
24047 @findex set_debug_traps
24048 @cindex remote serial stub, initialization
24049 This routine arranges for @code{handle_exception} to run when your
24050 program stops. You must call this subroutine explicitly in your
24051 program's startup code.
24053 @item handle_exception
24054 @findex handle_exception
24055 @cindex remote serial stub, main routine
24056 This is the central workhorse, but your program never calls it
24057 explicitly---the setup code arranges for @code{handle_exception} to
24058 run when a trap is triggered.
24060 @code{handle_exception} takes control when your program stops during
24061 execution (for example, on a breakpoint), and mediates communications
24062 with @value{GDBN} on the host machine. This is where the communications
24063 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
24064 representative on the target machine. It begins by sending summary
24065 information on the state of your program, then continues to execute,
24066 retrieving and transmitting any information @value{GDBN} needs, until you
24067 execute a @value{GDBN} command that makes your program resume; at that point,
24068 @code{handle_exception} returns control to your own code on the target
24072 @cindex @code{breakpoint} subroutine, remote
24073 Use this auxiliary subroutine to make your program contain a
24074 breakpoint. Depending on the particular situation, this may be the only
24075 way for @value{GDBN} to get control. For instance, if your target
24076 machine has some sort of interrupt button, you won't need to call this;
24077 pressing the interrupt button transfers control to
24078 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
24079 simply receiving characters on the serial port may also trigger a trap;
24080 again, in that situation, you don't need to call @code{breakpoint} from
24081 your own program---simply running @samp{target remote} from the host
24082 @value{GDBN} session gets control.
24084 Call @code{breakpoint} if none of these is true, or if you simply want
24085 to make certain your program stops at a predetermined point for the
24086 start of your debugging session.
24089 @node Bootstrapping
24090 @subsection What You Must Do for the Stub
24092 @cindex remote stub, support routines
24093 The debugging stubs that come with @value{GDBN} are set up for a particular
24094 chip architecture, but they have no information about the rest of your
24095 debugging target machine.
24097 First of all you need to tell the stub how to communicate with the
24101 @item int getDebugChar()
24102 @findex getDebugChar
24103 Write this subroutine to read a single character from the serial port.
24104 It may be identical to @code{getchar} for your target system; a
24105 different name is used to allow you to distinguish the two if you wish.
24107 @item void putDebugChar(int)
24108 @findex putDebugChar
24109 Write this subroutine to write a single character to the serial port.
24110 It may be identical to @code{putchar} for your target system; a
24111 different name is used to allow you to distinguish the two if you wish.
24114 @cindex control C, and remote debugging
24115 @cindex interrupting remote targets
24116 If you want @value{GDBN} to be able to stop your program while it is
24117 running, you need to use an interrupt-driven serial driver, and arrange
24118 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
24119 character). That is the character which @value{GDBN} uses to tell the
24120 remote system to stop.
24122 Getting the debugging target to return the proper status to @value{GDBN}
24123 probably requires changes to the standard stub; one quick and dirty way
24124 is to just execute a breakpoint instruction (the ``dirty'' part is that
24125 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
24127 Other routines you need to supply are:
24130 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
24131 @findex exceptionHandler
24132 Write this function to install @var{exception_address} in the exception
24133 handling tables. You need to do this because the stub does not have any
24134 way of knowing what the exception handling tables on your target system
24135 are like (for example, the processor's table might be in @sc{rom},
24136 containing entries which point to a table in @sc{ram}).
24137 The @var{exception_number} specifies the exception which should be changed;
24138 its meaning is architecture-dependent (for example, different numbers
24139 might represent divide by zero, misaligned access, etc). When this
24140 exception occurs, control should be transferred directly to
24141 @var{exception_address}, and the processor state (stack, registers,
24142 and so on) should be just as it is when a processor exception occurs. So if
24143 you want to use a jump instruction to reach @var{exception_address}, it
24144 should be a simple jump, not a jump to subroutine.
24146 For the 386, @var{exception_address} should be installed as an interrupt
24147 gate so that interrupts are masked while the handler runs. The gate
24148 should be at privilege level 0 (the most privileged level). The
24149 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
24150 help from @code{exceptionHandler}.
24152 @item void flush_i_cache()
24153 @findex flush_i_cache
24154 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
24155 instruction cache, if any, on your target machine. If there is no
24156 instruction cache, this subroutine may be a no-op.
24158 On target machines that have instruction caches, @value{GDBN} requires this
24159 function to make certain that the state of your program is stable.
24163 You must also make sure this library routine is available:
24166 @item void *memset(void *, int, int)
24168 This is the standard library function @code{memset} that sets an area of
24169 memory to a known value. If you have one of the free versions of
24170 @code{libc.a}, @code{memset} can be found there; otherwise, you must
24171 either obtain it from your hardware manufacturer, or write your own.
24174 If you do not use the GNU C compiler, you may need other standard
24175 library subroutines as well; this varies from one stub to another,
24176 but in general the stubs are likely to use any of the common library
24177 subroutines which @code{@value{NGCC}} generates as inline code.
24180 @node Debug Session
24181 @subsection Putting it All Together
24183 @cindex remote serial debugging summary
24184 In summary, when your program is ready to debug, you must follow these
24189 Make sure you have defined the supporting low-level routines
24190 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
24192 @code{getDebugChar}, @code{putDebugChar},
24193 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
24197 Insert these lines in your program's startup code, before the main
24198 procedure is called:
24205 On some machines, when a breakpoint trap is raised, the hardware
24206 automatically makes the PC point to the instruction after the
24207 breakpoint. If your machine doesn't do that, you may need to adjust
24208 @code{handle_exception} to arrange for it to return to the instruction
24209 after the breakpoint on this first invocation, so that your program
24210 doesn't keep hitting the initial breakpoint instead of making
24214 For the 680x0 stub only, you need to provide a variable called
24215 @code{exceptionHook}. Normally you just use:
24218 void (*exceptionHook)() = 0;
24222 but if before calling @code{set_debug_traps}, you set it to point to a
24223 function in your program, that function is called when
24224 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
24225 error). The function indicated by @code{exceptionHook} is called with
24226 one parameter: an @code{int} which is the exception number.
24229 Compile and link together: your program, the @value{GDBN} debugging stub for
24230 your target architecture, and the supporting subroutines.
24233 Make sure you have a serial connection between your target machine and
24234 the @value{GDBN} host, and identify the serial port on the host.
24237 @c The "remote" target now provides a `load' command, so we should
24238 @c document that. FIXME.
24239 Download your program to your target machine (or get it there by
24240 whatever means the manufacturer provides), and start it.
24243 Start @value{GDBN} on the host, and connect to the target
24244 (@pxref{Connecting,,Connecting to a Remote Target}).
24248 @node Configurations
24249 @chapter Configuration-Specific Information
24251 While nearly all @value{GDBN} commands are available for all native and
24252 cross versions of the debugger, there are some exceptions. This chapter
24253 describes things that are only available in certain configurations.
24255 There are three major categories of configurations: native
24256 configurations, where the host and target are the same, embedded
24257 operating system configurations, which are usually the same for several
24258 different processor architectures, and bare embedded processors, which
24259 are quite different from each other.
24264 * Embedded Processors::
24271 This section describes details specific to particular native
24275 * BSD libkvm Interface:: Debugging BSD kernel memory images
24276 * Process Information:: Process information
24277 * DJGPP Native:: Features specific to the DJGPP port
24278 * Cygwin Native:: Features specific to the Cygwin port
24279 * Hurd Native:: Features specific to @sc{gnu} Hurd
24280 * Darwin:: Features specific to Darwin
24281 * FreeBSD:: Features specific to FreeBSD
24284 @node BSD libkvm Interface
24285 @subsection BSD libkvm Interface
24288 @cindex kernel memory image
24289 @cindex kernel crash dump
24291 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
24292 interface that provides a uniform interface for accessing kernel virtual
24293 memory images, including live systems and crash dumps. @value{GDBN}
24294 uses this interface to allow you to debug live kernels and kernel crash
24295 dumps on many native BSD configurations. This is implemented as a
24296 special @code{kvm} debugging target. For debugging a live system, load
24297 the currently running kernel into @value{GDBN} and connect to the
24301 (@value{GDBP}) @b{target kvm}
24304 For debugging crash dumps, provide the file name of the crash dump as an
24308 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
24311 Once connected to the @code{kvm} target, the following commands are
24317 Set current context from the @dfn{Process Control Block} (PCB) address.
24320 Set current context from proc address. This command isn't available on
24321 modern FreeBSD systems.
24324 @node Process Information
24325 @subsection Process Information
24327 @cindex examine process image
24328 @cindex process info via @file{/proc}
24330 Some operating systems provide interfaces to fetch additional
24331 information about running processes beyond memory and per-thread
24332 register state. If @value{GDBN} is configured for an operating system
24333 with a supported interface, the command @code{info proc} is available
24334 to report information about the process running your program, or about
24335 any process running on your system.
24337 One supported interface is a facility called @samp{/proc} that can be
24338 used to examine the image of a running process using file-system
24339 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24342 On FreeBSD and NetBSD systems, system control nodes are used to query
24343 process information.
24345 In addition, some systems may provide additional process information
24346 in core files. Note that a core file may include a subset of the
24347 information available from a live process. Process information is
24348 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24355 @itemx info proc @var{process-id}
24356 Summarize available information about a process. If a
24357 process ID is specified by @var{process-id}, display information about
24358 that process; otherwise display information about the program being
24359 debugged. The summary includes the debugged process ID, the command
24360 line used to invoke it, its current working directory, and its
24361 executable file's absolute file name.
24363 On some systems, @var{process-id} can be of the form
24364 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24365 within a process. If the optional @var{pid} part is missing, it means
24366 a thread from the process being debugged (the leading @samp{/} still
24367 needs to be present, or else @value{GDBN} will interpret the number as
24368 a process ID rather than a thread ID).
24370 @item info proc cmdline
24371 @cindex info proc cmdline
24372 Show the original command line of the process. This command is
24373 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24375 @item info proc cwd
24376 @cindex info proc cwd
24377 Show the current working directory of the process. This command is
24378 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24380 @item info proc exe
24381 @cindex info proc exe
24382 Show the name of executable of the process. This command is supported
24383 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24385 @item info proc files
24386 @cindex info proc files
24387 Show the file descriptors open by the process. For each open file
24388 descriptor, @value{GDBN} shows its number, type (file, directory,
24389 character device, socket), file pointer offset, and the name of the
24390 resource open on the descriptor. The resource name can be a file name
24391 (for files, directories, and devices) or a protocol followed by socket
24392 address (for network connections). This command is supported on
24395 This example shows the open file descriptors for a process using a
24396 tty for standard input and output as well as two network sockets:
24399 (gdb) info proc files 22136
24403 FD Type Offset Flags Name
24404 text file - r-------- /usr/bin/ssh
24405 ctty chr - rw------- /dev/pts/20
24406 cwd dir - r-------- /usr/home/john
24407 root dir - r-------- /
24408 0 chr 0x32933a4 rw------- /dev/pts/20
24409 1 chr 0x32933a4 rw------- /dev/pts/20
24410 2 chr 0x32933a4 rw------- /dev/pts/20
24411 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24412 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24415 @item info proc mappings
24416 @cindex memory address space mappings
24417 Report the memory address space ranges accessible in a process. On
24418 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24419 on whether the process has read, write, or execute access rights to each
24420 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24421 includes the object file which is mapped to that range.
24423 @item info proc stat
24424 @itemx info proc status
24425 @cindex process detailed status information
24426 Show additional process-related information, including the user ID and
24427 group ID; virtual memory usage; the signals that are pending, blocked,
24428 and ignored; its TTY; its consumption of system and user time; its
24429 stack size; its @samp{nice} value; etc. These commands are supported
24430 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24432 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24433 information (type @kbd{man 5 proc} from your shell prompt).
24435 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24436 @code{info proc status}.
24438 @item info proc all
24439 Show all the information about the process described under all of the
24440 above @code{info proc} subcommands.
24443 @comment These sub-options of 'info proc' were not included when
24444 @comment procfs.c was re-written. Keep their descriptions around
24445 @comment against the day when someone finds the time to put them back in.
24446 @kindex info proc times
24447 @item info proc times
24448 Starting time, user CPU time, and system CPU time for your program and
24451 @kindex info proc id
24453 Report on the process IDs related to your program: its own process ID,
24454 the ID of its parent, the process group ID, and the session ID.
24457 @item set procfs-trace
24458 @kindex set procfs-trace
24459 @cindex @code{procfs} API calls
24460 This command enables and disables tracing of @code{procfs} API calls.
24462 @item show procfs-trace
24463 @kindex show procfs-trace
24464 Show the current state of @code{procfs} API call tracing.
24466 @item set procfs-file @var{file}
24467 @kindex set procfs-file
24468 Tell @value{GDBN} to write @code{procfs} API trace to the named
24469 @var{file}. @value{GDBN} appends the trace info to the previous
24470 contents of the file. The default is to display the trace on the
24473 @item show procfs-file
24474 @kindex show procfs-file
24475 Show the file to which @code{procfs} API trace is written.
24477 @item proc-trace-entry
24478 @itemx proc-trace-exit
24479 @itemx proc-untrace-entry
24480 @itemx proc-untrace-exit
24481 @kindex proc-trace-entry
24482 @kindex proc-trace-exit
24483 @kindex proc-untrace-entry
24484 @kindex proc-untrace-exit
24485 These commands enable and disable tracing of entries into and exits
24486 from the @code{syscall} interface.
24489 @kindex info pidlist
24490 @cindex process list, QNX Neutrino
24491 For QNX Neutrino only, this command displays the list of all the
24492 processes and all the threads within each process.
24495 @kindex info meminfo
24496 @cindex mapinfo list, QNX Neutrino
24497 For QNX Neutrino only, this command displays the list of all mapinfos.
24501 @subsection Features for Debugging @sc{djgpp} Programs
24502 @cindex @sc{djgpp} debugging
24503 @cindex native @sc{djgpp} debugging
24504 @cindex MS-DOS-specific commands
24507 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24508 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24509 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24510 top of real-mode DOS systems and their emulations.
24512 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24513 defines a few commands specific to the @sc{djgpp} port. This
24514 subsection describes those commands.
24519 This is a prefix of @sc{djgpp}-specific commands which print
24520 information about the target system and important OS structures.
24523 @cindex MS-DOS system info
24524 @cindex free memory information (MS-DOS)
24525 @item info dos sysinfo
24526 This command displays assorted information about the underlying
24527 platform: the CPU type and features, the OS version and flavor, the
24528 DPMI version, and the available conventional and DPMI memory.
24533 @cindex segment descriptor tables
24534 @cindex descriptor tables display
24536 @itemx info dos ldt
24537 @itemx info dos idt
24538 These 3 commands display entries from, respectively, Global, Local,
24539 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24540 tables are data structures which store a descriptor for each segment
24541 that is currently in use. The segment's selector is an index into a
24542 descriptor table; the table entry for that index holds the
24543 descriptor's base address and limit, and its attributes and access
24546 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24547 segment (used for both data and the stack), and a DOS segment (which
24548 allows access to DOS/BIOS data structures and absolute addresses in
24549 conventional memory). However, the DPMI host will usually define
24550 additional segments in order to support the DPMI environment.
24552 @cindex garbled pointers
24553 These commands allow to display entries from the descriptor tables.
24554 Without an argument, all entries from the specified table are
24555 displayed. An argument, which should be an integer expression, means
24556 display a single entry whose index is given by the argument. For
24557 example, here's a convenient way to display information about the
24558 debugged program's data segment:
24561 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24562 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24566 This comes in handy when you want to see whether a pointer is outside
24567 the data segment's limit (i.e.@: @dfn{garbled}).
24569 @cindex page tables display (MS-DOS)
24571 @itemx info dos pte
24572 These two commands display entries from, respectively, the Page
24573 Directory and the Page Tables. Page Directories and Page Tables are
24574 data structures which control how virtual memory addresses are mapped
24575 into physical addresses. A Page Table includes an entry for every
24576 page of memory that is mapped into the program's address space; there
24577 may be several Page Tables, each one holding up to 4096 entries. A
24578 Page Directory has up to 4096 entries, one each for every Page Table
24579 that is currently in use.
24581 Without an argument, @kbd{info dos pde} displays the entire Page
24582 Directory, and @kbd{info dos pte} displays all the entries in all of
24583 the Page Tables. An argument, an integer expression, given to the
24584 @kbd{info dos pde} command means display only that entry from the Page
24585 Directory table. An argument given to the @kbd{info dos pte} command
24586 means display entries from a single Page Table, the one pointed to by
24587 the specified entry in the Page Directory.
24589 @cindex direct memory access (DMA) on MS-DOS
24590 These commands are useful when your program uses @dfn{DMA} (Direct
24591 Memory Access), which needs physical addresses to program the DMA
24594 These commands are supported only with some DPMI servers.
24596 @cindex physical address from linear address
24597 @item info dos address-pte @var{addr}
24598 This command displays the Page Table entry for a specified linear
24599 address. The argument @var{addr} is a linear address which should
24600 already have the appropriate segment's base address added to it,
24601 because this command accepts addresses which may belong to @emph{any}
24602 segment. For example, here's how to display the Page Table entry for
24603 the page where a variable @code{i} is stored:
24606 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24607 @exdent @code{Page Table entry for address 0x11a00d30:}
24608 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24612 This says that @code{i} is stored at offset @code{0xd30} from the page
24613 whose physical base address is @code{0x02698000}, and shows all the
24614 attributes of that page.
24616 Note that you must cast the addresses of variables to a @code{char *},
24617 since otherwise the value of @code{__djgpp_base_address}, the base
24618 address of all variables and functions in a @sc{djgpp} program, will
24619 be added using the rules of C pointer arithmetics: if @code{i} is
24620 declared an @code{int}, @value{GDBN} will add 4 times the value of
24621 @code{__djgpp_base_address} to the address of @code{i}.
24623 Here's another example, it displays the Page Table entry for the
24627 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24628 @exdent @code{Page Table entry for address 0x29110:}
24629 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24633 (The @code{+ 3} offset is because the transfer buffer's address is the
24634 3rd member of the @code{_go32_info_block} structure.) The output
24635 clearly shows that this DPMI server maps the addresses in conventional
24636 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24637 linear (@code{0x29110}) addresses are identical.
24639 This command is supported only with some DPMI servers.
24642 @cindex DOS serial data link, remote debugging
24643 In addition to native debugging, the DJGPP port supports remote
24644 debugging via a serial data link. The following commands are specific
24645 to remote serial debugging in the DJGPP port of @value{GDBN}.
24648 @kindex set com1base
24649 @kindex set com1irq
24650 @kindex set com2base
24651 @kindex set com2irq
24652 @kindex set com3base
24653 @kindex set com3irq
24654 @kindex set com4base
24655 @kindex set com4irq
24656 @item set com1base @var{addr}
24657 This command sets the base I/O port address of the @file{COM1} serial
24660 @item set com1irq @var{irq}
24661 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24662 for the @file{COM1} serial port.
24664 There are similar commands @samp{set com2base}, @samp{set com3irq},
24665 etc.@: for setting the port address and the @code{IRQ} lines for the
24668 @kindex show com1base
24669 @kindex show com1irq
24670 @kindex show com2base
24671 @kindex show com2irq
24672 @kindex show com3base
24673 @kindex show com3irq
24674 @kindex show com4base
24675 @kindex show com4irq
24676 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24677 display the current settings of the base address and the @code{IRQ}
24678 lines used by the COM ports.
24681 @kindex info serial
24682 @cindex DOS serial port status
24683 This command prints the status of the 4 DOS serial ports. For each
24684 port, it prints whether it's active or not, its I/O base address and
24685 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24686 counts of various errors encountered so far.
24690 @node Cygwin Native
24691 @subsection Features for Debugging MS Windows PE Executables
24692 @cindex MS Windows debugging
24693 @cindex native Cygwin debugging
24694 @cindex Cygwin-specific commands
24696 @value{GDBN} supports native debugging of MS Windows programs, including
24697 DLLs with and without symbolic debugging information.
24699 @cindex Ctrl-BREAK, MS-Windows
24700 @cindex interrupt debuggee on MS-Windows
24701 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24702 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24703 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24704 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24705 sequence, which can be used to interrupt the debuggee even if it
24708 There are various additional Cygwin-specific commands, described in
24709 this section. Working with DLLs that have no debugging symbols is
24710 described in @ref{Non-debug DLL Symbols}.
24715 This is a prefix of MS Windows-specific commands which print
24716 information about the target system and important OS structures.
24718 @item info w32 selector
24719 This command displays information returned by
24720 the Win32 API @code{GetThreadSelectorEntry} function.
24721 It takes an optional argument that is evaluated to
24722 a long value to give the information about this given selector.
24723 Without argument, this command displays information
24724 about the six segment registers.
24726 @item info w32 thread-information-block
24727 This command displays thread specific information stored in the
24728 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24729 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24731 @kindex signal-event
24732 @item signal-event @var{id}
24733 This command signals an event with user-provided @var{id}. Used to resume
24734 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24736 To use it, create or edit the following keys in
24737 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24738 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24739 (for x86_64 versions):
24743 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24744 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24745 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24747 The first @code{%ld} will be replaced by the process ID of the
24748 crashing process, the second @code{%ld} will be replaced by the ID of
24749 the event that blocks the crashing process, waiting for @value{GDBN}
24753 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24754 make the system run debugger specified by the Debugger key
24755 automatically, @code{0} will cause a dialog box with ``OK'' and
24756 ``Cancel'' buttons to appear, which allows the user to either
24757 terminate the crashing process (OK) or debug it (Cancel).
24760 @kindex set cygwin-exceptions
24761 @cindex debugging the Cygwin DLL
24762 @cindex Cygwin DLL, debugging
24763 @item set cygwin-exceptions @var{mode}
24764 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24765 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24766 @value{GDBN} will delay recognition of exceptions, and may ignore some
24767 exceptions which seem to be caused by internal Cygwin DLL
24768 ``bookkeeping''. This option is meant primarily for debugging the
24769 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24770 @value{GDBN} users with false @code{SIGSEGV} signals.
24772 @kindex show cygwin-exceptions
24773 @item show cygwin-exceptions
24774 Displays whether @value{GDBN} will break on exceptions that happen
24775 inside the Cygwin DLL itself.
24777 @kindex set new-console
24778 @item set new-console @var{mode}
24779 If @var{mode} is @code{on} the debuggee will
24780 be started in a new console on next start.
24781 If @var{mode} is @code{off}, the debuggee will
24782 be started in the same console as the debugger.
24784 @kindex show new-console
24785 @item show new-console
24786 Displays whether a new console is used
24787 when the debuggee is started.
24789 @kindex set new-group
24790 @item set new-group @var{mode}
24791 This boolean value controls whether the debuggee should
24792 start a new group or stay in the same group as the debugger.
24793 This affects the way the Windows OS handles
24796 @kindex show new-group
24797 @item show new-group
24798 Displays current value of new-group boolean.
24800 @kindex set debugevents
24801 @item set debugevents
24802 This boolean value adds debug output concerning kernel events related
24803 to the debuggee seen by the debugger. This includes events that
24804 signal thread and process creation and exit, DLL loading and
24805 unloading, console interrupts, and debugging messages produced by the
24806 Windows @code{OutputDebugString} API call.
24808 @kindex set debugexec
24809 @item set debugexec
24810 This boolean value adds debug output concerning execute events
24811 (such as resume thread) seen by the debugger.
24813 @kindex set debugexceptions
24814 @item set debugexceptions
24815 This boolean value adds debug output concerning exceptions in the
24816 debuggee seen by the debugger.
24818 @kindex set debugmemory
24819 @item set debugmemory
24820 This boolean value adds debug output concerning debuggee memory reads
24821 and writes by the debugger.
24825 This boolean values specifies whether the debuggee is called
24826 via a shell or directly (default value is on).
24830 Displays if the debuggee will be started with a shell.
24835 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24838 @node Non-debug DLL Symbols
24839 @subsubsection Support for DLLs without Debugging Symbols
24840 @cindex DLLs with no debugging symbols
24841 @cindex Minimal symbols and DLLs
24843 Very often on windows, some of the DLLs that your program relies on do
24844 not include symbolic debugging information (for example,
24845 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24846 symbols in a DLL, it relies on the minimal amount of symbolic
24847 information contained in the DLL's export table. This section
24848 describes working with such symbols, known internally to @value{GDBN} as
24849 ``minimal symbols''.
24851 Note that before the debugged program has started execution, no DLLs
24852 will have been loaded. The easiest way around this problem is simply to
24853 start the program --- either by setting a breakpoint or letting the
24854 program run once to completion.
24856 @subsubsection DLL Name Prefixes
24858 In keeping with the naming conventions used by the Microsoft debugging
24859 tools, DLL export symbols are made available with a prefix based on the
24860 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24861 also entered into the symbol table, so @code{CreateFileA} is often
24862 sufficient. In some cases there will be name clashes within a program
24863 (particularly if the executable itself includes full debugging symbols)
24864 necessitating the use of the fully qualified name when referring to the
24865 contents of the DLL. Use single-quotes around the name to avoid the
24866 exclamation mark (``!'') being interpreted as a language operator.
24868 Note that the internal name of the DLL may be all upper-case, even
24869 though the file name of the DLL is lower-case, or vice-versa. Since
24870 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24871 some confusion. If in doubt, try the @code{info functions} and
24872 @code{info variables} commands or even @code{maint print msymbols}
24873 (@pxref{Symbols}). Here's an example:
24876 (@value{GDBP}) info function CreateFileA
24877 All functions matching regular expression "CreateFileA":
24879 Non-debugging symbols:
24880 0x77e885f4 CreateFileA
24881 0x77e885f4 KERNEL32!CreateFileA
24885 (@value{GDBP}) info function !
24886 All functions matching regular expression "!":
24888 Non-debugging symbols:
24889 0x6100114c cygwin1!__assert
24890 0x61004034 cygwin1!_dll_crt0@@0
24891 0x61004240 cygwin1!dll_crt0(per_process *)
24895 @subsubsection Working with Minimal Symbols
24897 Symbols extracted from a DLL's export table do not contain very much
24898 type information. All that @value{GDBN} can do is guess whether a symbol
24899 refers to a function or variable depending on the linker section that
24900 contains the symbol. Also note that the actual contents of the memory
24901 contained in a DLL are not available unless the program is running. This
24902 means that you cannot examine the contents of a variable or disassemble
24903 a function within a DLL without a running program.
24905 Variables are generally treated as pointers and dereferenced
24906 automatically. For this reason, it is often necessary to prefix a
24907 variable name with the address-of operator (``&'') and provide explicit
24908 type information in the command. Here's an example of the type of
24912 (@value{GDBP}) print 'cygwin1!__argv'
24913 'cygwin1!__argv' has unknown type; cast it to its declared type
24917 (@value{GDBP}) x 'cygwin1!__argv'
24918 'cygwin1!__argv' has unknown type; cast it to its declared type
24921 And two possible solutions:
24924 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24925 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24929 (@value{GDBP}) x/2x &'cygwin1!__argv'
24930 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24931 (@value{GDBP}) x/x 0x10021608
24932 0x10021608: 0x0022fd98
24933 (@value{GDBP}) x/s 0x0022fd98
24934 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24937 Setting a break point within a DLL is possible even before the program
24938 starts execution. However, under these circumstances, @value{GDBN} can't
24939 examine the initial instructions of the function in order to skip the
24940 function's frame set-up code. You can work around this by using ``*&''
24941 to set the breakpoint at a raw memory address:
24944 (@value{GDBP}) break *&'python22!PyOS_Readline'
24945 Breakpoint 1 at 0x1e04eff0
24948 The author of these extensions is not entirely convinced that setting a
24949 break point within a shared DLL like @file{kernel32.dll} is completely
24953 @subsection Commands Specific to @sc{gnu} Hurd Systems
24954 @cindex @sc{gnu} Hurd debugging
24956 This subsection describes @value{GDBN} commands specific to the
24957 @sc{gnu} Hurd native debugging.
24962 @kindex set signals@r{, Hurd command}
24963 @kindex set sigs@r{, Hurd command}
24964 This command toggles the state of inferior signal interception by
24965 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24966 affected by this command. @code{sigs} is a shorthand alias for
24971 @kindex show signals@r{, Hurd command}
24972 @kindex show sigs@r{, Hurd command}
24973 Show the current state of intercepting inferior's signals.
24975 @item set signal-thread
24976 @itemx set sigthread
24977 @kindex set signal-thread
24978 @kindex set sigthread
24979 This command tells @value{GDBN} which thread is the @code{libc} signal
24980 thread. That thread is run when a signal is delivered to a running
24981 process. @code{set sigthread} is the shorthand alias of @code{set
24984 @item show signal-thread
24985 @itemx show sigthread
24986 @kindex show signal-thread
24987 @kindex show sigthread
24988 These two commands show which thread will run when the inferior is
24989 delivered a signal.
24992 @kindex set stopped@r{, Hurd command}
24993 This commands tells @value{GDBN} that the inferior process is stopped,
24994 as with the @code{SIGSTOP} signal. The stopped process can be
24995 continued by delivering a signal to it.
24998 @kindex show stopped@r{, Hurd command}
24999 This command shows whether @value{GDBN} thinks the debuggee is
25002 @item set exceptions
25003 @kindex set exceptions@r{, Hurd command}
25004 Use this command to turn off trapping of exceptions in the inferior.
25005 When exception trapping is off, neither breakpoints nor
25006 single-stepping will work. To restore the default, set exception
25009 @item show exceptions
25010 @kindex show exceptions@r{, Hurd command}
25011 Show the current state of trapping exceptions in the inferior.
25013 @item set task pause
25014 @kindex set task@r{, Hurd commands}
25015 @cindex task attributes (@sc{gnu} Hurd)
25016 @cindex pause current task (@sc{gnu} Hurd)
25017 This command toggles task suspension when @value{GDBN} has control.
25018 Setting it to on takes effect immediately, and the task is suspended
25019 whenever @value{GDBN} gets control. Setting it to off will take
25020 effect the next time the inferior is continued. If this option is set
25021 to off, you can use @code{set thread default pause on} or @code{set
25022 thread pause on} (see below) to pause individual threads.
25024 @item show task pause
25025 @kindex show task@r{, Hurd commands}
25026 Show the current state of task suspension.
25028 @item set task detach-suspend-count
25029 @cindex task suspend count
25030 @cindex detach from task, @sc{gnu} Hurd
25031 This command sets the suspend count the task will be left with when
25032 @value{GDBN} detaches from it.
25034 @item show task detach-suspend-count
25035 Show the suspend count the task will be left with when detaching.
25037 @item set task exception-port
25038 @itemx set task excp
25039 @cindex task exception port, @sc{gnu} Hurd
25040 This command sets the task exception port to which @value{GDBN} will
25041 forward exceptions. The argument should be the value of the @dfn{send
25042 rights} of the task. @code{set task excp} is a shorthand alias.
25044 @item set noninvasive
25045 @cindex noninvasive task options
25046 This command switches @value{GDBN} to a mode that is the least
25047 invasive as far as interfering with the inferior is concerned. This
25048 is the same as using @code{set task pause}, @code{set exceptions}, and
25049 @code{set signals} to values opposite to the defaults.
25051 @item info send-rights
25052 @itemx info receive-rights
25053 @itemx info port-rights
25054 @itemx info port-sets
25055 @itemx info dead-names
25058 @cindex send rights, @sc{gnu} Hurd
25059 @cindex receive rights, @sc{gnu} Hurd
25060 @cindex port rights, @sc{gnu} Hurd
25061 @cindex port sets, @sc{gnu} Hurd
25062 @cindex dead names, @sc{gnu} Hurd
25063 These commands display information about, respectively, send rights,
25064 receive rights, port rights, port sets, and dead names of a task.
25065 There are also shorthand aliases: @code{info ports} for @code{info
25066 port-rights} and @code{info psets} for @code{info port-sets}.
25068 @item set thread pause
25069 @kindex set thread@r{, Hurd command}
25070 @cindex thread properties, @sc{gnu} Hurd
25071 @cindex pause current thread (@sc{gnu} Hurd)
25072 This command toggles current thread suspension when @value{GDBN} has
25073 control. Setting it to on takes effect immediately, and the current
25074 thread is suspended whenever @value{GDBN} gets control. Setting it to
25075 off will take effect the next time the inferior is continued.
25076 Normally, this command has no effect, since when @value{GDBN} has
25077 control, the whole task is suspended. However, if you used @code{set
25078 task pause off} (see above), this command comes in handy to suspend
25079 only the current thread.
25081 @item show thread pause
25082 @kindex show thread@r{, Hurd command}
25083 This command shows the state of current thread suspension.
25085 @item set thread run
25086 This command sets whether the current thread is allowed to run.
25088 @item show thread run
25089 Show whether the current thread is allowed to run.
25091 @item set thread detach-suspend-count
25092 @cindex thread suspend count, @sc{gnu} Hurd
25093 @cindex detach from thread, @sc{gnu} Hurd
25094 This command sets the suspend count @value{GDBN} will leave on a
25095 thread when detaching. This number is relative to the suspend count
25096 found by @value{GDBN} when it notices the thread; use @code{set thread
25097 takeover-suspend-count} to force it to an absolute value.
25099 @item show thread detach-suspend-count
25100 Show the suspend count @value{GDBN} will leave on the thread when
25103 @item set thread exception-port
25104 @itemx set thread excp
25105 Set the thread exception port to which to forward exceptions. This
25106 overrides the port set by @code{set task exception-port} (see above).
25107 @code{set thread excp} is the shorthand alias.
25109 @item set thread takeover-suspend-count
25110 Normally, @value{GDBN}'s thread suspend counts are relative to the
25111 value @value{GDBN} finds when it notices each thread. This command
25112 changes the suspend counts to be absolute instead.
25114 @item set thread default
25115 @itemx show thread default
25116 @cindex thread default settings, @sc{gnu} Hurd
25117 Each of the above @code{set thread} commands has a @code{set thread
25118 default} counterpart (e.g., @code{set thread default pause}, @code{set
25119 thread default exception-port}, etc.). The @code{thread default}
25120 variety of commands sets the default thread properties for all
25121 threads; you can then change the properties of individual threads with
25122 the non-default commands.
25129 @value{GDBN} provides the following commands specific to the Darwin target:
25132 @item set debug darwin @var{num}
25133 @kindex set debug darwin
25134 When set to a non zero value, enables debugging messages specific to
25135 the Darwin support. Higher values produce more verbose output.
25137 @item show debug darwin
25138 @kindex show debug darwin
25139 Show the current state of Darwin messages.
25141 @item set debug mach-o @var{num}
25142 @kindex set debug mach-o
25143 When set to a non zero value, enables debugging messages while
25144 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
25145 file format used on Darwin for object and executable files.) Higher
25146 values produce more verbose output. This is a command to diagnose
25147 problems internal to @value{GDBN} and should not be needed in normal
25150 @item show debug mach-o
25151 @kindex show debug mach-o
25152 Show the current state of Mach-O file messages.
25154 @item set mach-exceptions on
25155 @itemx set mach-exceptions off
25156 @kindex set mach-exceptions
25157 On Darwin, faults are first reported as a Mach exception and are then
25158 mapped to a Posix signal. Use this command to turn on trapping of
25159 Mach exceptions in the inferior. This might be sometimes useful to
25160 better understand the cause of a fault. The default is off.
25162 @item show mach-exceptions
25163 @kindex show mach-exceptions
25164 Show the current state of exceptions trapping.
25168 @subsection FreeBSD
25171 When the ABI of a system call is changed in the FreeBSD kernel, this
25172 is implemented by leaving a compatibility system call using the old
25173 ABI at the existing number and allocating a new system call number for
25174 the version using the new ABI. As a convenience, when a system call
25175 is caught by name (@pxref{catch syscall}), compatibility system calls
25178 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
25179 system call and catching the @code{kevent} system call by name catches
25183 (@value{GDBP}) catch syscall kevent
25184 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
25190 @section Embedded Operating Systems
25192 This section describes configurations involving the debugging of
25193 embedded operating systems that are available for several different
25196 @value{GDBN} includes the ability to debug programs running on
25197 various real-time operating systems.
25199 @node Embedded Processors
25200 @section Embedded Processors
25202 This section goes into details specific to particular embedded
25205 @cindex send command to simulator
25206 Whenever a specific embedded processor has a simulator, @value{GDBN}
25207 allows to send an arbitrary command to the simulator.
25210 @item sim @var{command}
25211 @kindex sim@r{, a command}
25212 Send an arbitrary @var{command} string to the simulator. Consult the
25213 documentation for the specific simulator in use for information about
25214 acceptable commands.
25219 * ARC:: Synopsys ARC
25222 * M68K:: Motorola M68K
25223 * MicroBlaze:: Xilinx MicroBlaze
25224 * MIPS Embedded:: MIPS Embedded
25225 * OpenRISC 1000:: OpenRISC 1000 (or1k)
25226 * PowerPC Embedded:: PowerPC Embedded
25229 * Super-H:: Renesas Super-H
25233 @subsection Synopsys ARC
25234 @cindex Synopsys ARC
25235 @cindex ARC specific commands
25241 @value{GDBN} provides the following ARC-specific commands:
25244 @item set debug arc
25245 @kindex set debug arc
25246 Control the level of ARC specific debug messages. Use 0 for no messages (the
25247 default), 1 for debug messages, and 2 for even more debug messages.
25249 @item show debug arc
25250 @kindex show debug arc
25251 Show the level of ARC specific debugging in operation.
25253 @item maint print arc arc-instruction @var{address}
25254 @kindex maint print arc arc-instruction
25255 Print internal disassembler information about instruction at a given address.
25262 @value{GDBN} provides the following ARM-specific commands:
25265 @item set arm disassembler
25267 This commands selects from a list of disassembly styles. The
25268 @code{"std"} style is the standard style.
25270 @item show arm disassembler
25272 Show the current disassembly style.
25274 @item set arm apcs32
25275 @cindex ARM 32-bit mode
25276 This command toggles ARM operation mode between 32-bit and 26-bit.
25278 @item show arm apcs32
25279 Display the current usage of the ARM 32-bit mode.
25281 @item set arm fpu @var{fputype}
25282 This command sets the ARM floating-point unit (FPU) type. The
25283 argument @var{fputype} can be one of these:
25287 Determine the FPU type by querying the OS ABI.
25289 Software FPU, with mixed-endian doubles on little-endian ARM
25292 GCC-compiled FPA co-processor.
25294 Software FPU with pure-endian doubles.
25300 Show the current type of the FPU.
25303 This command forces @value{GDBN} to use the specified ABI.
25306 Show the currently used ABI.
25308 @item set arm fallback-mode (arm|thumb|auto)
25309 @value{GDBN} uses the symbol table, when available, to determine
25310 whether instructions are ARM or Thumb. This command controls
25311 @value{GDBN}'s default behavior when the symbol table is not
25312 available. The default is @samp{auto}, which causes @value{GDBN} to
25313 use the current execution mode (from the @code{T} bit in the @code{CPSR}
25316 @item show arm fallback-mode
25317 Show the current fallback instruction mode.
25319 @item set arm force-mode (arm|thumb|auto)
25320 This command overrides use of the symbol table to determine whether
25321 instructions are ARM or Thumb. The default is @samp{auto}, which
25322 causes @value{GDBN} to use the symbol table and then the setting
25323 of @samp{set arm fallback-mode}.
25325 @item show arm force-mode
25326 Show the current forced instruction mode.
25328 @item set arm unwind-secure-frames
25329 This command enables unwinding from Non-secure to Secure mode on
25330 Cortex-M with Security extension.
25331 This can trigger security exceptions when unwinding the exception
25333 It is enabled by default.
25335 @item show arm unwind-secure-frames
25336 Show whether unwinding from Non-secure to Secure mode is enabled.
25338 @item set debug arm
25339 Toggle whether to display ARM-specific debugging messages from the ARM
25340 target support subsystem.
25342 @item show debug arm
25343 Show whether ARM-specific debugging messages are enabled.
25347 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25348 The @value{GDBN} ARM simulator accepts the following optional arguments.
25351 @item --swi-support=@var{type}
25352 Tell the simulator which SWI interfaces to support. The argument
25353 @var{type} may be a comma separated list of the following values.
25354 The default value is @code{all}.
25370 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25371 The @value{GDBN} BPF simulator accepts the following optional arguments.
25374 @item --skb-data-offset=@var{offset}
25375 Tell the simulator the offset, measured in bytes, of the
25376 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25377 This offset is used by some BPF specific-purpose load/store
25378 instructions. Defaults to 0.
25385 The Motorola m68k configuration includes ColdFire support.
25388 @subsection MicroBlaze
25389 @cindex Xilinx MicroBlaze
25390 @cindex XMD, Xilinx Microprocessor Debugger
25392 The MicroBlaze is a soft-core processor supported on various Xilinx
25393 FPGAs, such as Spartan or Virtex series. Boards with these processors
25394 usually have JTAG ports which connect to a host system running the Xilinx
25395 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25396 This host system is used to download the configuration bitstream to
25397 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25398 communicates with the target board using the JTAG interface and
25399 presents a @code{gdbserver} interface to the board. By default
25400 @code{xmd} uses port @code{1234}. (While it is possible to change
25401 this default port, it requires the use of undocumented @code{xmd}
25402 commands. Contact Xilinx support if you need to do this.)
25404 Use these GDB commands to connect to the MicroBlaze target processor.
25407 @item target remote :1234
25408 Use this command to connect to the target if you are running @value{GDBN}
25409 on the same system as @code{xmd}.
25411 @item target remote @var{xmd-host}:1234
25412 Use this command to connect to the target if it is connected to @code{xmd}
25413 running on a different system named @var{xmd-host}.
25416 Use this command to download a program to the MicroBlaze target.
25418 @item set debug microblaze @var{n}
25419 Enable MicroBlaze-specific debugging messages if non-zero.
25421 @item show debug microblaze @var{n}
25422 Show MicroBlaze-specific debugging level.
25425 @node MIPS Embedded
25426 @subsection @acronym{MIPS} Embedded
25429 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25432 @item set mipsfpu double
25433 @itemx set mipsfpu single
25434 @itemx set mipsfpu none
25435 @itemx set mipsfpu auto
25436 @itemx show mipsfpu
25437 @kindex set mipsfpu
25438 @kindex show mipsfpu
25439 @cindex @acronym{MIPS} remote floating point
25440 @cindex floating point, @acronym{MIPS} remote
25441 If your target board does not support the @acronym{MIPS} floating point
25442 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25443 need this, you may wish to put the command in your @value{GDBN} init
25444 file). This tells @value{GDBN} how to find the return value of
25445 functions which return floating point values. It also allows
25446 @value{GDBN} to avoid saving the floating point registers when calling
25447 functions on the board. If you are using a floating point coprocessor
25448 with only single precision floating point support, as on the @sc{r4650}
25449 processor, use the command @samp{set mipsfpu single}. The default
25450 double precision floating point coprocessor may be selected using
25451 @samp{set mipsfpu double}.
25453 In previous versions the only choices were double precision or no
25454 floating point, so @samp{set mipsfpu on} will select double precision
25455 and @samp{set mipsfpu off} will select no floating point.
25457 As usual, you can inquire about the @code{mipsfpu} variable with
25458 @samp{show mipsfpu}.
25461 @node OpenRISC 1000
25462 @subsection OpenRISC 1000
25463 @cindex OpenRISC 1000
25466 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25467 mainly provided as a soft-core which can run on Xilinx, Altera and other
25470 @value{GDBN} for OpenRISC supports the below commands when connecting to
25478 Runs the builtin CPU simulator which can run very basic
25479 programs but does not support most hardware functions like MMU.
25480 For more complex use cases the user is advised to run an external
25481 target, and connect using @samp{target remote}.
25483 Example: @code{target sim}
25485 @item set debug or1k
25486 Toggle whether to display OpenRISC-specific debugging messages from the
25487 OpenRISC target support subsystem.
25489 @item show debug or1k
25490 Show whether OpenRISC-specific debugging messages are enabled.
25493 @node PowerPC Embedded
25494 @subsection PowerPC Embedded
25496 @cindex DVC register
25497 @value{GDBN} supports using the DVC (Data Value Compare) register to
25498 implement in hardware simple hardware watchpoint conditions of the form:
25501 (@value{GDBP}) watch @var{address|variable} \
25502 if @var{address|variable} == @var{constant expression}
25505 The DVC register will be automatically used when @value{GDBN} detects
25506 such pattern in a condition expression, and the created watchpoint uses one
25507 debug register (either the @code{exact-watchpoints} option is on and the
25508 variable is scalar, or the variable has a length of one byte). This feature
25509 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25512 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25513 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25514 in which case watchpoints using only one debug register are created when
25515 watching variables of scalar types.
25517 You can create an artificial array to watch an arbitrary memory
25518 region using one of the following commands (@pxref{Expressions}):
25521 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25522 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25525 PowerPC embedded processors support masked watchpoints. See the discussion
25526 about the @code{mask} argument in @ref{Set Watchpoints}.
25528 @cindex ranged breakpoint
25529 PowerPC embedded processors support hardware accelerated
25530 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25531 the inferior whenever it executes an instruction at any address within
25532 the range it was set at. To set a ranged breakpoint in @value{GDBN},
25533 use the @code{break-range} command.
25535 @value{GDBN} provides the following PowerPC-specific commands:
25538 @kindex break-range
25539 @item break-range @var{start-locspec}, @var{end-locspec}
25540 Set a breakpoint for an address range given by @var{start-locspec} and
25541 @var{end-locspec}, which are location specs. @xref{Location
25542 Specifications}, for a list of all the possible forms of location
25543 specs. @value{GDBN} resolves both @var{start-locspec} and
25544 @var{end-locspec}, and uses the addresses of the resolved code
25545 locations as start and end addresses of the range to break at. The
25546 breakpoint will stop execution of the inferior whenever it executes an
25547 instruction at any address between the start and end addresses,
25548 inclusive. If either @var{start-locspec} or @var{end-locspec} resolve
25549 to multiple code locations in the program, then the command aborts
25550 with an error without creating a breakpoint.
25552 @kindex set powerpc
25553 @item set powerpc soft-float
25554 @itemx show powerpc soft-float
25555 Force @value{GDBN} to use (or not use) a software floating point calling
25556 convention. By default, @value{GDBN} selects the calling convention based
25557 on the selected architecture and the provided executable file.
25559 @item set powerpc vector-abi
25560 @itemx show powerpc vector-abi
25561 Force @value{GDBN} to use the specified calling convention for vector
25562 arguments and return values. The valid options are @samp{auto};
25563 @samp{generic}, to avoid vector registers even if they are present;
25564 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25565 registers. By default, @value{GDBN} selects the calling convention
25566 based on the selected architecture and the provided executable file.
25568 @item set powerpc exact-watchpoints
25569 @itemx show powerpc exact-watchpoints
25570 Allow @value{GDBN} to use only one debug register when watching a variable
25571 of scalar type, thus assuming that the variable is accessed through the
25572 address of its first byte.
25577 @subsection Atmel AVR
25580 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25581 following AVR-specific commands:
25584 @item info io_registers
25585 @kindex info io_registers@r{, AVR}
25586 @cindex I/O registers (Atmel AVR)
25587 This command displays information about the AVR I/O registers. For
25588 each register, @value{GDBN} prints its number and value.
25595 When configured for debugging CRIS, @value{GDBN} provides the
25596 following CRIS-specific commands:
25599 @item set cris-version @var{ver}
25600 @cindex CRIS version
25601 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25602 The CRIS version affects register names and sizes. This command is useful in
25603 case autodetection of the CRIS version fails.
25605 @item show cris-version
25606 Show the current CRIS version.
25608 @item set cris-dwarf2-cfi
25609 @cindex DWARF-2 CFI and CRIS
25610 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25611 Change to @samp{off} when using @code{gcc-cris} whose version is below
25614 @item show cris-dwarf2-cfi
25615 Show the current state of using DWARF-2 CFI.
25617 @item set cris-mode @var{mode}
25619 Set the current CRIS mode to @var{mode}. It should only be changed when
25620 debugging in guru mode, in which case it should be set to
25621 @samp{guru} (the default is @samp{normal}).
25623 @item show cris-mode
25624 Show the current CRIS mode.
25628 @subsection Renesas Super-H
25631 For the Renesas Super-H processor, @value{GDBN} provides these
25635 @item set sh calling-convention @var{convention}
25636 @kindex set sh calling-convention
25637 Set the calling-convention used when calling functions from @value{GDBN}.
25638 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25639 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25640 convention. If the DWARF-2 information of the called function specifies
25641 that the function follows the Renesas calling convention, the function
25642 is called using the Renesas calling convention. If the calling convention
25643 is set to @samp{renesas}, the Renesas calling convention is always used,
25644 regardless of the DWARF-2 information. This can be used to override the
25645 default of @samp{gcc} if debug information is missing, or the compiler
25646 does not emit the DWARF-2 calling convention entry for a function.
25648 @item show sh calling-convention
25649 @kindex show sh calling-convention
25650 Show the current calling convention setting.
25655 @node Architectures
25656 @section Architectures
25658 This section describes characteristics of architectures that affect
25659 all uses of @value{GDBN} with the architecture, both native and cross.
25666 * HPPA:: HP PA architecture
25674 @subsection AArch64
25675 @cindex AArch64 support
25677 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25678 following special commands:
25681 @item set debug aarch64
25682 @kindex set debug aarch64
25683 This command determines whether AArch64 architecture-specific debugging
25684 messages are to be displayed.
25686 @item show debug aarch64
25687 Show whether AArch64 debugging messages are displayed.
25691 @subsubsection AArch64 SVE.
25692 @cindex AArch64 SVE.
25694 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25695 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25696 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25697 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25698 @code{$vg} will be provided. This is the vector granule for the current thread
25699 and represents the number of 64-bit chunks in an SVE @code{z} register.
25701 If the vector length changes, then the @code{$vg} register will be updated,
25702 but the lengths of the @code{z} and @code{p} registers will not change. This
25703 is a known limitation of @value{GDBN} and does not affect the execution of the
25706 @subsubsection AArch64 Pointer Authentication.
25707 @cindex AArch64 Pointer Authentication.
25708 @anchor{AArch64 PAC}
25710 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25711 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25712 register @code{$lr} is pointing to an PAC function its value will be masked.
25713 When GDB prints a backtrace, any addresses that required unmasking will be
25714 postfixed with the marker [PAC]. When using the MI, this is printed as part
25715 of the @code{addr_flags} field.
25717 @subsubsection AArch64 Memory Tagging Extension.
25718 @cindex AArch64 Memory Tagging Extension.
25720 When @value{GDBN} is debugging the AArch64 architecture, the program is
25721 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25722 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25723 available for inspection and editing of logical and allocation tags.
25724 @xref{Memory Tagging}.
25726 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25727 signals are generated as a result of memory tag failures.
25729 If the tag violation is synchronous, the following will be shown:
25732 Program received signal SIGSEGV, Segmentation fault
25733 Memory tag violation while accessing address 0x0500fffff7ff8000
25738 If the tag violation is asynchronous, the fault address is not available.
25739 In this case @value{GDBN} will show the following:
25742 Program received signal SIGSEGV, Segmentation fault
25743 Memory tag violation
25744 Fault address unavailable.
25747 A special register, @code{tag_ctl}, is made available through the
25748 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25749 options that can be controlled at runtime and emulates the @code{prctl}
25750 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25751 documentation in the Linux kernel.
25754 @subsection x86 Architecture-specific Issues
25757 @item set struct-convention @var{mode}
25758 @kindex set struct-convention
25759 @cindex struct return convention
25760 @cindex struct/union returned in registers
25761 Set the convention used by the inferior to return @code{struct}s and
25762 @code{union}s from functions to @var{mode}. Possible values of
25763 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25764 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25765 are returned on the stack, while @code{"reg"} means that a
25766 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25767 be returned in a register.
25769 @item show struct-convention
25770 @kindex show struct-convention
25771 Show the current setting of the convention to return @code{struct}s
25776 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25777 @cindex Intel Memory Protection Extensions (MPX).
25779 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25780 @footnote{The register named with capital letters represent the architecture
25781 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25782 which are the lower bound and upper bound. Bounds are effective addresses or
25783 memory locations. The upper bounds are architecturally represented in 1's
25784 complement form. A bound having lower bound = 0, and upper bound = 0
25785 (1's complement of all bits set) will allow access to the entire address space.
25787 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25788 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25789 display the upper bound performing the complement of one operation on the
25790 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25791 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25792 can also be noted that the upper bounds are inclusive.
25794 As an example, assume that the register BND0 holds bounds for a pointer having
25795 access allowed for the range between 0x32 and 0x71. The values present on
25796 bnd0raw and bnd registers are presented as follows:
25799 bnd0raw = @{0x32, 0xffffffff8e@}
25800 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25803 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25804 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25805 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25806 Python, the display includes the memory size, in bits, accessible to
25809 Bounds can also be stored in bounds tables, which are stored in
25810 application memory. These tables store bounds for pointers by specifying
25811 the bounds pointer's value along with its bounds. Evaluating and changing
25812 bounds located in bound tables is therefore interesting while investigating
25813 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25816 @item show mpx bound @var{pointer}
25817 @kindex show mpx bound
25818 Display bounds of the given @var{pointer}.
25820 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25821 @kindex set mpx bound
25822 Set the bounds of a pointer in the bound table.
25823 This command takes three parameters: @var{pointer} is the pointers
25824 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25825 for lower and upper bounds respectively.
25828 When you call an inferior function on an Intel MPX enabled program,
25829 GDB sets the inferior's bound registers to the init (disabled) state
25830 before calling the function. As a consequence, bounds checks for the
25831 pointer arguments passed to the function will always pass.
25833 This is necessary because when you call an inferior function, the
25834 program is usually in the middle of the execution of other function.
25835 Since at that point bound registers are in an arbitrary state, not
25836 clearing them would lead to random bound violations in the called
25839 You can still examine the influence of the bound registers on the
25840 execution of the called function by stopping the execution of the
25841 called function at its prologue, setting bound registers, and
25842 continuing the execution. For example:
25846 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25847 $ print upper (a, b, c, d, 1)
25848 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25850 @{lbound = 0x0, ubound = ffffffff@} : size -1
25853 At this last step the value of bnd0 can be changed for investigation of bound
25854 violations caused along the execution of the call. In order to know how to
25855 set the bound registers or bound table for the call consult the ABI.
25860 See the following section.
25863 @subsection @acronym{MIPS}
25865 @cindex stack on Alpha
25866 @cindex stack on @acronym{MIPS}
25867 @cindex Alpha stack
25868 @cindex @acronym{MIPS} stack
25869 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25870 sometimes requires @value{GDBN} to search backward in the object code to
25871 find the beginning of a function.
25873 @cindex response time, @acronym{MIPS} debugging
25874 To improve response time (especially for embedded applications, where
25875 @value{GDBN} may be restricted to a slow serial line for this search)
25876 you may want to limit the size of this search, using one of these
25880 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25881 @item set heuristic-fence-post @var{limit}
25882 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25883 search for the beginning of a function. A value of @var{0} (the
25884 default) means there is no limit. However, except for @var{0}, the
25885 larger the limit the more bytes @code{heuristic-fence-post} must search
25886 and therefore the longer it takes to run. You should only need to use
25887 this command when debugging a stripped executable.
25889 @item show heuristic-fence-post
25890 Display the current limit.
25894 These commands are available @emph{only} when @value{GDBN} is configured
25895 for debugging programs on Alpha or @acronym{MIPS} processors.
25897 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25901 @item set mips abi @var{arg}
25902 @kindex set mips abi
25903 @cindex set ABI for @acronym{MIPS}
25904 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25905 values of @var{arg} are:
25909 The default ABI associated with the current binary (this is the
25919 @item show mips abi
25920 @kindex show mips abi
25921 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25923 @item set mips compression @var{arg}
25924 @kindex set mips compression
25925 @cindex code compression, @acronym{MIPS}
25926 Tell @value{GDBN} which @acronym{MIPS} compressed
25927 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25928 inferior. @value{GDBN} uses this for code disassembly and other
25929 internal interpretation purposes. This setting is only referred to
25930 when no executable has been associated with the debugging session or
25931 the executable does not provide information about the encoding it uses.
25932 Otherwise this setting is automatically updated from information
25933 provided by the executable.
25935 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25936 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25937 executables containing @acronym{MIPS16} code frequently are not
25938 identified as such.
25940 This setting is ``sticky''; that is, it retains its value across
25941 debugging sessions until reset either explicitly with this command or
25942 implicitly from an executable.
25944 The compiler and/or assembler typically add symbol table annotations to
25945 identify functions compiled for the @acronym{MIPS16} or
25946 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25947 are present, @value{GDBN} uses them in preference to the global
25948 compressed @acronym{ISA} encoding setting.
25950 @item show mips compression
25951 @kindex show mips compression
25952 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25953 @value{GDBN} to debug the inferior.
25956 @itemx show mipsfpu
25957 @xref{MIPS Embedded, set mipsfpu}.
25959 @item set mips mask-address @var{arg}
25960 @kindex set mips mask-address
25961 @cindex @acronym{MIPS} addresses, masking
25962 This command determines whether the most-significant 32 bits of 64-bit
25963 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25964 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25965 setting, which lets @value{GDBN} determine the correct value.
25967 @item show mips mask-address
25968 @kindex show mips mask-address
25969 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25972 @item set remote-mips64-transfers-32bit-regs
25973 @kindex set remote-mips64-transfers-32bit-regs
25974 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25975 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25976 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25977 and 64 bits for other registers, set this option to @samp{on}.
25979 @item show remote-mips64-transfers-32bit-regs
25980 @kindex show remote-mips64-transfers-32bit-regs
25981 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25983 @item set debug mips
25984 @kindex set debug mips
25985 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25986 target code in @value{GDBN}.
25988 @item show debug mips
25989 @kindex show debug mips
25990 Show the current setting of @acronym{MIPS} debugging messages.
25996 @cindex HPPA support
25998 When @value{GDBN} is debugging the HP PA architecture, it provides the
25999 following special commands:
26002 @item set debug hppa
26003 @kindex set debug hppa
26004 This command determines whether HPPA architecture-specific debugging
26005 messages are to be displayed.
26007 @item show debug hppa
26008 Show whether HPPA debugging messages are displayed.
26010 @item maint print unwind @var{address}
26011 @kindex maint print unwind@r{, HPPA}
26012 This command displays the contents of the unwind table entry at the
26013 given @var{address}.
26019 @subsection PowerPC
26020 @cindex PowerPC architecture
26022 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
26023 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
26024 numbers stored in the floating point registers. These values must be stored
26025 in two consecutive registers, always starting at an even register like
26026 @code{f0} or @code{f2}.
26028 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
26029 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
26030 @code{f2} and @code{f3} for @code{$dl1} and so on.
26032 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
26033 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
26036 @subsection Nios II
26037 @cindex Nios II architecture
26039 When @value{GDBN} is debugging the Nios II architecture,
26040 it provides the following special commands:
26044 @item set debug nios2
26045 @kindex set debug nios2
26046 This command turns on and off debugging messages for the Nios II
26047 target code in @value{GDBN}.
26049 @item show debug nios2
26050 @kindex show debug nios2
26051 Show the current setting of Nios II debugging messages.
26055 @subsection Sparc64
26056 @cindex Sparc64 support
26057 @cindex Application Data Integrity
26058 @subsubsection ADI Support
26060 The M7 processor supports an Application Data Integrity (ADI) feature that
26061 detects invalid data accesses. When software allocates memory and enables
26062 ADI on the allocated memory, it chooses a 4-bit version number, sets the
26063 version in the upper 4 bits of the 64-bit pointer to that data, and stores
26064 the 4-bit version in every cacheline of that data. Hardware saves the latter
26065 in spare bits in the cache and memory hierarchy. On each load and store,
26066 the processor compares the upper 4 VA (virtual address) bits to the
26067 cacheline's version. If there is a mismatch, the processor generates a
26068 version mismatch trap which can be either precise or disrupting. The trap
26069 is an error condition which the kernel delivers to the process as a SIGSEGV
26072 Note that only 64-bit applications can use ADI and need to be built with
26075 Values of the ADI version tags, which are in granularity of a
26076 cacheline (64 bytes), can be viewed or modified.
26080 @kindex adi examine
26081 @item adi (examine | x) [ / @var{n} ] @var{addr}
26083 The @code{adi examine} command displays the value of one ADI version tag per
26086 @var{n} is a decimal integer specifying the number in bytes; the default
26087 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
26088 block size, to display.
26090 @var{addr} is the address in user address space where you want @value{GDBN}
26091 to begin displaying the ADI version tags.
26093 Below is an example of displaying ADI versions of variable "shmaddr".
26096 (@value{GDBP}) adi x/100 shmaddr
26097 0xfff800010002c000: 0 0
26101 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
26103 The @code{adi assign} command is used to assign new ADI version tag
26106 @var{n} is a decimal integer specifying the number in bytes;
26107 the default is 1. It specifies how much ADI version information, at the
26108 ratio of 1:ADI block size, to modify.
26110 @var{addr} is the address in user address space where you want @value{GDBN}
26111 to begin modifying the ADI version tags.
26113 @var{tag} is the new ADI version tag.
26115 For example, do the following to modify then verify ADI versions of
26116 variable "shmaddr":
26119 (@value{GDBP}) adi a/100 shmaddr = 7
26120 (@value{GDBP}) adi x/100 shmaddr
26121 0xfff800010002c000: 7 7
26128 @cindex S12Z support
26130 When @value{GDBN} is debugging the S12Z architecture,
26131 it provides the following special command:
26134 @item maint info bdccsr
26135 @kindex maint info bdccsr@r{, S12Z}
26136 This command displays the current value of the microprocessor's
26141 @node Controlling GDB
26142 @chapter Controlling @value{GDBN}
26144 You can alter the way @value{GDBN} interacts with you by using the
26145 @code{set} command. For commands controlling how @value{GDBN} displays
26146 data, see @ref{Print Settings, ,Print Settings}. Other settings are
26151 * Editing:: Command editing
26152 * Command History:: Command history
26153 * Screen Size:: Screen size
26154 * Output Styling:: Output styling
26155 * Numbers:: Numbers
26156 * ABI:: Configuring the current ABI
26157 * Auto-loading:: Automatically loading associated files
26158 * Messages/Warnings:: Optional warnings and messages
26159 * Debugging Output:: Optional messages about internal happenings
26160 * Other Misc Settings:: Other Miscellaneous Settings
26168 @value{GDBN} indicates its readiness to read a command by printing a string
26169 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
26170 can change the prompt string with the @code{set prompt} command. For
26171 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
26172 the prompt in one of the @value{GDBN} sessions so that you can always tell
26173 which one you are talking to.
26175 @emph{Note:} @code{set prompt} does not add a space for you after the
26176 prompt you set. This allows you to set a prompt which ends in a space
26177 or a prompt that does not.
26181 @item set prompt @var{newprompt}
26182 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
26184 @kindex show prompt
26186 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
26189 Versions of @value{GDBN} that ship with Python scripting enabled have
26190 prompt extensions. The commands for interacting with these extensions
26194 @kindex set extended-prompt
26195 @item set extended-prompt @var{prompt}
26196 Set an extended prompt that allows for substitutions.
26197 @xref{gdb.prompt}, for a list of escape sequences that can be used for
26198 substitution. Any escape sequences specified as part of the prompt
26199 string are replaced with the corresponding strings each time the prompt
26205 set extended-prompt Current working directory: \w (gdb)
26208 Note that when an extended-prompt is set, it takes control of the
26209 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
26211 @kindex show extended-prompt
26212 @item show extended-prompt
26213 Prints the extended prompt. Any escape sequences specified as part of
26214 the prompt string with @code{set extended-prompt}, are replaced with the
26215 corresponding strings each time the prompt is displayed.
26219 @section Command Editing
26221 @cindex command line editing
26223 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
26224 @sc{gnu} library provides consistent behavior for programs which provide a
26225 command line interface to the user. Advantages are @sc{gnu} Emacs-style
26226 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
26227 substitution, and a storage and recall of command history across
26228 debugging sessions.
26230 You may control the behavior of command line editing in @value{GDBN} with the
26231 command @code{set}.
26234 @kindex set editing
26237 @itemx set editing on
26238 Enable command line editing (enabled by default).
26240 @item set editing off
26241 Disable command line editing.
26243 @kindex show editing
26245 Show whether command line editing is enabled.
26248 @ifset SYSTEM_READLINE
26249 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
26251 @ifclear SYSTEM_READLINE
26252 @xref{Command Line Editing},
26254 for more details about the Readline
26255 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
26256 encouraged to read that chapter.
26258 @cindex Readline application name
26259 @value{GDBN} sets the Readline application name to @samp{gdb}. This
26260 is useful for conditions in @file{.inputrc}.
26262 @cindex operate-and-get-next
26263 @value{GDBN} defines a bindable Readline command,
26264 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
26265 This command accepts the current line for execution and fetches the
26266 next line relative to the current line from the history for editing.
26267 Any argument is ignored.
26269 @node Command History
26270 @section Command History
26271 @cindex command history
26273 @value{GDBN} can keep track of the commands you type during your
26274 debugging sessions, so that you can be certain of precisely what
26275 happened. Use these commands to manage the @value{GDBN} command
26278 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
26279 package, to provide the history facility.
26280 @ifset SYSTEM_READLINE
26281 @xref{Using History Interactively, , , history, GNU History Library},
26283 @ifclear SYSTEM_READLINE
26284 @xref{Using History Interactively},
26286 for the detailed description of the History library.
26288 To issue a command to @value{GDBN} without affecting certain aspects of
26289 the state which is seen by users, prefix it with @samp{server }
26290 (@pxref{Server Prefix}). This
26291 means that this command will not affect the command history, nor will it
26292 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
26293 pressed on a line by itself.
26295 @cindex @code{server}, command prefix
26296 The server prefix does not affect the recording of values into the value
26297 history; to print a value without recording it into the value history,
26298 use the @code{output} command instead of the @code{print} command.
26300 Here is the description of @value{GDBN} commands related to command
26304 @cindex history substitution
26305 @cindex history file
26306 @kindex set history filename
26307 @cindex @env{GDBHISTFILE}, environment variable
26308 @item set history filename @r{[}@var{fname}@r{]}
26309 Set the name of the @value{GDBN} command history file to @var{fname}.
26310 This is the file where @value{GDBN} reads an initial command history
26311 list, and where it writes the command history from this session when it
26312 exits. You can access this list through history expansion or through
26313 the history command editing characters listed below. This file defaults
26314 to the value of the environment variable @env{GDBHISTFILE}, or to
26315 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
26318 The @env{GDBHISTFILE} environment variable is read after processing
26319 any @value{GDBN} initialization files (@pxref{Startup}) and after
26320 processing any commands passed using command line options (for
26321 example, @code{-ex}).
26323 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
26324 is the empty string then @value{GDBN} will neither try to load an
26325 existing history file, nor will it try to save the history on exit.
26327 @cindex save command history
26328 @kindex set history save
26329 @item set history save
26330 @itemx set history save on
26331 Record command history in a file, whose name may be specified with the
26332 @code{set history filename} command. By default, this option is
26333 disabled. The command history will be recorded when @value{GDBN}
26334 exits. If @code{set history filename} is set to the empty string then
26335 history saving is disabled, even when @code{set history save} is
26338 @item set history save off
26339 Don't record the command history into the file specified by @code{set
26340 history filename} when @value{GDBN} exits.
26342 @cindex history size
26343 @kindex set history size
26344 @cindex @env{GDBHISTSIZE}, environment variable
26345 @item set history size @var{size}
26346 @itemx set history size unlimited
26347 Set the number of commands which @value{GDBN} keeps in its history list.
26348 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
26349 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
26350 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
26351 either a negative number or the empty string, then the number of commands
26352 @value{GDBN} keeps in the history list is unlimited.
26354 The @env{GDBHISTSIZE} environment variable is read after processing
26355 any @value{GDBN} initialization files (@pxref{Startup}) and after
26356 processing any commands passed using command line options (for
26357 example, @code{-ex}).
26359 @cindex remove duplicate history
26360 @kindex set history remove-duplicates
26361 @item set history remove-duplicates @var{count}
26362 @itemx set history remove-duplicates unlimited
26363 Control the removal of duplicate history entries in the command history list.
26364 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26365 history entries and remove the first entry that is a duplicate of the current
26366 entry being added to the command history list. If @var{count} is
26367 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26368 removal of duplicate history entries is disabled.
26370 Only history entries added during the current session are considered for
26371 removal. This option is set to 0 by default.
26375 History expansion assigns special meaning to the character @kbd{!}.
26376 @ifset SYSTEM_READLINE
26377 @xref{Event Designators, , , history, GNU History Library},
26379 @ifclear SYSTEM_READLINE
26380 @xref{Event Designators},
26384 @cindex history expansion, turn on/off
26385 Since @kbd{!} is also the logical not operator in C, history expansion
26386 is off by default. If you decide to enable history expansion with the
26387 @code{set history expansion on} command, you may sometimes need to
26388 follow @kbd{!} (when it is used as logical not, in an expression) with
26389 a space or a tab to prevent it from being expanded. The readline
26390 history facilities do not attempt substitution on the strings
26391 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26393 The commands to control history expansion are:
26396 @item set history expansion on
26397 @itemx set history expansion
26398 @kindex set history expansion
26399 Enable history expansion. History expansion is off by default.
26401 @item set history expansion off
26402 Disable history expansion.
26405 @kindex show history
26407 @itemx show history filename
26408 @itemx show history save
26409 @itemx show history size
26410 @itemx show history expansion
26411 These commands display the state of the @value{GDBN} history parameters.
26412 @code{show history} by itself displays all four states.
26417 @kindex show commands
26418 @cindex show last commands
26419 @cindex display command history
26420 @item show commands
26421 Display the last ten commands in the command history.
26423 @item show commands @var{n}
26424 Print ten commands centered on command number @var{n}.
26426 @item show commands +
26427 Print ten commands just after the commands last printed.
26431 @section Screen Size
26432 @cindex size of screen
26433 @cindex screen size
26436 @cindex pauses in output
26438 Certain commands to @value{GDBN} may produce large amounts of
26439 information output to the screen. To help you read all of it,
26440 @value{GDBN} pauses and asks you for input at the end of each page of
26441 output. Type @key{RET} when you want to see one more page of output,
26442 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26443 without paging for the rest of the current command. Also, the screen
26444 width setting determines when to wrap lines of output. Depending on
26445 what is being printed, @value{GDBN} tries to break the line at a
26446 readable place, rather than simply letting it overflow onto the
26449 Normally @value{GDBN} knows the size of the screen from the terminal
26450 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26451 together with the value of the @env{TERM} environment variable and the
26452 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26453 you can override it with the @code{set height} and @code{set
26460 @kindex show height
26461 @item set height @var{lpp}
26462 @itemx set height unlimited
26464 @itemx set width @var{cpl}
26465 @itemx set width unlimited
26467 These @code{set} commands specify a screen height of @var{lpp} lines and
26468 a screen width of @var{cpl} characters. The associated @code{show}
26469 commands display the current settings.
26471 If you specify a height of either @code{unlimited} or zero lines,
26472 @value{GDBN} does not pause during output no matter how long the
26473 output is. This is useful if output is to a file or to an editor
26476 Likewise, you can specify @samp{set width unlimited} or @samp{set
26477 width 0} to prevent @value{GDBN} from wrapping its output.
26479 @item set pagination on
26480 @itemx set pagination off
26481 @kindex set pagination
26482 Turn the output pagination on or off; the default is on. Turning
26483 pagination off is the alternative to @code{set height unlimited}. Note that
26484 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26485 Options, -batch}) also automatically disables pagination.
26487 @item show pagination
26488 @kindex show pagination
26489 Show the current pagination mode.
26492 @node Output Styling
26493 @section Output Styling
26499 @value{GDBN} can style its output on a capable terminal. This is
26500 enabled by default on most systems, but disabled by default when in
26501 batch mode (@pxref{Mode Options}). Various style settings are available;
26502 and styles can also be disabled entirely.
26505 @item set style enabled @samp{on|off}
26506 Enable or disable all styling. The default is host-dependent, with
26507 most hosts defaulting to @samp{on}.
26509 @item show style enabled
26510 Show the current state of styling.
26512 @item set style sources @samp{on|off}
26513 Enable or disable source code styling. This affects whether source
26514 code, such as the output of the @code{list} command, is styled. The
26515 default is @samp{on}. Note that source styling only works if styling
26516 in general is enabled, and if a source highlighting library is
26517 available to @value{GDBN}.
26519 There are two ways that highlighting can be done. First, if
26520 @value{GDBN} was linked with the GNU Source Highlight library, then it
26521 is used. Otherwise, if @value{GDBN} was configured with Python
26522 scripting support, and if the Python Pygments package is available,
26523 then it will be used.
26525 @item show style sources
26526 Show the current state of source code styling.
26528 @item set style disassembler enabled @samp{on|off}
26529 Enable or disable disassembler styling. This affects whether
26530 disassembler output, such as the output of the @code{disassemble}
26531 command, is styled. Disassembler styling only works if styling in
26532 general is enabled (with @code{set style enabled on}), and if a source
26533 highlighting library is available to @value{GDBN}.
26535 To highlight disassembler output, @value{GDBN} must be compiled with
26536 Python support, and the Python Pygments package must be available. If
26537 these requirements are not met then @value{GDBN} will not highlight
26538 disassembler output, even when this option is @samp{on}.
26540 @item show style disassembler enabled
26541 Show the current state of disassembler styling.
26544 Subcommands of @code{set style} control specific forms of styling.
26545 These subcommands all follow the same pattern: each style-able object
26546 can be styled with a foreground color, a background color, and an
26549 For example, the style of file names can be controlled using the
26550 @code{set style filename} group of commands:
26553 @item set style filename background @var{color}
26554 Set the background to @var{color}. Valid colors are @samp{none}
26555 (meaning the terminal's default color), @samp{black}, @samp{red},
26556 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26559 @item set style filename foreground @var{color}
26560 Set the foreground to @var{color}. Valid colors are @samp{none}
26561 (meaning the terminal's default color), @samp{black}, @samp{red},
26562 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26565 @item set style filename intensity @var{value}
26566 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26567 (the default), @samp{bold}, and @samp{dim}.
26570 The @code{show style} command and its subcommands are styling
26571 a style name in their output using its own style.
26572 So, use @command{show style} to see the complete list of styles,
26573 their characteristics and the visual aspect of each style.
26575 The style-able objects are:
26578 Control the styling of file names and URLs. By default, this style's
26579 foreground color is green.
26582 Control the styling of function names. These are managed with the
26583 @code{set style function} family of commands. By default, this
26584 style's foreground color is yellow.
26587 Control the styling of variable names. These are managed with the
26588 @code{set style variable} family of commands. By default, this style's
26589 foreground color is cyan.
26592 Control the styling of addresses. These are managed with the
26593 @code{set style address} family of commands. By default, this style's
26594 foreground color is blue.
26597 Control the styling of @value{GDBN}'s version number text. By
26598 default, this style's foreground color is magenta and it has bold
26599 intensity. The version number is displayed in two places, the output
26600 of @command{show version}, and when @value{GDBN} starts up.
26602 In order to control how @value{GDBN} styles the version number at
26603 startup, add the @code{set style version} family of commands to the
26604 early initialization command file (@pxref{Initialization
26608 Control the styling of titles. These are managed with the
26609 @code{set style title} family of commands. By default, this style's
26610 intensity is bold. Commands are using the title style to improve
26611 the readability of large output. For example, the commands
26612 @command{apropos} and @command{help} are using the title style
26613 for the command names.
26616 Control the styling of highlightings. These are managed with the
26617 @code{set style highlight} family of commands. By default, this style's
26618 foreground color is red. Commands are using the highlight style to draw
26619 the user attention to some specific parts of their output. For example,
26620 the command @command{apropos -v REGEXP} uses the highlight style to
26621 mark the documentation parts matching @var{regexp}.
26624 Control the styling of data annotations added by @value{GDBN} to data
26625 it displays. By default, this style's intensity is dim. Metadata
26626 annotations include the @samp{repeats @var{n} times} annotation for
26627 suppressed display of repeated array elements (@pxref{Print Settings}),
26628 @samp{<unavailable>} and @w{@samp{<error @var{descr}>}} annotations
26629 for errors and @samp{<optimized-out>} annotations for optimized-out
26630 values in displaying stack frame information in backtraces
26631 (@pxref{Backtrace}), etc.
26634 Control the styling of the TUI border. Note that, unlike other
26635 styling options, only the color of the border can be controlled via
26636 @code{set style}. This was done for compatibility reasons, as TUI
26637 controls to set the border's intensity predated the addition of
26638 general styling to @value{GDBN}. @xref{TUI Configuration}.
26640 @item tui-active-border
26641 Control the styling of the active TUI border; that is, the TUI window
26642 that has the focus.
26648 @cindex number representation
26649 @cindex entering numbers
26651 You can always enter numbers in octal, decimal, or hexadecimal in
26652 @value{GDBN} by the usual conventions: octal numbers begin with
26653 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26654 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26655 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26656 10; likewise, the default display for numbers---when no particular
26657 format is specified---is base 10. You can change the default base for
26658 both input and output with the commands described below.
26661 @kindex set input-radix
26662 @item set input-radix @var{base}
26663 Set the default base for numeric input. Supported choices
26664 for @var{base} are decimal 8, 10, or 16. The base must itself be
26665 specified either unambiguously or using the current input radix; for
26669 set input-radix 012
26670 set input-radix 10.
26671 set input-radix 0xa
26675 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26676 leaves the input radix unchanged, no matter what it was, since
26677 @samp{10}, being without any leading or trailing signs of its base, is
26678 interpreted in the current radix. Thus, if the current radix is 16,
26679 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26682 @kindex set output-radix
26683 @item set output-radix @var{base}
26684 Set the default base for numeric display. Supported choices
26685 for @var{base} are decimal 8, 10, or 16. The base must itself be
26686 specified either unambiguously or using the current input radix.
26688 @kindex show input-radix
26689 @item show input-radix
26690 Display the current default base for numeric input.
26692 @kindex show output-radix
26693 @item show output-radix
26694 Display the current default base for numeric display.
26696 @item set radix @r{[}@var{base}@r{]}
26700 These commands set and show the default base for both input and output
26701 of numbers. @code{set radix} sets the radix of input and output to
26702 the same base; without an argument, it resets the radix back to its
26703 default value of 10.
26708 @section Configuring the Current ABI
26710 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26711 application automatically. However, sometimes you need to override its
26712 conclusions. Use these commands to manage @value{GDBN}'s view of the
26718 @cindex Newlib OS ABI and its influence on the longjmp handling
26720 One @value{GDBN} configuration can debug binaries for multiple operating
26721 system targets, either via remote debugging or native emulation.
26722 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26723 but you can override its conclusion using the @code{set osabi} command.
26724 One example where this is useful is in debugging of binaries which use
26725 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26726 not have the same identifying marks that the standard C library for your
26729 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26730 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26731 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26732 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26736 Show the OS ABI currently in use.
26739 With no argument, show the list of registered available OS ABI's.
26741 @item set osabi @var{abi}
26742 Set the current OS ABI to @var{abi}.
26745 @cindex float promotion
26747 Generally, the way that an argument of type @code{float} is passed to a
26748 function depends on whether the function is prototyped. For a prototyped
26749 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26750 according to the architecture's convention for @code{float}. For unprototyped
26751 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26752 @code{double} and then passed.
26754 Unfortunately, some forms of debug information do not reliably indicate whether
26755 a function is prototyped. If @value{GDBN} calls a function that is not marked
26756 as prototyped, it consults @kbd{set coerce-float-to-double}.
26759 @kindex set coerce-float-to-double
26760 @item set coerce-float-to-double
26761 @itemx set coerce-float-to-double on
26762 Arguments of type @code{float} will be promoted to @code{double} when passed
26763 to an unprototyped function. This is the default setting.
26765 @item set coerce-float-to-double off
26766 Arguments of type @code{float} will be passed directly to unprototyped
26769 @kindex show coerce-float-to-double
26770 @item show coerce-float-to-double
26771 Show the current setting of promoting @code{float} to @code{double}.
26775 @kindex show cp-abi
26776 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26777 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26778 used to build your application. @value{GDBN} only fully supports
26779 programs with a single C@t{++} ABI; if your program contains code using
26780 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26781 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26782 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26783 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26784 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26785 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26790 Show the C@t{++} ABI currently in use.
26793 With no argument, show the list of supported C@t{++} ABI's.
26795 @item set cp-abi @var{abi}
26796 @itemx set cp-abi auto
26797 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26801 @section Automatically loading associated files
26802 @cindex auto-loading
26804 @value{GDBN} sometimes reads files with commands and settings automatically,
26805 without being explicitly told so by the user. We call this feature
26806 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26807 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26808 results or introduce security risks (e.g., if the file comes from untrusted
26811 There are various kinds of files @value{GDBN} can automatically load.
26812 In addition to these files, @value{GDBN} supports auto-loading code written
26813 in various extension languages. @xref{Auto-loading extensions}.
26815 Note that loading of these associated files (including the local @file{.gdbinit}
26816 file) requires accordingly configured @code{auto-load safe-path}
26817 (@pxref{Auto-loading safe path}).
26819 For these reasons, @value{GDBN} includes commands and options to let you
26820 control when to auto-load files and which files should be auto-loaded.
26823 @anchor{set auto-load off}
26824 @kindex set auto-load off
26825 @item set auto-load off
26826 Globally disable loading of all auto-loaded files.
26827 You may want to use this command with the @samp{-iex} option
26828 (@pxref{Option -init-eval-command}) such as:
26830 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26833 Be aware that system init file (@pxref{System-wide configuration})
26834 and init files from your home directory (@pxref{Home Directory Init File})
26835 still get read (as they come from generally trusted directories).
26836 To prevent @value{GDBN} from auto-loading even those init files, use the
26837 @option{-nx} option (@pxref{Mode Options}), in addition to
26838 @code{set auto-load no}.
26840 @anchor{show auto-load}
26841 @kindex show auto-load
26842 @item show auto-load
26843 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26847 (gdb) show auto-load
26848 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26849 libthread-db: Auto-loading of inferior specific libthread_db is on.
26850 local-gdbinit: Auto-loading of .gdbinit script from current directory
26852 python-scripts: Auto-loading of Python scripts is on.
26853 safe-path: List of directories from which it is safe to auto-load files
26854 is $debugdir:$datadir/auto-load.
26855 scripts-directory: List of directories from which to load auto-loaded scripts
26856 is $debugdir:$datadir/auto-load.
26859 @anchor{info auto-load}
26860 @kindex info auto-load
26861 @item info auto-load
26862 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26866 (gdb) info auto-load
26869 Yes /home/user/gdb/gdb-gdb.gdb
26870 libthread-db: No auto-loaded libthread-db.
26871 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26875 Yes /home/user/gdb/gdb-gdb.py
26879 These are @value{GDBN} control commands for the auto-loading:
26881 @multitable @columnfractions .5 .5
26882 @item @xref{set auto-load off}.
26883 @tab Disable auto-loading globally.
26884 @item @xref{show auto-load}.
26885 @tab Show setting of all kinds of files.
26886 @item @xref{info auto-load}.
26887 @tab Show state of all kinds of files.
26888 @item @xref{set auto-load gdb-scripts}.
26889 @tab Control for @value{GDBN} command scripts.
