1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2019 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{} 1988-2019 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2019 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 @chapter A Sample @value{GDBN} Session
563 You can use this manual at your leisure to read all about @value{GDBN}.
564 However, a handful of commands are enough to get started using the
565 debugger. This chapter illustrates those commands.
568 In this sample session, we emphasize user input like this: @b{input},
569 to make it easier to pick out from the surrounding output.
572 @c FIXME: this example may not be appropriate for some configs, where
573 @c FIXME...primary interest is in remote use.
575 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
576 processor) exhibits the following bug: sometimes, when we change its
577 quote strings from the default, the commands used to capture one macro
578 definition within another stop working. In the following short @code{m4}
579 session, we define a macro @code{foo} which expands to @code{0000}; we
580 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
581 same thing. However, when we change the open quote string to
582 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
583 procedure fails to define a new synonym @code{baz}:
592 @b{define(bar,defn(`foo'))}
596 @b{changequote(<QUOTE>,<UNQUOTE>)}
598 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
601 m4: End of input: 0: fatal error: EOF in string
605 Let us use @value{GDBN} to try to see what is going on.
608 $ @b{@value{GDBP} m4}
609 @c FIXME: this falsifies the exact text played out, to permit smallbook
610 @c FIXME... format to come out better.
611 @value{GDBN} is free software and you are welcome to distribute copies
612 of it under certain conditions; type "show copying" to see
614 There is absolutely no warranty for @value{GDBN}; type "show warranty"
617 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
622 @value{GDBN} reads only enough symbol data to know where to find the
623 rest when needed; as a result, the first prompt comes up very quickly.
624 We now tell @value{GDBN} to use a narrower display width than usual, so
625 that examples fit in this manual.
628 (@value{GDBP}) @b{set width 70}
632 We need to see how the @code{m4} built-in @code{changequote} works.
633 Having looked at the source, we know the relevant subroutine is
634 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
635 @code{break} command.
638 (@value{GDBP}) @b{break m4_changequote}
639 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
643 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
644 control; as long as control does not reach the @code{m4_changequote}
645 subroutine, the program runs as usual:
648 (@value{GDBP}) @b{run}
649 Starting program: /work/Editorial/gdb/gnu/m4/m4
657 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
658 suspends execution of @code{m4}, displaying information about the
659 context where it stops.
662 @b{changequote(<QUOTE>,<UNQUOTE>)}
664 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
666 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
670 Now we use the command @code{n} (@code{next}) to advance execution to
671 the next line of the current function.
675 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
680 @code{set_quotes} looks like a promising subroutine. We can go into it
681 by using the command @code{s} (@code{step}) instead of @code{next}.
682 @code{step} goes to the next line to be executed in @emph{any}
683 subroutine, so it steps into @code{set_quotes}.
687 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
689 530 if (lquote != def_lquote)
693 The display that shows the subroutine where @code{m4} is now
694 suspended (and its arguments) is called a stack frame display. It
695 shows a summary of the stack. We can use the @code{backtrace}
696 command (which can also be spelled @code{bt}), to see where we are
697 in the stack as a whole: the @code{backtrace} command displays a
698 stack frame for each active subroutine.
701 (@value{GDBP}) @b{bt}
702 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
704 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
706 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
707 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
709 #4 0x79dc in expand_input () at macro.c:40
710 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
714 We step through a few more lines to see what happens. The first two
715 times, we can use @samp{s}; the next two times we use @code{n} to avoid
716 falling into the @code{xstrdup} subroutine.
720 0x3b5c 532 if (rquote != def_rquote)
722 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
723 def_lquote : xstrdup(lq);
725 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
728 538 len_lquote = strlen(rquote);
732 The last line displayed looks a little odd; we can examine the variables
733 @code{lquote} and @code{rquote} to see if they are in fact the new left
734 and right quotes we specified. We use the command @code{p}
735 (@code{print}) to see their values.
738 (@value{GDBP}) @b{p lquote}
739 $1 = 0x35d40 "<QUOTE>"
740 (@value{GDBP}) @b{p rquote}
741 $2 = 0x35d50 "<UNQUOTE>"
745 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
746 To look at some context, we can display ten lines of source
747 surrounding the current line with the @code{l} (@code{list}) command.
753 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
755 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
758 538 len_lquote = strlen(rquote);
759 539 len_rquote = strlen(lquote);
766 Let us step past the two lines that set @code{len_lquote} and
767 @code{len_rquote}, and then examine the values of those variables.
771 539 len_rquote = strlen(lquote);
774 (@value{GDBP}) @b{p len_lquote}
776 (@value{GDBP}) @b{p len_rquote}
781 That certainly looks wrong, assuming @code{len_lquote} and
782 @code{len_rquote} are meant to be the lengths of @code{lquote} and
783 @code{rquote} respectively. We can set them to better values using
784 the @code{p} command, since it can print the value of
785 any expression---and that expression can include subroutine calls and
789 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
791 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
796 Is that enough to fix the problem of using the new quotes with the
797 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
798 executing with the @code{c} (@code{continue}) command, and then try the
799 example that caused trouble initially:
805 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
812 Success! The new quotes now work just as well as the default ones. The
813 problem seems to have been just the two typos defining the wrong
814 lengths. We allow @code{m4} exit by giving it an EOF as input:
818 Program exited normally.
822 The message @samp{Program exited normally.} is from @value{GDBN}; it
823 indicates @code{m4} has finished executing. We can end our @value{GDBN}
824 session with the @value{GDBN} @code{quit} command.
827 (@value{GDBP}) @b{quit}
831 @chapter Getting In and Out of @value{GDBN}
833 This chapter discusses how to start @value{GDBN}, and how to get out of it.
837 type @samp{@value{GDBP}} to start @value{GDBN}.
839 type @kbd{quit} or @kbd{Ctrl-d} to exit.
843 * Invoking GDB:: How to start @value{GDBN}
844 * Quitting GDB:: How to quit @value{GDBN}
845 * Shell Commands:: How to use shell commands inside @value{GDBN}
846 * Logging Output:: How to log @value{GDBN}'s output to a file
850 @section Invoking @value{GDBN}
852 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
853 @value{GDBN} reads commands from the terminal until you tell it to exit.
855 You can also run @code{@value{GDBP}} with a variety of arguments and options,
856 to specify more of your debugging environment at the outset.
858 The command-line options described here are designed
859 to cover a variety of situations; in some environments, some of these
860 options may effectively be unavailable.
862 The most usual way to start @value{GDBN} is with one argument,
863 specifying an executable program:
866 @value{GDBP} @var{program}
870 You can also start with both an executable program and a core file
874 @value{GDBP} @var{program} @var{core}
877 You can, instead, specify a process ID as a second argument, if you want
878 to debug a running process:
881 @value{GDBP} @var{program} 1234
885 would attach @value{GDBN} to process @code{1234} (unless you also have a file
886 named @file{1234}; @value{GDBN} does check for a core file first).
888 Taking advantage of the second command-line argument requires a fairly
889 complete operating system; when you use @value{GDBN} as a remote
890 debugger attached to a bare board, there may not be any notion of
891 ``process'', and there is often no way to get a core dump. @value{GDBN}
892 will warn you if it is unable to attach or to read core dumps.
894 You can optionally have @code{@value{GDBP}} pass any arguments after the
895 executable file to the inferior using @code{--args}. This option stops
898 @value{GDBP} --args gcc -O2 -c foo.c
900 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
901 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
903 You can run @code{@value{GDBP}} without printing the front material, which describes
904 @value{GDBN}'s non-warranty, by specifying @code{--silent}
905 (or @code{-q}/@code{--quiet}):
908 @value{GDBP} --silent
912 You can further control how @value{GDBN} starts up by using command-line
913 options. @value{GDBN} itself can remind you of the options available.
923 to display all available options and briefly describe their use
924 (@samp{@value{GDBP} -h} is a shorter equivalent).
926 All options and command line arguments you give are processed
927 in sequential order. The order makes a difference when the
928 @samp{-x} option is used.
932 * File Options:: Choosing files
933 * Mode Options:: Choosing modes
934 * Startup:: What @value{GDBN} does during startup
938 @subsection Choosing Files
940 When @value{GDBN} starts, it reads any arguments other than options as
941 specifying an executable file and core file (or process ID). This is
942 the same as if the arguments were specified by the @samp{-se} and
943 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
944 first argument that does not have an associated option flag as
945 equivalent to the @samp{-se} option followed by that argument; and the
946 second argument that does not have an associated option flag, if any, as
947 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
948 If the second argument begins with a decimal digit, @value{GDBN} will
949 first attempt to attach to it as a process, and if that fails, attempt
950 to open it as a corefile. If you have a corefile whose name begins with
951 a digit, you can prevent @value{GDBN} from treating it as a pid by
952 prefixing it with @file{./}, e.g.@: @file{./12345}.
954 If @value{GDBN} has not been configured to included core file support,
955 such as for most embedded targets, then it will complain about a second
956 argument and ignore it.
958 Many options have both long and short forms; both are shown in the
959 following list. @value{GDBN} also recognizes the long forms if you truncate
960 them, so long as enough of the option is present to be unambiguous.
961 (If you prefer, you can flag option arguments with @samp{--} rather
962 than @samp{-}, though we illustrate the more usual convention.)
964 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
965 @c way, both those who look for -foo and --foo in the index, will find
969 @item -symbols @var{file}
971 @cindex @code{--symbols}
973 Read symbol table from file @var{file}.
975 @item -exec @var{file}
977 @cindex @code{--exec}
979 Use file @var{file} as the executable file to execute when appropriate,
980 and for examining pure data in conjunction with a core dump.
984 Read symbol table from file @var{file} and use it as the executable
987 @item -core @var{file}
989 @cindex @code{--core}
991 Use file @var{file} as a core dump to examine.
993 @item -pid @var{number}
994 @itemx -p @var{number}
997 Connect to process ID @var{number}, as with the @code{attach} command.
999 @item -command @var{file}
1000 @itemx -x @var{file}
1001 @cindex @code{--command}
1003 Execute commands from file @var{file}. The contents of this file is
1004 evaluated exactly as the @code{source} command would.
1005 @xref{Command Files,, Command files}.
1007 @item -eval-command @var{command}
1008 @itemx -ex @var{command}
1009 @cindex @code{--eval-command}
1011 Execute a single @value{GDBN} command.
1013 This option may be used multiple times to call multiple commands. It may
1014 also be interleaved with @samp{-command} as required.
1017 @value{GDBP} -ex 'target sim' -ex 'load' \
1018 -x setbreakpoints -ex 'run' a.out
1021 @item -init-command @var{file}
1022 @itemx -ix @var{file}
1023 @cindex @code{--init-command}
1025 Execute commands from file @var{file} before loading the inferior (but
1026 after loading gdbinit files).
1029 @item -init-eval-command @var{command}
1030 @itemx -iex @var{command}
1031 @cindex @code{--init-eval-command}
1033 Execute a single @value{GDBN} command before loading the inferior (but
1034 after loading gdbinit files).
1037 @item -directory @var{directory}
1038 @itemx -d @var{directory}
1039 @cindex @code{--directory}
1041 Add @var{directory} to the path to search for source and script files.
1045 @cindex @code{--readnow}
1047 Read each symbol file's entire symbol table immediately, rather than
1048 the default, which is to read it incrementally as it is needed.
1049 This makes startup slower, but makes future operations faster.
1052 @anchor{--readnever}
1053 @cindex @code{--readnever}, command-line option
1054 Do not read each symbol file's symbolic debug information. This makes
1055 startup faster but at the expense of not being able to perform
1056 symbolic debugging. DWARF unwind information is also not read,
1057 meaning backtraces may become incomplete or inaccurate. One use of
1058 this is when a user simply wants to do the following sequence: attach,
1059 dump core, detach. Loading the debugging information in this case is
1060 an unnecessary cause of delay.
1064 @subsection Choosing Modes
1066 You can run @value{GDBN} in various alternative modes---for example, in
1067 batch mode or quiet mode.
1075 Do not execute commands found in any initialization file.
1076 There are three init files, loaded in the following order:
1079 @item @file{system.gdbinit}
1080 This is the system-wide init file.
1081 Its location is specified with the @code{--with-system-gdbinit}
1082 configure option (@pxref{System-wide configuration}).
1083 It is loaded first when @value{GDBN} starts, before command line options
1084 have been processed.
1085 @item @file{~/.gdbinit}
1086 This is the init file in your home directory.
1087 It is loaded next, after @file{system.gdbinit}, and before
1088 command options have been processed.
1089 @item @file{./.gdbinit}
1090 This is the init file in the current directory.
1091 It is loaded last, after command line options other than @code{-x} and
1092 @code{-ex} have been processed. Command line options @code{-x} and
1093 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1096 For further documentation on startup processing, @xref{Startup}.
1097 For documentation on how to write command files,
1098 @xref{Command Files,,Command Files}.
1103 Do not execute commands found in @file{~/.gdbinit}, the init file
1104 in your home directory.
1110 @cindex @code{--quiet}
1111 @cindex @code{--silent}
1113 ``Quiet''. Do not print the introductory and copyright messages. These
1114 messages are also suppressed in batch mode.
1117 @cindex @code{--batch}
1118 Run in batch mode. Exit with status @code{0} after processing all the
1119 command files specified with @samp{-x} (and all commands from
1120 initialization files, if not inhibited with @samp{-n}). Exit with
1121 nonzero status if an error occurs in executing the @value{GDBN} commands
1122 in the command files. Batch mode also disables pagination, sets unlimited
1123 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1124 off} were in effect (@pxref{Messages/Warnings}).
1126 Batch mode may be useful for running @value{GDBN} as a filter, for
1127 example to download and run a program on another computer; in order to
1128 make this more useful, the message
1131 Program exited normally.
1135 (which is ordinarily issued whenever a program running under
1136 @value{GDBN} control terminates) is not issued when running in batch
1140 @cindex @code{--batch-silent}
1141 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1142 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1143 unaffected). This is much quieter than @samp{-silent} and would be useless
1144 for an interactive session.
1146 This is particularly useful when using targets that give @samp{Loading section}
1147 messages, for example.
1149 Note that targets that give their output via @value{GDBN}, as opposed to
1150 writing directly to @code{stdout}, will also be made silent.
1152 @item -return-child-result
1153 @cindex @code{--return-child-result}
1154 The return code from @value{GDBN} will be the return code from the child
1155 process (the process being debugged), with the following exceptions:
1159 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1160 internal error. In this case the exit code is the same as it would have been
1161 without @samp{-return-child-result}.
1163 The user quits with an explicit value. E.g., @samp{quit 1}.
1165 The child process never runs, or is not allowed to terminate, in which case
1166 the exit code will be -1.
1169 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1170 when @value{GDBN} is being used as a remote program loader or simulator
1175 @cindex @code{--nowindows}
1177 ``No windows''. If @value{GDBN} comes with a graphical user interface
1178 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1179 interface. If no GUI is available, this option has no effect.
1183 @cindex @code{--windows}
1185 If @value{GDBN} includes a GUI, then this option requires it to be
1188 @item -cd @var{directory}
1190 Run @value{GDBN} using @var{directory} as its working directory,
1191 instead of the current directory.
1193 @item -data-directory @var{directory}
1194 @itemx -D @var{directory}
1195 @cindex @code{--data-directory}
1197 Run @value{GDBN} using @var{directory} as its data directory.
1198 The data directory is where @value{GDBN} searches for its
1199 auxiliary files. @xref{Data Files}.
1203 @cindex @code{--fullname}
1205 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1206 subprocess. It tells @value{GDBN} to output the full file name and line
1207 number in a standard, recognizable fashion each time a stack frame is
1208 displayed (which includes each time your program stops). This
1209 recognizable format looks like two @samp{\032} characters, followed by
1210 the file name, line number and character position separated by colons,
1211 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1212 @samp{\032} characters as a signal to display the source code for the
1215 @item -annotate @var{level}
1216 @cindex @code{--annotate}
1217 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1218 effect is identical to using @samp{set annotate @var{level}}
1219 (@pxref{Annotations}). The annotation @var{level} controls how much
1220 information @value{GDBN} prints together with its prompt, values of
1221 expressions, source lines, and other types of output. Level 0 is the
1222 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1223 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1224 that control @value{GDBN}, and level 2 has been deprecated.
1226 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1230 @cindex @code{--args}
1231 Change interpretation of command line so that arguments following the
1232 executable file are passed as command line arguments to the inferior.
1233 This option stops option processing.
1235 @item -baud @var{bps}
1237 @cindex @code{--baud}
1239 Set the line speed (baud rate or bits per second) of any serial
1240 interface used by @value{GDBN} for remote debugging.
1242 @item -l @var{timeout}
1244 Set the timeout (in seconds) of any communication used by @value{GDBN}
1245 for remote debugging.
1247 @item -tty @var{device}
1248 @itemx -t @var{device}
1249 @cindex @code{--tty}
1251 Run using @var{device} for your program's standard input and output.
1252 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1254 @c resolve the situation of these eventually
1256 @cindex @code{--tui}
1257 Activate the @dfn{Text User Interface} when starting. The Text User
1258 Interface manages several text windows on the terminal, showing
1259 source, assembly, registers and @value{GDBN} command outputs
1260 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1261 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1262 Using @value{GDBN} under @sc{gnu} Emacs}).
1264 @item -interpreter @var{interp}
1265 @cindex @code{--interpreter}
1266 Use the interpreter @var{interp} for interface with the controlling
1267 program or device. This option is meant to be set by programs which
1268 communicate with @value{GDBN} using it as a back end.
1269 @xref{Interpreters, , Command Interpreters}.
1271 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1272 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1273 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1274 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1275 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1276 interfaces are no longer supported.
1279 @cindex @code{--write}
1280 Open the executable and core files for both reading and writing. This
1281 is equivalent to the @samp{set write on} command inside @value{GDBN}
1285 @cindex @code{--statistics}
1286 This option causes @value{GDBN} to print statistics about time and
1287 memory usage after it completes each command and returns to the prompt.