26890 @item @xref{show auto-load gdb-scripts}.
26891 @tab Show setting of @value{GDBN} command scripts.
26892 @item @xref{info auto-load gdb-scripts}.
26893 @tab Show state of @value{GDBN} command scripts.
26894 @item @xref{set auto-load python-scripts}.
26895 @tab Control for @value{GDBN} Python scripts.
26896 @item @xref{show auto-load python-scripts}.
26897 @tab Show setting of @value{GDBN} Python scripts.
26898 @item @xref{info auto-load python-scripts}.
26899 @tab Show state of @value{GDBN} Python scripts.
26900 @item @xref{set auto-load guile-scripts}.
26901 @tab Control for @value{GDBN} Guile scripts.
26902 @item @xref{show auto-load guile-scripts}.
26903 @tab Show setting of @value{GDBN} Guile scripts.
26904 @item @xref{info auto-load guile-scripts}.
26905 @tab Show state of @value{GDBN} Guile scripts.
26906 @item @xref{set auto-load scripts-directory}.
26907 @tab Control for @value{GDBN} auto-loaded scripts location.
26908 @item @xref{show auto-load scripts-directory}.
26909 @tab Show @value{GDBN} auto-loaded scripts location.
26910 @item @xref{add-auto-load-scripts-directory}.
26911 @tab Add directory for auto-loaded scripts location list.
26912 @item @xref{set auto-load local-gdbinit}.
26913 @tab Control for init file in the current directory.
26914 @item @xref{show auto-load local-gdbinit}.
26915 @tab Show setting of init file in the current directory.
26916 @item @xref{info auto-load local-gdbinit}.
26917 @tab Show state of init file in the current directory.
26918 @item @xref{set auto-load libthread-db}.
26919 @tab Control for thread debugging library.
26920 @item @xref{show auto-load libthread-db}.
26921 @tab Show setting of thread debugging library.
26922 @item @xref{info auto-load libthread-db}.
26923 @tab Show state of thread debugging library.
26924 @item @xref{set auto-load safe-path}.
26925 @tab Control directories trusted for automatic loading.
26926 @item @xref{show auto-load safe-path}.
26927 @tab Show directories trusted for automatic loading.
26928 @item @xref{add-auto-load-safe-path}.
26929 @tab Add directory trusted for automatic loading.
26933 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
26934 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
26936 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
26937 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
26940 @node Init File in the Current Directory
26941 @subsection Automatically loading init file in the current directory
26942 @cindex auto-loading init file in the current directory
26944 By default, @value{GDBN} reads and executes the canned sequences of commands
26945 from init file (if any) in the current working directory,
26946 see @ref{Init File in the Current Directory during Startup}.
26948 Note that loading of this local @file{.gdbinit} file also requires accordingly
26949 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26952 @anchor{set auto-load local-gdbinit}
26953 @kindex set auto-load local-gdbinit
26954 @item set auto-load local-gdbinit [on|off]
26955 Enable or disable the auto-loading of canned sequences of commands
26956 (@pxref{Sequences}) found in init file in the current directory.
26958 @anchor{show auto-load local-gdbinit}
26959 @kindex show auto-load local-gdbinit
26960 @item show auto-load local-gdbinit
26961 Show whether auto-loading of canned sequences of commands from init file in the
26962 current directory is enabled or disabled.
26964 @anchor{info auto-load local-gdbinit}
26965 @kindex info auto-load local-gdbinit
26966 @item info auto-load local-gdbinit
26967 Print whether canned sequences of commands from init file in the
26968 current directory have been auto-loaded.
26971 @node libthread_db.so.1 file
26972 @subsection Automatically loading thread debugging library
26973 @cindex auto-loading libthread_db.so.1
26975 This feature is currently present only on @sc{gnu}/Linux native hosts.
26977 @value{GDBN} reads in some cases thread debugging library from places specific
26978 to the inferior (@pxref{set libthread-db-search-path}).
26980 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26981 without checking this @samp{set auto-load libthread-db} switch as system
26982 libraries have to be trusted in general. In all other cases of
26983 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26984 auto-load libthread-db} is enabled before trying to open such thread debugging
26987 Note that loading of this debugging library also requires accordingly configured
26988 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26991 @anchor{set auto-load libthread-db}
26992 @kindex set auto-load libthread-db
26993 @item set auto-load libthread-db [on|off]
26994 Enable or disable the auto-loading of inferior specific thread debugging library.
26996 @anchor{show auto-load libthread-db}
26997 @kindex show auto-load libthread-db
26998 @item show auto-load libthread-db
26999 Show whether auto-loading of inferior specific thread debugging library is
27000 enabled or disabled.
27002 @anchor{info auto-load libthread-db}
27003 @kindex info auto-load libthread-db
27004 @item info auto-load libthread-db
27005 Print the list of all loaded inferior specific thread debugging libraries and
27006 for each such library print list of inferior @var{pid}s using it.
27009 @node Auto-loading safe path
27010 @subsection Security restriction for auto-loading
27011 @cindex auto-loading safe-path
27013 As the files of inferior can come from untrusted source (such as submitted by
27014 an application user) @value{GDBN} does not always load any files automatically.
27015 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
27016 directories trusted for loading files not explicitly requested by user.
27017 Each directory can also be a shell wildcard pattern.
27019 If the path is not set properly you will see a warning and the file will not
27024 Reading symbols from /home/user/gdb/gdb...
27025 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
27026 declined by your `auto-load safe-path' set
27027 to "$debugdir:$datadir/auto-load".
27028 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
27029 declined by your `auto-load safe-path' set
27030 to "$debugdir:$datadir/auto-load".
27034 To instruct @value{GDBN} to go ahead and use the init files anyway,
27035 invoke @value{GDBN} like this:
27038 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
27041 The list of trusted directories is controlled by the following commands:
27044 @anchor{set auto-load safe-path}
27045 @kindex set auto-load safe-path
27046 @item set auto-load safe-path @r{[}@var{directories}@r{]}
27047 Set the list of directories (and their subdirectories) trusted for automatic
27048 loading and execution of scripts. You can also enter a specific trusted file.
27049 Each directory can also be a shell wildcard pattern; wildcards do not match
27050 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
27051 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
27052 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
27053 its default value as specified during @value{GDBN} compilation.
27055 The list of directories uses path separator (@samp{:} on GNU and Unix
27056 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27057 to the @env{PATH} environment variable.
27059 @anchor{show auto-load safe-path}
27060 @kindex show auto-load safe-path
27061 @item show auto-load safe-path
27062 Show the list of directories trusted for automatic loading and execution of
27065 @anchor{add-auto-load-safe-path}
27066 @kindex add-auto-load-safe-path
27067 @item add-auto-load-safe-path
27068 Add an entry (or list of entries) to the list of directories trusted for
27069 automatic loading and execution of scripts. Multiple entries may be delimited
27070 by the host platform path separator in use.
27073 This variable defaults to what @code{--with-auto-load-dir} has been configured
27074 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
27075 substitution applies the same as for @ref{set auto-load scripts-directory}.
27076 The default @code{set auto-load safe-path} value can be also overriden by
27077 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
27079 Setting this variable to @file{/} disables this security protection,
27080 corresponding @value{GDBN} configuration option is
27081 @option{--without-auto-load-safe-path}.
27082 This variable is supposed to be set to the system directories writable by the
27083 system superuser only. Users can add their source directories in init files in
27084 their home directories (@pxref{Home Directory Init File}). See also deprecated
27085 init file in the current directory
27086 (@pxref{Init File in the Current Directory during Startup}).
27088 To force @value{GDBN} to load the files it declined to load in the previous
27089 example, you could use one of the following ways:
27092 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
27093 Specify this trusted directory (or a file) as additional component of the list.
27094 You have to specify also any existing directories displayed by
27095 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
27097 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
27098 Specify this directory as in the previous case but just for a single
27099 @value{GDBN} session.
27101 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
27102 Disable auto-loading safety for a single @value{GDBN} session.
27103 This assumes all the files you debug during this @value{GDBN} session will come
27104 from trusted sources.
27106 @item @kbd{./configure --without-auto-load-safe-path}
27107 During compilation of @value{GDBN} you may disable any auto-loading safety.
27108 This assumes all the files you will ever debug with this @value{GDBN} come from
27112 On the other hand you can also explicitly forbid automatic files loading which
27113 also suppresses any such warning messages:
27116 @item @kbd{gdb -iex "set auto-load no" @dots{}}
27117 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
27119 @item @file{~/.gdbinit}: @samp{set auto-load no}
27120 Disable auto-loading globally for the user
27121 (@pxref{Home Directory Init File}). While it is improbable, you could also
27122 use system init file instead (@pxref{System-wide configuration}).
27125 This setting applies to the file names as entered by user. If no entry matches
27126 @value{GDBN} tries as a last resort to also resolve all the file names into
27127 their canonical form (typically resolving symbolic links) and compare the
27128 entries again. @value{GDBN} already canonicalizes most of the filenames on its
27129 own before starting the comparison so a canonical form of directories is
27130 recommended to be entered.
27132 @node Auto-loading verbose mode
27133 @subsection Displaying files tried for auto-load
27134 @cindex auto-loading verbose mode
27136 For better visibility of all the file locations where you can place scripts to
27137 be auto-loaded with inferior --- or to protect yourself against accidental
27138 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
27139 all the files attempted to be loaded. Both existing and non-existing files may
27142 For example the list of directories from which it is safe to auto-load files
27143 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
27144 may not be too obvious while setting it up.
27147 (gdb) set debug auto-load on
27148 (gdb) file ~/src/t/true
27149 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
27150 for objfile "/tmp/true".
27151 auto-load: Updating directories of "/usr:/opt".
27152 auto-load: Using directory "/usr".
27153 auto-load: Using directory "/opt".
27154 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
27155 by your `auto-load safe-path' set to "/usr:/opt".
27159 @anchor{set debug auto-load}
27160 @kindex set debug auto-load
27161 @item set debug auto-load [on|off]
27162 Set whether to print the filenames attempted to be auto-loaded.
27164 @anchor{show debug auto-load}
27165 @kindex show debug auto-load
27166 @item show debug auto-load
27167 Show whether printing of the filenames attempted to be auto-loaded is turned
27171 @node Messages/Warnings
27172 @section Optional Warnings and Messages
27174 @cindex verbose operation
27175 @cindex optional warnings
27176 By default, @value{GDBN} is silent about its inner workings. If you are
27177 running on a slow machine, you may want to use the @code{set verbose}
27178 command. This makes @value{GDBN} tell you when it does a lengthy
27179 internal operation, so you will not think it has crashed.
27181 Currently, the messages controlled by @code{set verbose} are those
27182 which announce that the symbol table for a source file is being read;
27183 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
27186 @kindex set verbose
27187 @item set verbose on
27188 Enables @value{GDBN} output of certain informational messages.
27190 @item set verbose off
27191 Disables @value{GDBN} output of certain informational messages.
27193 @kindex show verbose
27195 Displays whether @code{set verbose} is on or off.
27198 By default, if @value{GDBN} encounters bugs in the symbol table of an
27199 object file, it is silent; but if you are debugging a compiler, you may
27200 find this information useful (@pxref{Symbol Errors, ,Errors Reading
27205 @kindex set complaints
27206 @item set complaints @var{limit}
27207 Permits @value{GDBN} to output @var{limit} complaints about each type of
27208 unusual symbols before becoming silent about the problem. Set
27209 @var{limit} to zero to suppress all complaints; set it to a large number
27210 to prevent complaints from being suppressed.
27212 @kindex show complaints
27213 @item show complaints
27214 Displays how many symbol complaints @value{GDBN} is permitted to produce.
27218 @anchor{confirmation requests}
27219 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
27220 lot of stupid questions to confirm certain commands. For example, if
27221 you try to run a program which is already running:
27225 The program being debugged has been started already.
27226 Start it from the beginning? (y or n)
27229 If you are willing to unflinchingly face the consequences of your own
27230 commands, you can disable this ``feature'':
27234 @kindex set confirm
27236 @cindex confirmation
27237 @cindex stupid questions
27238 @item set confirm off
27239 Disables confirmation requests. Note that running @value{GDBN} with
27240 the @option{--batch} option (@pxref{Mode Options, -batch}) also
27241 automatically disables confirmation requests.
27243 @item set confirm on
27244 Enables confirmation requests (the default).
27246 @kindex show confirm
27248 Displays state of confirmation requests.
27252 @cindex command tracing
27253 If you need to debug user-defined commands or sourced files you may find it
27254 useful to enable @dfn{command tracing}. In this mode each command will be
27255 printed as it is executed, prefixed with one or more @samp{+} symbols, the
27256 quantity denoting the call depth of each command.
27259 @kindex set trace-commands
27260 @cindex command scripts, debugging
27261 @item set trace-commands on
27262 Enable command tracing.
27263 @item set trace-commands off
27264 Disable command tracing.
27265 @item show trace-commands
27266 Display the current state of command tracing.
27269 @node Debugging Output
27270 @section Optional Messages about Internal Happenings
27271 @cindex optional debugging messages
27273 @value{GDBN} has commands that enable optional debugging messages from
27274 various @value{GDBN} subsystems; normally these commands are of
27275 interest to @value{GDBN} maintainers, or when reporting a bug. This
27276 section documents those commands.
27279 @kindex set exec-done-display
27280 @item set exec-done-display
27281 Turns on or off the notification of asynchronous commands'
27282 completion. When on, @value{GDBN} will print a message when an
27283 asynchronous command finishes its execution. The default is off.
27284 @kindex show exec-done-display
27285 @item show exec-done-display
27286 Displays the current setting of asynchronous command completion
27290 @cindex ARM AArch64
27291 @item set debug aarch64
27292 Turns on or off display of debugging messages related to ARM AArch64.
27293 The default is off.
27295 @item show debug aarch64
27296 Displays the current state of displaying debugging messages related to
27299 @cindex gdbarch debugging info
27300 @cindex architecture debugging info
27301 @item set debug arch
27302 Turns on or off display of gdbarch debugging info. The default is off
27303 @item show debug arch
27304 Displays the current state of displaying gdbarch debugging info.
27306 @item set debug aix-solib
27307 @cindex AIX shared library debugging
27308 Control display of debugging messages from the AIX shared library
27309 support module. The default is off.
27310 @item show debug aix-solib
27311 Show the current state of displaying AIX shared library debugging messages.
27313 @item set debug aix-thread
27314 @cindex AIX threads
27315 Display debugging messages about inner workings of the AIX thread
27317 @item show debug aix-thread
27318 Show the current state of AIX thread debugging info display.
27320 @item set debug check-physname
27322 Check the results of the ``physname'' computation. When reading DWARF
27323 debugging information for C@t{++}, @value{GDBN} attempts to compute
27324 each entity's name. @value{GDBN} can do this computation in two
27325 different ways, depending on exactly what information is present.
27326 When enabled, this setting causes @value{GDBN} to compute the names
27327 both ways and display any discrepancies.
27328 @item show debug check-physname
27329 Show the current state of ``physname'' checking.
27331 @item set debug coff-pe-read
27332 @cindex COFF/PE exported symbols
27333 Control display of debugging messages related to reading of COFF/PE
27334 exported symbols. The default is off.
27335 @item show debug coff-pe-read
27336 Displays the current state of displaying debugging messages related to
27337 reading of COFF/PE exported symbols.
27339 @item set debug dwarf-die
27341 Dump DWARF DIEs after they are read in.
27342 The value is the number of nesting levels to print.
27343 A value of zero turns off the display.
27344 @item show debug dwarf-die
27345 Show the current state of DWARF DIE debugging.
27347 @item set debug dwarf-line
27348 @cindex DWARF Line Tables
27349 Turns on or off display of debugging messages related to reading
27350 DWARF line tables. The default is 0 (off).
27351 A value of 1 provides basic information.
27352 A value greater than 1 provides more verbose information.
27353 @item show debug dwarf-line
27354 Show the current state of DWARF line table debugging.
27356 @item set debug dwarf-read
27357 @cindex DWARF Reading
27358 Turns on or off display of debugging messages related to reading
27359 DWARF debug info. The default is 0 (off).
27360 A value of 1 provides basic information.
27361 A value greater than 1 provides more verbose information.
27362 @item show debug dwarf-read
27363 Show the current state of DWARF reader debugging.
27365 @item set debug displaced
27366 @cindex displaced stepping debugging info
27367 Turns on or off display of @value{GDBN} debugging info for the
27368 displaced stepping support. The default is off.
27369 @item show debug displaced
27370 Displays the current state of displaying @value{GDBN} debugging info
27371 related to displaced stepping.
27373 @item set debug event
27374 @cindex event debugging info
27375 Turns on or off display of @value{GDBN} event debugging info. The
27377 @item show debug event
27378 Displays the current state of displaying @value{GDBN} event debugging
27381 @item set debug event-loop
27382 @cindex event-loop debugging
27383 Controls output of debugging info about the event loop. The possible
27384 values are @samp{off}, @samp{all} (shows all debugging info) and
27385 @samp{all-except-ui} (shows all debugging info except those about
27386 UI-related events).
27387 @item show debug event-loop
27388 Shows the current state of displaying debugging info about the event
27391 @item set debug expression
27392 @cindex expression debugging info
27393 Turns on or off display of debugging info about @value{GDBN}
27394 expression parsing. The default is off.
27395 @item show debug expression
27396 Displays the current state of displaying debugging info about
27397 @value{GDBN} expression parsing.
27399 @item set debug fbsd-lwp
27400 @cindex FreeBSD LWP debug messages
27401 Turns on or off debugging messages from the FreeBSD LWP debug support.
27402 @item show debug fbsd-lwp
27403 Show the current state of FreeBSD LWP debugging messages.
27405 @item set debug fbsd-nat
27406 @cindex FreeBSD native target debug messages
27407 Turns on or off debugging messages from the FreeBSD native target.
27408 @item show debug fbsd-nat
27409 Show the current state of FreeBSD native target debugging messages.
27411 @item set debug fortran-array-slicing
27412 @cindex fortran array slicing debugging info
27413 Turns on or off display of @value{GDBN} Fortran array slicing
27414 debugging info. The default is off.
27416 @item show debug fortran-array-slicing
27417 Displays the current state of displaying @value{GDBN} Fortran array
27418 slicing debugging info.
27420 @item set debug frame
27421 @cindex frame debugging info
27422 Turns on or off display of @value{GDBN} frame debugging info. The
27424 @item show debug frame
27425 Displays the current state of displaying @value{GDBN} frame debugging
27428 @item set debug gnu-nat
27429 @cindex @sc{gnu}/Hurd debug messages
27430 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27431 @item show debug gnu-nat
27432 Show the current state of @sc{gnu}/Hurd debugging messages.
27434 @item set debug infrun
27435 @cindex inferior debugging info
27436 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27437 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27438 for implementing operations such as single-stepping the inferior.
27439 @item show debug infrun
27440 Displays the current state of @value{GDBN} inferior debugging.
27442 @item set debug jit
27443 @cindex just-in-time compilation, debugging messages
27444 Turn on or off debugging messages from JIT debug support.
27445 @item show debug jit
27446 Displays the current state of @value{GDBN} JIT debugging.
27448 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27449 @cindex @sc{gnu}/Linux native target debug messages
27450 @cindex Linux native targets
27451 Turn on or off debugging messages from the Linux native target debug support.
27452 @item show debug linux-nat
27453 Show the current state of Linux native target debugging messages.
27455 @item set debug linux-namespaces
27456 @cindex @sc{gnu}/Linux namespaces debug messages
27457 Turn on or off debugging messages from the Linux namespaces debug support.
27458 @item show debug linux-namespaces
27459 Show the current state of Linux namespaces debugging messages.
27461 @item set debug mach-o
27462 @cindex Mach-O symbols processing
27463 Control display of debugging messages related to Mach-O symbols
27464 processing. The default is off.
27465 @item show debug mach-o
27466 Displays the current state of displaying debugging messages related to
27467 reading of COFF/PE exported symbols.
27469 @item set debug notification
27470 @cindex remote async notification debugging info
27471 Turn on or off debugging messages about remote async notification.
27472 The default is off.
27473 @item show debug notification
27474 Displays the current state of remote async notification debugging messages.
27476 @item set debug observer
27477 @cindex observer debugging info
27478 Turns on or off display of @value{GDBN} observer debugging. This
27479 includes info such as the notification of observable events.
27480 @item show debug observer
27481 Displays the current state of observer debugging.
27483 @item set debug overload
27484 @cindex C@t{++} overload debugging info
27485 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27486 info. This includes info such as ranking of functions, etc. The default
27488 @item show debug overload
27489 Displays the current state of displaying @value{GDBN} C@t{++} overload
27492 @cindex expression parser, debugging info
27493 @cindex debug expression parser
27494 @item set debug parser
27495 Turns on or off the display of expression parser debugging output.
27496 Internally, this sets the @code{yydebug} variable in the expression
27497 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27498 details. The default is off.
27499 @item show debug parser
27500 Show the current state of expression parser debugging.
27502 @cindex packets, reporting on stdout
27503 @cindex serial connections, debugging
27504 @cindex debug remote protocol
27505 @cindex remote protocol debugging
27506 @cindex display remote packets
27507 @item set debug remote
27508 Turns on or off display of reports on all packets sent back and forth across
27509 the serial line to the remote machine. The info is printed on the
27510 @value{GDBN} standard output stream. The default is off.
27511 @item show debug remote
27512 Displays the state of display of remote packets.
27514 @item set debug remote-packet-max-chars
27515 Sets the maximum number of characters to display for each remote packet when
27516 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27517 displaying lengthy remote packets and polluting the console.
27519 The default value is @code{512}, which means @value{GDBN} will truncate each
27520 remote packet after 512 bytes.
27522 Setting this option to @code{unlimited} will disable truncation and will output
27523 the full length of the remote packets.
27524 @item show debug remote-packet-max-chars
27525 Displays the number of bytes to output for remote packet debugging.
27527 @item set debug separate-debug-file
27528 Turns on or off display of debug output about separate debug file search.
27529 @item show debug separate-debug-file
27530 Displays the state of separate debug file search debug output.
27532 @item set debug serial
27533 Turns on or off display of @value{GDBN} serial debugging info. The
27535 @item show debug serial
27536 Displays the current state of displaying @value{GDBN} serial debugging
27539 @item set debug solib-frv
27540 @cindex FR-V shared-library debugging
27541 Turn on or off debugging messages for FR-V shared-library code.
27542 @item show debug solib-frv
27543 Display the current state of FR-V shared-library code debugging
27546 @item set debug symbol-lookup
27547 @cindex symbol lookup
27548 Turns on or off display of debugging messages related to symbol lookup.
27549 The default is 0 (off).
27550 A value of 1 provides basic information.
27551 A value greater than 1 provides more verbose information.
27552 @item show debug symbol-lookup
27553 Show the current state of symbol lookup debugging messages.
27555 @item set debug symfile
27556 @cindex symbol file functions
27557 Turns on or off display of debugging messages related to symbol file functions.
27558 The default is off. @xref{Files}.
27559 @item show debug symfile
27560 Show the current state of symbol file debugging messages.
27562 @item set debug symtab-create
27563 @cindex symbol table creation
27564 Turns on or off display of debugging messages related to symbol table creation.
27565 The default is 0 (off).
27566 A value of 1 provides basic information.
27567 A value greater than 1 provides more verbose information.
27568 @item show debug symtab-create
27569 Show the current state of symbol table creation debugging.
27571 @item set debug target
27572 @cindex target debugging info
27573 Turns on or off display of @value{GDBN} target debugging info. This info
27574 includes what is going on at the target level of GDB, as it happens. The
27575 default is 0. Set it to 1 to track events, and to 2 to also track the
27576 value of large memory transfers.
27577 @item show debug target
27578 Displays the current state of displaying @value{GDBN} target debugging
27581 @item set debug timestamp
27582 @cindex timestamping debugging info
27583 Turns on or off display of timestamps with @value{GDBN} debugging info.
27584 When enabled, seconds and microseconds are displayed before each debugging
27586 @item show debug timestamp
27587 Displays the current state of displaying timestamps with @value{GDBN}
27590 @item set debug varobj
27591 @cindex variable object debugging info
27592 Turns on or off display of @value{GDBN} variable object debugging
27593 info. The default is off.
27594 @item show debug varobj
27595 Displays the current state of displaying @value{GDBN} variable object
27598 @item set debug xml
27599 @cindex XML parser debugging
27600 Turn on or off debugging messages for built-in XML parsers.
27601 @item show debug xml
27602 Displays the current state of XML debugging messages.
27605 @node Other Misc Settings
27606 @section Other Miscellaneous Settings
27607 @cindex miscellaneous settings
27610 @kindex set interactive-mode
27611 @item set interactive-mode
27612 If @code{on}, forces @value{GDBN} to assume that GDB was started
27613 in a terminal. In practice, this means that @value{GDBN} should wait
27614 for the user to answer queries generated by commands entered at
27615 the command prompt. If @code{off}, forces @value{GDBN} to operate
27616 in the opposite mode, and it uses the default answers to all queries.
27617 If @code{auto} (the default), @value{GDBN} tries to determine whether
27618 its standard input is a terminal, and works in interactive-mode if it
27619 is, non-interactively otherwise.
27621 In the vast majority of cases, the debugger should be able to guess
27622 correctly which mode should be used. But this setting can be useful
27623 in certain specific cases, such as running a MinGW @value{GDBN}
27624 inside a cygwin window.
27626 @kindex show interactive-mode
27627 @item show interactive-mode
27628 Displays whether the debugger is operating in interactive mode or not.
27632 @kindex set suppress-cli-notifications
27633 @item set suppress-cli-notifications
27634 If @code{on}, command-line-interface (CLI) notifications that are
27635 printed by @value{GDBN} are suppressed. If @code{off}, the
27636 notifications are printed as usual. The default value is @code{off}.
27637 CLI notifications occur when you change the selected context or when
27638 the program being debugged stops, as detailed below.
27641 @item User-selected context changes:
27642 When you change the selected context (i.e.@: the current inferior,
27643 thread and/or the frame), @value{GDBN} prints information about the
27644 new context. For example, the default behavior is below:
27648 [Switching to inferior 1 [process 634] (/tmp/test)]
27649 [Switching to thread 1 (process 634)]
27650 #0 main () at test.c:3
27655 When the notifications are suppressed, the new context is not printed:
27658 (gdb) set suppress-cli-notifications on
27663 @item The program being debugged stops:
27664 When the program you are debugging stops (e.g.@: because of hitting a
27665 breakpoint, completing source-stepping, an interrupt, etc.),
27666 @value{GDBN} prints information about the stop event. For example,
27667 below is a breakpoint hit:
27670 (gdb) break test.c:3
27671 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27675 Breakpoint 2, main () at test.c:3
27680 When the notifications are suppressed, the output becomes:
27683 (gdb) break test.c:3
27684 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27685 (gdb) set suppress-cli-notifications on
27691 Suppressing CLI notifications may be useful in scripts to obtain a
27692 reduced output from a list of commands.
27695 @kindex show suppress-cli-notifications
27696 @item show suppress-cli-notifications
27697 Displays whether printing CLI notifications is suppressed or not.
27700 @node Extending GDB
27701 @chapter Extending @value{GDBN}
27702 @cindex extending GDB
27704 @value{GDBN} provides several mechanisms for extension.
27705 @value{GDBN} also provides the ability to automatically load
27706 extensions when it reads a file for debugging. This allows the
27707 user to automatically customize @value{GDBN} for the program
27710 To facilitate the use of extension languages, @value{GDBN} is capable
27711 of evaluating the contents of a file. When doing so, @value{GDBN}
27712 can recognize which extension language is being used by looking at
27713 the filename extension. Files with an unrecognized filename extension
27714 are always treated as a @value{GDBN} Command Files.
27715 @xref{Command Files,, Command files}.
27717 You can control how @value{GDBN} evaluates these files with the following
27721 @kindex set script-extension
27722 @kindex show script-extension
27723 @item set script-extension off
27724 All scripts are always evaluated as @value{GDBN} Command Files.
27726 @item set script-extension soft
27727 The debugger determines the scripting language based on filename
27728 extension. If this scripting language is supported, @value{GDBN}
27729 evaluates the script using that language. Otherwise, it evaluates
27730 the file as a @value{GDBN} Command File.
27732 @item set script-extension strict
27733 The debugger determines the scripting language based on filename
27734 extension, and evaluates the script using that language. If the
27735 language is not supported, then the evaluation fails.
27737 @item show script-extension
27738 Display the current value of the @code{script-extension} option.
27742 @ifset SYSTEM_GDBINIT_DIR
27743 This setting is not used for files in the system-wide gdbinit directory.
27744 Files in that directory must have an extension matching their language,
27745 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27746 commands. @xref{Startup}.
27750 * Sequences:: Canned Sequences of @value{GDBN} Commands
27751 * Aliases:: Command Aliases
27752 * Python:: Extending @value{GDBN} using Python
27753 * Guile:: Extending @value{GDBN} using Guile
27754 * Auto-loading extensions:: Automatically loading extensions
27755 * Multiple Extension Languages:: Working with multiple extension languages
27759 @section Canned Sequences of Commands
27761 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27762 Command Lists}), @value{GDBN} provides two ways to store sequences of
27763 commands for execution as a unit: user-defined commands and command
27767 * Define:: How to define your own commands
27768 * Hooks:: Hooks for user-defined commands
27769 * Command Files:: How to write scripts of commands to be stored in a file
27770 * Output:: Commands for controlled output
27771 * Auto-loading sequences:: Controlling auto-loaded command files
27775 @subsection User-defined Commands
27777 @cindex user-defined command
27778 @cindex arguments, to user-defined commands
27779 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27780 which you assign a new name as a command. This is done with the
27781 @code{define} command. User commands may accept an unlimited number of arguments
27782 separated by whitespace. Arguments are accessed within the user command
27783 via @code{$arg0@dots{}$argN}. A trivial example:
27787 print $arg0 + $arg1 + $arg2
27792 To execute the command use:
27799 This defines the command @code{adder}, which prints the sum of
27800 its three arguments. Note the arguments are text substitutions, so they may
27801 reference variables, use complex expressions, or even perform inferior
27804 @cindex argument count in user-defined commands
27805 @cindex how many arguments (user-defined commands)
27806 In addition, @code{$argc} may be used to find out how many arguments have
27812 print $arg0 + $arg1
27815 print $arg0 + $arg1 + $arg2
27820 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27821 to process a variable number of arguments:
27828 eval "set $sum = $sum + $arg%d", $i
27838 @item define @var{commandname}
27839 Define a command named @var{commandname}. If there is already a command
27840 by that name, you are asked to confirm that you want to redefine it.
27841 The argument @var{commandname} may be a bare command name consisting of letters,
27842 numbers, dashes, dots, and underscores. It may also start with any
27843 predefined or user-defined prefix command.
27844 For example, @samp{define target my-target} creates
27845 a user-defined @samp{target my-target} command.
27847 The definition of the command is made up of other @value{GDBN} command lines,
27848 which are given following the @code{define} command. The end of these
27849 commands is marked by a line containing @code{end}.
27852 @kindex end@r{ (user-defined commands)}
27853 @item document @var{commandname}
27854 Document the user-defined command @var{commandname}, so that it can be
27855 accessed by @code{help}. The command @var{commandname} must already be
27856 defined. This command reads lines of documentation just as @code{define}
27857 reads the lines of the command definition, ending with @code{end}.
27858 After the @code{document} command is finished, @code{help} on command
27859 @var{commandname} displays the documentation you have written.
27861 You may use the @code{document} command again to change the
27862 documentation of a command. Redefining the command with @code{define}
27863 does not change the documentation.
27865 @kindex define-prefix
27866 @item define-prefix @var{commandname}
27867 Define or mark the command @var{commandname} as a user-defined prefix
27868 command. Once marked, @var{commandname} can be used as prefix command
27869 by the @code{define} command.
27870 Note that @code{define-prefix} can be used with a not yet defined
27871 @var{commandname}. In such a case, @var{commandname} is defined as
27872 an empty user-defined command.
27873 In case you redefine a command that was marked as a user-defined
27874 prefix command, the subcommands of the redefined command are kept
27875 (and @value{GDBN} indicates so to the user).
27879 (gdb) define-prefix abc
27880 (gdb) define-prefix abc def
27881 (gdb) define abc def
27882 Type commands for definition of "abc def".
27883 End with a line saying just "end".
27884 >echo command initial def\n
27886 (gdb) define abc def ghi
27887 Type commands for definition of "abc def ghi".
27888 End with a line saying just "end".
27889 >echo command ghi\n
27891 (gdb) define abc def
27892 Keeping subcommands of prefix command "def".
27893 Redefine command "def"? (y or n) y
27894 Type commands for definition of "abc def".
27895 End with a line saying just "end".
27896 >echo command def\n
27905 @kindex dont-repeat
27906 @cindex don't repeat command
27908 Used inside a user-defined command, this tells @value{GDBN} that this
27909 command should not be repeated when the user hits @key{RET}
27910 (@pxref{Command Syntax, repeat last command}).
27912 @kindex help user-defined
27913 @item help user-defined
27914 List all user-defined commands and all python commands defined in class
27915 COMMAND_USER. The first line of the documentation or docstring is
27920 @itemx show user @var{commandname}
27921 Display the @value{GDBN} commands used to define @var{commandname} (but
27922 not its documentation). If no @var{commandname} is given, display the
27923 definitions for all user-defined commands.
27924 This does not work for user-defined python commands.
27926 @cindex infinite recursion in user-defined commands
27927 @kindex show max-user-call-depth
27928 @kindex set max-user-call-depth
27929 @item show max-user-call-depth
27930 @itemx set max-user-call-depth
27931 The value of @code{max-user-call-depth} controls how many recursion
27932 levels are allowed in user-defined commands before @value{GDBN} suspects an
27933 infinite recursion and aborts the command.
27934 This does not apply to user-defined python commands.
27937 In addition to the above commands, user-defined commands frequently
27938 use control flow commands, described in @ref{Command Files}.
27940 When user-defined commands are executed, the
27941 commands of the definition are not printed. An error in any command
27942 stops execution of the user-defined command.
27944 If used interactively, commands that would ask for confirmation proceed
27945 without asking when used inside a user-defined command. Many @value{GDBN}
27946 commands that normally print messages to say what they are doing omit the
27947 messages when used in a user-defined command.
27950 @subsection User-defined Command Hooks
27951 @cindex command hooks
27952 @cindex hooks, for commands
27953 @cindex hooks, pre-command
27956 You may define @dfn{hooks}, which are a special kind of user-defined
27957 command. Whenever you run the command @samp{foo}, if the user-defined
27958 command @samp{hook-foo} exists, it is executed (with no arguments)
27959 before that command.
27961 @cindex hooks, post-command
27963 A hook may also be defined which is run after the command you executed.
27964 Whenever you run the command @samp{foo}, if the user-defined command
27965 @samp{hookpost-foo} exists, it is executed (with no arguments) after
27966 that command. Post-execution hooks may exist simultaneously with
27967 pre-execution hooks, for the same command.
27969 It is valid for a hook to call the command which it hooks. If this
27970 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
27972 @c It would be nice if hookpost could be passed a parameter indicating
27973 @c if the command it hooks executed properly or not. FIXME!
27975 @kindex stop@r{, a pseudo-command}
27976 In addition, a pseudo-command, @samp{stop} exists. Defining
27977 (@samp{hook-stop}) makes the associated commands execute every time
27978 execution stops in your program: before breakpoint commands are run,
27979 displays are printed, or the stack frame is printed.
27981 For example, to ignore @code{SIGALRM} signals while
27982 single-stepping, but treat them normally during normal execution,
27987 handle SIGALRM nopass
27991 handle SIGALRM pass
27994 define hook-continue
27995 handle SIGALRM pass
27999 As a further example, to hook at the beginning and end of the @code{echo}
28000 command, and to add extra text to the beginning and end of the message,
28008 define hookpost-echo
28012 (@value{GDBP}) echo Hello World
28013 <<<---Hello World--->>>
28018 You can define a hook for any single-word command in @value{GDBN}, but
28019 not for command aliases; you should define a hook for the basic command
28020 name, e.g.@: @code{backtrace} rather than @code{bt}.
28021 @c FIXME! So how does Joe User discover whether a command is an alias
28023 You can hook a multi-word command by adding @code{hook-} or
28024 @code{hookpost-} to the last word of the command, e.g.@:
28025 @samp{define target hook-remote} to add a hook to @samp{target remote}.
28027 If an error occurs during the execution of your hook, execution of
28028 @value{GDBN} commands stops and @value{GDBN} issues a prompt
28029 (before the command that you actually typed had a chance to run).
28031 If you try to define a hook which does not match any known command, you
28032 get a warning from the @code{define} command.
28034 @node Command Files
28035 @subsection Command Files
28037 @cindex command files
28038 @cindex scripting commands
28039 A command file for @value{GDBN} is a text file made of lines that are
28040 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
28041 also be included. An empty line in a command file does nothing; it
28042 does not mean to repeat the last command, as it would from the
28045 You can request the execution of a command file with the @code{source}
28046 command. Note that the @code{source} command is also used to evaluate
28047 scripts that are not Command Files. The exact behavior can be configured
28048 using the @code{script-extension} setting.
28049 @xref{Extending GDB,, Extending GDB}.
28053 @cindex execute commands from a file
28054 @item source [-s] [-v] @var{filename}
28055 Execute the command file @var{filename}.
28058 The lines in a command file are generally executed sequentially,
28059 unless the order of execution is changed by one of the
28060 @emph{flow-control commands} described below. The commands are not
28061 printed as they are executed. An error in any command terminates
28062 execution of the command file and control is returned to the console.
28064 @value{GDBN} first searches for @var{filename} in the current directory.
28065 If the file is not found there, and @var{filename} does not specify a
28066 directory, then @value{GDBN} also looks for the file on the source search path
28067 (specified with the @samp{directory} command);
28068 except that @file{$cdir} is not searched because the compilation directory
28069 is not relevant to scripts.
28071 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
28072 on the search path even if @var{filename} specifies a directory.
28073 The search is done by appending @var{filename} to each element of the
28074 search path. So, for example, if @var{filename} is @file{mylib/myscript}
28075 and the search path contains @file{/home/user} then @value{GDBN} will
28076 look for the script @file{/home/user/mylib/myscript}.
28077 The search is also done if @var{filename} is an absolute path.
28078 For example, if @var{filename} is @file{/tmp/myscript} and
28079 the search path contains @file{/home/user} then @value{GDBN} will
28080 look for the script @file{/home/user/tmp/myscript}.
28081 For DOS-like systems, if @var{filename} contains a drive specification,
28082 it is stripped before concatenation. For example, if @var{filename} is
28083 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
28084 will look for the script @file{c:/tmp/myscript}.
28086 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
28087 each command as it is executed. The option must be given before
28088 @var{filename}, and is interpreted as part of the filename anywhere else.
28090 Commands that would ask for confirmation if used interactively proceed
28091 without asking when used in a command file. Many @value{GDBN} commands that
28092 normally print messages to say what they are doing omit the messages
28093 when called from command files.
28095 @value{GDBN} also accepts command input from standard input. In this
28096 mode, normal output goes to standard output and error output goes to
28097 standard error. Errors in a command file supplied on standard input do
28098 not terminate execution of the command file---execution continues with
28102 gdb < cmds > log 2>&1
28105 (The syntax above will vary depending on the shell used.) This example
28106 will execute commands from the file @file{cmds}. All output and errors
28107 would be directed to @file{log}.
28109 Since commands stored on command files tend to be more general than
28110 commands typed interactively, they frequently need to deal with
28111 complicated situations, such as different or unexpected values of
28112 variables and symbols, changes in how the program being debugged is
28113 built, etc. @value{GDBN} provides a set of flow-control commands to
28114 deal with these complexities. Using these commands, you can write
28115 complex scripts that loop over data structures, execute commands
28116 conditionally, etc.
28123 This command allows to include in your script conditionally executed
28124 commands. The @code{if} command takes a single argument, which is an
28125 expression to evaluate. It is followed by a series of commands that
28126 are executed only if the expression is true (its value is nonzero).
28127 There can then optionally be an @code{else} line, followed by a series
28128 of commands that are only executed if the expression was false. The
28129 end of the list is marked by a line containing @code{end}.
28133 This command allows to write loops. Its syntax is similar to
28134 @code{if}: the command takes a single argument, which is an expression
28135 to evaluate, and must be followed by the commands to execute, one per
28136 line, terminated by an @code{end}. These commands are called the
28137 @dfn{body} of the loop. The commands in the body of @code{while} are
28138 executed repeatedly as long as the expression evaluates to true.
28142 This command exits the @code{while} loop in whose body it is included.
28143 Execution of the script continues after that @code{while}s @code{end}
28146 @kindex loop_continue
28147 @item loop_continue
28148 This command skips the execution of the rest of the body of commands
28149 in the @code{while} loop in whose body it is included. Execution
28150 branches to the beginning of the @code{while} loop, where it evaluates
28151 the controlling expression.
28153 @kindex end@r{ (if/else/while commands)}
28155 Terminate the block of commands that are the body of @code{if},
28156 @code{else}, or @code{while} flow-control commands.
28161 @subsection Commands for Controlled Output
28163 During the execution of a command file or a user-defined command, normal
28164 @value{GDBN} output is suppressed; the only output that appears is what is
28165 explicitly printed by the commands in the definition. This section
28166 describes three commands useful for generating exactly the output you
28171 @item echo @var{text}
28172 @c I do not consider backslash-space a standard C escape sequence
28173 @c because it is not in ANSI.
28174 Print @var{text}. Nonprinting characters can be included in
28175 @var{text} using C escape sequences, such as @samp{\n} to print a
28176 newline. @strong{No newline is printed unless you specify one.}
28177 In addition to the standard C escape sequences, a backslash followed
28178 by a space stands for a space. This is useful for displaying a
28179 string with spaces at the beginning or the end, since leading and
28180 trailing spaces are otherwise trimmed from all arguments.
28181 To print @samp{@w{ }and foo =@w{ }}, use the command
28182 @samp{echo \@w{ }and foo = \@w{ }}.
28184 A backslash at the end of @var{text} can be used, as in C, to continue
28185 the command onto subsequent lines. For example,
28188 echo This is some text\n\
28189 which is continued\n\
28190 onto several lines.\n
28193 produces the same output as
28196 echo This is some text\n
28197 echo which is continued\n
28198 echo onto several lines.\n
28202 @item output @var{expression}
28203 Print the value of @var{expression} and nothing but that value: no
28204 newlines, no @samp{$@var{nn} = }. The value is not entered in the
28205 value history either. @xref{Expressions, ,Expressions}, for more information
28208 @item output/@var{fmt} @var{expression}
28209 Print the value of @var{expression} in format @var{fmt}. You can use
28210 the same formats as for @code{print}. @xref{Output Formats,,Output
28211 Formats}, for more information.
28214 @item printf @var{template}, @var{expressions}@dots{}
28215 Print the values of one or more @var{expressions} under the control of
28216 the string @var{template}. To print several values, make
28217 @var{expressions} be a comma-separated list of individual expressions,
28218 which may be either numbers or pointers. Their values are printed as
28219 specified by @var{template}, exactly as a C program would do by
28220 executing the code below:
28223 printf (@var{template}, @var{expressions}@dots{});
28226 As in @code{C} @code{printf}, ordinary characters in @var{template}
28227 are printed verbatim, while @dfn{conversion specification} introduced
28228 by the @samp{%} character cause subsequent @var{expressions} to be
28229 evaluated, their values converted and formatted according to type and
28230 style information encoded in the conversion specifications, and then
28233 For example, you can print two values in hex like this:
28236 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
28239 @code{printf} supports all the standard @code{C} conversion
28240 specifications, including the flags and modifiers between the @samp{%}
28241 character and the conversion letter, with the following exceptions:
28245 The argument-ordering modifiers, such as @samp{2$}, are not supported.
28248 The modifier @samp{*} is not supported for specifying precision or
28252 The @samp{'} flag (for separation of digits into groups according to
28253 @code{LC_NUMERIC'}) is not supported.
28256 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
28260 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
28263 The conversion letters @samp{a} and @samp{A} are not supported.
28267 Note that the @samp{ll} type modifier is supported only if the
28268 underlying @code{C} implementation used to build @value{GDBN} supports
28269 the @code{long long int} type, and the @samp{L} type modifier is
28270 supported only if @code{long double} type is available.
28272 As in @code{C}, @code{printf} supports simple backslash-escape
28273 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
28274 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
28275 single character. Octal and hexadecimal escape sequences are not
28278 Additionally, @code{printf} supports conversion specifications for DFP
28279 (@dfn{Decimal Floating Point}) types using the following length modifiers
28280 together with a floating point specifier.
28285 @samp{H} for printing @code{Decimal32} types.
28288 @samp{D} for printing @code{Decimal64} types.
28291 @samp{DD} for printing @code{Decimal128} types.
28294 If the underlying @code{C} implementation used to build @value{GDBN} has
28295 support for the three length modifiers for DFP types, other modifiers
28296 such as width and precision will also be available for @value{GDBN} to use.
28298 In case there is no such @code{C} support, no additional modifiers will be
28299 available and the value will be printed in the standard way.
28301 Here's an example of printing DFP types using the above conversion letters:
28303 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
28308 @item eval @var{template}, @var{expressions}@dots{}
28309 Convert the values of one or more @var{expressions} under the control of
28310 the string @var{template} to a command line, and call it.
28314 @node Auto-loading sequences
28315 @subsection Controlling auto-loading native @value{GDBN} scripts
28316 @cindex native script auto-loading
28318 When a new object file is read (for example, due to the @code{file}
28319 command, or because the inferior has loaded a shared library),
28320 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
28321 @xref{Auto-loading extensions}.
28323 Auto-loading can be enabled or disabled,
28324 and the list of auto-loaded scripts can be printed.
28327 @anchor{set auto-load gdb-scripts}
28328 @kindex set auto-load gdb-scripts
28329 @item set auto-load gdb-scripts [on|off]
28330 Enable or disable the auto-loading of canned sequences of commands scripts.
28332 @anchor{show auto-load gdb-scripts}
28333 @kindex show auto-load gdb-scripts
28334 @item show auto-load gdb-scripts
28335 Show whether auto-loading of canned sequences of commands scripts is enabled or
28338 @anchor{info auto-load gdb-scripts}
28339 @kindex info auto-load gdb-scripts
28340 @cindex print list of auto-loaded canned sequences of commands scripts
28341 @item info auto-load gdb-scripts [@var{regexp}]
28342 Print the list of all canned sequences of commands scripts that @value{GDBN}
28346 If @var{regexp} is supplied only canned sequences of commands scripts with
28347 matching names are printed.
28350 @section Command Aliases
28351 @cindex aliases for commands
28353 Aliases allow you to define alternate spellings for existing commands.
28354 For example, if a new @value{GDBN} command defined in Python
28355 (@pxref{Python}) has a long name, it is handy to have an abbreviated
28356 version of it that involves less typing.
28358 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28359 of the @samp{step} command even though it is otherwise an ambiguous
28360 abbreviation of other commands like @samp{set} and @samp{show}.
28362 Aliases are also used to provide shortened or more common versions
28363 of multi-word commands. For example, @value{GDBN} provides the
28364 @samp{tty} alias of the @samp{set inferior-tty} command.
28366 You can define a new alias with the @samp{alias} command.
28371 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28375 @var{alias} specifies the name of the new alias. Each word of
28376 @var{alias} must consist of letters, numbers, dashes and underscores.
28378 @var{command} specifies the name of an existing command
28379 that is being aliased.
28381 @var{command} can also be the name of an existing alias. In this
28382 case, @var{command} cannot be an alias that has default arguments.
28384 The @samp{-a} option specifies that the new alias is an abbreviation
28385 of the command. Abbreviations are not used in command completion.
28387 The @samp{--} option specifies the end of options,
28388 and is useful when @var{alias} begins with a dash.
28390 You can specify @var{default-args} for your alias. These
28391 @var{default-args} will be automatically added before the alias
28392 arguments typed explicitly on the command line.
28394 For example, the below defines an alias @code{btfullall} that shows all local
28395 variables and all frame arguments:
28397 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28400 For more information about @var{default-args}, see @ref{Command
28401 aliases default args, ,Default Arguments}.
28403 Here is a simple example showing how to make an abbreviation of a
28404 command so that there is less to type. Suppose you were tired of
28405 typing @samp{disas}, the current shortest unambiguous abbreviation of
28406 the @samp{disassemble} command and you wanted an even shorter version
28407 named @samp{di}. The following will accomplish this.
28410 (gdb) alias -a di = disas
28413 Note that aliases are different from user-defined commands. With a
28414 user-defined command, you also need to write documentation for it with
28415 the @samp{document} command. An alias automatically picks up the
28416 documentation of the existing command.
28418 Here is an example where we make @samp{elms} an abbreviation of
28419 @samp{elements} in the @samp{set print elements} command.
28420 This is to show that you can make an abbreviation of any part
28424 (gdb) alias -a set print elms = set print elements
28425 (gdb) alias -a show print elms = show print elements
28426 (gdb) set p elms 200
28428 Limit on string chars or array elements to print is 200.
28431 Note that if you are defining an alias of a @samp{set} command,
28432 and you want to have an alias for the corresponding @samp{show}
28433 command, then you need to define the latter separately.
28435 Unambiguously abbreviated commands are allowed in @var{command} and
28436 @var{alias}, just as they are normally.
28439 (gdb) alias -a set pr elms = set p ele
28442 Finally, here is an example showing the creation of a one word
28443 alias for a more complex command.
28444 This creates alias @samp{spe} of the command @samp{set print elements}.
28447 (gdb) alias spe = set print elements
28452 * Command aliases default args:: Default arguments for aliases
28455 @node Command aliases default args
28456 @subsection Default Arguments
28457 @cindex aliases for commands, default arguments
28459 You can tell @value{GDBN} to always prepend some default arguments to
28460 the list of arguments provided explicitly by the user when using a
28461 user-defined alias.
28463 If you repeatedly use the same arguments or options for a command, you
28464 can define an alias for this command and tell @value{GDBN} to
28465 automatically prepend these arguments or options to the list of
28466 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28467 could easily accept default arguments for pre-defined commands and aliases,
28468 but it was deemed this would be confusing, and so is not allowed.}.
28470 For example, if you often use the command @code{thread apply all}
28471 specifying to work on the threads in ascending order and to continue in case it
28472 encounters an error, you can tell @value{GDBN} to automatically preprend
28473 the @code{-ascending} and @code{-c} options by using:
28476 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28479 Once you have defined this alias with its default args, any time you type
28480 the @code{thread apply asc-all} followed by @code{some arguments},
28481 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28483 To have even less to type, you can also define a one word alias:
28485 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28488 As usual, unambiguous abbreviations can be used for @var{alias}
28489 and @var{default-args}.
28491 The different aliases of a command do not share their default args.
28492 For example, you define a new alias @code{bt_ALL} showing all possible
28493 information and another alias @code{bt_SMALL} showing very limited information
28496 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28497 -past-main -past-entry -full
28498 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28499 -past-main off -past-entry off
28502 (For more on using the @code{alias} command, see @ref{Aliases}.)
28504 Default args are not limited to the arguments and options of @var{command},
28505 but can specify nested commands if @var{command} accepts such a nested command
28507 For example, the below defines @code{faalocalsoftype} that lists the
28508 frames having locals of a certain type, together with the matching
28511 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28512 (@value{GDBP}) faalocalsoftype int
28513 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28518 This is also very useful to define an alias for a set of nested @code{with}
28519 commands to have a particular combination of temporary settings. For example,
28520 the below defines the alias @code{pp10} that pretty prints an expression
28521 argument, with a maximum of 10 elements if the expression is a string or
28524 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28526 This defines the alias @code{pp10} as being a sequence of 3 commands.
28527 The first part @code{with print pretty --} temporarily activates the setting
28528 @code{set print pretty}, then launches the command that follows the separator
28530 The command following the first part is also a @code{with} command that
28531 temporarily changes the setting @code{set print elements} to 10, then
28532 launches the command that follows the second separator @code{--}.
28533 The third part @code{print} is the command the @code{pp10} alias will launch,
28534 using the temporary values of the settings and the arguments explicitly given
28536 For more information about the @code{with} command usage,
28537 see @ref{Command Settings}.
28539 @c Python docs live in a separate file.
28540 @include python.texi
28542 @c Guile docs live in a separate file.
28543 @include guile.texi
28545 @node Auto-loading extensions
28546 @section Auto-loading extensions
28547 @cindex auto-loading extensions
28549 @value{GDBN} provides two mechanisms for automatically loading
28550 extensions when a new object file is read (for example, due to the
28551 @code{file} command, or because the inferior has loaded a shared
28552 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28553 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28554 @code{.debug_gdb_scripts} section of modern file formats like ELF
28555 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28556 section}). For a discussion of the differences between these two
28557 approaches see @ref{Which flavor to choose?}.
28559 The auto-loading feature is useful for supplying application-specific
28560 debugging commands and features.
28562 Auto-loading can be enabled or disabled,
28563 and the list of auto-loaded scripts can be printed.
28564 See the @samp{auto-loading} section of each extension language
28565 for more information.
28566 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28567 For Python files see @ref{Python Auto-loading}.
28569 Note that loading of this script file also requires accordingly configured
28570 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28573 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28574 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28575 * Which flavor to choose?:: Choosing between these approaches
28578 @node objfile-gdbdotext file
28579 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28580 @cindex @file{@var{objfile}-gdb.gdb}
28581 @cindex @file{@var{objfile}-gdb.py}
28582 @cindex @file{@var{objfile}-gdb.scm}
28584 When a new object file is read, @value{GDBN} looks for a file named
28585 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28586 where @var{objfile} is the object file's name and
28587 where @var{ext} is the file extension for the extension language:
28590 @item @file{@var{objfile}-gdb.gdb}
28591 GDB's own command language
28592 @item @file{@var{objfile}-gdb.py}
28594 @item @file{@var{objfile}-gdb.scm}
28598 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28599 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28600 components, and appending the @file{-gdb.@var{ext}} suffix.
28601 If this file exists and is readable, @value{GDBN} will evaluate it as a
28602 script in the specified extension language.
28604 If this file does not exist, then @value{GDBN} will look for
28605 @var{script-name} file in all of the directories as specified below.
28606 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28607 directories is converted to a one-letter subdirectory, i.e.@:
28608 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28609 filesystems disallow colons in file names.)
28611 Note that loading of these files requires an accordingly configured
28612 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28614 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28615 scripts normally according to its @file{.exe} filename. But if no scripts are
28616 found @value{GDBN} also tries script filenames matching the object file without
28617 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28618 is attempted on any platform. This makes the script filenames compatible
28619 between Unix and MS-Windows hosts.
28622 @anchor{set auto-load scripts-directory}
28623 @kindex set auto-load scripts-directory
28624 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28625 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28626 may be delimited by the host platform path separator in use
28627 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28629 Each entry here needs to be covered also by the security setting
28630 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28632 @anchor{with-auto-load-dir}
28633 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28634 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28635 configuration option @option{--with-auto-load-dir}.
28637 Any reference to @file{$debugdir} will get replaced by
28638 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28639 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28640 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28641 @file{$datadir} must be placed as a directory component --- either alone or
28642 delimited by @file{/} or @file{\} directory separators, depending on the host
28645 The list of directories uses path separator (@samp{:} on GNU and Unix
28646 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28647 to the @env{PATH} environment variable.
28649 @anchor{show auto-load scripts-directory}
28650 @kindex show auto-load scripts-directory
28651 @item show auto-load scripts-directory
28652 Show @value{GDBN} auto-loaded scripts location.
28654 @anchor{add-auto-load-scripts-directory}
28655 @kindex add-auto-load-scripts-directory
28656 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28657 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28658 Multiple entries may be delimited by the host platform path separator in use.
28661 @value{GDBN} does not track which files it has already auto-loaded this way.
28662 @value{GDBN} will load the associated script every time the corresponding
28663 @var{objfile} is opened.
28664 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28665 is evaluated more than once.
28667 @node dotdebug_gdb_scripts section
28668 @subsection The @code{.debug_gdb_scripts} section
28669 @cindex @code{.debug_gdb_scripts} section
28671 For systems using file formats like ELF and COFF,
28672 when @value{GDBN} loads a new object file
28673 it will look for a special section named @code{.debug_gdb_scripts}.
28674 If this section exists, its contents is a list of null-terminated entries
28675 specifying scripts to load. Each entry begins with a non-null prefix byte that
28676 specifies the kind of entry, typically the extension language and whether the
28677 script is in a file or inlined in @code{.debug_gdb_scripts}.
28679 The following entries are supported:
28682 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28683 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28684 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28685 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28688 @subsubsection Script File Entries
28690 If the entry specifies a file, @value{GDBN} will look for the file first
28691 in the current directory and then along the source search path
28692 (@pxref{Source Path, ,Specifying Source Directories}),
28693 except that @file{$cdir} is not searched, since the compilation
28694 directory is not relevant to scripts.
28696 File entries can be placed in section @code{.debug_gdb_scripts} with,
28697 for example, this GCC macro for Python scripts.
28700 /* Note: The "MS" section flags are to remove duplicates. */
28701 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28703 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28704 .byte 1 /* Python */\n\
28705 .asciz \"" script_name "\"\n\
28711 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28712 Then one can reference the macro in a header or source file like this:
28715 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28718 The script name may include directories if desired.
28720 Note that loading of this script file also requires accordingly configured
28721 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28723 If the macro invocation is put in a header, any application or library
28724 using this header will get a reference to the specified script,
28725 and with the use of @code{"MS"} attributes on the section, the linker
28726 will remove duplicates.
28728 @subsubsection Script Text Entries
28730 Script text entries allow to put the executable script in the entry
28731 itself instead of loading it from a file.
28732 The first line of the entry, everything after the prefix byte and up to
28733 the first newline (@code{0xa}) character, is the script name, and must not
28734 contain any kind of space character, e.g., spaces or tabs.
28735 The rest of the entry, up to the trailing null byte, is the script to
28736 execute in the specified language. The name needs to be unique among
28737 all script names, as @value{GDBN} executes each script only once based
28740 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28744 #include "symcat.h"
28745 #include "gdb/section-scripts.h"
28747 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28748 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28749 ".ascii \"gdb.inlined-script\\n\"\n"
28750 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28751 ".ascii \" def __init__ (self):\\n\"\n"
28752 ".ascii \" super (test_cmd, self).__init__ ("
28753 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28754 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28755 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28756 ".ascii \"test_cmd ()\\n\"\n"
28762 Loading of inlined scripts requires a properly configured
28763 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28764 The path to specify in @code{auto-load safe-path} is the path of the file
28765 containing the @code{.debug_gdb_scripts} section.
28767 @node Which flavor to choose?
28768 @subsection Which flavor to choose?
28770 Given the multiple ways of auto-loading extensions, it might not always
28771 be clear which one to choose. This section provides some guidance.
28774 Benefits of the @file{-gdb.@var{ext}} way:
28778 Can be used with file formats that don't support multiple sections.
28781 Ease of finding scripts for public libraries.
28783 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28784 in the source search path.
28785 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28786 isn't a source directory in which to find the script.
28789 Doesn't require source code additions.
28793 Benefits of the @code{.debug_gdb_scripts} way:
28797 Works with static linking.
28799 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28800 trigger their loading. When an application is statically linked the only
28801 objfile available is the executable, and it is cumbersome to attach all the
28802 scripts from all the input libraries to the executable's
28803 @file{-gdb.@var{ext}} script.
28806 Works with classes that are entirely inlined.
28808 Some classes can be entirely inlined, and thus there may not be an associated
28809 shared library to attach a @file{-gdb.@var{ext}} script to.
28812 Scripts needn't be copied out of the source tree.
28814 In some circumstances, apps can be built out of large collections of internal
28815 libraries, and the build infrastructure necessary to install the
28816 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28817 cumbersome. It may be easier to specify the scripts in the
28818 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28819 top of the source tree to the source search path.
28822 @node Multiple Extension Languages
28823 @section Multiple Extension Languages
28825 The Guile and Python extension languages do not share any state,
28826 and generally do not interfere with each other.
28827 There are some things to be aware of, however.
28829 @subsection Python comes first
28831 Python was @value{GDBN}'s first extension language, and to avoid breaking
28832 existing behaviour Python comes first. This is generally solved by the
28833 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28834 extension languages, and when it makes a call to an extension language,
28835 (say to pretty-print a value), it tries each in turn until an extension
28836 language indicates it has performed the request (e.g., has returned the
28837 pretty-printed form of a value).
28838 This extends to errors while performing such requests: If an error happens
28839 while, for example, trying to pretty-print an object then the error is
28840 reported and any following extension languages are not tried.
28843 @chapter Command Interpreters
28844 @cindex command interpreters
28846 @value{GDBN} supports multiple command interpreters, and some command
28847 infrastructure to allow users or user interface writers to switch
28848 between interpreters or run commands in other interpreters.
28850 @value{GDBN} currently supports two command interpreters, the console
28851 interpreter (sometimes called the command-line interpreter or @sc{cli})
28852 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28853 describes both of these interfaces in great detail.
28855 By default, @value{GDBN} will start with the console interpreter.
28856 However, the user may choose to start @value{GDBN} with another
28857 interpreter by specifying the @option{-i} or @option{--interpreter}
28858 startup options. Defined interpreters include:
28862 @cindex console interpreter
28863 The traditional console or command-line interpreter. This is the most often
28864 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28865 @value{GDBN} will use this interpreter.
28868 @cindex mi interpreter
28869 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28870 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28871 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28875 @cindex mi3 interpreter
28876 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28879 @cindex mi2 interpreter
28880 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28883 @cindex mi1 interpreter
28884 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28888 @cindex invoke another interpreter
28890 @kindex interpreter-exec
28891 You may execute commands in any interpreter from the current
28892 interpreter using the appropriate command. If you are running the
28893 console interpreter, simply use the @code{interpreter-exec} command:
28896 interpreter-exec mi "-data-list-register-names"
28899 @sc{gdb/mi} has a similar command, although it is only available in versions of
28900 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28902 Note that @code{interpreter-exec} only changes the interpreter for the
28903 duration of the specified command. It does not change the interpreter
28906 @cindex start a new independent interpreter
28908 Although you may only choose a single interpreter at startup, it is
28909 possible to run an independent interpreter on a specified input/output
28910 device (usually a tty).
28912 For example, consider a debugger GUI or IDE that wants to provide a
28913 @value{GDBN} console view. It may do so by embedding a terminal
28914 emulator widget in its GUI, starting @value{GDBN} in the traditional
28915 command-line mode with stdin/stdout/stderr redirected to that
28916 terminal, and then creating an MI interpreter running on a specified
28917 input/output device. The console interpreter created by @value{GDBN}
28918 at startup handles commands the user types in the terminal widget,
28919 while the GUI controls and synchronizes state with @value{GDBN} using
28920 the separate MI interpreter.
28922 To start a new secondary @dfn{user interface} running MI, use the
28923 @code{new-ui} command:
28926 @cindex new user interface
28928 new-ui @var{interpreter} @var{tty}
28931 The @var{interpreter} parameter specifies the interpreter to run.
28932 This accepts the same values as the @code{interpreter-exec} command.
28933 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
28934 @var{tty} parameter specifies the name of the bidirectional file the
28935 interpreter uses for input/output, usually the name of a
28936 pseudoterminal slave on Unix systems. For example:
28939 (@value{GDBP}) new-ui mi /dev/pts/9
28943 runs an MI interpreter on @file{/dev/pts/9}.
28946 @chapter @value{GDBN} Text User Interface
28948 @cindex Text User Interface
28950 The @value{GDBN} Text User Interface (TUI) is a terminal
28951 interface which uses the @code{curses} library to show the source
28952 file, the assembly output, the program registers and @value{GDBN}
28953 commands in separate text windows. The TUI mode is supported only
28954 on platforms where a suitable version of the @code{curses} library
28957 The TUI mode is enabled by default when you invoke @value{GDBN} as
28958 @samp{@value{GDBP} -tui}.
28959 You can also switch in and out of TUI mode while @value{GDBN} runs by
28960 using various TUI commands and key bindings, such as @command{tui
28961 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
28962 @ref{TUI Keys, ,TUI Key Bindings}.
28965 * TUI Overview:: TUI overview
28966 * TUI Keys:: TUI key bindings
28967 * TUI Single Key Mode:: TUI single key mode
28968 * TUI Mouse Support:: TUI mouse support
28969 * TUI Commands:: TUI-specific commands
28970 * TUI Configuration:: TUI configuration variables
28974 @section TUI Overview
28976 In TUI mode, @value{GDBN} can display several text windows:
28980 This window is the @value{GDBN} command window with the @value{GDBN}
28981 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28982 managed using readline.
28985 The source window shows the source file of the program. The current
28986 line and active breakpoints are displayed in this window.
28989 The assembly window shows the disassembly output of the program.
28992 This window shows the processor registers. Registers are highlighted
28993 when their values change.
28996 The source and assembly windows show the current program position
28997 by highlighting the current line and marking it with a @samp{>} marker.
28998 Breakpoints are indicated with two markers. The first marker
28999 indicates the breakpoint type:
29003 Breakpoint which was hit at least once.
29006 Breakpoint which was never hit.
29009 Hardware breakpoint which was hit at least once.
29012 Hardware breakpoint which was never hit.
29015 The second marker indicates whether the breakpoint is enabled or not:
29019 Breakpoint is enabled.
29022 Breakpoint is disabled.
29025 The source, assembly and register windows are updated when the current
29026 thread changes, when the frame changes, or when the program counter
29029 These windows are not all visible at the same time. The command
29030 window is always visible. The others can be arranged in several
29041 source and assembly,
29044 source and registers, or
29047 assembly and registers.
29050 These are the standard layouts, but other layouts can be defined.
29052 A status line above the command window shows the following information:
29056 Indicates the current @value{GDBN} target.
29057 (@pxref{Targets, ,Specifying a Debugging Target}).
29060 Gives the current process or thread number.
29061 When no process is being debugged, this field is set to @code{No process}.
29064 Gives the current function name for the selected frame.
29065 The name is demangled if demangling is turned on (@pxref{Print Settings}).
29066 When there is no symbol corresponding to the current program counter,
29067 the string @code{??} is displayed.
29070 Indicates the current line number for the selected frame.
29071 When the current line number is not known, the string @code{??} is displayed.
29074 Indicates the current program counter address.
29078 @section TUI Key Bindings
29079 @cindex TUI key bindings
29081 The TUI installs several key bindings in the readline keymaps
29082 @ifset SYSTEM_READLINE
29083 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
29085 @ifclear SYSTEM_READLINE
29086 (@pxref{Command Line Editing}).
29088 The following key bindings are installed for both TUI mode and the
29089 @value{GDBN} standard mode.
29098 Enter or leave the TUI mode. When leaving the TUI mode,
29099 the curses window management stops and @value{GDBN} operates using
29100 its standard mode, writing on the terminal directly. When reentering
29101 the TUI mode, control is given back to the curses windows.
29102 The screen is then refreshed.
29104 This key binding uses the bindable Readline function
29105 @code{tui-switch-mode}.
29109 Use a TUI layout with only one window. The layout will
29110 either be @samp{source} or @samp{assembly}. When the TUI mode
29111 is not active, it will switch to the TUI mode.
29113 Think of this key binding as the Emacs @kbd{C-x 1} binding.
29115 This key binding uses the bindable Readline function
29116 @code{tui-delete-other-windows}.
29120 Use a TUI layout with at least two windows. When the current
29121 layout already has two windows, the next layout with two windows is used.
29122 When a new layout is chosen, one window will always be common to the
29123 previous layout and the new one.
29125 Think of it as the Emacs @kbd{C-x 2} binding.
29127 This key binding uses the bindable Readline function
29128 @code{tui-change-windows}.
29132 Change the active window. The TUI associates several key bindings
29133 (like scrolling and arrow keys) with the active window. This command
29134 gives the focus to the next TUI window.
29136 Think of it as the Emacs @kbd{C-x o} binding.
29138 This key binding uses the bindable Readline function
29139 @code{tui-other-window}.
29143 Switch in and out of the TUI SingleKey mode that binds single
29144 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
29146 This key binding uses the bindable Readline function
29147 @code{next-keymap}.
29150 The following key bindings only work in the TUI mode:
29155 Scroll the active window one page up.
29159 Scroll the active window one page down.
29163 Scroll the active window one line up.
29167 Scroll the active window one line down.
29171 Scroll the active window one column left.
29175 Scroll the active window one column right.
29179 Refresh the screen.
29182 Because the arrow keys scroll the active window in the TUI mode, they
29183 are not available for their normal use by readline unless the command
29184 window has the focus. When another window is active, you must use
29185 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
29186 and @kbd{C-f} to control the command window.
29188 @node TUI Single Key Mode
29189 @section TUI Single Key Mode
29190 @cindex TUI single key mode
29192 The TUI also provides a @dfn{SingleKey} mode, which binds several
29193 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
29194 switch into this mode, where the following key bindings are used:
29197 @kindex c @r{(SingleKey TUI key)}
29201 @kindex d @r{(SingleKey TUI key)}
29205 @kindex f @r{(SingleKey TUI key)}
29209 @kindex n @r{(SingleKey TUI key)}
29213 @kindex o @r{(SingleKey TUI key)}
29215 nexti. The shortcut letter @samp{o} stands for ``step Over''.
29217 @kindex q @r{(SingleKey TUI key)}
29219 exit the SingleKey mode.
29221 @kindex r @r{(SingleKey TUI key)}
29225 @kindex s @r{(SingleKey TUI key)}
29229 @kindex i @r{(SingleKey TUI key)}
29231 stepi. The shortcut letter @samp{i} stands for ``step Into''.
29233 @kindex u @r{(SingleKey TUI key)}
29237 @kindex v @r{(SingleKey TUI key)}
29241 @kindex w @r{(SingleKey TUI key)}
29246 Other keys temporarily switch to the @value{GDBN} command prompt.
29247 The key that was pressed is inserted in the editing buffer so that
29248 it is possible to type most @value{GDBN} commands without interaction
29249 with the TUI SingleKey mode. Once the command is entered the TUI
29250 SingleKey mode is restored. The only way to permanently leave
29251 this mode is by typing @kbd{q} or @kbd{C-x s}.
29253 @cindex SingleKey keymap name
29254 If @value{GDBN} was built with Readline 8.0 or later, the TUI
29255 SingleKey keymap will be named @samp{SingleKey}. This can be used in
29256 @file{.inputrc} to add additional bindings to this keymap.
29258 @node TUI Mouse Support
29259 @section TUI Mouse Support
29260 @cindex TUI mouse support
29262 If the curses library supports the mouse, the TUI supports mouse
29265 The mouse wheel scrolls the appropriate window under the mouse cursor.
29267 The TUI itself does not directly support copying/pasting with the
29268 mouse. However, on Unix terminals, you can typically press and hold
29269 the @key{SHIFT} key on your keyboard to temporarily bypass
29270 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
29271 functionality (commonly, click-drag-release or double-click to select
29272 text, middle-click to paste). This copy/paste works with the
29273 terminal's selection buffer, as opposed to the TUI's buffer.
29276 @section TUI-specific Commands
29277 @cindex TUI commands
29279 The TUI has specific commands to control the text windows.
29280 These commands are always available, even when @value{GDBN} is not in
29281 the TUI mode. When @value{GDBN} is in the standard mode, most
29282 of these commands will automatically switch to the TUI mode.
29284 Note that if @value{GDBN}'s @code{stdout} is not connected to a
29285 terminal, or @value{GDBN} has been started with the machine interface
29286 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
29287 these commands will fail with an error, because it would not be
29288 possible or desirable to enable curses window management.
29293 Activate TUI mode. The last active TUI window layout will be used if
29294 TUI mode has previously been used in the current debugging session,
29295 otherwise a default layout is used.
29298 @kindex tui disable
29299 Disable TUI mode, returning to the console interpreter.
29301 @anchor{info_win_command}
29304 List the names and sizes of all currently displayed windows.
29306 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
29307 @kindex tui new-layout
29308 Create a new TUI layout. The new layout will be named @var{name}, and
29309 can be accessed using the @code{layout} command (see below).
29311 Each @var{window} parameter is either the name of a window to display,
29312 or a window description. The windows will be displayed from top to
29313 bottom in the order listed.
29315 The names of the windows are the same as the ones given to the
29316 @code{focus} command (see below); additional, the @code{status}
29317 window can be specified. Note that, because it is of fixed height,
29318 the weight assigned to the status window is of no importance. It is
29319 conventional to use @samp{0} here.
29321 A window description looks a bit like an invocation of @code{tui
29322 new-layout}, and is of the form
29323 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
29325 This specifies a sub-layout. If @code{-horizontal} is given, the
29326 windows in this description will be arranged side-by-side, rather than
29329 Each @var{weight} is an integer. It is the weight of this window
29330 relative to all the other windows in the layout. These numbers are
29331 used to calculate how much of the screen is given to each window.
29336 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
29339 Here, the new layout is called @samp{example}. It shows the source
29340 and register windows, followed by the status window, and then finally
29341 the command window. The non-status windows all have the same weight,
29342 so the terminal will be split into three roughly equal sections.
29344 Here is a more complex example, showing a horizontal layout:
29347 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
29350 This will result in side-by-side source and assembly windows; with the
29351 status and command window being beneath these, filling the entire
29352 width of the terminal. Because they have weight 2, the source and
29353 assembly windows will be twice the height of the command window.
29357 @item tui layout @var{name}
29358 @itemx layout @var{name}
29359 Changes which TUI windows are displayed. The @var{name} parameter
29360 controls which layout is shown. It can be either one of the built-in
29361 layout names, or the name of a layout defined by the user using
29362 @code{tui new-layout}.
29364 The built-in layouts are as follows:
29368 Display the next layout.
29371 Display the previous layout.
29374 Display the source and command windows.
29377 Display the assembly and command windows.
29380 Display the source, assembly, and command windows.
29383 When in @code{src} layout display the register, source, and command
29384 windows. When in @code{asm} or @code{split} layout display the
29385 register, assembler, and command windows.
29389 @item tui focus @var{name}
29390 @itemx focus @var{name}
29391 Changes which TUI window is currently active for scrolling. The
29392 @var{name} parameter can be any of the following:
29396 Make the next window active for scrolling.
29399 Make the previous window active for scrolling.
29402 Make the source window active for scrolling.
29405 Make the assembly window active for scrolling.
29408 Make the register window active for scrolling.
29411 Make the command window active for scrolling.
29414 @kindex tui refresh
29418 Refresh the screen. This is similar to typing @kbd{C-L}.
29420 @item tui reg @var{group}
29422 Changes the register group displayed in the tui register window to
29423 @var{group}. If the register window is not currently displayed this
29424 command will cause the register window to be displayed. The list of
29425 register groups, as well as their order is target specific. The
29426 following groups are available on most targets:
29429 Repeatedly selecting this group will cause the display to cycle
29430 through all of the available register groups.
29433 Repeatedly selecting this group will cause the display to cycle
29434 through all of the available register groups in the reverse order to
29438 Display the general registers.
29440 Display the floating point registers.
29442 Display the system registers.
29444 Display the vector registers.
29446 Display all registers.
29451 Update the source window and the current execution point.
29453 @kindex tui window height
29455 @item tui window height @var{name} +@var{count}
29456 @itemx tui window height @var{name} -@var{count}
29457 @itemx winheight @var{name} +@var{count}
29458 @itemx winheight @var{name} -@var{count}
29459 Change the height of the window @var{name} by @var{count} lines.
29460 Positive counts increase the height, while negative counts decrease
29461 it. The @var{name} parameter can be the name of any currently visible
29462 window. The names of the currently visible windows can be discovered
29463 using @kbd{info win} (@pxref{info_win_command,,info win}).
29465 The set of currently visible windows must always fill the terminal,
29466 and so, it is only possible to resize on window if there are other
29467 visible windows that can either give or receive the extra terminal
29470 @kindex tui window width
29472 @item tui window width @var{name} +@var{count}
29473 @itemx tui window width @var{name} -@var{count}
29474 @itemx winwidth @var{name} +@var{count}
29475 @itemx winwidth @var{name} -@var{count}
29476 Change the width of the window @var{name} by @var{count} columns.
29477 Positive counts increase the width, while negative counts decrease it.
29478 The @var{name} parameter can be the name of any currently visible
29479 window. The names of the currently visible windows can be discovered
29480 using @code{info win} (@pxref{info_win_command,,info win}).
29482 The set of currently visible windows must always fill the terminal,
29483 and so, it is only possible to resize on window if there are other
29484 visible windows that can either give or receive the extra terminal
29488 @node TUI Configuration
29489 @section TUI Configuration Variables
29490 @cindex TUI configuration variables
29492 Several configuration variables control the appearance of TUI windows.
29495 @item set tui border-kind @var{kind}
29496 @kindex set tui border-kind
29497 Select the border appearance for the source, assembly and register windows.
29498 The possible values are the following:
29501 Use a space character to draw the border.
29504 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29507 Use the Alternate Character Set to draw the border. The border is
29508 drawn using character line graphics if the terminal supports them.
29511 @item set tui border-mode @var{mode}
29512 @kindex set tui border-mode
29513 @itemx set tui active-border-mode @var{mode}
29514 @kindex set tui active-border-mode
29515 Select the display attributes for the borders of the inactive windows
29516 or the active window. The @var{mode} can be one of the following:
29519 Use normal attributes to display the border.
29525 Use reverse video mode.
29528 Use half bright mode.
29530 @item half-standout
29531 Use half bright and standout mode.
29534 Use extra bright or bold mode.
29536 @item bold-standout
29537 Use extra bright or bold and standout mode.
29540 @item set tui tab-width @var{nchars}
29541 @kindex set tui tab-width
29543 Set the width of tab stops to be @var{nchars} characters. This
29544 setting affects the display of TAB characters in the source and
29547 @item set tui compact-source @r{[}on@r{|}off@r{]}
29548 @kindex set tui compact-source
29549 Set whether the TUI source window is displayed in ``compact'' form.
29550 The default display uses more space for line numbers and starts the
29551 source text at the next tab stop; the compact display uses only as
29552 much space as is needed for the line numbers in the current file, and
29553 only a single space to separate the line numbers from the source.
29555 @kindex set debug tui
29556 @item set debug tui @r{[}on|off@r{]}
29557 Turn on or off display of @value{GDBN} internal debug messages relating
29560 @kindex show debug tui
29561 @item show debug tui
29562 Show the current status of displaying @value{GDBN} internal debug
29563 messages relating to the TUI.
29567 Note that the colors of the TUI borders can be controlled using the
29568 appropriate @code{set style} commands. @xref{Output Styling}.
29571 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29574 @cindex @sc{gnu} Emacs
29575 A special interface allows you to use @sc{gnu} Emacs to view (and
29576 edit) the source files for the program you are debugging with
29579 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29580 executable file you want to debug as an argument. This command starts
29581 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29582 created Emacs buffer.
29583 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29585 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29590 All ``terminal'' input and output goes through an Emacs buffer, called
29593 This applies both to @value{GDBN} commands and their output, and to the input
29594 and output done by the program you are debugging.
29596 This is useful because it means that you can copy the text of previous
29597 commands and input them again; you can even use parts of the output
29600 All the facilities of Emacs' Shell mode are available for interacting
29601 with your program. In particular, you can send signals the usual
29602 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29606 @value{GDBN} displays source code through Emacs.
29608 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29609 source file for that frame and puts an arrow (@samp{=>}) at the
29610 left margin of the current line. Emacs uses a separate buffer for
29611 source display, and splits the screen to show both your @value{GDBN} session
29614 Explicit @value{GDBN} @code{list} or search commands still produce output as
29615 usual, but you probably have no reason to use them from Emacs.
29618 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29619 a graphical mode, enabled by default, which provides further buffers
29620 that can control the execution and describe the state of your program.
29621 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29623 If you specify an absolute file name when prompted for the @kbd{M-x
29624 gdb} argument, then Emacs sets your current working directory to where
29625 your program resides. If you only specify the file name, then Emacs
29626 sets your current working directory to the directory associated
29627 with the previous buffer. In this case, @value{GDBN} may find your
29628 program by searching your environment's @env{PATH} variable, but on
29629 some operating systems it might not find the source. So, although the
29630 @value{GDBN} input and output session proceeds normally, the auxiliary
29631 buffer does not display the current source and line of execution.
29633 The initial working directory of @value{GDBN} is printed on the top
29634 line of the GUD buffer and this serves as a default for the commands
29635 that specify files for @value{GDBN} to operate on. @xref{Files,
29636 ,Commands to Specify Files}.
29638 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29639 need to call @value{GDBN} by a different name (for example, if you
29640 keep several configurations around, with different names) you can
29641 customize the Emacs variable @code{gud-gdb-command-name} to run the
29644 In the GUD buffer, you can use these special Emacs commands in
29645 addition to the standard Shell mode commands:
29649 Describe the features of Emacs' GUD Mode.
29652 Execute to another source line, like the @value{GDBN} @code{step} command; also
29653 update the display window to show the current file and location.
29656 Execute to next source line in this function, skipping all function
29657 calls, like the @value{GDBN} @code{next} command. Then update the display window
29658 to show the current file and location.
29661 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29662 display window accordingly.
29665 Execute until exit from the selected stack frame, like the @value{GDBN}
29666 @code{finish} command.
29669 Continue execution of your program, like the @value{GDBN} @code{continue}
29673 Go up the number of frames indicated by the numeric argument
29674 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29675 like the @value{GDBN} @code{up} command.
29678 Go down the number of frames indicated by the numeric argument, like the
29679 @value{GDBN} @code{down} command.
29682 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29683 tells @value{GDBN} to set a breakpoint on the source line point is on.
29685 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29686 separate frame which shows a backtrace when the GUD buffer is current.
29687 Move point to any frame in the stack and type @key{RET} to make it
29688 become the current frame and display the associated source in the
29689 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29690 selected frame become the current one. In graphical mode, the
29691 speedbar displays watch expressions.
29693 If you accidentally delete the source-display buffer, an easy way to get
29694 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29695 request a frame display; when you run under Emacs, this recreates
29696 the source buffer if necessary to show you the context of the current
29699 The source files displayed in Emacs are in ordinary Emacs buffers
29700 which are visiting the source files in the usual way. You can edit
29701 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29702 communicates with Emacs in terms of line numbers. If you add or
29703 delete lines from the text, the line numbers that @value{GDBN} knows cease
29704 to correspond properly with the code.
29706 A more detailed description of Emacs' interaction with @value{GDBN} is
29707 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29711 @chapter The @sc{gdb/mi} Interface
29713 @unnumberedsec Function and Purpose
29715 @cindex @sc{gdb/mi}, its purpose
29716 @sc{gdb/mi} is a line based machine oriented text interface to
29717 @value{GDBN} and is activated by specifying using the
29718 @option{--interpreter} command line option (@pxref{Mode Options}). It
29719 is specifically intended to support the development of systems which
29720 use the debugger as just one small component of a larger system.
29722 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29723 in the form of a reference manual.
29725 Note that @sc{gdb/mi} is still under construction, so some of the
29726 features described below are incomplete and subject to change
29727 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29729 @unnumberedsec Notation and Terminology
29731 @cindex notational conventions, for @sc{gdb/mi}
29732 This chapter uses the following notation:
29736 @code{|} separates two alternatives.
29739 @code{[ @var{something} ]} indicates that @var{something} is optional:
29740 it may or may not be given.