1290 @cindex @code{--version}
1291 This option causes @value{GDBN} to print its version number and
1292 no-warranty blurb, and exit.
1294 @item -configuration
1295 @cindex @code{--configuration}
1296 This option causes @value{GDBN} to print details about its build-time
1297 configuration parameters, and then exit. These details can be
1298 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1303 @subsection What @value{GDBN} Does During Startup
1304 @cindex @value{GDBN} startup
1306 Here's the description of what @value{GDBN} does during session startup:
1310 Sets up the command interpreter as specified by the command line
1311 (@pxref{Mode Options, interpreter}).
1315 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1316 used when building @value{GDBN}; @pxref{System-wide configuration,
1317 ,System-wide configuration and settings}) and executes all the commands in
1320 @anchor{Home Directory Init File}
1322 Reads the init file (if any) in your home directory@footnote{On
1323 DOS/Windows systems, the home directory is the one pointed to by the
1324 @code{HOME} environment variable.} and executes all the commands in
1327 @anchor{Option -init-eval-command}
1329 Executes commands and command files specified by the @samp{-iex} and
1330 @samp{-ix} options in their specified order. Usually you should use the
1331 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1332 settings before @value{GDBN} init files get executed and before inferior
1336 Processes command line options and operands.
1338 @anchor{Init File in the Current Directory during Startup}
1340 Reads and executes the commands from init file (if any) in the current
1341 working directory as long as @samp{set auto-load local-gdbinit} is set to
1342 @samp{on} (@pxref{Init File in the Current Directory}).
1343 This is only done if the current directory is
1344 different from your home directory. Thus, you can have more than one
1345 init file, one generic in your home directory, and another, specific
1346 to the program you are debugging, in the directory where you invoke
1350 If the command line specified a program to debug, or a process to
1351 attach to, or a core file, @value{GDBN} loads any auto-loaded
1352 scripts provided for the program or for its loaded shared libraries.
1353 @xref{Auto-loading}.
1355 If you wish to disable the auto-loading during startup,
1356 you must do something like the following:
1359 $ gdb -iex "set auto-load python-scripts off" myprogram
1362 Option @samp{-ex} does not work because the auto-loading is then turned
1366 Executes commands and command files specified by the @samp{-ex} and
1367 @samp{-x} options in their specified order. @xref{Command Files}, for
1368 more details about @value{GDBN} command files.
1371 Reads the command history recorded in the @dfn{history file}.
1372 @xref{Command History}, for more details about the command history and the
1373 files where @value{GDBN} records it.
1376 Init files use the same syntax as @dfn{command files} (@pxref{Command
1377 Files}) and are processed by @value{GDBN} in the same way. The init
1378 file in your home directory can set options (such as @samp{set
1379 complaints}) that affect subsequent processing of command line options
1380 and operands. Init files are not executed if you use the @samp{-nx}
1381 option (@pxref{Mode Options, ,Choosing Modes}).
1383 To display the list of init files loaded by gdb at startup, you
1384 can use @kbd{gdb --help}.
1386 @cindex init file name
1387 @cindex @file{.gdbinit}
1388 @cindex @file{gdb.ini}
1389 The @value{GDBN} init files are normally called @file{.gdbinit}.
1390 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1391 the limitations of file names imposed by DOS filesystems. The Windows
1392 port of @value{GDBN} uses the standard name, but if it finds a
1393 @file{gdb.ini} file in your home directory, it warns you about that
1394 and suggests to rename the file to the standard name.
1398 @section Quitting @value{GDBN}
1399 @cindex exiting @value{GDBN}
1400 @cindex leaving @value{GDBN}
1403 @kindex quit @r{[}@var{expression}@r{]}
1404 @kindex q @r{(@code{quit})}
1405 @item quit @r{[}@var{expression}@r{]}
1407 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1408 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1409 do not supply @var{expression}, @value{GDBN} will terminate normally;
1410 otherwise it will terminate using the result of @var{expression} as the
1415 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1416 terminates the action of any @value{GDBN} command that is in progress and
1417 returns to @value{GDBN} command level. It is safe to type the interrupt
1418 character at any time because @value{GDBN} does not allow it to take effect
1419 until a time when it is safe.
1421 If you have been using @value{GDBN} to control an attached process or
1422 device, you can release it with the @code{detach} command
1423 (@pxref{Attach, ,Debugging an Already-running Process}).
1425 @node Shell Commands
1426 @section Shell Commands
1428 If you need to execute occasional shell commands during your
1429 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1430 just use the @code{shell} command.
1435 @cindex shell escape
1436 @item shell @var{command-string}
1437 @itemx !@var{command-string}
1438 Invoke a standard shell to execute @var{command-string}.
1439 Note that no space is needed between @code{!} and @var{command-string}.
1440 If it exists, the environment variable @code{SHELL} determines which
1441 shell to run. Otherwise @value{GDBN} uses the default shell
1442 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1445 The utility @code{make} is often needed in development environments.
1446 You do not have to use the @code{shell} command for this purpose in
1451 @cindex calling make
1452 @item make @var{make-args}
1453 Execute the @code{make} program with the specified
1454 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1457 @node Logging Output
1458 @section Logging Output
1459 @cindex logging @value{GDBN} output
1460 @cindex save @value{GDBN} output to a file
1462 You may want to save the output of @value{GDBN} commands to a file.
1463 There are several commands to control @value{GDBN}'s logging.
1467 @item set logging on
1469 @item set logging off
1471 @cindex logging file name
1472 @item set logging file @var{file}
1473 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1474 @item set logging overwrite [on|off]
1475 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1476 you want @code{set logging on} to overwrite the logfile instead.
1477 @item set logging redirect [on|off]
1478 By default, @value{GDBN} output will go to both the terminal and the logfile.
1479 Set @code{redirect} if you want output to go only to the log file.
1480 @kindex show logging
1482 Show the current values of the logging settings.
1486 @chapter @value{GDBN} Commands
1488 You can abbreviate a @value{GDBN} command to the first few letters of the command
1489 name, if that abbreviation is unambiguous; and you can repeat certain
1490 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1491 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1492 show you the alternatives available, if there is more than one possibility).
1495 * Command Syntax:: How to give commands to @value{GDBN}
1496 * Completion:: Command completion
1497 * Help:: How to ask @value{GDBN} for help
1500 @node Command Syntax
1501 @section Command Syntax
1503 A @value{GDBN} command is a single line of input. There is no limit on
1504 how long it can be. It starts with a command name, which is followed by
1505 arguments whose meaning depends on the command name. For example, the
1506 command @code{step} accepts an argument which is the number of times to
1507 step, as in @samp{step 5}. You can also use the @code{step} command
1508 with no arguments. Some commands do not allow any arguments.
1510 @cindex abbreviation
1511 @value{GDBN} command names may always be truncated if that abbreviation is
1512 unambiguous. Other possible command abbreviations are listed in the
1513 documentation for individual commands. In some cases, even ambiguous
1514 abbreviations are allowed; for example, @code{s} is specially defined as
1515 equivalent to @code{step} even though there are other commands whose
1516 names start with @code{s}. You can test abbreviations by using them as
1517 arguments to the @code{help} command.
1519 @cindex repeating commands
1520 @kindex RET @r{(repeat last command)}
1521 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1522 repeat the previous command. Certain commands (for example, @code{run})
1523 will not repeat this way; these are commands whose unintentional
1524 repetition might cause trouble and which you are unlikely to want to
1525 repeat. User-defined commands can disable this feature; see
1526 @ref{Define, dont-repeat}.
1528 The @code{list} and @code{x} commands, when you repeat them with
1529 @key{RET}, construct new arguments rather than repeating
1530 exactly as typed. This permits easy scanning of source or memory.
1532 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1533 output, in a way similar to the common utility @code{more}
1534 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1535 @key{RET} too many in this situation, @value{GDBN} disables command
1536 repetition after any command that generates this sort of display.
1538 @kindex # @r{(a comment)}
1540 Any text from a @kbd{#} to the end of the line is a comment; it does
1541 nothing. This is useful mainly in command files (@pxref{Command
1542 Files,,Command Files}).
1544 @cindex repeating command sequences
1545 @kindex Ctrl-o @r{(operate-and-get-next)}
1546 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1547 commands. This command accepts the current line, like @key{RET}, and
1548 then fetches the next line relative to the current line from the history
1552 @section Command Completion
1555 @cindex word completion
1556 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1557 only one possibility; it can also show you what the valid possibilities
1558 are for the next word in a command, at any time. This works for @value{GDBN}
1559 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1561 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1562 of a word. If there is only one possibility, @value{GDBN} fills in the
1563 word, and waits for you to finish the command (or press @key{RET} to
1564 enter it). For example, if you type
1566 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1567 @c complete accuracy in these examples; space introduced for clarity.
1568 @c If texinfo enhancements make it unnecessary, it would be nice to
1569 @c replace " @key" by "@key" in the following...
1571 (@value{GDBP}) info bre @key{TAB}
1575 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1576 the only @code{info} subcommand beginning with @samp{bre}:
1579 (@value{GDBP}) info breakpoints
1583 You can either press @key{RET} at this point, to run the @code{info
1584 breakpoints} command, or backspace and enter something else, if
1585 @samp{breakpoints} does not look like the command you expected. (If you
1586 were sure you wanted @code{info breakpoints} in the first place, you
1587 might as well just type @key{RET} immediately after @samp{info bre},
1588 to exploit command abbreviations rather than command completion).
1590 If there is more than one possibility for the next word when you press
1591 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1592 characters and try again, or just press @key{TAB} a second time;
1593 @value{GDBN} displays all the possible completions for that word. For
1594 example, you might want to set a breakpoint on a subroutine whose name
1595 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1596 just sounds the bell. Typing @key{TAB} again displays all the
1597 function names in your program that begin with those characters, for
1601 (@value{GDBP}) b make_ @key{TAB}
1602 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1603 make_a_section_from_file make_environ
1604 make_abs_section make_function_type
1605 make_blockvector make_pointer_type
1606 make_cleanup make_reference_type
1607 make_command make_symbol_completion_list
1608 (@value{GDBP}) b make_
1612 After displaying the available possibilities, @value{GDBN} copies your
1613 partial input (@samp{b make_} in the example) so you can finish the
1616 If you just want to see the list of alternatives in the first place, you
1617 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1618 means @kbd{@key{META} ?}. You can type this either by holding down a
1619 key designated as the @key{META} shift on your keyboard (if there is
1620 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1622 If the number of possible completions is large, @value{GDBN} will
1623 print as much of the list as it has collected, as well as a message
1624 indicating that the list may be truncated.
1627 (@value{GDBP}) b m@key{TAB}@key{TAB}
1629 <... the rest of the possible completions ...>
1630 *** List may be truncated, max-completions reached. ***
1635 This behavior can be controlled with the following commands:
1638 @kindex set max-completions
1639 @item set max-completions @var{limit}
1640 @itemx set max-completions unlimited
1641 Set the maximum number of completion candidates. @value{GDBN} will
1642 stop looking for more completions once it collects this many candidates.
1643 This is useful when completing on things like function names as collecting
1644 all the possible candidates can be time consuming.
1645 The default value is 200. A value of zero disables tab-completion.
1646 Note that setting either no limit or a very large limit can make
1648 @kindex show max-completions
1649 @item show max-completions
1650 Show the maximum number of candidates that @value{GDBN} will collect and show
1654 @cindex quotes in commands
1655 @cindex completion of quoted strings
1656 Sometimes the string you need, while logically a ``word'', may contain
1657 parentheses or other characters that @value{GDBN} normally excludes from
1658 its notion of a word. To permit word completion to work in this
1659 situation, you may enclose words in @code{'} (single quote marks) in
1660 @value{GDBN} commands.
1662 A likely situation where you might need this is in typing an
1663 expression that involves a C@t{++} symbol name with template
1664 parameters. This is because when completing expressions, GDB treats
1665 the @samp{<} character as word delimiter, assuming that it's the
1666 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1669 For example, when you want to call a C@t{++} template function
1670 interactively using the @code{print} or @code{call} commands, you may
1671 need to distinguish whether you mean the version of @code{name} that
1672 was specialized for @code{int}, @code{name<int>()}, or the version
1673 that was specialized for @code{float}, @code{name<float>()}. To use
1674 the word-completion facilities in this situation, type a single quote
1675 @code{'} at the beginning of the function name. This alerts
1676 @value{GDBN} that it may need to consider more information than usual
1677 when you press @key{TAB} or @kbd{M-?} to request word completion:
1680 (@value{GDBP}) p 'func< @kbd{M-?}
1681 func<int>() func<float>()
1682 (@value{GDBP}) p 'func<
1685 When setting breakpoints however (@pxref{Specify Location}), you don't
1686 usually need to type a quote before the function name, because
1687 @value{GDBN} understands that you want to set a breakpoint on a
1691 (@value{GDBP}) b func< @kbd{M-?}
1692 func<int>() func<float>()
1693 (@value{GDBP}) b func<
1696 This is true even in the case of typing the name of C@t{++} overloaded
1697 functions (multiple definitions of the same function, distinguished by
1698 argument type). For example, when you want to set a breakpoint you
1699 don't need to distinguish whether you mean the version of @code{name}
1700 that takes an @code{int} parameter, @code{name(int)}, or the version
1701 that takes a @code{float} parameter, @code{name(float)}.
1704 (@value{GDBP}) b bubble( @kbd{M-?}
1705 bubble(int) bubble(double)
1706 (@value{GDBP}) b bubble(dou @kbd{M-?}
1710 See @ref{quoting names} for a description of other scenarios that
1713 For more information about overloaded functions, see @ref{C Plus Plus
1714 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1715 overload-resolution off} to disable overload resolution;
1716 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1718 @cindex completion of structure field names
1719 @cindex structure field name completion
1720 @cindex completion of union field names
1721 @cindex union field name completion
1722 When completing in an expression which looks up a field in a
1723 structure, @value{GDBN} also tries@footnote{The completer can be
1724 confused by certain kinds of invalid expressions. Also, it only
1725 examines the static type of the expression, not the dynamic type.} to
1726 limit completions to the field names available in the type of the
1730 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1731 magic to_fputs to_rewind
1732 to_data to_isatty to_write
1733 to_delete to_put to_write_async_safe
1738 This is because the @code{gdb_stdout} is a variable of the type
1739 @code{struct ui_file} that is defined in @value{GDBN} sources as
1746 ui_file_flush_ftype *to_flush;
1747 ui_file_write_ftype *to_write;
1748 ui_file_write_async_safe_ftype *to_write_async_safe;
1749 ui_file_fputs_ftype *to_fputs;
1750 ui_file_read_ftype *to_read;
1751 ui_file_delete_ftype *to_delete;
1752 ui_file_isatty_ftype *to_isatty;
1753 ui_file_rewind_ftype *to_rewind;
1754 ui_file_put_ftype *to_put;
1761 @section Getting Help
1762 @cindex online documentation
1765 You can always ask @value{GDBN} itself for information on its commands,
1766 using the command @code{help}.
1769 @kindex h @r{(@code{help})}
1772 You can use @code{help} (abbreviated @code{h}) with no arguments to
1773 display a short list of named classes of commands:
1777 List of classes of commands:
1779 aliases -- Aliases of other commands
1780 breakpoints -- Making program stop at certain points
1781 data -- Examining data
1782 files -- Specifying and examining files
1783 internals -- Maintenance commands
1784 obscure -- Obscure features
1785 running -- Running the program
1786 stack -- Examining the stack
1787 status -- Status inquiries
1788 support -- Support facilities
1789 tracepoints -- Tracing of program execution without
1790 stopping the program
1791 user-defined -- User-defined commands
1793 Type "help" followed by a class name for a list of
1794 commands in that class.
1795 Type "help" followed by command name for full
1797 Command name abbreviations are allowed if unambiguous.
1800 @c the above line break eliminates huge line overfull...
1802 @item help @var{class}
1803 Using one of the general help classes as an argument, you can get a
1804 list of the individual commands in that class. For example, here is the
1805 help display for the class @code{status}:
1808 (@value{GDBP}) help status
1813 @c Line break in "show" line falsifies real output, but needed
1814 @c to fit in smallbook page size.
1815 info -- Generic command for showing things
1816 about the program being debugged
1817 show -- Generic command for showing things
1820 Type "help" followed by command name for full
1822 Command name abbreviations are allowed if unambiguous.
1826 @item help @var{command}
1827 With a command name as @code{help} argument, @value{GDBN} displays a
1828 short paragraph on how to use that command.
1831 @item apropos @var{args}
1832 The @code{apropos} command searches through all of the @value{GDBN}
1833 commands, and their documentation, for the regular expression specified in
1834 @var{args}. It prints out all matches found. For example:
1845 alias -- Define a new command that is an alias of an existing command
1846 aliases -- Aliases of other commands
1847 d -- Delete some breakpoints or auto-display expressions
1848 del -- Delete some breakpoints or auto-display expressions
1849 delete -- Delete some breakpoints or auto-display expressions
1854 @item complete @var{args}
1855 The @code{complete @var{args}} command lists all the possible completions
1856 for the beginning of a command. Use @var{args} to specify the beginning of the
1857 command you want completed. For example:
1863 @noindent results in:
1874 @noindent This is intended for use by @sc{gnu} Emacs.
1877 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1878 and @code{show} to inquire about the state of your program, or the state
1879 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1880 manual introduces each of them in the appropriate context. The listings
1881 under @code{info} and under @code{show} in the Command, Variable, and
1882 Function Index point to all the sub-commands. @xref{Command and Variable
1888 @kindex i @r{(@code{info})}
1890 This command (abbreviated @code{i}) is for describing the state of your
1891 program. For example, you can show the arguments passed to a function
1892 with @code{info args}, list the registers currently in use with @code{info
1893 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1894 You can get a complete list of the @code{info} sub-commands with
1895 @w{@code{help info}}.