29743 @code{( @var{group} )*} means that @var{group} inside the parentheses
29744 may repeat zero or more times.
29747 @code{( @var{group} )+} means that @var{group} inside the parentheses
29748 may repeat one or more times.
29751 @code{"@var{string}"} means a literal @var{string}.
29755 @heading Dependencies
29759 * GDB/MI General Design::
29760 * GDB/MI Command Syntax::
29761 * GDB/MI Compatibility with CLI::
29762 * GDB/MI Development and Front Ends::
29763 * GDB/MI Output Records::
29764 * GDB/MI Simple Examples::
29765 * GDB/MI Command Description Format::
29766 * GDB/MI Breakpoint Commands::
29767 * GDB/MI Catchpoint Commands::
29768 * GDB/MI Program Context::
29769 * GDB/MI Thread Commands::
29770 * GDB/MI Ada Tasking Commands::
29771 * GDB/MI Program Execution::
29772 * GDB/MI Stack Manipulation::
29773 * GDB/MI Variable Objects::
29774 * GDB/MI Data Manipulation::
29775 * GDB/MI Tracepoint Commands::
29776 * GDB/MI Symbol Query::
29777 * GDB/MI File Commands::
29779 * GDB/MI Kod Commands::
29780 * GDB/MI Memory Overlay Commands::
29781 * GDB/MI Signal Handling Commands::
29783 * GDB/MI Target Manipulation::
29784 * GDB/MI File Transfer Commands::
29785 * GDB/MI Ada Exceptions Commands::
29786 * GDB/MI Support Commands::
29787 * GDB/MI Miscellaneous Commands::
29790 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29791 @node GDB/MI General Design
29792 @section @sc{gdb/mi} General Design
29793 @cindex GDB/MI General Design
29795 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29796 parts---commands sent to @value{GDBN}, responses to those commands
29797 and notifications. Each command results in exactly one response,
29798 indicating either successful completion of the command, or an error.
29799 For the commands that do not resume the target, the response contains the
29800 requested information. For the commands that resume the target, the
29801 response only indicates whether the target was successfully resumed.
29802 Notifications is the mechanism for reporting changes in the state of the
29803 target, or in @value{GDBN} state, that cannot conveniently be associated with
29804 a command and reported as part of that command response.
29806 The important examples of notifications are:
29810 Exec notifications. These are used to report changes in
29811 target state---when a target is resumed, or stopped. It would not
29812 be feasible to include this information in response of resuming
29813 commands, because one resume commands can result in multiple events in
29814 different threads. Also, quite some time may pass before any event
29815 happens in the target, while a frontend needs to know whether the resuming
29816 command itself was successfully executed.
29819 Console output, and status notifications. Console output
29820 notifications are used to report output of CLI commands, as well as
29821 diagnostics for other commands. Status notifications are used to
29822 report the progress of a long-running operation. Naturally, including
29823 this information in command response would mean no output is produced
29824 until the command is finished, which is undesirable.
29827 General notifications. Commands may have various side effects on
29828 the @value{GDBN} or target state beyond their official purpose. For example,
29829 a command may change the selected thread. Although such changes can
29830 be included in command response, using notification allows for more
29831 orthogonal frontend design.
29835 There's no guarantee that whenever an MI command reports an error,
29836 @value{GDBN} or the target are in any specific state, and especially,
29837 the state is not reverted to the state before the MI command was
29838 processed. Therefore, whenever an MI command results in an error,
29839 we recommend that the frontend refreshes all the information shown in
29840 the user interface.
29844 * Context management::
29845 * Asynchronous and non-stop modes::
29849 @node Context management
29850 @subsection Context management
29852 @subsubsection Threads and Frames
29854 In most cases when @value{GDBN} accesses the target, this access is
29855 done in context of a specific thread and frame (@pxref{Frames}).
29856 Often, even when accessing global data, the target requires that a thread
29857 be specified. The CLI interface maintains the selected thread and frame,
29858 and supplies them to target on each command. This is convenient,
29859 because a command line user would not want to specify that information
29860 explicitly on each command, and because user interacts with
29861 @value{GDBN} via a single terminal, so no confusion is possible as
29862 to what thread and frame are the current ones.
29864 In the case of MI, the concept of selected thread and frame is less
29865 useful. First, a frontend can easily remember this information
29866 itself. Second, a graphical frontend can have more than one window,
29867 each one used for debugging a different thread, and the frontend might
29868 want to access additional threads for internal purposes. This
29869 increases the risk that by relying on implicitly selected thread, the
29870 frontend may be operating on a wrong one. Therefore, each MI command
29871 should explicitly specify which thread and frame to operate on. To
29872 make it possible, each MI command accepts the @samp{--thread} and
29873 @samp{--frame} options, the value to each is @value{GDBN} global
29874 identifier for thread and frame to operate on.
29876 Usually, each top-level window in a frontend allows the user to select
29877 a thread and a frame, and remembers the user selection for further
29878 operations. However, in some cases @value{GDBN} may suggest that the
29879 current thread or frame be changed. For example, when stopping on a
29880 breakpoint it is reasonable to switch to the thread where breakpoint is
29881 hit. For another example, if the user issues the CLI @samp{thread} or
29882 @samp{frame} commands via the frontend, it is desirable to change the
29883 frontend's selection to the one specified by user. @value{GDBN}
29884 communicates the suggestion to change current thread and frame using the
29885 @samp{=thread-selected} notification.
29887 Note that historically, MI shares the selected thread with CLI, so
29888 frontends used the @code{-thread-select} to execute commands in the
29889 right context. However, getting this to work right is cumbersome. The
29890 simplest way is for frontend to emit @code{-thread-select} command
29891 before every command. This doubles the number of commands that need
29892 to be sent. The alternative approach is to suppress @code{-thread-select}
29893 if the selected thread in @value{GDBN} is supposed to be identical to the
29894 thread the frontend wants to operate on. However, getting this
29895 optimization right can be tricky. In particular, if the frontend
29896 sends several commands to @value{GDBN}, and one of the commands changes the
29897 selected thread, then the behaviour of subsequent commands will
29898 change. So, a frontend should either wait for response from such
29899 problematic commands, or explicitly add @code{-thread-select} for
29900 all subsequent commands. No frontend is known to do this exactly
29901 right, so it is suggested to just always pass the @samp{--thread} and
29902 @samp{--frame} options.
29904 @subsubsection Language
29906 The execution of several commands depends on which language is selected.
29907 By default, the current language (@pxref{show language}) is used.
29908 But for commands known to be language-sensitive, it is recommended
29909 to use the @samp{--language} option. This option takes one argument,
29910 which is the name of the language to use while executing the command.
29914 -data-evaluate-expression --language c "sizeof (void*)"
29919 The valid language names are the same names accepted by the
29920 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29921 @samp{local} or @samp{unknown}.
29923 @node Asynchronous and non-stop modes
29924 @subsection Asynchronous command execution and non-stop mode
29926 On some targets, @value{GDBN} is capable of processing MI commands
29927 even while the target is running. This is called @dfn{asynchronous
29928 command execution} (@pxref{Background Execution}). The frontend may
29929 specify a preference for asynchronous execution using the
29930 @code{-gdb-set mi-async 1} command, which should be emitted before
29931 either running the executable or attaching to the target. After the
29932 frontend has started the executable or attached to the target, it can
29933 find if asynchronous execution is enabled using the
29934 @code{-list-target-features} command.
29937 @cindex foreground execution
29938 @cindex background execution
29939 @cindex asynchronous execution
29940 @cindex execution, foreground, background and asynchronous
29941 @kindex set mi-async
29942 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
29943 Set whether MI is in asynchronous mode.
29945 When @code{off}, which is the default, MI execution commands (e.g.,
29946 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
29947 for the program to stop before processing further commands.
29949 When @code{on}, MI execution commands are background execution
29950 commands (e.g., @code{-exec-continue} becomes the equivalent of the
29951 @code{c&} CLI command), and so @value{GDBN} is capable of processing
29952 MI commands even while the target is running.
29954 @kindex show mi-async
29955 @item -gdb-show mi-async
29956 Show whether MI asynchronous mode is enabled.
29959 Note: In @value{GDBN} version 7.7 and earlier, this option was called
29960 @code{target-async} instead of @code{mi-async}, and it had the effect
29961 of both putting MI in asynchronous mode and making CLI background
29962 commands possible. CLI background commands are now always possible
29963 ``out of the box'' if the target supports them. The old spelling is
29964 kept as a deprecated alias for backwards compatibility.
29966 Even if @value{GDBN} can accept a command while target is running,
29967 many commands that access the target do not work when the target is
29968 running. Therefore, asynchronous command execution is most useful
29969 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29970 it is possible to examine the state of one thread, while other threads
29973 When a given thread is running, MI commands that try to access the
29974 target in the context of that thread may not work, or may work only on
29975 some targets. In particular, commands that try to operate on thread's
29976 stack will not work, on any target. Commands that read memory, or
29977 modify breakpoints, may work or not work, depending on the target. Note
29978 that even commands that operate on global state, such as @code{print},
29979 @code{set}, and breakpoint commands, still access the target in the
29980 context of a specific thread, so frontend should try to find a
29981 stopped thread and perform the operation on that thread (using the
29982 @samp{--thread} option).
29984 Which commands will work in the context of a running thread is
29985 highly target dependent. However, the two commands
29986 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29987 to find the state of a thread, will always work.
29989 @node Thread groups
29990 @subsection Thread groups
29991 @value{GDBN} may be used to debug several processes at the same time.
29992 On some platforms, @value{GDBN} may support debugging of several
29993 hardware systems, each one having several cores with several different
29994 processes running on each core. This section describes the MI
29995 mechanism to support such debugging scenarios.
29997 The key observation is that regardless of the structure of the
29998 target, MI can have a global list of threads, because most commands that
29999 accept the @samp{--thread} option do not need to know what process that
30000 thread belongs to. Therefore, it is not necessary to introduce
30001 neither additional @samp{--process} option, nor an notion of the
30002 current process in the MI interface. The only strictly new feature
30003 that is required is the ability to find how the threads are grouped
30006 To allow the user to discover such grouping, and to support arbitrary
30007 hierarchy of machines/cores/processes, MI introduces the concept of a
30008 @dfn{thread group}. Thread group is a collection of threads and other
30009 thread groups. A thread group always has a string identifier, a type,
30010 and may have additional attributes specific to the type. A new
30011 command, @code{-list-thread-groups}, returns the list of top-level
30012 thread groups, which correspond to processes that @value{GDBN} is
30013 debugging at the moment. By passing an identifier of a thread group
30014 to the @code{-list-thread-groups} command, it is possible to obtain
30015 the members of specific thread group.
30017 To allow the user to easily discover processes, and other objects, he
30018 wishes to debug, a concept of @dfn{available thread group} is
30019 introduced. Available thread group is an thread group that
30020 @value{GDBN} is not debugging, but that can be attached to, using the
30021 @code{-target-attach} command. The list of available top-level thread
30022 groups can be obtained using @samp{-list-thread-groups --available}.
30023 In general, the content of a thread group may be only retrieved only
30024 after attaching to that thread group.
30026 Thread groups are related to inferiors (@pxref{Inferiors Connections and
30027 Programs}). Each inferior corresponds to a thread group of a special
30028 type @samp{process}, and some additional operations are permitted on
30029 such thread groups.
30031 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30032 @node GDB/MI Command Syntax
30033 @section @sc{gdb/mi} Command Syntax
30036 * GDB/MI Input Syntax::
30037 * GDB/MI Output Syntax::
30040 @node GDB/MI Input Syntax
30041 @subsection @sc{gdb/mi} Input Syntax
30043 @cindex input syntax for @sc{gdb/mi}
30044 @cindex @sc{gdb/mi}, input syntax
30046 @item @var{command} @expansion{}
30047 @code{@var{cli-command} | @var{mi-command}}
30049 @item @var{cli-command} @expansion{}
30050 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
30051 @var{cli-command} is any existing @value{GDBN} CLI command.
30053 @item @var{mi-command} @expansion{}
30054 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
30055 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
30057 @item @var{token} @expansion{}
30058 "any sequence of digits"
30060 @item @var{option} @expansion{}
30061 @code{"-" @var{parameter} [ " " @var{parameter} ]}
30063 @item @var{parameter} @expansion{}
30064 @code{@var{non-blank-sequence} | @var{c-string}}
30066 @item @var{operation} @expansion{}
30067 @emph{any of the operations described in this chapter}
30069 @item @var{non-blank-sequence} @expansion{}
30070 @emph{anything, provided it doesn't contain special characters such as
30071 "-", @var{nl}, """ and of course " "}
30073 @item @var{c-string} @expansion{}
30074 @code{""" @var{seven-bit-iso-c-string-content} """}
30076 @item @var{nl} @expansion{}
30085 The CLI commands are still handled by the @sc{mi} interpreter; their
30086 output is described below.
30089 The @code{@var{token}}, when present, is passed back when the command
30093 Some @sc{mi} commands accept optional arguments as part of the parameter
30094 list. Each option is identified by a leading @samp{-} (dash) and may be
30095 followed by an optional argument parameter. Options occur first in the
30096 parameter list and can be delimited from normal parameters using
30097 @samp{--} (this is useful when some parameters begin with a dash).
30104 We want easy access to the existing CLI syntax (for debugging).
30107 We want it to be easy to spot a @sc{mi} operation.
30110 @node GDB/MI Output Syntax
30111 @subsection @sc{gdb/mi} Output Syntax
30113 @cindex output syntax of @sc{gdb/mi}
30114 @cindex @sc{gdb/mi}, output syntax
30115 The output from @sc{gdb/mi} consists of zero or more out-of-band records
30116 followed, optionally, by a single result record. This result record
30117 is for the most recent command. The sequence of output records is
30118 terminated by @samp{(gdb)}.
30120 If an input command was prefixed with a @code{@var{token}} then the
30121 corresponding output for that command will also be prefixed by that same
30125 @item @var{output} @expansion{}
30126 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
30128 @item @var{result-record} @expansion{}
30129 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
30131 @item @var{out-of-band-record} @expansion{}
30132 @code{@var{async-record} | @var{stream-record}}
30134 @item @var{async-record} @expansion{}
30135 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
30137 @item @var{exec-async-output} @expansion{}
30138 @code{[ @var{token} ] "*" @var{async-output nl}}
30140 @item @var{status-async-output} @expansion{}
30141 @code{[ @var{token} ] "+" @var{async-output nl}}
30143 @item @var{notify-async-output} @expansion{}
30144 @code{[ @var{token} ] "=" @var{async-output nl}}
30146 @item @var{async-output} @expansion{}
30147 @code{@var{async-class} ( "," @var{result} )*}
30149 @item @var{result-class} @expansion{}
30150 @code{"done" | "running" | "connected" | "error" | "exit"}
30152 @item @var{async-class} @expansion{}
30153 @code{"stopped" | @var{others}} (where @var{others} will be added
30154 depending on the needs---this is still in development).
30156 @item @var{result} @expansion{}
30157 @code{ @var{variable} "=" @var{value}}
30159 @item @var{variable} @expansion{}
30160 @code{ @var{string} }
30162 @item @var{value} @expansion{}
30163 @code{ @var{const} | @var{tuple} | @var{list} }
30165 @item @var{const} @expansion{}
30166 @code{@var{c-string}}
30168 @item @var{tuple} @expansion{}
30169 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
30171 @item @var{list} @expansion{}
30172 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
30173 @var{result} ( "," @var{result} )* "]" }
30175 @item @var{stream-record} @expansion{}
30176 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
30178 @item @var{console-stream-output} @expansion{}
30179 @code{"~" @var{c-string nl}}
30181 @item @var{target-stream-output} @expansion{}
30182 @code{"@@" @var{c-string nl}}
30184 @item @var{log-stream-output} @expansion{}
30185 @code{"&" @var{c-string nl}}
30187 @item @var{nl} @expansion{}
30190 @item @var{token} @expansion{}
30191 @emph{any sequence of digits}.
30199 All output sequences end in a single line containing a period.
30202 The @code{@var{token}} is from the corresponding request. Note that
30203 for all async output, while the token is allowed by the grammar and
30204 may be output by future versions of @value{GDBN} for select async
30205 output messages, it is generally omitted. Frontends should treat
30206 all async output as reporting general changes in the state of the
30207 target and there should be no need to associate async output to any
30211 @cindex status output in @sc{gdb/mi}
30212 @var{status-async-output} contains on-going status information about the
30213 progress of a slow operation. It can be discarded. All status output is
30214 prefixed by @samp{+}.
30217 @cindex async output in @sc{gdb/mi}
30218 @var{exec-async-output} contains asynchronous state change on the target
30219 (stopped, started, disappeared). All async output is prefixed by
30223 @cindex notify output in @sc{gdb/mi}
30224 @var{notify-async-output} contains supplementary information that the
30225 client should handle (e.g., a new breakpoint information). All notify
30226 output is prefixed by @samp{=}.
30229 @cindex console output in @sc{gdb/mi}
30230 @var{console-stream-output} is output that should be displayed as is in the
30231 console. It is the textual response to a CLI command. All the console
30232 output is prefixed by @samp{~}.
30235 @cindex target output in @sc{gdb/mi}
30236 @var{target-stream-output} is the output produced by the target program.
30237 All the target output is prefixed by @samp{@@}.
30240 @cindex log output in @sc{gdb/mi}
30241 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
30242 instance messages that should be displayed as part of an error log. All
30243 the log output is prefixed by @samp{&}.
30246 @cindex list output in @sc{gdb/mi}
30247 New @sc{gdb/mi} commands should only output @var{lists} containing
30253 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
30254 details about the various output records.
30256 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30257 @node GDB/MI Compatibility with CLI
30258 @section @sc{gdb/mi} Compatibility with CLI
30260 @cindex compatibility, @sc{gdb/mi} and CLI
30261 @cindex @sc{gdb/mi}, compatibility with CLI
30263 For the developers convenience CLI commands can be entered directly,
30264 but there may be some unexpected behaviour. For example, commands
30265 that query the user will behave as if the user replied yes, breakpoint
30266 command lists are not executed and some CLI commands, such as
30267 @code{if}, @code{when} and @code{define}, prompt for further input with
30268 @samp{>}, which is not valid MI output.
30270 This feature may be removed at some stage in the future and it is
30271 recommended that front ends use the @code{-interpreter-exec} command
30272 (@pxref{-interpreter-exec}).
30274 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30275 @node GDB/MI Development and Front Ends
30276 @section @sc{gdb/mi} Development and Front Ends
30277 @cindex @sc{gdb/mi} development
30279 The application which takes the MI output and presents the state of the
30280 program being debugged to the user is called a @dfn{front end}.
30282 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
30283 to the MI interface may break existing usage. This section describes how the
30284 protocol changes and how to request previous version of the protocol when it
30287 Some changes in MI need not break a carefully designed front end, and
30288 for these the MI version will remain unchanged. The following is a
30289 list of changes that may occur within one level, so front ends should
30290 parse MI output in a way that can handle them:
30294 New MI commands may be added.
30297 New fields may be added to the output of any MI command.
30300 The range of values for fields with specified values, e.g.,
30301 @code{in_scope} (@pxref{-var-update}) may be extended.
30303 @c The format of field's content e.g type prefix, may change so parse it
30304 @c at your own risk. Yes, in general?
30306 @c The order of fields may change? Shouldn't really matter but it might
30307 @c resolve inconsistencies.
30310 If the changes are likely to break front ends, the MI version level
30311 will be increased by one. The new versions of the MI protocol are not compatible
30312 with the old versions. Old versions of MI remain available, allowing front ends
30313 to keep using them until they are modified to use the latest MI version.
30315 Since @code{--interpreter=mi} always points to the latest MI version, it is
30316 recommended that front ends request a specific version of MI when launching
30317 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
30318 interpreter with the MI version they expect.
30320 The following table gives a summary of the released versions of the MI
30321 interface: the version number, the version of GDB in which it first appeared
30322 and the breaking changes compared to the previous version.
30324 @multitable @columnfractions .1 .1 .8
30325 @headitem MI version @tab GDB version @tab Breaking changes
30342 The @code{-environment-pwd}, @code{-environment-directory} and
30343 @code{-environment-path} commands now returns values using the MI output
30344 syntax, rather than CLI output syntax.
30347 @code{-var-list-children}'s @code{children} result field is now a list, rather
30351 @code{-var-update}'s @code{changelist} result field is now a list, rather than
30363 The output of information about multi-location breakpoints has changed in the
30364 responses to the @code{-break-insert} and @code{-break-info} commands, as well
30365 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
30366 The multiple locations are now placed in a @code{locations} field, whose value
30372 If your front end cannot yet migrate to a more recent version of the
30373 MI protocol, you can nevertheless selectively enable specific features
30374 available in those recent MI versions, using the following commands:
30378 @item -fix-multi-location-breakpoint-output
30379 Use the output for multi-location breakpoints which was introduced by
30380 MI 3, even when using MI versions 2 or 1. This command has no
30381 effect when using MI version 3 or later.
30385 The best way to avoid unexpected changes in MI that might break your front
30386 end is to make your project known to @value{GDBN} developers and
30387 follow development on @email{gdb@@sourceware.org} and
30388 @email{gdb-patches@@sourceware.org}.
30389 @cindex mailing lists
30391 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30392 @node GDB/MI Output Records
30393 @section @sc{gdb/mi} Output Records
30396 * GDB/MI Result Records::
30397 * GDB/MI Stream Records::
30398 * GDB/MI Async Records::
30399 * GDB/MI Breakpoint Information::
30400 * GDB/MI Frame Information::
30401 * GDB/MI Thread Information::
30402 * GDB/MI Ada Exception Information::
30405 @node GDB/MI Result Records
30406 @subsection @sc{gdb/mi} Result Records
30408 @cindex result records in @sc{gdb/mi}
30409 @cindex @sc{gdb/mi}, result records
30410 In addition to a number of out-of-band notifications, the response to a
30411 @sc{gdb/mi} command includes one of the following result indications:
30415 @item "^done" [ "," @var{results} ]
30416 The synchronous operation was successful, @code{@var{results}} are the return
30421 This result record is equivalent to @samp{^done}. Historically, it
30422 was output instead of @samp{^done} if the command has resumed the
30423 target. This behaviour is maintained for backward compatibility, but
30424 all frontends should treat @samp{^done} and @samp{^running}
30425 identically and rely on the @samp{*running} output record to determine
30426 which threads are resumed.
30430 @value{GDBN} has connected to a remote target.
30432 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30434 The operation failed. The @code{msg=@var{c-string}} variable contains
30435 the corresponding error message.
30437 If present, the @code{code=@var{c-string}} variable provides an error
30438 code on which consumers can rely on to detect the corresponding
30439 error condition. At present, only one error code is defined:
30442 @item "undefined-command"
30443 Indicates that the command causing the error does not exist.
30448 @value{GDBN} has terminated.
30452 @node GDB/MI Stream Records
30453 @subsection @sc{gdb/mi} Stream Records
30455 @cindex @sc{gdb/mi}, stream records
30456 @cindex stream records in @sc{gdb/mi}
30457 @value{GDBN} internally maintains a number of output streams: the console, the
30458 target, and the log. The output intended for each of these streams is
30459 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30461 Each stream record begins with a unique @dfn{prefix character} which
30462 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30463 Syntax}). In addition to the prefix, each stream record contains a
30464 @code{@var{string-output}}. This is either raw text (with an implicit new
30465 line) or a quoted C string (which does not contain an implicit newline).
30468 @item "~" @var{string-output}
30469 The console output stream contains text that should be displayed in the
30470 CLI console window. It contains the textual responses to CLI commands.
30472 @item "@@" @var{string-output}
30473 The target output stream contains any textual output from the running
30474 target. This is only present when GDB's event loop is truly
30475 asynchronous, which is currently only the case for remote targets.
30477 @item "&" @var{string-output}
30478 The log stream contains debugging messages being produced by @value{GDBN}'s
30482 @node GDB/MI Async Records
30483 @subsection @sc{gdb/mi} Async Records
30485 @cindex async records in @sc{gdb/mi}
30486 @cindex @sc{gdb/mi}, async records
30487 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30488 additional changes that have occurred. Those changes can either be a
30489 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30490 target activity (e.g., target stopped).
30492 The following is the list of possible async records:
30496 @item *running,thread-id="@var{thread}"
30497 The target is now running. The @var{thread} field can be the global
30498 thread ID of the thread that is now running, and it can be
30499 @samp{all} if all threads are running. The frontend should assume
30500 that no interaction with a running thread is possible after this
30501 notification is produced. The frontend should not assume that this
30502 notification is output only once for any command. @value{GDBN} may
30503 emit this notification several times, either for different threads,
30504 because it cannot resume all threads together, or even for a single
30505 thread, if the thread must be stepped though some code before letting
30508 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30509 The target has stopped. The @var{reason} field can have one of the
30513 @item breakpoint-hit
30514 A breakpoint was reached.
30515 @item watchpoint-trigger
30516 A watchpoint was triggered.
30517 @item read-watchpoint-trigger
30518 A read watchpoint was triggered.
30519 @item access-watchpoint-trigger
30520 An access watchpoint was triggered.
30521 @item function-finished
30522 An -exec-finish or similar CLI command was accomplished.
30523 @item location-reached
30524 An -exec-until or similar CLI command was accomplished.
30525 @item watchpoint-scope
30526 A watchpoint has gone out of scope.
30527 @item end-stepping-range
30528 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30529 similar CLI command was accomplished.
30530 @item exited-signalled
30531 The inferior exited because of a signal.
30533 The inferior exited.
30534 @item exited-normally
30535 The inferior exited normally.
30536 @item signal-received
30537 A signal was received by the inferior.
30539 The inferior has stopped due to a library being loaded or unloaded.
30540 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30541 set or when a @code{catch load} or @code{catch unload} catchpoint is
30542 in use (@pxref{Set Catchpoints}).
30544 The inferior has forked. This is reported when @code{catch fork}
30545 (@pxref{Set Catchpoints}) has been used.
30547 The inferior has vforked. This is reported in when @code{catch vfork}
30548 (@pxref{Set Catchpoints}) has been used.
30549 @item syscall-entry
30550 The inferior entered a system call. This is reported when @code{catch
30551 syscall} (@pxref{Set Catchpoints}) has been used.
30552 @item syscall-return
30553 The inferior returned from a system call. This is reported when
30554 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30556 The inferior called @code{exec}. This is reported when @code{catch exec}
30557 (@pxref{Set Catchpoints}) has been used.
30560 The @var{id} field identifies the global thread ID of the thread
30561 that directly caused the stop -- for example by hitting a breakpoint.
30562 Depending on whether all-stop
30563 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30564 stop all threads, or only the thread that directly triggered the stop.
30565 If all threads are stopped, the @var{stopped} field will have the
30566 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30567 field will be a list of thread identifiers. Presently, this list will
30568 always include a single thread, but frontend should be prepared to see
30569 several threads in the list. The @var{core} field reports the
30570 processor core on which the stop event has happened. This field may be absent
30571 if such information is not available.
30573 @item =thread-group-added,id="@var{id}"
30574 @itemx =thread-group-removed,id="@var{id}"
30575 A thread group was either added or removed. The @var{id} field
30576 contains the @value{GDBN} identifier of the thread group. When a thread
30577 group is added, it generally might not be associated with a running
30578 process. When a thread group is removed, its id becomes invalid and
30579 cannot be used in any way.
30581 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30582 A thread group became associated with a running program,
30583 either because the program was just started or the thread group
30584 was attached to a program. The @var{id} field contains the
30585 @value{GDBN} identifier of the thread group. The @var{pid} field
30586 contains process identifier, specific to the operating system.
30588 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30589 A thread group is no longer associated with a running program,
30590 either because the program has exited, or because it was detached
30591 from. The @var{id} field contains the @value{GDBN} identifier of the
30592 thread group. The @var{code} field is the exit code of the inferior; it exists
30593 only when the inferior exited with some code.
30595 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30596 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30597 A thread either was created, or has exited. The @var{id} field
30598 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30599 field identifies the thread group this thread belongs to.
30601 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30602 Informs that the selected thread or frame were changed. This notification
30603 is not emitted as result of the @code{-thread-select} or
30604 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30605 that is not documented to change the selected thread and frame actually
30606 changes them. In particular, invoking, directly or indirectly
30607 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30608 will generate this notification. Changing the thread or frame from another
30609 user interface (see @ref{Interpreters}) will also generate this notification.
30611 The @var{frame} field is only present if the newly selected thread is
30612 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30614 We suggest that in response to this notification, front ends
30615 highlight the selected thread and cause subsequent commands to apply to
30618 @item =library-loaded,...
30619 Reports that a new library file was loaded by the program. This
30620 notification has 5 fields---@var{id}, @var{target-name},
30621 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30622 opaque identifier of the library. For remote debugging case,
30623 @var{target-name} and @var{host-name} fields give the name of the
30624 library file on the target, and on the host respectively. For native
30625 debugging, both those fields have the same value. The
30626 @var{symbols-loaded} field is emitted only for backward compatibility
30627 and should not be relied on to convey any useful information. The
30628 @var{thread-group} field, if present, specifies the id of the thread
30629 group in whose context the library was loaded. If the field is
30630 absent, it means the library was loaded in the context of all present
30631 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30634 @item =library-unloaded,...
30635 Reports that a library was unloaded by the program. This notification
30636 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30637 the same meaning as for the @code{=library-loaded} notification.
30638 The @var{thread-group} field, if present, specifies the id of the
30639 thread group in whose context the library was unloaded. If the field is
30640 absent, it means the library was unloaded in the context of all present
30643 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30644 @itemx =traceframe-changed,end
30645 Reports that the trace frame was changed and its new number is
30646 @var{tfnum}. The number of the tracepoint associated with this trace
30647 frame is @var{tpnum}.
30649 @item =tsv-created,name=@var{name},initial=@var{initial}
30650 Reports that the new trace state variable @var{name} is created with
30651 initial value @var{initial}.
30653 @item =tsv-deleted,name=@var{name}
30654 @itemx =tsv-deleted
30655 Reports that the trace state variable @var{name} is deleted or all
30656 trace state variables are deleted.
30658 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30659 Reports that the trace state variable @var{name} is modified with
30660 the initial value @var{initial}. The current value @var{current} of
30661 trace state variable is optional and is reported if the current
30662 value of trace state variable is known.
30664 @item =breakpoint-created,bkpt=@{...@}
30665 @itemx =breakpoint-modified,bkpt=@{...@}
30666 @itemx =breakpoint-deleted,id=@var{number}
30667 Reports that a breakpoint was created, modified, or deleted,
30668 respectively. Only user-visible breakpoints are reported to the MI
30671 The @var{bkpt} argument is of the same form as returned by the various
30672 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30673 @var{number} is the ordinal number of the breakpoint.
30675 Note that if a breakpoint is emitted in the result record of a
30676 command, then it will not also be emitted in an async record.
30678 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30679 @itemx =record-stopped,thread-group="@var{id}"
30680 Execution log recording was either started or stopped on an
30681 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30682 group corresponding to the affected inferior.
30684 The @var{method} field indicates the method used to record execution. If the
30685 method in use supports multiple recording formats, @var{format} will be present
30686 and contain the currently used format. @xref{Process Record and Replay},
30687 for existing method and format values.
30689 @item =cmd-param-changed,param=@var{param},value=@var{value}
30690 Reports that a parameter of the command @code{set @var{param}} is
30691 changed to @var{value}. In the multi-word @code{set} command,
30692 the @var{param} is the whole parameter list to @code{set} command.
30693 For example, In command @code{set check type on}, @var{param}
30694 is @code{check type} and @var{value} is @code{on}.
30696 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30697 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30698 written in an inferior. The @var{id} is the identifier of the
30699 thread group corresponding to the affected inferior. The optional
30700 @code{type="code"} part is reported if the memory written to holds
30704 @node GDB/MI Breakpoint Information
30705 @subsection @sc{gdb/mi} Breakpoint Information
30707 When @value{GDBN} reports information about a breakpoint, a
30708 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30713 The breakpoint number.
30716 The type of the breakpoint. For ordinary breakpoints this will be
30717 @samp{breakpoint}, but many values are possible.
30720 If the type of the breakpoint is @samp{catchpoint}, then this
30721 indicates the exact type of catchpoint.
30724 This is the breakpoint disposition---either @samp{del}, meaning that
30725 the breakpoint will be deleted at the next stop, or @samp{keep},
30726 meaning that the breakpoint will not be deleted.
30729 This indicates whether the breakpoint is enabled, in which case the
30730 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30731 Note that this is not the same as the field @code{enable}.
30734 The address of the breakpoint. This may be a hexidecimal number,
30735 giving the address; or the string @samp{<PENDING>}, for a pending
30736 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30737 multiple locations. This field will not be present if no address can
30738 be determined. For example, a watchpoint does not have an address.
30741 Optional field containing any flags related to the address. These flags are
30742 architecture-dependent; see @ref{Architectures} for their meaning for a
30746 If known, the function in which the breakpoint appears.
30747 If not known, this field is not present.
30750 The name of the source file which contains this function, if known.
30751 If not known, this field is not present.
30754 The full file name of the source file which contains this function, if
30755 known. If not known, this field is not present.
30758 The line number at which this breakpoint appears, if known.
30759 If not known, this field is not present.
30762 If the source file is not known, this field may be provided. If
30763 provided, this holds the address of the breakpoint, possibly followed
30767 If this breakpoint is pending, this field is present and holds the
30768 text used to set the breakpoint, as entered by the user.
30771 Where this breakpoint's condition is evaluated, either @samp{host} or
30775 If this is a thread-specific breakpoint, then this identifies the
30776 thread in which the breakpoint can trigger.
30779 If this breakpoint is restricted to a particular Ada task, then this
30780 field will hold the task identifier.
30783 If the breakpoint is conditional, this is the condition expression.
30786 The ignore count of the breakpoint.
30789 The enable count of the breakpoint.
30791 @item traceframe-usage
30794 @item static-tracepoint-marker-string-id
30795 For a static tracepoint, the name of the static tracepoint marker.
30798 For a masked watchpoint, this is the mask.
30801 A tracepoint's pass count.
30803 @item original-location
30804 The location of the breakpoint as originally specified by the user.
30805 This field is optional.
30808 The number of times the breakpoint has been hit.
30811 This field is only given for tracepoints. This is either @samp{y},
30812 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30816 Some extra data, the exact contents of which are type-dependent.
30819 This field is present if the breakpoint has multiple locations. It is also
30820 exceptionally present if the breakpoint is enabled and has a single, disabled
30823 The value is a list of locations. The format of a location is described below.
30827 A location in a multi-location breakpoint is represented as a tuple with the
30833 The location number as a dotted pair, like @samp{1.2}. The first digit is the
30834 number of the parent breakpoint. The second digit is the number of the
30835 location within that breakpoint.
30838 There are three possible values, with the following meanings:
30841 The location is enabled.
30843 The location is disabled by the user.
30845 The location is disabled because the breakpoint condition is invalid
30850 The address of this location as an hexidecimal number.
30853 Optional field containing any flags related to the address. These flags are
30854 architecture-dependent; see @ref{Architectures} for their meaning for a
30858 If known, the function in which the location appears.
30859 If not known, this field is not present.
30862 The name of the source file which contains this location, if known.
30863 If not known, this field is not present.
30866 The full file name of the source file which contains this location, if
30867 known. If not known, this field is not present.
30870 The line number at which this location appears, if known.
30871 If not known, this field is not present.
30873 @item thread-groups
30874 The thread groups this location is in.
30878 For example, here is what the output of @code{-break-insert}
30879 (@pxref{GDB/MI Breakpoint Commands}) might be:
30882 -> -break-insert main
30883 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30884 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30885 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30890 @node GDB/MI Frame Information
30891 @subsection @sc{gdb/mi} Frame Information
30893 Response from many MI commands includes an information about stack
30894 frame. This information is a tuple that may have the following
30899 The level of the stack frame. The innermost frame has the level of
30900 zero. This field is always present.
30903 The name of the function corresponding to the frame. This field may
30904 be absent if @value{GDBN} is unable to determine the function name.
30907 The code address for the frame. This field is always present.
30910 Optional field containing any flags related to the address. These flags are
30911 architecture-dependent; see @ref{Architectures} for their meaning for a
30915 The name of the source files that correspond to the frame's code
30916 address. This field may be absent.
30919 The source line corresponding to the frames' code address. This field
30923 The name of the binary file (either executable or shared library) the
30924 corresponds to the frame's code address. This field may be absent.
30928 @node GDB/MI Thread Information
30929 @subsection @sc{gdb/mi} Thread Information
30931 Whenever @value{GDBN} has to report an information about a thread, it
30932 uses a tuple with the following fields. The fields are always present unless
30937 The global numeric id assigned to the thread by @value{GDBN}.
30940 The target-specific string identifying the thread.
30943 Additional information about the thread provided by the target.
30944 It is supposed to be human-readable and not interpreted by the
30945 frontend. This field is optional.
30948 The name of the thread. If the user specified a name using the
30949 @code{thread name} command, then this name is given. Otherwise, if
30950 @value{GDBN} can extract the thread name from the target, then that
30951 name is given. If @value{GDBN} cannot find the thread name, then this
30955 The execution state of the thread, either @samp{stopped} or @samp{running},
30956 depending on whether the thread is presently running.
30959 The stack frame currently executing in the thread. This field is only present
30960 if the thread is stopped. Its format is documented in
30961 @ref{GDB/MI Frame Information}.
30964 The value of this field is an integer number of the processor core the
30965 thread was last seen on. This field is optional.
30968 @node GDB/MI Ada Exception Information
30969 @subsection @sc{gdb/mi} Ada Exception Information
30971 Whenever a @code{*stopped} record is emitted because the program
30972 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
30973 @value{GDBN} provides the name of the exception that was raised via
30974 the @code{exception-name} field. Also, for exceptions that were raised
30975 with an exception message, @value{GDBN} provides that message via
30976 the @code{exception-message} field.
30978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30979 @node GDB/MI Simple Examples
30980 @section Simple Examples of @sc{gdb/mi} Interaction
30981 @cindex @sc{gdb/mi}, simple examples
30983 This subsection presents several simple examples of interaction using
30984 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
30985 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
30986 the output received from @sc{gdb/mi}.
30988 Note the line breaks shown in the examples are here only for
30989 readability, they don't appear in the real output.
30991 @subheading Setting a Breakpoint
30993 Setting a breakpoint generates synchronous output which contains detailed
30994 information of the breakpoint.
30997 -> -break-insert main
30998 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30999 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31000 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31005 @subheading Program Execution
31007 Program execution generates asynchronous records and MI gives the
31008 reason that execution stopped.
31014 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31015 frame=@{addr="0x08048564",func="main",
31016 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
31017 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
31018 arch="i386:x86_64"@}
31023 <- *stopped,reason="exited-normally"
31027 @subheading Quitting @value{GDBN}
31029 Quitting @value{GDBN} just prints the result class @samp{^exit}.
31037 Please note that @samp{^exit} is printed immediately, but it might
31038 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
31039 performs necessary cleanups, including killing programs being debugged
31040 or disconnecting from debug hardware, so the frontend should wait till
31041 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
31042 fails to exit in reasonable time.
31044 @subheading A Bad Command
31046 Here's what happens if you pass a non-existent command:
31050 <- ^error,msg="Undefined MI command: rubbish"
31055 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31056 @node GDB/MI Command Description Format
31057 @section @sc{gdb/mi} Command Description Format
31059 The remaining sections describe blocks of commands. Each block of
31060 commands is laid out in a fashion similar to this section.
31062 @subheading Motivation
31064 The motivation for this collection of commands.
31066 @subheading Introduction
31068 A brief introduction to this collection of commands as a whole.
31070 @subheading Commands
31072 For each command in the block, the following is described:
31074 @subsubheading Synopsis
31077 -command @var{args}@dots{}
31080 @subsubheading Result
31082 @subsubheading @value{GDBN} Command
31084 The corresponding @value{GDBN} CLI command(s), if any.
31086 @subsubheading Example
31088 Example(s) formatted for readability. Some of the described commands have
31089 not been implemented yet and these are labeled N.A.@: (not available).
31092 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31093 @node GDB/MI Breakpoint Commands
31094 @section @sc{gdb/mi} Breakpoint Commands
31096 @cindex breakpoint commands for @sc{gdb/mi}
31097 @cindex @sc{gdb/mi}, breakpoint commands
31098 This section documents @sc{gdb/mi} commands for manipulating
31101 @subheading The @code{-break-after} Command
31102 @findex -break-after
31104 @subsubheading Synopsis
31107 -break-after @var{number} @var{count}
31110 The breakpoint number @var{number} is not in effect until it has been
31111 hit @var{count} times. To see how this is reflected in the output of
31112 the @samp{-break-list} command, see the description of the
31113 @samp{-break-list} command below.
31115 @subsubheading @value{GDBN} Command
31117 The corresponding @value{GDBN} command is @samp{ignore}.
31119 @subsubheading Example
31124 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31125 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31126 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31134 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31135 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31136 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31137 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31138 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31139 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31140 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31141 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31142 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31143 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
31148 @subheading The @code{-break-catch} Command
31149 @findex -break-catch
31152 @subheading The @code{-break-commands} Command
31153 @findex -break-commands
31155 @subsubheading Synopsis
31158 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
31161 Specifies the CLI commands that should be executed when breakpoint
31162 @var{number} is hit. The parameters @var{command1} to @var{commandN}
31163 are the commands. If no command is specified, any previously-set
31164 commands are cleared. @xref{Break Commands}. Typical use of this
31165 functionality is tracing a program, that is, printing of values of
31166 some variables whenever breakpoint is hit and then continuing.
31168 @subsubheading @value{GDBN} Command
31170 The corresponding @value{GDBN} command is @samp{commands}.
31172 @subsubheading Example
31177 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31178 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31179 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31182 -break-commands 1 "print v" "continue"
31187 @subheading The @code{-break-condition} Command
31188 @findex -break-condition
31190 @subsubheading Synopsis
31193 -break-condition [ --force ] @var{number} [ @var{expr} ]
31196 Breakpoint @var{number} will stop the program only if the condition in
31197 @var{expr} is true. The condition becomes part of the
31198 @samp{-break-list} output (see the description of the @samp{-break-list}
31199 command below). If the @samp{--force} flag is passed, the condition
31200 is forcibly defined even when it is invalid for all locations of
31201 breakpoint @var{number}. If the @var{expr} argument is omitted,
31202 breakpoint @var{number} becomes unconditional.
31204 @subsubheading @value{GDBN} Command
31206 The corresponding @value{GDBN} command is @samp{condition}.
31208 @subsubheading Example
31212 -break-condition 1 1
31216 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31217 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31218 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31219 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31220 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31221 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31222 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31223 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31224 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31225 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
31229 @subheading The @code{-break-delete} Command
31230 @findex -break-delete
31232 @subsubheading Synopsis
31235 -break-delete ( @var{breakpoint} )+
31238 Delete the breakpoint(s) whose number(s) are specified in the argument
31239 list. This is obviously reflected in the breakpoint list.
31241 @subsubheading @value{GDBN} Command
31243 The corresponding @value{GDBN} command is @samp{delete}.
31245 @subsubheading Example
31253 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31254 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31255 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31256 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31257 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31258 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31259 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31264 @subheading The @code{-break-disable} Command
31265 @findex -break-disable
31267 @subsubheading Synopsis
31270 -break-disable ( @var{breakpoint} )+
31273 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
31274 break list is now set to @samp{n} for the named @var{breakpoint}(s).
31276 @subsubheading @value{GDBN} Command
31278 The corresponding @value{GDBN} command is @samp{disable}.
31280 @subsubheading Example
31288 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31289 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31290 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31291 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31292 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31293 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31294 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31295 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
31296 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31297 line="5",thread-groups=["i1"],times="0"@}]@}
31301 @subheading The @code{-break-enable} Command
31302 @findex -break-enable
31304 @subsubheading Synopsis
31307 -break-enable ( @var{breakpoint} )+
31310 Enable (previously disabled) @var{breakpoint}(s).
31312 @subsubheading @value{GDBN} Command
31314 The corresponding @value{GDBN} command is @samp{enable}.
31316 @subsubheading Example
31324 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31325 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31326 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31327 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31328 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31329 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31330 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31331 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31332 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31333 line="5",thread-groups=["i1"],times="0"@}]@}
31337 @subheading The @code{-break-info} Command
31338 @findex -break-info
31340 @subsubheading Synopsis
31343 -break-info @var{breakpoint}
31347 Get information about a single breakpoint.
31349 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
31350 Information}, for details on the format of each breakpoint in the
31353 @subsubheading @value{GDBN} Command
31355 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
31357 @subsubheading Example
31360 @subheading The @code{-break-insert} Command
31361 @findex -break-insert
31362 @anchor{-break-insert}
31364 @subsubheading Synopsis
31367 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
31368 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
31369 [ -p @var{thread-id} ] [ @var{locspec} ]
31373 If specified, @var{locspec}, can be one of:
31376 @item linespec location
31377 A linespec location. @xref{Linespec Locations}.
31379 @item explicit location
31380 An explicit location. @sc{gdb/mi} explicit locations are
31381 analogous to the CLI's explicit locations using the option names
31382 listed below. @xref{Explicit Locations}.
31385 @item --source @var{filename}
31386 The source file name of the location. This option requires the use
31387 of either @samp{--function} or @samp{--line}.
31389 @item --function @var{function}
31390 The name of a function or method.
31392 @item --label @var{label}
31393 The name of a label.
31395 @item --line @var{lineoffset}
31396 An absolute or relative line offset from the start of the location.
31399 @item address location
31400 An address location, *@var{address}. @xref{Address Locations}.
31404 The possible optional parameters of this command are:
31408 Insert a temporary breakpoint.
31410 Insert a hardware breakpoint.
31412 If @var{locspec} cannot be resolved (for example if it
31413 refers to unknown files or functions), create a pending
31414 breakpoint. Without this flag, @value{GDBN} will report
31415 an error, and won't create a breakpoint, if @var{locspec}
31418 Create a disabled breakpoint.
31420 Create a tracepoint. @xref{Tracepoints}. When this parameter
31421 is used together with @samp{-h}, a fast tracepoint is created.
31422 @item -c @var{condition}
31423 Make the breakpoint conditional on @var{condition}.
31424 @item --force-condition
31425 Forcibly define the breakpoint even if the condition is invalid at
31426 all of the breakpoint locations.
31427 @item -i @var{ignore-count}
31428 Initialize the @var{ignore-count}.
31429 @item -p @var{thread-id}
31430 Restrict the breakpoint to the thread with the specified global
31433 This option makes @value{GDBN} interpret a function name specified as
31434 a complete fully-qualified name.
31437 @subsubheading Result
31439 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31440 resulting breakpoint.
31442 Note: this format is open to change.
31443 @c An out-of-band breakpoint instead of part of the result?
31445 @subsubheading @value{GDBN} Command
31447 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31448 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31450 @subsubheading Example
31455 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31456 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31459 -break-insert -t foo
31460 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31461 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31465 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31466 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31467 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31468 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31469 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31470 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31471 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31472 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31473 addr="0x0001072c", func="main",file="recursive2.c",
31474 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31476 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31477 addr="0x00010774",func="foo",file="recursive2.c",
31478 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31483 @subheading The @code{-dprintf-insert} Command
31484 @findex -dprintf-insert
31486 @subsubheading Synopsis
31489 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31490 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31491 [ -p @var{thread-id} ] [ @var{locspec} ] [ @var{format} ]
31496 If supplied, @var{locspec} and @code{--qualified} may be specified
31497 the same way as for the @code{-break-insert} command.
31498 @xref{-break-insert}.
31500 The possible optional parameters of this command are:
31504 Insert a temporary breakpoint.
31506 If @var{locspec} cannot be parsed (for example, if it
31507 refers to unknown files or functions), create a pending
31508 breakpoint. Without this flag, @value{GDBN} will report
31509 an error, and won't create a breakpoint, if @var{locspec}
31512 Create a disabled breakpoint.
31513 @item -c @var{condition}
31514 Make the breakpoint conditional on @var{condition}.
31515 @item --force-condition
31516 Forcibly define the breakpoint even if the condition is invalid at
31517 all of the breakpoint locations.
31518 @item -i @var{ignore-count}
31519 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31520 to @var{ignore-count}.
31521 @item -p @var{thread-id}
31522 Restrict the breakpoint to the thread with the specified global
31526 @subsubheading Result
31528 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31529 resulting breakpoint.
31531 @c An out-of-band breakpoint instead of part of the result?
31533 @subsubheading @value{GDBN} Command
31535 The corresponding @value{GDBN} command is @samp{dprintf}.
31537 @subsubheading Example
31541 4-dprintf-insert foo "At foo entry\n"
31542 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31543 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31544 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31545 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
31546 original-location="foo"@}
31548 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31549 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31550 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31551 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31552 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
31553 original-location="mi-dprintf.c:26"@}
31557 @subheading The @code{-break-list} Command
31558 @findex -break-list
31560 @subsubheading Synopsis
31566 Displays the list of inserted breakpoints, showing the following fields:
31570 number of the breakpoint
31572 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31574 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31577 is the breakpoint enabled or no: @samp{y} or @samp{n}
31579 memory location at which the breakpoint is set
31581 logical location of the breakpoint, expressed by function name, file
31583 @item Thread-groups
31584 list of thread groups to which this breakpoint applies
31586 number of times the breakpoint has been hit
31589 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31590 @code{body} field is an empty list.
31592 @subsubheading @value{GDBN} Command
31594 The corresponding @value{GDBN} command is @samp{info break}.
31596 @subsubheading Example
31601 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31602 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31603 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31604 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31605 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31606 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31607 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31608 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31609 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31611 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31612 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31613 line="13",thread-groups=["i1"],times="0"@}]@}
31617 Here's an example of the result when there are no breakpoints:
31622 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31623 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31624 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31625 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31626 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31627 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31628 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31633 @subheading The @code{-break-passcount} Command
31634 @findex -break-passcount
31636 @subsubheading Synopsis
31639 -break-passcount @var{tracepoint-number} @var{passcount}
31642 Set the passcount for tracepoint @var{tracepoint-number} to
31643 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31644 is not a tracepoint, error is emitted. This corresponds to CLI
31645 command @samp{passcount}.
31647 @subheading The @code{-break-watch} Command
31648 @findex -break-watch
31650 @subsubheading Synopsis
31653 -break-watch [ -a | -r ]
31656 Create a watchpoint. With the @samp{-a} option it will create an
31657 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31658 read from or on a write to the memory location. With the @samp{-r}
31659 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31660 trigger only when the memory location is accessed for reading. Without
31661 either of the options, the watchpoint created is a regular watchpoint,
31662 i.e., it will trigger when the memory location is accessed for writing.
31663 @xref{Set Watchpoints, , Setting Watchpoints}.
31665 Note that @samp{-break-list} will report a single list of watchpoints and
31666 breakpoints inserted.
31668 @subsubheading @value{GDBN} Command
31670 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31673 @subsubheading Example
31675 Setting a watchpoint on a variable in the @code{main} function:
31680 ^done,wpt=@{number="2",exp="x"@}
31685 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31686 value=@{old="-268439212",new="55"@},
31687 frame=@{func="main",args=[],file="recursive2.c",
31688 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31692 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31693 the program execution twice: first for the variable changing value, then
31694 for the watchpoint going out of scope.
31699 ^done,wpt=@{number="5",exp="C"@}
31704 *stopped,reason="watchpoint-trigger",
31705 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31706 frame=@{func="callee4",args=[],
31707 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31708 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31709 arch="i386:x86_64"@}
31714 *stopped,reason="watchpoint-scope",wpnum="5",
31715 frame=@{func="callee3",args=[@{name="strarg",
31716 value="0x11940 \"A string argument.\""@}],
31717 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31718 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31719 arch="i386:x86_64"@}
31723 Listing breakpoints and watchpoints, at different points in the program
31724 execution. Note that once the watchpoint goes out of scope, it is
31730 ^done,wpt=@{number="2",exp="C"@}
31733 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31740 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31741 addr="0x00010734",func="callee4",
31742 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31743 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31745 bkpt=@{number="2",type="watchpoint",disp="keep",
31746 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31751 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31752 value=@{old="-276895068",new="3"@},
31753 frame=@{func="callee4",args=[],
31754 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31755 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31756 arch="i386:x86_64"@}
31759 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31760 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31761 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31762 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31763 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31764 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31765 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31766 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31767 addr="0x00010734",func="callee4",
31768 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31769 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31771 bkpt=@{number="2",type="watchpoint",disp="keep",
31772 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31776 ^done,reason="watchpoint-scope",wpnum="2",
31777 frame=@{func="callee3",args=[@{name="strarg",
31778 value="0x11940 \"A string argument.\""@}],
31779 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31780 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31781 arch="i386:x86_64"@}
31784 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31785 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31786 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31787 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31788 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31789 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31790 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31791 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31792 addr="0x00010734",func="callee4",
31793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31794 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31795 thread-groups=["i1"],times="1"@}]@}
31800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31801 @node GDB/MI Catchpoint Commands
31802 @section @sc{gdb/mi} Catchpoint Commands
31804 This section documents @sc{gdb/mi} commands for manipulating
31808 * Shared Library GDB/MI Catchpoint Commands::
31809 * Ada Exception GDB/MI Catchpoint Commands::
31810 * C++ Exception GDB/MI Catchpoint Commands::
31813 @node Shared Library GDB/MI Catchpoint Commands
31814 @subsection Shared Library @sc{gdb/mi} Catchpoints
31816 @subheading The @code{-catch-load} Command
31817 @findex -catch-load
31819 @subsubheading Synopsis
31822 -catch-load [ -t ] [ -d ] @var{regexp}
31825 Add a catchpoint for library load events. If the @samp{-t} option is used,
31826 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31827 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
31828 in a disabled state. The @samp{regexp} argument is a regular
31829 expression used to match the name of the loaded library.
31832 @subsubheading @value{GDBN} Command
31834 The corresponding @value{GDBN} command is @samp{catch load}.
31836 @subsubheading Example
31839 -catch-load -t foo.so
31840 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
31841 what="load of library matching foo.so",catch-type="load",times="0"@}
31846 @subheading The @code{-catch-unload} Command
31847 @findex -catch-unload
31849 @subsubheading Synopsis
31852 -catch-unload [ -t ] [ -d ] @var{regexp}
31855 Add a catchpoint for library unload events. If the @samp{-t} option is
31856 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31857 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
31858 created in a disabled state. The @samp{regexp} argument is a regular
31859 expression used to match the name of the unloaded library.
31861 @subsubheading @value{GDBN} Command
31863 The corresponding @value{GDBN} command is @samp{catch unload}.
31865 @subsubheading Example
31868 -catch-unload -d bar.so
31869 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
31870 what="load of library matching bar.so",catch-type="unload",times="0"@}
31874 @node Ada Exception GDB/MI Catchpoint Commands
31875 @subsection Ada Exception @sc{gdb/mi} Catchpoints
31877 The following @sc{gdb/mi} commands can be used to create catchpoints
31878 that stop the execution when Ada exceptions are being raised.
31880 @subheading The @code{-catch-assert} Command
31881 @findex -catch-assert
31883 @subsubheading Synopsis
31886 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
31889 Add a catchpoint for failed Ada assertions.
31891 The possible optional parameters for this command are:
31894 @item -c @var{condition}
31895 Make the catchpoint conditional on @var{condition}.
31897 Create a disabled catchpoint.
31899 Create a temporary catchpoint.
31902 @subsubheading @value{GDBN} Command
31904 The corresponding @value{GDBN} command is @samp{catch assert}.
31906 @subsubheading Example
31910 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
31911 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
31912 thread-groups=["i1"],times="0",
31913 original-location="__gnat_debug_raise_assert_failure"@}
31917 @subheading The @code{-catch-exception} Command
31918 @findex -catch-exception
31920 @subsubheading Synopsis
31923 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31927 Add a catchpoint stopping when Ada exceptions are raised.
31928 By default, the command stops the program when any Ada exception
31929 gets raised. But it is also possible, by using some of the
31930 optional parameters described below, to create more selective
31933 The possible optional parameters for this command are:
31936 @item -c @var{condition}
31937 Make the catchpoint conditional on @var{condition}.
31939 Create a disabled catchpoint.
31940 @item -e @var{exception-name}
31941 Only stop when @var{exception-name} is raised. This option cannot
31942 be used combined with @samp{-u}.
31944 Create a temporary catchpoint.
31946 Stop only when an unhandled exception gets raised. This option
31947 cannot be used combined with @samp{-e}.
31950 @subsubheading @value{GDBN} Command
31952 The corresponding @value{GDBN} commands are @samp{catch exception}
31953 and @samp{catch exception unhandled}.
31955 @subsubheading Example
31958 -catch-exception -e Program_Error
31959 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31960 enabled="y",addr="0x0000000000404874",
31961 what="`Program_Error' Ada exception", thread-groups=["i1"],
31962 times="0",original-location="__gnat_debug_raise_exception"@}
31966 @subheading The @code{-catch-handlers} Command
31967 @findex -catch-handlers
31969 @subsubheading Synopsis
31972 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31976 Add a catchpoint stopping when Ada exceptions are handled.
31977 By default, the command stops the program when any Ada exception
31978 gets handled. But it is also possible, by using some of the
31979 optional parameters described below, to create more selective
31982 The possible optional parameters for this command are:
31985 @item -c @var{condition}
31986 Make the catchpoint conditional on @var{condition}.
31988 Create a disabled catchpoint.
31989 @item -e @var{exception-name}
31990 Only stop when @var{exception-name} is handled.
31992 Create a temporary catchpoint.
31995 @subsubheading @value{GDBN} Command
31997 The corresponding @value{GDBN} command is @samp{catch handlers}.
31999 @subsubheading Example
32002 -catch-handlers -e Constraint_Error
32003 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32004 enabled="y",addr="0x0000000000402f68",
32005 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
32006 times="0",original-location="__gnat_begin_handler"@}
32010 @node C++ Exception GDB/MI Catchpoint Commands
32011 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
32013 The following @sc{gdb/mi} commands can be used to create catchpoints
32014 that stop the execution when C@t{++} exceptions are being throw, rethrown,
32017 @subheading The @code{-catch-throw} Command
32018 @findex -catch-throw
32020 @subsubheading Synopsis
32023 -catch-throw [ -t ] [ -r @var{regexp}]
32026 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
32027 given, then only exceptions whose type matches the regular expression
32030 If @samp{-t} is given, then the catchpoint is enabled only for one
32031 stop, the catchpoint is automatically deleted after stopping once for
32034 @subsubheading @value{GDBN} Command
32036 The corresponding @value{GDBN} commands are @samp{catch throw}
32037 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
32039 @subsubheading Example
32042 -catch-throw -r exception_type
32043 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32044 what="exception throw",catch-type="throw",
32045 thread-groups=["i1"],
32046 regexp="exception_type",times="0"@}
32052 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
32053 in __cxa_throw () from /lib64/libstdc++.so.6\n"
32054 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32055 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
32056 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32057 thread-id="1",stopped-threads="all",core="6"
32061 @subheading The @code{-catch-rethrow} Command
32062 @findex -catch-rethrow
32064 @subsubheading Synopsis
32067 -catch-rethrow [ -t ] [ -r @var{regexp}]
32070 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
32071 then only exceptions whose type matches the regular expression will be
32074 If @samp{-t} is given, then the catchpoint is enabled only for one
32075 stop, the catchpoint is automatically deleted after the first event is
32078 @subsubheading @value{GDBN} Command
32080 The corresponding @value{GDBN} commands are @samp{catch rethrow}
32081 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
32083 @subsubheading Example
32086 -catch-rethrow -r exception_type
32087 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32088 what="exception rethrow",catch-type="rethrow",
32089 thread-groups=["i1"],
32090 regexp="exception_type",times="0"@}
32096 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
32097 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
32098 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32099 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
32100 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32101 thread-id="1",stopped-threads="all",core="6"
32105 @subheading The @code{-catch-catch} Command
32106 @findex -catch-catch
32108 @subsubheading Synopsis
32111 -catch-catch [ -t ] [ -r @var{regexp}]
32114 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
32115 is given, then only exceptions whose type matches the regular
32116 expression will be caught.
32118 If @samp{-t} is given, then the catchpoint is enabled only for one
32119 stop, the catchpoint is automatically deleted after the first event is
32122 @subsubheading @value{GDBN} Command
32124 The corresponding @value{GDBN} commands are @samp{catch catch}
32125 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
32127 @subsubheading Example
32130 -catch-catch -r exception_type
32131 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32132 what="exception catch",catch-type="catch",
32133 thread-groups=["i1"],
32134 regexp="exception_type",times="0"@}
32140 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
32141 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
32142 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32143 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
32144 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32145 thread-id="1",stopped-threads="all",core="6"
32149 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32150 @node GDB/MI Program Context
32151 @section @sc{gdb/mi} Program Context
32153 @subheading The @code{-exec-arguments} Command
32154 @findex -exec-arguments
32157 @subsubheading Synopsis
32160 -exec-arguments @var{args}
32163 Set the inferior program arguments, to be used in the next
32166 @subsubheading @value{GDBN} Command
32168 The corresponding @value{GDBN} command is @samp{set args}.
32170 @subsubheading Example
32174 -exec-arguments -v word
32181 @subheading The @code{-exec-show-arguments} Command
32182 @findex -exec-show-arguments
32184 @subsubheading Synopsis
32187 -exec-show-arguments
32190 Print the arguments of the program.
32192 @subsubheading @value{GDBN} Command
32194 The corresponding @value{GDBN} command is @samp{show args}.
32196 @subsubheading Example
32201 @subheading The @code{-environment-cd} Command
32202 @findex -environment-cd
32204 @subsubheading Synopsis
32207 -environment-cd @var{pathdir}
32210 Set @value{GDBN}'s working directory.
32212 @subsubheading @value{GDBN} Command
32214 The corresponding @value{GDBN} command is @samp{cd}.
32216 @subsubheading Example
32220 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32226 @subheading The @code{-environment-directory} Command
32227 @findex -environment-directory
32229 @subsubheading Synopsis
32232 -environment-directory [ -r ] [ @var{pathdir} ]+
32235 Add directories @var{pathdir} to beginning of search path for source files.
32236 If the @samp{-r} option is used, the search path is reset to the default
32237 search path. If directories @var{pathdir} are supplied in addition to the
32238 @samp{-r} option, the search path is first reset and then addition
32240 Multiple directories may be specified, separated by blanks. Specifying
32241 multiple directories in a single command
32242 results in the directories added to the beginning of the
32243 search path in the same order they were presented in the command.
32244 If blanks are needed as
32245 part of a directory name, double-quotes should be used around
32246 the name. In the command output, the path will show up separated
32247 by the system directory-separator character. The directory-separator
32248 character must not be used
32249 in any directory name.
32250 If no directories are specified, the current search path is displayed.
32252 @subsubheading @value{GDBN} Command
32254 The corresponding @value{GDBN} command is @samp{dir}.
32256 @subsubheading Example
32260 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32261 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32263 -environment-directory ""
32264 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32266 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
32267 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
32269 -environment-directory -r
32270 ^done,source-path="$cdir:$cwd"
32275 @subheading The @code{-environment-path} Command
32276 @findex -environment-path
32278 @subsubheading Synopsis
32281 -environment-path [ -r ] [ @var{pathdir} ]+
32284 Add directories @var{pathdir} to beginning of search path for object files.
32285 If the @samp{-r} option is used, the search path is reset to the original
32286 search path that existed at gdb start-up. If directories @var{pathdir} are
32287 supplied in addition to the
32288 @samp{-r} option, the search path is first reset and then addition
32290 Multiple directories may be specified, separated by blanks. Specifying
32291 multiple directories in a single command
32292 results in the directories added to the beginning of the
32293 search path in the same order they were presented in the command.
32294 If blanks are needed as
32295 part of a directory name, double-quotes should be used around
32296 the name. In the command output, the path will show up separated
32297 by the system directory-separator character. The directory-separator
32298 character must not be used
32299 in any directory name.
32300 If no directories are specified, the current path is displayed.
32303 @subsubheading @value{GDBN} Command
32305 The corresponding @value{GDBN} command is @samp{path}.
32307 @subsubheading Example
32312 ^done,path="/usr/bin"
32314 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
32315 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
32317 -environment-path -r /usr/local/bin
32318 ^done,path="/usr/local/bin:/usr/bin"
32323 @subheading The @code{-environment-pwd} Command
32324 @findex -environment-pwd
32326 @subsubheading Synopsis
32332 Show the current working directory.
32334 @subsubheading @value{GDBN} Command
32336 The corresponding @value{GDBN} command is @samp{pwd}.
32338 @subsubheading Example
32343 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
32347 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32348 @node GDB/MI Thread Commands
32349 @section @sc{gdb/mi} Thread Commands
32352 @subheading The @code{-thread-info} Command
32353 @findex -thread-info
32355 @subsubheading Synopsis
32358 -thread-info [ @var{thread-id} ]
32361 Reports information about either a specific thread, if the
32362 @var{thread-id} parameter is present, or about all threads.
32363 @var{thread-id} is the thread's global thread ID. When printing
32364 information about all threads, also reports the global ID of the
32367 @subsubheading @value{GDBN} Command
32369 The @samp{info thread} command prints the same information
32372 @subsubheading Result
32374 The result contains the following attributes:
32378 A list of threads. The format of the elements of the list is described in
32379 @ref{GDB/MI Thread Information}.
32381 @item current-thread-id
32382 The global id of the currently selected thread. This field is omitted if there
32383 is no selected thread (for example, when the selected inferior is not running,
32384 and therefore has no threads) or if a @var{thread-id} argument was passed to
32389 @subsubheading Example
32394 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32395 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
32396 args=[]@},state="running"@},
32397 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32398 frame=@{level="0",addr="0x0804891f",func="foo",
32399 args=[@{name="i",value="10"@}],
32400 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32401 state="running"@}],
32402 current-thread-id="1"
32406 @subheading The @code{-thread-list-ids} Command
32407 @findex -thread-list-ids
32409 @subsubheading Synopsis
32415 Produces a list of the currently known global @value{GDBN} thread ids.
32416 At the end of the list it also prints the total number of such
32419 This command is retained for historical reasons, the
32420 @code{-thread-info} command should be used instead.
32422 @subsubheading @value{GDBN} Command
32424 Part of @samp{info threads} supplies the same information.
32426 @subsubheading Example
32431 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32432 current-thread-id="1",number-of-threads="3"
32437 @subheading The @code{-thread-select} Command
32438 @findex -thread-select
32440 @subsubheading Synopsis
32443 -thread-select @var{thread-id}
32446 Make thread with global thread number @var{thread-id} the current
32447 thread. It prints the number of the new current thread, and the
32448 topmost frame for that thread.
32450 This command is deprecated in favor of explicitly using the
32451 @samp{--thread} option to each command.
32453 @subsubheading @value{GDBN} Command
32455 The corresponding @value{GDBN} command is @samp{thread}.
32457 @subsubheading Example
32464 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32465 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32469 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32470 number-of-threads="3"
32473 ^done,new-thread-id="3",
32474 frame=@{level="0",func="vprintf",
32475 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32476 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32480 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32481 @node GDB/MI Ada Tasking Commands
32482 @section @sc{gdb/mi} Ada Tasking Commands
32484 @subheading The @code{-ada-task-info} Command
32485 @findex -ada-task-info
32487 @subsubheading Synopsis
32490 -ada-task-info [ @var{task-id} ]
32493 Reports information about either a specific Ada task, if the
32494 @var{task-id} parameter is present, or about all Ada tasks.
32496 @subsubheading @value{GDBN} Command
32498 The @samp{info tasks} command prints the same information
32499 about all Ada tasks (@pxref{Ada Tasks}).
32501 @subsubheading Result
32503 The result is a table of Ada tasks. The following columns are
32504 defined for each Ada task:
32508 This field exists only for the current thread. It has the value @samp{*}.
32511 The identifier that @value{GDBN} uses to refer to the Ada task.
32514 The identifier that the target uses to refer to the Ada task.
32517 The global thread identifier of the thread corresponding to the Ada
32520 This field should always exist, as Ada tasks are always implemented
32521 on top of a thread. But if @value{GDBN} cannot find this corresponding
32522 thread for any reason, the field is omitted.
32525 This field exists only when the task was created by another task.
32526 In this case, it provides the ID of the parent task.
32529 The base priority of the task.
32532 The current state of the task. For a detailed description of the
32533 possible states, see @ref{Ada Tasks}.
32536 The name of the task.
32540 @subsubheading Example
32544 ^done,tasks=@{nr_rows="3",nr_cols="8",
32545 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32546 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32547 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32548 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32549 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32550 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32551 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32552 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32553 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32554 state="Child Termination Wait",name="main_task"@}]@}
32558 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32559 @node GDB/MI Program Execution
32560 @section @sc{gdb/mi} Program Execution
32562 These are the asynchronous commands which generate the out-of-band
32563 record @samp{*stopped}. Currently @value{GDBN} only really executes
32564 asynchronously with remote targets and this interaction is mimicked in
32567 @subheading The @code{-exec-continue} Command
32568 @findex -exec-continue
32570 @subsubheading Synopsis
32573 -exec-continue [--reverse] [--all|--thread-group N]
32576 Resumes the execution of the inferior program, which will continue
32577 to execute until it reaches a debugger stop event. If the
32578 @samp{--reverse} option is specified, execution resumes in reverse until
32579 it reaches a stop event. Stop events may include
32582 breakpoints or watchpoints
32584 signals or exceptions
32586 the end of the process (or its beginning under @samp{--reverse})
32588 the end or beginning of a replay log if one is being used.
32590 In all-stop mode (@pxref{All-Stop
32591 Mode}), may resume only one thread, or all threads, depending on the
32592 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32593 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32594 ignored in all-stop mode. If the @samp{--thread-group} options is
32595 specified, then all threads in that thread group are resumed.
32597 @subsubheading @value{GDBN} Command
32599 The corresponding @value{GDBN} corresponding is @samp{continue}.
32601 @subsubheading Example
32608 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32609 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32610 line="13",arch="i386:x86_64"@}
32615 @subheading The @code{-exec-finish} Command
32616 @findex -exec-finish
32618 @subsubheading Synopsis
32621 -exec-finish [--reverse]
32624 Resumes the execution of the inferior program until the current
32625 function is exited. Displays the results returned by the function.
32626 If the @samp{--reverse} option is specified, resumes the reverse
32627 execution of the inferior program until the point where current
32628 function was called.
32630 @subsubheading @value{GDBN} Command
32632 The corresponding @value{GDBN} command is @samp{finish}.
32634 @subsubheading Example
32636 Function returning @code{void}.
32643 *stopped,reason="function-finished",frame=@{func="main",args=[],
32644 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32648 Function returning other than @code{void}. The name of the internal
32649 @value{GDBN} variable storing the result is printed, together with the
32656 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32657 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32658 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32659 arch="i386:x86_64"@},
32660 gdb-result-var="$1",return-value="0"
32665 @subheading The @code{-exec-interrupt} Command
32666 @findex -exec-interrupt
32668 @subsubheading Synopsis
32671 -exec-interrupt [--all|--thread-group N]
32674 Interrupts the background execution of the target. Note how the token
32675 associated with the stop message is the one for the execution command
32676 that has been interrupted. The token for the interrupt itself only
32677 appears in the @samp{^done} output. If the user is trying to
32678 interrupt a non-running program, an error message will be printed.
32680 Note that when asynchronous execution is enabled, this command is
32681 asynchronous just like other execution commands. That is, first the
32682 @samp{^done} response will be printed, and the target stop will be
32683 reported after that using the @samp{*stopped} notification.
32685 In non-stop mode, only the context thread is interrupted by default.
32686 All threads (in all inferiors) will be interrupted if the
32687 @samp{--all} option is specified. If the @samp{--thread-group}
32688 option is specified, all threads in that group will be interrupted.
32690 @subsubheading @value{GDBN} Command
32692 The corresponding @value{GDBN} command is @samp{interrupt}.
32694 @subsubheading Example
32705 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32706 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32707 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32712 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32716 @subheading The @code{-exec-jump} Command
32719 @subsubheading Synopsis
32722 -exec-jump @var{locspec}
32725 Resumes execution of the inferior program at the address to
32726 which @var{locspec} resolves. @xref{Location Specifications},
32727 for a description of the different forms of @var{locspec}.
32729 @subsubheading @value{GDBN} Command
32731 The corresponding @value{GDBN} command is @samp{jump}.
32733 @subsubheading Example
32736 -exec-jump foo.c:10
32737 *running,thread-id="all"
32742 @subheading The @code{-exec-next} Command
32745 @subsubheading Synopsis
32748 -exec-next [--reverse]
32751 Resumes execution of the inferior program, stopping when the beginning
32752 of the next source line is reached.
32754 If the @samp{--reverse} option is specified, resumes reverse execution
32755 of the inferior program, stopping at the beginning of the previous
32756 source line. If you issue this command on the first line of a
32757 function, it will take you back to the caller of that function, to the
32758 source line where the function was called.
32761 @subsubheading @value{GDBN} Command
32763 The corresponding @value{GDBN} command is @samp{next}.
32765 @subsubheading Example
32771 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32776 @subheading The @code{-exec-next-instruction} Command
32777 @findex -exec-next-instruction
32779 @subsubheading Synopsis
32782 -exec-next-instruction [--reverse]
32785 Executes one machine instruction. If the instruction is a function
32786 call, continues until the function returns. If the program stops at an
32787 instruction in the middle of a source line, the address will be
32790 If the @samp{--reverse} option is specified, resumes reverse execution
32791 of the inferior program, stopping at the previous instruction. If the
32792 previously executed instruction was a return from another function,
32793 it will continue to execute in reverse until the call to that function
32794 (from the current stack frame) is reached.
32796 @subsubheading @value{GDBN} Command
32798 The corresponding @value{GDBN} command is @samp{nexti}.
32800 @subsubheading Example
32804 -exec-next-instruction
32808 *stopped,reason="end-stepping-range",
32809 addr="0x000100d4",line="5",file="hello.c"
32814 @subheading The @code{-exec-return} Command
32815 @findex -exec-return
32817 @subsubheading Synopsis
32823 Makes current function return immediately. Doesn't execute the inferior.
32824 Displays the new current frame.
32826 @subsubheading @value{GDBN} Command
32828 The corresponding @value{GDBN} command is @samp{return}.
32830 @subsubheading Example
32834 200-break-insert callee4
32835 200^done,bkpt=@{number="1",addr="0x00010734",
32836 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
32841 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32842 frame=@{func="callee4",args=[],
32843 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32844 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32845 arch="i386:x86_64"@}
32851 111^done,frame=@{level="0",func="callee3",
32852 args=[@{name="strarg",
32853 value="0x11940 \"A string argument.\""@}],
32854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32855 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32856 arch="i386:x86_64"@}
32861 @subheading The @code{-exec-run} Command
32864 @subsubheading Synopsis
32867 -exec-run [ --all | --thread-group N ] [ --start ]
32870 Starts execution of the inferior from the beginning. The inferior
32871 executes until either a breakpoint is encountered or the program
32872 exits. In the latter case the output will include an exit code, if
32873 the program has exited exceptionally.
32875 When neither the @samp{--all} nor the @samp{--thread-group} option
32876 is specified, the current inferior is started. If the
32877 @samp{--thread-group} option is specified, it should refer to a thread
32878 group of type @samp{process}, and that thread group will be started.
32879 If the @samp{--all} option is specified, then all inferiors will be started.
32881 Using the @samp{--start} option instructs the debugger to stop
32882 the execution at the start of the inferior's main subprogram,
32883 following the same behavior as the @code{start} command
32884 (@pxref{Starting}).
32886 @subsubheading @value{GDBN} Command
32888 The corresponding @value{GDBN} command is @samp{run}.
32890 @subsubheading Examples
32895 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
32900 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32901 frame=@{func="main",args=[],file="recursive2.c",
32902 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
32907 Program exited normally:
32915 *stopped,reason="exited-normally"
32920 Program exited exceptionally:
32928 *stopped,reason="exited",exit-code="01"
32932 Another way the program can terminate is if it receives a signal such as
32933 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
32937 *stopped,reason="exited-signalled",signal-name="SIGINT",
32938 signal-meaning="Interrupt"
32942 @c @subheading -exec-signal
32945 @subheading The @code{-exec-step} Command
32948 @subsubheading Synopsis
32951 -exec-step [--reverse]
32954 Resumes execution of the inferior program, stopping when the beginning
32955 of the next source line is reached, if the next source line is not a
32956 function call. If it is, stop at the first instruction of the called
32957 function. If the @samp{--reverse} option is specified, resumes reverse
32958 execution of the inferior program, stopping at the beginning of the
32959 previously executed source line.
32961 @subsubheading @value{GDBN} Command
32963 The corresponding @value{GDBN} command is @samp{step}.
32965 @subsubheading Example
32967 Stepping into a function:
32973 *stopped,reason="end-stepping-range",
32974 frame=@{func="foo",args=[@{name="a",value="10"@},
32975 @{name="b",value="0"@}],file="recursive2.c",
32976 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
32986 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
32991 @subheading The @code{-exec-step-instruction} Command
32992 @findex -exec-step-instruction
32994 @subsubheading Synopsis
32997 -exec-step-instruction [--reverse]
33000 Resumes the inferior which executes one machine instruction. If the
33001 @samp{--reverse} option is specified, resumes reverse execution of the
33002 inferior program, stopping at the previously executed instruction.
33003 The output, once @value{GDBN} has stopped, will vary depending on
33004 whether we have stopped in the middle of a source line or not. In the
33005 former case, the address at which the program stopped will be printed
33008 @subsubheading @value{GDBN} Command
33010 The corresponding @value{GDBN} command is @samp{stepi}.
33012 @subsubheading Example
33016 -exec-step-instruction
33020 *stopped,reason="end-stepping-range",
33021 frame=@{func="foo",args=[],file="try.c",
33022 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33024 -exec-step-instruction
33028 *stopped,reason="end-stepping-range",
33029 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
33030 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33035 @subheading The @code{-exec-until} Command
33036 @findex -exec-until
33038 @subsubheading Synopsis
33041 -exec-until [ @var{locspec} ]
33044 Executes the inferior until it reaches the address to which
33045 @var{locspec} resolves. If there is no argument, the inferior
33046 executes until it reaches a source line greater than the current one.
33047 The reason for stopping in this case will be @samp{location-reached}.
33049 @subsubheading @value{GDBN} Command
33051 The corresponding @value{GDBN} command is @samp{until}.
33053 @subsubheading Example
33057 -exec-until recursive2.c:6
33061 *stopped,reason="location-reached",frame=@{func="main",args=[],
33062 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
33063 arch="i386:x86_64"@}
33068 @subheading -file-clear
33069 Is this going away????
33072 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33073 @node GDB/MI Stack Manipulation
33074 @section @sc{gdb/mi} Stack Manipulation Commands
33076 @subheading The @code{-enable-frame-filters} Command
33077 @findex -enable-frame-filters
33080 -enable-frame-filters
33083 @value{GDBN} allows Python-based frame filters to affect the output of
33084 the MI commands relating to stack traces. As there is no way to
33085 implement this in a fully backward-compatible way, a front end must
33086 request that this functionality be enabled.
33088 Once enabled, this feature cannot be disabled.
33090 Note that if Python support has not been compiled into @value{GDBN},
33091 this command will still succeed (and do nothing).
33093 @subheading The @code{-stack-info-frame} Command
33094 @findex -stack-info-frame
33096 @subsubheading Synopsis
33102 Get info on the selected frame.
33104 @subsubheading @value{GDBN} Command
33106 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
33107 (without arguments).
33109 @subsubheading Example
33114 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
33115 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33116 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33117 arch="i386:x86_64"@}
33121 @subheading The @code{-stack-info-depth} Command
33122 @findex -stack-info-depth
33124 @subsubheading Synopsis
33127 -stack-info-depth [ @var{max-depth} ]
33130 Return the depth of the stack. If the integer argument @var{max-depth}
33131 is specified, do not count beyond @var{max-depth} frames.
33133 @subsubheading @value{GDBN} Command
33135 There's no equivalent @value{GDBN} command.
33137 @subsubheading Example
33139 For a stack with frame levels 0 through 11:
33146 -stack-info-depth 4
33149 -stack-info-depth 12
33152 -stack-info-depth 11
33155 -stack-info-depth 13
33160 @anchor{-stack-list-arguments}
33161 @subheading The @code{-stack-list-arguments} Command
33162 @findex -stack-list-arguments
33164 @subsubheading Synopsis
33167 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33168 [ @var{low-frame} @var{high-frame} ]
33171 Display a list of the arguments for the frames between @var{low-frame}
33172 and @var{high-frame} (inclusive). If @var{low-frame} and
33173 @var{high-frame} are not provided, list the arguments for the whole
33174 call stack. If the two arguments are equal, show the single frame
33175 at the corresponding level. It is an error if @var{low-frame} is
33176 larger than the actual number of frames. On the other hand,
33177 @var{high-frame} may be larger than the actual number of frames, in
33178 which case only existing frames will be returned.
33180 If @var{print-values} is 0 or @code{--no-values}, print only the names of
33181 the variables; if it is 1 or @code{--all-values}, print also their
33182 values; and if it is 2 or @code{--simple-values}, print the name,
33183 type and value for simple data types, and the name and type for arrays,
33184 structures and unions. If the option @code{--no-frame-filters} is
33185 supplied, then Python frame filters will not be executed.
33187 If the @code{--skip-unavailable} option is specified, arguments that
33188 are not available are not listed. Partially available arguments
33189 are still displayed, however.
33191 Use of this command to obtain arguments in a single frame is
33192 deprecated in favor of the @samp{-stack-list-variables} command.
33194 @subsubheading @value{GDBN} Command
33196 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
33197 @samp{gdb_get_args} command which partially overlaps with the
33198 functionality of @samp{-stack-list-arguments}.
33200 @subsubheading Example
33207 frame=@{level="0",addr="0x00010734",func="callee4",
33208 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33209 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33210 arch="i386:x86_64"@},
33211 frame=@{level="1",addr="0x0001076c",func="callee3",
33212 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33213 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33214 arch="i386:x86_64"@},
33215 frame=@{level="2",addr="0x0001078c",func="callee2",
33216 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33217 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
33218 arch="i386:x86_64"@},
33219 frame=@{level="3",addr="0x000107b4",func="callee1",
33220 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33221 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
33222 arch="i386:x86_64"@},
33223 frame=@{level="4",addr="0x000107e0",func="main",
33224 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33225 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
33226 arch="i386:x86_64"@}]
33228 -stack-list-arguments 0
33231 frame=@{level="0",args=[]@},
33232 frame=@{level="1",args=[name="strarg"]@},
33233 frame=@{level="2",args=[name="intarg",name="strarg"]@},
33234 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
33235 frame=@{level="4",args=[]@}]
33237 -stack-list-arguments 1
33240 frame=@{level="0",args=[]@},
33242 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33243 frame=@{level="2",args=[
33244 @{name="intarg",value="2"@},
33245 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33246 @{frame=@{level="3",args=[
33247 @{name="intarg",value="2"@},
33248 @{name="strarg",value="0x11940 \"A string argument.\""@},
33249 @{name="fltarg",value="3.5"@}]@},
33250 frame=@{level="4",args=[]@}]
33252 -stack-list-arguments 0 2 2
33253 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
33255 -stack-list-arguments 1 2 2
33256 ^done,stack-args=[frame=@{level="2",
33257 args=[@{name="intarg",value="2"@},
33258 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
33262 @c @subheading -stack-list-exception-handlers
33265 @anchor{-stack-list-frames}
33266 @subheading The @code{-stack-list-frames} Command
33267 @findex -stack-list-frames
33269 @subsubheading Synopsis
33272 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
33275 List the frames currently on the stack. For each frame it displays the
33280 The frame number, 0 being the topmost frame, i.e., the innermost function.
33282 The @code{$pc} value for that frame.
33286 File name of the source file where the function lives.
33287 @item @var{fullname}
33288 The full file name of the source file where the function lives.
33290 Line number corresponding to the @code{$pc}.
33292 The shared library where this function is defined. This is only given
33293 if the frame's function is not known.