1899 You can assign the result of an expression to an environment variable with
1900 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1901 @code{set prompt $}.
1905 In contrast to @code{info}, @code{show} is for describing the state of
1906 @value{GDBN} itself.
1907 You can change most of the things you can @code{show}, by using the
1908 related command @code{set}; for example, you can control what number
1909 system is used for displays with @code{set radix}, or simply inquire
1910 which is currently in use with @code{show radix}.
1913 To display all the settable parameters and their current
1914 values, you can use @code{show} with no arguments; you may also use
1915 @code{info set}. Both commands produce the same display.
1916 @c FIXME: "info set" violates the rule that "info" is for state of
1917 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1918 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1922 Here are several miscellaneous @code{show} subcommands, all of which are
1923 exceptional in lacking corresponding @code{set} commands:
1926 @kindex show version
1927 @cindex @value{GDBN} version number
1929 Show what version of @value{GDBN} is running. You should include this
1930 information in @value{GDBN} bug-reports. If multiple versions of
1931 @value{GDBN} are in use at your site, you may need to determine which
1932 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1933 commands are introduced, and old ones may wither away. Also, many
1934 system vendors ship variant versions of @value{GDBN}, and there are
1935 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1936 The version number is the same as the one announced when you start
1939 @kindex show copying
1940 @kindex info copying
1941 @cindex display @value{GDBN} copyright
1944 Display information about permission for copying @value{GDBN}.
1946 @kindex show warranty
1947 @kindex info warranty
1949 @itemx info warranty
1950 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1951 if your version of @value{GDBN} comes with one.
1953 @kindex show configuration
1954 @item show configuration
1955 Display detailed information about the way @value{GDBN} was configured
1956 when it was built. This displays the optional arguments passed to the
1957 @file{configure} script and also configuration parameters detected
1958 automatically by @command{configure}. When reporting a @value{GDBN}
1959 bug (@pxref{GDB Bugs}), it is important to include this information in
1965 @chapter Running Programs Under @value{GDBN}
1967 When you run a program under @value{GDBN}, you must first generate
1968 debugging information when you compile it.
1970 You may start @value{GDBN} with its arguments, if any, in an environment
1971 of your choice. If you are doing native debugging, you may redirect
1972 your program's input and output, debug an already running process, or
1973 kill a child process.
1976 * Compilation:: Compiling for debugging
1977 * Starting:: Starting your program
1978 * Arguments:: Your program's arguments
1979 * Environment:: Your program's environment
1981 * Working Directory:: Your program's working directory
1982 * Input/Output:: Your program's input and output
1983 * Attach:: Debugging an already-running process
1984 * Kill Process:: Killing the child process
1986 * Inferiors and Programs:: Debugging multiple inferiors and programs
1987 * Threads:: Debugging programs with multiple threads
1988 * Forks:: Debugging forks
1989 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1993 @section Compiling for Debugging
1995 In order to debug a program effectively, you need to generate
1996 debugging information when you compile it. This debugging information
1997 is stored in the object file; it describes the data type of each
1998 variable or function and the correspondence between source line numbers
1999 and addresses in the executable code.
2001 To request debugging information, specify the @samp{-g} option when you run
2004 Programs that are to be shipped to your customers are compiled with
2005 optimizations, using the @samp{-O} compiler option. However, some
2006 compilers are unable to handle the @samp{-g} and @samp{-O} options
2007 together. Using those compilers, you cannot generate optimized
2008 executables containing debugging information.
2010 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2011 without @samp{-O}, making it possible to debug optimized code. We
2012 recommend that you @emph{always} use @samp{-g} whenever you compile a
2013 program. You may think your program is correct, but there is no sense
2014 in pushing your luck. For more information, see @ref{Optimized Code}.
2016 Older versions of the @sc{gnu} C compiler permitted a variant option
2017 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2018 format; if your @sc{gnu} C compiler has this option, do not use it.
2020 @value{GDBN} knows about preprocessor macros and can show you their
2021 expansion (@pxref{Macros}). Most compilers do not include information
2022 about preprocessor macros in the debugging information if you specify
2023 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2024 the @sc{gnu} C compiler, provides macro information if you are using
2025 the DWARF debugging format, and specify the option @option{-g3}.
2027 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2028 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2029 information on @value{NGCC} options affecting debug information.
2031 You will have the best debugging experience if you use the latest
2032 version of the DWARF debugging format that your compiler supports.
2033 DWARF is currently the most expressive and best supported debugging
2034 format in @value{GDBN}.
2038 @section Starting your Program
2044 @kindex r @r{(@code{run})}
2047 Use the @code{run} command to start your program under @value{GDBN}.
2048 You must first specify the program name with an argument to
2049 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2050 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2051 command (@pxref{Files, ,Commands to Specify Files}).
2055 If you are running your program in an execution environment that
2056 supports processes, @code{run} creates an inferior process and makes
2057 that process run your program. In some environments without processes,
2058 @code{run} jumps to the start of your program. Other targets,
2059 like @samp{remote}, are always running. If you get an error
2060 message like this one:
2063 The "remote" target does not support "run".
2064 Try "help target" or "continue".
2068 then use @code{continue} to run your program. You may need @code{load}
2069 first (@pxref{load}).
2071 The execution of a program is affected by certain information it
2072 receives from its superior. @value{GDBN} provides ways to specify this
2073 information, which you must do @emph{before} starting your program. (You
2074 can change it after starting your program, but such changes only affect
2075 your program the next time you start it.) This information may be
2076 divided into four categories:
2079 @item The @emph{arguments.}
2080 Specify the arguments to give your program as the arguments of the
2081 @code{run} command. If a shell is available on your target, the shell
2082 is used to pass the arguments, so that you may use normal conventions
2083 (such as wildcard expansion or variable substitution) in describing
2085 In Unix systems, you can control which shell is used with the
2086 @code{SHELL} environment variable. If you do not define @code{SHELL},
2087 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2088 use of any shell with the @code{set startup-with-shell} command (see
2091 @item The @emph{environment.}
2092 Your program normally inherits its environment from @value{GDBN}, but you can
2093 use the @value{GDBN} commands @code{set environment} and @code{unset
2094 environment} to change parts of the environment that affect
2095 your program. @xref{Environment, ,Your Program's Environment}.
2097 @item The @emph{working directory.}
2098 You can set your program's working directory with the command
2099 @kbd{set cwd}. If you do not set any working directory with this
2100 command, your program will inherit @value{GDBN}'s working directory if
2101 native debugging, or the remote server's working directory if remote
2102 debugging. @xref{Working Directory, ,Your Program's Working
2105 @item The @emph{standard input and output.}
2106 Your program normally uses the same device for standard input and
2107 standard output as @value{GDBN} is using. You can redirect input and output
2108 in the @code{run} command line, or you can use the @code{tty} command to
2109 set a different device for your program.
2110 @xref{Input/Output, ,Your Program's Input and Output}.
2113 @emph{Warning:} While input and output redirection work, you cannot use
2114 pipes to pass the output of the program you are debugging to another
2115 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2119 When you issue the @code{run} command, your program begins to execute
2120 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2121 of how to arrange for your program to stop. Once your program has
2122 stopped, you may call functions in your program, using the @code{print}
2123 or @code{call} commands. @xref{Data, ,Examining Data}.
2125 If the modification time of your symbol file has changed since the last
2126 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2127 table, and reads it again. When it does this, @value{GDBN} tries to retain
2128 your current breakpoints.
2133 @cindex run to main procedure
2134 The name of the main procedure can vary from language to language.
2135 With C or C@t{++}, the main procedure name is always @code{main}, but
2136 other languages such as Ada do not require a specific name for their
2137 main procedure. The debugger provides a convenient way to start the
2138 execution of the program and to stop at the beginning of the main
2139 procedure, depending on the language used.
2141 The @samp{start} command does the equivalent of setting a temporary
2142 breakpoint at the beginning of the main procedure and then invoking
2143 the @samp{run} command.
2145 @cindex elaboration phase
2146 Some programs contain an @dfn{elaboration} phase where some startup code is
2147 executed before the main procedure is called. This depends on the
2148 languages used to write your program. In C@t{++}, for instance,
2149 constructors for static and global objects are executed before
2150 @code{main} is called. It is therefore possible that the debugger stops
2151 before reaching the main procedure. However, the temporary breakpoint
2152 will remain to halt execution.
2154 Specify the arguments to give to your program as arguments to the
2155 @samp{start} command. These arguments will be given verbatim to the
2156 underlying @samp{run} command. Note that the same arguments will be
2157 reused if no argument is provided during subsequent calls to
2158 @samp{start} or @samp{run}.
2160 It is sometimes necessary to debug the program during elaboration. In
2161 these cases, using the @code{start} command would stop the execution
2162 of your program too late, as the program would have already completed
2163 the elaboration phase. Under these circumstances, either insert
2164 breakpoints in your elaboration code before running your program or
2165 use the @code{starti} command.
2169 @cindex run to first instruction
2170 The @samp{starti} command does the equivalent of setting a temporary
2171 breakpoint at the first instruction of a program's execution and then
2172 invoking the @samp{run} command. For programs containing an
2173 elaboration phase, the @code{starti} command will stop execution at
2174 the start of the elaboration phase.
2176 @anchor{set exec-wrapper}
2177 @kindex set exec-wrapper
2178 @item set exec-wrapper @var{wrapper}
2179 @itemx show exec-wrapper
2180 @itemx unset exec-wrapper
2181 When @samp{exec-wrapper} is set, the specified wrapper is used to
2182 launch programs for debugging. @value{GDBN} starts your program
2183 with a shell command of the form @kbd{exec @var{wrapper}
2184 @var{program}}. Quoting is added to @var{program} and its
2185 arguments, but not to @var{wrapper}, so you should add quotes if
2186 appropriate for your shell. The wrapper runs until it executes
2187 your program, and then @value{GDBN} takes control.
2189 You can use any program that eventually calls @code{execve} with
2190 its arguments as a wrapper. Several standard Unix utilities do
2191 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2192 with @code{exec "$@@"} will also work.
2194 For example, you can use @code{env} to pass an environment variable to
2195 the debugged program, without setting the variable in your shell's
2199 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2203 This command is available when debugging locally on most targets, excluding
2204 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2206 @kindex set startup-with-shell
2207 @anchor{set startup-with-shell}
2208 @item set startup-with-shell
2209 @itemx set startup-with-shell on
2210 @itemx set startup-with-shell off
2211 @itemx show startup-with-shell
2212 On Unix systems, by default, if a shell is available on your target,
2213 @value{GDBN}) uses it to start your program. Arguments of the
2214 @code{run} command are passed to the shell, which does variable
2215 substitution, expands wildcard characters and performs redirection of
2216 I/O. In some circumstances, it may be useful to disable such use of a
2217 shell, for example, when debugging the shell itself or diagnosing
2218 startup failures such as:
2222 Starting program: ./a.out
2223 During startup program terminated with signal SIGSEGV, Segmentation fault.
2227 which indicates the shell or the wrapper specified with
2228 @samp{exec-wrapper} crashed, not your program. Most often, this is
2229 caused by something odd in your shell's non-interactive mode
2230 initialization file---such as @file{.cshrc} for C-shell,
2231 $@file{.zshenv} for the Z shell, or the file specified in the
2232 @samp{BASH_ENV} environment variable for BASH.
2234 @anchor{set auto-connect-native-target}
2235 @kindex set auto-connect-native-target
2236 @item set auto-connect-native-target
2237 @itemx set auto-connect-native-target on
2238 @itemx set auto-connect-native-target off
2239 @itemx show auto-connect-native-target
2241 By default, if not connected to any target yet (e.g., with
2242 @code{target remote}), the @code{run} command starts your program as a
2243 native process under @value{GDBN}, on your local machine. If you're
2244 sure you don't want to debug programs on your local machine, you can
2245 tell @value{GDBN} to not connect to the native target automatically
2246 with the @code{set auto-connect-native-target off} command.
2248 If @code{on}, which is the default, and if @value{GDBN} is not
2249 connected to a target already, the @code{run} command automaticaly
2250 connects to the native target, if one is available.
2252 If @code{off}, and if @value{GDBN} is not connected to a target
2253 already, the @code{run} command fails with an error:
2257 Don't know how to run. Try "help target".
2260 If @value{GDBN} is already connected to a target, @value{GDBN} always
2261 uses it with the @code{run} command.
2263 In any case, you can explicitly connect to the native target with the
2264 @code{target native} command. For example,
2267 (@value{GDBP}) set auto-connect-native-target off
2269 Don't know how to run. Try "help target".
2270 (@value{GDBP}) target native
2272 Starting program: ./a.out
2273 [Inferior 1 (process 10421) exited normally]
2276 In case you connected explicitly to the @code{native} target,
2277 @value{GDBN} remains connected even if all inferiors exit, ready for
2278 the next @code{run} command. Use the @code{disconnect} command to
2281 Examples of other commands that likewise respect the
2282 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2283 proc}, @code{info os}.
2285 @kindex set disable-randomization
2286 @item set disable-randomization
2287 @itemx set disable-randomization on
2288 This option (enabled by default in @value{GDBN}) will turn off the native
2289 randomization of the virtual address space of the started program. This option
2290 is useful for multiple debugging sessions to make the execution better
2291 reproducible and memory addresses reusable across debugging sessions.
2293 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2294 On @sc{gnu}/Linux you can get the same behavior using
2297 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2300 @item set disable-randomization off
2301 Leave the behavior of the started executable unchanged. Some bugs rear their
2302 ugly heads only when the program is loaded at certain addresses. If your bug
2303 disappears when you run the program under @value{GDBN}, that might be because
2304 @value{GDBN} by default disables the address randomization on platforms, such
2305 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2306 disable-randomization off} to try to reproduce such elusive bugs.
2308 On targets where it is available, virtual address space randomization
2309 protects the programs against certain kinds of security attacks. In these
2310 cases the attacker needs to know the exact location of a concrete executable
2311 code. Randomizing its location makes it impossible to inject jumps misusing
2312 a code at its expected addresses.
2314 Prelinking shared libraries provides a startup performance advantage but it
2315 makes addresses in these libraries predictable for privileged processes by
2316 having just unprivileged access at the target system. Reading the shared
2317 library binary gives enough information for assembling the malicious code
2318 misusing it. Still even a prelinked shared library can get loaded at a new
2319 random address just requiring the regular relocation process during the
2320 startup. Shared libraries not already prelinked are always loaded at
2321 a randomly chosen address.
2323 Position independent executables (PIE) contain position independent code
2324 similar to the shared libraries and therefore such executables get loaded at
2325 a randomly chosen address upon startup. PIE executables always load even
2326 already prelinked shared libraries at a random address. You can build such
2327 executable using @command{gcc -fPIE -pie}.
2329 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2330 (as long as the randomization is enabled).
2332 @item show disable-randomization
2333 Show the current setting of the explicit disable of the native randomization of
2334 the virtual address space of the started program.
2339 @section Your Program's Arguments
2341 @cindex arguments (to your program)
2342 The arguments to your program can be specified by the arguments of the
2344 They are passed to a shell, which expands wildcard characters and
2345 performs redirection of I/O, and thence to your program. Your
2346 @code{SHELL} environment variable (if it exists) specifies what shell
2347 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2348 the default shell (@file{/bin/sh} on Unix).
2350 On non-Unix systems, the program is usually invoked directly by
2351 @value{GDBN}, which emulates I/O redirection via the appropriate system
2352 calls, and the wildcard characters are expanded by the startup code of
2353 the program, not by the shell.
2355 @code{run} with no arguments uses the same arguments used by the previous
2356 @code{run}, or those set by the @code{set args} command.
2361 Specify the arguments to be used the next time your program is run. If
2362 @code{set args} has no arguments, @code{run} executes your program
2363 with no arguments. Once you have run your program with arguments,
2364 using @code{set args} before the next @code{run} is the only way to run
2365 it again without arguments.
2369 Show the arguments to give your program when it is started.
2373 @section Your Program's Environment
2375 @cindex environment (of your program)
2376 The @dfn{environment} consists of a set of environment variables and
2377 their values. Environment variables conventionally record such things as
2378 your user name, your home directory, your terminal type, and your search
2379 path for programs to run. Usually you set up environment variables with
2380 the shell and they are inherited by all the other programs you run. When
2381 debugging, it can be useful to try running your program with a modified
2382 environment without having to start @value{GDBN} over again.
2386 @item path @var{directory}
2387 Add @var{directory} to the front of the @code{PATH} environment variable
2388 (the search path for executables) that will be passed to your program.
2389 The value of @code{PATH} used by @value{GDBN} does not change.
2390 You may specify several directory names, separated by whitespace or by a
2391 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2392 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2393 is moved to the front, so it is searched sooner.
2395 You can use the string @samp{$cwd} to refer to whatever is the current
2396 working directory at the time @value{GDBN} searches the path. If you
2397 use @samp{.} instead, it refers to the directory where you executed the
2398 @code{path} command. @value{GDBN} replaces @samp{.} in the
2399 @var{directory} argument (with the current path) before adding
2400 @var{directory} to the search path.
2401 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2402 @c document that, since repeating it would be a no-op.
2406 Display the list of search paths for executables (the @code{PATH}
2407 environment variable).
2409 @kindex show environment
2410 @item show environment @r{[}@var{varname}@r{]}
2411 Print the value of environment variable @var{varname} to be given to
2412 your program when it starts. If you do not supply @var{varname},
2413 print the names and values of all environment variables to be given to
2414 your program. You can abbreviate @code{environment} as @code{env}.
2416 @kindex set environment
2417 @anchor{set environment}
2418 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2419 Set environment variable @var{varname} to @var{value}. The value
2420 changes for your program (and the shell @value{GDBN} uses to launch
2421 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2422 values of environment variables are just strings, and any
2423 interpretation is supplied by your program itself. The @var{value}
2424 parameter is optional; if it is eliminated, the variable is set to a
2426 @c "any string" here does not include leading, trailing
2427 @c blanks. Gnu asks: does anyone care?