33295 Frame's architecture.
33298 If invoked without arguments, this command prints a backtrace for the
33299 whole stack. If given two integer arguments, it shows the frames whose
33300 levels are between the two arguments (inclusive). If the two arguments
33301 are equal, it shows the single frame at the corresponding level. It is
33302 an error if @var{low-frame} is larger than the actual number of
33303 frames. On the other hand, @var{high-frame} may be larger than the
33304 actual number of frames, in which case only existing frames will be
33305 returned. If the option @code{--no-frame-filters} is supplied, then
33306 Python frame filters will not be executed.
33308 @subsubheading @value{GDBN} Command
33310 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
33312 @subsubheading Example
33314 Full stack backtrace:
33320 [frame=@{level="0",addr="0x0001076c",func="foo",
33321 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
33322 arch="i386:x86_64"@},
33323 frame=@{level="1",addr="0x000107a4",func="foo",
33324 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33325 arch="i386:x86_64"@},
33326 frame=@{level="2",addr="0x000107a4",func="foo",
33327 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33328 arch="i386:x86_64"@},
33329 frame=@{level="3",addr="0x000107a4",func="foo",
33330 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33331 arch="i386:x86_64"@},
33332 frame=@{level="4",addr="0x000107a4",func="foo",
33333 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33334 arch="i386:x86_64"@},
33335 frame=@{level="5",addr="0x000107a4",func="foo",
33336 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33337 arch="i386:x86_64"@},
33338 frame=@{level="6",addr="0x000107a4",func="foo",
33339 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33340 arch="i386:x86_64"@},
33341 frame=@{level="7",addr="0x000107a4",func="foo",
33342 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33343 arch="i386:x86_64"@},
33344 frame=@{level="8",addr="0x000107a4",func="foo",
33345 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33346 arch="i386:x86_64"@},
33347 frame=@{level="9",addr="0x000107a4",func="foo",
33348 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33349 arch="i386:x86_64"@},
33350 frame=@{level="10",addr="0x000107a4",func="foo",
33351 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33352 arch="i386:x86_64"@},
33353 frame=@{level="11",addr="0x00010738",func="main",
33354 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
33355 arch="i386:x86_64"@}]
33359 Show frames between @var{low_frame} and @var{high_frame}:
33363 -stack-list-frames 3 5
33365 [frame=@{level="3",addr="0x000107a4",func="foo",
33366 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33367 arch="i386:x86_64"@},
33368 frame=@{level="4",addr="0x000107a4",func="foo",
33369 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33370 arch="i386:x86_64"@},
33371 frame=@{level="5",addr="0x000107a4",func="foo",
33372 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33373 arch="i386:x86_64"@}]
33377 Show a single frame:
33381 -stack-list-frames 3 3
33383 [frame=@{level="3",addr="0x000107a4",func="foo",
33384 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33385 arch="i386:x86_64"@}]
33390 @subheading The @code{-stack-list-locals} Command
33391 @findex -stack-list-locals
33392 @anchor{-stack-list-locals}
33394 @subsubheading Synopsis
33397 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33400 Display the local variable names for the selected frame. If
33401 @var{print-values} is 0 or @code{--no-values}, print only the names of
33402 the variables; if it is 1 or @code{--all-values}, print also their
33403 values; and if it is 2 or @code{--simple-values}, print the name,
33404 type and value for simple data types, and the name and type for arrays,
33405 structures and unions. In this last case, a frontend can immediately
33406 display the value of simple data types and create variable objects for
33407 other data types when the user wishes to explore their values in
33408 more detail. If the option @code{--no-frame-filters} is supplied, then
33409 Python frame filters will not be executed.
33411 If the @code{--skip-unavailable} option is specified, local variables
33412 that are not available are not listed. Partially available local
33413 variables are still displayed, however.
33415 This command is deprecated in favor of the
33416 @samp{-stack-list-variables} command.
33418 @subsubheading @value{GDBN} Command
33420 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33422 @subsubheading Example
33426 -stack-list-locals 0
33427 ^done,locals=[name="A",name="B",name="C"]
33429 -stack-list-locals --all-values
33430 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33431 @{name="C",value="@{1, 2, 3@}"@}]
33432 -stack-list-locals --simple-values
33433 ^done,locals=[@{name="A",type="int",value="1"@},
33434 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33438 @anchor{-stack-list-variables}
33439 @subheading The @code{-stack-list-variables} Command
33440 @findex -stack-list-variables
33442 @subsubheading Synopsis
33445 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33448 Display the names of local variables and function arguments for the selected frame. If
33449 @var{print-values} is 0 or @code{--no-values}, print only the names of
33450 the variables; if it is 1 or @code{--all-values}, print also their
33451 values; and if it is 2 or @code{--simple-values}, print the name,
33452 type and value for simple data types, and the name and type for arrays,
33453 structures and unions. If the option @code{--no-frame-filters} is
33454 supplied, then Python frame filters will not be executed.
33456 If the @code{--skip-unavailable} option is specified, local variables
33457 and arguments that are not available are not listed. Partially
33458 available arguments and local variables are still displayed, however.
33460 @subsubheading Example
33464 -stack-list-variables --thread 1 --frame 0 --all-values
33465 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33470 @subheading The @code{-stack-select-frame} Command
33471 @findex -stack-select-frame
33473 @subsubheading Synopsis
33476 -stack-select-frame @var{framenum}
33479 Change the selected frame. Select a different frame @var{framenum} on
33482 This command in deprecated in favor of passing the @samp{--frame}
33483 option to every command.
33485 @subsubheading @value{GDBN} Command
33487 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33488 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33490 @subsubheading Example
33494 -stack-select-frame 2
33499 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33500 @node GDB/MI Variable Objects
33501 @section @sc{gdb/mi} Variable Objects
33505 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33507 For the implementation of a variable debugger window (locals, watched
33508 expressions, etc.), we are proposing the adaptation of the existing code
33509 used by @code{Insight}.
33511 The two main reasons for that are:
33515 It has been proven in practice (it is already on its second generation).
33518 It will shorten development time (needless to say how important it is
33522 The original interface was designed to be used by Tcl code, so it was
33523 slightly changed so it could be used through @sc{gdb/mi}. This section
33524 describes the @sc{gdb/mi} operations that will be available and gives some
33525 hints about their use.
33527 @emph{Note}: In addition to the set of operations described here, we
33528 expect the @sc{gui} implementation of a variable window to require, at
33529 least, the following operations:
33532 @item @code{-gdb-show} @code{output-radix}
33533 @item @code{-stack-list-arguments}
33534 @item @code{-stack-list-locals}
33535 @item @code{-stack-select-frame}
33540 @subheading Introduction to Variable Objects
33542 @cindex variable objects in @sc{gdb/mi}
33544 Variable objects are "object-oriented" MI interface for examining and
33545 changing values of expressions. Unlike some other MI interfaces that
33546 work with expressions, variable objects are specifically designed for
33547 simple and efficient presentation in the frontend. A variable object
33548 is identified by string name. When a variable object is created, the
33549 frontend specifies the expression for that variable object. The
33550 expression can be a simple variable, or it can be an arbitrary complex
33551 expression, and can even involve CPU registers. After creating a
33552 variable object, the frontend can invoke other variable object
33553 operations---for example to obtain or change the value of a variable
33554 object, or to change display format.
33556 Variable objects have hierarchical tree structure. Any variable object
33557 that corresponds to a composite type, such as structure in C, has
33558 a number of child variable objects, for example corresponding to each
33559 element of a structure. A child variable object can itself have
33560 children, recursively. Recursion ends when we reach
33561 leaf variable objects, which always have built-in types. Child variable
33562 objects are created only by explicit request, so if a frontend
33563 is not interested in the children of a particular variable object, no
33564 child will be created.
33566 For a leaf variable object it is possible to obtain its value as a
33567 string, or set the value from a string. String value can be also
33568 obtained for a non-leaf variable object, but it's generally a string
33569 that only indicates the type of the object, and does not list its
33570 contents. Assignment to a non-leaf variable object is not allowed.
33572 A frontend does not need to read the values of all variable objects each time
33573 the program stops. Instead, MI provides an update command that lists all
33574 variable objects whose values has changed since the last update
33575 operation. This considerably reduces the amount of data that must
33576 be transferred to the frontend. As noted above, children variable
33577 objects are created on demand, and only leaf variable objects have a
33578 real value. As result, gdb will read target memory only for leaf
33579 variables that frontend has created.
33581 The automatic update is not always desirable. For example, a frontend
33582 might want to keep a value of some expression for future reference,
33583 and never update it. For another example, fetching memory is
33584 relatively slow for embedded targets, so a frontend might want
33585 to disable automatic update for the variables that are either not
33586 visible on the screen, or ``closed''. This is possible using so
33587 called ``frozen variable objects''. Such variable objects are never
33588 implicitly updated.
33590 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33591 fixed variable object, the expression is parsed when the variable
33592 object is created, including associating identifiers to specific
33593 variables. The meaning of expression never changes. For a floating
33594 variable object the values of variables whose names appear in the
33595 expressions are re-evaluated every time in the context of the current
33596 frame. Consider this example:
33601 struct work_state state;
33608 If a fixed variable object for the @code{state} variable is created in
33609 this function, and we enter the recursive call, the variable
33610 object will report the value of @code{state} in the top-level
33611 @code{do_work} invocation. On the other hand, a floating variable
33612 object will report the value of @code{state} in the current frame.
33614 If an expression specified when creating a fixed variable object
33615 refers to a local variable, the variable object becomes bound to the
33616 thread and frame in which the variable object is created. When such
33617 variable object is updated, @value{GDBN} makes sure that the
33618 thread/frame combination the variable object is bound to still exists,
33619 and re-evaluates the variable object in context of that thread/frame.
33621 The following is the complete set of @sc{gdb/mi} operations defined to
33622 access this functionality:
33624 @multitable @columnfractions .4 .6
33625 @item @strong{Operation}
33626 @tab @strong{Description}
33628 @item @code{-enable-pretty-printing}
33629 @tab enable Python-based pretty-printing
33630 @item @code{-var-create}
33631 @tab create a variable object
33632 @item @code{-var-delete}
33633 @tab delete the variable object and/or its children
33634 @item @code{-var-set-format}
33635 @tab set the display format of this variable
33636 @item @code{-var-show-format}
33637 @tab show the display format of this variable
33638 @item @code{-var-info-num-children}
33639 @tab tells how many children this object has
33640 @item @code{-var-list-children}
33641 @tab return a list of the object's children
33642 @item @code{-var-info-type}
33643 @tab show the type of this variable object
33644 @item @code{-var-info-expression}
33645 @tab print parent-relative expression that this variable object represents
33646 @item @code{-var-info-path-expression}
33647 @tab print full expression that this variable object represents
33648 @item @code{-var-show-attributes}
33649 @tab is this variable editable? does it exist here?
33650 @item @code{-var-evaluate-expression}
33651 @tab get the value of this variable
33652 @item @code{-var-assign}
33653 @tab set the value of this variable
33654 @item @code{-var-update}
33655 @tab update the variable and its children
33656 @item @code{-var-set-frozen}
33657 @tab set frozenness attribute
33658 @item @code{-var-set-update-range}
33659 @tab set range of children to display on update
33662 In the next subsection we describe each operation in detail and suggest
33663 how it can be used.
33665 @subheading Description And Use of Operations on Variable Objects
33667 @subheading The @code{-enable-pretty-printing} Command
33668 @findex -enable-pretty-printing
33671 -enable-pretty-printing
33674 @value{GDBN} allows Python-based visualizers to affect the output of the
33675 MI variable object commands. However, because there was no way to
33676 implement this in a fully backward-compatible way, a front end must
33677 request that this functionality be enabled.
33679 Once enabled, this feature cannot be disabled.
33681 Note that if Python support has not been compiled into @value{GDBN},
33682 this command will still succeed (and do nothing).
33684 @subheading The @code{-var-create} Command
33685 @findex -var-create
33687 @subsubheading Synopsis
33690 -var-create @{@var{name} | "-"@}
33691 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33694 This operation creates a variable object, which allows the monitoring of
33695 a variable, the result of an expression, a memory cell or a CPU
33698 The @var{name} parameter is the string by which the object can be
33699 referenced. It must be unique. If @samp{-} is specified, the varobj
33700 system will generate a string ``varNNNNNN'' automatically. It will be
33701 unique provided that one does not specify @var{name} of that format.
33702 The command fails if a duplicate name is found.
33704 The frame under which the expression should be evaluated can be
33705 specified by @var{frame-addr}. A @samp{*} indicates that the current
33706 frame should be used. A @samp{@@} indicates that a floating variable
33707 object must be created.
33709 @var{expression} is any expression valid on the current language set (must not
33710 begin with a @samp{*}), or one of the following:
33714 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33717 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33720 @samp{$@var{regname}} --- a CPU register name
33723 @cindex dynamic varobj
33724 A varobj's contents may be provided by a Python-based pretty-printer. In this
33725 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33726 have slightly different semantics in some cases. If the
33727 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33728 will never create a dynamic varobj. This ensures backward
33729 compatibility for existing clients.
33731 @subsubheading Result
33733 This operation returns attributes of the newly-created varobj. These
33738 The name of the varobj.
33741 The number of children of the varobj. This number is not necessarily
33742 reliable for a dynamic varobj. Instead, you must examine the
33743 @samp{has_more} attribute.
33746 The varobj's scalar value. For a varobj whose type is some sort of
33747 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33748 will not be interesting.
33751 The varobj's type. This is a string representation of the type, as
33752 would be printed by the @value{GDBN} CLI. If @samp{print object}
33753 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33754 @emph{actual} (derived) type of the object is shown rather than the
33755 @emph{declared} one.
33758 If a variable object is bound to a specific thread, then this is the
33759 thread's global identifier.
33762 For a dynamic varobj, this indicates whether there appear to be any
33763 children available. For a non-dynamic varobj, this will be 0.
33766 This attribute will be present and have the value @samp{1} if the
33767 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33768 then this attribute will not be present.
33771 A dynamic varobj can supply a display hint to the front end. The
33772 value comes directly from the Python pretty-printer object's
33773 @code{display_hint} method. @xref{Pretty Printing API}.
33776 Typical output will look like this:
33779 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33780 has_more="@var{has_more}"
33784 @subheading The @code{-var-delete} Command
33785 @findex -var-delete
33787 @subsubheading Synopsis
33790 -var-delete [ -c ] @var{name}
33793 Deletes a previously created variable object and all of its children.
33794 With the @samp{-c} option, just deletes the children.
33796 Returns an error if the object @var{name} is not found.
33799 @subheading The @code{-var-set-format} Command
33800 @findex -var-set-format
33802 @subsubheading Synopsis
33805 -var-set-format @var{name} @var{format-spec}
33808 Sets the output format for the value of the object @var{name} to be
33811 @anchor{-var-set-format}
33812 The syntax for the @var{format-spec} is as follows:
33815 @var{format-spec} @expansion{}
33816 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
33819 The natural format is the default format choosen automatically
33820 based on the variable type (like decimal for an @code{int}, hex
33821 for pointers, etc.).
33823 The zero-hexadecimal format has a representation similar to hexadecimal
33824 but with padding zeroes to the left of the value. For example, a 32-bit
33825 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
33826 zero-hexadecimal format.
33828 For a variable with children, the format is set only on the
33829 variable itself, and the children are not affected.
33831 @subheading The @code{-var-show-format} Command
33832 @findex -var-show-format
33834 @subsubheading Synopsis
33837 -var-show-format @var{name}
33840 Returns the format used to display the value of the object @var{name}.
33843 @var{format} @expansion{}
33848 @subheading The @code{-var-info-num-children} Command
33849 @findex -var-info-num-children
33851 @subsubheading Synopsis
33854 -var-info-num-children @var{name}
33857 Returns the number of children of a variable object @var{name}:
33863 Note that this number is not completely reliable for a dynamic varobj.
33864 It will return the current number of children, but more children may
33868 @subheading The @code{-var-list-children} Command
33869 @findex -var-list-children
33871 @subsubheading Synopsis
33874 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
33876 @anchor{-var-list-children}
33878 Return a list of the children of the specified variable object and
33879 create variable objects for them, if they do not already exist. With
33880 a single argument or if @var{print-values} has a value of 0 or
33881 @code{--no-values}, print only the names of the variables; if
33882 @var{print-values} is 1 or @code{--all-values}, also print their
33883 values; and if it is 2 or @code{--simple-values} print the name and
33884 value for simple data types and just the name for arrays, structures
33887 @var{from} and @var{to}, if specified, indicate the range of children
33888 to report. If @var{from} or @var{to} is less than zero, the range is
33889 reset and all children will be reported. Otherwise, children starting
33890 at @var{from} (zero-based) and up to and excluding @var{to} will be
33893 If a child range is requested, it will only affect the current call to
33894 @code{-var-list-children}, but not future calls to @code{-var-update}.
33895 For this, you must instead use @code{-var-set-update-range}. The
33896 intent of this approach is to enable a front end to implement any
33897 update approach it likes; for example, scrolling a view may cause the
33898 front end to request more children with @code{-var-list-children}, and
33899 then the front end could call @code{-var-set-update-range} with a
33900 different range to ensure that future updates are restricted to just
33903 For each child the following results are returned:
33908 Name of the variable object created for this child.
33911 The expression to be shown to the user by the front end to designate this child.
33912 For example this may be the name of a structure member.
33914 For a dynamic varobj, this value cannot be used to form an
33915 expression. There is no way to do this at all with a dynamic varobj.
33917 For C/C@t{++} structures there are several pseudo children returned to
33918 designate access qualifiers. For these pseudo children @var{exp} is
33919 @samp{public}, @samp{private}, or @samp{protected}. In this case the
33920 type and value are not present.
33922 A dynamic varobj will not report the access qualifying
33923 pseudo-children, regardless of the language. This information is not
33924 available at all with a dynamic varobj.
33927 Number of children this child has. For a dynamic varobj, this will be
33931 The type of the child. If @samp{print object}
33932 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33933 @emph{actual} (derived) type of the object is shown rather than the
33934 @emph{declared} one.
33937 If values were requested, this is the value.
33940 If this variable object is associated with a thread, this is the
33941 thread's global thread id. Otherwise this result is not present.
33944 If the variable object is frozen, this variable will be present with a value of 1.
33947 A dynamic varobj can supply a display hint to the front end. The
33948 value comes directly from the Python pretty-printer object's
33949 @code{display_hint} method. @xref{Pretty Printing API}.
33952 This attribute will be present and have the value @samp{1} if the
33953 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33954 then this attribute will not be present.
33958 The result may have its own attributes:
33962 A dynamic varobj can supply a display hint to the front end. The
33963 value comes directly from the Python pretty-printer object's
33964 @code{display_hint} method. @xref{Pretty Printing API}.
33967 This is an integer attribute which is nonzero if there are children
33968 remaining after the end of the selected range.
33971 @subsubheading Example
33975 -var-list-children n
33976 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33977 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
33979 -var-list-children --all-values n
33980 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33981 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
33985 @subheading The @code{-var-info-type} Command
33986 @findex -var-info-type
33988 @subsubheading Synopsis
33991 -var-info-type @var{name}
33994 Returns the type of the specified variable @var{name}. The type is
33995 returned as a string in the same format as it is output by the
33999 type=@var{typename}
34003 @subheading The @code{-var-info-expression} Command
34004 @findex -var-info-expression
34006 @subsubheading Synopsis
34009 -var-info-expression @var{name}
34012 Returns a string that is suitable for presenting this
34013 variable object in user interface. The string is generally
34014 not valid expression in the current language, and cannot be evaluated.
34016 For example, if @code{a} is an array, and variable object
34017 @code{A} was created for @code{a}, then we'll get this output:
34020 (gdb) -var-info-expression A.1
34021 ^done,lang="C",exp="1"
34025 Here, the value of @code{lang} is the language name, which can be
34026 found in @ref{Supported Languages}.
34028 Note that the output of the @code{-var-list-children} command also
34029 includes those expressions, so the @code{-var-info-expression} command
34032 @subheading The @code{-var-info-path-expression} Command
34033 @findex -var-info-path-expression
34035 @subsubheading Synopsis
34038 -var-info-path-expression @var{name}
34041 Returns an expression that can be evaluated in the current
34042 context and will yield the same value that a variable object has.
34043 Compare this with the @code{-var-info-expression} command, which
34044 result can be used only for UI presentation. Typical use of
34045 the @code{-var-info-path-expression} command is creating a
34046 watchpoint from a variable object.
34048 This command is currently not valid for children of a dynamic varobj,
34049 and will give an error when invoked on one.
34051 For example, suppose @code{C} is a C@t{++} class, derived from class
34052 @code{Base}, and that the @code{Base} class has a member called
34053 @code{m_size}. Assume a variable @code{c} is has the type of
34054 @code{C} and a variable object @code{C} was created for variable
34055 @code{c}. Then, we'll get this output:
34057 (gdb) -var-info-path-expression C.Base.public.m_size
34058 ^done,path_expr=((Base)c).m_size)
34061 @subheading The @code{-var-show-attributes} Command
34062 @findex -var-show-attributes
34064 @subsubheading Synopsis
34067 -var-show-attributes @var{name}
34070 List attributes of the specified variable object @var{name}:
34073 status=@var{attr} [ ( ,@var{attr} )* ]
34077 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
34079 @subheading The @code{-var-evaluate-expression} Command
34080 @findex -var-evaluate-expression
34082 @subsubheading Synopsis
34085 -var-evaluate-expression [-f @var{format-spec}] @var{name}
34088 Evaluates the expression that is represented by the specified variable
34089 object and returns its value as a string. The format of the string
34090 can be specified with the @samp{-f} option. The possible values of
34091 this option are the same as for @code{-var-set-format}
34092 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
34093 the current display format will be used. The current display format
34094 can be changed using the @code{-var-set-format} command.
34100 Note that one must invoke @code{-var-list-children} for a variable
34101 before the value of a child variable can be evaluated.
34103 @subheading The @code{-var-assign} Command
34104 @findex -var-assign
34106 @subsubheading Synopsis
34109 -var-assign @var{name} @var{expression}
34112 Assigns the value of @var{expression} to the variable object specified
34113 by @var{name}. The object must be @samp{editable}. If the variable's
34114 value is altered by the assign, the variable will show up in any
34115 subsequent @code{-var-update} list.
34117 @subsubheading Example
34125 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
34129 @subheading The @code{-var-update} Command
34130 @findex -var-update
34132 @subsubheading Synopsis
34135 -var-update [@var{print-values}] @{@var{name} | "*"@}
34138 Reevaluate the expressions corresponding to the variable object
34139 @var{name} and all its direct and indirect children, and return the
34140 list of variable objects whose values have changed; @var{name} must
34141 be a root variable object. Here, ``changed'' means that the result of
34142 @code{-var-evaluate-expression} before and after the
34143 @code{-var-update} is different. If @samp{*} is used as the variable
34144 object names, all existing variable objects are updated, except
34145 for frozen ones (@pxref{-var-set-frozen}). The option
34146 @var{print-values} determines whether both names and values, or just
34147 names are printed. The possible values of this option are the same
34148 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
34149 recommended to use the @samp{--all-values} option, to reduce the
34150 number of MI commands needed on each program stop.
34152 With the @samp{*} parameter, if a variable object is bound to a
34153 currently running thread, it will not be updated, without any
34156 If @code{-var-set-update-range} was previously used on a varobj, then
34157 only the selected range of children will be reported.
34159 @code{-var-update} reports all the changed varobjs in a tuple named
34162 Each item in the change list is itself a tuple holding:
34166 The name of the varobj.
34169 If values were requested for this update, then this field will be
34170 present and will hold the value of the varobj.
34173 @anchor{-var-update}
34174 This field is a string which may take one of three values:
34178 The variable object's current value is valid.
34181 The variable object does not currently hold a valid value but it may
34182 hold one in the future if its associated expression comes back into
34186 The variable object no longer holds a valid value.
34187 This can occur when the executable file being debugged has changed,
34188 either through recompilation or by using the @value{GDBN} @code{file}
34189 command. The front end should normally choose to delete these variable
34193 In the future new values may be added to this list so the front should
34194 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
34197 This is only present if the varobj is still valid. If the type
34198 changed, then this will be the string @samp{true}; otherwise it will
34201 When a varobj's type changes, its children are also likely to have
34202 become incorrect. Therefore, the varobj's children are automatically
34203 deleted when this attribute is @samp{true}. Also, the varobj's update
34204 range, when set using the @code{-var-set-update-range} command, is
34208 If the varobj's type changed, then this field will be present and will
34211 @item new_num_children
34212 For a dynamic varobj, if the number of children changed, or if the
34213 type changed, this will be the new number of children.
34215 The @samp{numchild} field in other varobj responses is generally not
34216 valid for a dynamic varobj -- it will show the number of children that
34217 @value{GDBN} knows about, but because dynamic varobjs lazily
34218 instantiate their children, this will not reflect the number of
34219 children which may be available.
34221 The @samp{new_num_children} attribute only reports changes to the
34222 number of children known by @value{GDBN}. This is the only way to
34223 detect whether an update has removed children (which necessarily can
34224 only happen at the end of the update range).
34227 The display hint, if any.
34230 This is an integer value, which will be 1 if there are more children
34231 available outside the varobj's update range.
34234 This attribute will be present and have the value @samp{1} if the
34235 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34236 then this attribute will not be present.
34239 If new children were added to a dynamic varobj within the selected
34240 update range (as set by @code{-var-set-update-range}), then they will
34241 be listed in this attribute.
34244 @subsubheading Example
34251 -var-update --all-values var1
34252 ^done,changelist=[@{name="var1",value="3",in_scope="true",
34253 type_changed="false"@}]
34257 @subheading The @code{-var-set-frozen} Command
34258 @findex -var-set-frozen
34259 @anchor{-var-set-frozen}
34261 @subsubheading Synopsis
34264 -var-set-frozen @var{name} @var{flag}
34267 Set the frozenness flag on the variable object @var{name}. The
34268 @var{flag} parameter should be either @samp{1} to make the variable
34269 frozen or @samp{0} to make it unfrozen. If a variable object is
34270 frozen, then neither itself, nor any of its children, are
34271 implicitly updated by @code{-var-update} of
34272 a parent variable or by @code{-var-update *}. Only
34273 @code{-var-update} of the variable itself will update its value and
34274 values of its children. After a variable object is unfrozen, it is
34275 implicitly updated by all subsequent @code{-var-update} operations.
34276 Unfreezing a variable does not update it, only subsequent
34277 @code{-var-update} does.
34279 @subsubheading Example
34283 -var-set-frozen V 1
34288 @subheading The @code{-var-set-update-range} command
34289 @findex -var-set-update-range
34290 @anchor{-var-set-update-range}
34292 @subsubheading Synopsis
34295 -var-set-update-range @var{name} @var{from} @var{to}
34298 Set the range of children to be returned by future invocations of
34299 @code{-var-update}.
34301 @var{from} and @var{to} indicate the range of children to report. If
34302 @var{from} or @var{to} is less than zero, the range is reset and all
34303 children will be reported. Otherwise, children starting at @var{from}
34304 (zero-based) and up to and excluding @var{to} will be reported.
34306 @subsubheading Example
34310 -var-set-update-range V 1 2
34314 @subheading The @code{-var-set-visualizer} command
34315 @findex -var-set-visualizer
34316 @anchor{-var-set-visualizer}
34318 @subsubheading Synopsis
34321 -var-set-visualizer @var{name} @var{visualizer}
34324 Set a visualizer for the variable object @var{name}.
34326 @var{visualizer} is the visualizer to use. The special value
34327 @samp{None} means to disable any visualizer in use.
34329 If not @samp{None}, @var{visualizer} must be a Python expression.
34330 This expression must evaluate to a callable object which accepts a
34331 single argument. @value{GDBN} will call this object with the value of
34332 the varobj @var{name} as an argument (this is done so that the same
34333 Python pretty-printing code can be used for both the CLI and MI).
34334 When called, this object must return an object which conforms to the
34335 pretty-printing interface (@pxref{Pretty Printing API}).
34337 The pre-defined function @code{gdb.default_visualizer} may be used to
34338 select a visualizer by following the built-in process
34339 (@pxref{Selecting Pretty-Printers}). This is done automatically when
34340 a varobj is created, and so ordinarily is not needed.
34342 This feature is only available if Python support is enabled. The MI
34343 command @code{-list-features} (@pxref{GDB/MI Support Commands})
34344 can be used to check this.
34346 @subsubheading Example
34348 Resetting the visualizer:
34352 -var-set-visualizer V None
34356 Reselecting the default (type-based) visualizer:
34360 -var-set-visualizer V gdb.default_visualizer
34364 Suppose @code{SomeClass} is a visualizer class. A lambda expression
34365 can be used to instantiate this class for a varobj:
34369 -var-set-visualizer V "lambda val: SomeClass()"
34373 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34374 @node GDB/MI Data Manipulation
34375 @section @sc{gdb/mi} Data Manipulation
34377 @cindex data manipulation, in @sc{gdb/mi}
34378 @cindex @sc{gdb/mi}, data manipulation
34379 This section describes the @sc{gdb/mi} commands that manipulate data:
34380 examine memory and registers, evaluate expressions, etc.
34382 For details about what an addressable memory unit is,
34383 @pxref{addressable memory unit}.
34385 @c REMOVED FROM THE INTERFACE.
34386 @c @subheading -data-assign
34387 @c Change the value of a program variable. Plenty of side effects.
34388 @c @subsubheading GDB Command
34390 @c @subsubheading Example
34393 @subheading The @code{-data-disassemble} Command
34394 @findex -data-disassemble
34396 @subsubheading Synopsis
34400 [ -s @var{start-addr} -e @var{end-addr} ]
34401 | [ -a @var{addr} ]
34402 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
34410 @item @var{start-addr}
34411 is the beginning address (or @code{$pc})
34412 @item @var{end-addr}
34415 is an address anywhere within (or the name of) the function to
34416 disassemble. If an address is specified, the whole function
34417 surrounding that address will be disassembled. If a name is
34418 specified, the whole function with that name will be disassembled.
34419 @item @var{filename}
34420 is the name of the file to disassemble
34421 @item @var{linenum}
34422 is the line number to disassemble around
34424 is the number of disassembly lines to be produced. If it is -1,
34425 the whole function will be disassembled, in case no @var{end-addr} is
34426 specified. If @var{end-addr} is specified as a non-zero value, and
34427 @var{lines} is lower than the number of disassembly lines between
34428 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34429 displayed; if @var{lines} is higher than the number of lines between
34430 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34435 @item 0 disassembly only
34436 @item 1 mixed source and disassembly (deprecated)
34437 @item 2 disassembly with raw opcodes
34438 @item 3 mixed source and disassembly with raw opcodes (deprecated)
34439 @item 4 mixed source and disassembly
34440 @item 5 mixed source and disassembly with raw opcodes
34443 Modes 1 and 3 are deprecated. The output is ``source centric''
34444 which hasn't proved useful in practice.
34445 @xref{Machine Code}, for a discussion of the difference between
34446 @code{/m} and @code{/s} output of the @code{disassemble} command.
34449 @subsubheading Result
34451 The result of the @code{-data-disassemble} command will be a list named
34452 @samp{asm_insns}, the contents of this list depend on the @var{mode}
34453 used with the @code{-data-disassemble} command.
34455 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
34460 The address at which this instruction was disassembled.
34463 The name of the function this instruction is within.
34466 The decimal offset in bytes from the start of @samp{func-name}.
34469 The text disassembly for this @samp{address}.
34472 This field is only present for modes 2, 3 and 5. This contains the
34473 raw opcode bytes for the @samp{inst} field. The bytes are formatted
34474 as single bytes, in hex, in ascending address order, with a single
34475 space between each byte.
34479 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
34480 @samp{src_and_asm_line}, each of which has the following fields:
34484 The line number within @samp{file}.
34487 The file name from the compilation unit. This might be an absolute
34488 file name or a relative file name depending on the compile command
34492 Absolute file name of @samp{file}. It is converted to a canonical form
34493 using the source file search path
34494 (@pxref{Source Path, ,Specifying Source Directories})
34495 and after resolving all the symbolic links.
34497 If the source file is not found this field will contain the path as
34498 present in the debug information.
34500 @item line_asm_insn
34501 This is a list of tuples containing the disassembly for @samp{line} in
34502 @samp{file}. The fields of each tuple are the same as for
34503 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34504 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34509 Note that whatever included in the @samp{inst} field, is not
34510 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34513 @subsubheading @value{GDBN} Command
34515 The corresponding @value{GDBN} command is @samp{disassemble}.
34517 @subsubheading Example
34519 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34523 -data-disassemble -s $pc -e "$pc + 20" -- 0
34526 @{address="0x000107c0",func-name="main",offset="4",
34527 inst="mov 2, %o0"@},
34528 @{address="0x000107c4",func-name="main",offset="8",
34529 inst="sethi %hi(0x11800), %o2"@},
34530 @{address="0x000107c8",func-name="main",offset="12",
34531 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34532 @{address="0x000107cc",func-name="main",offset="16",
34533 inst="sethi %hi(0x11800), %o2"@},
34534 @{address="0x000107d0",func-name="main",offset="20",
34535 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34539 Disassemble the whole @code{main} function. Line 32 is part of
34543 -data-disassemble -f basics.c -l 32 -- 0
34545 @{address="0x000107bc",func-name="main",offset="0",
34546 inst="save %sp, -112, %sp"@},
34547 @{address="0x000107c0",func-name="main",offset="4",
34548 inst="mov 2, %o0"@},
34549 @{address="0x000107c4",func-name="main",offset="8",
34550 inst="sethi %hi(0x11800), %o2"@},
34552 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34553 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34557 Disassemble 3 instructions from the start of @code{main}:
34561 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34563 @{address="0x000107bc",func-name="main",offset="0",
34564 inst="save %sp, -112, %sp"@},
34565 @{address="0x000107c0",func-name="main",offset="4",
34566 inst="mov 2, %o0"@},
34567 @{address="0x000107c4",func-name="main",offset="8",
34568 inst="sethi %hi(0x11800), %o2"@}]
34572 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34576 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34578 src_and_asm_line=@{line="31",
34579 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34580 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34581 line_asm_insn=[@{address="0x000107bc",
34582 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34583 src_and_asm_line=@{line="32",
34584 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34585 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34586 line_asm_insn=[@{address="0x000107c0",
34587 func-name="main",offset="4",inst="mov 2, %o0"@},
34588 @{address="0x000107c4",func-name="main",offset="8",
34589 inst="sethi %hi(0x11800), %o2"@}]@}]
34594 @subheading The @code{-data-evaluate-expression} Command
34595 @findex -data-evaluate-expression
34597 @subsubheading Synopsis
34600 -data-evaluate-expression @var{expr}
34603 Evaluate @var{expr} as an expression. The expression could contain an
34604 inferior function call. The function call will execute synchronously.
34605 If the expression contains spaces, it must be enclosed in double quotes.
34607 @subsubheading @value{GDBN} Command
34609 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34610 @samp{call}. In @code{gdbtk} only, there's a corresponding
34611 @samp{gdb_eval} command.
34613 @subsubheading Example
34615 In the following example, the numbers that precede the commands are the
34616 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34617 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34621 211-data-evaluate-expression A
34624 311-data-evaluate-expression &A
34625 311^done,value="0xefffeb7c"
34627 411-data-evaluate-expression A+3
34630 511-data-evaluate-expression "A + 3"
34636 @subheading The @code{-data-list-changed-registers} Command
34637 @findex -data-list-changed-registers
34639 @subsubheading Synopsis
34642 -data-list-changed-registers
34645 Display a list of the registers that have changed.
34647 @subsubheading @value{GDBN} Command
34649 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
34650 has the corresponding command @samp{gdb_changed_register_list}.
34652 @subsubheading Example
34654 On a PPC MBX board:
34662 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34663 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34664 line="5",arch="powerpc"@}
34666 -data-list-changed-registers
34667 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34668 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34669 "24","25","26","27","28","30","31","64","65","66","67","69"]
34674 @subheading The @code{-data-list-register-names} Command
34675 @findex -data-list-register-names
34677 @subsubheading Synopsis
34680 -data-list-register-names [ ( @var{regno} )+ ]
34683 Show a list of register names for the current target. If no arguments
34684 are given, it shows a list of the names of all the registers. If
34685 integer numbers are given as arguments, it will print a list of the
34686 names of the registers corresponding to the arguments. To ensure
34687 consistency between a register name and its number, the output list may
34688 include empty register names.
34690 @subsubheading @value{GDBN} Command
34692 @value{GDBN} does not have a command which corresponds to
34693 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34694 corresponding command @samp{gdb_regnames}.
34696 @subsubheading Example
34698 For the PPC MBX board:
34701 -data-list-register-names
34702 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34703 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34704 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34705 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34706 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34707 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34708 "", "pc","ps","cr","lr","ctr","xer"]
34710 -data-list-register-names 1 2 3
34711 ^done,register-names=["r1","r2","r3"]
34715 @subheading The @code{-data-list-register-values} Command
34716 @findex -data-list-register-values
34718 @subsubheading Synopsis
34721 -data-list-register-values
34722 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34725 Display the registers' contents. The format according to which the
34726 registers' contents are to be returned is given by @var{fmt}, followed
34727 by an optional list of numbers specifying the registers to display. A
34728 missing list of numbers indicates that the contents of all the
34729 registers must be returned. The @code{--skip-unavailable} option
34730 indicates that only the available registers are to be returned.
34732 Allowed formats for @var{fmt} are:
34749 @subsubheading @value{GDBN} Command
34751 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34752 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34754 @subsubheading Example
34756 For a PPC MBX board (note: line breaks are for readability only, they
34757 don't appear in the actual output):
34761 -data-list-register-values r 64 65
34762 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34763 @{number="65",value="0x00029002"@}]
34765 -data-list-register-values x
34766 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34767 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34768 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34769 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34770 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34771 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34772 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34773 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34774 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34775 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34776 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34777 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34778 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34779 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34780 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34781 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34782 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34783 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34784 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34785 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34786 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34787 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34788 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34789 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34790 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34791 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34792 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34793 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34794 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34795 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34796 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34797 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34798 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34799 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34800 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34801 @{number="69",value="0x20002b03"@}]
34806 @subheading The @code{-data-read-memory} Command
34807 @findex -data-read-memory
34809 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34811 @subsubheading Synopsis
34814 -data-read-memory [ -o @var{byte-offset} ]
34815 @var{address} @var{word-format} @var{word-size}
34816 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
34823 @item @var{address}
34824 An expression specifying the address of the first memory word to be
34825 read. Complex expressions containing embedded white space should be
34826 quoted using the C convention.
34828 @item @var{word-format}
34829 The format to be used to print the memory words. The notation is the
34830 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
34833 @item @var{word-size}
34834 The size of each memory word in bytes.
34836 @item @var{nr-rows}
34837 The number of rows in the output table.
34839 @item @var{nr-cols}
34840 The number of columns in the output table.
34843 If present, indicates that each row should include an @sc{ascii} dump. The
34844 value of @var{aschar} is used as a padding character when a byte is not a
34845 member of the printable @sc{ascii} character set (printable @sc{ascii}
34846 characters are those whose code is between 32 and 126, inclusively).
34848 @item @var{byte-offset}
34849 An offset to add to the @var{address} before fetching memory.
34852 This command displays memory contents as a table of @var{nr-rows} by
34853 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
34854 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
34855 (returned as @samp{total-bytes}). Should less than the requested number
34856 of bytes be returned by the target, the missing words are identified
34857 using @samp{N/A}. The number of bytes read from the target is returned
34858 in @samp{nr-bytes} and the starting address used to read memory in
34861 The address of the next/previous row or page is available in
34862 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
34865 @subsubheading @value{GDBN} Command
34867 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
34868 @samp{gdb_get_mem} memory read command.
34870 @subsubheading Example
34872 Read six bytes of memory starting at @code{bytes+6} but then offset by
34873 @code{-6} bytes. Format as three rows of two columns. One byte per
34874 word. Display each word in hex.
34878 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
34879 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
34880 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
34881 prev-page="0x0000138a",memory=[
34882 @{addr="0x00001390",data=["0x00","0x01"]@},
34883 @{addr="0x00001392",data=["0x02","0x03"]@},
34884 @{addr="0x00001394",data=["0x04","0x05"]@}]
34888 Read two bytes of memory starting at address @code{shorts + 64} and
34889 display as a single word formatted in decimal.
34893 5-data-read-memory shorts+64 d 2 1 1
34894 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
34895 next-row="0x00001512",prev-row="0x0000150e",
34896 next-page="0x00001512",prev-page="0x0000150e",memory=[
34897 @{addr="0x00001510",data=["128"]@}]
34901 Read thirty two bytes of memory starting at @code{bytes+16} and format
34902 as eight rows of four columns. Include a string encoding with @samp{x}
34903 used as the non-printable character.
34907 4-data-read-memory bytes+16 x 1 8 4 x
34908 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
34909 next-row="0x000013c0",prev-row="0x0000139c",
34910 next-page="0x000013c0",prev-page="0x00001380",memory=[
34911 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
34912 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
34913 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
34914 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
34915 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
34916 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
34917 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
34918 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
34922 @subheading The @code{-data-read-memory-bytes} Command
34923 @findex -data-read-memory-bytes
34925 @subsubheading Synopsis
34928 -data-read-memory-bytes [ -o @var{offset} ]
34929 @var{address} @var{count}
34936 @item @var{address}
34937 An expression specifying the address of the first addressable memory unit
34938 to be read. Complex expressions containing embedded white space should be
34939 quoted using the C convention.
34942 The number of addressable memory units to read. This should be an integer
34946 The offset relative to @var{address} at which to start reading. This
34947 should be an integer literal. This option is provided so that a frontend
34948 is not required to first evaluate address and then perform address
34949 arithmetics itself.
34953 This command attempts to read all accessible memory regions in the
34954 specified range. First, all regions marked as unreadable in the memory
34955 map (if one is defined) will be skipped. @xref{Memory Region
34956 Attributes}. Second, @value{GDBN} will attempt to read the remaining
34957 regions. For each one, if reading full region results in an errors,
34958 @value{GDBN} will try to read a subset of the region.
34960 In general, every single memory unit in the region may be readable or not,
34961 and the only way to read every readable unit is to try a read at
34962 every address, which is not practical. Therefore, @value{GDBN} will
34963 attempt to read all accessible memory units at either beginning or the end
34964 of the region, using a binary division scheme. This heuristic works
34965 well for reading across a memory map boundary. Note that if a region
34966 has a readable range that is neither at the beginning or the end,
34967 @value{GDBN} will not read it.
34969 The result record (@pxref{GDB/MI Result Records}) that is output of
34970 the command includes a field named @samp{memory} whose content is a
34971 list of tuples. Each tuple represent a successfully read memory block
34972 and has the following fields:
34976 The start address of the memory block, as hexadecimal literal.
34979 The end address of the memory block, as hexadecimal literal.
34982 The offset of the memory block, as hexadecimal literal, relative to
34983 the start address passed to @code{-data-read-memory-bytes}.
34986 The contents of the memory block, in hex.
34992 @subsubheading @value{GDBN} Command
34994 The corresponding @value{GDBN} command is @samp{x}.
34996 @subsubheading Example
35000 -data-read-memory-bytes &a 10
35001 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
35003 contents="01000000020000000300"@}]
35008 @subheading The @code{-data-write-memory-bytes} Command
35009 @findex -data-write-memory-bytes
35011 @subsubheading Synopsis
35014 -data-write-memory-bytes @var{address} @var{contents}
35015 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
35022 @item @var{address}
35023 An expression specifying the address of the first addressable memory unit
35024 to be written. Complex expressions containing embedded white space should
35025 be quoted using the C convention.
35027 @item @var{contents}
35028 The hex-encoded data to write. It is an error if @var{contents} does
35029 not represent an integral number of addressable memory units.
35032 Optional argument indicating the number of addressable memory units to be
35033 written. If @var{count} is greater than @var{contents}' length,
35034 @value{GDBN} will repeatedly write @var{contents} until it fills
35035 @var{count} memory units.
35039 @subsubheading @value{GDBN} Command
35041 There's no corresponding @value{GDBN} command.
35043 @subsubheading Example
35047 -data-write-memory-bytes &a "aabbccdd"
35054 -data-write-memory-bytes &a "aabbccdd" 16e
35059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35060 @node GDB/MI Tracepoint Commands
35061 @section @sc{gdb/mi} Tracepoint Commands
35063 The commands defined in this section implement MI support for
35064 tracepoints. For detailed introduction, see @ref{Tracepoints}.
35066 @subheading The @code{-trace-find} Command
35067 @findex -trace-find
35069 @subsubheading Synopsis
35072 -trace-find @var{mode} [@var{parameters}@dots{}]
35075 Find a trace frame using criteria defined by @var{mode} and
35076 @var{parameters}. The following table lists permissible
35077 modes and their parameters. For details of operation, see @ref{tfind}.
35082 No parameters are required. Stops examining trace frames.
35085 An integer is required as parameter. Selects tracepoint frame with
35088 @item tracepoint-number
35089 An integer is required as parameter. Finds next
35090 trace frame that corresponds to tracepoint with the specified number.
35093 An address is required as parameter. Finds
35094 next trace frame that corresponds to any tracepoint at the specified
35097 @item pc-inside-range
35098 Two addresses are required as parameters. Finds next trace
35099 frame that corresponds to a tracepoint at an address inside the
35100 specified range. Both bounds are considered to be inside the range.
35102 @item pc-outside-range
35103 Two addresses are required as parameters. Finds
35104 next trace frame that corresponds to a tracepoint at an address outside
35105 the specified range. Both bounds are considered to be inside the range.
35108 Location specification is required as parameter. @xref{Location Specifications}.
35109 Finds next trace frame that corresponds to a tracepoint at
35110 the specified location.
35114 If @samp{none} was passed as @var{mode}, the response does not
35115 have fields. Otherwise, the response may have the following fields:
35119 This field has either @samp{0} or @samp{1} as the value, depending
35120 on whether a matching tracepoint was found.
35123 The index of the found traceframe. This field is present iff
35124 the @samp{found} field has value of @samp{1}.
35127 The index of the found tracepoint. This field is present iff
35128 the @samp{found} field has value of @samp{1}.
35131 The information about the frame corresponding to the found trace
35132 frame. This field is present only if a trace frame was found.
35133 @xref{GDB/MI Frame Information}, for description of this field.
35137 @subsubheading @value{GDBN} Command
35139 The corresponding @value{GDBN} command is @samp{tfind}.
35141 @subheading -trace-define-variable
35142 @findex -trace-define-variable
35144 @subsubheading Synopsis
35147 -trace-define-variable @var{name} [ @var{value} ]
35150 Create trace variable @var{name} if it does not exist. If
35151 @var{value} is specified, sets the initial value of the specified
35152 trace variable to that value. Note that the @var{name} should start
35153 with the @samp{$} character.
35155 @subsubheading @value{GDBN} Command
35157 The corresponding @value{GDBN} command is @samp{tvariable}.
35159 @subheading The @code{-trace-frame-collected} Command
35160 @findex -trace-frame-collected
35162 @subsubheading Synopsis
35165 -trace-frame-collected
35166 [--var-print-values @var{var_pval}]
35167 [--comp-print-values @var{comp_pval}]
35168 [--registers-format @var{regformat}]
35169 [--memory-contents]
35172 This command returns the set of collected objects, register names,
35173 trace state variable names, memory ranges and computed expressions
35174 that have been collected at a particular trace frame. The optional
35175 parameters to the command affect the output format in different ways.
35176 See the output description table below for more details.
35178 The reported names can be used in the normal manner to create
35179 varobjs and inspect the objects themselves. The items returned by
35180 this command are categorized so that it is clear which is a variable,
35181 which is a register, which is a trace state variable, which is a
35182 memory range and which is a computed expression.
35184 For instance, if the actions were
35186 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
35187 collect *(int*)0xaf02bef0@@40
35191 the object collected in its entirety would be @code{myVar}. The
35192 object @code{myArray} would be partially collected, because only the
35193 element at index @code{myIndex} would be collected. The remaining
35194 objects would be computed expressions.
35196 An example output would be:
35200 -trace-frame-collected
35202 explicit-variables=[@{name="myVar",value="1"@}],
35203 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
35204 @{name="myObj.field",value="0"@},
35205 @{name="myPtr->field",value="1"@},
35206 @{name="myCount + 2",value="3"@},
35207 @{name="$tvar1 + 1",value="43970027"@}],
35208 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
35209 @{number="1",value="0x0"@},
35210 @{number="2",value="0x4"@},
35212 @{number="125",value="0x0"@}],
35213 tvars=[@{name="$tvar1",current="43970026"@}],
35214 memory=[@{address="0x0000000000602264",length="4"@},
35215 @{address="0x0000000000615bc0",length="4"@}]
35222 @item explicit-variables
35223 The set of objects that have been collected in their entirety (as
35224 opposed to collecting just a few elements of an array or a few struct
35225 members). For each object, its name and value are printed.
35226 The @code{--var-print-values} option affects how or whether the value
35227 field is output. If @var{var_pval} is 0, then print only the names;
35228 if it is 1, print also their values; and if it is 2, print the name,
35229 type and value for simple data types, and the name and type for
35230 arrays, structures and unions.
35232 @item computed-expressions
35233 The set of computed expressions that have been collected at the
35234 current trace frame. The @code{--comp-print-values} option affects
35235 this set like the @code{--var-print-values} option affects the
35236 @code{explicit-variables} set. See above.
35239 The registers that have been collected at the current trace frame.
35240 For each register collected, the name and current value are returned.
35241 The value is formatted according to the @code{--registers-format}
35242 option. See the @command{-data-list-register-values} command for a
35243 list of the allowed formats. The default is @samp{x}.
35246 The trace state variables that have been collected at the current
35247 trace frame. For each trace state variable collected, the name and
35248 current value are returned.
35251 The set of memory ranges that have been collected at the current trace
35252 frame. Its content is a list of tuples. Each tuple represents a
35253 collected memory range and has the following fields:
35257 The start address of the memory range, as hexadecimal literal.
35260 The length of the memory range, as decimal literal.
35263 The contents of the memory block, in hex. This field is only present
35264 if the @code{--memory-contents} option is specified.
35270 @subsubheading @value{GDBN} Command
35272 There is no corresponding @value{GDBN} command.
35274 @subsubheading Example
35276 @subheading -trace-list-variables
35277 @findex -trace-list-variables
35279 @subsubheading Synopsis
35282 -trace-list-variables
35285 Return a table of all defined trace variables. Each element of the
35286 table has the following fields:
35290 The name of the trace variable. This field is always present.
35293 The initial value. This is a 64-bit signed integer. This
35294 field is always present.
35297 The value the trace variable has at the moment. This is a 64-bit
35298 signed integer. This field is absent iff current value is
35299 not defined, for example if the trace was never run, or is
35304 @subsubheading @value{GDBN} Command
35306 The corresponding @value{GDBN} command is @samp{tvariables}.
35308 @subsubheading Example
35312 -trace-list-variables
35313 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
35314 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
35315 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
35316 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
35317 body=[variable=@{name="$trace_timestamp",initial="0"@}
35318 variable=@{name="$foo",initial="10",current="15"@}]@}
35322 @subheading -trace-save
35323 @findex -trace-save
35325 @subsubheading Synopsis
35328 -trace-save [ -r ] [ -ctf ] @var{filename}
35331 Saves the collected trace data to @var{filename}. Without the
35332 @samp{-r} option, the data is downloaded from the target and saved
35333 in a local file. With the @samp{-r} option the target is asked
35334 to perform the save.
35336 By default, this command will save the trace in the tfile format. You can
35337 supply the optional @samp{-ctf} argument to save it the CTF format. See
35338 @ref{Trace Files} for more information about CTF.
35340 @subsubheading @value{GDBN} Command
35342 The corresponding @value{GDBN} command is @samp{tsave}.
35345 @subheading -trace-start
35346 @findex -trace-start
35348 @subsubheading Synopsis
35354 Starts a tracing experiment. The result of this command does not
35357 @subsubheading @value{GDBN} Command
35359 The corresponding @value{GDBN} command is @samp{tstart}.
35361 @subheading -trace-status
35362 @findex -trace-status
35364 @subsubheading Synopsis
35370 Obtains the status of a tracing experiment. The result may include
35371 the following fields:
35376 May have a value of either @samp{0}, when no tracing operations are
35377 supported, @samp{1}, when all tracing operations are supported, or
35378 @samp{file} when examining trace file. In the latter case, examining
35379 of trace frame is possible but new tracing experiement cannot be
35380 started. This field is always present.
35383 May have a value of either @samp{0} or @samp{1} depending on whether
35384 tracing experiement is in progress on target. This field is present
35385 if @samp{supported} field is not @samp{0}.
35388 Report the reason why the tracing was stopped last time. This field
35389 may be absent iff tracing was never stopped on target yet. The
35390 value of @samp{request} means the tracing was stopped as result of
35391 the @code{-trace-stop} command. The value of @samp{overflow} means
35392 the tracing buffer is full. The value of @samp{disconnection} means
35393 tracing was automatically stopped when @value{GDBN} has disconnected.
35394 The value of @samp{passcount} means tracing was stopped when a
35395 tracepoint was passed a maximal number of times for that tracepoint.
35396 This field is present if @samp{supported} field is not @samp{0}.
35398 @item stopping-tracepoint
35399 The number of tracepoint whose passcount as exceeded. This field is
35400 present iff the @samp{stop-reason} field has the value of
35404 @itemx frames-created
35405 The @samp{frames} field is a count of the total number of trace frames
35406 in the trace buffer, while @samp{frames-created} is the total created
35407 during the run, including ones that were discarded, such as when a
35408 circular trace buffer filled up. Both fields are optional.
35412 These fields tell the current size of the tracing buffer and the
35413 remaining space. These fields are optional.
35416 The value of the circular trace buffer flag. @code{1} means that the
35417 trace buffer is circular and old trace frames will be discarded if
35418 necessary to make room, @code{0} means that the trace buffer is linear
35422 The value of the disconnected tracing flag. @code{1} means that
35423 tracing will continue after @value{GDBN} disconnects, @code{0} means
35424 that the trace run will stop.
35427 The filename of the trace file being examined. This field is
35428 optional, and only present when examining a trace file.
35432 @subsubheading @value{GDBN} Command
35434 The corresponding @value{GDBN} command is @samp{tstatus}.
35436 @subheading -trace-stop
35437 @findex -trace-stop
35439 @subsubheading Synopsis
35445 Stops a tracing experiment. The result of this command has the same
35446 fields as @code{-trace-status}, except that the @samp{supported} and
35447 @samp{running} fields are not output.
35449 @subsubheading @value{GDBN} Command
35451 The corresponding @value{GDBN} command is @samp{tstop}.
35454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35455 @node GDB/MI Symbol Query
35456 @section @sc{gdb/mi} Symbol Query Commands
35460 @subheading The @code{-symbol-info-address} Command
35461 @findex -symbol-info-address
35463 @subsubheading Synopsis
35466 -symbol-info-address @var{symbol}
35469 Describe where @var{symbol} is stored.
35471 @subsubheading @value{GDBN} Command
35473 The corresponding @value{GDBN} command is @samp{info address}.
35475 @subsubheading Example
35479 @subheading The @code{-symbol-info-file} Command
35480 @findex -symbol-info-file
35482 @subsubheading Synopsis
35488 Show the file for the symbol.
35490 @subsubheading @value{GDBN} Command
35492 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35493 @samp{gdb_find_file}.
35495 @subsubheading Example
35499 @subheading The @code{-symbol-info-functions} Command
35500 @findex -symbol-info-functions
35501 @anchor{-symbol-info-functions}
35503 @subsubheading Synopsis
35506 -symbol-info-functions [--include-nondebug]
35507 [--type @var{type_regexp}]
35508 [--name @var{name_regexp}]
35509 [--max-results @var{limit}]
35513 Return a list containing the names and types for all global functions
35514 taken from the debug information. The functions are grouped by source
35515 file, and shown with the line number on which each function is
35518 The @code{--include-nondebug} option causes the output to include
35519 code symbols from the symbol table.
35521 The options @code{--type} and @code{--name} allow the symbols returned
35522 to be filtered based on either the name of the function, or the type
35523 signature of the function.
35525 The option @code{--max-results} restricts the command to return no
35526 more than @var{limit} results. If exactly @var{limit} results are
35527 returned then there might be additional results available if a higher
35530 @subsubheading @value{GDBN} Command
35532 The corresponding @value{GDBN} command is @samp{info functions}.
35534 @subsubheading Example
35538 -symbol-info-functions
35541 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35542 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35543 symbols=[@{line="36", name="f4", type="void (int *)",
35544 description="void f4(int *);"@},
35545 @{line="42", name="main", type="int ()",
35546 description="int main();"@},
35547 @{line="30", name="f1", type="my_int_t (int, int)",
35548 description="static my_int_t f1(int, int);"@}]@},
35549 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35550 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35551 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35552 description="float f2(another_float_t);"@},
35553 @{line="39", name="f3", type="int (another_int_t)",
35554 description="int f3(another_int_t);"@},
35555 @{line="27", name="f1", type="another_float_t (int)",
35556 description="static another_float_t f1(int);"@}]@}]@}
35560 -symbol-info-functions --name f1
35563 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35564 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35565 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35566 description="static my_int_t f1(int, int);"@}]@},
35567 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35568 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35569 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35570 description="static another_float_t f1(int);"@}]@}]@}
35574 -symbol-info-functions --type void
35577 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35578 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35579 symbols=[@{line="36", name="f4", type="void (int *)",
35580 description="void f4(int *);"@}]@}]@}
35584 -symbol-info-functions --include-nondebug
35587 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35588 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35589 symbols=[@{line="36", name="f4", type="void (int *)",
35590 description="void f4(int *);"@},
35591 @{line="42", name="main", type="int ()",
35592 description="int main();"@},
35593 @{line="30", name="f1", type="my_int_t (int, int)",
35594 description="static my_int_t f1(int, int);"@}]@},
35595 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35596 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35597 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35598 description="float f2(another_float_t);"@},
35599 @{line="39", name="f3", type="int (another_int_t)",
35600 description="int f3(another_int_t);"@},
35601 @{line="27", name="f1", type="another_float_t (int)",
35602 description="static another_float_t f1(int);"@}]@}],
35604 [@{address="0x0000000000400398",name="_init"@},
35605 @{address="0x00000000004003b0",name="_start"@},
35611 @subheading The @code{-symbol-info-module-functions} Command
35612 @findex -symbol-info-module-functions
35613 @anchor{-symbol-info-module-functions}
35615 @subsubheading Synopsis
35618 -symbol-info-module-functions [--module @var{module_regexp}]
35619 [--name @var{name_regexp}]
35620 [--type @var{type_regexp}]
35624 Return a list containing the names of all known functions within all
35625 know Fortran modules. The functions are grouped by source file and
35626 containing module, and shown with the line number on which each
35627 function is defined.
35629 The option @code{--module} only returns results for modules matching
35630 @var{module_regexp}. The option @code{--name} only returns functions
35631 whose name matches @var{name_regexp}, and @code{--type} only returns
35632 functions whose type matches @var{type_regexp}.
35634 @subsubheading @value{GDBN} Command
35636 The corresponding @value{GDBN} command is @samp{info module functions}.
35638 @subsubheading Example
35643 -symbol-info-module-functions
35646 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35647 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35648 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
35649 description="void mod1::check_all(void);"@}]@}]@},
35651 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35652 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35653 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35654 description="void mod2::check_var_i(void);"@}]@}]@},
35656 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35657 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35658 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35659 description="void mod3::check_all(void);"@},
35660 @{line="27",name="mod3::check_mod2",type="void (void)",
35661 description="void mod3::check_mod2(void);"@}]@}]@},
35662 @{module="modmany",
35663 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35664 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35665 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35666 description="void modmany::check_some(void);"@}]@}]@},
35668 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35669 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35670 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35671 description="void moduse::check_all(void);"@},
35672 @{line="49",name="moduse::check_var_x",type="void (void)",
35673 description="void moduse::check_var_x(void);"@}]@}]@}]
35677 @subheading The @code{-symbol-info-module-variables} Command
35678 @findex -symbol-info-module-variables
35679 @anchor{-symbol-info-module-variables}
35681 @subsubheading Synopsis
35684 -symbol-info-module-variables [--module @var{module_regexp}]
35685 [--name @var{name_regexp}]
35686 [--type @var{type_regexp}]
35690 Return a list containing the names of all known variables within all
35691 know Fortran modules. The variables are grouped by source file and
35692 containing module, and shown with the line number on which each
35693 variable is defined.
35695 The option @code{--module} only returns results for modules matching
35696 @var{module_regexp}. The option @code{--name} only returns variables
35697 whose name matches @var{name_regexp}, and @code{--type} only returns
35698 variables whose type matches @var{type_regexp}.
35700 @subsubheading @value{GDBN} Command
35702 The corresponding @value{GDBN} command is @samp{info module variables}.
35704 @subsubheading Example
35709 -symbol-info-module-variables
35712 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35713 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35714 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35715 description="integer(kind=4) mod1::var_const;"@},
35716 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35717 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35719 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35720 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35721 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35722 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35724 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35725 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35726 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35727 description="integer(kind=4) mod3::mod1;"@},
35728 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35729 description="integer(kind=4) mod3::mod2;"@},
35730 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35731 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35732 @{module="modmany",
35733 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35734 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35735 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35736 description="integer(kind=4) modmany::var_a;"@},
35737 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35738 description="integer(kind=4) modmany::var_b;"@},
35739 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35740 description="integer(kind=4) modmany::var_c;"@},
35741 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35742 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35744 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35745 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35746 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35747 description="integer(kind=4) moduse::var_x;"@},
35748 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35749 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35753 @subheading The @code{-symbol-info-modules} Command
35754 @findex -symbol-info-modules
35755 @anchor{-symbol-info-modules}
35757 @subsubheading Synopsis
35760 -symbol-info-modules [--name @var{name_regexp}]
35761 [--max-results @var{limit}]
35766 Return a list containing the names of all known Fortran modules. The
35767 modules are grouped by source file, and shown with the line number on
35768 which each modules is defined.
35770 The option @code{--name} allows the modules returned to be filtered
35771 based the name of the module.
35773 The option @code{--max-results} restricts the command to return no
35774 more than @var{limit} results. If exactly @var{limit} results are
35775 returned then there might be additional results available if a higher
35778 @subsubheading @value{GDBN} Command
35780 The corresponding @value{GDBN} command is @samp{info modules}.
35782 @subsubheading Example
35786 -symbol-info-modules
35789 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35790 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35791 symbols=[@{line="16",name="mod1"@},
35792 @{line="22",name="mod2"@}]@},
35793 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35794 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35795 symbols=[@{line="16",name="mod3"@},
35796 @{line="22",name="modmany"@},
35797 @{line="26",name="moduse"@}]@}]@}
35801 -symbol-info-modules --name mod[123]
35804 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35805 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35806 symbols=[@{line="16",name="mod1"@},
35807 @{line="22",name="mod2"@}]@},
35808 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35809 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35810 symbols=[@{line="16",name="mod3"@}]@}]@}
35814 @subheading The @code{-symbol-info-types} Command
35815 @findex -symbol-info-types
35816 @anchor{-symbol-info-types}
35818 @subsubheading Synopsis
35821 -symbol-info-types [--name @var{name_regexp}]
35822 [--max-results @var{limit}]
35827 Return a list of all defined types. The types are grouped by source
35828 file, and shown with the line number on which each user defined type
35829 is defined. Some base types are not defined in the source code but
35830 are added to the debug information by the compiler, for example
35831 @code{int}, @code{float}, etc.; these types do not have an associated
35834 The option @code{--name} allows the list of types returned to be
35837 The option @code{--max-results} restricts the command to return no
35838 more than @var{limit} results. If exactly @var{limit} results are
35839 returned then there might be additional results available if a higher
35842 @subsubheading @value{GDBN} Command
35844 The corresponding @value{GDBN} command is @samp{info types}.
35846 @subsubheading Example
35853 [@{filename="gdb.mi/mi-sym-info-1.c",
35854 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35855 symbols=[@{name="float"@},
35857 @{line="27",name="typedef int my_int_t;"@}]@},
35858 @{filename="gdb.mi/mi-sym-info-2.c",
35859 fullname="/project/gdb.mi/mi-sym-info-2.c",
35860 symbols=[@{line="24",name="typedef float another_float_t;"@},
35861 @{line="23",name="typedef int another_int_t;"@},
35863 @{name="int"@}]@}]@}
35867 -symbol-info-types --name _int_
35870 [@{filename="gdb.mi/mi-sym-info-1.c",
35871 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35872 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
35873 @{filename="gdb.mi/mi-sym-info-2.c",
35874 fullname="/project/gdb.mi/mi-sym-info-2.c",
35875 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
35879 @subheading The @code{-symbol-info-variables} Command
35880 @findex -symbol-info-variables
35881 @anchor{-symbol-info-variables}
35883 @subsubheading Synopsis
35886 -symbol-info-variables [--include-nondebug]
35887 [--type @var{type_regexp}]
35888 [--name @var{name_regexp}]
35889 [--max-results @var{limit}]
35894 Return a list containing the names and types for all global variables
35895 taken from the debug information. The variables are grouped by source
35896 file, and shown with the line number on which each variable is
35899 The @code{--include-nondebug} option causes the output to include
35900 data symbols from the symbol table.
35902 The options @code{--type} and @code{--name} allow the symbols returned
35903 to be filtered based on either the name of the variable, or the type
35906 The option @code{--max-results} restricts the command to return no
35907 more than @var{limit} results. If exactly @var{limit} results are
35908 returned then there might be additional results available if a higher
35911 @subsubheading @value{GDBN} Command
35913 The corresponding @value{GDBN} command is @samp{info variables}.
35915 @subsubheading Example
35919 -symbol-info-variables
35922 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35923 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35924 symbols=[@{line="25",name="global_f1",type="float",
35925 description="static float global_f1;"@},
35926 @{line="24",name="global_i1",type="int",
35927 description="static int global_i1;"@}]@},
35928 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35929 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35930 symbols=[@{line="21",name="global_f2",type="int",
35931 description="int global_f2;"@},
35932 @{line="20",name="global_i2",type="int",
35933 description="int global_i2;"@},
35934 @{line="19",name="global_f1",type="float",
35935 description="static float global_f1;"@},
35936 @{line="18",name="global_i1",type="int",
35937 description="static int global_i1;"@}]@}]@}
35941 -symbol-info-variables --name f1
35944 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35945 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35946 symbols=[@{line="25",name="global_f1",type="float",
35947 description="static float global_f1;"@}]@},
35948 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35949 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35950 symbols=[@{line="19",name="global_f1",type="float",
35951 description="static float global_f1;"@}]@}]@}
35955 -symbol-info-variables --type float
35958 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35959 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35960 symbols=[@{line="25",name="global_f1",type="float",
35961 description="static float global_f1;"@}]@},
35962 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35963 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35964 symbols=[@{line="19",name="global_f1",type="float",
35965 description="static float global_f1;"@}]@}]@}
35969 -symbol-info-variables --include-nondebug
35972 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35973 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35974 symbols=[@{line="25",name="global_f1",type="float",
35975 description="static float global_f1;"@},
35976 @{line="24",name="global_i1",type="int",
35977 description="static int global_i1;"@}]@},
35978 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35979 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35980 symbols=[@{line="21",name="global_f2",type="int",
35981 description="int global_f2;"@},
35982 @{line="20",name="global_i2",type="int",
35983 description="int global_i2;"@},
35984 @{line="19",name="global_f1",type="float",
35985 description="static float global_f1;"@},
35986 @{line="18",name="global_i1",type="int",
35987 description="static int global_i1;"@}]@}],
35989 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
35990 @{address="0x00000000004005d8",name="__dso_handle"@}
35997 @subheading The @code{-symbol-info-line} Command
35998 @findex -symbol-info-line
36000 @subsubheading Synopsis
36006 Show the core addresses of the code for a source line.
36008 @subsubheading @value{GDBN} Command
36010 The corresponding @value{GDBN} command is @samp{info line}.
36011 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
36013 @subsubheading Example
36017 @subheading The @code{-symbol-info-symbol} Command
36018 @findex -symbol-info-symbol
36020 @subsubheading Synopsis
36023 -symbol-info-symbol @var{addr}
36026 Describe what symbol is at location @var{addr}.
36028 @subsubheading @value{GDBN} Command
36030 The corresponding @value{GDBN} command is @samp{info symbol}.
36032 @subsubheading Example
36036 @subheading The @code{-symbol-list-functions} Command
36037 @findex -symbol-list-functions
36039 @subsubheading Synopsis
36042 -symbol-list-functions
36045 List the functions in the executable.
36047 @subsubheading @value{GDBN} Command
36049 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
36050 @samp{gdb_search} in @code{gdbtk}.
36052 @subsubheading Example
36057 @subheading The @code{-symbol-list-lines} Command
36058 @findex -symbol-list-lines
36060 @subsubheading Synopsis
36063 -symbol-list-lines @var{filename}
36066 Print the list of lines that contain code and their associated program
36067 addresses for the given source filename. The entries are sorted in
36068 ascending PC order.
36070 @subsubheading @value{GDBN} Command
36072 There is no corresponding @value{GDBN} command.
36074 @subsubheading Example
36077 -symbol-list-lines basics.c
36078 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
36084 @subheading The @code{-symbol-list-types} Command
36085 @findex -symbol-list-types
36087 @subsubheading Synopsis
36093 List all the type names.
36095 @subsubheading @value{GDBN} Command
36097 The corresponding commands are @samp{info types} in @value{GDBN},
36098 @samp{gdb_search} in @code{gdbtk}.
36100 @subsubheading Example
36104 @subheading The @code{-symbol-list-variables} Command
36105 @findex -symbol-list-variables
36107 @subsubheading Synopsis
36110 -symbol-list-variables
36113 List all the global and static variable names.
36115 @subsubheading @value{GDBN} Command
36117 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
36119 @subsubheading Example
36123 @subheading The @code{-symbol-locate} Command
36124 @findex -symbol-locate
36126 @subsubheading Synopsis
36132 @subsubheading @value{GDBN} Command
36134 @samp{gdb_loc} in @code{gdbtk}.
36136 @subsubheading Example
36140 @subheading The @code{-symbol-type} Command
36141 @findex -symbol-type
36143 @subsubheading Synopsis
36146 -symbol-type @var{variable}
36149 Show type of @var{variable}.
36151 @subsubheading @value{GDBN} Command
36153 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
36154 @samp{gdb_obj_variable}.
36156 @subsubheading Example
36161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36162 @node GDB/MI File Commands
36163 @section @sc{gdb/mi} File Commands
36165 This section describes the GDB/MI commands to specify executable file names
36166 and to read in and obtain symbol table information.
36168 @subheading The @code{-file-exec-and-symbols} Command
36169 @findex -file-exec-and-symbols
36171 @subsubheading Synopsis
36174 -file-exec-and-symbols @var{file}
36177 Specify the executable file to be debugged. This file is the one from
36178 which the symbol table is also read. If no file is specified, the
36179 command clears the executable and symbol information. If breakpoints
36180 are set when using this command with no arguments, @value{GDBN} will produce
36181 error messages. Otherwise, no output is produced, except a completion
36184 @subsubheading @value{GDBN} Command
36186 The corresponding @value{GDBN} command is @samp{file}.
36188 @subsubheading Example
36192 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36198 @subheading The @code{-file-exec-file} Command
36199 @findex -file-exec-file
36201 @subsubheading Synopsis
36204 -file-exec-file @var{file}
36207 Specify the executable file to be debugged. Unlike
36208 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
36209 from this file. If used without argument, @value{GDBN} clears the information
36210 about the executable file. No output is produced, except a completion
36213 @subsubheading @value{GDBN} Command
36215 The corresponding @value{GDBN} command is @samp{exec-file}.
36217 @subsubheading Example
36221 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36228 @subheading The @code{-file-list-exec-sections} Command
36229 @findex -file-list-exec-sections
36231 @subsubheading Synopsis
36234 -file-list-exec-sections
36237 List the sections of the current executable file.
36239 @subsubheading @value{GDBN} Command
36241 The @value{GDBN} command @samp{info file} shows, among the rest, the same
36242 information as this command. @code{gdbtk} has a corresponding command
36243 @samp{gdb_load_info}.
36245 @subsubheading Example
36250 @subheading The @code{-file-list-exec-source-file} Command
36251 @findex -file-list-exec-source-file
36253 @subsubheading Synopsis
36256 -file-list-exec-source-file
36259 List the line number, the current source file, and the absolute path
36260 to the current source file for the current executable. The macro
36261 information field has a value of @samp{1} or @samp{0} depending on
36262 whether or not the file includes preprocessor macro information.
36264 @subsubheading @value{GDBN} Command
36266 The @value{GDBN} equivalent is @samp{info source}
36268 @subsubheading Example
36272 123-file-list-exec-source-file
36273 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
36278 @subheading The @code{-file-list-exec-source-files} Command
36279 @kindex info sources
36280 @findex -file-list-exec-source-files
36282 @subsubheading Synopsis
36285 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
36286 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
36288 @r{[} @var{regexp} @r{]}
36291 This command returns information about the source files @value{GDBN}
36292 knows about, it will output both the filename and fullname (absolute
36293 file name) of a source file, though the fullname can be elided if this
36294 information is not known to @value{GDBN}.
36296 With no arguments this command returns a list of source files. Each
36297 source file is represented by a tuple with the fields; @var{file},
36298 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
36299 display name for the file, while @var{fullname} is the absolute name
36300 of the file. The @var{fullname} field can be elided if the absolute
36301 name of the source file can't be computed. The field
36302 @var{debug-fully-read} will be a string, either @code{true} or
36303 @code{false}. When @code{true}, this indicates the full debug
36304 information for the compilation unit describing this file has been
36305 read in. When @code{false}, the full debug information has not yet
36306 been read in. While reading in the full debug information it is
36307 possible that @value{GDBN} could become aware of additional source
36310 The optional @var{regexp} can be used to filter the list of source
36311 files returned. The @var{regexp} will be matched against the full
36312 source file name. The matching is case-sensitive, except on operating
36313 systems that have case-insensitive filesystem (e.g.,
36314 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
36315 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
36316 @var{regexp} starts with @samp{-}).
36318 If @code{--dirname} is provided, then @var{regexp} is matched only
36319 against the directory name of each source file. If @code{--basename}
36320 is provided, then @var{regexp} is matched against the basename of each
36321 source file. Only one of @code{--dirname} or @code{--basename} may be
36322 given, and if either is given then @var{regexp} is required.
36324 If @code{--group-by-objfile} is used then the format of the results is
36325 changed. The results will now be a list of tuples, with each tuple
36326 representing an object file (executable or shared library) loaded into
36327 @value{GDBN}. The fields of these tuples are; @var{filename},
36328 @var{debug-info}, and @var{sources}. The @var{filename} is the
36329 absolute name of the object file, @var{debug-info} is a string with
36330 one of the following values:
36334 This object file has no debug information.
36335 @item partially-read
36336 This object file has debug information, but it is not fully read in
36337 yet. When it is read in later, GDB might become aware of additional
36340 This object file has debug information, and this information is fully
36341 read into GDB. The list of source files is complete.
36344 The @var{sources} is a list or tuples, with each tuple describing a
36345 single source file with the same fields as described previously. The
36346 @var{sources} list can be empty for object files that have no debug
36349 @subsubheading @value{GDBN} Command
36351 The @value{GDBN} equivalent is @samp{info sources}.
36352 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
36354 @subsubheading Example
36357 -file-list-exec-source-files
36358 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
36359 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
36360 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
36362 -file-list-exec-source-files
36363 ^done,files=[@{file="test.c",
36364 fullname="/tmp/info-sources/test.c",
36365 debug-fully-read="true"@},
36366 @{file="/usr/include/stdc-predef.h",
36367 fullname="/usr/include/stdc-predef.h",
36368 debug-fully-read="true"@},
36370 fullname="/tmp/info-sources/header.h",
36371 debug-fully-read="true"@},
36373 fullname="/tmp/info-sources/helper.c",
36374 debug-fully-read="true"@}]
36376 -file-list-exec-source-files -- \\.c
36377 ^done,files=[@{file="test.c",
36378 fullname="/tmp/info-sources/test.c",
36379 debug-fully-read="true"@},
36381 fullname="/tmp/info-sources/helper.c",
36382 debug-fully-read="true"@}]
36384 -file-list-exec-source-files --group-by-objfile
36385 ^done,files=[@{filename="/tmp/info-sources/test.x",
36386 debug-info="fully-read",
36387 sources=[@{file="test.c",
36388 fullname="/tmp/info-sources/test.c",
36389 debug-fully-read="true"@},
36390 @{file="/usr/include/stdc-predef.h",
36391 fullname="/usr/include/stdc-predef.h",
36392 debug-fully-read="true"@},
36394 fullname="/tmp/info-sources/header.h",
36395 debug-fully-read="true"@}]@},
36396 @{filename="/lib64/ld-linux-x86-64.so.2",
36399 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36402 @{filename="/tmp/info-sources/libhelper.so",
36403 debug-info="fully-read",
36404 sources=[@{file="helper.c",
36405 fullname="/tmp/info-sources/helper.c",
36406 debug-fully-read="true"@},
36407 @{file="/usr/include/stdc-predef.h",
36408 fullname="/usr/include/stdc-predef.h",
36409 debug-fully-read="true"@},
36411 fullname="/tmp/info-sources/header.h",
36412 debug-fully-read="true"@}]@},
36413 @{filename="/lib64/libc.so.6",
36418 @subheading The @code{-file-list-shared-libraries} Command
36419 @findex -file-list-shared-libraries
36421 @subsubheading Synopsis
36424 -file-list-shared-libraries [ @var{regexp} ]
36427 List the shared libraries in the program.
36428 With a regular expression @var{regexp}, only those libraries whose
36429 names match @var{regexp} are listed.
36431 @subsubheading @value{GDBN} Command
36433 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36434 have a similar meaning to the @code{=library-loaded} notification.
36435 The @code{ranges} field specifies the multiple segments belonging to this
36436 library. Each range has the following fields:
36440 The address defining the inclusive lower bound of the segment.
36442 The address defining the exclusive upper bound of the segment.
36445 @subsubheading Example
36448 -file-list-exec-source-files
36449 ^done,shared-libraries=[
36450 @{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"@}]@},
36451 @{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"@}]@}]
36457 @subheading The @code{-file-list-symbol-files} Command
36458 @findex -file-list-symbol-files
36460 @subsubheading Synopsis
36463 -file-list-symbol-files
36468 @subsubheading @value{GDBN} Command
36470 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36472 @subsubheading Example
36477 @subheading The @code{-file-symbol-file} Command
36478 @findex -file-symbol-file
36480 @subsubheading Synopsis
36483 -file-symbol-file @var{file}
36486 Read symbol table info from the specified @var{file} argument. When
36487 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36488 produced, except for a completion notification.
36490 @subsubheading @value{GDBN} Command
36492 The corresponding @value{GDBN} command is @samp{symbol-file}.
36494 @subsubheading Example
36498 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36504 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36505 @node GDB/MI Memory Overlay Commands
36506 @section @sc{gdb/mi} Memory Overlay Commands
36508 The memory overlay commands are not implemented.
36510 @c @subheading -overlay-auto
36512 @c @subheading -overlay-list-mapping-state
36514 @c @subheading -overlay-list-overlays
36516 @c @subheading -overlay-map
36518 @c @subheading -overlay-off
36520 @c @subheading -overlay-on
36522 @c @subheading -overlay-unmap
36524 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36525 @node GDB/MI Signal Handling Commands
36526 @section @sc{gdb/mi} Signal Handling Commands
36528 Signal handling commands are not implemented.
36530 @c @subheading -signal-handle
36532 @c @subheading -signal-list-handle-actions
36534 @c @subheading -signal-list-signal-types
36538 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36539 @node GDB/MI Target Manipulation
36540 @section @sc{gdb/mi} Target Manipulation Commands
36543 @subheading The @code{-target-attach} Command
36544 @findex -target-attach
36546 @subsubheading Synopsis
36549 -target-attach @var{pid} | @var{gid} | @var{file}
36552 Attach to a process @var{pid} or a file @var{file} outside of
36553 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36554 group, the id previously returned by
36555 @samp{-list-thread-groups --available} must be used.
36557 @subsubheading @value{GDBN} Command
36559 The corresponding @value{GDBN} command is @samp{attach}.
36561 @subsubheading Example
36565 =thread-created,id="1"
36566 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36572 @subheading The @code{-target-compare-sections} Command
36573 @findex -target-compare-sections
36575 @subsubheading Synopsis
36578 -target-compare-sections [ @var{section} ]
36581 Compare data of section @var{section} on target to the exec file.
36582 Without the argument, all sections are compared.
36584 @subsubheading @value{GDBN} Command
36586 The @value{GDBN} equivalent is @samp{compare-sections}.
36588 @subsubheading Example
36593 @subheading The @code{-target-detach} Command
36594 @findex -target-detach
36596 @subsubheading Synopsis
36599 -target-detach [ @var{pid} | @var{gid} ]
36602 Detach from the remote target which normally resumes its execution.
36603 If either @var{pid} or @var{gid} is specified, detaches from either
36604 the specified process, or specified thread group. There's no output.
36606 @subsubheading @value{GDBN} Command
36608 The corresponding @value{GDBN} command is @samp{detach}.
36610 @subsubheading Example
36620 @subheading The @code{-target-disconnect} Command
36621 @findex -target-disconnect
36623 @subsubheading Synopsis
36629 Disconnect from the remote target. There's no output and the target is
36630 generally not resumed.
36632 @subsubheading @value{GDBN} Command
36634 The corresponding @value{GDBN} command is @samp{disconnect}.
36636 @subsubheading Example
36646 @subheading The @code{-target-download} Command
36647 @findex -target-download
36649 @subsubheading Synopsis
36655 Loads the executable onto the remote target.
36656 It prints out an update message every half second, which includes the fields:
36660 The name of the section.
36662 The size of what has been sent so far for that section.
36664 The size of the section.
36666 The total size of what was sent so far (the current and the previous sections).
36668 The size of the overall executable to download.
36672 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36673 @sc{gdb/mi} Output Syntax}).
36675 In addition, it prints the name and size of the sections, as they are
36676 downloaded. These messages include the following fields:
36680 The name of the section.
36682 The size of the section.
36684 The size of the overall executable to download.
36688 At the end, a summary is printed.
36690 @subsubheading @value{GDBN} Command
36692 The corresponding @value{GDBN} command is @samp{load}.
36694 @subsubheading Example
36696 Note: each status message appears on a single line. Here the messages
36697 have been broken down so that they can fit onto a page.
36702 +download,@{section=".text",section-size="6668",total-size="9880"@}
36703 +download,@{section=".text",section-sent="512",section-size="6668",
36704 total-sent="512",total-size="9880"@}
36705 +download,@{section=".text",section-sent="1024",section-size="6668",
36706 total-sent="1024",total-size="9880"@}
36707 +download,@{section=".text",section-sent="1536",section-size="6668",
36708 total-sent="1536",total-size="9880"@}
36709 +download,@{section=".text",section-sent="2048",section-size="6668",
36710 total-sent="2048",total-size="9880"@}
36711 +download,@{section=".text",section-sent="2560",section-size="6668",
36712 total-sent="2560",total-size="9880"@}
36713 +download,@{section=".text",section-sent="3072",section-size="6668",
36714 total-sent="3072",total-size="9880"@}
36715 +download,@{section=".text",section-sent="3584",section-size="6668",
36716 total-sent="3584",total-size="9880"@}
36717 +download,@{section=".text",section-sent="4096",section-size="6668",
36718 total-sent="4096",total-size="9880"@}
36719 +download,@{section=".text",section-sent="4608",section-size="6668",
36720 total-sent="4608",total-size="9880"@}
36721 +download,@{section=".text",section-sent="5120",section-size="6668",
36722 total-sent="5120",total-size="9880"@}
36723 +download,@{section=".text",section-sent="5632",section-size="6668",
36724 total-sent="5632",total-size="9880"@}
36725 +download,@{section=".text",section-sent="6144",section-size="6668",
36726 total-sent="6144",total-size="9880"@}
36727 +download,@{section=".text",section-sent="6656",section-size="6668",
36728 total-sent="6656",total-size="9880"@}
36729 +download,@{section=".init",section-size="28",total-size="9880"@}
36730 +download,@{section=".fini",section-size="28",total-size="9880"@}
36731 +download,@{section=".data",section-size="3156",total-size="9880"@}
36732 +download,@{section=".data",section-sent="512",section-size="3156",
36733 total-sent="7236",total-size="9880"@}
36734 +download,@{section=".data",section-sent="1024",section-size="3156",
36735 total-sent="7748",total-size="9880"@}
36736 +download,@{section=".data",section-sent="1536",section-size="3156",
36737 total-sent="8260",total-size="9880"@}
36738 +download,@{section=".data",section-sent="2048",section-size="3156",
36739 total-sent="8772",total-size="9880"@}
36740 +download,@{section=".data",section-sent="2560",section-size="3156",
36741 total-sent="9284",total-size="9880"@}
36742 +download,@{section=".data",section-sent="3072",section-size="3156",
36743 total-sent="9796",total-size="9880"@}
36744 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36751 @subheading The @code{-target-exec-status} Command
36752 @findex -target-exec-status
36754 @subsubheading Synopsis
36757 -target-exec-status
36760 Provide information on the state of the target (whether it is running or
36761 not, for instance).
36763 @subsubheading @value{GDBN} Command
36765 There's no equivalent @value{GDBN} command.
36767 @subsubheading Example
36771 @subheading The @code{-target-list-available-targets} Command
36772 @findex -target-list-available-targets
36774 @subsubheading Synopsis
36777 -target-list-available-targets
36780 List the possible targets to connect to.
36782 @subsubheading @value{GDBN} Command
36784 The corresponding @value{GDBN} command is @samp{help target}.
36786 @subsubheading Example
36790 @subheading The @code{-target-list-current-targets} Command
36791 @findex -target-list-current-targets
36793 @subsubheading Synopsis
36796 -target-list-current-targets
36799 Describe the current target.
36801 @subsubheading @value{GDBN} Command
36803 The corresponding information is printed by @samp{info file} (among
36806 @subsubheading Example
36810 @subheading The @code{-target-list-parameters} Command
36811 @findex -target-list-parameters
36813 @subsubheading Synopsis
36816 -target-list-parameters
36822 @subsubheading @value{GDBN} Command
36826 @subsubheading Example
36829 @subheading The @code{-target-flash-erase} Command
36830 @findex -target-flash-erase
36832 @subsubheading Synopsis
36835 -target-flash-erase
36838 Erases all known flash memory regions on the target.
36840 The corresponding @value{GDBN} command is @samp{flash-erase}.
36842 The output is a list of flash regions that have been erased, with starting
36843 addresses and memory region sizes.
36847 -target-flash-erase
36848 ^done,erased-regions=@{address="0x0",size="0x40000"@}
36852 @subheading The @code{-target-select} Command
36853 @findex -target-select
36855 @subsubheading Synopsis
36858 -target-select @var{type} @var{parameters @dots{}}
36861 Connect @value{GDBN} to the remote target. This command takes two args:
36865 The type of target, for instance @samp{remote}, etc.
36866 @item @var{parameters}
36867 Device names, host names and the like. @xref{Target Commands, ,
36868 Commands for Managing Targets}, for more details.
36871 The output is a connection notification, followed by the address at
36872 which the target program is, in the following form:
36875 ^connected,addr="@var{address}",func="@var{function name}",
36876 args=[@var{arg list}]
36879 @subsubheading @value{GDBN} Command
36881 The corresponding @value{GDBN} command is @samp{target}.
36883 @subsubheading Example
36887 -target-select remote /dev/ttya
36888 ^connected,addr="0xfe00a300",func="??",args=[]
36892 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36893 @node GDB/MI File Transfer Commands
36894 @section @sc{gdb/mi} File Transfer Commands
36897 @subheading The @code{-target-file-put} Command
36898 @findex -target-file-put
36900 @subsubheading Synopsis
36903 -target-file-put @var{hostfile} @var{targetfile}
36906 Copy file @var{hostfile} from the host system (the machine running
36907 @value{GDBN}) to @var{targetfile} on the target system.
36909 @subsubheading @value{GDBN} Command
36911 The corresponding @value{GDBN} command is @samp{remote put}.
36913 @subsubheading Example
36917 -target-file-put localfile remotefile
36923 @subheading The @code{-target-file-get} Command
36924 @findex -target-file-get
36926 @subsubheading Synopsis
36929 -target-file-get @var{targetfile} @var{hostfile}
36932 Copy file @var{targetfile} from the target system to @var{hostfile}
36933 on the host system.
36935 @subsubheading @value{GDBN} Command
36937 The corresponding @value{GDBN} command is @samp{remote get}.
36939 @subsubheading Example
36943 -target-file-get remotefile localfile
36949 @subheading The @code{-target-file-delete} Command
36950 @findex -target-file-delete
36952 @subsubheading Synopsis
36955 -target-file-delete @var{targetfile}
36958 Delete @var{targetfile} from the target system.
36960 @subsubheading @value{GDBN} Command
36962 The corresponding @value{GDBN} command is @samp{remote delete}.
36964 @subsubheading Example
36968 -target-file-delete remotefile
36974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36975 @node GDB/MI Ada Exceptions Commands
36976 @section Ada Exceptions @sc{gdb/mi} Commands
36978 @subheading The @code{-info-ada-exceptions} Command
36979 @findex -info-ada-exceptions
36981 @subsubheading Synopsis
36984 -info-ada-exceptions [ @var{regexp}]
36987 List all Ada exceptions defined within the program being debugged.
36988 With a regular expression @var{regexp}, only those exceptions whose
36989 names match @var{regexp} are listed.
36991 @subsubheading @value{GDBN} Command
36993 The corresponding @value{GDBN} command is @samp{info exceptions}.
36995 @subsubheading Result
36997 The result is a table of Ada exceptions. The following columns are
36998 defined for each exception:
37002 The name of the exception.
37005 The address of the exception.
37009 @subsubheading Example
37012 -info-ada-exceptions aint
37013 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
37014 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
37015 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
37016 body=[@{name="constraint_error",address="0x0000000000613da0"@},
37017 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
37020 @subheading Catching Ada Exceptions
37022 The commands describing how to ask @value{GDBN} to stop when a program
37023 raises an exception are described at @ref{Ada Exception GDB/MI
37024 Catchpoint Commands}.
37027 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37028 @node GDB/MI Support Commands
37029 @section @sc{gdb/mi} Support Commands
37031 Since new commands and features get regularly added to @sc{gdb/mi},
37032 some commands are available to help front-ends query the debugger
37033 about support for these capabilities. Similarly, it is also possible
37034 to query @value{GDBN} about target support of certain features.
37036 @subheading The @code{-info-gdb-mi-command} Command
37037 @cindex @code{-info-gdb-mi-command}
37038 @findex -info-gdb-mi-command
37040 @subsubheading Synopsis
37043 -info-gdb-mi-command @var{cmd_name}
37046 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
37048 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
37049 is technically not part of the command name (@pxref{GDB/MI Input
37050 Syntax}), and thus should be omitted in @var{cmd_name}. However,
37051 for ease of use, this command also accepts the form with the leading
37054 @subsubheading @value{GDBN} Command
37056 There is no corresponding @value{GDBN} command.
37058 @subsubheading Result
37060 The result is a tuple. There is currently only one field:
37064 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
37065 @code{"false"} otherwise.
37069 @subsubheading Example
37071 Here is an example where the @sc{gdb/mi} command does not exist:
37074 -info-gdb-mi-command unsupported-command
37075 ^done,command=@{exists="false"@}
37079 And here is an example where the @sc{gdb/mi} command is known
37083 -info-gdb-mi-command symbol-list-lines
37084 ^done,command=@{exists="true"@}
37087 @subheading The @code{-list-features} Command
37088 @findex -list-features
37089 @cindex supported @sc{gdb/mi} features, list
37091 Returns a list of particular features of the MI protocol that
37092 this version of gdb implements. A feature can be a command,
37093 or a new field in an output of some command, or even an
37094 important bugfix. While a frontend can sometimes detect presence
37095 of a feature at runtime, it is easier to perform detection at debugger
37098 The command returns a list of strings, with each string naming an
37099 available feature. Each returned string is just a name, it does not
37100 have any internal structure. The list of possible feature names
37106 (gdb) -list-features
37107 ^done,result=["feature1","feature2"]
37110 The current list of features is:
37113 @item frozen-varobjs
37114 Indicates support for the @code{-var-set-frozen} command, as well
37115 as possible presence of the @code{frozen} field in the output
37116 of @code{-varobj-create}.
37117 @item pending-breakpoints
37118 Indicates support for the @option{-f} option to the @code{-break-insert}
37121 Indicates Python scripting support, Python-based
37122 pretty-printing commands, and possible presence of the
37123 @samp{display_hint} field in the output of @code{-var-list-children}
37125 Indicates support for the @code{-thread-info} command.
37126 @item data-read-memory-bytes
37127 Indicates support for the @code{-data-read-memory-bytes} and the
37128 @code{-data-write-memory-bytes} commands.
37129 @item breakpoint-notifications
37130 Indicates that changes to breakpoints and breakpoints created via the
37131 CLI will be announced via async records.
37132 @item ada-task-info
37133 Indicates support for the @code{-ada-task-info} command.
37134 @item language-option
37135 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
37136 option (@pxref{Context management}).
37137 @item info-gdb-mi-command
37138 Indicates support for the @code{-info-gdb-mi-command} command.
37139 @item undefined-command-error-code
37140 Indicates support for the "undefined-command" error code in error result
37141 records, produced when trying to execute an undefined @sc{gdb/mi} command
37142 (@pxref{GDB/MI Result Records}).
37143 @item exec-run-start-option
37144 Indicates that the @code{-exec-run} command supports the @option{--start}
37145 option (@pxref{GDB/MI Program Execution}).
37146 @item data-disassemble-a-option
37147 Indicates that the @code{-data-disassemble} command supports the @option{-a}
37148 option (@pxref{GDB/MI Data Manipulation}).
37151 @subheading The @code{-list-target-features} Command
37152 @findex -list-target-features
37154 Returns a list of particular features that are supported by the
37155 target. Those features affect the permitted MI commands, but
37156 unlike the features reported by the @code{-list-features} command, the
37157 features depend on which target GDB is using at the moment. Whenever
37158 a target can change, due to commands such as @code{-target-select},
37159 @code{-target-attach} or @code{-exec-run}, the list of target features
37160 may change, and the frontend should obtain it again.
37164 (gdb) -list-target-features
37165 ^done,result=["async"]
37168 The current list of features is:
37172 Indicates that the target is capable of asynchronous command
37173 execution, which means that @value{GDBN} will accept further commands
37174 while the target is running.
37177 Indicates that the target is capable of reverse execution.
37178 @xref{Reverse Execution}, for more information.
37182 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37183 @node GDB/MI Miscellaneous Commands
37184 @section Miscellaneous @sc{gdb/mi} Commands
37186 @c @subheading -gdb-complete
37188 @subheading The @code{-gdb-exit} Command
37191 @subsubheading Synopsis
37197 Exit @value{GDBN} immediately.
37199 @subsubheading @value{GDBN} Command
37201 Approximately corresponds to @samp{quit}.
37203 @subsubheading Example
37213 @subheading The @code{-exec-abort} Command
37214 @findex -exec-abort
37216 @subsubheading Synopsis
37222 Kill the inferior running program.
37224 @subsubheading @value{GDBN} Command
37226 The corresponding @value{GDBN} command is @samp{kill}.
37228 @subsubheading Example
37233 @subheading The @code{-gdb-set} Command
37236 @subsubheading Synopsis
37242 Set an internal @value{GDBN} variable.
37243 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
37245 @subsubheading @value{GDBN} Command
37247 The corresponding @value{GDBN} command is @samp{set}.
37249 @subsubheading Example
37259 @subheading The @code{-gdb-show} Command
37262 @subsubheading Synopsis
37268 Show the current value of a @value{GDBN} variable.
37270 @subsubheading @value{GDBN} Command
37272 The corresponding @value{GDBN} command is @samp{show}.
37274 @subsubheading Example
37283 @c @subheading -gdb-source
37286 @subheading The @code{-gdb-version} Command
37287 @findex -gdb-version
37289 @subsubheading Synopsis
37295 Show version information for @value{GDBN}. Used mostly in testing.
37297 @subsubheading @value{GDBN} Command
37299 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
37300 default shows this information when you start an interactive session.
37302 @subsubheading Example
37304 @c This example modifies the actual output from GDB to avoid overfull
37310 ~Copyright 2000 Free Software Foundation, Inc.
37311 ~GDB is free software, covered by the GNU General Public License, and
37312 ~you are welcome to change it and/or distribute copies of it under
37313 ~ certain conditions.
37314 ~Type "show copying" to see the conditions.
37315 ~There is absolutely no warranty for GDB. Type "show warranty" for
37317 ~This GDB was configured as
37318 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
37323 @subheading The @code{-list-thread-groups} Command
37324 @findex -list-thread-groups
37326 @subheading Synopsis
37329 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
37332 Lists thread groups (@pxref{Thread groups}). When a single thread
37333 group is passed as the argument, lists the children of that group.
37334 When several thread group are passed, lists information about those
37335 thread groups. Without any parameters, lists information about all
37336 top-level thread groups.
37338 Normally, thread groups that are being debugged are reported.
37339 With the @samp{--available} option, @value{GDBN} reports thread groups
37340 available on the target.
37342 The output of this command may have either a @samp{threads} result or
37343 a @samp{groups} result. The @samp{thread} result has a list of tuples
37344 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
37345 Information}). The @samp{groups} result has a list of tuples as value,
37346 each tuple describing a thread group. If top-level groups are
37347 requested (that is, no parameter is passed), or when several groups
37348 are passed, the output always has a @samp{groups} result. The format
37349 of the @samp{group} result is described below.
37351 To reduce the number of roundtrips it's possible to list thread groups
37352 together with their children, by passing the @samp{--recurse} option
37353 and the recursion depth. Presently, only recursion depth of 1 is
37354 permitted. If this option is present, then every reported thread group
37355 will also include its children, either as @samp{group} or
37356 @samp{threads} field.
37358 In general, any combination of option and parameters is permitted, with
37359 the following caveats:
37363 When a single thread group is passed, the output will typically
37364 be the @samp{threads} result. Because threads may not contain
37365 anything, the @samp{recurse} option will be ignored.
37368 When the @samp{--available} option is passed, limited information may
37369 be available. In particular, the list of threads of a process might
37370 be inaccessible. Further, specifying specific thread groups might
37371 not give any performance advantage over listing all thread groups.
37372 The frontend should assume that @samp{-list-thread-groups --available}
37373 is always an expensive operation and cache the results.
37377 The @samp{groups} result is a list of tuples, where each tuple may
37378 have the following fields:
37382 Identifier of the thread group. This field is always present.
37383 The identifier is an opaque string; frontends should not try to
37384 convert it to an integer, even though it might look like one.
37387 The type of the thread group. At present, only @samp{process} is a
37391 The target-specific process identifier. This field is only present
37392 for thread groups of type @samp{process} and only if the process exists.
37395 The exit code of this group's last exited thread, formatted in octal.
37396 This field is only present for thread groups of type @samp{process} and
37397 only if the process is not running.
37400 The number of children this thread group has. This field may be
37401 absent for an available thread group.
37404 This field has a list of tuples as value, each tuple describing a
37405 thread. It may be present if the @samp{--recurse} option is
37406 specified, and it's actually possible to obtain the threads.
37409 This field is a list of integers, each identifying a core that one
37410 thread of the group is running on. This field may be absent if
37411 such information is not available.
37414 The name of the executable file that corresponds to this thread group.
37415 The field is only present for thread groups of type @samp{process},
37416 and only if there is a corresponding executable file.
37420 @subheading Example
37424 -list-thread-groups
37425 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37426 -list-thread-groups 17
37427 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37428 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37429 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37430 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37431 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37432 -list-thread-groups --available
37433 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37434 -list-thread-groups --available --recurse 1
37435 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37436 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37437 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37438 -list-thread-groups --available --recurse 1 17 18
37439 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37440 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37441 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37444 @subheading The @code{-info-os} Command
37447 @subsubheading Synopsis
37450 -info-os [ @var{type} ]
37453 If no argument is supplied, the command returns a table of available
37454 operating-system-specific information types. If one of these types is
37455 supplied as an argument @var{type}, then the command returns a table
37456 of data of that type.
37458 The types of information available depend on the target operating
37461 @subsubheading @value{GDBN} Command
37463 The corresponding @value{GDBN} command is @samp{info os}.
37465 @subsubheading Example
37467 When run on a @sc{gnu}/Linux system, the output will look something
37473 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37474 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37475 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37476 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37477 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37479 item=@{col0="files",col1="Listing of all file descriptors",
37480 col2="File descriptors"@},
37481 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37482 col2="Kernel modules"@},
37483 item=@{col0="msg",col1="Listing of all message queues",
37484 col2="Message queues"@},
37485 item=@{col0="processes",col1="Listing of all processes",
37486 col2="Processes"@},
37487 item=@{col0="procgroups",col1="Listing of all process groups",
37488 col2="Process groups"@},
37489 item=@{col0="semaphores",col1="Listing of all semaphores",
37490 col2="Semaphores"@},
37491 item=@{col0="shm",col1="Listing of all shared-memory regions",
37492 col2="Shared-memory regions"@},
37493 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37495 item=@{col0="threads",col1="Listing of all threads",
37499 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37500 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37501 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37502 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37503 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37504 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37505 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37506 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37508 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37509 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37513 (Note that the MI output here includes a @code{"Title"} column that
37514 does not appear in command-line @code{info os}; this column is useful
37515 for MI clients that want to enumerate the types of data, such as in a
37516 popup menu, but is needless clutter on the command line, and
37517 @code{info os} omits it.)
37519 @subheading The @code{-add-inferior} Command
37520 @findex -add-inferior
37522 @subheading Synopsis
37525 -add-inferior [ --no-connection ]
37528 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37529 inferior is not associated with any executable. Such association may
37530 be established with the @samp{-file-exec-and-symbols} command
37531 (@pxref{GDB/MI File Commands}).
37533 By default, the new inferior begins connected to the same target
37534 connection as the current inferior. For example, if the current
37535 inferior was connected to @code{gdbserver} with @code{target remote},
37536 then the new inferior will be connected to the same @code{gdbserver}
37537 instance. The @samp{--no-connection} option starts the new inferior
37538 with no connection yet. You can then for example use the
37539 @code{-target-select remote} command to connect to some other
37540 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
37543 The command response always has a field, @var{inferior}, whose value
37544 is the identifier of the thread group corresponding to the new
37547 An additional section field, @var{connection}, is optional. This
37548 field will only exist if the new inferior has a target connection. If
37549 this field exists, then its value will be a tuple containing the
37554 The number of the connection used for the new inferior.
37557 The name of the connection type used for the new inferior.
37560 @subheading @value{GDBN} Command
37562 The corresponding @value{GDBN} command is @samp{add-inferior}
37563 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
37565 @subheading Example
37570 ^done,inferior="i3"
37573 @subheading The @code{-interpreter-exec} Command
37574 @findex -interpreter-exec
37576 @subheading Synopsis
37579 -interpreter-exec @var{interpreter} @var{command}
37581 @anchor{-interpreter-exec}
37583 Execute the specified @var{command} in the given @var{interpreter}.
37585 @subheading @value{GDBN} Command
37587 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37589 @subheading Example
37593 -interpreter-exec console "break main"
37594 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37595 &"During symbol reading, bad structure-type format.\n"
37596 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37601 @subheading The @code{-inferior-tty-set} Command
37602 @findex -inferior-tty-set
37604 @subheading Synopsis
37607 -inferior-tty-set /dev/pts/1
37610 Set terminal for future runs of the program being debugged.
37612 @subheading @value{GDBN} Command
37614 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37616 @subheading Example
37620 -inferior-tty-set /dev/pts/1
37625 @subheading The @code{-inferior-tty-show} Command
37626 @findex -inferior-tty-show
37628 @subheading Synopsis
37634 Show terminal for future runs of program being debugged.
37636 @subheading @value{GDBN} Command
37638 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
37640 @subheading Example
37644 -inferior-tty-set /dev/pts/1
37648 ^done,inferior_tty_terminal="/dev/pts/1"
37652 @subheading The @code{-enable-timings} Command
37653 @findex -enable-timings
37655 @subheading Synopsis
37658 -enable-timings [yes | no]
37661 Toggle the printing of the wallclock, user and system times for an MI
37662 command as a field in its output. This command is to help frontend
37663 developers optimize the performance of their code. No argument is
37664 equivalent to @samp{yes}.
37666 @subheading @value{GDBN} Command
37670 @subheading Example
37678 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
37679 addr="0x080484ed",func="main",file="myprog.c",
37680 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
37682 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37690 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37691 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37692 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37693 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37697 @subheading The @code{-complete} Command
37700 @subheading Synopsis
37703 -complete @var{command}
37706 Show a list of completions for partially typed CLI @var{command}.
37708 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37709 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37710 because @value{GDBN} is used remotely via a SSH connection.
37714 The result consists of two or three fields:
37718 This field contains the completed @var{command}. If @var{command}
37719 has no known completions, this field is omitted.
37722 This field contains a (possibly empty) array of matches. It is always present.
37724 @item max_completions_reached
37725 This field contains @code{1} if number of known completions is above
37726 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37727 @code{0}. It is always present.
37731 @subheading @value{GDBN} Command
37733 The corresponding @value{GDBN} command is @samp{complete}.
37735 @subheading Example
37740 ^done,completion="break",
37741 matches=["break","break-range"],
37742 max_completions_reached="0"
37745 ^done,completion="b ma",
37746 matches=["b madvise","b main"],max_completions_reached="0"
37748 -complete "b push_b"
37749 ^done,completion="b push_back(",
37751 "b A::push_back(void*)",
37752 "b std::string::push_back(char)",
37753 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37754 max_completions_reached="0"
37756 -complete "nonexist"
37757 ^done,matches=[],max_completions_reached="0"
37763 @chapter @value{GDBN} Annotations
37765 This chapter describes annotations in @value{GDBN}. Annotations were
37766 designed to interface @value{GDBN} to graphical user interfaces or other
37767 similar programs which want to interact with @value{GDBN} at a
37768 relatively high level.
37770 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37774 This is Edition @value{EDITION}, @value{DATE}.
37778 * Annotations Overview:: What annotations are; the general syntax.
37779 * Server Prefix:: Issuing a command without affecting user state.
37780 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37781 * Errors:: Annotations for error messages.
37782 * Invalidation:: Some annotations describe things now invalid.
37783 * Annotations for Running::
37784 Whether the program is running, how it stopped, etc.
37785 * Source Annotations:: Annotations describing source code.
37788 @node Annotations Overview
37789 @section What is an Annotation?
37790 @cindex annotations
37792 Annotations start with a newline character, two @samp{control-z}
37793 characters, and the name of the annotation. If there is no additional
37794 information associated with this annotation, the name of the annotation
37795 is followed immediately by a newline. If there is additional
37796 information, the name of the annotation is followed by a space, the
37797 additional information, and a newline. The additional information
37798 cannot contain newline characters.
37800 Any output not beginning with a newline and two @samp{control-z}
37801 characters denotes literal output from @value{GDBN}. Currently there is
37802 no need for @value{GDBN} to output a newline followed by two
37803 @samp{control-z} characters, but if there was such a need, the
37804 annotations could be extended with an @samp{escape} annotation which
37805 means those three characters as output.
37807 The annotation @var{level}, which is specified using the
37808 @option{--annotate} command line option (@pxref{Mode Options}), controls
37809 how much information @value{GDBN} prints together with its prompt,
37810 values of expressions, source lines, and other types of output. Level 0
37811 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37812 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37813 for programs that control @value{GDBN}, and level 2 annotations have
37814 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37815 Interface, annotate, GDB's Obsolete Annotations}).
37818 @kindex set annotate
37819 @item set annotate @var{level}
37820 The @value{GDBN} command @code{set annotate} sets the level of
37821 annotations to the specified @var{level}.
37823 @item show annotate
37824 @kindex show annotate
37825 Show the current annotation level.
37828 This chapter describes level 3 annotations.
37830 A simple example of starting up @value{GDBN} with annotations is:
37833 $ @kbd{gdb --annotate=3}
37835 Copyright 2003 Free Software Foundation, Inc.
37836 GDB is free software, covered by the GNU General Public License,
37837 and you are welcome to change it and/or distribute copies of it
37838 under certain conditions.
37839 Type "show copying" to see the conditions.
37840 There is absolutely no warranty for GDB. Type "show warranty"
37842 This GDB was configured as "i386-pc-linux-gnu"
37853 Here @samp{quit} is input to @value{GDBN}; the rest is output from
37854 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
37855 denotes a @samp{control-z} character) are annotations; the rest is
37856 output from @value{GDBN}.
37858 @node Server Prefix
37859 @section The Server Prefix
37860 @cindex server prefix
37862 If you prefix a command with @samp{server } then it will not affect
37863 the command history, nor will it affect @value{GDBN}'s notion of which
37864 command to repeat if @key{RET} is pressed on a line by itself. This
37865 means that commands can be run behind a user's back by a front-end in
37866 a transparent manner.
37868 The @code{server } prefix does not affect the recording of values into
37869 the value history; to print a value without recording it into the
37870 value history, use the @code{output} command instead of the
37871 @code{print} command.
37873 Using this prefix also disables confirmation requests
37874 (@pxref{confirmation requests}).
37877 @section Annotation for @value{GDBN} Input
37879 @cindex annotations for prompts
37880 When @value{GDBN} prompts for input, it annotates this fact so it is possible
37881 to know when to send output, when the output from a given command is
37884 Different kinds of input each have a different @dfn{input type}. Each
37885 input type has three annotations: a @code{pre-} annotation, which
37886 denotes the beginning of any prompt which is being output, a plain
37887 annotation, which denotes the end of the prompt, and then a @code{post-}
37888 annotation which denotes the end of any echo which may (or may not) be
37889 associated with the input. For example, the @code{prompt} input type
37890 features the following annotations:
37898 The input types are
37901 @findex pre-prompt annotation
37902 @findex prompt annotation
37903 @findex post-prompt annotation
37905 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
37907 @findex pre-commands annotation
37908 @findex commands annotation
37909 @findex post-commands annotation
37911 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
37912 command. The annotations are repeated for each command which is input.
37914 @findex pre-overload-choice annotation
37915 @findex overload-choice annotation
37916 @findex post-overload-choice annotation
37917 @item overload-choice
37918 When @value{GDBN} wants the user to select between various overloaded functions.
37920 @findex pre-query annotation
37921 @findex query annotation
37922 @findex post-query annotation
37924 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
37926 @findex pre-prompt-for-continue annotation
37927 @findex prompt-for-continue annotation
37928 @findex post-prompt-for-continue annotation
37929 @item prompt-for-continue
37930 When @value{GDBN} is asking the user to press return to continue. Note: Don't
37931 expect this to work well; instead use @code{set height 0} to disable
37932 prompting. This is because the counting of lines is buggy in the
37933 presence of annotations.
37938 @cindex annotations for errors, warnings and interrupts
37940 @findex quit annotation
37945 This annotation occurs right before @value{GDBN} responds to an interrupt.
37947 @findex error annotation
37952 This annotation occurs right before @value{GDBN} responds to an error.
37954 Quit and error annotations indicate that any annotations which @value{GDBN} was
37955 in the middle of may end abruptly. For example, if a
37956 @code{value-history-begin} annotation is followed by a @code{error}, one
37957 cannot expect to receive the matching @code{value-history-end}. One
37958 cannot expect not to receive it either, however; an error annotation
37959 does not necessarily mean that @value{GDBN} is immediately returning all the way
37962 @findex error-begin annotation
37963 A quit or error annotation may be preceded by
37969 Any output between that and the quit or error annotation is the error
37972 Warning messages are not yet annotated.
37973 @c If we want to change that, need to fix warning(), type_error(),
37974 @c range_error(), and possibly other places.
37977 @section Invalidation Notices
37979 @cindex annotations for invalidation messages
37980 The following annotations say that certain pieces of state may have
37984 @findex frames-invalid annotation
37985 @item ^Z^Zframes-invalid
37987 The frames (for example, output from the @code{backtrace} command) may
37990 @findex breakpoints-invalid annotation
37991 @item ^Z^Zbreakpoints-invalid
37993 The breakpoints may have changed. For example, the user just added or
37994 deleted a breakpoint.
37997 @node Annotations for Running
37998 @section Running the Program
37999 @cindex annotations for running programs
38001 @findex starting annotation
38002 @findex stopping annotation
38003 When the program starts executing due to a @value{GDBN} command such as
38004 @code{step} or @code{continue},
38010 is output. When the program stops,
38016 is output. Before the @code{stopped} annotation, a variety of
38017 annotations describe how the program stopped.
38020 @findex exited annotation
38021 @item ^Z^Zexited @var{exit-status}
38022 The program exited, and @var{exit-status} is the exit status (zero for
38023 successful exit, otherwise nonzero).
38025 @findex signalled annotation
38026 @findex signal-name annotation
38027 @findex signal-name-end annotation
38028 @findex signal-string annotation
38029 @findex signal-string-end annotation
38030 @item ^Z^Zsignalled
38031 The program exited with a signal. After the @code{^Z^Zsignalled}, the
38032 annotation continues:
38038 ^Z^Zsignal-name-end
38042 ^Z^Zsignal-string-end
38047 where @var{name} is the name of the signal, such as @code{SIGILL} or
38048 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
38049 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
38050 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
38051 user's benefit and have no particular format.
38053 @findex signal annotation
38055 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
38056 just saying that the program received the signal, not that it was
38057 terminated with it.
38059 @findex breakpoint annotation
38060 @item ^Z^Zbreakpoint @var{number}
38061 The program hit breakpoint number @var{number}.
38063 @findex watchpoint annotation
38064 @item ^Z^Zwatchpoint @var{number}
38065 The program hit watchpoint number @var{number}.
38068 @node Source Annotations
38069 @section Displaying Source
38070 @cindex annotations for source display
38072 @findex source annotation
38073 The following annotation is used instead of displaying source code:
38076 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
38079 where @var{filename} is an absolute file name indicating which source
38080 file, @var{line} is the line number within that file (where 1 is the
38081 first line in the file), @var{character} is the character position
38082 within the file (where 0 is the first character in the file) (for most
38083 debug formats this will necessarily point to the beginning of a line),
38084 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
38085 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
38086 @var{addr} is the address in the target program associated with the
38087 source which is being displayed. The @var{addr} is in the form @samp{0x}
38088 followed by one or more lowercase hex digits (note that this does not
38089 depend on the language).
38091 @node JIT Interface
38092 @chapter JIT Compilation Interface
38093 @cindex just-in-time compilation
38094 @cindex JIT compilation interface
38096 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
38097 interface. A JIT compiler is a program or library that generates native
38098 executable code at runtime and executes it, usually in order to achieve good
38099 performance while maintaining platform independence.
38101 Programs that use JIT compilation are normally difficult to debug because
38102 portions of their code are generated at runtime, instead of being loaded from
38103 object files, which is where @value{GDBN} normally finds the program's symbols
38104 and debug information. In order to debug programs that use JIT compilation,
38105 @value{GDBN} has an interface that allows the program to register in-memory
38106 symbol files with @value{GDBN} at runtime.
38108 If you are using @value{GDBN} to debug a program that uses this interface, then
38109 it should work transparently so long as you have not stripped the binary. If
38110 you are developing a JIT compiler, then the interface is documented in the rest
38111 of this chapter. At this time, the only known client of this interface is the
38114 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
38115 JIT compiler communicates with @value{GDBN} by writing data into a global
38116 variable and calling a function at a well-known symbol. When @value{GDBN}
38117 attaches, it reads a linked list of symbol files from the global variable to
38118 find existing code, and puts a breakpoint in the function so that it can find
38119 out about additional code.
38122 * Declarations:: Relevant C struct declarations
38123 * Registering Code:: Steps to register code
38124 * Unregistering Code:: Steps to unregister code
38125 * Custom Debug Info:: Emit debug information in a custom format
38129 @section JIT Declarations
38131 These are the relevant struct declarations that a C program should include to
38132 implement the interface:
38142 struct jit_code_entry
38144 struct jit_code_entry *next_entry;
38145 struct jit_code_entry *prev_entry;
38146 const char *symfile_addr;
38147 uint64_t symfile_size;
38150 struct jit_descriptor
38153 /* This type should be jit_actions_t, but we use uint32_t
38154 to be explicit about the bitwidth. */
38155 uint32_t action_flag;
38156 struct jit_code_entry *relevant_entry;
38157 struct jit_code_entry *first_entry;
38160 /* GDB puts a breakpoint in this function. */
38161 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
38163 /* Make sure to specify the version statically, because the
38164 debugger may check the version before we can set it. */
38165 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
38168 If the JIT is multi-threaded, then it is important that the JIT synchronize any
38169 modifications to this global data properly, which can easily be done by putting
38170 a global mutex around modifications to these structures.
38172 @node Registering Code
38173 @section Registering Code
38175 To register code with @value{GDBN}, the JIT should follow this protocol:
38179 Generate an object file in memory with symbols and other desired debug
38180 information. The file must include the virtual addresses of the sections.
38183 Create a code entry for the file, which gives the start and size of the symbol
38187 Add it to the linked list in the JIT descriptor.
38190 Point the relevant_entry field of the descriptor at the entry.
38193 Set @code{action_flag} to @code{JIT_REGISTER} and call
38194 @code{__jit_debug_register_code}.
38197 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
38198 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
38199 new code. However, the linked list must still be maintained in order to allow
38200 @value{GDBN} to attach to a running process and still find the symbol files.
38202 @node Unregistering Code
38203 @section Unregistering Code
38205 If code is freed, then the JIT should use the following protocol:
38209 Remove the code entry corresponding to the code from the linked list.
38212 Point the @code{relevant_entry} field of the descriptor at the code entry.
38215 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
38216 @code{__jit_debug_register_code}.
38219 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
38220 and the JIT will leak the memory used for the associated symbol files.
38222 @node Custom Debug Info
38223 @section Custom Debug Info
38224 @cindex custom JIT debug info
38225 @cindex JIT debug info reader
38227 Generating debug information in platform-native file formats (like ELF
38228 or COFF) may be an overkill for JIT compilers; especially if all the
38229 debug info is used for is displaying a meaningful backtrace. The
38230 issue can be resolved by having the JIT writers decide on a debug info
38231 format and also provide a reader that parses the debug info generated
38232 by the JIT compiler. This section gives a brief overview on writing
38233 such a parser. More specific details can be found in the source file
38234 @file{gdb/jit-reader.in}, which is also installed as a header at
38235 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
38237 The reader is implemented as a shared object (so this functionality is
38238 not available on platforms which don't allow loading shared objects at
38239 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
38240 @code{jit-reader-unload} are provided, to be used to load and unload
38241 the readers from a preconfigured directory. Once loaded, the shared
38242 object is used the parse the debug information emitted by the JIT
38246 * Using JIT Debug Info Readers:: How to use supplied readers correctly
38247 * Writing JIT Debug Info Readers:: Creating a debug-info reader
38250 @node Using JIT Debug Info Readers
38251 @subsection Using JIT Debug Info Readers
38252 @kindex jit-reader-load
38253 @kindex jit-reader-unload
38255 Readers can be loaded and unloaded using the @code{jit-reader-load}
38256 and @code{jit-reader-unload} commands.
38259 @item jit-reader-load @var{reader}
38260 Load the JIT reader named @var{reader}, which is a shared
38261 object specified as either an absolute or a relative file name. In
38262 the latter case, @value{GDBN} will try to load the reader from a
38263 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
38264 system (here @var{libdir} is the system library directory, often
38265 @file{/usr/local/lib}).
38267 Only one reader can be active at a time; trying to load a second
38268 reader when one is already loaded will result in @value{GDBN}
38269 reporting an error. A new JIT reader can be loaded by first unloading
38270 the current one using @code{jit-reader-unload} and then invoking
38271 @code{jit-reader-load}.
38273 @item jit-reader-unload
38274 Unload the currently loaded JIT reader.
38278 @node Writing JIT Debug Info Readers
38279 @subsection Writing JIT Debug Info Readers
38280 @cindex writing JIT debug info readers
38282 As mentioned, a reader is essentially a shared object conforming to a
38283 certain ABI. This ABI is described in @file{jit-reader.h}.
38285 @file{jit-reader.h} defines the structures, macros and functions
38286 required to write a reader. It is installed (along with
38287 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
38288 the system include directory.
38290 Readers need to be released under a GPL compatible license. A reader
38291 can be declared as released under such a license by placing the macro
38292 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
38294 The entry point for readers is the symbol @code{gdb_init_reader},
38295 which is expected to be a function with the prototype
38297 @findex gdb_init_reader
38299 extern struct gdb_reader_funcs *gdb_init_reader (void);
38302 @cindex @code{struct gdb_reader_funcs}
38304 @code{struct gdb_reader_funcs} contains a set of pointers to callback
38305 functions. These functions are executed to read the debug info
38306 generated by the JIT compiler (@code{read}), to unwind stack frames
38307 (@code{unwind}) and to create canonical frame IDs
38308 (@code{get_frame_id}). It also has a callback that is called when the
38309 reader is being unloaded (@code{destroy}). The struct looks like this
38312 struct gdb_reader_funcs
38314 /* Must be set to GDB_READER_INTERFACE_VERSION. */
38315 int reader_version;
38317 /* For use by the reader. */
38320 gdb_read_debug_info *read;
38321 gdb_unwind_frame *unwind;
38322 gdb_get_frame_id *get_frame_id;
38323 gdb_destroy_reader *destroy;
38327 @cindex @code{struct gdb_symbol_callbacks}
38328 @cindex @code{struct gdb_unwind_callbacks}
38330 The callbacks are provided with another set of callbacks by
38331 @value{GDBN} to do their job. For @code{read}, these callbacks are
38332 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
38333 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
38334 @code{struct gdb_symbol_callbacks} has callbacks to create new object
38335 files and new symbol tables inside those object files. @code{struct
38336 gdb_unwind_callbacks} has callbacks to read registers off the current
38337 frame and to write out the values of the registers in the previous
38338 frame. Both have a callback (@code{target_read}) to read bytes off the
38339 target's address space.
38341 @node In-Process Agent
38342 @chapter In-Process Agent
38343 @cindex debugging agent
38344 The traditional debugging model is conceptually low-speed, but works fine,
38345 because most bugs can be reproduced in debugging-mode execution. However,
38346 as multi-core or many-core processors are becoming mainstream, and
38347 multi-threaded programs become more and more popular, there should be more
38348 and more bugs that only manifest themselves at normal-mode execution, for
38349 example, thread races, because debugger's interference with the program's
38350 timing may conceal the bugs. On the other hand, in some applications,
38351 it is not feasible for the debugger to interrupt the program's execution
38352 long enough for the developer to learn anything helpful about its behavior.
38353 If the program's correctness depends on its real-time behavior, delays
38354 introduced by a debugger might cause the program to fail, even when the
38355 code itself is correct. It is useful to be able to observe the program's
38356 behavior without interrupting it.
38358 Therefore, traditional debugging model is too intrusive to reproduce
38359 some bugs. In order to reduce the interference with the program, we can
38360 reduce the number of operations performed by debugger. The
38361 @dfn{In-Process Agent}, a shared library, is running within the same
38362 process with inferior, and is able to perform some debugging operations
38363 itself. As a result, debugger is only involved when necessary, and
38364 performance of debugging can be improved accordingly. Note that
38365 interference with program can be reduced but can't be removed completely,
38366 because the in-process agent will still stop or slow down the program.
38368 The in-process agent can interpret and execute Agent Expressions
38369 (@pxref{Agent Expressions}) during performing debugging operations. The
38370 agent expressions can be used for different purposes, such as collecting
38371 data in tracepoints, and condition evaluation in breakpoints.
38373 @anchor{Control Agent}
38374 You can control whether the in-process agent is used as an aid for
38375 debugging with the following commands:
38378 @kindex set agent on
38380 Causes the in-process agent to perform some operations on behalf of the
38381 debugger. Just which operations requested by the user will be done
38382 by the in-process agent depends on the its capabilities. For example,
38383 if you request to evaluate breakpoint conditions in the in-process agent,
38384 and the in-process agent has such capability as well, then breakpoint
38385 conditions will be evaluated in the in-process agent.
38387 @kindex set agent off
38388 @item set agent off
38389 Disables execution of debugging operations by the in-process agent. All
38390 of the operations will be performed by @value{GDBN}.
38394 Display the current setting of execution of debugging operations by
38395 the in-process agent.
38399 * In-Process Agent Protocol::
38402 @node In-Process Agent Protocol
38403 @section In-Process Agent Protocol
38404 @cindex in-process agent protocol
38406 The in-process agent is able to communicate with both @value{GDBN} and
38407 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
38408 used for communications between @value{GDBN} or GDBserver and the IPA.
38409 In general, @value{GDBN} or GDBserver sends commands
38410 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
38411 in-process agent replies back with the return result of the command, or
38412 some other information. The data sent to in-process agent is composed
38413 of primitive data types, such as 4-byte or 8-byte type, and composite
38414 types, which are called objects (@pxref{IPA Protocol Objects}).
38417 * IPA Protocol Objects::
38418 * IPA Protocol Commands::
38421 @node IPA Protocol Objects
38422 @subsection IPA Protocol Objects
38423 @cindex ipa protocol objects
38425 The commands sent to and results received from agent may contain some
38426 complex data types called @dfn{objects}.
38428 The in-process agent is running on the same machine with @value{GDBN}
38429 or GDBserver, so it doesn't have to handle as much differences between
38430 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38431 However, there are still some differences of two ends in two processes:
38435 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38436 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38438 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38439 GDBserver is compiled with one, and in-process agent is compiled with
38443 Here are the IPA Protocol Objects:
38447 agent expression object. It represents an agent expression
38448 (@pxref{Agent Expressions}).
38449 @anchor{agent expression object}
38451 tracepoint action object. It represents a tracepoint action
38452 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38453 memory, static trace data and to evaluate expression.
38454 @anchor{tracepoint action object}
38456 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38457 @anchor{tracepoint object}
38461 The following table describes important attributes of each IPA protocol
38464 @multitable @columnfractions .30 .20 .50
38465 @headitem Name @tab Size @tab Description
38466 @item @emph{agent expression object} @tab @tab
38467 @item length @tab 4 @tab length of bytes code
38468 @item byte code @tab @var{length} @tab contents of byte code
38469 @item @emph{tracepoint action for collecting memory} @tab @tab
38470 @item 'M' @tab 1 @tab type of tracepoint action
38471 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38472 address of the lowest byte to collect, otherwise @var{addr} is the offset
38473 of @var{basereg} for memory collecting.
38474 @item len @tab 8 @tab length of memory for collecting
38475 @item basereg @tab 4 @tab the register number containing the starting
38476 memory address for collecting.
38477 @item @emph{tracepoint action for collecting registers} @tab @tab
38478 @item 'R' @tab 1 @tab type of tracepoint action
38479 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38480 @item 'L' @tab 1 @tab type of tracepoint action
38481 @item @emph{tracepoint action for expression evaluation} @tab @tab
38482 @item 'X' @tab 1 @tab type of tracepoint action
38483 @item agent expression @tab length of @tab @ref{agent expression object}
38484 @item @emph{tracepoint object} @tab @tab
38485 @item number @tab 4 @tab number of tracepoint
38486 @item address @tab 8 @tab address of tracepoint inserted on
38487 @item type @tab 4 @tab type of tracepoint
38488 @item enabled @tab 1 @tab enable or disable of tracepoint
38489 @item step_count @tab 8 @tab step
38490 @item pass_count @tab 8 @tab pass
38491 @item numactions @tab 4 @tab number of tracepoint actions
38492 @item hit count @tab 8 @tab hit count
38493 @item trace frame usage @tab 8 @tab trace frame usage
38494 @item compiled_cond @tab 8 @tab compiled condition
38495 @item orig_size @tab 8 @tab orig size
38496 @item condition @tab 4 if condition is NULL otherwise length of
38497 @ref{agent expression object}
38498 @tab zero if condition is NULL, otherwise is
38499 @ref{agent expression object}
38500 @item actions @tab variable
38501 @tab numactions number of @ref{tracepoint action object}
38504 @node IPA Protocol Commands
38505 @subsection IPA Protocol Commands
38506 @cindex ipa protocol commands
38508 The spaces in each command are delimiters to ease reading this commands
38509 specification. They don't exist in real commands.
38513 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38514 Installs a new fast tracepoint described by @var{tracepoint_object}
38515 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38516 head of @dfn{jumppad}, which is used to jump to data collection routine
38521 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38522 @var{target_address} is address of tracepoint in the inferior.
38523 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38524 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38525 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38526 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38533 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38534 is about to kill inferiors.
38542 @item probe_marker_at:@var{address}
38543 Asks in-process agent to probe the marker at @var{address}.
38550 @item unprobe_marker_at:@var{address}
38551 Asks in-process agent to unprobe the marker at @var{address}.
38555 @chapter Reporting Bugs in @value{GDBN}
38556 @cindex bugs in @value{GDBN}
38557 @cindex reporting bugs in @value{GDBN}
38559 Your bug reports play an essential role in making @value{GDBN} reliable.
38561 Reporting a bug may help you by bringing a solution to your problem, or it
38562 may not. But in any case the principal function of a bug report is to help
38563 the entire community by making the next version of @value{GDBN} work better. Bug
38564 reports are your contribution to the maintenance of @value{GDBN}.
38566 In order for a bug report to serve its purpose, you must include the
38567 information that enables us to fix the bug.
38570 * Bug Criteria:: Have you found a bug?
38571 * Bug Reporting:: How to report bugs
38575 @section Have You Found a Bug?
38576 @cindex bug criteria
38578 If you are not sure whether you have found a bug, here are some guidelines:
38581 @cindex fatal signal
38582 @cindex debugger crash
38583 @cindex crash of debugger
38585 If the debugger gets a fatal signal, for any input whatever, that is a
38586 @value{GDBN} bug. Reliable debuggers never crash.
38588 @cindex error on valid input
38590 If @value{GDBN} produces an error message for valid input, that is a
38591 bug. (Note that if you're cross debugging, the problem may also be
38592 somewhere in the connection to the target.)
38594 @cindex invalid input
38596 If @value{GDBN} does not produce an error message for invalid input,
38597 that is a bug. However, you should note that your idea of
38598 ``invalid input'' might be our idea of ``an extension'' or ``support
38599 for traditional practice''.
38602 If you are an experienced user of debugging tools, your suggestions
38603 for improvement of @value{GDBN} are welcome in any case.
38606 @node Bug Reporting
38607 @section How to Report Bugs
38608 @cindex bug reports
38609 @cindex @value{GDBN} bugs, reporting
38611 A number of companies and individuals offer support for @sc{gnu} products.
38612 If you obtained @value{GDBN} from a support organization, we recommend you
38613 contact that organization first.
38615 You can find contact information for many support companies and
38616 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38618 @c should add a web page ref...
38621 @ifset BUGURL_DEFAULT
38622 In any event, we also recommend that you submit bug reports for
38623 @value{GDBN}. The preferred method is to submit them directly using
38624 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38625 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
38628 @strong{Do not send bug reports to @samp{info-gdb}, or to
38629 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
38630 not want to receive bug reports. Those that do have arranged to receive
38633 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
38634 serves as a repeater. The mailing list and the newsgroup carry exactly
38635 the same messages. Often people think of posting bug reports to the
38636 newsgroup instead of mailing them. This appears to work, but it has one
38637 problem which can be crucial: a newsgroup posting often lacks a mail
38638 path back to the sender. Thus, if we need to ask for more information,
38639 we may be unable to reach you. For this reason, it is better to send
38640 bug reports to the mailing list.
38642 @ifclear BUGURL_DEFAULT
38643 In any event, we also recommend that you submit bug reports for
38644 @value{GDBN} to @value{BUGURL}.
38648 The fundamental principle of reporting bugs usefully is this:
38649 @strong{report all the facts}. If you are not sure whether to state a
38650 fact or leave it out, state it!
38652 Often people omit facts because they think they know what causes the
38653 problem and assume that some details do not matter. Thus, you might
38654 assume that the name of the variable you use in an example does not matter.
38655 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
38656 stray memory reference which happens to fetch from the location where that
38657 name is stored in memory; perhaps, if the name were different, the contents
38658 of that location would fool the debugger into doing the right thing despite
38659 the bug. Play it safe and give a specific, complete example. That is the
38660 easiest thing for you to do, and the most helpful.
38662 Keep in mind that the purpose of a bug report is to enable us to fix the
38663 bug. It may be that the bug has been reported previously, but neither
38664 you nor we can know that unless your bug report is complete and
38667 Sometimes people give a few sketchy facts and ask, ``Does this ring a
38668 bell?'' Those bug reports are useless, and we urge everyone to
38669 @emph{refuse to respond to them} except to chide the sender to report
38672 To enable us to fix the bug, you should include all these things:
38676 The version of @value{GDBN}. @value{GDBN} announces it if you start
38677 with no arguments; you can also print it at any time using @code{show
38680 Without this, we will not know whether there is any point in looking for
38681 the bug in the current version of @value{GDBN}.
38684 The type of machine you are using, and the operating system name and
38688 The details of the @value{GDBN} build-time configuration.
38689 @value{GDBN} shows these details if you invoke it with the
38690 @option{--configuration} command-line option, or if you type
38691 @code{show configuration} at @value{GDBN}'s prompt.
38694 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38695 ``@value{GCC}--2.8.1''.
38698 What compiler (and its version) was used to compile the program you are
38699 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38700 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38701 to get this information; for other compilers, see the documentation for
38705 The command arguments you gave the compiler to compile your example and
38706 observe the bug. For example, did you use @samp{-O}? To guarantee
38707 you will not omit something important, list them all. A copy of the
38708 Makefile (or the output from make) is sufficient.
38710 If we were to try to guess the arguments, we would probably guess wrong
38711 and then we might not encounter the bug.
38714 A complete input script, and all necessary source files, that will
38718 A description of what behavior you observe that you believe is
38719 incorrect. For example, ``It gets a fatal signal.''
38721 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38722 will certainly notice it. But if the bug is incorrect output, we might
38723 not notice unless it is glaringly wrong. You might as well not give us
38724 a chance to make a mistake.
38726 Even if the problem you experience is a fatal signal, you should still
38727 say so explicitly. Suppose something strange is going on, such as, your
38728 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38729 the C library on your system. (This has happened!) Your copy might
38730 crash and ours would not. If you told us to expect a crash, then when
38731 ours fails to crash, we would know that the bug was not happening for
38732 us. If you had not told us to expect a crash, then we would not be able
38733 to draw any conclusion from our observations.
38736 @cindex recording a session script
38737 To collect all this information, you can use a session recording program
38738 such as @command{script}, which is available on many Unix systems.
38739 Just run your @value{GDBN} session inside @command{script} and then
38740 include the @file{typescript} file with your bug report.
38742 Another way to record a @value{GDBN} session is to run @value{GDBN}
38743 inside Emacs and then save the entire buffer to a file.
38746 If you wish to suggest changes to the @value{GDBN} source, send us context
38747 diffs. If you even discuss something in the @value{GDBN} source, refer to
38748 it by context, not by line number.
38750 The line numbers in our development sources will not match those in your
38751 sources. Your line numbers would convey no useful information to us.
38755 Here are some things that are not necessary:
38759 A description of the envelope of the bug.
38761 Often people who encounter a bug spend a lot of time investigating
38762 which changes to the input file will make the bug go away and which
38763 changes will not affect it.
38765 This is often time consuming and not very useful, because the way we
38766 will find the bug is by running a single example under the debugger
38767 with breakpoints, not by pure deduction from a series of examples.
38768 We recommend that you save your time for something else.
38770 Of course, if you can find a simpler example to report @emph{instead}
38771 of the original one, that is a convenience for us. Errors in the
38772 output will be easier to spot, running under the debugger will take
38773 less time, and so on.
38775 However, simplification is not vital; if you do not want to do this,
38776 report the bug anyway and send us the entire test case you used.
38779 A patch for the bug.
38781 A patch for the bug does help us if it is a good one. But do not omit
38782 the necessary information, such as the test case, on the assumption that
38783 a patch is all we need. We might see problems with your patch and decide
38784 to fix the problem another way, or we might not understand it at all.
38786 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38787 construct an example that will make the program follow a certain path
38788 through the code. If you do not send us the example, we will not be able
38789 to construct one, so we will not be able to verify that the bug is fixed.
38791 And if we cannot understand what bug you are trying to fix, or why your
38792 patch should be an improvement, we will not install it. A test case will
38793 help us to understand.
38796 A guess about what the bug is or what it depends on.
38798 Such guesses are usually wrong. Even we cannot guess right about such
38799 things without first using the debugger to find the facts.
38802 @c The readline documentation is distributed with the readline code
38803 @c and consists of the two following files:
38806 @c Use -I with makeinfo to point to the appropriate directory,
38807 @c environment var TEXINPUTS with TeX.
38808 @ifclear SYSTEM_READLINE
38809 @include rluser.texi
38810 @include hsuser.texi
38814 @appendix In Memoriam
38816 The @value{GDBN} project mourns the loss of the following long-time
38821 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
38822 to Free Software in general. Outside of @value{GDBN}, he was known in
38823 the Amiga world for his series of Fish Disks, and the GeekGadget project.
38825 @item Michael Snyder
38826 Michael was one of the Global Maintainers of the @value{GDBN} project,
38827 with contributions recorded as early as 1996, until 2011. In addition
38828 to his day to day participation, he was a large driving force behind
38829 adding Reverse Debugging to @value{GDBN}.
38832 Beyond their technical contributions to the project, they were also
38833 enjoyable members of the Free Software Community. We will miss them.
38835 @node Formatting Documentation
38836 @appendix Formatting Documentation
38838 @cindex @value{GDBN} reference card
38839 @cindex reference card
38840 The @value{GDBN} 4 release includes an already-formatted reference card, ready
38841 for printing with PostScript or Ghostscript, in the @file{gdb}
38842 subdirectory of the main source directory@footnote{In
38843 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
38844 release.}. If you can use PostScript or Ghostscript with your printer,
38845 you can print the reference card immediately with @file{refcard.ps}.
38847 The release also includes the source for the reference card. You
38848 can format it, using @TeX{}, by typing:
38854 The @value{GDBN} reference card is designed to print in @dfn{landscape}
38855 mode on US ``letter'' size paper;
38856 that is, on a sheet 11 inches wide by 8.5 inches
38857 high. You will need to specify this form of printing as an option to
38858 your @sc{dvi} output program.
38860 @cindex documentation
38862 All the documentation for @value{GDBN} comes as part of the machine-readable
38863 distribution. The documentation is written in Texinfo format, which is
38864 a documentation system that uses a single source file to produce both
38865 on-line information and a printed manual. You can use one of the Info
38866 formatting commands to create the on-line version of the documentation
38867 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
38869 @value{GDBN} includes an already formatted copy of the on-line Info
38870 version of this manual in the @file{gdb} subdirectory. The main Info
38871 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
38872 subordinate files matching @samp{gdb.info*} in the same directory. If
38873 necessary, you can print out these files, or read them with any editor;
38874 but they are easier to read using the @code{info} subsystem in @sc{gnu}
38875 Emacs or the standalone @code{info} program, available as part of the
38876 @sc{gnu} Texinfo distribution.
38878 If you want to format these Info files yourself, you need one of the
38879 Info formatting programs, such as @code{texinfo-format-buffer} or
38882 If you have @code{makeinfo} installed, and are in the top level
38883 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
38884 version @value{GDBVN}), you can make the Info file by typing:
38891 If you want to typeset and print copies of this manual, you need @TeX{},
38892 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
38893 Texinfo definitions file.
38895 @TeX{} is a typesetting program; it does not print files directly, but
38896 produces output files called @sc{dvi} files. To print a typeset
38897 document, you need a program to print @sc{dvi} files. If your system
38898 has @TeX{} installed, chances are it has such a program. The precise
38899 command to use depends on your system; @kbd{lpr -d} is common; another
38900 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
38901 require a file name without any extension or a @samp{.dvi} extension.
38903 @TeX{} also requires a macro definitions file called
38904 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
38905 written in Texinfo format. On its own, @TeX{} cannot either read or
38906 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
38907 and is located in the @file{gdb-@var{version-number}/texinfo}
38910 If you have @TeX{} and a @sc{dvi} printer program installed, you can
38911 typeset and print this manual. First switch to the @file{gdb}
38912 subdirectory of the main source directory (for example, to
38913 @file{gdb-@value{GDBVN}/gdb}) and type:
38919 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
38921 @node Installing GDB
38922 @appendix Installing @value{GDBN}
38923 @cindex installation
38926 * Requirements:: Requirements for building @value{GDBN}
38927 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
38928 * Separate Objdir:: Compiling @value{GDBN} in another directory
38929 * Config Names:: Specifying names for hosts and targets
38930 * Configure Options:: Summary of options for configure
38931 * System-wide configuration:: Having a system-wide init file
38935 @section Requirements for Building @value{GDBN}
38936 @cindex building @value{GDBN}, requirements for
38938 Building @value{GDBN} requires various tools and packages to be available.
38939 Other packages will be used only if they are found.
38941 @heading Tools/Packages Necessary for Building @value{GDBN}
38943 @item C@t{++}11 compiler
38944 @value{GDBN} is written in C@t{++}11. It should be buildable with any
38945 recent C@t{++}11 compiler, e.g.@: GCC.
38948 @value{GDBN}'s build system relies on features only found in the GNU
38949 make program. Other variants of @code{make} will not work.
38951 @item GMP (The GNU Multiple Precision Arithmetic Library)
38952 @value{GDBN} now uses GMP to perform some of its arithmetics.
38953 This library may be included with your operating system distribution;
38954 if it is not, you can get the latest version from
38955 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
38956 you can use the @option{--with-libgmp-prefix} option to specify
38961 @heading Tools/Packages Optional for Building @value{GDBN}
38965 @value{GDBN} can use the Expat XML parsing library. This library may be
38966 included with your operating system distribution; if it is not, you
38967 can get the latest version from @url{http://expat.sourceforge.net}.
38968 The @file{configure} script will search for this library in several
38969 standard locations; if it is installed in an unusual path, you can
38970 use the @option{--with-libexpat-prefix} option to specify its location.
38976 Remote protocol memory maps (@pxref{Memory Map Format})
38978 Target descriptions (@pxref{Target Descriptions})
38980 Remote shared library lists (@xref{Library List Format},
38981 or alternatively @pxref{Library List Format for SVR4 Targets})
38983 MS-Windows shared libraries (@pxref{Shared Libraries})
38985 Traceframe info (@pxref{Traceframe Info Format})
38987 Branch trace (@pxref{Branch Trace Format},
38988 @pxref{Branch Trace Configuration Format})
38992 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
38993 default, @value{GDBN} will be compiled if the Guile libraries are
38994 installed and are found by @file{configure}. You can use the
38995 @code{--with-guile} option to request Guile, and pass either the Guile
38996 version number or the file name of the relevant @code{pkg-config}
38997 program to choose a particular version of Guile.
39000 @value{GDBN}'s features related to character sets (@pxref{Character
39001 Sets}) require a functioning @code{iconv} implementation. If you are
39002 on a GNU system, then this is provided by the GNU C Library. Some
39003 other systems also provide a working @code{iconv}.
39005 If @value{GDBN} is using the @code{iconv} program which is installed
39006 in a non-standard place, you will need to tell @value{GDBN} where to
39007 find it. This is done with @option{--with-iconv-bin} which specifies
39008 the directory that contains the @code{iconv} program. This program is
39009 run in order to make a list of the available character sets.
39011 On systems without @code{iconv}, you can install GNU Libiconv. If
39012 Libiconv is installed in a standard place, @value{GDBN} will
39013 automatically use it if it is needed. If you have previously
39014 installed Libiconv in a non-standard place, you can use the
39015 @option{--with-libiconv-prefix} option to @file{configure}.
39017 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
39018 arrange to build Libiconv if a directory named @file{libiconv} appears
39019 in the top-most source directory. If Libiconv is built this way, and
39020 if the operating system does not provide a suitable @code{iconv}
39021 implementation, then the just-built library will automatically be used
39022 by @value{GDBN}. One easy way to set this up is to download GNU
39023 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
39024 source tree, and then rename the directory holding the Libiconv source
39025 code to @samp{libiconv}.
39028 @value{GDBN} can support debugging sections that are compressed with
39029 the LZMA library. @xref{MiniDebugInfo}. If this library is not
39030 included with your operating system, you can find it in the xz package
39031 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
39032 the usual place, then the @file{configure} script will use it
39033 automatically. If it is installed in an unusual path, you can use the
39034 @option{--with-liblzma-prefix} option to specify its location.
39038 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
39039 library. This library may be included with your operating system
39040 distribution; if it is not, you can get the latest version from
39041 @url{http://www.mpfr.org}. The @file{configure} script will search
39042 for this library in several standard locations; if it is installed
39043 in an unusual path, you can use the @option{--with-libmpfr-prefix}
39044 option to specify its location.
39046 GNU MPFR is used to emulate target floating-point arithmetic during
39047 expression evaluation when the target uses different floating-point
39048 formats than the host. If GNU MPFR it is not available, @value{GDBN}
39049 will fall back to using host floating-point arithmetic.
39052 @value{GDBN} can be scripted using Python language. @xref{Python}.
39053 By default, @value{GDBN} will be compiled if the Python libraries are
39054 installed and are found by @file{configure}. You can use the
39055 @code{--with-python} option to request Python, and pass either the
39056 file name of the relevant @code{python} executable, or the name of the
39057 directory in which Python is installed, to choose a particular
39058 installation of Python.
39061 @cindex compressed debug sections
39062 @value{GDBN} will use the @samp{zlib} library, if available, to read
39063 compressed debug sections. Some linkers, such as GNU gold, are capable
39064 of producing binaries with compressed debug sections. If @value{GDBN}
39065 is compiled with @samp{zlib}, it will be able to read the debug
39066 information in such binaries.
39068 The @samp{zlib} library is likely included with your operating system
39069 distribution; if it is not, you can get the latest version from
39070 @url{http://zlib.net}.
39073 @node Running Configure
39074 @section Invoking the @value{GDBN} @file{configure} Script
39075 @cindex configuring @value{GDBN}
39076 @value{GDBN} comes with a @file{configure} script that automates the process
39077 of preparing @value{GDBN} for installation; you can then use @code{make} to
39078 build the @code{gdb} program.
39080 @c irrelevant in info file; it's as current as the code it lives with.
39081 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
39082 look at the @file{README} file in the sources; we may have improved the
39083 installation procedures since publishing this manual.}
39086 The @value{GDBN} distribution includes all the source code you need for
39087 @value{GDBN} in a single directory, whose name is usually composed by
39088 appending the version number to @samp{gdb}.
39090 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
39091 @file{gdb-@value{GDBVN}} directory. That directory contains:
39094 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
39095 script for configuring @value{GDBN} and all its supporting libraries
39097 @item gdb-@value{GDBVN}/gdb
39098 the source specific to @value{GDBN} itself
39100 @item gdb-@value{GDBVN}/bfd
39101 source for the Binary File Descriptor library
39103 @item gdb-@value{GDBVN}/include
39104 @sc{gnu} include files
39106 @item gdb-@value{GDBVN}/libiberty
39107 source for the @samp{-liberty} free software library
39109 @item gdb-@value{GDBVN}/opcodes
39110 source for the library of opcode tables and disassemblers
39112 @item gdb-@value{GDBVN}/readline
39113 source for the @sc{gnu} command-line interface
39116 There may be other subdirectories as well.
39118 The simplest way to configure and build @value{GDBN} is to run @file{configure}
39119 from the @file{gdb-@var{version-number}} source directory, which in
39120 this example is the @file{gdb-@value{GDBVN}} directory.
39122 First switch to the @file{gdb-@var{version-number}} source directory
39123 if you are not already in it; then run @file{configure}. Pass the
39124 identifier for the platform on which @value{GDBN} will run as an
39130 cd gdb-@value{GDBVN}
39135 Running @samp{configure} and then running @code{make} builds the
39136 included supporting libraries, then @code{gdb} itself. The configured
39137 source files, and the binaries, are left in the corresponding source
39141 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
39142 system does not recognize this automatically when you run a different
39143 shell, you may need to run @code{sh} on it explicitly:
39149 You should run the @file{configure} script from the top directory in the
39150 source tree, the @file{gdb-@var{version-number}} directory. If you run
39151 @file{configure} from one of the subdirectories, you will configure only
39152 that subdirectory. That is usually not what you want. In particular,
39153 if you run the first @file{configure} from the @file{gdb} subdirectory
39154 of the @file{gdb-@var{version-number}} directory, you will omit the
39155 configuration of @file{bfd}, @file{readline}, and other sibling
39156 directories of the @file{gdb} subdirectory. This leads to build errors
39157 about missing include files such as @file{bfd/bfd.h}.
39159 You can install @code{@value{GDBN}} anywhere. The best way to do this
39160 is to pass the @code{--prefix} option to @code{configure}, and then
39161 install it with @code{make install}.
39163 @node Separate Objdir
39164 @section Compiling @value{GDBN} in Another Directory
39166 If you want to run @value{GDBN} versions for several host or target machines,
39167 you need a different @code{gdb} compiled for each combination of
39168 host and target. @file{configure} is designed to make this easy by
39169 allowing you to generate each configuration in a separate subdirectory,
39170 rather than in the source directory. If your @code{make} program
39171 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
39172 @code{make} in each of these directories builds the @code{gdb}
39173 program specified there.
39175 To build @code{gdb} in a separate directory, run @file{configure}
39176 with the @samp{--srcdir} option to specify where to find the source.
39177 (You also need to specify a path to find @file{configure}
39178 itself from your working directory. If the path to @file{configure}
39179 would be the same as the argument to @samp{--srcdir}, you can leave out
39180 the @samp{--srcdir} option; it is assumed.)
39182 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
39183 separate directory for a Sun 4 like this:
39187 cd gdb-@value{GDBVN}
39190 ../gdb-@value{GDBVN}/configure
39195 When @file{configure} builds a configuration using a remote source
39196 directory, it creates a tree for the binaries with the same structure
39197 (and using the same names) as the tree under the source directory. In
39198 the example, you'd find the Sun 4 library @file{libiberty.a} in the
39199 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
39200 @file{gdb-sun4/gdb}.
39202 Make sure that your path to the @file{configure} script has just one
39203 instance of @file{gdb} in it. If your path to @file{configure} looks
39204 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
39205 one subdirectory of @value{GDBN}, not the whole package. This leads to
39206 build errors about missing include files such as @file{bfd/bfd.h}.
39208 One popular reason to build several @value{GDBN} configurations in separate
39209 directories is to configure @value{GDBN} for cross-compiling (where
39210 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
39211 programs that run on another machine---the @dfn{target}).
39212 You specify a cross-debugging target by
39213 giving the @samp{--target=@var{target}} option to @file{configure}.
39215 When you run @code{make} to build a program or library, you must run
39216 it in a configured directory---whatever directory you were in when you
39217 called @file{configure} (or one of its subdirectories).
39219 The @code{Makefile} that @file{configure} generates in each source
39220 directory also runs recursively. If you type @code{make} in a source
39221 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
39222 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
39223 will build all the required libraries, and then build GDB.
39225 When you have multiple hosts or targets configured in separate
39226 directories, you can run @code{make} on them in parallel (for example,
39227 if they are NFS-mounted on each of the hosts); they will not interfere
39231 @section Specifying Names for Hosts and Targets
39233 The specifications used for hosts and targets in the @file{configure}
39234 script are based on a three-part naming scheme, but some short predefined
39235 aliases are also supported. The full naming scheme encodes three pieces
39236 of information in the following pattern:
39239 @var{architecture}-@var{vendor}-@var{os}
39242 For example, you can use the alias @code{sun4} as a @var{host} argument,
39243 or as the value for @var{target} in a @code{--target=@var{target}}
39244 option. The equivalent full name is @samp{sparc-sun-sunos4}.
39246 The @file{configure} script accompanying @value{GDBN} does not provide
39247 any query facility to list all supported host and target names or
39248 aliases. @file{configure} calls the Bourne shell script
39249 @code{config.sub} to map abbreviations to full names; you can read the
39250 script, if you wish, or you can use it to test your guesses on
39251 abbreviations---for example:
39254 % sh config.sub i386-linux
39256 % sh config.sub alpha-linux
39257 alpha-unknown-linux-gnu
39258 % sh config.sub hp9k700
39260 % sh config.sub sun4
39261 sparc-sun-sunos4.1.1
39262 % sh config.sub sun3
39263 m68k-sun-sunos4.1.1
39264 % sh config.sub i986v
39265 Invalid configuration `i986v': machine `i986v' not recognized
39269 @code{config.sub} is also distributed in the @value{GDBN} source
39270 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
39272 @node Configure Options
39273 @section @file{configure} Options
39275 Here is a summary of the @file{configure} options and arguments that
39276 are most often useful for building @value{GDBN}. @file{configure}
39277 also has several other options not listed here. @xref{Running
39278 configure Scripts,,,autoconf}, for a full
39279 explanation of @file{configure}.
39282 configure @r{[}--help@r{]}
39283 @r{[}--prefix=@var{dir}@r{]}
39284 @r{[}--exec-prefix=@var{dir}@r{]}
39285 @r{[}--srcdir=@var{dirname}@r{]}
39286 @r{[}--target=@var{target}@r{]}
39290 You may introduce options with a single @samp{-} rather than
39291 @samp{--} if you prefer; but you may abbreviate option names if you use
39296 Display a quick summary of how to invoke @file{configure}.
39298 @item --prefix=@var{dir}
39299 Configure the source to install programs and files under directory
39302 @item --exec-prefix=@var{dir}
39303 Configure the source to install programs under directory
39306 @c avoid splitting the warning from the explanation:
39308 @item --srcdir=@var{dirname}
39309 Use this option to make configurations in directories separate from the
39310 @value{GDBN} source directories. Among other things, you can use this to
39311 build (or maintain) several configurations simultaneously, in separate
39312 directories. @file{configure} writes configuration-specific files in
39313 the current directory, but arranges for them to use the source in the
39314 directory @var{dirname}. @file{configure} creates directories under
39315 the working directory in parallel to the source directories below
39318 @item --target=@var{target}
39319 Configure @value{GDBN} for cross-debugging programs running on the specified
39320 @var{target}. Without this option, @value{GDBN} is configured to debug
39321 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
39323 There is no convenient way to generate a list of all available
39324 targets. Also see the @code{--enable-targets} option, below.
39327 There are many other options that are specific to @value{GDBN}. This
39328 lists just the most common ones; there are some very specialized
39329 options not described here.
39332 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
39333 @itemx --enable-targets=all
39334 Configure @value{GDBN} for cross-debugging programs running on the
39335 specified list of targets. The special value @samp{all} configures
39336 @value{GDBN} for debugging programs running on any target it supports.
39338 @item --with-gdb-datadir=@var{path}
39339 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
39340 here for certain supporting files or scripts. This defaults to the
39341 @file{gdb} subdirectory of @samp{datadir} (which can be set using
39344 @item --with-relocated-sources=@var{dir}
39345 Sets up the default source path substitution rule so that directory
39346 names recorded in debug information will be automatically adjusted for
39347 any directory under @var{dir}. @var{dir} should be a subdirectory of
39348 @value{GDBN}'s configured prefix, the one mentioned in the
39349 @code{--prefix} or @code{--exec-prefix} options to configure. This
39350 option is useful if GDB is supposed to be moved to a different place
39353 @item --enable-64-bit-bfd
39354 Enable 64-bit support in BFD on 32-bit hosts.
39356 @item --disable-gdbmi
39357 Build @value{GDBN} without the GDB/MI machine interface
39361 Build @value{GDBN} with the text-mode full-screen user interface
39362 (TUI). Requires a curses library (ncurses and cursesX are also
39365 @item --with-curses
39366 Use the curses library instead of the termcap library, for text-mode
39367 terminal operations.
39369 @item --with-debuginfod
39370 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
39371 library. Used to automatically fetch ELF, DWARF and source files from
39372 @code{debuginfod} servers using build IDs associated with any missing
39373 files. Enabled by default if @file{libdebuginfod} is installed and found
39374 at configure time. For more information regarding @code{debuginfod} see
39377 @item --with-libunwind-ia64
39378 Use the libunwind library for unwinding function call stack on ia64
39379 target platforms. See http://www.nongnu.org/libunwind/index.html for
39382 @item --with-system-readline
39383 Use the readline library installed on the host, rather than the
39384 library supplied as part of @value{GDBN}. Readline 7 or newer is
39385 required; this is enforced by the build system.
39387 @item --with-system-zlib
39388 Use the zlib library installed on the host, rather than the library
39389 supplied as part of @value{GDBN}.
39392 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
39393 default if libexpat is installed and found at configure time.) This
39394 library is used to read XML files supplied with @value{GDBN}. If it
39395 is unavailable, some features, such as remote protocol memory maps,
39396 target descriptions, and shared library lists, that are based on XML
39397 files, will not be available in @value{GDBN}. If your host does not
39398 have libexpat installed, you can get the latest version from
39399 `http://expat.sourceforge.net'.
39401 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
39403 Build @value{GDBN} with GNU libiconv, a character set encoding
39404 conversion library. This is not done by default, as on GNU systems
39405 the @code{iconv} that is built in to the C library is sufficient. If
39406 your host does not have a working @code{iconv}, you can get the latest
39407 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
39409 @value{GDBN}'s build system also supports building GNU libiconv as
39410 part of the overall build. @xref{Requirements}.
39413 Build @value{GDBN} with LZMA, a compression library. (Done by default
39414 if liblzma is installed and found at configure time.) LZMA is used by
39415 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
39416 platforms using the ELF object file format. If your host does not
39417 have liblzma installed, you can get the latest version from
39418 `https://tukaani.org/xz/'.
39421 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
39422 floating-point computation with correct rounding. (Done by default if
39423 GNU MPFR is installed and found at configure time.) This library is
39424 used to emulate target floating-point arithmetic during expression
39425 evaluation when the target uses different floating-point formats than
39426 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39427 to using host floating-point arithmetic. If your host does not have
39428 GNU MPFR installed, you can get the latest version from
39429 `http://www.mpfr.org'.
39431 @item --with-python@r{[}=@var{python}@r{]}
39432 Build @value{GDBN} with Python scripting support. (Done by default if
39433 libpython is present and found at configure time.) Python makes
39434 @value{GDBN} scripting much more powerful than the restricted CLI
39435 scripting language. If your host does not have Python installed, you
39436 can find it on `http://www.python.org/download/'. The oldest version
39437 of Python supported by GDB is 2.6. The optional argument @var{python}
39438 is used to find the Python headers and libraries. It can be either
39439 the name of a Python executable, or the name of the directory in which
39440 Python is installed.
39442 @item --with-guile[=GUILE]'
39443 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39444 if libguile is present and found at configure time.) If your host
39445 does not have Guile installed, you can find it at
39446 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39447 can be a version number, which will cause @code{configure} to try to
39448 use that version of Guile; or the file name of a @code{pkg-config}
39449 executable, which will be queried to find the information needed to
39450 compile and link against Guile.
39452 @item --without-included-regex
39453 Don't use the regex library included with @value{GDBN} (as part of the
39454 libiberty library). This is the default on hosts with version 2 of
39457 @item --with-sysroot=@var{dir}
39458 Use @var{dir} as the default system root directory for libraries whose
39459 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39460 @var{dir} can be modified at run time by using the @command{set
39461 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39462 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39463 default system root will be automatically adjusted if and when
39464 @value{GDBN} is moved to a different location.
39466 @item --with-system-gdbinit=@var{file}
39467 Configure @value{GDBN} to automatically load a system-wide init file.
39468 @var{file} should be an absolute file name. If @var{file} is in a
39469 directory under the configured prefix, and @value{GDBN} is moved to
39470 another location after being built, the location of the system-wide
39471 init file will be adjusted accordingly.
39473 @item --with-system-gdbinit-dir=@var{directory}
39474 Configure @value{GDBN} to automatically load init files from a
39475 system-wide directory. @var{directory} should be an absolute directory
39476 name. If @var{directory} is in a directory under the configured
39477 prefix, and @value{GDBN} is moved to another location after being
39478 built, the location of the system-wide init directory will be
39479 adjusted accordingly.
39481 @item --enable-build-warnings
39482 When building the @value{GDBN} sources, ask the compiler to warn about
39483 any code which looks even vaguely suspicious. It passes many
39484 different warning flags, depending on the exact version of the
39485 compiler you are using.
39487 @item --enable-werror
39488 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39489 to the compiler, which will fail the compilation if the compiler
39490 outputs any warning messages.
39492 @item --enable-ubsan
39493 Enable the GCC undefined behavior sanitizer. This is disabled by
39494 default, but passing @code{--enable-ubsan=yes} or
39495 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39496 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39497 It has a performance cost, so if you are looking at @value{GDBN}'s
39498 performance, you should disable it. The undefined behavior sanitizer
39499 was first introduced in GCC 4.9.
39502 @node System-wide configuration
39503 @section System-wide configuration and settings
39504 @cindex system-wide init file
39506 @value{GDBN} can be configured to have a system-wide init file and a
39507 system-wide init file directory; this file and files in that directory
39508 (if they have a recognized file extension) will be read and executed at
39509 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39511 Here are the corresponding configure options:
39514 @item --with-system-gdbinit=@var{file}
39515 Specify that the default location of the system-wide init file is
39517 @item --with-system-gdbinit-dir=@var{directory}
39518 Specify that the default location of the system-wide init file directory
39519 is @var{directory}.
39522 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39523 they may be subject to relocation. Two possible cases:
39527 If the default location of this init file/directory contains @file{$prefix},
39528 it will be subject to relocation. Suppose that the configure options
39529 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39530 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39531 init file is looked for as @file{$install/etc/gdbinit} instead of
39532 @file{$prefix/etc/gdbinit}.
39535 By contrast, if the default location does not contain the prefix,
39536 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39537 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39538 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39539 wherever @value{GDBN} is installed.
39542 If the configured location of the system-wide init file (as given by the
39543 @option{--with-system-gdbinit} option at configure time) is in the
39544 data-directory (as specified by @option{--with-gdb-datadir} at configure
39545 time) or in one of its subdirectories, then @value{GDBN} will look for the
39546 system-wide init file in the directory specified by the
39547 @option{--data-directory} command-line option.
39548 Note that the system-wide init file is only read once, during @value{GDBN}
39549 initialization. If the data-directory is changed after @value{GDBN} has
39550 started with the @code{set data-directory} command, the file will not be
39553 This applies similarly to the system-wide directory specified in
39554 @option{--with-system-gdbinit-dir}.
39556 Any supported scripting language can be used for these init files, as long
39557 as the file extension matches the scripting language. To be interpreted
39558 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39562 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39565 @node System-wide Configuration Scripts
39566 @subsection Installed System-wide Configuration Scripts
39567 @cindex system-wide configuration scripts
39569 The @file{system-gdbinit} directory, located inside the data-directory
39570 (as specified by @option{--with-gdb-datadir} at configure time) contains
39571 a number of scripts which can be used as system-wide init files. To
39572 automatically source those scripts at startup, @value{GDBN} should be
39573 configured with @option{--with-system-gdbinit}. Otherwise, any user
39574 should be able to source them by hand as needed.
39576 The following scripts are currently available:
39579 @item @file{elinos.py}
39581 @cindex ELinOS system-wide configuration script
39582 This script is useful when debugging a program on an ELinOS target.
39583 It takes advantage of the environment variables defined in a standard
39584 ELinOS environment in order to determine the location of the system
39585 shared libraries, and then sets the @samp{solib-absolute-prefix}
39586 and @samp{solib-search-path} variables appropriately.
39588 @item @file{wrs-linux.py}
39589 @pindex wrs-linux.py
39590 @cindex Wind River Linux system-wide configuration script
39591 This script is useful when debugging a program on a target running
39592 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39593 the host-side sysroot used by the target system.
39597 @node Maintenance Commands
39598 @appendix Maintenance Commands
39599 @cindex maintenance commands
39600 @cindex internal commands
39602 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39603 includes a number of commands intended for @value{GDBN} developers,
39604 that are not documented elsewhere in this manual. These commands are
39605 provided here for reference. (For commands that turn on debugging
39606 messages, see @ref{Debugging Output}.)
39609 @kindex maint agent
39610 @kindex maint agent-eval
39611 @item maint agent @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39612 @itemx maint agent-eval @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39613 Translate the given @var{expression} into remote agent bytecodes.
39614 This command is useful for debugging the Agent Expression mechanism
39615 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39616 expression useful for data collection, such as by tracepoints, while
39617 @samp{maint agent-eval} produces an expression that evaluates directly
39618 to a result. For instance, a collection expression for @code{globa +
39619 globb} will include bytecodes to record four bytes of memory at each
39620 of the addresses of @code{globa} and @code{globb}, while discarding
39621 the result of the addition, while an evaluation expression will do the
39622 addition and return the sum.
39623 If @code{-at} is given, generate remote agent bytecode for all the
39624 addresses to which @var{linespec} resolves (@pxref{Linespec
39626 If not, generate remote agent bytecode for current frame PC address.
39628 @kindex maint agent-printf
39629 @item maint agent-printf @var{format},@var{expr},...
39630 Translate the given format string and list of argument expressions
39631 into remote agent bytecodes and display them as a disassembled list.
39632 This command is useful for debugging the agent version of dynamic
39633 printf (@pxref{Dynamic Printf}).