2429 For example, this command:
2436 tells the debugged program, when subsequently run, that its user is named
2437 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2438 are not actually required.)
2440 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2441 which also inherits the environment set with @code{set environment}.
2442 If necessary, you can avoid that by using the @samp{env} program as a
2443 wrapper instead of using @code{set environment}. @xref{set
2444 exec-wrapper}, for an example doing just that.
2446 Environment variables that are set by the user are also transmitted to
2447 @command{gdbserver} to be used when starting the remote inferior.
2448 @pxref{QEnvironmentHexEncoded}.
2450 @kindex unset environment
2451 @anchor{unset environment}
2452 @item unset environment @var{varname}
2453 Remove variable @var{varname} from the environment to be passed to your
2454 program. This is different from @samp{set env @var{varname} =};
2455 @code{unset environment} removes the variable from the environment,
2456 rather than assigning it an empty value.
2458 Environment variables that are unset by the user are also unset on
2459 @command{gdbserver} when starting the remote inferior.
2460 @pxref{QEnvironmentUnset}.
2463 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2464 the shell indicated by your @code{SHELL} environment variable if it
2465 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2466 names a shell that runs an initialization file when started
2467 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2468 for the Z shell, or the file specified in the @samp{BASH_ENV}
2469 environment variable for BASH---any variables you set in that file
2470 affect your program. You may wish to move setting of environment
2471 variables to files that are only run when you sign on, such as
2472 @file{.login} or @file{.profile}.
2474 @node Working Directory
2475 @section Your Program's Working Directory
2477 @cindex working directory (of your program)
2478 Each time you start your program with @code{run}, the inferior will be
2479 initialized with the current working directory specified by the
2480 @kbd{set cwd} command. If no directory has been specified by this
2481 command, then the inferior will inherit @value{GDBN}'s current working
2482 directory as its working directory if native debugging, or it will
2483 inherit the remote server's current working directory if remote
2488 @cindex change inferior's working directory
2489 @anchor{set cwd command}
2490 @item set cwd @r{[}@var{directory}@r{]}
2491 Set the inferior's working directory to @var{directory}, which will be
2492 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2493 argument has been specified, the command clears the setting and resets
2494 it to an empty state. This setting has no effect on @value{GDBN}'s
2495 working directory, and it only takes effect the next time you start
2496 the inferior. The @file{~} in @var{directory} is a short for the
2497 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2498 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2499 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2502 You can also change @value{GDBN}'s current working directory by using
2503 the @code{cd} command.
2507 @cindex show inferior's working directory
2509 Show the inferior's working directory. If no directory has been
2510 specified by @kbd{set cwd}, then the default inferior's working
2511 directory is the same as @value{GDBN}'s working directory.
2514 @cindex change @value{GDBN}'s working directory
2516 @item cd @r{[}@var{directory}@r{]}
2517 Set the @value{GDBN} working directory to @var{directory}. If not
2518 given, @var{directory} uses @file{'~'}.
2520 The @value{GDBN} working directory serves as a default for the
2521 commands that specify files for @value{GDBN} to operate on.
2522 @xref{Files, ,Commands to Specify Files}.
2523 @xref{set cwd command}.
2527 Print the @value{GDBN} working directory.
2530 It is generally impossible to find the current working directory of
2531 the process being debugged (since a program can change its directory
2532 during its run). If you work on a system where @value{GDBN} supports
2533 the @code{info proc} command (@pxref{Process Information}), you can
2534 use the @code{info proc} command to find out the
2535 current working directory of the debuggee.
2538 @section Your Program's Input and Output
2543 By default, the program you run under @value{GDBN} does input and output to
2544 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2545 to its own terminal modes to interact with you, but it records the terminal
2546 modes your program was using and switches back to them when you continue
2547 running your program.
2550 @kindex info terminal
2552 Displays information recorded by @value{GDBN} about the terminal modes your
2556 You can redirect your program's input and/or output using shell
2557 redirection with the @code{run} command. For example,
2564 starts your program, diverting its output to the file @file{outfile}.
2567 @cindex controlling terminal
2568 Another way to specify where your program should do input and output is
2569 with the @code{tty} command. This command accepts a file name as
2570 argument, and causes this file to be the default for future @code{run}
2571 commands. It also resets the controlling terminal for the child
2572 process, for future @code{run} commands. For example,
2579 directs that processes started with subsequent @code{run} commands
2580 default to do input and output on the terminal @file{/dev/ttyb} and have
2581 that as their controlling terminal.
2583 An explicit redirection in @code{run} overrides the @code{tty} command's
2584 effect on the input/output device, but not its effect on the controlling
2587 When you use the @code{tty} command or redirect input in the @code{run}
2588 command, only the input @emph{for your program} is affected. The input
2589 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2590 for @code{set inferior-tty}.
2592 @cindex inferior tty
2593 @cindex set inferior controlling terminal
2594 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2595 display the name of the terminal that will be used for future runs of your
2599 @item set inferior-tty [ @var{tty} ]
2600 @kindex set inferior-tty
2601 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2602 restores the default behavior, which is to use the same terminal as
2605 @item show inferior-tty
2606 @kindex show inferior-tty
2607 Show the current tty for the program being debugged.
2611 @section Debugging an Already-running Process
2616 @item attach @var{process-id}
2617 This command attaches to a running process---one that was started
2618 outside @value{GDBN}. (@code{info files} shows your active
2619 targets.) The command takes as argument a process ID. The usual way to
2620 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2621 or with the @samp{jobs -l} shell command.
2623 @code{attach} does not repeat if you press @key{RET} a second time after
2624 executing the command.
2627 To use @code{attach}, your program must be running in an environment
2628 which supports processes; for example, @code{attach} does not work for
2629 programs on bare-board targets that lack an operating system. You must
2630 also have permission to send the process a signal.
2632 When you use @code{attach}, the debugger finds the program running in
2633 the process first by looking in the current working directory, then (if
2634 the program is not found) by using the source file search path
2635 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2636 the @code{file} command to load the program. @xref{Files, ,Commands to
2639 The first thing @value{GDBN} does after arranging to debug the specified
2640 process is to stop it. You can examine and modify an attached process
2641 with all the @value{GDBN} commands that are ordinarily available when
2642 you start processes with @code{run}. You can insert breakpoints; you
2643 can step and continue; you can modify storage. If you would rather the
2644 process continue running, you may use the @code{continue} command after
2645 attaching @value{GDBN} to the process.
2650 When you have finished debugging the attached process, you can use the
2651 @code{detach} command to release it from @value{GDBN} control. Detaching
2652 the process continues its execution. After the @code{detach} command,
2653 that process and @value{GDBN} become completely independent once more, and you
2654 are ready to @code{attach} another process or start one with @code{run}.
2655 @code{detach} does not repeat if you press @key{RET} again after
2656 executing the command.
2659 If you exit @value{GDBN} while you have an attached process, you detach
2660 that process. If you use the @code{run} command, you kill that process.
2661 By default, @value{GDBN} asks for confirmation if you try to do either of these
2662 things; you can control whether or not you need to confirm by using the
2663 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2667 @section Killing the Child Process
2672 Kill the child process in which your program is running under @value{GDBN}.
2675 This command is useful if you wish to debug a core dump instead of a
2676 running process. @value{GDBN} ignores any core dump file while your program
2679 On some operating systems, a program cannot be executed outside @value{GDBN}
2680 while you have breakpoints set on it inside @value{GDBN}. You can use the
2681 @code{kill} command in this situation to permit running your program
2682 outside the debugger.
2684 The @code{kill} command is also useful if you wish to recompile and
2685 relink your program, since on many systems it is impossible to modify an
2686 executable file while it is running in a process. In this case, when you
2687 next type @code{run}, @value{GDBN} notices that the file has changed, and
2688 reads the symbol table again (while trying to preserve your current
2689 breakpoint settings).
2691 @node Inferiors and Programs
2692 @section Debugging Multiple Inferiors and Programs
2694 @value{GDBN} lets you run and debug multiple programs in a single
2695 session. In addition, @value{GDBN} on some systems may let you run
2696 several programs simultaneously (otherwise you have to exit from one
2697 before starting another). In the most general case, you can have
2698 multiple threads of execution in each of multiple processes, launched
2699 from multiple executables.
2702 @value{GDBN} represents the state of each program execution with an
2703 object called an @dfn{inferior}. An inferior typically corresponds to
2704 a process, but is more general and applies also to targets that do not
2705 have processes. Inferiors may be created before a process runs, and
2706 may be retained after a process exits. Inferiors have unique
2707 identifiers that are different from process ids. Usually each
2708 inferior will also have its own distinct address space, although some
2709 embedded targets may have several inferiors running in different parts
2710 of a single address space. Each inferior may in turn have multiple
2711 threads running in it.