39635 @kindex maint info breakpoints
39636 @item @anchor{maint info breakpoints}maint info breakpoints
39637 Using the same format as @samp{info breakpoints}, display both the
39638 breakpoints you've set explicitly, and those @value{GDBN} is using for
39639 internal purposes. Internal breakpoints are shown with negative
39640 breakpoint numbers. The type column identifies what kind of breakpoint
39645 Normal, explicitly set breakpoint.
39648 Normal, explicitly set watchpoint.
39651 Internal breakpoint, used to handle correctly stepping through
39652 @code{longjmp} calls.
39654 @item longjmp resume
39655 Internal breakpoint at the target of a @code{longjmp}.
39658 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
39661 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
39664 Shared library events.
39668 @kindex maint info btrace
39669 @item maint info btrace
39670 Pint information about raw branch tracing data.
39672 @kindex maint btrace packet-history
39673 @item maint btrace packet-history
39674 Print the raw branch trace packets that are used to compute the
39675 execution history for the @samp{record btrace} command. Both the
39676 information and the format in which it is printed depend on the btrace
39681 For the BTS recording format, print a list of blocks of sequential
39682 code. For each block, the following information is printed:
39686 Newer blocks have higher numbers. The oldest block has number zero.
39687 @item Lowest @samp{PC}
39688 @item Highest @samp{PC}
39692 For the Intel Processor Trace recording format, print a list of
39693 Intel Processor Trace packets. For each packet, the following
39694 information is printed:
39697 @item Packet number
39698 Newer packets have higher numbers. The oldest packet has number zero.
39700 The packet's offset in the trace stream.
39701 @item Packet opcode and payload
39705 @kindex maint btrace clear-packet-history
39706 @item maint btrace clear-packet-history
39707 Discards the cached packet history printed by the @samp{maint btrace
39708 packet-history} command. The history will be computed again when
39711 @kindex maint btrace clear
39712 @item maint btrace clear
39713 Discard the branch trace data. The data will be fetched anew and the
39714 branch trace will be recomputed when needed.
39716 This implicitly truncates the branch trace to a single branch trace
39717 buffer. When updating branch trace incrementally, the branch trace
39718 available to @value{GDBN} may be bigger than a single branch trace
39721 @kindex maint set btrace pt skip-pad
39722 @item maint set btrace pt skip-pad
39723 @kindex maint show btrace pt skip-pad
39724 @item maint show btrace pt skip-pad
39725 Control whether @value{GDBN} will skip PAD packets when computing the
39728 @kindex maint info jit
39729 @item maint info jit
39730 Print information about JIT code objects loaded in the current inferior.
39732 @anchor{maint info python-disassemblers}
39733 @kindex maint info python-disassemblers
39734 @item maint info python-disassemblers
39735 This command is defined within the @code{gdb.disassembler} Python
39736 module (@pxref{Disassembly In Python}), and will only be present after
39737 that module has been imported. To force the module to be imported do
39741 (@value{GDBP}) python import gdb.disassembler
39744 This command lists all the architectures for which a disassembler is
39745 currently registered, and the name of the disassembler. If a
39746 disassembler is registered for all architectures, then this is listed
39747 last against the @samp{GLOBAL} architecture.
39749 If one of the disassemblers would be selected for the architecture of
39750 the current inferior, then this disassembler will be marked.
39752 The following example shows a situation in which two disassemblers are
39753 registered, initially the @samp{i386} disassembler matches the current
39754 architecture, then the architecture is changed, now the @samp{GLOBAL}
39755 disassembler matches.
39759 (@value{GDBP}) show architecture
39760 The target architecture is set to "auto" (currently "i386").
39761 (@value{GDBP}) maint info python-disassemblers
39762 Architecture Disassember Name
39763 i386 Disassembler_1 (Matches current architecture)
39764 GLOBAL Disassembler_2
39767 (@value{GDBP}) set architecture arm
39768 The target architecture is set to "arm".
39769 (@value{GDBP}) maint info python-disassemblers
39771 Architecture Disassember Name
39772 i386 Disassembler_1
39773 GLOBAL Disassembler_2 (Matches current architecture)
39777 @kindex set displaced-stepping
39778 @kindex show displaced-stepping
39779 @cindex displaced stepping support
39780 @cindex out-of-line single-stepping
39781 @item set displaced-stepping
39782 @itemx show displaced-stepping
39783 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39784 if the target supports it. Displaced stepping is a way to single-step
39785 over breakpoints without removing them from the inferior, by executing
39786 an out-of-line copy of the instruction that was originally at the
39787 breakpoint location. It is also known as out-of-line single-stepping.
39790 @item set displaced-stepping on
39791 If the target architecture supports it, @value{GDBN} will use
39792 displaced stepping to step over breakpoints.
39794 @item set displaced-stepping off
39795 @value{GDBN} will not use displaced stepping to step over breakpoints,
39796 even if such is supported by the target architecture.
39798 @cindex non-stop mode, and @samp{set displaced-stepping}
39799 @item set displaced-stepping auto
39800 This is the default mode. @value{GDBN} will use displaced stepping
39801 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39802 architecture supports displaced stepping.
39805 @kindex maint check-psymtabs
39806 @item maint check-psymtabs
39807 Check the consistency of currently expanded psymtabs versus symtabs.
39808 Use this to check, for example, whether a symbol is in one but not the other.
39810 @kindex maint check-symtabs
39811 @item maint check-symtabs
39812 Check the consistency of currently expanded symtabs.
39814 @kindex maint expand-symtabs
39815 @item maint expand-symtabs [@var{regexp}]
39816 Expand symbol tables.
39817 If @var{regexp} is specified, only expand symbol tables for file
39818 names matching @var{regexp}.
39820 @kindex maint set catch-demangler-crashes
39821 @kindex maint show catch-demangler-crashes
39822 @cindex demangler crashes
39823 @item maint set catch-demangler-crashes [on|off]
39824 @itemx maint show catch-demangler-crashes
39825 Control whether @value{GDBN} should attempt to catch crashes in the
39826 symbol name demangler. The default is to attempt to catch crashes.
39827 If enabled, the first time a crash is caught, a core file is created,
39828 the offending symbol is displayed and the user is presented with the
39829 option to terminate the current session.
39831 @kindex maint cplus first_component
39832 @item maint cplus first_component @var{name}
39833 Print the first C@t{++} class/namespace component of @var{name}.
39835 @kindex maint cplus namespace
39836 @item maint cplus namespace
39837 Print the list of possible C@t{++} namespaces.
39839 @kindex maint deprecate
39840 @kindex maint undeprecate
39841 @cindex deprecated commands
39842 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
39843 @itemx maint undeprecate @var{command}
39844 Deprecate or undeprecate the named @var{command}. Deprecated commands
39845 cause @value{GDBN} to issue a warning when you use them. The optional
39846 argument @var{replacement} says which newer command should be used in
39847 favor of the deprecated one; if it is given, @value{GDBN} will mention
39848 the replacement as part of the warning.
39850 @kindex maint dump-me
39851 @item maint dump-me
39852 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
39853 Cause a fatal signal in the debugger and force it to dump its core.
39854 This is supported only on systems which support aborting a program
39855 with the @code{SIGQUIT} signal.
39857 @kindex maint internal-error
39858 @kindex maint internal-warning
39859 @kindex maint demangler-warning
39860 @cindex demangler crashes
39861 @item maint internal-error @r{[}@var{message-text}@r{]}
39862 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
39863 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
39865 Cause @value{GDBN} to call the internal function @code{internal_error},
39866 @code{internal_warning} or @code{demangler_warning} and hence behave
39867 as though an internal problem has been detected. In addition to
39868 reporting the internal problem, these functions give the user the
39869 opportunity to either quit @value{GDBN} or (for @code{internal_error}
39870 and @code{internal_warning}) create a core file of the current
39871 @value{GDBN} session.
39873 These commands take an optional parameter @var{message-text} that is
39874 used as the text of the error or warning message.
39876 Here's an example of using @code{internal-error}:
39879 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
39880 @dots{}/maint.c:121: internal-error: testing, 1, 2
39881 A problem internal to GDB has been detected. Further
39882 debugging may prove unreliable.
39883 Quit this debugging session? (y or n) @kbd{n}
39884 Create a core file? (y or n) @kbd{n}
39888 @cindex @value{GDBN} internal error
39889 @cindex internal errors, control of @value{GDBN} behavior
39890 @cindex demangler crashes
39892 @kindex maint set internal-error
39893 @kindex maint show internal-error
39894 @kindex maint set internal-warning
39895 @kindex maint show internal-warning
39896 @kindex maint set demangler-warning
39897 @kindex maint show demangler-warning
39898 @item maint set internal-error @var{action} [ask|yes|no]
39899 @itemx maint show internal-error @var{action}
39900 @itemx maint set internal-warning @var{action} [ask|yes|no]
39901 @itemx maint show internal-warning @var{action}
39902 @itemx maint set demangler-warning @var{action} [ask|yes|no]
39903 @itemx maint show demangler-warning @var{action}
39904 When @value{GDBN} reports an internal problem (error or warning) it
39905 gives the user the opportunity to both quit @value{GDBN} and create a
39906 core file of the current @value{GDBN} session. These commands let you
39907 override the default behaviour for each particular @var{action},
39908 described in the table below.
39912 You can specify that @value{GDBN} should always (yes) or never (no)
39913 quit. The default is to ask the user what to do.
39916 You can specify that @value{GDBN} should always (yes) or never (no)
39917 create a core file. The default is to ask the user what to do. Note
39918 that there is no @code{corefile} option for @code{demangler-warning}:
39919 demangler warnings always create a core file and this cannot be
39923 @kindex maint set internal-error
39924 @kindex maint show internal-error
39925 @kindex maint set internal-warning
39926 @kindex maint show internal-warning
39927 @item maint set internal-error backtrace @r{[}on|off@r{]}
39928 @itemx maint show internal-error backtrace
39929 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
39930 @itemx maint show internal-warning backtrace
39931 When @value{GDBN} reports an internal problem (error or warning) it is
39932 possible to have a backtrace of @value{GDBN} printed to the standard
39933 error stream. This is @samp{on} by default for @code{internal-error}
39934 and @samp{off} by default for @code{internal-warning}.
39936 @anchor{maint packet}
39937 @kindex maint packet
39938 @item maint packet @var{text}
39939 If @value{GDBN} is talking to an inferior via the serial protocol,
39940 then this command sends the string @var{text} to the inferior, and
39941 displays the response packet. @value{GDBN} supplies the initial
39942 @samp{$} character, the terminating @samp{#} character, and the
39945 Any non-printable characters in the reply are printed as escaped hex,
39946 e.g. @samp{\x00}, @samp{\x01}, etc.
39948 @kindex maint print architecture
39949 @item maint print architecture @r{[}@var{file}@r{]}
39950 Print the entire architecture configuration. The optional argument
39951 @var{file} names the file where the output goes.
39953 @kindex maint print c-tdesc
39954 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
39955 Print the target description (@pxref{Target Descriptions}) as
39956 a C source file. By default, the target description is for the current
39957 target, but if the optional argument @var{file} is provided, that file
39958 is used to produce the description. The @var{file} should be an XML
39959 document, of the form described in @ref{Target Description Format}.
39960 The created source file is built into @value{GDBN} when @value{GDBN} is
39961 built again. This command is used by developers after they add or
39962 modify XML target descriptions.
39964 When the optional flag @samp{-single-feature} is provided then the
39965 target description being processed (either the default, or from
39966 @var{file}) must only contain a single feature. The source file
39967 produced is different in this case.
39969 @kindex maint print xml-tdesc
39970 @item maint print xml-tdesc @r{[}@var{file}@r{]}
39971 Print the target description (@pxref{Target Descriptions}) as an XML
39972 file. By default print the target description for the current target,
39973 but if the optional argument @var{file} is provided, then that file is
39974 read in by GDB and then used to produce the description. The
39975 @var{file} should be an XML document, of the form described in
39976 @ref{Target Description Format}.
39978 @kindex maint check xml-descriptions
39979 @item maint check xml-descriptions @var{dir}
39980 Check that the target descriptions dynamically created by @value{GDBN}
39981 equal the descriptions created from XML files found in @var{dir}.
39983 @anchor{maint check libthread-db}
39984 @kindex maint check libthread-db
39985 @item maint check libthread-db
39986 Run integrity checks on the current inferior's thread debugging
39987 library. This exercises all @code{libthread_db} functionality used by
39988 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
39989 @code{proc_service} functions provided by @value{GDBN} that
39990 @code{libthread_db} uses. Note that parts of the test may be skipped
39991 on some platforms when debugging core files.
39993 @kindex maint print core-file-backed-mappings
39994 @cindex memory address space mappings
39995 @item maint print core-file-backed-mappings
39996 Print the file-backed mappings which were loaded from a core file note.
39997 This output represents state internal to @value{GDBN} and should be
39998 similar to the mappings displayed by the @code{info proc mappings}
40001 @kindex maint print dummy-frames
40002 @item maint print dummy-frames
40003 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
40006 (@value{GDBP}) @kbd{b add}
40008 (@value{GDBP}) @kbd{print add(2,3)}
40009 Breakpoint 2, add (a=2, b=3) at @dots{}
40011 The program being debugged stopped while in a function called from GDB.
40013 (@value{GDBP}) @kbd{maint print dummy-frames}
40014 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
40018 Takes an optional file parameter.
40020 @kindex maint print registers
40021 @kindex maint print raw-registers
40022 @kindex maint print cooked-registers
40023 @kindex maint print register-groups
40024 @kindex maint print remote-registers
40025 @item maint print registers @r{[}@var{file}@r{]}
40026 @itemx maint print raw-registers @r{[}@var{file}@r{]}
40027 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
40028 @itemx maint print register-groups @r{[}@var{file}@r{]}
40029 @itemx maint print remote-registers @r{[}@var{file}@r{]}
40030 Print @value{GDBN}'s internal register data structures.
40032 The command @code{maint print raw-registers} includes the contents of
40033 the raw register cache; the command @code{maint print
40034 cooked-registers} includes the (cooked) value of all registers,
40035 including registers which aren't available on the target nor visible
40036 to user; the command @code{maint print register-groups} includes the
40037 groups that each register is a member of; and the command @code{maint
40038 print remote-registers} includes the remote target's register numbers
40039 and offsets in the `G' packets.
40041 These commands take an optional parameter, a file name to which to
40042 write the information.
40044 @kindex maint print reggroups
40045 @item maint print reggroups @r{[}@var{file}@r{]}
40046 Print @value{GDBN}'s internal register group data structures. The
40047 optional argument @var{file} tells to what file to write the
40050 The register groups info looks like this:
40053 (@value{GDBP}) @kbd{maint print reggroups}
40064 @kindex maint flush register-cache
40066 @cindex register cache, flushing
40067 @item maint flush register-cache
40069 Flush the contents of the register cache and as a consequence the
40070 frame cache. This command is useful when debugging issues related to
40071 register fetching, or frame unwinding. The command @code{flushregs}
40072 is deprecated in favor of @code{maint flush register-cache}.
40074 @kindex maint flush source-cache
40075 @cindex source code, caching
40076 @item maint flush source-cache
40077 Flush @value{GDBN}'s cache of source code file contents. After
40078 @value{GDBN} reads a source file, and optionally applies styling
40079 (@pxref{Output Styling}), the file contents are cached. This command
40080 clears that cache. The next time @value{GDBN} wants to show lines
40081 from a source file, the content will be re-read.
40083 This command is useful when debugging issues related to source code
40084 styling. After flushing the cache any source code displayed by
40085 @value{GDBN} will be re-read and re-styled.
40087 @kindex maint print objfiles
40088 @cindex info for known object files
40089 @item maint print objfiles @r{[}@var{regexp}@r{]}
40090 Print a dump of all known object files.
40091 If @var{regexp} is specified, only print object files whose names
40092 match @var{regexp}. For each object file, this command prints its name,
40093 address in memory, and all of its psymtabs and symtabs.
40095 @kindex maint print user-registers
40096 @cindex user registers
40097 @item maint print user-registers
40098 List all currently available @dfn{user registers}. User registers
40099 typically provide alternate names for actual hardware registers. They
40100 include the four ``standard'' registers @code{$fp}, @code{$pc},
40101 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
40102 registers can be used in expressions in the same way as the canonical
40103 register names, but only the latter are listed by the @code{info
40104 registers} and @code{maint print registers} commands.
40106 @kindex maint print section-scripts
40107 @cindex info for known .debug_gdb_scripts-loaded scripts
40108 @item maint print section-scripts [@var{regexp}]
40109 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
40110 If @var{regexp} is specified, only print scripts loaded by object files
40111 matching @var{regexp}.
40112 For each script, this command prints its name as specified in the objfile,
40113 and the full path if known.
40114 @xref{dotdebug_gdb_scripts section}.
40116 @kindex maint print statistics
40117 @cindex bcache statistics
40118 @item maint print statistics
40119 This command prints, for each object file in the program, various data
40120 about that object file followed by the byte cache (@dfn{bcache})
40121 statistics for the object file. The objfile data includes the number
40122 of minimal, partial, full, and stabs symbols, the number of types
40123 defined by the objfile, the number of as yet unexpanded psym tables,
40124 the number of line tables and string tables, and the amount of memory
40125 used by the various tables. The bcache statistics include the counts,
40126 sizes, and counts of duplicates of all and unique objects, max,
40127 average, and median entry size, total memory used and its overhead and
40128 savings, and various measures of the hash table size and chain
40131 @kindex maint print target-stack
40132 @cindex target stack description
40133 @item maint print target-stack
40134 A @dfn{target} is an interface between the debugger and a particular
40135 kind of file or process. Targets can be stacked in @dfn{strata},
40136 so that more than one target can potentially respond to a request.
40137 In particular, memory accesses will walk down the stack of targets
40138 until they find a target that is interested in handling that particular
40141 This command prints a short description of each layer that was pushed on
40142 the @dfn{target stack}, starting from the top layer down to the bottom one.
40144 @kindex maint print type
40145 @cindex type chain of a data type
40146 @item maint print type @var{expr}
40147 Print the type chain for a type specified by @var{expr}. The argument
40148 can be either a type name or a symbol. If it is a symbol, the type of
40149 that symbol is described. The type chain produced by this command is
40150 a recursive definition of the data type as stored in @value{GDBN}'s
40151 data structures, including its flags and contained types.
40153 @kindex maint selftest
40155 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
40156 Run any self tests that were compiled in to @value{GDBN}. This will
40157 print a message showing how many tests were run, and how many failed.
40158 If a @var{filter} is passed, only the tests with @var{filter} in their
40159 name will be ran. If @code{-verbose} is passed, the self tests can be
40162 @kindex maint set selftest verbose
40163 @kindex maint show selftest verbose
40165 @item maint set selftest verbose
40166 @item maint show selftest verbose
40167 Control whether self tests are run verbosely or not.
40169 @kindex maint info selftests
40171 @item maint info selftests
40172 List the selftests compiled in to @value{GDBN}.
40174 @kindex maint set dwarf always-disassemble
40175 @kindex maint show dwarf always-disassemble
40176 @item maint set dwarf always-disassemble
40177 @item maint show dwarf always-disassemble
40178 Control the behavior of @code{info address} when using DWARF debugging
40181 The default is @code{off}, which means that @value{GDBN} should try to
40182 describe a variable's location in an easily readable format. When
40183 @code{on}, @value{GDBN} will instead display the DWARF location
40184 expression in an assembly-like format. Note that some locations are
40185 too complex for @value{GDBN} to describe simply; in this case you will
40186 always see the disassembly form.
40188 Here is an example of the resulting disassembly:
40191 (gdb) info addr argc
40192 Symbol "argc" is a complex DWARF expression:
40196 For more information on these expressions, see
40197 @uref{http://www.dwarfstd.org/, the DWARF standard}.
40199 @kindex maint set dwarf max-cache-age
40200 @kindex maint show dwarf max-cache-age
40201 @item maint set dwarf max-cache-age
40202 @itemx maint show dwarf max-cache-age
40203 Control the DWARF compilation unit cache.
40205 @cindex DWARF compilation units cache
40206 In object files with inter-compilation-unit references, such as those
40207 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
40208 reader needs to frequently refer to previously read compilation units.
40209 This setting controls how long a compilation unit will remain in the
40210 cache if it is not referenced. A higher limit means that cached
40211 compilation units will be stored in memory longer, and more total
40212 memory will be used. Setting it to zero disables caching, which will
40213 slow down @value{GDBN} startup, but reduce memory consumption.
40215 @kindex maint set dwarf unwinders
40216 @kindex maint show dwarf unwinders
40217 @item maint set dwarf unwinders
40218 @itemx maint show dwarf unwinders
40219 Control use of the DWARF frame unwinders.
40221 @cindex DWARF frame unwinders
40222 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
40223 frame unwinders to build the backtrace. Many of these targets will
40224 also have a second mechanism for building the backtrace for use in
40225 cases where DWARF information is not available, this second mechanism
40226 is often an analysis of a function's prologue.
40228 In order to extend testing coverage of the second level stack
40229 unwinding mechanisms it is helpful to be able to disable the DWARF
40230 stack unwinders, this can be done with this switch.
40232 In normal use of @value{GDBN} disabling the DWARF unwinders is not
40233 advisable, there are cases that are better handled through DWARF than
40234 prologue analysis, and the debug experience is likely to be better
40235 with the DWARF frame unwinders enabled.
40237 If DWARF frame unwinders are not supported for a particular target
40238 architecture, then enabling this flag does not cause them to be used.
40240 @kindex maint set worker-threads
40241 @kindex maint show worker-threads
40242 @item maint set worker-threads
40243 @item maint show worker-threads
40244 Control the number of worker threads that may be used by @value{GDBN}.
40245 On capable hosts, @value{GDBN} may use multiple threads to speed up
40246 certain CPU-intensive operations, such as demangling symbol names.
40247 While the number of threads used by @value{GDBN} may vary, this
40248 command can be used to set an upper bound on this number. The default
40249 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
40250 number. Note that this only controls worker threads started by
40251 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
40254 @kindex maint set profile
40255 @kindex maint show profile
40256 @cindex profiling GDB
40257 @item maint set profile
40258 @itemx maint show profile
40259 Control profiling of @value{GDBN}.
40261 Profiling will be disabled until you use the @samp{maint set profile}
40262 command to enable it. When you enable profiling, the system will begin
40263 collecting timing and execution count data; when you disable profiling or
40264 exit @value{GDBN}, the results will be written to a log file. Remember that
40265 if you use profiling, @value{GDBN} will overwrite the profiling log file
40266 (often called @file{gmon.out}). If you have a record of important profiling
40267 data in a @file{gmon.out} file, be sure to move it to a safe location.
40269 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
40270 compiled with the @samp{-pg} compiler option.
40272 @kindex maint set show-debug-regs
40273 @kindex maint show show-debug-regs
40274 @cindex hardware debug registers
40275 @item maint set show-debug-regs
40276 @itemx maint show show-debug-regs
40277 Control whether to show variables that mirror the hardware debug
40278 registers. Use @code{on} to enable, @code{off} to disable. If
40279 enabled, the debug registers values are shown when @value{GDBN} inserts or
40280 removes a hardware breakpoint or watchpoint, and when the inferior
40281 triggers a hardware-assisted breakpoint or watchpoint.
40283 @kindex maint set show-all-tib
40284 @kindex maint show show-all-tib
40285 @item maint set show-all-tib
40286 @itemx maint show show-all-tib
40287 Control whether to show all non zero areas within a 1k block starting
40288 at thread local base, when using the @samp{info w32 thread-information-block}
40291 @kindex maint set target-async
40292 @kindex maint show target-async
40293 @item maint set target-async
40294 @itemx maint show target-async
40295 This controls whether @value{GDBN} targets operate in synchronous or
40296 asynchronous mode (@pxref{Background Execution}). Normally the
40297 default is asynchronous, if it is available; but this can be changed
40298 to more easily debug problems occurring only in synchronous mode.
40300 @kindex maint set target-non-stop @var{mode} [on|off|auto]
40301 @kindex maint show target-non-stop
40302 @item maint set target-non-stop
40303 @itemx maint show target-non-stop
40305 This controls whether @value{GDBN} targets always operate in non-stop
40306 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
40307 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
40308 if supported by the target.
40311 @item maint set target-non-stop auto
40312 This is the default mode. @value{GDBN} controls the target in
40313 non-stop mode if the target supports it.
40315 @item maint set target-non-stop on
40316 @value{GDBN} controls the target in non-stop mode even if the target
40317 does not indicate support.
40319 @item maint set target-non-stop off
40320 @value{GDBN} does not control the target in non-stop mode even if the
40321 target supports it.
40324 @kindex maint set tui-resize-message
40325 @kindex maint show tui-resize-message
40326 @item maint set tui-resize-message
40327 @item maint show tui-resize-message
40328 Control whether @value{GDBN} displays a message each time the terminal
40329 is resized when in TUI mode. The default is @code{off}, which means
40330 that @value{GDBN} is silent during resizes. When @code{on},
40331 @value{GDBN} will display a message after a resize is completed; the
40332 message will include a number indicating how many times the terminal
40333 has been resized. This setting is intended for use by the test suite,
40334 where it would otherwise be difficult to determine when a resize and
40335 refresh has been completed.
40337 @kindex maint set per-command
40338 @kindex maint show per-command
40339 @item maint set per-command
40340 @itemx maint show per-command
40341 @cindex resources used by commands
40343 @value{GDBN} can display the resources used by each command.
40344 This is useful in debugging performance problems.
40347 @item maint set per-command space [on|off]
40348 @itemx maint show per-command space
40349 Enable or disable the printing of the memory used by GDB for each command.
40350 If enabled, @value{GDBN} will display how much memory each command
40351 took, following the command's own output.
40352 This can also be requested by invoking @value{GDBN} with the
40353 @option{--statistics} command-line switch (@pxref{Mode Options}).
40355 @item maint set per-command time [on|off]
40356 @itemx maint show per-command time
40357 Enable or disable the printing of the execution time of @value{GDBN}
40359 If enabled, @value{GDBN} will display how much time it
40360 took to execute each command, following the command's own output.
40361 Both CPU time and wallclock time are printed.
40362 Printing both is useful when trying to determine whether the cost is
40363 CPU or, e.g., disk/network latency.
40364 Note that the CPU time printed is for @value{GDBN} only, it does not include
40365 the execution time of the inferior because there's no mechanism currently
40366 to compute how much time was spent by @value{GDBN} and how much time was
40367 spent by the program been debugged.
40368 This can also be requested by invoking @value{GDBN} with the
40369 @option{--statistics} command-line switch (@pxref{Mode Options}).
40371 @item maint set per-command symtab [on|off]
40372 @itemx maint show per-command symtab
40373 Enable or disable the printing of basic symbol table statistics
40375 If enabled, @value{GDBN} will display the following information:
40379 number of symbol tables
40381 number of primary symbol tables
40383 number of blocks in the blockvector
40387 @kindex maint set check-libthread-db
40388 @kindex maint show check-libthread-db
40389 @item maint set check-libthread-db [on|off]
40390 @itemx maint show check-libthread-db
40391 Control whether @value{GDBN} should run integrity checks on inferior
40392 specific thread debugging libraries as they are loaded. The default
40393 is not to perform such checks. If any check fails @value{GDBN} will
40394 unload the library and continue searching for a suitable candidate as
40395 described in @ref{set libthread-db-search-path}. For more information
40396 about the tests, see @ref{maint check libthread-db}.
40398 @kindex maint set gnu-source-highlight enabled
40399 @kindex maint show gnu-source-highlight enabled
40400 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
40401 @itemx maint show gnu-source-highlight enabled
40402 Control whether @value{GDBN} should use the GNU Source Highlight
40403 library for applying styling to source code (@pxref{Output Styling}).
40404 This will be @samp{on} by default if the GNU Source Highlight library
40405 is available. If the GNU Source Highlight library is not available,
40406 then this will be @samp{off} by default, and attempting to change this
40407 value to @samp{on} will give an error.
40409 If the GNU Source Highlight library is not being used, then
40410 @value{GDBN} will use the Python Pygments package for source code
40411 styling, if it is available.
40413 This option is useful for debugging @value{GDBN}'s use of the Pygments
40414 library when @value{GDBN} is linked against the GNU Source Highlight
40417 @kindex maint space
40418 @cindex memory used by commands
40419 @item maint space @var{value}
40420 An alias for @code{maint set per-command space}.
40421 A non-zero value enables it, zero disables it.
40424 @cindex time of command execution
40425 @item maint time @var{value}
40426 An alias for @code{maint set per-command time}.
40427 A non-zero value enables it, zero disables it.
40429 @kindex maint translate-address
40430 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
40431 Find the symbol stored at the location specified by the address
40432 @var{addr} and an optional section name @var{section}. If found,
40433 @value{GDBN} prints the name of the closest symbol and an offset from
40434 the symbol's location to the specified address. This is similar to
40435 the @code{info address} command (@pxref{Symbols}), except that this
40436 command also allows to find symbols in other sections.
40438 If section was not specified, the section in which the symbol was found
40439 is also printed. For dynamically linked executables, the name of
40440 executable or shared library containing the symbol is printed as well.
40442 @kindex maint test-options
40443 @item maint test-options require-delimiter
40444 @itemx maint test-options unknown-is-error
40445 @itemx maint test-options unknown-is-operand
40446 These commands are used by the testsuite to validate the command
40447 options framework. The @code{require-delimiter} variant requires a
40448 double-dash delimiter to indicate end of options. The
40449 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
40450 @code{unknown-is-error} variant throws an error on unknown option,
40451 while @code{unknown-is-operand} treats unknown options as the start of
40452 the command's operands. When run, the commands output the result of
40453 the processed options. When completed, the commands store the
40454 internal result of completion in a variable exposed by the @code{maint
40455 show test-options-completion-result} command.
40457 @kindex maint show test-options-completion-result
40458 @item maint show test-options-completion-result
40459 Shows the result of completing the @code{maint test-options}
40460 subcommands. This is used by the testsuite to validate completion
40461 support in the command options framework.
40463 @kindex maint set test-settings
40464 @kindex maint show test-settings
40465 @item maint set test-settings @var{kind}
40466 @itemx maint show test-settings @var{kind}
40467 These are representative commands for each @var{kind} of setting type
40468 @value{GDBN} supports. They are used by the testsuite for exercising
40469 the settings infrastructure.
40471 @kindex maint set backtrace-on-fatal-signal
40472 @kindex maint show backtrace-on-fatal-signal
40473 @item maint set backtrace-on-fatal-signal [on|off]
40474 @itemx maint show backtrace-on-fatal-signal
40475 When this setting is @code{on}, if @value{GDBN} itself terminates with
40476 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40477 printed to the standard error stream. This backtrace can be used to
40478 help diagnose crashes within @value{GDBN} in situations where a user
40479 is unable to share a corefile with the @value{GDBN} developers.
40481 If the functionality to provide this backtrace is not available for
40482 the platform on which GDB is running then this feature will be
40483 @code{off} by default, and attempting to turn this feature on will
40486 For platforms that do support creating the backtrace this feature is
40487 @code{on} by default.
40490 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40491 Like the @code{with} command, but works with @code{maintenance set}
40492 variables. This is used by the testsuite to exercise the @code{with}
40493 command's infrastructure.
40497 The following command is useful for non-interactive invocations of
40498 @value{GDBN}, such as in the test suite.
40501 @item set watchdog @var{nsec}
40502 @kindex set watchdog
40503 @cindex watchdog timer
40504 @cindex timeout for commands
40505 Set the maximum number of seconds @value{GDBN} will wait for the
40506 target operation to finish. If this time expires, @value{GDBN}
40507 reports and error and the command is aborted.
40509 @item show watchdog
40510 Show the current setting of the target wait timeout.
40513 @node Remote Protocol
40514 @appendix @value{GDBN} Remote Serial Protocol
40519 * Stop Reply Packets::
40520 * General Query Packets::
40521 * Architecture-Specific Protocol Details::
40522 * Tracepoint Packets::
40523 * Host I/O Packets::
40525 * Notification Packets::
40526 * Remote Non-Stop::
40527 * Packet Acknowledgment::
40529 * File-I/O Remote Protocol Extension::
40530 * Library List Format::
40531 * Library List Format for SVR4 Targets::
40532 * Memory Map Format::
40533 * Thread List Format::
40534 * Traceframe Info Format::
40535 * Branch Trace Format::
40536 * Branch Trace Configuration Format::
40542 There may be occasions when you need to know something about the
40543 protocol---for example, if there is only one serial port to your target
40544 machine, you might want your program to do something special if it
40545 recognizes a packet meant for @value{GDBN}.
40547 In the examples below, @samp{->} and @samp{<-} are used to indicate
40548 transmitted and received data, respectively.
40550 @cindex protocol, @value{GDBN} remote serial
40551 @cindex serial protocol, @value{GDBN} remote
40552 @cindex remote serial protocol
40553 All @value{GDBN} commands and responses (other than acknowledgments
40554 and notifications, see @ref{Notification Packets}) are sent as a
40555 @var{packet}. A @var{packet} is introduced with the character
40556 @samp{$}, the actual @var{packet-data}, and the terminating character
40557 @samp{#} followed by a two-digit @var{checksum}:
40560 @code{$}@var{packet-data}@code{#}@var{checksum}
40564 @cindex checksum, for @value{GDBN} remote
40566 The two-digit @var{checksum} is computed as the modulo 256 sum of all
40567 characters between the leading @samp{$} and the trailing @samp{#} (an
40568 eight bit unsigned checksum).
40570 Implementors should note that prior to @value{GDBN} 5.0 the protocol
40571 specification also included an optional two-digit @var{sequence-id}:
40574 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
40577 @cindex sequence-id, for @value{GDBN} remote
40579 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
40580 has never output @var{sequence-id}s. Stubs that handle packets added
40581 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
40583 When either the host or the target machine receives a packet, the first
40584 response expected is an acknowledgment: either @samp{+} (to indicate
40585 the package was received correctly) or @samp{-} (to request
40589 -> @code{$}@var{packet-data}@code{#}@var{checksum}
40594 The @samp{+}/@samp{-} acknowledgments can be disabled
40595 once a connection is established.
40596 @xref{Packet Acknowledgment}, for details.
40598 The host (@value{GDBN}) sends @var{command}s, and the target (the
40599 debugging stub incorporated in your program) sends a @var{response}. In
40600 the case of step and continue @var{command}s, the response is only sent
40601 when the operation has completed, and the target has again stopped all
40602 threads in all attached processes. This is the default all-stop mode
40603 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
40604 execution mode; see @ref{Remote Non-Stop}, for details.
40606 @var{packet-data} consists of a sequence of characters with the
40607 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
40610 @cindex remote protocol, field separator
40611 Fields within the packet should be separated using @samp{,} @samp{;} or
40612 @samp{:}. Except where otherwise noted all numbers are represented in
40613 @sc{hex} with leading zeros suppressed.
40615 Implementors should note that prior to @value{GDBN} 5.0, the character
40616 @samp{:} could not appear as the third character in a packet (as it
40617 would potentially conflict with the @var{sequence-id}).
40619 @cindex remote protocol, binary data
40620 @anchor{Binary Data}
40621 Binary data in most packets is encoded either as two hexadecimal
40622 digits per byte of binary data. This allowed the traditional remote
40623 protocol to work over connections which were only seven-bit clean.
40624 Some packets designed more recently assume an eight-bit clean
40625 connection, and use a more efficient encoding to send and receive
40628 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
40629 as an escape character. Any escaped byte is transmitted as the escape
40630 character followed by the original character XORed with @code{0x20}.
40631 For example, the byte @code{0x7d} would be transmitted as the two
40632 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
40633 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
40634 @samp{@}}) must always be escaped. Responses sent by the stub
40635 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
40636 is not interpreted as the start of a run-length encoded sequence
40639 Response @var{data} can be run-length encoded to save space.
40640 Run-length encoding replaces runs of identical characters with one
40641 instance of the repeated character, followed by a @samp{*} and a
40642 repeat count. The repeat count is itself sent encoded, to avoid
40643 binary characters in @var{data}: a value of @var{n} is sent as
40644 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
40645 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
40646 code 32) for a repeat count of 3. (This is because run-length
40647 encoding starts to win for counts 3 or more.) Thus, for example,
40648 @samp{0* } is a run-length encoding of ``0000'': the space character
40649 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
40652 The printable characters @samp{#} and @samp{$} or with a numeric value
40653 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
40654 seven repeats (@samp{$}) can be expanded using a repeat count of only
40655 five (@samp{"}). For example, @samp{00000000} can be encoded as
40658 The error response returned for some packets includes a two character
40659 error number. That number is not well defined.
40661 @cindex empty response, for unsupported packets
40662 For any @var{command} not supported by the stub, an empty response
40663 (@samp{$#00}) should be returned. That way it is possible to extend the
40664 protocol. A newer @value{GDBN} can tell if a packet is supported based
40667 At a minimum, a stub is required to support the @samp{?} command to
40668 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
40669 commands for register access, and the @samp{m} and @samp{M} commands
40670 for memory access. Stubs that only control single-threaded targets
40671 can implement run control with the @samp{c} (continue) command, and if
40672 the target architecture supports hardware-assisted single-stepping,
40673 the @samp{s} (step) command. Stubs that support multi-threading
40674 targets should support the @samp{vCont} command. All other commands
40680 The following table provides a complete list of all currently defined
40681 @var{command}s and their corresponding response @var{data}.
40682 @xref{File-I/O Remote Protocol Extension}, for details about the File
40683 I/O extension of the remote protocol.
40685 Each packet's description has a template showing the packet's overall
40686 syntax, followed by an explanation of the packet's meaning. We
40687 include spaces in some of the templates for clarity; these are not
40688 part of the packet's syntax. No @value{GDBN} packet uses spaces to
40689 separate its components. For example, a template like @samp{foo
40690 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
40691 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
40692 @var{baz}. @value{GDBN} does not transmit a space character between the
40693 @samp{foo} and the @var{bar}, or between the @var{bar} and the
40696 @cindex @var{thread-id}, in remote protocol
40697 @anchor{thread-id syntax}
40698 Several packets and replies include a @var{thread-id} field to identify
40699 a thread. Normally these are positive numbers with a target-specific
40700 interpretation, formatted as big-endian hex strings. A @var{thread-id}
40701 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
40704 In addition, the remote protocol supports a multiprocess feature in
40705 which the @var{thread-id} syntax is extended to optionally include both
40706 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
40707 The @var{pid} (process) and @var{tid} (thread) components each have the
40708 format described above: a positive number with target-specific
40709 interpretation formatted as a big-endian hex string, literal @samp{-1}
40710 to indicate all processes or threads (respectively), or @samp{0} to
40711 indicate an arbitrary process or thread. Specifying just a process, as
40712 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
40713 error to specify all processes but a specific thread, such as
40714 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
40715 for those packets and replies explicitly documented to include a process
40716 ID, rather than a @var{thread-id}.
40718 The multiprocess @var{thread-id} syntax extensions are only used if both
40719 @value{GDBN} and the stub report support for the @samp{multiprocess}
40720 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
40723 Note that all packet forms beginning with an upper- or lower-case
40724 letter, other than those described here, are reserved for future use.
40726 Here are the packet descriptions.
40731 @cindex @samp{!} packet
40732 @anchor{extended mode}
40733 Enable extended mode. In extended mode, the remote server is made
40734 persistent. The @samp{R} packet is used to restart the program being
40740 The remote target both supports and has enabled extended mode.
40744 @cindex @samp{?} packet
40746 This is sent when connection is first established to query the reason
40747 the target halted. The reply is the same as for step and continue.
40748 This packet has a special interpretation when the target is in
40749 non-stop mode; see @ref{Remote Non-Stop}.
40752 @xref{Stop Reply Packets}, for the reply specifications.
40754 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
40755 @cindex @samp{A} packet
40756 Initialized @code{argv[]} array passed into program. @var{arglen}
40757 specifies the number of bytes in the hex encoded byte stream
40758 @var{arg}. See @code{gdbserver} for more details.
40763 The arguments were set.
40769 @cindex @samp{b} packet
40770 (Don't use this packet; its behavior is not well-defined.)
40771 Change the serial line speed to @var{baud}.
40773 JTC: @emph{When does the transport layer state change? When it's
40774 received, or after the ACK is transmitted. In either case, there are
40775 problems if the command or the acknowledgment packet is dropped.}
40777 Stan: @emph{If people really wanted to add something like this, and get
40778 it working for the first time, they ought to modify ser-unix.c to send
40779 some kind of out-of-band message to a specially-setup stub and have the
40780 switch happen "in between" packets, so that from remote protocol's point
40781 of view, nothing actually happened.}
40783 @item B @var{addr},@var{mode}
40784 @cindex @samp{B} packet
40785 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
40786 breakpoint at @var{addr}.
40788 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
40789 (@pxref{insert breakpoint or watchpoint packet}).
40791 @cindex @samp{bc} packet
40794 Backward continue. Execute the target system in reverse. No parameter.
40795 @xref{Reverse Execution}, for more information.
40798 @xref{Stop Reply Packets}, for the reply specifications.
40800 @cindex @samp{bs} packet
40803 Backward single step. Execute one instruction in reverse. No parameter.
40804 @xref{Reverse Execution}, for more information.
40807 @xref{Stop Reply Packets}, for the reply specifications.
40809 @item c @r{[}@var{addr}@r{]}
40810 @cindex @samp{c} packet
40811 Continue at @var{addr}, which is the address to resume. If @var{addr}
40812 is omitted, resume at current address.
40814 This packet is deprecated for multi-threading support. @xref{vCont
40818 @xref{Stop Reply Packets}, for the reply specifications.
40820 @item C @var{sig}@r{[};@var{addr}@r{]}
40821 @cindex @samp{C} packet
40822 Continue with signal @var{sig} (hex signal number). If
40823 @samp{;@var{addr}} is omitted, resume at same address.
40825 This packet is deprecated for multi-threading support. @xref{vCont
40829 @xref{Stop Reply Packets}, for the reply specifications.
40832 @cindex @samp{d} packet
40835 Don't use this packet; instead, define a general set packet
40836 (@pxref{General Query Packets}).
40840 @cindex @samp{D} packet
40841 The first form of the packet is used to detach @value{GDBN} from the
40842 remote system. It is sent to the remote target
40843 before @value{GDBN} disconnects via the @code{detach} command.
40845 The second form, including a process ID, is used when multiprocess
40846 protocol extensions are enabled (@pxref{multiprocess extensions}), to
40847 detach only a specific process. The @var{pid} is specified as a
40848 big-endian hex string.
40858 @item F @var{RC},@var{EE},@var{CF};@var{XX}
40859 @cindex @samp{F} packet
40860 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
40861 This is part of the File-I/O protocol extension. @xref{File-I/O
40862 Remote Protocol Extension}, for the specification.
40865 @anchor{read registers packet}
40866 @cindex @samp{g} packet
40867 Read general registers.
40871 @item @var{XX@dots{}}
40872 Each byte of register data is described by two hex digits. The bytes
40873 with the register are transmitted in target byte order. The size of
40874 each register and their position within the @samp{g} packet are
40875 determined by the @value{GDBN} internal gdbarch functions
40876 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
40878 When reading registers from a trace frame (@pxref{Analyze Collected
40879 Data,,Using the Collected Data}), the stub may also return a string of
40880 literal @samp{x}'s in place of the register data digits, to indicate
40881 that the corresponding register has not been collected, thus its value
40882 is unavailable. For example, for an architecture with 4 registers of
40883 4 bytes each, the following reply indicates to @value{GDBN} that
40884 registers 0 and 2 have not been collected, while registers 1 and 3
40885 have been collected, and both have zero value:
40889 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
40896 @item G @var{XX@dots{}}
40897 @cindex @samp{G} packet
40898 Write general registers. @xref{read registers packet}, for a
40899 description of the @var{XX@dots{}} data.
40909 @item H @var{op} @var{thread-id}
40910 @cindex @samp{H} packet
40911 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
40912 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
40913 should be @samp{c} for step and continue operations (note that this
40914 is deprecated, supporting the @samp{vCont} command is a better
40915 option), and @samp{g} for other operations. The thread designator
40916 @var{thread-id} has the format and interpretation described in
40917 @ref{thread-id syntax}.
40928 @c 'H': How restrictive (or permissive) is the thread model. If a
40929 @c thread is selected and stopped, are other threads allowed
40930 @c to continue to execute? As I mentioned above, I think the
40931 @c semantics of each command when a thread is selected must be
40932 @c described. For example:
40934 @c 'g': If the stub supports threads and a specific thread is
40935 @c selected, returns the register block from that thread;
40936 @c otherwise returns current registers.
40938 @c 'G' If the stub supports threads and a specific thread is
40939 @c selected, sets the registers of the register block of
40940 @c that thread; otherwise sets current registers.
40942 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
40943 @anchor{cycle step packet}
40944 @cindex @samp{i} packet
40945 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
40946 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
40947 step starting at that address.
40950 @cindex @samp{I} packet
40951 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
40955 @cindex @samp{k} packet
40958 The exact effect of this packet is not specified.
40960 For a bare-metal target, it may power cycle or reset the target
40961 system. For that reason, the @samp{k} packet has no reply.
40963 For a single-process target, it may kill that process if possible.
40965 A multiple-process target may choose to kill just one process, or all
40966 that are under @value{GDBN}'s control. For more precise control, use
40967 the vKill packet (@pxref{vKill packet}).
40969 If the target system immediately closes the connection in response to
40970 @samp{k}, @value{GDBN} does not consider the lack of packet
40971 acknowledgment to be an error, and assumes the kill was successful.
40973 If connected using @kbd{target extended-remote}, and the target does
40974 not close the connection in response to a kill request, @value{GDBN}
40975 probes the target state as if a new connection was opened
40976 (@pxref{? packet}).
40978 @item m @var{addr},@var{length}
40979 @cindex @samp{m} packet
40980 Read @var{length} addressable memory units starting at address @var{addr}
40981 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
40982 any particular boundary.
40984 The stub need not use any particular size or alignment when gathering
40985 data from memory for the response; even if @var{addr} is word-aligned
40986 and @var{length} is a multiple of the word size, the stub is free to
40987 use byte accesses, or not. For this reason, this packet may not be
40988 suitable for accessing memory-mapped I/O devices.
40989 @cindex alignment of remote memory accesses
40990 @cindex size of remote memory accesses
40991 @cindex memory, alignment and size of remote accesses
40995 @item @var{XX@dots{}}
40996 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
40997 The reply may contain fewer addressable memory units than requested if the
40998 server was able to read only part of the region of memory.
41003 @item M @var{addr},@var{length}:@var{XX@dots{}}
41004 @cindex @samp{M} packet
41005 Write @var{length} addressable memory units starting at address @var{addr}
41006 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
41007 byte is transmitted as a two-digit hexadecimal number.
41014 for an error (this includes the case where only part of the data was
41019 @cindex @samp{p} packet
41020 Read the value of register @var{n}; @var{n} is in hex.
41021 @xref{read registers packet}, for a description of how the returned
41022 register value is encoded.
41026 @item @var{XX@dots{}}
41027 the register's value
41031 Indicating an unrecognized @var{query}.
41034 @item P @var{n@dots{}}=@var{r@dots{}}
41035 @anchor{write register packet}
41036 @cindex @samp{P} packet
41037 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
41038 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
41039 digits for each byte in the register (target byte order).
41049 @item q @var{name} @var{params}@dots{}
41050 @itemx Q @var{name} @var{params}@dots{}
41051 @cindex @samp{q} packet
41052 @cindex @samp{Q} packet
41053 General query (@samp{q}) and set (@samp{Q}). These packets are
41054 described fully in @ref{General Query Packets}.
41057 @cindex @samp{r} packet
41058 Reset the entire system.
41060 Don't use this packet; use the @samp{R} packet instead.
41063 @cindex @samp{R} packet
41064 Restart the program being debugged. The @var{XX}, while needed, is ignored.
41065 This packet is only available in extended mode (@pxref{extended mode}).
41067 The @samp{R} packet has no reply.
41069 @item s @r{[}@var{addr}@r{]}
41070 @cindex @samp{s} packet
41071 Single step, resuming at @var{addr}. If
41072 @var{addr} is omitted, resume at same address.
41074 This packet is deprecated for multi-threading support. @xref{vCont
41078 @xref{Stop Reply Packets}, for the reply specifications.
41080 @item S @var{sig}@r{[};@var{addr}@r{]}
41081 @anchor{step with signal packet}
41082 @cindex @samp{S} packet
41083 Step with signal. This is analogous to the @samp{C} packet, but
41084 requests a single-step, rather than a normal resumption of execution.
41086 This packet is deprecated for multi-threading support. @xref{vCont
41090 @xref{Stop Reply Packets}, for the reply specifications.
41092 @item t @var{addr}:@var{PP},@var{MM}
41093 @cindex @samp{t} packet
41094 Search backwards starting at address @var{addr} for a match with pattern
41095 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
41096 There must be at least 3 digits in @var{addr}.
41098 @item T @var{thread-id}
41099 @cindex @samp{T} packet
41100 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
41105 thread is still alive
41111 Packets starting with @samp{v} are identified by a multi-letter name,
41112 up to the first @samp{;} or @samp{?} (or the end of the packet).
41114 @item vAttach;@var{pid}
41115 @cindex @samp{vAttach} packet
41116 Attach to a new process with the specified process ID @var{pid}.
41117 The process ID is a
41118 hexadecimal integer identifying the process. In all-stop mode, all
41119 threads in the attached process are stopped; in non-stop mode, it may be
41120 attached without being stopped if that is supported by the target.
41122 @c In non-stop mode, on a successful vAttach, the stub should set the
41123 @c current thread to a thread of the newly-attached process. After
41124 @c attaching, GDB queries for the attached process's thread ID with qC.
41125 @c Also note that, from a user perspective, whether or not the
41126 @c target is stopped on attach in non-stop mode depends on whether you
41127 @c use the foreground or background version of the attach command, not
41128 @c on what vAttach does; GDB does the right thing with respect to either
41129 @c stopping or restarting threads.
41131 This packet is only available in extended mode (@pxref{extended mode}).
41137 @item @r{Any stop packet}
41138 for success in all-stop mode (@pxref{Stop Reply Packets})
41140 for success in non-stop mode (@pxref{Remote Non-Stop})
41143 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
41144 @cindex @samp{vCont} packet
41145 @anchor{vCont packet}
41146 Resume the inferior, specifying different actions for each thread.
41148 For each inferior thread, the leftmost action with a matching
41149 @var{thread-id} is applied. Threads that don't match any action
41150 remain in their current state. Thread IDs are specified using the
41151 syntax described in @ref{thread-id syntax}. If multiprocess
41152 extensions (@pxref{multiprocess extensions}) are supported, actions
41153 can be specified to match all threads in a process by using the
41154 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
41155 @var{thread-id} matches all threads. Specifying no actions is an
41158 Currently supported actions are:
41164 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
41168 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
41171 @item r @var{start},@var{end}
41172 Step once, and then keep stepping as long as the thread stops at
41173 addresses between @var{start} (inclusive) and @var{end} (exclusive).
41174 The remote stub reports a stop reply when either the thread goes out
41175 of the range or is stopped due to an unrelated reason, such as hitting
41176 a breakpoint. @xref{range stepping}.
41178 If the range is empty (@var{start} == @var{end}), then the action
41179 becomes equivalent to the @samp{s} action. In other words,
41180 single-step once, and report the stop (even if the stepped instruction
41181 jumps to @var{start}).
41183 (A stop reply may be sent at any point even if the PC is still within
41184 the stepping range; for example, it is valid to implement this packet
41185 in a degenerate way as a single instruction step operation.)
41189 The optional argument @var{addr} normally associated with the
41190 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
41191 not supported in @samp{vCont}.
41193 The @samp{t} action is only relevant in non-stop mode
41194 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
41195 A stop reply should be generated for any affected thread not already stopped.
41196 When a thread is stopped by means of a @samp{t} action,
41197 the corresponding stop reply should indicate that the thread has stopped with
41198 signal @samp{0}, regardless of whether the target uses some other signal
41199 as an implementation detail.
41201 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
41202 @samp{r} actions for threads that are already running. Conversely,
41203 the server must ignore @samp{t} actions for threads that are already
41206 @emph{Note:} In non-stop mode, a thread is considered running until
41207 @value{GDBN} acknowledges an asynchronous stop notification for it with
41208 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
41210 The stub must support @samp{vCont} if it reports support for
41211 multiprocess extensions (@pxref{multiprocess extensions}).
41214 @xref{Stop Reply Packets}, for the reply specifications.
41217 @cindex @samp{vCont?} packet
41218 Request a list of actions supported by the @samp{vCont} packet.
41222 @item vCont@r{[};@var{action}@dots{}@r{]}
41223 The @samp{vCont} packet is supported. Each @var{action} is a supported
41224 command in the @samp{vCont} packet.
41226 The @samp{vCont} packet is not supported.
41229 @anchor{vCtrlC packet}
41231 @cindex @samp{vCtrlC} packet
41232 Interrupt remote target as if a control-C was pressed on the remote
41233 terminal. This is the equivalent to reacting to the @code{^C}
41234 (@samp{\003}, the control-C character) character in all-stop mode
41235 while the target is running, except this works in non-stop mode.
41236 @xref{interrupting remote targets}, for more info on the all-stop
41247 @item vFile:@var{operation}:@var{parameter}@dots{}
41248 @cindex @samp{vFile} packet
41249 Perform a file operation on the target system. For details,
41250 see @ref{Host I/O Packets}.
41252 @item vFlashErase:@var{addr},@var{length}
41253 @cindex @samp{vFlashErase} packet
41254 Direct the stub to erase @var{length} bytes of flash starting at
41255 @var{addr}. The region may enclose any number of flash blocks, but
41256 its start and end must fall on block boundaries, as indicated by the
41257 flash block size appearing in the memory map (@pxref{Memory Map
41258 Format}). @value{GDBN} groups flash memory programming operations
41259 together, and sends a @samp{vFlashDone} request after each group; the
41260 stub is allowed to delay erase operation until the @samp{vFlashDone}
41261 packet is received.
41271 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
41272 @cindex @samp{vFlashWrite} packet
41273 Direct the stub to write data to flash address @var{addr}. The data
41274 is passed in binary form using the same encoding as for the @samp{X}
41275 packet (@pxref{Binary Data}). The memory ranges specified by
41276 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
41277 not overlap, and must appear in order of increasing addresses
41278 (although @samp{vFlashErase} packets for higher addresses may already
41279 have been received; the ordering is guaranteed only between
41280 @samp{vFlashWrite} packets). If a packet writes to an address that was
41281 neither erased by a preceding @samp{vFlashErase} packet nor by some other
41282 target-specific method, the results are unpredictable.
41290 for vFlashWrite addressing non-flash memory
41296 @cindex @samp{vFlashDone} packet
41297 Indicate to the stub that flash programming operation is finished.
41298 The stub is permitted to delay or batch the effects of a group of
41299 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
41300 @samp{vFlashDone} packet is received. The contents of the affected
41301 regions of flash memory are unpredictable until the @samp{vFlashDone}
41302 request is completed.
41304 @item vKill;@var{pid}
41305 @cindex @samp{vKill} packet
41306 @anchor{vKill packet}
41307 Kill the process with the specified process ID @var{pid}, which is a
41308 hexadecimal integer identifying the process. This packet is used in
41309 preference to @samp{k} when multiprocess protocol extensions are
41310 supported; see @ref{multiprocess extensions}.
41320 @item vMustReplyEmpty
41321 @cindex @samp{vMustReplyEmpty} packet
41322 The correct reply to an unknown @samp{v} packet is to return the empty
41323 string, however, some older versions of @command{gdbserver} would
41324 incorrectly return @samp{OK} for unknown @samp{v} packets.
41326 The @samp{vMustReplyEmpty} is used as a feature test to check how
41327 @command{gdbserver} handles unknown packets, it is important that this
41328 packet be handled in the same way as other unknown @samp{v} packets.
41329 If this packet is handled differently to other unknown @samp{v}
41330 packets then it is possible that @value{GDBN} may run into problems in
41331 other areas, specifically around use of @samp{vFile:setfs:}.
41333 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
41334 @cindex @samp{vRun} packet
41335 Run the program @var{filename}, passing it each @var{argument} on its
41336 command line. The file and arguments are hex-encoded strings. If
41337 @var{filename} is an empty string, the stub may use a default program
41338 (e.g.@: the last program run). The program is created in the stopped
41341 @c FIXME: What about non-stop mode?
41343 This packet is only available in extended mode (@pxref{extended mode}).
41349 @item @r{Any stop packet}
41350 for success (@pxref{Stop Reply Packets})
41354 @cindex @samp{vStopped} packet
41355 @xref{Notification Packets}.
41357 @item X @var{addr},@var{length}:@var{XX@dots{}}
41359 @cindex @samp{X} packet
41360 Write data to memory, where the data is transmitted in binary.
41361 Memory is specified by its address @var{addr} and number of addressable memory
41362 units @var{length} (@pxref{addressable memory unit});
41363 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
41373 @item z @var{type},@var{addr},@var{kind}
41374 @itemx Z @var{type},@var{addr},@var{kind}
41375 @anchor{insert breakpoint or watchpoint packet}
41376 @cindex @samp{z} packet
41377 @cindex @samp{Z} packets
41378 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
41379 watchpoint starting at address @var{address} of kind @var{kind}.
41381 Each breakpoint and watchpoint packet @var{type} is documented
41384 @emph{Implementation notes: A remote target shall return an empty string
41385 for an unrecognized breakpoint or watchpoint packet @var{type}. A
41386 remote target shall support either both or neither of a given
41387 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
41388 avoid potential problems with duplicate packets, the operations should
41389 be implemented in an idempotent way.}
41391 @item z0,@var{addr},@var{kind}
41392 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41393 @cindex @samp{z0} packet
41394 @cindex @samp{Z0} packet
41395 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
41396 @var{addr} of type @var{kind}.
41398 A software breakpoint is implemented by replacing the instruction at
41399 @var{addr} with a software breakpoint or trap instruction. The
41400 @var{kind} is target-specific and typically indicates the size of the
41401 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
41402 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
41403 architectures have additional meanings for @var{kind}
41404 (@pxref{Architecture-Specific Protocol Details}); if no
41405 architecture-specific value is being used, it should be @samp{0}.
41406 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
41407 conditional expressions in bytecode form that should be evaluated on
41408 the target's side. These are the conditions that should be taken into
41409 consideration when deciding if the breakpoint trigger should be
41410 reported back to @value{GDBN}.
41412 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
41413 for how to best report a software breakpoint event to @value{GDBN}.
41415 The @var{cond_list} parameter is comprised of a series of expressions,
41416 concatenated without separators. Each expression has the following form:
41420 @item X @var{len},@var{expr}
41421 @var{len} is the length of the bytecode expression and @var{expr} is the
41422 actual conditional expression in bytecode form.
41426 The optional @var{cmd_list} parameter introduces commands that may be
41427 run on the target, rather than being reported back to @value{GDBN}.
41428 The parameter starts with a numeric flag @var{persist}; if the flag is
41429 nonzero, then the breakpoint may remain active and the commands
41430 continue to be run even when @value{GDBN} disconnects from the target.
41431 Following this flag is a series of expressions concatenated with no
41432 separators. Each expression has the following form:
41436 @item X @var{len},@var{expr}
41437 @var{len} is the length of the bytecode expression and @var{expr} is the
41438 actual commands expression in bytecode form.
41442 @emph{Implementation note: It is possible for a target to copy or move
41443 code that contains software breakpoints (e.g., when implementing
41444 overlays). The behavior of this packet, in the presence of such a
41445 target, is not defined.}
41457 @item z1,@var{addr},@var{kind}
41458 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41459 @cindex @samp{z1} packet
41460 @cindex @samp{Z1} packet
41461 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
41462 address @var{addr}.
41464 A hardware breakpoint is implemented using a mechanism that is not
41465 dependent on being able to modify the target's memory. The
41466 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
41467 same meaning as in @samp{Z0} packets.
41469 @emph{Implementation note: A hardware breakpoint is not affected by code
41482 @item z2,@var{addr},@var{kind}
41483 @itemx Z2,@var{addr},@var{kind}
41484 @cindex @samp{z2} packet
41485 @cindex @samp{Z2} packet
41486 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41487 The number of bytes to watch is specified by @var{kind}.
41499 @item z3,@var{addr},@var{kind}
41500 @itemx Z3,@var{addr},@var{kind}
41501 @cindex @samp{z3} packet
41502 @cindex @samp{Z3} packet
41503 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41504 The number of bytes to watch is specified by @var{kind}.
41516 @item z4,@var{addr},@var{kind}
41517 @itemx Z4,@var{addr},@var{kind}
41518 @cindex @samp{z4} packet
41519 @cindex @samp{Z4} packet
41520 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
41521 The number of bytes to watch is specified by @var{kind}.
41535 @node Stop Reply Packets
41536 @section Stop Reply Packets
41537 @cindex stop reply packets
41539 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
41540 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
41541 receive any of the below as a reply. Except for @samp{?}
41542 and @samp{vStopped}, that reply is only returned
41543 when the target halts. In the below the exact meaning of @dfn{signal
41544 number} is defined by the header @file{include/gdb/signals.h} in the
41545 @value{GDBN} source code.
41547 In non-stop mode, the server will simply reply @samp{OK} to commands
41548 such as @samp{vCont}; any stop will be the subject of a future
41549 notification. @xref{Remote Non-Stop}.
41551 As in the description of request packets, we include spaces in the
41552 reply templates for clarity; these are not part of the reply packet's
41553 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
41559 The program received signal number @var{AA} (a two-digit hexadecimal
41560 number). This is equivalent to a @samp{T} response with no
41561 @var{n}:@var{r} pairs.
41563 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
41564 @cindex @samp{T} packet reply
41565 The program received signal number @var{AA} (a two-digit hexadecimal
41566 number). This is equivalent to an @samp{S} response, except that the
41567 @samp{@var{n}:@var{r}} pairs can carry values of important registers
41568 and other information directly in the stop reply packet, reducing
41569 round-trip latency. Single-step and breakpoint traps are reported
41570 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
41574 If @var{n} is a hexadecimal number, it is a register number, and the
41575 corresponding @var{r} gives that register's value. The data @var{r} is a
41576 series of bytes in target byte order, with each byte given by a
41577 two-digit hex number.
41580 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
41581 the stopped thread, as specified in @ref{thread-id syntax}.
41584 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
41585 the core on which the stop event was detected.
41588 If @var{n} is a recognized @dfn{stop reason}, it describes a more
41589 specific event that stopped the target. The currently defined stop
41590 reasons are listed below. The @var{aa} should be @samp{05}, the trap
41591 signal. At most one stop reason should be present.
41594 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
41595 and go on to the next; this allows us to extend the protocol in the
41599 The currently defined stop reasons are:
41605 The packet indicates a watchpoint hit, and @var{r} is the data address, in
41608 @item syscall_entry
41609 @itemx syscall_return
41610 The packet indicates a syscall entry or return, and @var{r} is the
41611 syscall number, in hex.
41613 @cindex shared library events, remote reply
41615 The packet indicates that the loaded libraries have changed.
41616 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
41617 list of loaded libraries. The @var{r} part is ignored.
41619 @cindex replay log events, remote reply
41621 The packet indicates that the target cannot continue replaying
41622 logged execution events, because it has reached the end (or the
41623 beginning when executing backward) of the log. The value of @var{r}
41624 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
41625 for more information.
41628 @anchor{swbreak stop reason}
41629 The packet indicates a software breakpoint instruction was executed,
41630 irrespective of whether it was @value{GDBN} that planted the
41631 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
41632 part must be left empty.
41634 On some architectures, such as x86, at the architecture level, when a
41635 breakpoint instruction executes the program counter points at the
41636 breakpoint address plus an offset. On such targets, the stub is
41637 responsible for adjusting the PC to point back at the breakpoint
41640 This packet should not be sent by default; older @value{GDBN} versions
41641 did not support it. @value{GDBN} requests it, by supplying an
41642 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41643 remote stub must also supply the appropriate @samp{qSupported} feature
41644 indicating support.
41646 This packet is required for correct non-stop mode operation.
41649 The packet indicates the target stopped for a hardware breakpoint.
41650 The @var{r} part must be left empty.
41652 The same remarks about @samp{qSupported} and non-stop mode above
41655 @cindex fork events, remote reply
41657 The packet indicates that @code{fork} was called, and @var{r}
41658 is the thread ID of the new child process. Refer to
41659 @ref{thread-id syntax} for the format of the @var{thread-id}
41660 field. This packet is only applicable to targets that support
41663 This packet should not be sent by default; older @value{GDBN} versions
41664 did not support it. @value{GDBN} requests it, by supplying an
41665 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41666 remote stub must also supply the appropriate @samp{qSupported} feature
41667 indicating support.
41669 @cindex vfork events, remote reply
41671 The packet indicates that @code{vfork} was called, and @var{r}
41672 is the thread ID of the new child process. Refer to
41673 @ref{thread-id syntax} for the format of the @var{thread-id}
41674 field. This packet is only applicable to targets that support
41677 This packet should not be sent by default; older @value{GDBN} versions
41678 did not support it. @value{GDBN} requests it, by supplying an
41679 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41680 remote stub must also supply the appropriate @samp{qSupported} feature
41681 indicating support.
41683 @cindex vforkdone events, remote reply
41685 The packet indicates that a child process created by a vfork
41686 has either called @code{exec} or terminated, so that the
41687 address spaces of the parent and child process are no longer
41688 shared. The @var{r} part is ignored. This packet is only
41689 applicable to targets that support vforkdone events.
41691 This packet should not be sent by default; older @value{GDBN} versions
41692 did not support it. @value{GDBN} requests it, by supplying an
41693 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41694 remote stub must also supply the appropriate @samp{qSupported} feature
41695 indicating support.
41697 @cindex exec events, remote reply
41699 The packet indicates that @code{execve} was called, and @var{r}
41700 is the absolute pathname of the file that was executed, in hex.
41701 This packet is only applicable to targets that support exec events.
41703 This packet should not be sent by default; older @value{GDBN} versions
41704 did not support it. @value{GDBN} requests it, by supplying an
41705 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41706 remote stub must also supply the appropriate @samp{qSupported} feature
41707 indicating support.
41709 @cindex thread create event, remote reply
41710 @anchor{thread create event}
41712 The packet indicates that the thread was just created. The new thread
41713 is stopped until @value{GDBN} sets it running with a resumption packet
41714 (@pxref{vCont packet}). This packet should not be sent by default;
41715 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
41716 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
41717 @var{r} part is ignored.
41722 @itemx W @var{AA} ; process:@var{pid}
41723 The process exited, and @var{AA} is the exit status. This is only
41724 applicable to certain targets.
41726 The second form of the response, including the process ID of the
41727 exited process, can be used only when @value{GDBN} has reported
41728 support for multiprocess protocol extensions; see @ref{multiprocess
41729 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41733 @itemx X @var{AA} ; process:@var{pid}
41734 The process terminated with signal @var{AA}.
41736 The second form of the response, including the process ID of the
41737 terminated process, can be used only when @value{GDBN} has reported
41738 support for multiprocess protocol extensions; see @ref{multiprocess
41739 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41742 @anchor{thread exit event}
41743 @cindex thread exit event, remote reply
41744 @item w @var{AA} ; @var{tid}
41746 The thread exited, and @var{AA} is the exit status. This response
41747 should not be sent by default; @value{GDBN} requests it with the
41748 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
41749 @var{AA} is formatted as a big-endian hex string.
41752 There are no resumed threads left in the target. In other words, even
41753 though the process is alive, the last resumed thread has exited. For
41754 example, say the target process has two threads: thread 1 and thread
41755 2. The client leaves thread 1 stopped, and resumes thread 2, which
41756 subsequently exits. At this point, even though the process is still
41757 alive, and thus no @samp{W} stop reply is sent, no thread is actually
41758 executing either. The @samp{N} stop reply thus informs the client
41759 that it can stop waiting for stop replies. This packet should not be
41760 sent by default; older @value{GDBN} versions did not support it.
41761 @value{GDBN} requests it, by supplying an appropriate
41762 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
41763 also supply the appropriate @samp{qSupported} feature indicating
41766 @item O @var{XX}@dots{}
41767 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
41768 written as the program's console output. This can happen at any time
41769 while the program is running and the debugger should continue to wait
41770 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
41772 @item F @var{call-id},@var{parameter}@dots{}
41773 @var{call-id} is the identifier which says which host system call should
41774 be called. This is just the name of the function. Translation into the
41775 correct system call is only applicable as it's defined in @value{GDBN}.
41776 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
41779 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
41780 this very system call.
41782 The target replies with this packet when it expects @value{GDBN} to
41783 call a host system call on behalf of the target. @value{GDBN} replies
41784 with an appropriate @samp{F} packet and keeps up waiting for the next
41785 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
41786 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
41787 Protocol Extension}, for more details.
41791 @node General Query Packets
41792 @section General Query Packets
41793 @cindex remote query requests
41795 Packets starting with @samp{q} are @dfn{general query packets};
41796 packets starting with @samp{Q} are @dfn{general set packets}. General
41797 query and set packets are a semi-unified form for retrieving and
41798 sending information to and from the stub.
41800 The initial letter of a query or set packet is followed by a name
41801 indicating what sort of thing the packet applies to. For example,
41802 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
41803 definitions with the stub. These packet names follow some
41808 The name must not contain commas, colons or semicolons.
41810 Most @value{GDBN} query and set packets have a leading upper case
41813 The names of custom vendor packets should use a company prefix, in
41814 lower case, followed by a period. For example, packets designed at
41815 the Acme Corporation might begin with @samp{qacme.foo} (for querying
41816 foos) or @samp{Qacme.bar} (for setting bars).
41819 The name of a query or set packet should be separated from any
41820 parameters by a @samp{:}; the parameters themselves should be
41821 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
41822 full packet name, and check for a separator or the end of the packet,
41823 in case two packet names share a common prefix. New packets should not begin
41824 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
41825 packets predate these conventions, and have arguments without any terminator
41826 for the packet name; we suspect they are in widespread use in places that
41827 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
41828 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
41831 Like the descriptions of the other packets, each description here
41832 has a template showing the packet's overall syntax, followed by an
41833 explanation of the packet's meaning. We include spaces in some of the
41834 templates for clarity; these are not part of the packet's syntax. No
41835 @value{GDBN} packet uses spaces to separate its components.
41837 Here are the currently defined query and set packets:
41843 Turn on or off the agent as a helper to perform some debugging operations
41844 delegated from @value{GDBN} (@pxref{Control Agent}).
41846 @item QAllow:@var{op}:@var{val}@dots{}
41847 @cindex @samp{QAllow} packet
41848 Specify which operations @value{GDBN} expects to request of the
41849 target, as a semicolon-separated list of operation name and value
41850 pairs. Possible values for @var{op} include @samp{WriteReg},
41851 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
41852 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
41853 indicating that @value{GDBN} will not request the operation, or 1,
41854 indicating that it may. (The target can then use this to set up its
41855 own internals optimally, for instance if the debugger never expects to
41856 insert breakpoints, it may not need to install its own trap handler.)
41859 @cindex current thread, remote request
41860 @cindex @samp{qC} packet
41861 Return the current thread ID.
41865 @item QC @var{thread-id}
41866 Where @var{thread-id} is a thread ID as documented in
41867 @ref{thread-id syntax}.
41868 @item @r{(anything else)}
41869 Any other reply implies the old thread ID.
41872 @item qCRC:@var{addr},@var{length}
41873 @cindex CRC of memory block, remote request
41874 @cindex @samp{qCRC} packet
41875 @anchor{qCRC packet}
41876 Compute the CRC checksum of a block of memory using CRC-32 defined in
41877 IEEE 802.3. The CRC is computed byte at a time, taking the most
41878 significant bit of each byte first. The initial pattern code
41879 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
41881 @emph{Note:} This is the same CRC used in validating separate debug
41882 files (@pxref{Separate Debug Files, , Debugging Information in Separate
41883 Files}). However the algorithm is slightly different. When validating
41884 separate debug files, the CRC is computed taking the @emph{least}
41885 significant bit of each byte first, and the final result is inverted to
41886 detect trailing zeros.
41891 An error (such as memory fault)
41892 @item C @var{crc32}
41893 The specified memory region's checksum is @var{crc32}.
41896 @item QDisableRandomization:@var{value}
41897 @cindex disable address space randomization, remote request
41898 @cindex @samp{QDisableRandomization} packet
41899 Some target operating systems will randomize the virtual address space
41900 of the inferior process as a security feature, but provide a feature
41901 to disable such randomization, e.g.@: to allow for a more deterministic
41902 debugging experience. On such systems, this packet with a @var{value}
41903 of 1 directs the target to disable address space randomization for
41904 processes subsequently started via @samp{vRun} packets, while a packet
41905 with a @var{value} of 0 tells the target to enable address space
41908 This packet is only available in extended mode (@pxref{extended mode}).
41913 The request succeeded.
41916 An error occurred. The error number @var{nn} is given as hex digits.
41919 An empty reply indicates that @samp{QDisableRandomization} is not supported
41923 This packet is not probed by default; the remote stub must request it,
41924 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41925 This should only be done on targets that actually support disabling
41926 address space randomization.
41928 @item QStartupWithShell:@var{value}
41929 @cindex startup with shell, remote request
41930 @cindex @samp{QStartupWithShell} packet
41931 On UNIX-like targets, it is possible to start the inferior using a
41932 shell program. This is the default behavior on both @value{GDBN} and
41933 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
41934 used to inform @command{gdbserver} whether it should start the
41935 inferior using a shell or not.
41937 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
41938 to start the inferior. If @var{value} is @samp{1},
41939 @command{gdbserver} will use a shell to start the inferior. All other
41940 values are considered an error.
41942 This packet is only available in extended mode (@pxref{extended
41948 The request succeeded.
41951 An error occurred. The error number @var{nn} is given as hex digits.
41954 This packet is not probed by default; the remote stub must request it,
41955 by supplying an appropriate @samp{qSupported} response
41956 (@pxref{qSupported}). This should only be done on targets that
41957 actually support starting the inferior using a shell.
41959 Use of this packet is controlled by the @code{set startup-with-shell}
41960 command; @pxref{set startup-with-shell}.
41962 @item QEnvironmentHexEncoded:@var{hex-value}
41963 @anchor{QEnvironmentHexEncoded}
41964 @cindex set environment variable, remote request
41965 @cindex @samp{QEnvironmentHexEncoded} packet
41966 On UNIX-like targets, it is possible to set environment variables that
41967 will be passed to the inferior during the startup process. This
41968 packet is used to inform @command{gdbserver} of an environment
41969 variable that has been defined by the user on @value{GDBN} (@pxref{set
41972 The packet is composed by @var{hex-value}, an hex encoded
41973 representation of the @var{name=value} format representing an
41974 environment variable. The name of the environment variable is
41975 represented by @var{name}, and the value to be assigned to the
41976 environment variable is represented by @var{value}. If the variable
41977 has no value (i.e., the value is @code{null}), then @var{value} will
41980 This packet is only available in extended mode (@pxref{extended
41986 The request succeeded.
41989 This packet is not probed by default; the remote stub must request it,
41990 by supplying an appropriate @samp{qSupported} response
41991 (@pxref{qSupported}). This should only be done on targets that
41992 actually support passing environment variables to the starting
41995 This packet is related to the @code{set environment} command;
41996 @pxref{set environment}.
41998 @item QEnvironmentUnset:@var{hex-value}
41999 @anchor{QEnvironmentUnset}
42000 @cindex unset environment variable, remote request
42001 @cindex @samp{QEnvironmentUnset} packet
42002 On UNIX-like targets, it is possible to unset environment variables
42003 before starting the inferior in the remote target. This packet is
42004 used to inform @command{gdbserver} of an environment variable that has
42005 been unset by the user on @value{GDBN} (@pxref{unset environment}).
42007 The packet is composed by @var{hex-value}, an hex encoded
42008 representation of the name of the environment variable to be unset.
42010 This packet is only available in extended mode (@pxref{extended
42016 The request succeeded.
42019 This packet is not probed by default; the remote stub must request it,
42020 by supplying an appropriate @samp{qSupported} response
42021 (@pxref{qSupported}). This should only be done on targets that
42022 actually support passing environment variables to the starting
42025 This packet is related to the @code{unset environment} command;
42026 @pxref{unset environment}.
42028 @item QEnvironmentReset
42029 @anchor{QEnvironmentReset}
42030 @cindex reset environment, remote request
42031 @cindex @samp{QEnvironmentReset} packet
42032 On UNIX-like targets, this packet is used to reset the state of
42033 environment variables in the remote target before starting the
42034 inferior. In this context, reset means unsetting all environment
42035 variables that were previously set by the user (i.e., were not
42036 initially present in the environment). It is sent to
42037 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
42038 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
42039 (@pxref{QEnvironmentUnset}) packets.
42041 This packet is only available in extended mode (@pxref{extended
42047 The request succeeded.
42050 This packet is not probed by default; the remote stub must request it,
42051 by supplying an appropriate @samp{qSupported} response
42052 (@pxref{qSupported}). This should only be done on targets that
42053 actually support passing environment variables to the starting
42056 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
42057 @anchor{QSetWorkingDir packet}
42058 @cindex set working directory, remote request
42059 @cindex @samp{QSetWorkingDir} packet
42060 This packet is used to inform the remote server of the intended
42061 current working directory for programs that are going to be executed.
42063 The packet is composed by @var{directory}, an hex encoded
42064 representation of the directory that the remote inferior will use as
42065 its current working directory. If @var{directory} is an empty string,
42066 the remote server should reset the inferior's current working
42067 directory to its original, empty value.
42069 This packet is only available in extended mode (@pxref{extended
42075 The request succeeded.
42079 @itemx qsThreadInfo
42080 @cindex list active threads, remote request
42081 @cindex @samp{qfThreadInfo} packet
42082 @cindex @samp{qsThreadInfo} packet
42083 Obtain a list of all active thread IDs from the target (OS). Since there
42084 may be too many active threads to fit into one reply packet, this query
42085 works iteratively: it may require more than one query/reply sequence to
42086 obtain the entire list of threads. The first query of the sequence will
42087 be the @samp{qfThreadInfo} query; subsequent queries in the
42088 sequence will be the @samp{qsThreadInfo} query.
42090 NOTE: This packet replaces the @samp{qL} query (see below).
42094 @item m @var{thread-id}
42096 @item m @var{thread-id},@var{thread-id}@dots{}
42097 a comma-separated list of thread IDs
42099 (lower case letter @samp{L}) denotes end of list.
42102 In response to each query, the target will reply with a list of one or
42103 more thread IDs, separated by commas.
42104 @value{GDBN} will respond to each reply with a request for more thread
42105 ids (using the @samp{qs} form of the query), until the target responds
42106 with @samp{l} (lower-case ell, for @dfn{last}).
42107 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
42110 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
42111 initial connection with the remote target, and the very first thread ID
42112 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
42113 message. Therefore, the stub should ensure that the first thread ID in
42114 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
42116 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
42117 @cindex get thread-local storage address, remote request
42118 @cindex @samp{qGetTLSAddr} packet
42119 Fetch the address associated with thread local storage specified
42120 by @var{thread-id}, @var{offset}, and @var{lm}.
42122 @var{thread-id} is the thread ID associated with the
42123 thread for which to fetch the TLS address. @xref{thread-id syntax}.
42125 @var{offset} is the (big endian, hex encoded) offset associated with the
42126 thread local variable. (This offset is obtained from the debug
42127 information associated with the variable.)
42129 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
42130 load module associated with the thread local storage. For example,
42131 a @sc{gnu}/Linux system will pass the link map address of the shared
42132 object associated with the thread local storage under consideration.
42133 Other operating environments may choose to represent the load module
42134 differently, so the precise meaning of this parameter will vary.
42138 @item @var{XX}@dots{}
42139 Hex encoded (big endian) bytes representing the address of the thread
42140 local storage requested.
42143 An error occurred. The error number @var{nn} is given as hex digits.
42146 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
42149 @item qGetTIBAddr:@var{thread-id}
42150 @cindex get thread information block address
42151 @cindex @samp{qGetTIBAddr} packet
42152 Fetch address of the Windows OS specific Thread Information Block.
42154 @var{thread-id} is the thread ID associated with the thread.
42158 @item @var{XX}@dots{}
42159 Hex encoded (big endian) bytes representing the linear address of the
42160 thread information block.
42163 An error occured. This means that either the thread was not found, or the
42164 address could not be retrieved.
42167 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
42170 @item qL @var{startflag} @var{threadcount} @var{nextthread}
42171 Obtain thread information from RTOS. Where: @var{startflag} (one hex
42172 digit) is one to indicate the first query and zero to indicate a
42173 subsequent query; @var{threadcount} (two hex digits) is the maximum
42174 number of threads the response packet can contain; and @var{nextthread}
42175 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
42176 returned in the response as @var{argthread}.
42178 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
42182 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
42183 Where: @var{count} (two hex digits) is the number of threads being
42184 returned; @var{done} (one hex digit) is zero to indicate more threads
42185 and one indicates no further threads; @var{argthreadid} (eight hex
42186 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
42187 is a sequence of thread IDs, @var{threadid} (eight hex
42188 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
42191 @item qMemTags:@var{start address},@var{length}:@var{type}
42193 @cindex fetch memory tags
42194 @cindex @samp{qMemTags} packet
42195 Fetch memory tags of type @var{type} from the address range
42196 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42197 target is responsible for calculating how many tags will be returned, as this
42198 is architecture-specific.
42200 @var{start address} is the starting address of the memory range.
42202 @var{length} is the length, in bytes, of the memory range.
42204 @var{type} is the type of tag the request wants to fetch. The type is a signed
42209 @item @var{mxx}@dots{}
42210 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
42211 tags found in the requested memory range.
42214 An error occured. This means that fetching of memory tags failed for some
42218 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
42219 although this should not happen given @value{GDBN} will only send this packet
42220 if the stub has advertised support for memory tagging via @samp{qSupported}.
42223 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
42225 @cindex store memory tags
42226 @cindex @samp{QMemTags} packet
42227 Store memory tags of type @var{type} to the address range
42228 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42229 target is responsible for interpreting the type, the tag bytes and modifying
42230 the memory tag granules accordingly, given this is architecture-specific.
42232 The interpretation of how many tags (@var{nt}) should be written to how many
42233 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
42234 implementation-specific, but the following is suggested.
42236 If the number of memory tags, @var{nt}, is greater than or equal to the
42237 number of memory tag granules, @var{ng}, only @var{ng} tags will be
42240 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
42241 and the tag bytes will be used as a pattern that will get repeated until
42242 @var{ng} tags are stored.
42244 @var{start address} is the starting address of the memory range. The address
42245 does not have any restriction on alignment or size.
42247 @var{length} is the length, in bytes, of the memory range.
42249 @var{type} is the type of tag the request wants to fetch. The type is a signed
42252 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
42253 interpreted by the target. Each pair of hex digits is interpreted as a
42259 The request was successful and the memory tag granules were modified
42263 An error occured. This means that modifying the memory tag granules failed
42267 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
42268 although this should not happen given @value{GDBN} will only send this packet
42269 if the stub has advertised support for memory tagging via @samp{qSupported}.
42273 @cindex section offsets, remote request
42274 @cindex @samp{qOffsets} packet
42275 Get section offsets that the target used when relocating the downloaded
42280 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
42281 Relocate the @code{Text} section by @var{xxx} from its original address.
42282 Relocate the @code{Data} section by @var{yyy} from its original address.
42283 If the object file format provides segment information (e.g.@: @sc{elf}
42284 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
42285 segments by the supplied offsets.
42287 @emph{Note: while a @code{Bss} offset may be included in the response,
42288 @value{GDBN} ignores this and instead applies the @code{Data} offset
42289 to the @code{Bss} section.}
42291 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
42292 Relocate the first segment of the object file, which conventionally
42293 contains program code, to a starting address of @var{xxx}. If
42294 @samp{DataSeg} is specified, relocate the second segment, which
42295 conventionally contains modifiable data, to a starting address of
42296 @var{yyy}. @value{GDBN} will report an error if the object file
42297 does not contain segment information, or does not contain at least
42298 as many segments as mentioned in the reply. Extra segments are
42299 kept at fixed offsets relative to the last relocated segment.
42302 @item qP @var{mode} @var{thread-id}
42303 @cindex thread information, remote request
42304 @cindex @samp{qP} packet
42305 Returns information on @var{thread-id}. Where: @var{mode} is a hex
42306 encoded 32 bit mode; @var{thread-id} is a thread ID
42307 (@pxref{thread-id syntax}).
42309 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
42312 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
42316 @cindex non-stop mode, remote request
42317 @cindex @samp{QNonStop} packet
42319 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
42320 @xref{Remote Non-Stop}, for more information.
42325 The request succeeded.
42328 An error occurred. The error number @var{nn} is given as hex digits.
42331 An empty reply indicates that @samp{QNonStop} is not supported by
42335 This packet is not probed by default; the remote stub must request it,
42336 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42337 Use of this packet is controlled by the @code{set non-stop} command;
42338 @pxref{Non-Stop Mode}.
42340 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
42341 @itemx QCatchSyscalls:0
42342 @cindex catch syscalls from inferior, remote request
42343 @cindex @samp{QCatchSyscalls} packet
42344 @anchor{QCatchSyscalls}
42345 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
42346 catching syscalls from the inferior process.
42348 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
42349 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
42350 is listed, every system call should be reported.
42352 Note that if a syscall not in the list is reported, @value{GDBN} will
42353 still filter the event according to its own list from all corresponding
42354 @code{catch syscall} commands. However, it is more efficient to only
42355 report the requested syscalls.
42357 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
42358 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
42360 If the inferior process execs, the state of @samp{QCatchSyscalls} is
42361 kept for the new process too. On targets where exec may affect syscall
42362 numbers, for example with exec between 32 and 64-bit processes, the
42363 client should send a new packet with the new syscall list.
42368 The request succeeded.
42371 An error occurred. @var{nn} are hex digits.
42374 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
42378 Use of this packet is controlled by the @code{set remote catch-syscalls}
42379 command (@pxref{Remote Configuration, set remote catch-syscalls}).
42380 This packet is not probed by default; the remote stub must request it,
42381 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42383 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42384 @cindex pass signals to inferior, remote request
42385 @cindex @samp{QPassSignals} packet
42386 @anchor{QPassSignals}
42387 Each listed @var{signal} should be passed directly to the inferior process.
42388 Signals are numbered identically to continue packets and stop replies
42389 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42390 strictly greater than the previous item. These signals do not need to stop
42391 the inferior, or be reported to @value{GDBN}. All other signals should be
42392 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
42393 combine; any earlier @samp{QPassSignals} list is completely replaced by the
42394 new list. This packet improves performance when using @samp{handle
42395 @var{signal} nostop noprint pass}.
42400 The request succeeded.
42403 An error occurred. The error number @var{nn} is given as hex digits.
42406 An empty reply indicates that @samp{QPassSignals} is not supported by
42410 Use of this packet is controlled by the @code{set remote pass-signals}
42411 command (@pxref{Remote Configuration, set remote pass-signals}).
42412 This packet is not probed by default; the remote stub must request it,
42413 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42415 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42416 @cindex signals the inferior may see, remote request
42417 @cindex @samp{QProgramSignals} packet
42418 @anchor{QProgramSignals}
42419 Each listed @var{signal} may be delivered to the inferior process.
42420 Others should be silently discarded.
42422 In some cases, the remote stub may need to decide whether to deliver a
42423 signal to the program or not without @value{GDBN} involvement. One
42424 example of that is while detaching --- the program's threads may have
42425 stopped for signals that haven't yet had a chance of being reported to
42426 @value{GDBN}, and so the remote stub can use the signal list specified
42427 by this packet to know whether to deliver or ignore those pending
42430 This does not influence whether to deliver a signal as requested by a
42431 resumption packet (@pxref{vCont packet}).
42433 Signals are numbered identically to continue packets and stop replies
42434 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42435 strictly greater than the previous item. Multiple
42436 @samp{QProgramSignals} packets do not combine; any earlier
42437 @samp{QProgramSignals} list is completely replaced by the new list.
42442 The request succeeded.
42445 An error occurred. The error number @var{nn} is given as hex digits.
42448 An empty reply indicates that @samp{QProgramSignals} is not supported
42452 Use of this packet is controlled by the @code{set remote program-signals}
42453 command (@pxref{Remote Configuration, set remote program-signals}).
42454 This packet is not probed by default; the remote stub must request it,
42455 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42457 @anchor{QThreadEvents}
42458 @item QThreadEvents:1
42459 @itemx QThreadEvents:0
42460 @cindex thread create/exit events, remote request
42461 @cindex @samp{QThreadEvents} packet
42463 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
42464 reporting of thread create and exit events. @xref{thread create
42465 event}, for the reply specifications. For example, this is used in
42466 non-stop mode when @value{GDBN} stops a set of threads and
42467 synchronously waits for the their corresponding stop replies. Without
42468 exit events, if one of the threads exits, @value{GDBN} would hang
42469 forever not knowing that it should no longer expect a stop for that
42470 same thread. @value{GDBN} does not enable this feature unless the
42471 stub reports that it supports it by including @samp{QThreadEvents+} in
42472 its @samp{qSupported} reply.
42477 The request succeeded.
42480 An error occurred. The error number @var{nn} is given as hex digits.
42483 An empty reply indicates that @samp{QThreadEvents} is not supported by
42487 Use of this packet is controlled by the @code{set remote thread-events}
42488 command (@pxref{Remote Configuration, set remote thread-events}).
42490 @item qRcmd,@var{command}
42491 @cindex execute remote command, remote request
42492 @cindex @samp{qRcmd} packet
42493 @var{command} (hex encoded) is passed to the local interpreter for
42494 execution. Invalid commands should be reported using the output
42495 string. Before the final result packet, the target may also respond
42496 with a number of intermediate @samp{O@var{output}} console output
42497 packets. @emph{Implementors should note that providing access to a
42498 stubs's interpreter may have security implications}.
42503 A command response with no output.
42505 A command response with the hex encoded output string @var{OUTPUT}.
42507 Indicate a badly formed request. The error number @var{NN} is given as
42510 An empty reply indicates that @samp{qRcmd} is not recognized.
42513 (Note that the @code{qRcmd} packet's name is separated from the
42514 command by a @samp{,}, not a @samp{:}, contrary to the naming
42515 conventions above. Please don't use this packet as a model for new
42518 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42519 @cindex searching memory, in remote debugging
42521 @cindex @samp{qSearch:memory} packet
42523 @cindex @samp{qSearch memory} packet
42524 @anchor{qSearch memory}
42525 Search @var{length} bytes at @var{address} for @var{search-pattern}.
42526 Both @var{address} and @var{length} are encoded in hex;
42527 @var{search-pattern} is a sequence of bytes, also hex encoded.
42532 The pattern was not found.
42534 The pattern was found at @var{address}.
42536 A badly formed request or an error was encountered while searching memory.
42538 An empty reply indicates that @samp{qSearch:memory} is not recognized.
42541 @item QStartNoAckMode
42542 @cindex @samp{QStartNoAckMode} packet
42543 @anchor{QStartNoAckMode}
42544 Request that the remote stub disable the normal @samp{+}/@samp{-}
42545 protocol acknowledgments (@pxref{Packet Acknowledgment}).
42550 The stub has switched to no-acknowledgment mode.
42551 @value{GDBN} acknowledges this response,
42552 but neither the stub nor @value{GDBN} shall send or expect further
42553 @samp{+}/@samp{-} acknowledgments in the current connection.
42555 An empty reply indicates that the stub does not support no-acknowledgment mode.
42558 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
42559 @cindex supported packets, remote query
42560 @cindex features of the remote protocol
42561 @cindex @samp{qSupported} packet
42562 @anchor{qSupported}
42563 Tell the remote stub about features supported by @value{GDBN}, and
42564 query the stub for features it supports. This packet allows
42565 @value{GDBN} and the remote stub to take advantage of each others'
42566 features. @samp{qSupported} also consolidates multiple feature probes
42567 at startup, to improve @value{GDBN} performance---a single larger
42568 packet performs better than multiple smaller probe packets on
42569 high-latency links. Some features may enable behavior which must not
42570 be on by default, e.g.@: because it would confuse older clients or
42571 stubs. Other features may describe packets which could be
42572 automatically probed for, but are not. These features must be
42573 reported before @value{GDBN} will use them. This ``default
42574 unsupported'' behavior is not appropriate for all packets, but it
42575 helps to keep the initial connection time under control with new
42576 versions of @value{GDBN} which support increasing numbers of packets.
42580 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
42581 The stub supports or does not support each returned @var{stubfeature},
42582 depending on the form of each @var{stubfeature} (see below for the
42585 An empty reply indicates that @samp{qSupported} is not recognized,
42586 or that no features needed to be reported to @value{GDBN}.
42589 The allowed forms for each feature (either a @var{gdbfeature} in the
42590 @samp{qSupported} packet, or a @var{stubfeature} in the response)
42594 @item @var{name}=@var{value}
42595 The remote protocol feature @var{name} is supported, and associated
42596 with the specified @var{value}. The format of @var{value} depends
42597 on the feature, but it must not include a semicolon.
42599 The remote protocol feature @var{name} is supported, and does not
42600 need an associated value.
42602 The remote protocol feature @var{name} is not supported.
42604 The remote protocol feature @var{name} may be supported, and
42605 @value{GDBN} should auto-detect support in some other way when it is
42606 needed. This form will not be used for @var{gdbfeature} notifications,
42607 but may be used for @var{stubfeature} responses.
42610 Whenever the stub receives a @samp{qSupported} request, the
42611 supplied set of @value{GDBN} features should override any previous
42612 request. This allows @value{GDBN} to put the stub in a known
42613 state, even if the stub had previously been communicating with
42614 a different version of @value{GDBN}.
42616 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
42621 This feature indicates whether @value{GDBN} supports multiprocess
42622 extensions to the remote protocol. @value{GDBN} does not use such
42623 extensions unless the stub also reports that it supports them by
42624 including @samp{multiprocess+} in its @samp{qSupported} reply.
42625 @xref{multiprocess extensions}, for details.
42628 This feature indicates that @value{GDBN} supports the XML target
42629 description. If the stub sees @samp{xmlRegisters=} with target
42630 specific strings separated by a comma, it will report register
42634 This feature indicates whether @value{GDBN} supports the
42635 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
42636 instruction reply packet}).
42639 This feature indicates whether @value{GDBN} supports the swbreak stop
42640 reason in stop replies. @xref{swbreak stop reason}, for details.
42643 This feature indicates whether @value{GDBN} supports the hwbreak stop
42644 reason in stop replies. @xref{swbreak stop reason}, for details.
42647 This feature indicates whether @value{GDBN} supports fork event
42648 extensions to the remote protocol. @value{GDBN} does not use such
42649 extensions unless the stub also reports that it supports them by
42650 including @samp{fork-events+} in its @samp{qSupported} reply.
42653 This feature indicates whether @value{GDBN} supports vfork event
42654 extensions to the remote protocol. @value{GDBN} does not use such
42655 extensions unless the stub also reports that it supports them by
42656 including @samp{vfork-events+} in its @samp{qSupported} reply.
42659 This feature indicates whether @value{GDBN} supports exec event
42660 extensions to the remote protocol. @value{GDBN} does not use such
42661 extensions unless the stub also reports that it supports them by
42662 including @samp{exec-events+} in its @samp{qSupported} reply.
42664 @item vContSupported
42665 This feature indicates whether @value{GDBN} wants to know the
42666 supported actions in the reply to @samp{vCont?} packet.
42669 Stubs should ignore any unknown values for
42670 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
42671 packet supports receiving packets of unlimited length (earlier
42672 versions of @value{GDBN} may reject overly long responses). Additional values
42673 for @var{gdbfeature} may be defined in the future to let the stub take
42674 advantage of new features in @value{GDBN}, e.g.@: incompatible
42675 improvements in the remote protocol---the @samp{multiprocess} feature is
42676 an example of such a feature. The stub's reply should be independent
42677 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
42678 describes all the features it supports, and then the stub replies with
42679 all the features it supports.
42681 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
42682 responses, as long as each response uses one of the standard forms.
42684 Some features are flags. A stub which supports a flag feature
42685 should respond with a @samp{+} form response. Other features
42686 require values, and the stub should respond with an @samp{=}
42689 Each feature has a default value, which @value{GDBN} will use if
42690 @samp{qSupported} is not available or if the feature is not mentioned
42691 in the @samp{qSupported} response. The default values are fixed; a
42692 stub is free to omit any feature responses that match the defaults.
42694 Not all features can be probed, but for those which can, the probing
42695 mechanism is useful: in some cases, a stub's internal
42696 architecture may not allow the protocol layer to know some information
42697 about the underlying target in advance. This is especially common in
42698 stubs which may be configured for multiple targets.
42700 These are the currently defined stub features and their properties:
42702 @multitable @columnfractions 0.35 0.2 0.12 0.2
42703 @c NOTE: The first row should be @headitem, but we do not yet require
42704 @c a new enough version of Texinfo (4.7) to use @headitem.
42706 @tab Value Required
42710 @item @samp{PacketSize}
42715 @item @samp{qXfer:auxv:read}
42720 @item @samp{qXfer:btrace:read}
42725 @item @samp{qXfer:btrace-conf:read}
42730 @item @samp{qXfer:exec-file:read}
42735 @item @samp{qXfer:features:read}
42740 @item @samp{qXfer:libraries:read}
42745 @item @samp{qXfer:libraries-svr4:read}
42750 @item @samp{augmented-libraries-svr4-read}
42755 @item @samp{qXfer:memory-map:read}
42760 @item @samp{qXfer:sdata:read}
42765 @item @samp{qXfer:siginfo:read}
42770 @item @samp{qXfer:siginfo:write}
42775 @item @samp{qXfer:threads:read}
42780 @item @samp{qXfer:traceframe-info:read}
42785 @item @samp{qXfer:uib:read}
42790 @item @samp{qXfer:fdpic:read}
42795 @item @samp{Qbtrace:off}
42800 @item @samp{Qbtrace:bts}
42805 @item @samp{Qbtrace:pt}
42810 @item @samp{Qbtrace-conf:bts:size}
42815 @item @samp{Qbtrace-conf:pt:size}
42820 @item @samp{QNonStop}
42825 @item @samp{QCatchSyscalls}
42830 @item @samp{QPassSignals}
42835 @item @samp{QStartNoAckMode}
42840 @item @samp{multiprocess}
42845 @item @samp{ConditionalBreakpoints}
42850 @item @samp{ConditionalTracepoints}
42855 @item @samp{ReverseContinue}
42860 @item @samp{ReverseStep}
42865 @item @samp{TracepointSource}
42870 @item @samp{QAgent}
42875 @item @samp{QAllow}
42880 @item @samp{QDisableRandomization}
42885 @item @samp{EnableDisableTracepoints}
42890 @item @samp{QTBuffer:size}
42895 @item @samp{tracenz}
42900 @item @samp{BreakpointCommands}
42905 @item @samp{swbreak}
42910 @item @samp{hwbreak}
42915 @item @samp{fork-events}
42920 @item @samp{vfork-events}
42925 @item @samp{exec-events}
42930 @item @samp{QThreadEvents}
42935 @item @samp{no-resumed}
42940 @item @samp{memory-tagging}
42947 These are the currently defined stub features, in more detail:
42950 @cindex packet size, remote protocol
42951 @item PacketSize=@var{bytes}
42952 The remote stub can accept packets up to at least @var{bytes} in
42953 length. @value{GDBN} will send packets up to this size for bulk
42954 transfers, and will never send larger packets. This is a limit on the
42955 data characters in the packet, including the frame and checksum.
42956 There is no trailing NUL byte in a remote protocol packet; if the stub
42957 stores packets in a NUL-terminated format, it should allow an extra
42958 byte in its buffer for the NUL. If this stub feature is not supported,
42959 @value{GDBN} guesses based on the size of the @samp{g} packet response.
42961 @item qXfer:auxv:read
42962 The remote stub understands the @samp{qXfer:auxv:read} packet
42963 (@pxref{qXfer auxiliary vector read}).
42965 @item qXfer:btrace:read
42966 The remote stub understands the @samp{qXfer:btrace:read}
42967 packet (@pxref{qXfer btrace read}).
42969 @item qXfer:btrace-conf:read
42970 The remote stub understands the @samp{qXfer:btrace-conf:read}
42971 packet (@pxref{qXfer btrace-conf read}).
42973 @item qXfer:exec-file:read
42974 The remote stub understands the @samp{qXfer:exec-file:read} packet
42975 (@pxref{qXfer executable filename read}).
42977 @item qXfer:features:read
42978 The remote stub understands the @samp{qXfer:features:read} packet
42979 (@pxref{qXfer target description read}).
42981 @item qXfer:libraries:read
42982 The remote stub understands the @samp{qXfer:libraries:read} packet
42983 (@pxref{qXfer library list read}).
42985 @item qXfer:libraries-svr4:read
42986 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
42987 (@pxref{qXfer svr4 library list read}).
42989 @item augmented-libraries-svr4-read
42990 The remote stub understands the augmented form of the
42991 @samp{qXfer:libraries-svr4:read} packet
42992 (@pxref{qXfer svr4 library list read}).
42994 @item qXfer:memory-map:read
42995 The remote stub understands the @samp{qXfer:memory-map:read} packet
42996 (@pxref{qXfer memory map read}).
42998 @item qXfer:sdata:read
42999 The remote stub understands the @samp{qXfer:sdata:read} packet
43000 (@pxref{qXfer sdata read}).
43002 @item qXfer:siginfo:read
43003 The remote stub understands the @samp{qXfer:siginfo:read} packet
43004 (@pxref{qXfer siginfo read}).
43006 @item qXfer:siginfo:write
43007 The remote stub understands the @samp{qXfer:siginfo:write} packet
43008 (@pxref{qXfer siginfo write}).
43010 @item qXfer:threads:read
43011 The remote stub understands the @samp{qXfer:threads:read} packet
43012 (@pxref{qXfer threads read}).
43014 @item qXfer:traceframe-info:read
43015 The remote stub understands the @samp{qXfer:traceframe-info:read}
43016 packet (@pxref{qXfer traceframe info read}).
43018 @item qXfer:uib:read
43019 The remote stub understands the @samp{qXfer:uib:read}
43020 packet (@pxref{qXfer unwind info block}).
43022 @item qXfer:fdpic:read
43023 The remote stub understands the @samp{qXfer:fdpic:read}
43024 packet (@pxref{qXfer fdpic loadmap read}).
43027 The remote stub understands the @samp{QNonStop} packet
43028 (@pxref{QNonStop}).
43030 @item QCatchSyscalls
43031 The remote stub understands the @samp{QCatchSyscalls} packet
43032 (@pxref{QCatchSyscalls}).
43035 The remote stub understands the @samp{QPassSignals} packet
43036 (@pxref{QPassSignals}).
43038 @item QStartNoAckMode
43039 The remote stub understands the @samp{QStartNoAckMode} packet and
43040 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
43043 @anchor{multiprocess extensions}
43044 @cindex multiprocess extensions, in remote protocol
43045 The remote stub understands the multiprocess extensions to the remote
43046 protocol syntax. The multiprocess extensions affect the syntax of
43047 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
43048 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
43049 replies. Note that reporting this feature indicates support for the
43050 syntactic extensions only, not that the stub necessarily supports
43051 debugging of more than one process at a time. The stub must not use
43052 multiprocess extensions in packet replies unless @value{GDBN} has also
43053 indicated it supports them in its @samp{qSupported} request.
43055 @item qXfer:osdata:read
43056 The remote stub understands the @samp{qXfer:osdata:read} packet
43057 ((@pxref{qXfer osdata read}).
43059 @item ConditionalBreakpoints
43060 The target accepts and implements evaluation of conditional expressions
43061 defined for breakpoints. The target will only report breakpoint triggers
43062 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
43064 @item ConditionalTracepoints
43065 The remote stub accepts and implements conditional expressions defined
43066 for tracepoints (@pxref{Tracepoint Conditions}).
43068 @item ReverseContinue
43069 The remote stub accepts and implements the reverse continue packet
43073 The remote stub accepts and implements the reverse step packet
43076 @item TracepointSource
43077 The remote stub understands the @samp{QTDPsrc} packet that supplies
43078 the source form of tracepoint definitions.
43081 The remote stub understands the @samp{QAgent} packet.
43084 The remote stub understands the @samp{QAllow} packet.
43086 @item QDisableRandomization
43087 The remote stub understands the @samp{QDisableRandomization} packet.
43089 @item StaticTracepoint
43090 @cindex static tracepoints, in remote protocol
43091 The remote stub supports static tracepoints.
43093 @item InstallInTrace
43094 @anchor{install tracepoint in tracing}
43095 The remote stub supports installing tracepoint in tracing.
43097 @item EnableDisableTracepoints
43098 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
43099 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
43100 to be enabled and disabled while a trace experiment is running.
43102 @item QTBuffer:size
43103 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
43104 packet that allows to change the size of the trace buffer.
43107 @cindex string tracing, in remote protocol
43108 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
43109 See @ref{Bytecode Descriptions} for details about the bytecode.
43111 @item BreakpointCommands
43112 @cindex breakpoint commands, in remote protocol
43113 The remote stub supports running a breakpoint's command list itself,
43114 rather than reporting the hit to @value{GDBN}.
43117 The remote stub understands the @samp{Qbtrace:off} packet.
43120 The remote stub understands the @samp{Qbtrace:bts} packet.
43123 The remote stub understands the @samp{Qbtrace:pt} packet.
43125 @item Qbtrace-conf:bts:size
43126 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
43128 @item Qbtrace-conf:pt:size
43129 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
43132 The remote stub reports the @samp{swbreak} stop reason for memory
43136 The remote stub reports the @samp{hwbreak} stop reason for hardware
43140 The remote stub reports the @samp{fork} stop reason for fork events.
43143 The remote stub reports the @samp{vfork} stop reason for vfork events
43144 and vforkdone events.
43147 The remote stub reports the @samp{exec} stop reason for exec events.
43149 @item vContSupported
43150 The remote stub reports the supported actions in the reply to
43151 @samp{vCont?} packet.
43153 @item QThreadEvents
43154 The remote stub understands the @samp{QThreadEvents} packet.
43157 The remote stub reports the @samp{N} stop reply.
43160 @item memory-tagging
43161 The remote stub supports and implements the required memory tagging
43162 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
43163 @samp{QMemTags} (@pxref{QMemTags}) packets.
43165 For AArch64 GNU/Linux systems, this feature also requires access to the
43166 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
43167 This is done via the @samp{vFile} requests.
43172 @cindex symbol lookup, remote request
43173 @cindex @samp{qSymbol} packet
43174 Notify the target that @value{GDBN} is prepared to serve symbol lookup
43175 requests. Accept requests from the target for the values of symbols.
43180 The target does not need to look up any (more) symbols.
43181 @item qSymbol:@var{sym_name}
43182 The target requests the value of symbol @var{sym_name} (hex encoded).
43183 @value{GDBN} may provide the value by using the
43184 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
43188 @item qSymbol:@var{sym_value}:@var{sym_name}
43189 Set the value of @var{sym_name} to @var{sym_value}.
43191 @var{sym_name} (hex encoded) is the name of a symbol whose value the
43192 target has previously requested.
43194 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
43195 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
43201 The target does not need to look up any (more) symbols.
43202 @item qSymbol:@var{sym_name}
43203 The target requests the value of a new symbol @var{sym_name} (hex
43204 encoded). @value{GDBN} will continue to supply the values of symbols
43205 (if available), until the target ceases to request them.
43210 @itemx QTDisconnected
43217 @itemx qTMinFTPILen
43219 @xref{Tracepoint Packets}.
43221 @anchor{qThreadExtraInfo}
43222 @item qThreadExtraInfo,@var{thread-id}
43223 @cindex thread attributes info, remote request
43224 @cindex @samp{qThreadExtraInfo} packet
43225 Obtain from the target OS a printable string description of thread
43226 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
43227 for the forms of @var{thread-id}. This
43228 string may contain anything that the target OS thinks is interesting
43229 for @value{GDBN} to tell the user about the thread. The string is
43230 displayed in @value{GDBN}'s @code{info threads} display. Some
43231 examples of possible thread extra info strings are @samp{Runnable}, or
43232 @samp{Blocked on Mutex}.
43236 @item @var{XX}@dots{}
43237 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
43238 comprising the printable string containing the extra information about
43239 the thread's attributes.
43242 (Note that the @code{qThreadExtraInfo} packet's name is separated from
43243 the command by a @samp{,}, not a @samp{:}, contrary to the naming
43244 conventions above. Please don't use this packet as a model for new
43263 @xref{Tracepoint Packets}.
43265 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
43266 @cindex read special object, remote request
43267 @cindex @samp{qXfer} packet
43268 @anchor{qXfer read}
43269 Read uninterpreted bytes from the target's special data area
43270 identified by the keyword @var{object}. Request @var{length} bytes
43271 starting at @var{offset} bytes into the data. The content and
43272 encoding of @var{annex} is specific to @var{object}; it can supply
43273 additional details about what data to access.
43278 Data @var{data} (@pxref{Binary Data}) has been read from the
43279 target. There may be more data at a higher address (although
43280 it is permitted to return @samp{m} even for the last valid
43281 block of data, as long as at least one byte of data was read).
43282 It is possible for @var{data} to have fewer bytes than the @var{length} in the
43286 Data @var{data} (@pxref{Binary Data}) has been read from the target.
43287 There is no more data to be read. It is possible for @var{data} to
43288 have fewer bytes than the @var{length} in the request.
43291 The @var{offset} in the request is at the end of the data.
43292 There is no more data to be read.
43295 The request was malformed, or @var{annex} was invalid.
43298 The offset was invalid, or there was an error encountered reading the data.
43299 The @var{nn} part is a hex-encoded @code{errno} value.
43302 An empty reply indicates the @var{object} string was not recognized by
43303 the stub, or that the object does not support reading.
43306 Here are the specific requests of this form defined so far. All the
43307 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
43308 formats, listed above.
43311 @item qXfer:auxv:read::@var{offset},@var{length}
43312 @anchor{qXfer auxiliary vector read}
43313 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
43314 auxiliary vector}. Note @var{annex} must be empty.
43316 This packet is not probed by default; the remote stub must request it,
43317 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43319 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
43320 @anchor{qXfer btrace read}
43322 Return a description of the current branch trace.
43323 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
43324 packet may have one of the following values:
43328 Returns all available branch trace.
43331 Returns all available branch trace if the branch trace changed since
43332 the last read request.
43335 Returns the new branch trace since the last read request. Adds a new
43336 block to the end of the trace that begins at zero and ends at the source
43337 location of the first branch in the trace buffer. This extra block is
43338 used to stitch traces together.
43340 If the trace buffer overflowed, returns an error indicating the overflow.
43343 This packet is not probed by default; the remote stub must request it
43344 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43346 @item qXfer:btrace-conf:read::@var{offset},@var{length}
43347 @anchor{qXfer btrace-conf read}
43349 Return a description of the current branch trace configuration.
43350 @xref{Branch Trace Configuration Format}.
43352 This packet is not probed by default; the remote stub must request it
43353 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43355 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
43356 @anchor{qXfer executable filename read}
43357 Return the full absolute name of the file that was executed to create
43358 a process running on the remote system. The annex specifies the
43359 numeric process ID of the process to query, encoded as a hexadecimal
43360 number. If the annex part is empty the remote stub should return the
43361 filename corresponding to the currently executing process.
43363 This packet is not probed by default; the remote stub must request it,
43364 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43366 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
43367 @anchor{qXfer target description read}
43368 Access the @dfn{target description}. @xref{Target Descriptions}. The
43369 annex specifies which XML document to access. The main description is
43370 always loaded from the @samp{target.xml} annex.
43372 This packet is not probed by default; the remote stub must request it,
43373 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43375 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
43376 @anchor{qXfer library list read}
43377 Access the target's list of loaded libraries. @xref{Library List Format}.
43378 The annex part of the generic @samp{qXfer} packet must be empty
43379 (@pxref{qXfer read}).
43381 Targets which maintain a list of libraries in the program's memory do
43382 not need to implement this packet; it is designed for platforms where
43383 the operating system manages the list of loaded libraries.
43385 This packet is not probed by default; the remote stub must request it,
43386 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43388 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
43389 @anchor{qXfer svr4 library list read}
43390 Access the target's list of loaded libraries when the target is an SVR4
43391 platform. @xref{Library List Format for SVR4 Targets}. The annex part
43392 of the generic @samp{qXfer} packet must be empty unless the remote
43393 stub indicated it supports the augmented form of this packet
43394 by supplying an appropriate @samp{qSupported} response
43395 (@pxref{qXfer read}, @ref{qSupported}).
43397 This packet is optional for better performance on SVR4 targets.
43398 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
43400 This packet is not probed by default; the remote stub must request it,
43401 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43403 If the remote stub indicates it supports the augmented form of this
43404 packet then the annex part of the generic @samp{qXfer} packet may
43405 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
43406 arguments. The currently supported arguments are:
43409 @item start=@var{address}
43410 A hexadecimal number specifying the address of the @samp{struct
43411 link_map} to start reading the library list from. If unset or zero
43412 then the first @samp{struct link_map} in the library list will be
43413 chosen as the starting point.
43415 @item prev=@var{address}
43416 A hexadecimal number specifying the address of the @samp{struct
43417 link_map} immediately preceding the @samp{struct link_map}
43418 specified by the @samp{start} argument. If unset or zero then
43419 the remote stub will expect that no @samp{struct link_map}
43420 exists prior to the starting point.
43424 Arguments that are not understood by the remote stub will be silently
43427 @item qXfer:memory-map:read::@var{offset},@var{length}
43428 @anchor{qXfer memory map read}
43429 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
43430 annex part of the generic @samp{qXfer} packet must be empty
43431 (@pxref{qXfer read}).
43433 This packet is not probed by default; the remote stub must request it,
43434 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43436 @item qXfer:sdata:read::@var{offset},@var{length}
43437 @anchor{qXfer sdata read}
43439 Read contents of the extra collected static tracepoint marker
43440 information. The annex part of the generic @samp{qXfer} packet must
43441 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
43444 This packet is not probed by default; the remote stub must request it,
43445 by supplying an appropriate @samp{qSupported} response
43446 (@pxref{qSupported}).
43448 @item qXfer:siginfo:read::@var{offset},@var{length}
43449 @anchor{qXfer siginfo read}
43450 Read contents of the extra signal information on the target
43451 system. The annex part of the generic @samp{qXfer} packet must be
43452 empty (@pxref{qXfer read}).
43454 This packet is not probed by default; the remote stub must request it,
43455 by supplying an appropriate @samp{qSupported} response
43456 (@pxref{qSupported}).
43458 @item qXfer:threads:read::@var{offset},@var{length}
43459 @anchor{qXfer threads read}
43460 Access the list of threads on target. @xref{Thread List Format}. The
43461 annex part of the generic @samp{qXfer} packet must be empty
43462 (@pxref{qXfer read}).
43464 This packet is not probed by default; the remote stub must request it,
43465 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43467 @item qXfer:traceframe-info:read::@var{offset},@var{length}
43468 @anchor{qXfer traceframe info read}
43470 Return a description of the current traceframe's contents.
43471 @xref{Traceframe Info Format}. The annex part of the generic
43472 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
43474 This packet is not probed by default; the remote stub must request it,
43475 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43477 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43478 @anchor{qXfer unwind info block}
43480 Return the unwind information block for @var{pc}. This packet is used
43481 on OpenVMS/ia64 to ask the kernel unwind information.
43483 This packet is not probed by default.
43485 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43486 @anchor{qXfer fdpic loadmap read}
43487 Read contents of @code{loadmap}s on the target system. The
43488 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43489 executable @code{loadmap} or interpreter @code{loadmap} to read.
43491 This packet is not probed by default; the remote stub must request it,
43492 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43494 @item qXfer:osdata:read::@var{offset},@var{length}
43495 @anchor{qXfer osdata read}
43496 Access the target's @dfn{operating system information}.
43497 @xref{Operating System Information}.
43501 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43502 @cindex write data into object, remote request
43503 @anchor{qXfer write}
43504 Write uninterpreted bytes into the target's special data area
43505 identified by the keyword @var{object}, starting at @var{offset} bytes
43506 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43507 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43508 is specific to @var{object}; it can supply additional details about what data
43514 @var{nn} (hex encoded) is the number of bytes written.
43515 This may be fewer bytes than supplied in the request.
43518 The request was malformed, or @var{annex} was invalid.
43521 The offset was invalid, or there was an error encountered writing the data.
43522 The @var{nn} part is a hex-encoded @code{errno} value.
43525 An empty reply indicates the @var{object} string was not
43526 recognized by the stub, or that the object does not support writing.
43529 Here are the specific requests of this form defined so far. All the
43530 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
43531 formats, listed above.
43534 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
43535 @anchor{qXfer siginfo write}
43536 Write @var{data} to the extra signal information on the target system.
43537 The annex part of the generic @samp{qXfer} packet must be
43538 empty (@pxref{qXfer write}).
43540 This packet is not probed by default; the remote stub must request it,
43541 by supplying an appropriate @samp{qSupported} response
43542 (@pxref{qSupported}).
43545 @item qXfer:@var{object}:@var{operation}:@dots{}
43546 Requests of this form may be added in the future. When a stub does
43547 not recognize the @var{object} keyword, or its support for
43548 @var{object} does not recognize the @var{operation} keyword, the stub
43549 must respond with an empty packet.
43551 @item qAttached:@var{pid}
43552 @cindex query attached, remote request
43553 @cindex @samp{qAttached} packet
43554 Return an indication of whether the remote server attached to an
43555 existing process or created a new process. When the multiprocess
43556 protocol extensions are supported (@pxref{multiprocess extensions}),
43557 @var{pid} is an integer in hexadecimal format identifying the target
43558 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
43559 the query packet will be simplified as @samp{qAttached}.
43561 This query is used, for example, to know whether the remote process
43562 should be detached or killed when a @value{GDBN} session is ended with
43563 the @code{quit} command.
43568 The remote server attached to an existing process.
43570 The remote server created a new process.
43572 A badly formed request or an error was encountered.
43576 Enable branch tracing for the current thread using Branch Trace Store.
43581 Branch tracing has been enabled.
43583 A badly formed request or an error was encountered.
43587 Enable branch tracing for the current thread using Intel Processor Trace.
43592 Branch tracing has been enabled.
43594 A badly formed request or an error was encountered.
43598 Disable branch tracing for the current thread.
43603 Branch tracing has been disabled.
43605 A badly formed request or an error was encountered.
43608 @item Qbtrace-conf:bts:size=@var{value}
43609 Set the requested ring buffer size for new threads that use the
43610 btrace recording method in bts format.
43615 The ring buffer size has been set.
43617 A badly formed request or an error was encountered.
43620 @item Qbtrace-conf:pt:size=@var{value}
43621 Set the requested ring buffer size for new threads that use the
43622 btrace recording method in pt format.
43627 The ring buffer size has been set.
43629 A badly formed request or an error was encountered.
43634 @node Architecture-Specific Protocol Details
43635 @section Architecture-Specific Protocol Details
43637 This section describes how the remote protocol is applied to specific
43638 target architectures. Also see @ref{Standard Target Features}, for
43639 details of XML target descriptions for each architecture.
43642 * ARM-Specific Protocol Details::
43643 * MIPS-Specific Protocol Details::
43646 @node ARM-Specific Protocol Details
43647 @subsection @acronym{ARM}-specific Protocol Details
43650 * ARM Breakpoint Kinds::
43651 * ARM Memory Tag Types::
43654 @node ARM Breakpoint Kinds
43655 @subsubsection @acronym{ARM} Breakpoint Kinds
43656 @cindex breakpoint kinds, @acronym{ARM}
43658 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43663 16-bit Thumb mode breakpoint.
43666 32-bit Thumb mode (Thumb-2) breakpoint.
43669 32-bit @acronym{ARM} mode breakpoint.
43673 @node ARM Memory Tag Types
43674 @subsubsection @acronym{ARM} Memory Tag Types
43675 @cindex memory tag types, @acronym{ARM}
43677 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
43690 @node MIPS-Specific Protocol Details
43691 @subsection @acronym{MIPS}-specific Protocol Details
43694 * MIPS Register packet Format::
43695 * MIPS Breakpoint Kinds::
43698 @node MIPS Register packet Format
43699 @subsubsection @acronym{MIPS} Register Packet Format
43700 @cindex register packet format, @acronym{MIPS}
43702 The following @code{g}/@code{G} packets have previously been defined.
43703 In the below, some thirty-two bit registers are transferred as
43704 sixty-four bits. Those registers should be zero/sign extended (which?)
43705 to fill the space allocated. Register bytes are transferred in target
43706 byte order. The two nibbles within a register byte are transferred
43707 most-significant -- least-significant.
43712 All registers are transferred as thirty-two bit quantities in the order:
43713 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
43714 registers; fsr; fir; fp.
43717 All registers are transferred as sixty-four bit quantities (including
43718 thirty-two bit registers such as @code{sr}). The ordering is the same
43723 @node MIPS Breakpoint Kinds
43724 @subsubsection @acronym{MIPS} Breakpoint Kinds
43725 @cindex breakpoint kinds, @acronym{MIPS}
43727 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43732 16-bit @acronym{MIPS16} mode breakpoint.
43735 16-bit @acronym{microMIPS} mode breakpoint.
43738 32-bit standard @acronym{MIPS} mode breakpoint.
43741 32-bit @acronym{microMIPS} mode breakpoint.
43745 @node Tracepoint Packets
43746 @section Tracepoint Packets
43747 @cindex tracepoint packets
43748 @cindex packets, tracepoint
43750 Here we describe the packets @value{GDBN} uses to implement
43751 tracepoints (@pxref{Tracepoints}).
43755 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
43756 @cindex @samp{QTDP} packet
43757 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
43758 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
43759 the tracepoint is disabled. The @var{step} gives the tracepoint's step
43760 count, and @var{pass} gives its pass count. If an @samp{F} is present,
43761 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
43762 the number of bytes that the target should copy elsewhere to make room
43763 for the tracepoint. If an @samp{X} is present, it introduces a
43764 tracepoint condition, which consists of a hexadecimal length, followed
43765 by a comma and hex-encoded bytes, in a manner similar to action
43766 encodings as described below. If the trailing @samp{-} is present,
43767 further @samp{QTDP} packets will follow to specify this tracepoint's
43773 The packet was understood and carried out.
43775 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43777 The packet was not recognized.
43780 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
43781 Define actions to be taken when a tracepoint is hit. The @var{n} and
43782 @var{addr} must be the same as in the initial @samp{QTDP} packet for
43783 this tracepoint. This packet may only be sent immediately after
43784 another @samp{QTDP} packet that ended with a @samp{-}. If the
43785 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
43786 specifying more actions for this tracepoint.
43788 In the series of action packets for a given tracepoint, at most one
43789 can have an @samp{S} before its first @var{action}. If such a packet
43790 is sent, it and the following packets define ``while-stepping''
43791 actions. Any prior packets define ordinary actions --- that is, those
43792 taken when the tracepoint is first hit. If no action packet has an
43793 @samp{S}, then all the packets in the series specify ordinary
43794 tracepoint actions.
43796 The @samp{@var{action}@dots{}} portion of the packet is a series of
43797 actions, concatenated without separators. Each action has one of the
43803 Collect the registers whose bits are set in @var{mask},
43804 a hexadecimal number whose @var{i}'th bit is set if register number
43805 @var{i} should be collected. (The least significant bit is numbered
43806 zero.) Note that @var{mask} may be any number of digits long; it may
43807 not fit in a 32-bit word.
43809 @item M @var{basereg},@var{offset},@var{len}
43810 Collect @var{len} bytes of memory starting at the address in register
43811 number @var{basereg}, plus @var{offset}. If @var{basereg} is
43812 @samp{-1}, then the range has a fixed address: @var{offset} is the
43813 address of the lowest byte to collect. The @var{basereg},
43814 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
43815 values (the @samp{-1} value for @var{basereg} is a special case).
43817 @item X @var{len},@var{expr}
43818 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
43819 it directs. The agent expression @var{expr} is as described in
43820 @ref{Agent Expressions}. Each byte of the expression is encoded as a
43821 two-digit hex number in the packet; @var{len} is the number of bytes
43822 in the expression (and thus one-half the number of hex digits in the
43827 Any number of actions may be packed together in a single @samp{QTDP}
43828 packet, as long as the packet does not exceed the maximum packet
43829 length (400 bytes, for many stubs). There may be only one @samp{R}
43830 action per tracepoint, and it must precede any @samp{M} or @samp{X}
43831 actions. Any registers referred to by @samp{M} and @samp{X} actions
43832 must be collected by a preceding @samp{R} action. (The
43833 ``while-stepping'' actions are treated as if they were attached to a
43834 separate tracepoint, as far as these restrictions are concerned.)
43839 The packet was understood and carried out.
43841 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43843 The packet was not recognized.
43846 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
43847 @cindex @samp{QTDPsrc} packet
43848 Specify a source string of tracepoint @var{n} at address @var{addr}.
43849 This is useful to get accurate reproduction of the tracepoints
43850 originally downloaded at the beginning of the trace run. The @var{type}
43851 is the name of the tracepoint part, such as @samp{cond} for the
43852 tracepoint's conditional expression (see below for a list of types), while
43853 @var{bytes} is the string, encoded in hexadecimal.
43855 @var{start} is the offset of the @var{bytes} within the overall source
43856 string, while @var{slen} is the total length of the source string.
43857 This is intended for handling source strings that are longer than will
43858 fit in a single packet.
43859 @c Add detailed example when this info is moved into a dedicated
43860 @c tracepoint descriptions section.
43862 The available string types are @samp{at} for the location,
43863 @samp{cond} for the conditional, and @samp{cmd} for an action command.
43864 @value{GDBN} sends a separate packet for each command in the action
43865 list, in the same order in which the commands are stored in the list.
43867 The target does not need to do anything with source strings except
43868 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
43871 Although this packet is optional, and @value{GDBN} will only send it
43872 if the target replies with @samp{TracepointSource} @xref{General
43873 Query Packets}, it makes both disconnected tracing and trace files
43874 much easier to use. Otherwise the user must be careful that the
43875 tracepoints in effect while looking at trace frames are identical to
43876 the ones in effect during the trace run; even a small discrepancy
43877 could cause @samp{tdump} not to work, or a particular trace frame not
43880 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
43881 @cindex define trace state variable, remote request
43882 @cindex @samp{QTDV} packet
43883 Create a new trace state variable, number @var{n}, with an initial
43884 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
43885 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
43886 the option of not using this packet for initial values of zero; the
43887 target should simply create the trace state variables as they are
43888 mentioned in expressions. The value @var{builtin} should be 1 (one)
43889 if the trace state variable is builtin and 0 (zero) if it is not builtin.
43890 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
43891 @samp{qTsV} packet had it set. The contents of @var{name} is the
43892 hex-encoded name (without the leading @samp{$}) of the trace state
43895 @item QTFrame:@var{n}
43896 @cindex @samp{QTFrame} packet
43897 Select the @var{n}'th tracepoint frame from the buffer, and use the
43898 register and memory contents recorded there to answer subsequent
43899 request packets from @value{GDBN}.
43901 A successful reply from the stub indicates that the stub has found the
43902 requested frame. The response is a series of parts, concatenated
43903 without separators, describing the frame we selected. Each part has
43904 one of the following forms:
43908 The selected frame is number @var{n} in the trace frame buffer;
43909 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
43910 was no frame matching the criteria in the request packet.
43913 The selected trace frame records a hit of tracepoint number @var{t};
43914 @var{t} is a hexadecimal number.
43918 @item QTFrame:pc:@var{addr}
43919 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43920 currently selected frame whose PC is @var{addr};
43921 @var{addr} is a hexadecimal number.
43923 @item QTFrame:tdp:@var{t}
43924 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43925 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
43926 is a hexadecimal number.
43928 @item QTFrame:range:@var{start}:@var{end}
43929 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43930 currently selected frame whose PC is between @var{start} (inclusive)
43931 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
43934 @item QTFrame:outside:@var{start}:@var{end}
43935 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
43936 frame @emph{outside} the given range of addresses (exclusive).
43939 @cindex @samp{qTMinFTPILen} packet
43940 This packet requests the minimum length of instruction at which a fast
43941 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
43942 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
43943 it depends on the target system being able to create trampolines in
43944 the first 64K of memory, which might or might not be possible for that
43945 system. So the reply to this packet will be 4 if it is able to
43952 The minimum instruction length is currently unknown.
43954 The minimum instruction length is @var{length}, where @var{length}
43955 is a hexadecimal number greater or equal to 1. A reply
43956 of 1 means that a fast tracepoint may be placed on any instruction
43957 regardless of size.
43959 An error has occurred.
43961 An empty reply indicates that the request is not supported by the stub.
43965 @cindex @samp{QTStart} packet
43966 Begin the tracepoint experiment. Begin collecting data from
43967 tracepoint hits in the trace frame buffer. This packet supports the
43968 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
43969 instruction reply packet}).
43972 @cindex @samp{QTStop} packet
43973 End the tracepoint experiment. Stop collecting trace frames.
43975 @item QTEnable:@var{n}:@var{addr}
43977 @cindex @samp{QTEnable} packet
43978 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
43979 experiment. If the tracepoint was previously disabled, then collection
43980 of data from it will resume.
43982 @item QTDisable:@var{n}:@var{addr}
43984 @cindex @samp{QTDisable} packet
43985 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
43986 experiment. No more data will be collected from the tracepoint unless
43987 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
43990 @cindex @samp{QTinit} packet
43991 Clear the table of tracepoints, and empty the trace frame buffer.
43993 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
43994 @cindex @samp{QTro} packet
43995 Establish the given ranges of memory as ``transparent''. The stub
43996 will answer requests for these ranges from memory's current contents,
43997 if they were not collected as part of the tracepoint hit.
43999 @value{GDBN} uses this to mark read-only regions of memory, like those
44000 containing program code. Since these areas never change, they should
44001 still have the same contents they did when the tracepoint was hit, so
44002 there's no reason for the stub to refuse to provide their contents.
44004 @item QTDisconnected:@var{value}
44005 @cindex @samp{QTDisconnected} packet
44006 Set the choice to what to do with the tracing run when @value{GDBN}
44007 disconnects from the target. A @var{value} of 1 directs the target to
44008 continue the tracing run, while 0 tells the target to stop tracing if
44009 @value{GDBN} is no longer in the picture.
44012 @cindex @samp{qTStatus} packet
44013 Ask the stub if there is a trace experiment running right now.
44015 The reply has the form:
44019 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
44020 @var{running} is a single digit @code{1} if the trace is presently
44021 running, or @code{0} if not. It is followed by semicolon-separated
44022 optional fields that an agent may use to report additional status.
44026 If the trace is not running, the agent may report any of several
44027 explanations as one of the optional fields:
44032 No trace has been run yet.
44034 @item tstop[:@var{text}]:0
44035 The trace was stopped by a user-originated stop command. The optional
44036 @var{text} field is a user-supplied string supplied as part of the
44037 stop command (for instance, an explanation of why the trace was
44038 stopped manually). It is hex-encoded.
44041 The trace stopped because the trace buffer filled up.
44043 @item tdisconnected:0
44044 The trace stopped because @value{GDBN} disconnected from the target.
44046 @item tpasscount:@var{tpnum}
44047 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
44049 @item terror:@var{text}:@var{tpnum}
44050 The trace stopped because tracepoint @var{tpnum} had an error. The
44051 string @var{text} is available to describe the nature of the error
44052 (for instance, a divide by zero in the condition expression); it
44056 The trace stopped for some other reason.
44060 Additional optional fields supply statistical and other information.
44061 Although not required, they are extremely useful for users monitoring
44062 the progress of a trace run. If a trace has stopped, and these
44063 numbers are reported, they must reflect the state of the just-stopped
44068 @item tframes:@var{n}
44069 The number of trace frames in the buffer.
44071 @item tcreated:@var{n}
44072 The total number of trace frames created during the run. This may
44073 be larger than the trace frame count, if the buffer is circular.
44075 @item tsize:@var{n}
44076 The total size of the trace buffer, in bytes.
44078 @item tfree:@var{n}
44079 The number of bytes still unused in the buffer.
44081 @item circular:@var{n}
44082 The value of the circular trace buffer flag. @code{1} means that the
44083 trace buffer is circular and old trace frames will be discarded if
44084 necessary to make room, @code{0} means that the trace buffer is linear
44087 @item disconn:@var{n}
44088 The value of the disconnected tracing flag. @code{1} means that
44089 tracing will continue after @value{GDBN} disconnects, @code{0} means
44090 that the trace run will stop.
44094 @item qTP:@var{tp}:@var{addr}
44095 @cindex tracepoint status, remote request
44096 @cindex @samp{qTP} packet
44097 Ask the stub for the current state of tracepoint number @var{tp} at
44098 address @var{addr}.
44102 @item V@var{hits}:@var{usage}
44103 The tracepoint has been hit @var{hits} times so far during the trace
44104 run, and accounts for @var{usage} in the trace buffer. Note that
44105 @code{while-stepping} steps are not counted as separate hits, but the
44106 steps' space consumption is added into the usage number.
44110 @item qTV:@var{var}
44111 @cindex trace state variable value, remote request
44112 @cindex @samp{qTV} packet
44113 Ask the stub for the value of the trace state variable number @var{var}.
44118 The value of the variable is @var{value}. This will be the current
44119 value of the variable if the user is examining a running target, or a
44120 saved value if the variable was collected in the trace frame that the
44121 user is looking at. Note that multiple requests may result in
44122 different reply values, such as when requesting values while the
44123 program is running.
44126 The value of the variable is unknown. This would occur, for example,
44127 if the user is examining a trace frame in which the requested variable
44132 @cindex @samp{qTfP} packet
44134 @cindex @samp{qTsP} packet
44135 These packets request data about tracepoints that are being used by
44136 the target. @value{GDBN} sends @code{qTfP} to get the first piece
44137 of data, and multiple @code{qTsP} to get additional pieces. Replies
44138 to these packets generally take the form of the @code{QTDP} packets
44139 that define tracepoints. (FIXME add detailed syntax)
44142 @cindex @samp{qTfV} packet
44144 @cindex @samp{qTsV} packet
44145 These packets request data about trace state variables that are on the
44146 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
44147 and multiple @code{qTsV} to get additional variables. Replies to
44148 these packets follow the syntax of the @code{QTDV} packets that define
44149 trace state variables.
44155 @cindex @samp{qTfSTM} packet
44156 @cindex @samp{qTsSTM} packet
44157 These packets request data about static tracepoint markers that exist
44158 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
44159 first piece of data, and multiple @code{qTsSTM} to get additional
44160 pieces. Replies to these packets take the following form:
44164 @item m @var{address}:@var{id}:@var{extra}
44166 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
44167 a comma-separated list of markers
44169 (lower case letter @samp{L}) denotes end of list.
44171 An error occurred. The error number @var{nn} is given as hex digits.
44173 An empty reply indicates that the request is not supported by the
44177 The @var{address} is encoded in hex;
44178 @var{id} and @var{extra} are strings encoded in hex.
44180 In response to each query, the target will reply with a list of one or
44181 more markers, separated by commas. @value{GDBN} will respond to each
44182 reply with a request for more markers (using the @samp{qs} form of the
44183 query), until the target responds with @samp{l} (lower-case ell, for
44186 @item qTSTMat:@var{address}
44188 @cindex @samp{qTSTMat} packet
44189 This packets requests data about static tracepoint markers in the
44190 target program at @var{address}. Replies to this packet follow the
44191 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
44192 tracepoint markers.
44194 @item QTSave:@var{filename}
44195 @cindex @samp{QTSave} packet
44196 This packet directs the target to save trace data to the file name
44197 @var{filename} in the target's filesystem. The @var{filename} is encoded
44198 as a hex string; the interpretation of the file name (relative vs
44199 absolute, wild cards, etc) is up to the target.
44201 @item qTBuffer:@var{offset},@var{len}
44202 @cindex @samp{qTBuffer} packet
44203 Return up to @var{len} bytes of the current contents of trace buffer,
44204 starting at @var{offset}. The trace buffer is treated as if it were
44205 a contiguous collection of traceframes, as per the trace file format.
44206 The reply consists as many hex-encoded bytes as the target can deliver
44207 in a packet; it is not an error to return fewer than were asked for.
44208 A reply consisting of just @code{l} indicates that no bytes are
44211 @item QTBuffer:circular:@var{value}
44212 This packet directs the target to use a circular trace buffer if
44213 @var{value} is 1, or a linear buffer if the value is 0.
44215 @item QTBuffer:size:@var{size}
44216 @anchor{QTBuffer-size}
44217 @cindex @samp{QTBuffer size} packet
44218 This packet directs the target to make the trace buffer be of size
44219 @var{size} if possible. A value of @code{-1} tells the target to
44220 use whatever size it prefers.
44222 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
44223 @cindex @samp{QTNotes} packet
44224 This packet adds optional textual notes to the trace run. Allowable
44225 types include @code{user}, @code{notes}, and @code{tstop}, the
44226 @var{text} fields are arbitrary strings, hex-encoded.
44230 @subsection Relocate instruction reply packet
44231 When installing fast tracepoints in memory, the target may need to
44232 relocate the instruction currently at the tracepoint address to a
44233 different address in memory. For most instructions, a simple copy is
44234 enough, but, for example, call instructions that implicitly push the
44235 return address on the stack, and relative branches or other
44236 PC-relative instructions require offset adjustment, so that the effect
44237 of executing the instruction at a different address is the same as if
44238 it had executed in the original location.
44240 In response to several of the tracepoint packets, the target may also
44241 respond with a number of intermediate @samp{qRelocInsn} request
44242 packets before the final result packet, to have @value{GDBN} handle
44243 this relocation operation. If a packet supports this mechanism, its
44244 documentation will explicitly say so. See for example the above
44245 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
44246 format of the request is:
44249 @item qRelocInsn:@var{from};@var{to}
44251 This requests @value{GDBN} to copy instruction at address @var{from}
44252 to address @var{to}, possibly adjusted so that executing the
44253 instruction at @var{to} has the same effect as executing it at
44254 @var{from}. @value{GDBN} writes the adjusted instruction to target
44255 memory starting at @var{to}.
44260 @item qRelocInsn:@var{adjusted_size}
44261 Informs the stub the relocation is complete. The @var{adjusted_size} is
44262 the length in bytes of resulting relocated instruction sequence.
44264 A badly formed request was detected, or an error was encountered while
44265 relocating the instruction.
44268 @node Host I/O Packets
44269 @section Host I/O Packets
44270 @cindex Host I/O, remote protocol
44271 @cindex file transfer, remote protocol
44273 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
44274 operations on the far side of a remote link. For example, Host I/O is
44275 used to upload and download files to a remote target with its own
44276 filesystem. Host I/O uses the same constant values and data structure
44277 layout as the target-initiated File-I/O protocol. However, the
44278 Host I/O packets are structured differently. The target-initiated
44279 protocol relies on target memory to store parameters and buffers.
44280 Host I/O requests are initiated by @value{GDBN}, and the
44281 target's memory is not involved. @xref{File-I/O Remote Protocol
44282 Extension}, for more details on the target-initiated protocol.
44284 The Host I/O request packets all encode a single operation along with
44285 its arguments. They have this format:
44289 @item vFile:@var{operation}: @var{parameter}@dots{}
44290 @var{operation} is the name of the particular request; the target
44291 should compare the entire packet name up to the second colon when checking
44292 for a supported operation. The format of @var{parameter} depends on
44293 the operation. Numbers are always passed in hexadecimal. Negative
44294 numbers have an explicit minus sign (i.e.@: two's complement is not
44295 used). Strings (e.g.@: filenames) are encoded as a series of
44296 hexadecimal bytes. The last argument to a system call may be a
44297 buffer of escaped binary data (@pxref{Binary Data}).
44301 The valid responses to Host I/O packets are:
44305 @item F @var{result} [, @var{errno}] [; @var{attachment}]
44306 @var{result} is the integer value returned by this operation, usually
44307 non-negative for success and -1 for errors. If an error has occured,
44308 @var{errno} will be included in the result specifying a
44309 value defined by the File-I/O protocol (@pxref{Errno Values}). For
44310 operations which return data, @var{attachment} supplies the data as a
44311 binary buffer. Binary buffers in response packets are escaped in the
44312 normal way (@pxref{Binary Data}). See the individual packet
44313 documentation for the interpretation of @var{result} and
44317 An empty response indicates that this operation is not recognized.
44321 These are the supported Host I/O operations:
44324 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
44325 Open a file at @var{filename} and return a file descriptor for it, or
44326 return -1 if an error occurs. The @var{filename} is a string,
44327 @var{flags} is an integer indicating a mask of open flags
44328 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
44329 of mode bits to use if the file is created (@pxref{mode_t Values}).
44330 @xref{open}, for details of the open flags and mode values.
44332 @item vFile:close: @var{fd}
44333 Close the open file corresponding to @var{fd} and return 0, or
44334 -1 if an error occurs.
44336 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
44337 Read data from the open file corresponding to @var{fd}. Up to
44338 @var{count} bytes will be read from the file, starting at @var{offset}
44339 relative to the start of the file. The target may read fewer bytes;
44340 common reasons include packet size limits and an end-of-file
44341 condition. The number of bytes read is returned. Zero should only be
44342 returned for a successful read at the end of the file, or if
44343 @var{count} was zero.
44345 The data read should be returned as a binary attachment on success.
44346 If zero bytes were read, the response should include an empty binary
44347 attachment (i.e.@: a trailing semicolon). The return value is the
44348 number of target bytes read; the binary attachment may be longer if
44349 some characters were escaped.
44351 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
44352 Write @var{data} (a binary buffer) to the open file corresponding
44353 to @var{fd}. Start the write at @var{offset} from the start of the
44354 file. Unlike many @code{write} system calls, there is no
44355 separate @var{count} argument; the length of @var{data} in the
44356 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
44357 which may be shorter than the length of @var{data}, or -1 if an
44360 @item vFile:fstat: @var{fd}
44361 Get information about the open file corresponding to @var{fd}.
44362 On success the information is returned as a binary attachment
44363 and the return value is the size of this attachment in bytes.
44364 If an error occurs the return value is -1. The format of the
44365 returned binary attachment is as described in @ref{struct stat}.
44367 @item vFile:unlink: @var{filename}
44368 Delete the file at @var{filename} on the target. Return 0,
44369 or -1 if an error occurs. The @var{filename} is a string.
44371 @item vFile:readlink: @var{filename}
44372 Read value of symbolic link @var{filename} on the target. Return
44373 the number of bytes read, or -1 if an error occurs.
44375 The data read should be returned as a binary attachment on success.
44376 If zero bytes were read, the response should include an empty binary
44377 attachment (i.e.@: a trailing semicolon). The return value is the
44378 number of target bytes read; the binary attachment may be longer if
44379 some characters were escaped.
44381 @item vFile:setfs: @var{pid}
44382 Select the filesystem on which @code{vFile} operations with
44383 @var{filename} arguments will operate. This is required for
44384 @value{GDBN} to be able to access files on remote targets where
44385 the remote stub does not share a common filesystem with the
44388 If @var{pid} is nonzero, select the filesystem as seen by process
44389 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
44390 the remote stub. Return 0 on success, or -1 if an error occurs.
44391 If @code{vFile:setfs:} indicates success, the selected filesystem
44392 remains selected until the next successful @code{vFile:setfs:}
44398 @section Interrupts
44399 @cindex interrupts (remote protocol)
44400 @anchor{interrupting remote targets}
44402 In all-stop mode, when a program on the remote target is running,
44403 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
44404 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
44405 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
44407 The precise meaning of @code{BREAK} is defined by the transport
44408 mechanism and may, in fact, be undefined. @value{GDBN} does not
44409 currently define a @code{BREAK} mechanism for any of the network
44410 interfaces except for TCP, in which case @value{GDBN} sends the
44411 @code{telnet} BREAK sequence.
44413 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
44414 transport mechanisms. It is represented by sending the single byte
44415 @code{0x03} without any of the usual packet overhead described in
44416 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
44417 transmitted as part of a packet, it is considered to be packet data
44418 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
44419 (@pxref{X packet}), used for binary downloads, may include an unescaped
44420 @code{0x03} as part of its packet.
44422 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
44423 When Linux kernel receives this sequence from serial port,
44424 it stops execution and connects to gdb.
44426 In non-stop mode, because packet resumptions are asynchronous
44427 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
44428 command to the remote stub, even when the target is running. For that
44429 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
44430 packet}) with the usual packet framing instead of the single byte
44433 Stubs are not required to recognize these interrupt mechanisms and the
44434 precise meaning associated with receipt of the interrupt is
44435 implementation defined. If the target supports debugging of multiple
44436 threads and/or processes, it should attempt to interrupt all
44437 currently-executing threads and processes.
44438 If the stub is successful at interrupting the
44439 running program, it should send one of the stop
44440 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
44441 of successfully stopping the program in all-stop mode, and a stop reply
44442 for each stopped thread in non-stop mode.
44443 Interrupts received while the
44444 program is stopped are queued and the program will be interrupted when
44445 it is resumed next time.
44447 @node Notification Packets
44448 @section Notification Packets
44449 @cindex notification packets
44450 @cindex packets, notification
44452 The @value{GDBN} remote serial protocol includes @dfn{notifications},
44453 packets that require no acknowledgment. Both the GDB and the stub
44454 may send notifications (although the only notifications defined at
44455 present are sent by the stub). Notifications carry information
44456 without incurring the round-trip latency of an acknowledgment, and so
44457 are useful for low-impact communications where occasional packet loss
44460 A notification packet has the form @samp{% @var{data} #
44461 @var{checksum}}, where @var{data} is the content of the notification,
44462 and @var{checksum} is a checksum of @var{data}, computed and formatted
44463 as for ordinary @value{GDBN} packets. A notification's @var{data}
44464 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
44465 receiving a notification, the recipient sends no @samp{+} or @samp{-}
44466 to acknowledge the notification's receipt or to report its corruption.
44468 Every notification's @var{data} begins with a name, which contains no
44469 colon characters, followed by a colon character.
44471 Recipients should silently ignore corrupted notifications and
44472 notifications they do not understand. Recipients should restart
44473 timeout periods on receipt of a well-formed notification, whether or
44474 not they understand it.
44476 Senders should only send the notifications described here when this
44477 protocol description specifies that they are permitted. In the
44478 future, we may extend the protocol to permit existing notifications in
44479 new contexts; this rule helps older senders avoid confusing newer
44482 (Older versions of @value{GDBN} ignore bytes received until they see
44483 the @samp{$} byte that begins an ordinary packet, so new stubs may
44484 transmit notifications without fear of confusing older clients. There
44485 are no notifications defined for @value{GDBN} to send at the moment, but we
44486 assume that most older stubs would ignore them, as well.)
44488 Each notification is comprised of three parts:
44490 @item @var{name}:@var{event}
44491 The notification packet is sent by the side that initiates the
44492 exchange (currently, only the stub does that), with @var{event}
44493 carrying the specific information about the notification, and
44494 @var{name} specifying the name of the notification.
44496 The acknowledge sent by the other side, usually @value{GDBN}, to
44497 acknowledge the exchange and request the event.
44500 The purpose of an asynchronous notification mechanism is to report to
44501 @value{GDBN} that something interesting happened in the remote stub.
44503 The remote stub may send notification @var{name}:@var{event}
44504 at any time, but @value{GDBN} acknowledges the notification when
44505 appropriate. The notification event is pending before @value{GDBN}
44506 acknowledges. Only one notification at a time may be pending; if
44507 additional events occur before @value{GDBN} has acknowledged the
44508 previous notification, they must be queued by the stub for later
44509 synchronous transmission in response to @var{ack} packets from
44510 @value{GDBN}. Because the notification mechanism is unreliable,
44511 the stub is permitted to resend a notification if it believes
44512 @value{GDBN} may not have received it.
44514 Specifically, notifications may appear when @value{GDBN} is not
44515 otherwise reading input from the stub, or when @value{GDBN} is
44516 expecting to read a normal synchronous response or a
44517 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
44518 Notification packets are distinct from any other communication from
44519 the stub so there is no ambiguity.
44521 After receiving a notification, @value{GDBN} shall acknowledge it by
44522 sending a @var{ack} packet as a regular, synchronous request to the
44523 stub. Such acknowledgment is not required to happen immediately, as
44524 @value{GDBN} is permitted to send other, unrelated packets to the
44525 stub first, which the stub should process normally.
44527 Upon receiving a @var{ack} packet, if the stub has other queued
44528 events to report to @value{GDBN}, it shall respond by sending a
44529 normal @var{event}. @value{GDBN} shall then send another @var{ack}
44530 packet to solicit further responses; again, it is permitted to send
44531 other, unrelated packets as well which the stub should process
44534 If the stub receives a @var{ack} packet and there are no additional
44535 @var{event} to report, the stub shall return an @samp{OK} response.
44536 At this point, @value{GDBN} has finished processing a notification
44537 and the stub has completed sending any queued events. @value{GDBN}
44538 won't accept any new notifications until the final @samp{OK} is
44539 received . If further notification events occur, the stub shall send
44540 a new notification, @value{GDBN} shall accept the notification, and
44541 the process shall be repeated.
44543 The process of asynchronous notification can be illustrated by the
44546 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
44549 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
44551 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
44556 The following notifications are defined:
44557 @multitable @columnfractions 0.12 0.12 0.38 0.38
44566 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
44567 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
44568 for information on how these notifications are acknowledged by
44570 @tab Report an asynchronous stop event in non-stop mode.
44574 @node Remote Non-Stop
44575 @section Remote Protocol Support for Non-Stop Mode
44577 @value{GDBN}'s remote protocol supports non-stop debugging of
44578 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
44579 supports non-stop mode, it should report that to @value{GDBN} by including
44580 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
44582 @value{GDBN} typically sends a @samp{QNonStop} packet only when
44583 establishing a new connection with the stub. Entering non-stop mode
44584 does not alter the state of any currently-running threads, but targets
44585 must stop all threads in any already-attached processes when entering
44586 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
44587 probe the target state after a mode change.
44589 In non-stop mode, when an attached process encounters an event that
44590 would otherwise be reported with a stop reply, it uses the
44591 asynchronous notification mechanism (@pxref{Notification Packets}) to
44592 inform @value{GDBN}. In contrast to all-stop mode, where all threads
44593 in all processes are stopped when a stop reply is sent, in non-stop
44594 mode only the thread reporting the stop event is stopped. That is,
44595 when reporting a @samp{S} or @samp{T} response to indicate completion
44596 of a step operation, hitting a breakpoint, or a fault, only the
44597 affected thread is stopped; any other still-running threads continue
44598 to run. When reporting a @samp{W} or @samp{X} response, all running
44599 threads belonging to other attached processes continue to run.
44601 In non-stop mode, the target shall respond to the @samp{?} packet as
44602 follows. First, any incomplete stop reply notification/@samp{vStopped}
44603 sequence in progress is abandoned. The target must begin a new
44604 sequence reporting stop events for all stopped threads, whether or not
44605 it has previously reported those events to @value{GDBN}. The first
44606 stop reply is sent as a synchronous reply to the @samp{?} packet, and
44607 subsequent stop replies are sent as responses to @samp{vStopped} packets
44608 using the mechanism described above. The target must not send
44609 asynchronous stop reply notifications until the sequence is complete.
44610 If all threads are running when the target receives the @samp{?} packet,
44611 or if the target is not attached to any process, it shall respond
44614 If the stub supports non-stop mode, it should also support the
44615 @samp{swbreak} stop reason if software breakpoints are supported, and
44616 the @samp{hwbreak} stop reason if hardware breakpoints are supported
44617 (@pxref{swbreak stop reason}). This is because given the asynchronous
44618 nature of non-stop mode, between the time a thread hits a breakpoint
44619 and the time the event is finally processed by @value{GDBN}, the
44620 breakpoint may have already been removed from the target. Due to
44621 this, @value{GDBN} needs to be able to tell whether a trap stop was
44622 caused by a delayed breakpoint event, which should be ignored, as
44623 opposed to a random trap signal, which should be reported to the user.
44624 Note the @samp{swbreak} feature implies that the target is responsible
44625 for adjusting the PC when a software breakpoint triggers, if
44626 necessary, such as on the x86 architecture.
44628 @node Packet Acknowledgment
44629 @section Packet Acknowledgment
44631 @cindex acknowledgment, for @value{GDBN} remote
44632 @cindex packet acknowledgment, for @value{GDBN} remote
44633 By default, when either the host or the target machine receives a packet,
44634 the first response expected is an acknowledgment: either @samp{+} (to indicate
44635 the package was received correctly) or @samp{-} (to request retransmission).
44636 This mechanism allows the @value{GDBN} remote protocol to operate over
44637 unreliable transport mechanisms, such as a serial line.
44639 In cases where the transport mechanism is itself reliable (such as a pipe or
44640 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
44641 It may be desirable to disable them in that case to reduce communication
44642 overhead, or for other reasons. This can be accomplished by means of the
44643 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
44645 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
44646 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
44647 and response format still includes the normal checksum, as described in
44648 @ref{Overview}, but the checksum may be ignored by the receiver.
44650 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
44651 no-acknowledgment mode, it should report that to @value{GDBN}
44652 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
44653 @pxref{qSupported}.
44654 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
44655 disabled via the @code{set remote noack-packet off} command
44656 (@pxref{Remote Configuration}),
44657 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
44658 Only then may the stub actually turn off packet acknowledgments.
44659 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
44660 response, which can be safely ignored by the stub.
44662 Note that @code{set remote noack-packet} command only affects negotiation
44663 between @value{GDBN} and the stub when subsequent connections are made;
44664 it does not affect the protocol acknowledgment state for any current
44666 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
44667 new connection is established,
44668 there is also no protocol request to re-enable the acknowledgments
44669 for the current connection, once disabled.
44674 Example sequence of a target being re-started. Notice how the restart
44675 does not get any direct output:
44680 @emph{target restarts}
44683 <- @code{T001:1234123412341234}
44687 Example sequence of a target being stepped by a single instruction:
44690 -> @code{G1445@dots{}}
44695 <- @code{T001:1234123412341234}
44699 <- @code{1455@dots{}}
44703 @node File-I/O Remote Protocol Extension
44704 @section File-I/O Remote Protocol Extension
44705 @cindex File-I/O remote protocol extension
44708 * File-I/O Overview::
44709 * Protocol Basics::
44710 * The F Request Packet::
44711 * The F Reply Packet::
44712 * The Ctrl-C Message::
44714 * List of Supported Calls::
44715 * Protocol-specific Representation of Datatypes::
44717 * File-I/O Examples::
44720 @node File-I/O Overview
44721 @subsection File-I/O Overview
44722 @cindex file-i/o overview
44724 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
44725 target to use the host's file system and console I/O to perform various
44726 system calls. System calls on the target system are translated into a
44727 remote protocol packet to the host system, which then performs the needed
44728 actions and returns a response packet to the target system.
44729 This simulates file system operations even on targets that lack file systems.
44731 The protocol is defined to be independent of both the host and target systems.
44732 It uses its own internal representation of datatypes and values. Both
44733 @value{GDBN} and the target's @value{GDBN} stub are responsible for
44734 translating the system-dependent value representations into the internal
44735 protocol representations when data is transmitted.
44737 The communication is synchronous. A system call is possible only when
44738 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
44739 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
44740 the target is stopped to allow deterministic access to the target's
44741 memory. Therefore File-I/O is not interruptible by target signals. On
44742 the other hand, it is possible to interrupt File-I/O by a user interrupt
44743 (@samp{Ctrl-C}) within @value{GDBN}.
44745 The target's request to perform a host system call does not finish
44746 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
44747 after finishing the system call, the target returns to continuing the
44748 previous activity (continue, step). No additional continue or step
44749 request from @value{GDBN} is required.
44752 (@value{GDBP}) continue
44753 <- target requests 'system call X'
44754 target is stopped, @value{GDBN} executes system call
44755 -> @value{GDBN} returns result
44756 ... target continues, @value{GDBN} returns to wait for the target
44757 <- target hits breakpoint and sends a Txx packet
44760 The protocol only supports I/O on the console and to regular files on
44761 the host file system. Character or block special devices, pipes,
44762 named pipes, sockets or any other communication method on the host
44763 system are not supported by this protocol.
44765 File I/O is not supported in non-stop mode.
44767 @node Protocol Basics
44768 @subsection Protocol Basics
44769 @cindex protocol basics, file-i/o
44771 The File-I/O protocol uses the @code{F} packet as the request as well
44772 as reply packet. Since a File-I/O system call can only occur when
44773 @value{GDBN} is waiting for a response from the continuing or stepping target,
44774 the File-I/O request is a reply that @value{GDBN} has to expect as a result
44775 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
44776 This @code{F} packet contains all information needed to allow @value{GDBN}
44777 to call the appropriate host system call:
44781 A unique identifier for the requested system call.
44784 All parameters to the system call. Pointers are given as addresses
44785 in the target memory address space. Pointers to strings are given as
44786 pointer/length pair. Numerical values are given as they are.
44787 Numerical control flags are given in a protocol-specific representation.
44791 At this point, @value{GDBN} has to perform the following actions.
44795 If the parameters include pointer values to data needed as input to a
44796 system call, @value{GDBN} requests this data from the target with a
44797 standard @code{m} packet request. This additional communication has to be
44798 expected by the target implementation and is handled as any other @code{m}
44802 @value{GDBN} translates all value from protocol representation to host
44803 representation as needed. Datatypes are coerced into the host types.
44806 @value{GDBN} calls the system call.
44809 It then coerces datatypes back to protocol representation.
44812 If the system call is expected to return data in buffer space specified
44813 by pointer parameters to the call, the data is transmitted to the
44814 target using a @code{M} or @code{X} packet. This packet has to be expected
44815 by the target implementation and is handled as any other @code{M} or @code{X}
44820 Eventually @value{GDBN} replies with another @code{F} packet which contains all
44821 necessary information for the target to continue. This at least contains
44828 @code{errno}, if has been changed by the system call.
44835 After having done the needed type and value coercion, the target continues
44836 the latest continue or step action.
44838 @node The F Request Packet
44839 @subsection The @code{F} Request Packet
44840 @cindex file-i/o request packet
44841 @cindex @code{F} request packet
44843 The @code{F} request packet has the following format:
44846 @item F@var{call-id},@var{parameter@dots{}}
44848 @var{call-id} is the identifier to indicate the host system call to be called.
44849 This is just the name of the function.
44851 @var{parameter@dots{}} are the parameters to the system call.
44852 Parameters are hexadecimal integer values, either the actual values in case
44853 of scalar datatypes, pointers to target buffer space in case of compound
44854 datatypes and unspecified memory areas, or pointer/length pairs in case
44855 of string parameters. These are appended to the @var{call-id} as a
44856 comma-delimited list. All values are transmitted in ASCII
44857 string representation, pointer/length pairs separated by a slash.
44863 @node The F Reply Packet
44864 @subsection The @code{F} Reply Packet
44865 @cindex file-i/o reply packet
44866 @cindex @code{F} reply packet
44868 The @code{F} reply packet has the following format:
44872 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
44874 @var{retcode} is the return code of the system call as hexadecimal value.
44876 @var{errno} is the @code{errno} set by the call, in protocol-specific
44878 This parameter can be omitted if the call was successful.
44880 @var{Ctrl-C flag} is only sent if the user requested a break. In this
44881 case, @var{errno} must be sent as well, even if the call was successful.
44882 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
44889 or, if the call was interrupted before the host call has been performed:
44896 assuming 4 is the protocol-specific representation of @code{EINTR}.
44901 @node The Ctrl-C Message
44902 @subsection The @samp{Ctrl-C} Message
44903 @cindex ctrl-c message, in file-i/o protocol
44905 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
44906 reply packet (@pxref{The F Reply Packet}),
44907 the target should behave as if it had
44908 gotten a break message. The meaning for the target is ``system call
44909 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
44910 (as with a break message) and return to @value{GDBN} with a @code{T02}
44913 It's important for the target to know in which
44914 state the system call was interrupted. There are two possible cases:
44918 The system call hasn't been performed on the host yet.
44921 The system call on the host has been finished.
44925 These two states can be distinguished by the target by the value of the
44926 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
44927 call hasn't been performed. This is equivalent to the @code{EINTR} handling
44928 on POSIX systems. In any other case, the target may presume that the
44929 system call has been finished --- successfully or not --- and should behave
44930 as if the break message arrived right after the system call.
44932 @value{GDBN} must behave reliably. If the system call has not been called
44933 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
44934 @code{errno} in the packet. If the system call on the host has been finished
44935 before the user requests a break, the full action must be finished by
44936 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
44937 The @code{F} packet may only be sent when either nothing has happened
44938 or the full action has been completed.
44941 @subsection Console I/O
44942 @cindex console i/o as part of file-i/o
44944 By default and if not explicitly closed by the target system, the file
44945 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
44946 on the @value{GDBN} console is handled as any other file output operation
44947 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
44948 by @value{GDBN} so that after the target read request from file descriptor
44949 0 all following typing is buffered until either one of the following
44954 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
44956 system call is treated as finished.
44959 The user presses @key{RET}. This is treated as end of input with a trailing
44963 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
44964 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
44968 If the user has typed more characters than fit in the buffer given to
44969 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
44970 either another @code{read(0, @dots{})} is requested by the target, or debugging
44971 is stopped at the user's request.
44974 @node List of Supported Calls
44975 @subsection List of Supported Calls
44976 @cindex list of supported file-i/o calls
44993 @unnumberedsubsubsec open
44994 @cindex open, file-i/o system call
44999 int open(const char *pathname, int flags);
45000 int open(const char *pathname, int flags, mode_t mode);
45004 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
45007 @var{flags} is the bitwise @code{OR} of the following values:
45011 If the file does not exist it will be created. The host
45012 rules apply as far as file ownership and time stamps
45016 When used with @code{O_CREAT}, if the file already exists it is
45017 an error and open() fails.
45020 If the file already exists and the open mode allows
45021 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
45022 truncated to zero length.
45025 The file is opened in append mode.
45028 The file is opened for reading only.
45031 The file is opened for writing only.
45034 The file is opened for reading and writing.
45038 Other bits are silently ignored.
45042 @var{mode} is the bitwise @code{OR} of the following values:
45046 User has read permission.
45049 User has write permission.
45052 Group has read permission.
45055 Group has write permission.
45058 Others have read permission.
45061 Others have write permission.
45065 Other bits are silently ignored.
45068 @item Return value:
45069 @code{open} returns the new file descriptor or -1 if an error
45076 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
45079 @var{pathname} refers to a directory.
45082 The requested access is not allowed.
45085 @var{pathname} was too long.
45088 A directory component in @var{pathname} does not exist.
45091 @var{pathname} refers to a device, pipe, named pipe or socket.
45094 @var{pathname} refers to a file on a read-only filesystem and
45095 write access was requested.
45098 @var{pathname} is an invalid pointer value.
45101 No space on device to create the file.
45104 The process already has the maximum number of files open.
45107 The limit on the total number of files open on the system
45111 The call was interrupted by the user.
45117 @unnumberedsubsubsec close
45118 @cindex close, file-i/o system call
45127 @samp{Fclose,@var{fd}}
45129 @item Return value:
45130 @code{close} returns zero on success, or -1 if an error occurred.
45136 @var{fd} isn't a valid open file descriptor.
45139 The call was interrupted by the user.
45145 @unnumberedsubsubsec read
45146 @cindex read, file-i/o system call
45151 int read(int fd, void *buf, unsigned int count);
45155 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
45157 @item Return value:
45158 On success, the number of bytes read is returned.
45159 Zero indicates end of file. If count is zero, read
45160 returns zero as well. On error, -1 is returned.
45166 @var{fd} is not a valid file descriptor or is not open for
45170 @var{bufptr} is an invalid pointer value.
45173 The call was interrupted by the user.
45179 @unnumberedsubsubsec write
45180 @cindex write, file-i/o system call
45185 int write(int fd, const void *buf, unsigned int count);
45189 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
45191 @item Return value:
45192 On success, the number of bytes written are returned.
45193 Zero indicates nothing was written. On error, -1
45200 @var{fd} is not a valid file descriptor or is not open for
45204 @var{bufptr} is an invalid pointer value.
45207 An attempt was made to write a file that exceeds the
45208 host-specific maximum file size allowed.
45211 No space on device to write the data.
45214 The call was interrupted by the user.
45220 @unnumberedsubsubsec lseek
45221 @cindex lseek, file-i/o system call
45226 long lseek (int fd, long offset, int flag);
45230 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
45232 @var{flag} is one of:
45236 The offset is set to @var{offset} bytes.
45239 The offset is set to its current location plus @var{offset}
45243 The offset is set to the size of the file plus @var{offset}
45247 @item Return value:
45248 On success, the resulting unsigned offset in bytes from
45249 the beginning of the file is returned. Otherwise, a
45250 value of -1 is returned.
45256 @var{fd} is not a valid open file descriptor.
45259 @var{fd} is associated with the @value{GDBN} console.
45262 @var{flag} is not a proper value.
45265 The call was interrupted by the user.
45271 @unnumberedsubsubsec rename
45272 @cindex rename, file-i/o system call
45277 int rename(const char *oldpath, const char *newpath);
45281 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
45283 @item Return value:
45284 On success, zero is returned. On error, -1 is returned.
45290 @var{newpath} is an existing directory, but @var{oldpath} is not a
45294 @var{newpath} is a non-empty directory.
45297 @var{oldpath} or @var{newpath} is a directory that is in use by some
45301 An attempt was made to make a directory a subdirectory
45305 A component used as a directory in @var{oldpath} or new
45306 path is not a directory. Or @var{oldpath} is a directory
45307 and @var{newpath} exists but is not a directory.
45310 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
45313 No access to the file or the path of the file.
45317 @var{oldpath} or @var{newpath} was too long.
45320 A directory component in @var{oldpath} or @var{newpath} does not exist.
45323 The file is on a read-only filesystem.
45326 The device containing the file has no room for the new
45330 The call was interrupted by the user.
45336 @unnumberedsubsubsec unlink
45337 @cindex unlink, file-i/o system call
45342 int unlink(const char *pathname);
45346 @samp{Funlink,@var{pathnameptr}/@var{len}}
45348 @item Return value:
45349 On success, zero is returned. On error, -1 is returned.
45355 No access to the file or the path of the file.
45358 The system does not allow unlinking of directories.
45361 The file @var{pathname} cannot be unlinked because it's
45362 being used by another process.
45365 @var{pathnameptr} is an invalid pointer value.
45368 @var{pathname} was too long.
45371 A directory component in @var{pathname} does not exist.
45374 A component of the path is not a directory.
45377 The file is on a read-only filesystem.
45380 The call was interrupted by the user.
45386 @unnumberedsubsubsec stat/fstat
45387 @cindex fstat, file-i/o system call
45388 @cindex stat, file-i/o system call
45393 int stat(const char *pathname, struct stat *buf);
45394 int fstat(int fd, struct stat *buf);
45398 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
45399 @samp{Ffstat,@var{fd},@var{bufptr}}
45401 @item Return value:
45402 On success, zero is returned. On error, -1 is returned.
45408 @var{fd} is not a valid open file.
45411 A directory component in @var{pathname} does not exist or the
45412 path is an empty string.
45415 A component of the path is not a directory.
45418 @var{pathnameptr} is an invalid pointer value.
45421 No access to the file or the path of the file.
45424 @var{pathname} was too long.
45427 The call was interrupted by the user.
45433 @unnumberedsubsubsec gettimeofday
45434 @cindex gettimeofday, file-i/o system call
45439 int gettimeofday(struct timeval *tv, void *tz);
45443 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
45445 @item Return value:
45446 On success, 0 is returned, -1 otherwise.
45452 @var{tz} is a non-NULL pointer.
45455 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
45461 @unnumberedsubsubsec isatty
45462 @cindex isatty, file-i/o system call
45467 int isatty(int fd);
45471 @samp{Fisatty,@var{fd}}
45473 @item Return value:
45474 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45480 The call was interrupted by the user.
45485 Note that the @code{isatty} call is treated as a special case: it returns
45486 1 to the target if the file descriptor is attached
45487 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45488 would require implementing @code{ioctl} and would be more complex than
45493 @unnumberedsubsubsec system
45494 @cindex system, file-i/o system call
45499 int system(const char *command);
45503 @samp{Fsystem,@var{commandptr}/@var{len}}
45505 @item Return value:
45506 If @var{len} is zero, the return value indicates whether a shell is
45507 available. A zero return value indicates a shell is not available.
45508 For non-zero @var{len}, the value returned is -1 on error and the
45509 return status of the command otherwise. Only the exit status of the
45510 command is returned, which is extracted from the host's @code{system}
45511 return value by calling @code{WEXITSTATUS(retval)}. In case
45512 @file{/bin/sh} could not be executed, 127 is returned.
45518 The call was interrupted by the user.
45523 @value{GDBN} takes over the full task of calling the necessary host calls
45524 to perform the @code{system} call. The return value of @code{system} on
45525 the host is simplified before it's returned
45526 to the target. Any termination signal information from the child process
45527 is discarded, and the return value consists
45528 entirely of the exit status of the called command.
45530 Due to security concerns, the @code{system} call is by default refused
45531 by @value{GDBN}. The user has to allow this call explicitly with the
45532 @code{set remote system-call-allowed 1} command.
45535 @item set remote system-call-allowed
45536 @kindex set remote system-call-allowed
45537 Control whether to allow the @code{system} calls in the File I/O
45538 protocol for the remote target. The default is zero (disabled).
45540 @item show remote system-call-allowed
45541 @kindex show remote system-call-allowed
45542 Show whether the @code{system} calls are allowed in the File I/O
45546 @node Protocol-specific Representation of Datatypes
45547 @subsection Protocol-specific Representation of Datatypes
45548 @cindex protocol-specific representation of datatypes, in file-i/o protocol
45551 * Integral Datatypes::
45553 * Memory Transfer::
45558 @node Integral Datatypes
45559 @unnumberedsubsubsec Integral Datatypes
45560 @cindex integral datatypes, in file-i/o protocol
45562 The integral datatypes used in the system calls are @code{int},
45563 @code{unsigned int}, @code{long}, @code{unsigned long},
45564 @code{mode_t}, and @code{time_t}.
45566 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
45567 implemented as 32 bit values in this protocol.
45569 @code{long} and @code{unsigned long} are implemented as 64 bit types.
45571 @xref{Limits}, for corresponding MIN and MAX values (similar to those
45572 in @file{limits.h}) to allow range checking on host and target.
45574 @code{time_t} datatypes are defined as seconds since the Epoch.
45576 All integral datatypes transferred as part of a memory read or write of a
45577 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
45580 @node Pointer Values
45581 @unnumberedsubsubsec Pointer Values
45582 @cindex pointer values, in file-i/o protocol
45584 Pointers to target data are transmitted as they are. An exception
45585 is made for pointers to buffers for which the length isn't
45586 transmitted as part of the function call, namely strings. Strings
45587 are transmitted as a pointer/length pair, both as hex values, e.g.@:
45594 which is a pointer to data of length 18 bytes at position 0x1aaf.
45595 The length is defined as the full string length in bytes, including
45596 the trailing null byte. For example, the string @code{"hello world"}
45597 at address 0x123456 is transmitted as
45603 @node Memory Transfer
45604 @unnumberedsubsubsec Memory Transfer
45605 @cindex memory transfer, in file-i/o protocol
45607 Structured data which is transferred using a memory read or write (for
45608 example, a @code{struct stat}) is expected to be in a protocol-specific format
45609 with all scalar multibyte datatypes being big endian. Translation to
45610 this representation needs to be done both by the target before the @code{F}
45611 packet is sent, and by @value{GDBN} before
45612 it transfers memory to the target. Transferred pointers to structured
45613 data should point to the already-coerced data at any time.
45617 @unnumberedsubsubsec struct stat
45618 @cindex struct stat, in file-i/o protocol
45620 The buffer of type @code{struct stat} used by the target and @value{GDBN}
45621 is defined as follows:
45625 unsigned int st_dev; /* device */
45626 unsigned int st_ino; /* inode */
45627 mode_t st_mode; /* protection */
45628 unsigned int st_nlink; /* number of hard links */
45629 unsigned int st_uid; /* user ID of owner */
45630 unsigned int st_gid; /* group ID of owner */
45631 unsigned int st_rdev; /* device type (if inode device) */
45632 unsigned long st_size; /* total size, in bytes */
45633 unsigned long st_blksize; /* blocksize for filesystem I/O */
45634 unsigned long st_blocks; /* number of blocks allocated */
45635 time_t st_atime; /* time of last access */
45636 time_t st_mtime; /* time of last modification */
45637 time_t st_ctime; /* time of last change */
45641 The integral datatypes conform to the definitions given in the
45642 appropriate section (see @ref{Integral Datatypes}, for details) so this
45643 structure is of size 64 bytes.
45645 The values of several fields have a restricted meaning and/or
45651 A value of 0 represents a file, 1 the console.
45654 No valid meaning for the target. Transmitted unchanged.
45657 Valid mode bits are described in @ref{Constants}. Any other
45658 bits have currently no meaning for the target.
45663 No valid meaning for the target. Transmitted unchanged.
45668 These values have a host and file system dependent
45669 accuracy. Especially on Windows hosts, the file system may not
45670 support exact timing values.
45673 The target gets a @code{struct stat} of the above representation and is
45674 responsible for coercing it to the target representation before
45677 Note that due to size differences between the host, target, and protocol
45678 representations of @code{struct stat} members, these members could eventually
45679 get truncated on the target.
45681 @node struct timeval
45682 @unnumberedsubsubsec struct timeval
45683 @cindex struct timeval, in file-i/o protocol
45685 The buffer of type @code{struct timeval} used by the File-I/O protocol
45686 is defined as follows:
45690 time_t tv_sec; /* second */
45691 long tv_usec; /* microsecond */
45695 The integral datatypes conform to the definitions given in the
45696 appropriate section (see @ref{Integral Datatypes}, for details) so this
45697 structure is of size 8 bytes.
45700 @subsection Constants
45701 @cindex constants, in file-i/o protocol
45703 The following values are used for the constants inside of the
45704 protocol. @value{GDBN} and target are responsible for translating these
45705 values before and after the call as needed.
45716 @unnumberedsubsubsec Open Flags
45717 @cindex open flags, in file-i/o protocol
45719 All values are given in hexadecimal representation.
45731 @node mode_t Values
45732 @unnumberedsubsubsec mode_t Values
45733 @cindex mode_t values, in file-i/o protocol
45735 All values are given in octal representation.
45752 @unnumberedsubsubsec Errno Values
45753 @cindex errno values, in file-i/o protocol
45755 All values are given in decimal representation.
45780 @code{EUNKNOWN} is used as a fallback error value if a host system returns
45781 any error value not in the list of supported error numbers.
45784 @unnumberedsubsubsec Lseek Flags
45785 @cindex lseek flags, in file-i/o protocol
45794 @unnumberedsubsubsec Limits
45795 @cindex limits, in file-i/o protocol
45797 All values are given in decimal representation.
45800 INT_MIN -2147483648
45802 UINT_MAX 4294967295
45803 LONG_MIN -9223372036854775808
45804 LONG_MAX 9223372036854775807
45805 ULONG_MAX 18446744073709551615
45808 @node File-I/O Examples
45809 @subsection File-I/O Examples
45810 @cindex file-i/o examples
45812 Example sequence of a write call, file descriptor 3, buffer is at target
45813 address 0x1234, 6 bytes should be written:
45816 <- @code{Fwrite,3,1234,6}
45817 @emph{request memory read from target}
45820 @emph{return "6 bytes written"}
45824 Example sequence of a read call, file descriptor 3, buffer is at target
45825 address 0x1234, 6 bytes should be read:
45828 <- @code{Fread,3,1234,6}
45829 @emph{request memory write to target}
45830 -> @code{X1234,6:XXXXXX}
45831 @emph{return "6 bytes read"}
45835 Example sequence of a read call, call fails on the host due to invalid
45836 file descriptor (@code{EBADF}):
45839 <- @code{Fread,3,1234,6}
45843 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
45847 <- @code{Fread,3,1234,6}
45852 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
45856 <- @code{Fread,3,1234,6}
45857 -> @code{X1234,6:XXXXXX}
45861 @node Library List Format
45862 @section Library List Format
45863 @cindex library list format, remote protocol
45865 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
45866 same process as your application to manage libraries. In this case,
45867 @value{GDBN} can use the loader's symbol table and normal memory
45868 operations to maintain a list of shared libraries. On other
45869 platforms, the operating system manages loaded libraries.
45870 @value{GDBN} can not retrieve the list of currently loaded libraries
45871 through memory operations, so it uses the @samp{qXfer:libraries:read}
45872 packet (@pxref{qXfer library list read}) instead. The remote stub
45873 queries the target's operating system and reports which libraries
45876 The @samp{qXfer:libraries:read} packet returns an XML document which
45877 lists loaded libraries and their offsets. Each library has an
45878 associated name and one or more segment or section base addresses,
45879 which report where the library was loaded in memory.
45881 For the common case of libraries that are fully linked binaries, the
45882 library should have a list of segments. If the target supports
45883 dynamic linking of a relocatable object file, its library XML element
45884 should instead include a list of allocated sections. The segment or
45885 section bases are start addresses, not relocation offsets; they do not
45886 depend on the library's link-time base addresses.
45888 @value{GDBN} must be linked with the Expat library to support XML
45889 library lists. @xref{Expat}.
45891 A simple memory map, with one loaded library relocated by a single
45892 offset, looks like this:
45896 <library name="/lib/libc.so.6">
45897 <segment address="0x10000000"/>
45902 Another simple memory map, with one loaded library with three
45903 allocated sections (.text, .data, .bss), looks like this:
45907 <library name="sharedlib.o">
45908 <section address="0x10000000"/>
45909 <section address="0x20000000"/>
45910 <section address="0x30000000"/>
45915 The format of a library list is described by this DTD:
45918 <!-- library-list: Root element with versioning -->
45919 <!ELEMENT library-list (library)*>
45920 <!ATTLIST library-list version CDATA #FIXED "1.0">
45921 <!ELEMENT library (segment*, section*)>
45922 <!ATTLIST library name CDATA #REQUIRED>
45923 <!ELEMENT segment EMPTY>
45924 <!ATTLIST segment address CDATA #REQUIRED>
45925 <!ELEMENT section EMPTY>
45926 <!ATTLIST section address CDATA #REQUIRED>
45929 In addition, segments and section descriptors cannot be mixed within a
45930 single library element, and you must supply at least one segment or
45931 section for each library.
45933 @node Library List Format for SVR4 Targets
45934 @section Library List Format for SVR4 Targets
45935 @cindex library list format, remote protocol
45937 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
45938 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
45939 shared libraries. Still a special library list provided by this packet is
45940 more efficient for the @value{GDBN} remote protocol.
45942 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
45943 loaded libraries and their SVR4 linker parameters. For each library on SVR4
45944 target, the following parameters are reported:
45948 @code{name}, the absolute file name from the @code{l_name} field of
45949 @code{struct link_map}.
45951 @code{lm} with address of @code{struct link_map} used for TLS
45952 (Thread Local Storage) access.
45954 @code{l_addr}, the displacement as read from the field @code{l_addr} of
45955 @code{struct link_map}. For prelinked libraries this is not an absolute
45956 memory address. It is a displacement of absolute memory address against
45957 address the file was prelinked to during the library load.
45959 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
45962 Additionally the single @code{main-lm} attribute specifies address of
45963 @code{struct link_map} used for the main executable. This parameter is used
45964 for TLS access and its presence is optional.
45966 @value{GDBN} must be linked with the Expat library to support XML
45967 SVR4 library lists. @xref{Expat}.
45969 A simple memory map, with two loaded libraries (which do not use prelink),
45973 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
45974 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
45976 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
45978 </library-list-svr>
45981 The format of an SVR4 library list is described by this DTD:
45984 <!-- library-list-svr4: Root element with versioning -->
45985 <!ELEMENT library-list-svr4 (library)*>
45986 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
45987 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
45988 <!ELEMENT library EMPTY>
45989 <!ATTLIST library name CDATA #REQUIRED>
45990 <!ATTLIST library lm CDATA #REQUIRED>
45991 <!ATTLIST library l_addr CDATA #REQUIRED>
45992 <!ATTLIST library l_ld CDATA #REQUIRED>
45995 @node Memory Map Format
45996 @section Memory Map Format
45997 @cindex memory map format
45999 To be able to write into flash memory, @value{GDBN} needs to obtain a
46000 memory map from the target. This section describes the format of the
46003 The memory map is obtained using the @samp{qXfer:memory-map:read}
46004 (@pxref{qXfer memory map read}) packet and is an XML document that
46005 lists memory regions.
46007 @value{GDBN} must be linked with the Expat library to support XML
46008 memory maps. @xref{Expat}.
46010 The top-level structure of the document is shown below:
46013 <?xml version="1.0"?>
46014 <!DOCTYPE memory-map
46015 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46016 "http://sourceware.org/gdb/gdb-memory-map.dtd">
46022 Each region can be either:
46027 A region of RAM starting at @var{addr} and extending for @var{length}
46031 <memory type="ram" start="@var{addr}" length="@var{length}"/>
46036 A region of read-only memory:
46039 <memory type="rom" start="@var{addr}" length="@var{length}"/>
46044 A region of flash memory, with erasure blocks @var{blocksize}
46048 <memory type="flash" start="@var{addr}" length="@var{length}">
46049 <property name="blocksize">@var{blocksize}</property>
46055 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
46056 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
46057 packets to write to addresses in such ranges.
46059 The formal DTD for memory map format is given below:
46062 <!-- ................................................... -->
46063 <!-- Memory Map XML DTD ................................ -->
46064 <!-- File: memory-map.dtd .............................. -->
46065 <!-- .................................... .............. -->
46066 <!-- memory-map.dtd -->
46067 <!-- memory-map: Root element with versioning -->
46068 <!ELEMENT memory-map (memory)*>
46069 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
46070 <!ELEMENT memory (property)*>
46071 <!-- memory: Specifies a memory region,
46072 and its type, or device. -->
46073 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
46074 start CDATA #REQUIRED
46075 length CDATA #REQUIRED>
46076 <!-- property: Generic attribute tag -->
46077 <!ELEMENT property (#PCDATA | property)*>
46078 <!ATTLIST property name (blocksize) #REQUIRED>
46081 @node Thread List Format
46082 @section Thread List Format
46083 @cindex thread list format
46085 To efficiently update the list of threads and their attributes,
46086 @value{GDBN} issues the @samp{qXfer:threads:read} packet
46087 (@pxref{qXfer threads read}) and obtains the XML document with
46088 the following structure:
46091 <?xml version="1.0"?>
46093 <thread id="id" core="0" name="name">
46094 ... description ...
46099 Each @samp{thread} element must have the @samp{id} attribute that
46100 identifies the thread (@pxref{thread-id syntax}). The
46101 @samp{core} attribute, if present, specifies which processor core
46102 the thread was last executing on. The @samp{name} attribute, if
46103 present, specifies the human-readable name of the thread. The content
46104 of the of @samp{thread} element is interpreted as human-readable
46105 auxiliary information. The @samp{handle} attribute, if present,
46106 is a hex encoded representation of the thread handle.
46109 @node Traceframe Info Format
46110 @section Traceframe Info Format
46111 @cindex traceframe info format
46113 To be able to know which objects in the inferior can be examined when
46114 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
46115 memory ranges, registers and trace state variables that have been
46116 collected in a traceframe.
46118 This list is obtained using the @samp{qXfer:traceframe-info:read}
46119 (@pxref{qXfer traceframe info read}) packet and is an XML document.
46121 @value{GDBN} must be linked with the Expat library to support XML
46122 traceframe info discovery. @xref{Expat}.
46124 The top-level structure of the document is shown below:
46127 <?xml version="1.0"?>
46128 <!DOCTYPE traceframe-info
46129 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46130 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
46136 Each traceframe block can be either:
46141 A region of collected memory starting at @var{addr} and extending for
46142 @var{length} bytes from there:
46145 <memory start="@var{addr}" length="@var{length}"/>
46149 A block indicating trace state variable numbered @var{number} has been
46153 <tvar id="@var{number}"/>
46158 The formal DTD for the traceframe info format is given below:
46161 <!ELEMENT traceframe-info (memory | tvar)* >
46162 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
46164 <!ELEMENT memory EMPTY>
46165 <!ATTLIST memory start CDATA #REQUIRED
46166 length CDATA #REQUIRED>
46168 <!ATTLIST tvar id CDATA #REQUIRED>
46171 @node Branch Trace Format
46172 @section Branch Trace Format
46173 @cindex branch trace format
46175 In order to display the branch trace of an inferior thread,
46176 @value{GDBN} needs to obtain the list of branches. This list is
46177 represented as list of sequential code blocks that are connected via
46178 branches. The code in each block has been executed sequentially.
46180 This list is obtained using the @samp{qXfer:btrace:read}
46181 (@pxref{qXfer btrace read}) packet and is an XML document.
46183 @value{GDBN} must be linked with the Expat library to support XML
46184 traceframe info discovery. @xref{Expat}.
46186 The top-level structure of the document is shown below:
46189 <?xml version="1.0"?>
46191 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
46192 "http://sourceware.org/gdb/gdb-btrace.dtd">
46201 A block of sequentially executed instructions starting at @var{begin}
46202 and ending at @var{end}:
46205 <block begin="@var{begin}" end="@var{end}"/>
46210 The formal DTD for the branch trace format is given below:
46213 <!ELEMENT btrace (block* | pt) >
46214 <!ATTLIST btrace version CDATA #FIXED "1.0">
46216 <!ELEMENT block EMPTY>
46217 <!ATTLIST block begin CDATA #REQUIRED
46218 end CDATA #REQUIRED>
46220 <!ELEMENT pt (pt-config?, raw?)>
46222 <!ELEMENT pt-config (cpu?)>
46224 <!ELEMENT cpu EMPTY>
46225 <!ATTLIST cpu vendor CDATA #REQUIRED
46226 family CDATA #REQUIRED
46227 model CDATA #REQUIRED
46228 stepping CDATA #REQUIRED>
46230 <!ELEMENT raw (#PCDATA)>
46233 @node Branch Trace Configuration Format
46234 @section Branch Trace Configuration Format
46235 @cindex branch trace configuration format
46237 For each inferior thread, @value{GDBN} can obtain the branch trace
46238 configuration using the @samp{qXfer:btrace-conf:read}
46239 (@pxref{qXfer btrace-conf read}) packet.
46241 The configuration describes the branch trace format and configuration
46242 settings for that format. The following information is described:
46246 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
46249 The size of the @acronym{BTS} ring buffer in bytes.
46252 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
46256 The size of the @acronym{Intel PT} ring buffer in bytes.
46260 @value{GDBN} must be linked with the Expat library to support XML
46261 branch trace configuration discovery. @xref{Expat}.
46263 The formal DTD for the branch trace configuration format is given below:
46266 <!ELEMENT btrace-conf (bts?, pt?)>
46267 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
46269 <!ELEMENT bts EMPTY>
46270 <!ATTLIST bts size CDATA #IMPLIED>
46272 <!ELEMENT pt EMPTY>
46273 <!ATTLIST pt size CDATA #IMPLIED>
46276 @include agentexpr.texi
46278 @node Target Descriptions
46279 @appendix Target Descriptions
46280 @cindex target descriptions
46282 One of the challenges of using @value{GDBN} to debug embedded systems
46283 is that there are so many minor variants of each processor
46284 architecture in use. It is common practice for vendors to start with
46285 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
46286 and then make changes to adapt it to a particular market niche. Some
46287 architectures have hundreds of variants, available from dozens of
46288 vendors. This leads to a number of problems:
46292 With so many different customized processors, it is difficult for
46293 the @value{GDBN} maintainers to keep up with the changes.
46295 Since individual variants may have short lifetimes or limited
46296 audiences, it may not be worthwhile to carry information about every
46297 variant in the @value{GDBN} source tree.
46299 When @value{GDBN} does support the architecture of the embedded system
46300 at hand, the task of finding the correct architecture name to give the
46301 @command{set architecture} command can be error-prone.
46304 To address these problems, the @value{GDBN} remote protocol allows a
46305 target system to not only identify itself to @value{GDBN}, but to
46306 actually describe its own features. This lets @value{GDBN} support
46307 processor variants it has never seen before --- to the extent that the
46308 descriptions are accurate, and that @value{GDBN} understands them.
46310 @value{GDBN} must be linked with the Expat library to support XML
46311 target descriptions. @xref{Expat}.
46314 * Retrieving Descriptions:: How descriptions are fetched from a target.
46315 * Target Description Format:: The contents of a target description.
46316 * Predefined Target Types:: Standard types available for target
46318 * Enum Target Types:: How to define enum target types.
46319 * Standard Target Features:: Features @value{GDBN} knows about.
46322 @node Retrieving Descriptions
46323 @section Retrieving Descriptions
46325 Target descriptions can be read from the target automatically, or
46326 specified by the user manually. The default behavior is to read the
46327 description from the target. @value{GDBN} retrieves it via the remote
46328 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
46329 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
46330 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
46331 XML document, of the form described in @ref{Target Description
46334 Alternatively, you can specify a file to read for the target description.
46335 If a file is set, the target will not be queried. The commands to
46336 specify a file are:
46339 @cindex set tdesc filename
46340 @item set tdesc filename @var{path}
46341 Read the target description from @var{path}.
46343 @cindex unset tdesc filename
46344 @item unset tdesc filename
46345 Do not read the XML target description from a file. @value{GDBN}
46346 will use the description supplied by the current target.
46348 @cindex show tdesc filename
46349 @item show tdesc filename
46350 Show the filename to read for a target description, if any.
46354 @node Target Description Format
46355 @section Target Description Format
46356 @cindex target descriptions, XML format
46358 A target description annex is an @uref{http://www.w3.org/XML/, XML}
46359 document which complies with the Document Type Definition provided in
46360 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
46361 means you can use generally available tools like @command{xmllint} to
46362 check that your feature descriptions are well-formed and valid.
46363 However, to help people unfamiliar with XML write descriptions for
46364 their targets, we also describe the grammar here.
46366 Target descriptions can identify the architecture of the remote target
46367 and (for some architectures) provide information about custom register
46368 sets. They can also identify the OS ABI of the remote target.
46369 @value{GDBN} can use this information to autoconfigure for your
46370 target, or to warn you if you connect to an unsupported target.
46372 Here is a simple target description:
46375 <target version="1.0">
46376 <architecture>i386:x86-64</architecture>
46381 This minimal description only says that the target uses
46382 the x86-64 architecture.
46384 A target description has the following overall form, with [ ] marking
46385 optional elements and @dots{} marking repeatable elements. The elements
46386 are explained further below.
46389 <?xml version="1.0"?>
46390 <!DOCTYPE target SYSTEM "gdb-target.dtd">
46391 <target version="1.0">
46392 @r{[}@var{architecture}@r{]}
46393 @r{[}@var{osabi}@r{]}
46394 @r{[}@var{compatible}@r{]}
46395 @r{[}@var{feature}@dots{}@r{]}
46400 The description is generally insensitive to whitespace and line
46401 breaks, under the usual common-sense rules. The XML version
46402 declaration and document type declaration can generally be omitted
46403 (@value{GDBN} does not require them), but specifying them may be
46404 useful for XML validation tools. The @samp{version} attribute for
46405 @samp{<target>} may also be omitted, but we recommend
46406 including it; if future versions of @value{GDBN} use an incompatible
46407 revision of @file{gdb-target.dtd}, they will detect and report
46408 the version mismatch.
46410 @subsection Inclusion
46411 @cindex target descriptions, inclusion
46414 @cindex <xi:include>
46417 It can sometimes be valuable to split a target description up into
46418 several different annexes, either for organizational purposes, or to
46419 share files between different possible target descriptions. You can
46420 divide a description into multiple files by replacing any element of
46421 the target description with an inclusion directive of the form:
46424 <xi:include href="@var{document}"/>
46428 When @value{GDBN} encounters an element of this form, it will retrieve
46429 the named XML @var{document}, and replace the inclusion directive with
46430 the contents of that document. If the current description was read
46431 using @samp{qXfer}, then so will be the included document;
46432 @var{document} will be interpreted as the name of an annex. If the
46433 current description was read from a file, @value{GDBN} will look for
46434 @var{document} as a file in the same directory where it found the
46435 original description.
46437 @subsection Architecture
46438 @cindex <architecture>
46440 An @samp{<architecture>} element has this form:
46443 <architecture>@var{arch}</architecture>
46446 @var{arch} is one of the architectures from the set accepted by
46447 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46450 @cindex @code{<osabi>}
46452 This optional field was introduced in @value{GDBN} version 7.0.
46453 Previous versions of @value{GDBN} ignore it.
46455 An @samp{<osabi>} element has this form:
46458 <osabi>@var{abi-name}</osabi>
46461 @var{abi-name} is an OS ABI name from the same selection accepted by
46462 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
46464 @subsection Compatible Architecture
46465 @cindex @code{<compatible>}
46467 This optional field was introduced in @value{GDBN} version 7.0.
46468 Previous versions of @value{GDBN} ignore it.
46470 A @samp{<compatible>} element has this form:
46473 <compatible>@var{arch}</compatible>
46476 @var{arch} is one of the architectures from the set accepted by
46477 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46479 A @samp{<compatible>} element is used to specify that the target
46480 is able to run binaries in some other than the main target architecture
46481 given by the @samp{<architecture>} element. For example, on the
46482 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46483 or @code{powerpc:common64}, but the system is able to run binaries
46484 in the @code{spu} architecture as well. The way to describe this
46485 capability with @samp{<compatible>} is as follows:
46488 <architecture>powerpc:common</architecture>
46489 <compatible>spu</compatible>
46492 @subsection Features
46495 Each @samp{<feature>} describes some logical portion of the target
46496 system. Features are currently used to describe available CPU
46497 registers and the types of their contents. A @samp{<feature>} element
46501 <feature name="@var{name}">
46502 @r{[}@var{type}@dots{}@r{]}
46508 Each feature's name should be unique within the description. The name
46509 of a feature does not matter unless @value{GDBN} has some special
46510 knowledge of the contents of that feature; if it does, the feature
46511 should have its standard name. @xref{Standard Target Features}.
46515 Any register's value is a collection of bits which @value{GDBN} must
46516 interpret. The default interpretation is a two's complement integer,
46517 but other types can be requested by name in the register description.
46518 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
46519 Target Types}), and the description can define additional composite
46522 Each type element must have an @samp{id} attribute, which gives
46523 a unique (within the containing @samp{<feature>}) name to the type.
46524 Types must be defined before they are used.
46527 Some targets offer vector registers, which can be treated as arrays
46528 of scalar elements. These types are written as @samp{<vector>} elements,
46529 specifying the array element type, @var{type}, and the number of elements,
46533 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
46537 If a register's value is usefully viewed in multiple ways, define it
46538 with a union type containing the useful representations. The
46539 @samp{<union>} element contains one or more @samp{<field>} elements,
46540 each of which has a @var{name} and a @var{type}:
46543 <union id="@var{id}">
46544 <field name="@var{name}" type="@var{type}"/>
46551 If a register's value is composed from several separate values, define
46552 it with either a structure type or a flags type.
46553 A flags type may only contain bitfields.
46554 A structure type may either contain only bitfields or contain no bitfields.
46555 If the value contains only bitfields, its total size in bytes must be
46558 Non-bitfield values have a @var{name} and @var{type}.
46561 <struct id="@var{id}">
46562 <field name="@var{name}" type="@var{type}"/>
46567 Both @var{name} and @var{type} values are required.
46568 No implicit padding is added.
46570 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
46573 <struct id="@var{id}" size="@var{size}">
46574 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46580 <flags id="@var{id}" size="@var{size}">
46581 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46586 The @var{name} value is required.
46587 Bitfield values may be named with the empty string, @samp{""},
46588 in which case the field is ``filler'' and its value is not printed.
46589 Not all bits need to be specified, so ``filler'' fields are optional.
46591 The @var{start} and @var{end} values are required, and @var{type}
46593 The field's @var{start} must be less than or equal to its @var{end},
46594 and zero represents the least significant bit.
46596 The default value of @var{type} is @code{bool} for single bit fields,
46597 and an unsigned integer otherwise.
46599 Which to choose? Structures or flags?
46601 Registers defined with @samp{flags} have these advantages over
46602 defining them with @samp{struct}:
46606 Arithmetic may be performed on them as if they were integers.
46608 They are printed in a more readable fashion.
46611 Registers defined with @samp{struct} have one advantage over
46612 defining them with @samp{flags}:
46616 One can fetch individual fields like in @samp{C}.
46619 (gdb) print $my_struct_reg.field3
46625 @subsection Registers
46628 Each register is represented as an element with this form:
46631 <reg name="@var{name}"
46632 bitsize="@var{size}"
46633 @r{[}regnum="@var{num}"@r{]}
46634 @r{[}save-restore="@var{save-restore}"@r{]}
46635 @r{[}type="@var{type}"@r{]}
46636 @r{[}group="@var{group}"@r{]}/>
46640 The components are as follows:
46645 The register's name; it must be unique within the target description.
46648 The register's size, in bits.
46651 The register's number. If omitted, a register's number is one greater
46652 than that of the previous register (either in the current feature or in
46653 a preceding feature); the first register in the target description
46654 defaults to zero. This register number is used to read or write
46655 the register; e.g.@: it is used in the remote @code{p} and @code{P}
46656 packets, and registers appear in the @code{g} and @code{G} packets
46657 in order of increasing register number.
46660 Whether the register should be preserved across inferior function
46661 calls; this must be either @code{yes} or @code{no}. The default is
46662 @code{yes}, which is appropriate for most registers except for
46663 some system control registers; this is not related to the target's
46667 The type of the register. It may be a predefined type, a type
46668 defined in the current feature, or one of the special types @code{int}
46669 and @code{float}. @code{int} is an integer type of the correct size
46670 for @var{bitsize}, and @code{float} is a floating point type (in the
46671 architecture's normal floating point format) of the correct size for
46672 @var{bitsize}. The default is @code{int}.
46675 The register group to which this register belongs. It can be one of the
46676 standard register groups @code{general}, @code{float}, @code{vector} or an
46677 arbitrary string. Group names should be limited to alphanumeric characters.
46678 If a group name is made up of multiple words the words may be separated by
46679 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
46680 @var{group} is specified, @value{GDBN} will not display the register in
46681 @code{info registers}.
46685 @node Predefined Target Types
46686 @section Predefined Target Types
46687 @cindex target descriptions, predefined types
46689 Type definitions in the self-description can build up composite types
46690 from basic building blocks, but can not define fundamental types. Instead,
46691 standard identifiers are provided by @value{GDBN} for the fundamental
46692 types. The currently supported types are:
46697 Boolean type, occupying a single bit.
46705 Signed integer types holding the specified number of bits.
46713 Unsigned integer types holding the specified number of bits.
46717 Pointers to unspecified code and data. The program counter and
46718 any dedicated return address register may be marked as code
46719 pointers; printing a code pointer converts it into a symbolic
46720 address. The stack pointer and any dedicated address registers
46721 may be marked as data pointers.
46724 Half precision IEEE floating point.
46727 Single precision IEEE floating point.
46730 Double precision IEEE floating point.
46733 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
46736 The 12-byte extended precision format used by ARM FPA registers.
46739 The 10-byte extended precision format used by x87 registers.
46742 32bit @sc{eflags} register used by x86.
46745 32bit @sc{mxcsr} register used by x86.
46749 @node Enum Target Types
46750 @section Enum Target Types
46751 @cindex target descriptions, enum types
46753 Enum target types are useful in @samp{struct} and @samp{flags}
46754 register descriptions. @xref{Target Description Format}.
46756 Enum types have a name, size and a list of name/value pairs.
46759 <enum id="@var{id}" size="@var{size}">
46760 <evalue name="@var{name}" value="@var{value}"/>
46765 Enums must be defined before they are used.
46768 <enum id="levels_type" size="4">
46769 <evalue name="low" value="0"/>
46770 <evalue name="high" value="1"/>
46772 <flags id="flags_type" size="4">
46773 <field name="X" start="0"/>
46774 <field name="LEVEL" start="1" end="1" type="levels_type"/>
46776 <reg name="flags" bitsize="32" type="flags_type"/>
46779 Given that description, a value of 3 for the @samp{flags} register
46780 would be printed as:
46783 (gdb) info register flags
46784 flags 0x3 [ X LEVEL=high ]
46787 @node Standard Target Features
46788 @section Standard Target Features
46789 @cindex target descriptions, standard features
46791 A target description must contain either no registers or all the
46792 target's registers. If the description contains no registers, then
46793 @value{GDBN} will assume a default register layout, selected based on
46794 the architecture. If the description contains any registers, the
46795 default layout will not be used; the standard registers must be
46796 described in the target description, in such a way that @value{GDBN}
46797 can recognize them.
46799 This is accomplished by giving specific names to feature elements
46800 which contain standard registers. @value{GDBN} will look for features
46801 with those names and verify that they contain the expected registers;
46802 if any known feature is missing required registers, or if any required
46803 feature is missing, @value{GDBN} will reject the target
46804 description. You can add additional registers to any of the
46805 standard features --- @value{GDBN} will display them just as if
46806 they were added to an unrecognized feature.
46808 This section lists the known features and their expected contents.
46809 Sample XML documents for these features are included in the
46810 @value{GDBN} source tree, in the directory @file{gdb/features}.
46812 Names recognized by @value{GDBN} should include the name of the
46813 company or organization which selected the name, and the overall
46814 architecture to which the feature applies; so e.g.@: the feature
46815 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
46817 The names of registers are not case sensitive for the purpose
46818 of recognizing standard features, but @value{GDBN} will only display
46819 registers using the capitalization used in the description.
46822 * AArch64 Features::
46826 * LoongArch Features::
46827 * MicroBlaze Features::
46831 * Nios II Features::
46832 * OpenRISC 1000 Features::
46833 * PowerPC Features::
46834 * RISC-V Features::
46836 * S/390 and System z Features::
46842 @node AArch64 Features
46843 @subsection AArch64 Features
46844 @cindex target descriptions, AArch64 features
46846 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
46847 targets. It should contain registers @samp{x0} through @samp{x30},
46848 @samp{sp}, @samp{pc}, and @samp{cpsr}.
46850 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
46851 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
46854 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
46855 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
46856 through @samp{p15}, @samp{ffr} and @samp{vg}.
46858 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
46859 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
46862 @subsection ARC Features
46863 @cindex target descriptions, ARC Features
46865 ARC processors are so configurable that even core registers and their numbers
46866 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
46867 registers, which are important to @value{GDBN}, are not ``core'' registers in
46868 ARC. Therefore, there are two features that their presence is mandatory:
46869 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
46871 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
46876 @samp{r0} through @samp{r25} for normal register file targets.
46878 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
46879 register file targets.
46881 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
46882 @samp{blink}, @samp{lp_count}, @samp{pcl}.
46885 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
46886 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
46887 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
46888 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
46889 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
46890 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
46891 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
46892 because of their inaccessibility during user space debugging sessions.
46894 Extension core registers @samp{r32} through @samp{r59} are optional and their
46895 existence depends on the configuration. When debugging GNU/Linux applications,
46896 i.e.@: user space debugging, these core registers are not available.
46898 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
46899 is the list of registers pertinent to this feature:
46903 mandatory: @samp{pc} and @samp{status32}.
46905 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
46909 @subsection ARM Features
46910 @cindex target descriptions, ARM features
46912 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
46914 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
46915 @samp{lr}, @samp{pc}, and @samp{cpsr}.
46917 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
46918 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
46919 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
46922 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
46923 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
46925 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
46926 must contain register @samp{vpr}.
46928 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
46929 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
46931 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
46932 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
46933 synthesize the @samp{q} pseudo registers from @samp{d} register
46936 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
46937 it should contain at least registers @samp{wR0} through @samp{wR15} and
46938 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
46939 @samp{wCSSF}, and @samp{wCASF} registers are optional.
46941 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
46942 should contain at least registers @samp{d0} through @samp{d15}. If
46943 they are present, @samp{d16} through @samp{d31} should also be included.
46944 @value{GDBN} will synthesize the single-precision registers from
46945 halves of the double-precision registers.
46947 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
46948 need to contain registers; it instructs @value{GDBN} to display the
46949 VFP double-precision registers as vectors and to synthesize the
46950 quad-precision registers from pairs of double-precision registers.
46951 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
46952 be present and include 32 double-precision registers.
46954 The @samp{org.gnu.gdb.arm.m-profile-pacbti} feature is optional, and
46955 acknowledges support for the ARMv8.1-m PACBTI extensions. @value{GDBN}
46956 will track return address signing states and will decorate backtraces using
46957 the [PAC] marker, similar to AArch64's PAC extension.
46958 @xref{AArch64 PAC}.
46960 @node i386 Features
46961 @subsection i386 Features
46962 @cindex target descriptions, i386 features
46964 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
46965 targets. It should describe the following registers:
46969 @samp{eax} through @samp{edi} plus @samp{eip} for i386
46971 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
46973 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
46974 @samp{fs}, @samp{gs}
46976 @samp{st0} through @samp{st7}
46978 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
46979 @samp{foseg}, @samp{fooff} and @samp{fop}
46982 The register sets may be different, depending on the target.
46984 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
46985 describe registers:
46989 @samp{xmm0} through @samp{xmm7} for i386
46991 @samp{xmm0} through @samp{xmm15} for amd64
46996 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
46997 @samp{org.gnu.gdb.i386.sse} feature. It should
46998 describe the upper 128 bits of @sc{ymm} registers:
47002 @samp{ymm0h} through @samp{ymm7h} for i386
47004 @samp{ymm0h} through @samp{ymm15h} for amd64
47007 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
47008 Memory Protection Extension (MPX). It should describe the following registers:
47012 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
47014 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
47017 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
47018 describe a single register, @samp{orig_eax}.
47020 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
47021 describe two system registers: @samp{fs_base} and @samp{gs_base}.
47023 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
47024 @samp{org.gnu.gdb.i386.avx} feature. It should
47025 describe additional @sc{xmm} registers:
47029 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
47032 It should describe the upper 128 bits of additional @sc{ymm} registers:
47036 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
47040 describe the upper 256 bits of @sc{zmm} registers:
47044 @samp{zmm0h} through @samp{zmm7h} for i386.
47046 @samp{zmm0h} through @samp{zmm15h} for amd64.
47050 describe the additional @sc{zmm} registers:
47054 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
47057 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
47058 describe a single register, @samp{pkru}. It is a 32-bit register
47059 valid for i386 and amd64.
47061 @node LoongArch Features
47062 @subsection LoongArch Features
47063 @cindex target descriptions, LoongArch Features
47065 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
47066 targets. It should contain the registers @samp{r0} through @samp{r31},
47067 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
47068 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
47070 @node MicroBlaze Features
47071 @subsection MicroBlaze Features
47072 @cindex target descriptions, MicroBlaze features
47074 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
47075 targets. It should contain registers @samp{r0} through @samp{r31},
47076 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
47077 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
47078 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
47080 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
47081 If present, it should contain registers @samp{rshr} and @samp{rslr}
47083 @node MIPS Features
47084 @subsection @acronym{MIPS} Features
47085 @cindex target descriptions, @acronym{MIPS} features
47087 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
47088 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
47089 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
47092 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
47093 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
47094 registers. They may be 32-bit or 64-bit depending on the target.
47096 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
47097 it may be optional in a future version of @value{GDBN}. It should
47098 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
47099 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
47101 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
47102 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
47103 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
47104 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
47106 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
47107 contain a single register, @samp{restart}, which is used by the
47108 Linux kernel to control restartable syscalls.
47110 @node M68K Features
47111 @subsection M68K Features
47112 @cindex target descriptions, M68K features
47115 @item @samp{org.gnu.gdb.m68k.core}
47116 @itemx @samp{org.gnu.gdb.coldfire.core}
47117 @itemx @samp{org.gnu.gdb.fido.core}
47118 One of those features must be always present.
47119 The feature that is present determines which flavor of m68k is
47120 used. The feature that is present should contain registers
47121 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
47122 @samp{sp}, @samp{ps} and @samp{pc}.
47124 @item @samp{org.gnu.gdb.coldfire.fp}
47125 This feature is optional. If present, it should contain registers
47126 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
47129 Note that, despite the fact that this feature's name says
47130 @samp{coldfire}, it is used to describe any floating point registers.
47131 The size of the registers must match the main m68k flavor; so, for
47132 example, if the primary feature is reported as @samp{coldfire}, then
47133 64-bit floating point registers are required.
47136 @node NDS32 Features
47137 @subsection NDS32 Features
47138 @cindex target descriptions, NDS32 features
47140 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
47141 targets. It should contain at least registers @samp{r0} through
47142 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
47145 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
47146 it should contain 64-bit double-precision floating-point registers
47147 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
47148 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
47150 @emph{Note:} The first sixteen 64-bit double-precision floating-point
47151 registers are overlapped with the thirty-two 32-bit single-precision
47152 floating-point registers. The 32-bit single-precision registers, if
47153 not being listed explicitly, will be synthesized from halves of the
47154 overlapping 64-bit double-precision registers. Listing 32-bit
47155 single-precision registers explicitly is deprecated, and the
47156 support to it could be totally removed some day.
47158 @node Nios II Features
47159 @subsection Nios II Features
47160 @cindex target descriptions, Nios II features
47162 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
47163 targets. It should contain the 32 core registers (@samp{zero},
47164 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
47165 @samp{pc}, and the 16 control registers (@samp{status} through
47168 @node OpenRISC 1000 Features
47169 @subsection Openrisc 1000 Features
47170 @cindex target descriptions, OpenRISC 1000 features
47172 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
47173 targets. It should contain the 32 general purpose registers (@samp{r0}
47174 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
47176 @node PowerPC Features
47177 @subsection PowerPC Features
47178 @cindex target descriptions, PowerPC features
47180 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
47181 targets. It should contain registers @samp{r0} through @samp{r31},
47182 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
47183 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
47185 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
47186 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
47188 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
47189 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
47190 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
47191 through @samp{v31} as aliases for the corresponding @samp{vrX}
47194 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
47195 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
47196 combine these registers with the floating point registers (@samp{f0}
47197 through @samp{f31}) and the altivec registers (@samp{vr0} through
47198 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
47199 @samp{vs63}, the set of vector-scalar registers for POWER7.
47200 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
47201 @samp{org.gnu.gdb.power.altivec}.
47203 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
47204 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
47205 @samp{spefscr}. SPE targets should provide 32-bit registers in
47206 @samp{org.gnu.gdb.power.core} and provide the upper halves in
47207 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
47208 these to present registers @samp{ev0} through @samp{ev31} to the
47211 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
47212 contain the 64-bit register @samp{ppr}.
47214 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
47215 contain the 64-bit register @samp{dscr}.
47217 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
47218 contain the 64-bit register @samp{tar}.
47220 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
47221 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
47224 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
47225 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
47226 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
47227 server PMU registers provided by @sc{gnu}/Linux.
47229 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
47230 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
47233 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
47234 contain the checkpointed general-purpose registers @samp{cr0} through
47235 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
47236 @samp{cctr}. These registers may all be either 32-bit or 64-bit
47237 depending on the target. It should also contain the checkpointed
47238 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
47241 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
47242 contain the checkpointed 64-bit floating-point registers @samp{cf0}
47243 through @samp{cf31}, as well as the checkpointed 64-bit register
47246 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
47247 should contain the checkpointed altivec registers @samp{cvr0} through
47248 @samp{cvr31}, all 128-bit wide. It should also contain the
47249 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
47252 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
47253 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
47254 will combine these registers with the checkpointed floating point
47255 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
47256 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
47257 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
47258 @samp{cvs63}. Therefore, this feature requires both
47259 @samp{org.gnu.gdb.power.htm.altivec} and
47260 @samp{org.gnu.gdb.power.htm.fpu}.
47262 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
47263 contain the 64-bit checkpointed register @samp{cppr}.
47265 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
47266 contain the 64-bit checkpointed register @samp{cdscr}.
47268 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
47269 contain the 64-bit checkpointed register @samp{ctar}.
47272 @node RISC-V Features
47273 @subsection RISC-V Features
47274 @cindex target descriptions, RISC-V Features
47276 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
47277 targets. It should contain the registers @samp{x0} through
47278 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
47279 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
47282 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
47283 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
47284 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
47285 architectural register names, or the ABI names can be used.
47287 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
47288 it should contain registers that are not backed by real registers on
47289 the target, but are instead virtual, where the register value is
47290 derived from other target state. In many ways these are like
47291 @value{GDBN}s pseudo-registers, except implemented by the target.
47292 Currently the only register expected in this set is the one byte
47293 @samp{priv} register that contains the target's privilege level in the
47294 least significant two bits.
47296 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
47297 should contain all of the target's standard CSRs. Standard CSRs are
47298 those defined in the RISC-V specification documents. There is some
47299 overlap between this feature and the fpu feature; the @samp{fflags},
47300 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
47301 expectation is that these registers will be in the fpu feature if the
47302 target has floating point hardware, but can be moved into the csr
47303 feature if the target has the floating point control registers, but no
47304 other floating point hardware.
47306 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
47307 it should contain registers @samp{v0} through @samp{v31}, all of which
47308 must be the same size. These requirements are based on the v0.10
47309 draft vector extension, as the vector extension is not yet final. In
47310 the event that the register set of the vector extension changes for
47311 the final specification, the requirements given here could change for
47312 future releases of @value{GDBN}.
47315 @subsection RX Features
47316 @cindex target descriptions, RX Features
47318 The @samp{org.gnu.gdb.rx.core} feature is required for RX
47319 targets. It should contain the registers @samp{r0} through
47320 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
47321 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
47323 @node S/390 and System z Features
47324 @subsection S/390 and System z Features
47325 @cindex target descriptions, S/390 features
47326 @cindex target descriptions, System z features
47328 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
47329 System z targets. It should contain the PSW and the 16 general
47330 registers. In particular, System z targets should provide the 64-bit
47331 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
47332 S/390 targets should provide the 32-bit versions of these registers.
47333 A System z target that runs in 31-bit addressing mode should provide
47334 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
47335 register's upper halves @samp{r0h} through @samp{r15h}, and their
47336 lower halves @samp{r0l} through @samp{r15l}.
47338 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
47339 contain the 64-bit registers @samp{f0} through @samp{f15}, and
47342 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
47343 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
47345 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
47346 contain the register @samp{orig_r2}, which is 64-bit wide on System z
47347 targets and 32-bit otherwise. In addition, the feature may contain
47348 the @samp{last_break} register, whose width depends on the addressing
47349 mode, as well as the @samp{system_call} register, which is always
47352 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
47353 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
47354 @samp{atia}, and @samp{tr0} through @samp{tr15}.
47356 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
47357 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
47358 combined by @value{GDBN} with the floating point registers @samp{f0}
47359 through @samp{f15} to present the 128-bit wide vector registers
47360 @samp{v0} through @samp{v15}. In addition, this feature should
47361 contain the 128-bit wide vector registers @samp{v16} through
47364 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
47365 the 64-bit wide guarded-storage-control registers @samp{gsd},
47366 @samp{gssm}, and @samp{gsepla}.
47368 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
47369 the 64-bit wide guarded-storage broadcast control registers
47370 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
47372 @node Sparc Features
47373 @subsection Sparc Features
47374 @cindex target descriptions, sparc32 features
47375 @cindex target descriptions, sparc64 features
47376 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
47377 targets. It should describe the following registers:
47381 @samp{g0} through @samp{g7}
47383 @samp{o0} through @samp{o7}
47385 @samp{l0} through @samp{l7}
47387 @samp{i0} through @samp{i7}
47390 They may be 32-bit or 64-bit depending on the target.
47392 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
47393 targets. It should describe the following registers:
47397 @samp{f0} through @samp{f31}
47399 @samp{f32} through @samp{f62} for sparc64
47402 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
47403 targets. It should describe the following registers:
47407 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
47408 @samp{fsr}, and @samp{csr} for sparc32
47410 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
47414 @node TIC6x Features
47415 @subsection TMS320C6x Features
47416 @cindex target descriptions, TIC6x features
47417 @cindex target descriptions, TMS320C6x features
47418 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
47419 targets. It should contain registers @samp{A0} through @samp{A15},
47420 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
47422 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
47423 contain registers @samp{A16} through @samp{A31} and @samp{B16}
47424 through @samp{B31}.
47426 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
47427 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
47429 @node Operating System Information
47430 @appendix Operating System Information
47431 @cindex operating system information
47433 Users of @value{GDBN} often wish to obtain information about the state of
47434 the operating system running on the target---for example the list of
47435 processes, or the list of open files. This section describes the
47436 mechanism that makes it possible. This mechanism is similar to the
47437 target features mechanism (@pxref{Target Descriptions}), but focuses
47438 on a different aspect of target.
47440 Operating system information is retrieved from the target via the
47441 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
47442 read}). The object name in the request should be @samp{osdata}, and
47443 the @var{annex} identifies the data to be fetched.
47450 @appendixsection Process list
47451 @cindex operating system information, process list
47453 When requesting the process list, the @var{annex} field in the
47454 @samp{qXfer} request should be @samp{processes}. The returned data is
47455 an XML document. The formal syntax of this document is defined in
47456 @file{gdb/features/osdata.dtd}.
47458 An example document is:
47461 <?xml version="1.0"?>
47462 <!DOCTYPE target SYSTEM "osdata.dtd">
47463 <osdata type="processes">
47465 <column name="pid">1</column>
47466 <column name="user">root</column>
47467 <column name="command">/sbin/init</column>
47468 <column name="cores">1,2,3</column>
47473 Each item should include a column whose name is @samp{pid}. The value
47474 of that column should identify the process on the target. The
47475 @samp{user} and @samp{command} columns are optional, and will be
47476 displayed by @value{GDBN}. The @samp{cores} column, if present,
47477 should contain a comma-separated list of cores that this process
47478 is running on. Target may provide additional columns,
47479 which @value{GDBN} currently ignores.
47481 @node Trace File Format
47482 @appendix Trace File Format
47483 @cindex trace file format
47485 The trace file comes in three parts: a header, a textual description
47486 section, and a trace frame section with binary data.
47488 The header has the form @code{\x7fTRACE0\n}. The first byte is
47489 @code{0x7f} so as to indicate that the file contains binary data,
47490 while the @code{0} is a version number that may have different values
47493 The description section consists of multiple lines of @sc{ascii} text
47494 separated by newline characters (@code{0xa}). The lines may include a
47495 variety of optional descriptive or context-setting information, such
47496 as tracepoint definitions or register set size. @value{GDBN} will
47497 ignore any line that it does not recognize. An empty line marks the end
47502 Specifies the size of a register block in bytes. This is equal to the
47503 size of a @code{g} packet payload in the remote protocol. @var{size}
47504 is an ascii decimal number. There should be only one such line in
47505 a single trace file.
47507 @item status @var{status}
47508 Trace status. @var{status} has the same format as a @code{qTStatus}
47509 remote packet reply. There should be only one such line in a single trace
47512 @item tp @var{payload}
47513 Tracepoint definition. The @var{payload} has the same format as
47514 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
47515 may take multiple lines of definition, corresponding to the multiple
47518 @item tsv @var{payload}
47519 Trace state variable definition. The @var{payload} has the same format as
47520 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
47521 may take multiple lines of definition, corresponding to the multiple
47524 @item tdesc @var{payload}
47525 Target description in XML format. The @var{payload} is a single line of
47526 the XML file. All such lines should be concatenated together to get
47527 the original XML file. This file is in the same format as @code{qXfer}
47528 @code{features} payload, and corresponds to the main @code{target.xml}
47529 file. Includes are not allowed.
47533 The trace frame section consists of a number of consecutive frames.
47534 Each frame begins with a two-byte tracepoint number, followed by a
47535 four-byte size giving the amount of data in the frame. The data in
47536 the frame consists of a number of blocks, each introduced by a
47537 character indicating its type (at least register, memory, and trace
47538 state variable). The data in this section is raw binary, not a
47539 hexadecimal or other encoding; its endianness matches the target's
47542 @c FIXME bi-arch may require endianness/arch info in description section
47545 @item R @var{bytes}
47546 Register block. The number and ordering of bytes matches that of a
47547 @code{g} packet in the remote protocol. Note that these are the
47548 actual bytes, in target order, not a hexadecimal encoding.
47550 @item M @var{address} @var{length} @var{bytes}...
47551 Memory block. This is a contiguous block of memory, at the 8-byte
47552 address @var{address}, with a 2-byte length @var{length}, followed by
47553 @var{length} bytes.
47555 @item V @var{number} @var{value}
47556 Trace state variable block. This records the 8-byte signed value
47557 @var{value} of trace state variable numbered @var{number}.
47561 Future enhancements of the trace file format may include additional types
47564 @node Index Section Format
47565 @appendix @code{.gdb_index} section format
47566 @cindex .gdb_index section format
47567 @cindex index section format
47569 This section documents the index section that is created by @code{save
47570 gdb-index} (@pxref{Index Files}). The index section is
47571 DWARF-specific; some knowledge of DWARF is assumed in this
47574 The mapped index file format is designed to be directly
47575 @code{mmap}able on any architecture. In most cases, a datum is
47576 represented using a little-endian 32-bit integer value, called an
47577 @code{offset_type}. Big endian machines must byte-swap the values
47578 before using them. Exceptions to this rule are noted. The data is
47579 laid out such that alignment is always respected.
47581 A mapped index consists of several areas, laid out in order.
47585 The file header. This is a sequence of values, of @code{offset_type}
47586 unless otherwise noted:
47590 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
47591 Version 4 uses a different hashing function from versions 5 and 6.
47592 Version 6 includes symbols for inlined functions, whereas versions 4
47593 and 5 do not. Version 7 adds attributes to the CU indices in the
47594 symbol table. Version 8 specifies that symbols from DWARF type units
47595 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
47596 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
47598 @value{GDBN} will only read version 4, 5, or 6 indices
47599 by specifying @code{set use-deprecated-index-sections on}.
47600 GDB has a workaround for potentially broken version 7 indices so it is
47601 currently not flagged as deprecated.
47604 The offset, from the start of the file, of the CU list.
47607 The offset, from the start of the file, of the types CU list. Note
47608 that this area can be empty, in which case this offset will be equal
47609 to the next offset.
47612 The offset, from the start of the file, of the address area.
47615 The offset, from the start of the file, of the symbol table.
47618 The offset, from the start of the file, of the constant pool.
47622 The CU list. This is a sequence of pairs of 64-bit little-endian
47623 values, sorted by the CU offset. The first element in each pair is
47624 the offset of a CU in the @code{.debug_info} section. The second
47625 element in each pair is the length of that CU. References to a CU
47626 elsewhere in the map are done using a CU index, which is just the
47627 0-based index into this table. Note that if there are type CUs, then
47628 conceptually CUs and type CUs form a single list for the purposes of
47632 The types CU list. This is a sequence of triplets of 64-bit
47633 little-endian values. In a triplet, the first value is the CU offset,
47634 the second value is the type offset in the CU, and the third value is
47635 the type signature. The types CU list is not sorted.
47638 The address area. The address area consists of a sequence of address
47639 entries. Each address entry has three elements:
47643 The low address. This is a 64-bit little-endian value.
47646 The high address. This is a 64-bit little-endian value. Like
47647 @code{DW_AT_high_pc}, the value is one byte beyond the end.
47650 The CU index. This is an @code{offset_type} value.
47654 The symbol table. This is an open-addressed hash table. The size of
47655 the hash table is always a power of 2.
47657 Each slot in the hash table consists of a pair of @code{offset_type}
47658 values. The first value is the offset of the symbol's name in the
47659 constant pool. The second value is the offset of the CU vector in the
47662 If both values are 0, then this slot in the hash table is empty. This
47663 is ok because while 0 is a valid constant pool index, it cannot be a
47664 valid index for both a string and a CU vector.
47666 The hash value for a table entry is computed by applying an
47667 iterative hash function to the symbol's name. Starting with an
47668 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
47669 the string is incorporated into the hash using the formula depending on the
47674 The formula is @code{r = r * 67 + c - 113}.
47676 @item Versions 5 to 7
47677 The formula is @code{r = r * 67 + tolower (c) - 113}.
47680 The terminating @samp{\0} is not incorporated into the hash.
47682 The step size used in the hash table is computed via
47683 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
47684 value, and @samp{size} is the size of the hash table. The step size
47685 is used to find the next candidate slot when handling a hash
47688 The names of C@t{++} symbols in the hash table are canonicalized. We
47689 don't currently have a simple description of the canonicalization
47690 algorithm; if you intend to create new index sections, you must read
47694 The constant pool. This is simply a bunch of bytes. It is organized
47695 so that alignment is correct: CU vectors are stored first, followed by
47698 A CU vector in the constant pool is a sequence of @code{offset_type}
47699 values. The first value is the number of CU indices in the vector.
47700 Each subsequent value is the index and symbol attributes of a CU in
47701 the CU list. This element in the hash table is used to indicate which
47702 CUs define the symbol and how the symbol is used.
47703 See below for the format of each CU index+attributes entry.
47705 A string in the constant pool is zero-terminated.
47708 Attributes were added to CU index values in @code{.gdb_index} version 7.
47709 If a symbol has multiple uses within a CU then there is one
47710 CU index+attributes value for each use.
47712 The format of each CU index+attributes entry is as follows
47718 This is the index of the CU in the CU list.
47720 These bits are reserved for future purposes and must be zero.
47722 The kind of the symbol in the CU.
47726 This value is reserved and should not be used.
47727 By reserving zero the full @code{offset_type} value is backwards compatible
47728 with previous versions of the index.
47730 The symbol is a type.
47732 The symbol is a variable or an enum value.
47734 The symbol is a function.
47736 Any other kind of symbol.
47738 These values are reserved.
47742 This bit is zero if the value is global and one if it is static.
47744 The determination of whether a symbol is global or static is complicated.
47745 The authorative reference is the file @file{dwarf2read.c} in
47746 @value{GDBN} sources.
47750 This pseudo-code describes the computation of a symbol's kind and
47751 global/static attributes in the index.
47754 is_external = get_attribute (die, DW_AT_external);
47755 language = get_attribute (cu_die, DW_AT_language);
47758 case DW_TAG_typedef:
47759 case DW_TAG_base_type:
47760 case DW_TAG_subrange_type:
47764 case DW_TAG_enumerator:
47766 is_static = language != CPLUS;
47768 case DW_TAG_subprogram:
47770 is_static = ! (is_external || language == ADA);
47772 case DW_TAG_constant:
47774 is_static = ! is_external;
47776 case DW_TAG_variable:
47778 is_static = ! is_external;
47780 case DW_TAG_namespace:
47784 case DW_TAG_class_type:
47785 case DW_TAG_interface_type:
47786 case DW_TAG_structure_type:
47787 case DW_TAG_union_type:
47788 case DW_TAG_enumeration_type:
47790 is_static = language != CPLUS;
47798 @appendix Download debugging resources with Debuginfod
47801 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
47804 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
47805 can query servers using the build IDs associated with missing debug info,
47806 executables and source files in order to download them on demand.
47808 For instructions on building @value{GDBN} with @file{libdebuginfod},
47809 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
47810 with @code{elfutils}, starting with version 0.178. See
47811 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
47812 regarding @code{debuginfod}.
47815 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
47818 @node Debuginfod Settings
47819 @section Debuginfod Settings
47821 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
47824 @kindex set debuginfod enabled
47825 @anchor{set debuginfod enabled}
47826 @item set debuginfod enabled
47827 @itemx set debuginfod enabled on
47828 @cindex enable debuginfod
47829 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
47830 info or source files.
47832 @item set debuginfod enabled off
47833 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
47834 debug info or source files. By default, @code{debuginfod enabled} is set to
47835 @code{off} for non-interactive sessions.
47837 @item set debuginfod enabled ask
47838 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
47839 attempting to perform the next query. By default, @code{debuginfod enabled}
47840 is set to @code{ask} for interactive sessions.
47842 @kindex show debuginfod enabled
47843 @item show debuginfod enabled
47844 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
47847 @kindex set debuginfod urls
47848 @cindex configure debuginfod URLs
47849 @item set debuginfod urls
47850 @itemx set debuginfod urls @var{urls}
47851 Set the space-separated list of URLs that @code{debuginfod} will attempt to
47852 query. Only @code{http://}, @code{https://} and @code{file://} protocols
47853 should be used. The default value of @code{debuginfod urls} is copied from
47854 the @var{DEBUGINFOD_URLS} environment variable.
47856 @kindex show debuginfod urls
47857 @item show debuginfod urls
47858 Display the list of URLs that @code{debuginfod} will attempt to query.
47860 @kindex set debuginfod verbose
47861 @cindex debuginfod verbosity
47862 @item set debuginfod verbose
47863 @itemx set debuginfod verbose @var{n}
47864 Enable or disable @code{debuginfod}-related output. Use a non-zero value
47865 to enable and @code{0} to disable. @code{debuginfod} output is shown by
47868 @kindex show debuginfod verbose
47869 @item show debuginfod verbose
47870 Show the current verbosity setting.
47875 @appendix Manual pages
47879 * gdb man:: The GNU Debugger man page
47880 * gdbserver man:: Remote Server for the GNU Debugger man page
47881 * gcore man:: Generate a core file of a running program
47882 * gdbinit man:: gdbinit scripts
47883 * gdb-add-index man:: Add index files to speed up GDB
47889 @c man title gdb The GNU Debugger
47891 @c man begin SYNOPSIS gdb
47892 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
47895 @c man begin DESCRIPTION gdb
47896 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
47897 going on ``inside'' another program while it executes -- or what another
47898 program was doing at the moment it crashed.
47900 @value{GDBN} can do four main kinds of things (plus other things in support of
47901 these) to help you catch bugs in the act:
47905 Start your program, specifying anything that might affect its behavior.
47908 Make your program stop on specified conditions.
47911 Examine what has happened, when your program has stopped.
47914 Change things in your program, so you can experiment with correcting the
47915 effects of one bug and go on to learn about another.
47918 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
47921 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
47922 commands from the terminal until you tell it to exit with the @value{GDBN}
47923 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
47924 by using the command @code{help}.
47926 You can run @code{gdb} with no arguments or options; but the most
47927 usual way to start @value{GDBN} is with one argument or two, specifying an
47928 executable program as the argument:
47934 You can also start with both an executable program and a core file specified:
47940 You can, instead, specify a process ID as a second argument or use option
47941 @code{-p}, if you want to debug a running process:
47949 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
47950 can omit the @var{program} filename.
47952 Here are some of the most frequently needed @value{GDBN} commands:
47954 @c pod2man highlights the right hand side of the @item lines.
47956 @item break [@var{file}:][@var{function}|@var{line}]
47957 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
47959 @item run [@var{arglist}]
47960 Start your program (with @var{arglist}, if specified).
47963 Backtrace: display the program stack.
47965 @item print @var{expr}
47966 Display the value of an expression.
47969 Continue running your program (after stopping, e.g.@: at a breakpoint).
47972 Execute next program line (after stopping); step @emph{over} any
47973 function calls in the line.
47975 @item edit [@var{file}:]@var{function}
47976 look at the program line where it is presently stopped.
47978 @item list [@var{file}:]@var{function}
47979 type the text of the program in the vicinity of where it is presently stopped.
47982 Execute next program line (after stopping); step @emph{into} any
47983 function calls in the line.
47985 @item help [@var{name}]
47986 Show information about @value{GDBN} command @var{name}, or general information
47987 about using @value{GDBN}.
47991 Exit from @value{GDBN}.
47995 For full details on @value{GDBN},
47996 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47997 by Richard M. Stallman and Roland H. Pesch. The same text is available online
47998 as the @code{gdb} entry in the @code{info} program.
48002 @c man begin OPTIONS gdb
48003 Any arguments other than options specify an executable
48004 file and core file (or process ID); that is, the first argument
48005 encountered with no
48006 associated option flag is equivalent to a @option{--se} option, and the second,
48007 if any, is equivalent to a @option{-c} option if it's the name of a file.
48009 both long and abbreviated forms; both are shown here. The long forms are also
48010 recognized if you truncate them, so long as enough of the option is
48011 present to be unambiguous.
48013 The abbreviated forms are shown here with @samp{-} and long forms are shown
48014 with @samp{--} to reflect how they are shown in @option{--help}. However,
48015 @value{GDBN} recognizes all of the following conventions for most options:
48018 @item --option=@var{value}
48019 @item --option @var{value}
48020 @item -option=@var{value}
48021 @item -option @var{value}
48022 @item --o=@var{value}
48023 @item --o @var{value}
48024 @item -o=@var{value}
48025 @item -o @var{value}
48028 All the options and command line arguments you give are processed
48029 in sequential order. The order makes a difference when the @option{-x}
48035 List all options, with brief explanations.
48037 @item --symbols=@var{file}
48038 @itemx -s @var{file}
48039 Read symbol table from @var{file}.
48042 Enable writing into executable and core files.
48044 @item --exec=@var{file}
48045 @itemx -e @var{file}
48046 Use @var{file} as the executable file to execute when
48047 appropriate, and for examining pure data in conjunction with a core
48050 @item --se=@var{file}
48051 Read symbol table from @var{file} and use it as the executable
48054 @item --core=@var{file}
48055 @itemx -c @var{file}
48056 Use @var{file} as a core dump to examine.
48058 @item --command=@var{file}
48059 @itemx -x @var{file}
48060 Execute @value{GDBN} commands from @var{file}.
48062 @item --eval-command=@var{command}
48063 @item -ex @var{command}
48064 Execute given @value{GDBN} @var{command}.
48066 @item --init-eval-command=@var{command}
48068 Execute @value{GDBN} @var{command} before loading the inferior.
48070 @item --directory=@var{directory}
48071 @itemx -d @var{directory}
48072 Add @var{directory} to the path to search for source files.
48075 Do not execute commands from @file{~/.config/gdb/gdbinit},
48076 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
48077 @file{~/.gdbearlyinit}
48081 Do not execute commands from any @file{.gdbinit} or
48082 @file{.gdbearlyinit} initialization files.
48087 ``Quiet''. Do not print the introductory and copyright messages. These
48088 messages are also suppressed in batch mode.
48091 Run in batch mode. Exit with status @code{0} after processing all the command
48092 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
48093 Exit with nonzero status if an error occurs in executing the @value{GDBN}
48094 commands in the command files.
48096 Batch mode may be useful for running @value{GDBN} as a filter, for example to
48097 download and run a program on another computer; in order to make this
48098 more useful, the message
48101 Program exited normally.
48105 (which is ordinarily issued whenever a program running under @value{GDBN} control
48106 terminates) is not issued when running in batch mode.
48108 @item --batch-silent
48109 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
48110 output is supressed (stderr is unaffected). This is much quieter than
48111 @option{--silent} and would be useless for an interactive session.
48113 This is particularly useful when using targets that give @samp{Loading section}
48114 messages, for example.
48116 Note that targets that give their output via @value{GDBN}, as opposed to writing
48117 directly to @code{stdout}, will also be made silent.
48119 @item --args @var{prog} [@var{arglist}]
48120 Change interpretation of command line so that arguments following this
48121 option are passed as arguments to the inferior. As an example, take
48122 the following command:
48129 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
48130 the other hand, using:
48133 gdb --args ./a.out -q
48137 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
48139 @item --pid=@var{pid}
48140 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
48143 Open the terminal user interface.
48146 Read all symbols from the given symfile on the first access.
48149 Do not read symbol files.
48151 @item --return-child-result
48152 @value{GDBN}'s exit code will be the same as the child's exit code.
48154 @item --configuration
48155 Print details about GDB configuration and then exit.
48158 Print version information and then exit.
48160 @item --cd=@var{directory}
48161 Run @value{GDBN} using @var{directory} as its working directory,
48162 instead of the current directory.
48164 @item --data-directory=@var{directory}
48166 Run @value{GDBN} using @var{directory} as its data directory. The data
48167 directory is where @value{GDBN} searches for its auxiliary files.
48171 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
48172 @value{GDBN} to output the full file name and line number in a standard,
48173 recognizable fashion each time a stack frame is displayed (which
48174 includes each time the program stops). This recognizable format looks
48175 like two @samp{\032} characters, followed by the file name, line number
48176 and character position separated by colons, and a newline. The
48177 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
48178 characters as a signal to display the source code for the frame.
48180 @item -b @var{baudrate}
48181 Set the line speed (baud rate or bits per second) of any serial
48182 interface used by @value{GDBN} for remote debugging.
48184 @item -l @var{timeout}
48185 Set timeout, in seconds, for remote debugging.
48187 @item --tty=@var{device}
48188 Run using @var{device} for your program's standard input and output.
48192 @c man begin SEEALSO gdb
48194 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48195 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48196 documentation are properly installed at your site, the command
48203 should give you access to the complete manual.
48205 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48206 Richard M. Stallman and Roland H. Pesch, July 1991.
48210 @node gdbserver man
48211 @heading gdbserver man
48213 @c man title gdbserver Remote Server for the GNU Debugger
48215 @c man begin SYNOPSIS gdbserver
48216 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48218 gdbserver --attach @var{comm} @var{pid}
48220 gdbserver --multi @var{comm}
48224 @c man begin DESCRIPTION gdbserver
48225 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
48226 than the one which is running the program being debugged.
48229 @subheading Usage (server (target) side)
48232 Usage (server (target) side):
48235 First, you need to have a copy of the program you want to debug put onto
48236 the target system. The program can be stripped to save space if needed, as
48237 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
48238 the @value{GDBN} running on the host system.
48240 To use the server, you log on to the target system, and run the @command{gdbserver}
48241 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
48242 your program, and (c) its arguments. The general syntax is:
48245 target> gdbserver @var{comm} @var{program} [@var{args} ...]
48248 For example, using a serial port, you might say:
48252 @c @file would wrap it as F</dev/com1>.
48253 target> gdbserver /dev/com1 emacs foo.txt
48256 target> gdbserver @file{/dev/com1} emacs foo.txt
48260 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
48261 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
48262 waits patiently for the host @value{GDBN} to communicate with it.
48264 To use a TCP connection, you could say:
48267 target> gdbserver host:2345 emacs foo.txt
48270 This says pretty much the same thing as the last example, except that we are
48271 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
48272 that we are expecting to see a TCP connection from @code{host} to local TCP port
48273 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
48274 want for the port number as long as it does not conflict with any existing TCP
48275 ports on the target system. This same port number must be used in the host
48276 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
48277 you chose a port number that conflicts with another service, @command{gdbserver} will
48278 print an error message and exit.
48280 @command{gdbserver} can also attach to running programs.
48281 This is accomplished via the @option{--attach} argument. The syntax is:
48284 target> gdbserver --attach @var{comm} @var{pid}
48287 @var{pid} is the process ID of a currently running process. It isn't
48288 necessary to point @command{gdbserver} at a binary for the running process.
48290 To start @code{gdbserver} without supplying an initial command to run
48291 or process ID to attach, use the @option{--multi} command line option.
48292 In such case you should connect using @kbd{target extended-remote} to start
48293 the program you want to debug.
48296 target> gdbserver --multi @var{comm}
48300 @subheading Usage (host side)
48306 You need an unstripped copy of the target program on your host system, since
48307 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
48308 would, with the target program as the first argument. (You may need to use the
48309 @option{--baud} option if the serial line is running at anything except 9600 baud.)
48310 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
48311 new command you need to know about is @code{target remote}
48312 (or @code{target extended-remote}). Its argument is either
48313 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
48314 descriptor. For example:
48318 @c @file would wrap it as F</dev/ttyb>.
48319 (gdb) target remote /dev/ttyb
48322 (gdb) target remote @file{/dev/ttyb}
48327 communicates with the server via serial line @file{/dev/ttyb}, and:
48330 (gdb) target remote the-target:2345
48334 communicates via a TCP connection to port 2345 on host `the-target', where
48335 you previously started up @command{gdbserver} with the same port number. Note that for
48336 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
48337 command, otherwise you may get an error that looks something like
48338 `Connection refused'.
48340 @command{gdbserver} can also debug multiple inferiors at once,
48343 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
48344 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
48347 @ref{Inferiors Connections and Programs}.
48349 In such case use the @code{extended-remote} @value{GDBN} command variant:
48352 (gdb) target extended-remote the-target:2345
48355 The @command{gdbserver} option @option{--multi} may or may not be used in such
48359 @c man begin OPTIONS gdbserver
48360 There are three different modes for invoking @command{gdbserver}:
48365 Debug a specific program specified by its program name:
48368 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48371 The @var{comm} parameter specifies how should the server communicate
48372 with @value{GDBN}; it is either a device name (to use a serial line),
48373 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
48374 stdin/stdout of @code{gdbserver}. Specify the name of the program to
48375 debug in @var{prog}. Any remaining arguments will be passed to the
48376 program verbatim. When the program exits, @value{GDBN} will close the
48377 connection, and @code{gdbserver} will exit.
48380 Debug a specific program by specifying the process ID of a running
48384 gdbserver --attach @var{comm} @var{pid}
48387 The @var{comm} parameter is as described above. Supply the process ID
48388 of a running program in @var{pid}; @value{GDBN} will do everything
48389 else. Like with the previous mode, when the process @var{pid} exits,
48390 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
48393 Multi-process mode -- debug more than one program/process:
48396 gdbserver --multi @var{comm}
48399 In this mode, @value{GDBN} can instruct @command{gdbserver} which
48400 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
48401 close the connection when a process being debugged exits, so you can
48402 debug several processes in the same session.
48405 In each of the modes you may specify these options:
48410 List all options, with brief explanations.
48413 This option causes @command{gdbserver} to print its version number and exit.
48416 @command{gdbserver} will attach to a running program. The syntax is:
48419 target> gdbserver --attach @var{comm} @var{pid}
48422 @var{pid} is the process ID of a currently running process. It isn't
48423 necessary to point @command{gdbserver} at a binary for the running process.
48426 To start @code{gdbserver} without supplying an initial command to run
48427 or process ID to attach, use this command line option.
48428 Then you can connect using @kbd{target extended-remote} and start
48429 the program you want to debug. The syntax is:
48432 target> gdbserver --multi @var{comm}
48436 Instruct @code{gdbserver} to display extra status information about the debugging
48438 This option is intended for @code{gdbserver} development and for bug reports to
48441 @item --remote-debug
48442 Instruct @code{gdbserver} to display remote protocol debug output.
48443 This option is intended for @code{gdbserver} development and for bug reports to
48446 @item --debug-file=@var{filename}
48447 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
48448 This option is intended for @code{gdbserver} development and for bug reports to
48451 @item --debug-format=option1@r{[},option2,...@r{]}
48452 Instruct @code{gdbserver} to include extra information in each line
48453 of debugging output.
48454 @xref{Other Command-Line Arguments for gdbserver}.
48457 Specify a wrapper to launch programs
48458 for debugging. The option should be followed by the name of the
48459 wrapper, then any command-line arguments to pass to the wrapper, then
48460 @kbd{--} indicating the end of the wrapper arguments.
48463 By default, @command{gdbserver} keeps the listening TCP port open, so that
48464 additional connections are possible. However, if you start @code{gdbserver}
48465 with the @option{--once} option, it will stop listening for any further
48466 connection attempts after connecting to the first @value{GDBN} session.
48468 @c --disable-packet is not documented for users.
48470 @c --disable-randomization and --no-disable-randomization are superseded by
48471 @c QDisableRandomization.
48476 @c man begin SEEALSO gdbserver
48478 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48479 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48480 documentation are properly installed at your site, the command
48486 should give you access to the complete manual.
48488 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48489 Richard M. Stallman and Roland H. Pesch, July 1991.
48496 @c man title gcore Generate a core file of a running program
48499 @c man begin SYNOPSIS gcore
48500 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48504 @c man begin DESCRIPTION gcore
48505 Generate core dumps of one or more running programs with process IDs
48506 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
48507 is equivalent to one produced by the kernel when the process crashes
48508 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
48509 limit). However, unlike after a crash, after @command{gcore} finishes
48510 its job the program remains running without any change.
48513 @c man begin OPTIONS gcore
48516 Dump all memory mappings. The actual effect of this option depends on
48517 the Operating System. On @sc{gnu}/Linux, it will disable
48518 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
48519 enable @code{dump-excluded-mappings} (@pxref{set
48520 dump-excluded-mappings}).
48522 @item -o @var{prefix}
48523 The optional argument @var{prefix} specifies the prefix to be used
48524 when composing the file names of the core dumps. The file name is
48525 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
48526 process ID of the running program being analyzed by @command{gcore}.
48527 If not specified, @var{prefix} defaults to @var{gcore}.
48531 @c man begin SEEALSO gcore
48533 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48534 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48535 documentation are properly installed at your site, the command
48542 should give you access to the complete manual.
48544 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48545 Richard M. Stallman and Roland H. Pesch, July 1991.
48552 @c man title gdbinit GDB initialization scripts
48555 @c man begin SYNOPSIS gdbinit
48556 @ifset SYSTEM_GDBINIT
48557 @value{SYSTEM_GDBINIT}
48560 @ifset SYSTEM_GDBINIT_DIR
48561 @value{SYSTEM_GDBINIT_DIR}/*
48564 ~/.config/gdb/gdbinit
48572 @c man begin DESCRIPTION gdbinit
48573 These files contain @value{GDBN} commands to automatically execute during
48574 @value{GDBN} startup. The lines of contents are canned sequences of commands,
48577 the @value{GDBN} manual in node @code{Sequences}
48578 -- shell command @code{info -f gdb -n Sequences}.
48584 Please read more in
48586 the @value{GDBN} manual in node @code{Startup}
48587 -- shell command @code{info -f gdb -n Startup}.
48594 @ifset SYSTEM_GDBINIT
48595 @item @value{SYSTEM_GDBINIT}
48597 @ifclear SYSTEM_GDBINIT
48598 @item (not enabled with @code{--with-system-gdbinit} during compilation)
48600 System-wide initialization file. It is executed unless user specified
48601 @value{GDBN} option @code{-nx} or @code{-n}.
48604 the @value{GDBN} manual in node @code{System-wide configuration}
48605 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48607 @ifset SYSTEM_GDBINIT_DIR
48608 @item @value{SYSTEM_GDBINIT_DIR}
48610 @ifclear SYSTEM_GDBINIT_DIR
48611 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
48613 System-wide initialization directory. All files in this directory are
48614 executed on startup unless user specified @value{GDBN} option @code{-nx} or
48615 @code{-n}, as long as they have a recognized file extension.
48618 the @value{GDBN} manual in node @code{System-wide configuration}
48619 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48622 @ref{System-wide configuration}.
48625 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
48626 User initialization file. It is executed unless user specified
48627 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
48629 @item @file{.gdbinit}
48630 Initialization file for current directory. It may need to be enabled with
48631 @value{GDBN} security command @code{set auto-load local-gdbinit}.
48634 the @value{GDBN} manual in node @code{Init File in the Current Directory}
48635 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
48638 @ref{Init File in the Current Directory}.
48643 @c man begin SEEALSO gdbinit
48645 gdb(1), @code{info -f gdb -n Startup}
48647 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48648 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48649 documentation are properly installed at your site, the command
48655 should give you access to the complete manual.
48657 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48658 Richard M. Stallman and Roland H. Pesch, July 1991.
48662 @node gdb-add-index man
48663 @heading gdb-add-index
48664 @pindex gdb-add-index
48665 @anchor{gdb-add-index}
48667 @c man title gdb-add-index Add index files to speed up GDB
48669 @c man begin SYNOPSIS gdb-add-index
48670 gdb-add-index @var{filename}
48673 @c man begin DESCRIPTION gdb-add-index
48674 When @value{GDBN} finds a symbol file, it scans the symbols in the
48675 file in order to construct an internal symbol table. This lets most
48676 @value{GDBN} operations work quickly--at the cost of a delay early on.
48677 For large programs, this delay can be quite lengthy, so @value{GDBN}
48678 provides a way to build an index, which speeds up startup.
48680 To determine whether a file contains such an index, use the command
48681 @kbd{readelf -S filename}: the index is stored in a section named
48682 @code{.gdb_index}. The index file can only be produced on systems
48683 which use ELF binaries and DWARF debug information (i.e., sections
48684 named @code{.debug_*}).
48686 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
48687 in the @env{PATH} environment variable. If you want to use different
48688 versions of these programs, you can specify them through the
48689 @env{GDB} and @env{OBJDUMP} environment variables.
48693 the @value{GDBN} manual in node @code{Index Files}
48694 -- shell command @kbd{info -f gdb -n "Index Files"}.
48701 @c man begin SEEALSO gdb-add-index
48703 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48704 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48705 documentation are properly installed at your site, the command
48711 should give you access to the complete manual.
48713 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48714 Richard M. Stallman and Roland H. Pesch, July 1991.
48720 @node GNU Free Documentation License
48721 @appendix GNU Free Documentation License
48724 @node Concept Index
48725 @unnumbered Concept Index
48729 @node Command and Variable Index
48730 @unnumbered Command, Variable, and Function Index
48735 % I think something like @@colophon should be in texinfo. In the
48737 \long\def\colophon{\hbox to0pt{}\vfill
48738 \centerline{The body of this manual is set in}
48739 \centerline{\fontname\tenrm,}
48740 \centerline{with headings in {\bf\fontname\tenbf}}
48741 \centerline{and examples in {\tt\fontname\tentt}.}
48742 \centerline{{\it\fontname\tenit\/},}
48743 \centerline{{\bf\fontname\tenbf}, and}
48744 \centerline{{\sl\fontname\tensl\/}}
48745 \centerline{are used for emphasis.}\vfill}
48747 % Blame: doc@@cygnus.com, 1991.