2713 To find out what inferiors exist at any moment, use @w{@code{info
2717 @kindex info inferiors [ @var{id}@dots{} ]
2718 @item info inferiors
2719 Print a list of all inferiors currently being managed by @value{GDBN}.
2720 By default all inferiors are printed, but the argument @var{id}@dots{}
2721 -- a space separated list of inferior numbers -- can be used to limit
2722 the display to just the requested inferiors.
2724 @value{GDBN} displays for each inferior (in this order):
2728 the inferior number assigned by @value{GDBN}
2731 the target system's inferior identifier
2734 the name of the executable the inferior is running.
2739 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2740 indicates the current inferior.
2744 @c end table here to get a little more width for example
2747 (@value{GDBP}) info inferiors
2748 Num Description Executable
2749 2 process 2307 hello
2750 * 1 process 3401 goodbye
2753 To switch focus between inferiors, use the @code{inferior} command:
2756 @kindex inferior @var{infno}
2757 @item inferior @var{infno}
2758 Make inferior number @var{infno} the current inferior. The argument
2759 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2760 in the first field of the @samp{info inferiors} display.
2763 @vindex $_inferior@r{, convenience variable}
2764 The debugger convenience variable @samp{$_inferior} contains the
2765 number of the current inferior. You may find this useful in writing
2766 breakpoint conditional expressions, command scripts, and so forth.
2767 @xref{Convenience Vars,, Convenience Variables}, for general
2768 information on convenience variables.
2770 You can get multiple executables into a debugging session via the
2771 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2772 systems @value{GDBN} can add inferiors to the debug session
2773 automatically by following calls to @code{fork} and @code{exec}. To
2774 remove inferiors from the debugging session use the
2775 @w{@code{remove-inferiors}} command.
2778 @kindex add-inferior
2779 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2780 Adds @var{n} inferiors to be run using @var{executable} as the
2781 executable; @var{n} defaults to 1. If no executable is specified,
2782 the inferiors begins empty, with no program. You can still assign or
2783 change the program assigned to the inferior at any time by using the
2784 @code{file} command with the executable name as its argument.
2786 @kindex clone-inferior
2787 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2788 Adds @var{n} inferiors ready to execute the same program as inferior
2789 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2790 number of the current inferior. This is a convenient command when you
2791 want to run another instance of the inferior you are debugging.
2794 (@value{GDBP}) info inferiors
2795 Num Description Executable
2796 * 1 process 29964 helloworld
2797 (@value{GDBP}) clone-inferior
2800 (@value{GDBP}) info inferiors
2801 Num Description Executable
2803 * 1 process 29964 helloworld
2806 You can now simply switch focus to inferior 2 and run it.
2808 @kindex remove-inferiors
2809 @item remove-inferiors @var{infno}@dots{}
2810 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2811 possible to remove an inferior that is running with this command. For
2812 those, use the @code{kill} or @code{detach} command first.
2816 To quit debugging one of the running inferiors that is not the current
2817 inferior, you can either detach from it by using the @w{@code{detach
2818 inferior}} command (allowing it to run independently), or kill it
2819 using the @w{@code{kill inferiors}} command:
2822 @kindex detach inferiors @var{infno}@dots{}
2823 @item detach inferior @var{infno}@dots{}
2824 Detach from the inferior or inferiors identified by @value{GDBN}
2825 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2826 still stays on the list of inferiors shown by @code{info inferiors},
2827 but its Description will show @samp{<null>}.
2829 @kindex kill inferiors @var{infno}@dots{}
2830 @item kill inferiors @var{infno}@dots{}
2831 Kill the inferior or inferiors identified by @value{GDBN} inferior
2832 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2833 stays on the list of inferiors shown by @code{info inferiors}, but its
2834 Description will show @samp{<null>}.
2837 After the successful completion of a command such as @code{detach},
2838 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2839 a normal process exit, the inferior is still valid and listed with
2840 @code{info inferiors}, ready to be restarted.
2843 To be notified when inferiors are started or exit under @value{GDBN}'s
2844 control use @w{@code{set print inferior-events}}:
2847 @kindex set print inferior-events
2848 @cindex print messages on inferior start and exit
2849 @item set print inferior-events
2850 @itemx set print inferior-events on
2851 @itemx set print inferior-events off
2852 The @code{set print inferior-events} command allows you to enable or
2853 disable printing of messages when @value{GDBN} notices that new
2854 inferiors have started or that inferiors have exited or have been
2855 detached. By default, these messages will not be printed.
2857 @kindex show print inferior-events
2858 @item show print inferior-events
2859 Show whether messages will be printed when @value{GDBN} detects that
2860 inferiors have started, exited or have been detached.
2863 Many commands will work the same with multiple programs as with a
2864 single program: e.g., @code{print myglobal} will simply display the
2865 value of @code{myglobal} in the current inferior.
2868 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2869 get more info about the relationship of inferiors, programs, address
2870 spaces in a debug session. You can do that with the @w{@code{maint
2871 info program-spaces}} command.
2874 @kindex maint info program-spaces
2875 @item maint info program-spaces
2876 Print a list of all program spaces currently being managed by
2879 @value{GDBN} displays for each program space (in this order):
2883 the program space number assigned by @value{GDBN}
2886 the name of the executable loaded into the program space, with e.g.,
2887 the @code{file} command.
2892 An asterisk @samp{*} preceding the @value{GDBN} program space number
2893 indicates the current program space.
2895 In addition, below each program space line, @value{GDBN} prints extra
2896 information that isn't suitable to display in tabular form. For
2897 example, the list of inferiors bound to the program space.
2900 (@value{GDBP}) maint info program-spaces
2904 Bound inferiors: ID 1 (process 21561)
2907 Here we can see that no inferior is running the program @code{hello},
2908 while @code{process 21561} is running the program @code{goodbye}. On
2909 some targets, it is possible that multiple inferiors are bound to the
2910 same program space. The most common example is that of debugging both
2911 the parent and child processes of a @code{vfork} call. For example,
2914 (@value{GDBP}) maint info program-spaces
2917 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2920 Here, both inferior 2 and inferior 1 are running in the same program
2921 space as a result of inferior 1 having executed a @code{vfork} call.
2925 @section Debugging Programs with Multiple Threads
2927 @cindex threads of execution
2928 @cindex multiple threads
2929 @cindex switching threads
2930 In some operating systems, such as GNU/Linux and Solaris, a single program
2931 may have more than one @dfn{thread} of execution. The precise semantics
2932 of threads differ from one operating system to another, but in general
2933 the threads of a single program are akin to multiple processes---except
2934 that they share one address space (that is, they can all examine and
2935 modify the same variables). On the other hand, each thread has its own
2936 registers and execution stack, and perhaps private memory.
2938 @value{GDBN} provides these facilities for debugging multi-thread
2942 @item automatic notification of new threads
2943 @item @samp{thread @var{thread-id}}, a command to switch among threads
2944 @item @samp{info threads}, a command to inquire about existing threads
2945 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
2946 a command to apply a command to a list of threads
2947 @item thread-specific breakpoints
2948 @item @samp{set print thread-events}, which controls printing of
2949 messages on thread start and exit.
2950 @item @samp{set libthread-db-search-path @var{path}}, which lets
2951 the user specify which @code{libthread_db} to use if the default choice
2952 isn't compatible with the program.
2955 @cindex focus of debugging
2956 @cindex current thread
2957 The @value{GDBN} thread debugging facility allows you to observe all
2958 threads while your program runs---but whenever @value{GDBN} takes
2959 control, one thread in particular is always the focus of debugging.
2960 This thread is called the @dfn{current thread}. Debugging commands show
2961 program information from the perspective of the current thread.
2963 @cindex @code{New} @var{systag} message
2964 @cindex thread identifier (system)
2965 @c FIXME-implementors!! It would be more helpful if the [New...] message
2966 @c included GDB's numeric thread handle, so you could just go to that
2967 @c thread without first checking `info threads'.
2968 Whenever @value{GDBN} detects a new thread in your program, it displays
2969 the target system's identification for the thread with a message in the
2970 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2971 whose form varies depending on the particular system. For example, on
2972 @sc{gnu}/Linux, you might see
2975 [New Thread 0x41e02940 (LWP 25582)]
2979 when @value{GDBN} notices a new thread. In contrast, on other systems,
2980 the @var{systag} is simply something like @samp{process 368}, with no
2983 @c FIXME!! (1) Does the [New...] message appear even for the very first
2984 @c thread of a program, or does it only appear for the
2985 @c second---i.e.@: when it becomes obvious we have a multithread
2987 @c (2) *Is* there necessarily a first thread always? Or do some
2988 @c multithread systems permit starting a program with multiple
2989 @c threads ab initio?
2991 @anchor{thread numbers}
2992 @cindex thread number, per inferior
2993 @cindex thread identifier (GDB)
2994 For debugging purposes, @value{GDBN} associates its own thread number
2995 ---always a single integer---with each thread of an inferior. This
2996 number is unique between all threads of an inferior, but not unique
2997 between threads of different inferiors.
2999 @cindex qualified thread ID
3000 You can refer to a given thread in an inferior using the qualified
3001 @var{inferior-num}.@var{thread-num} syntax, also known as
3002 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3003 number and @var{thread-num} being the thread number of the given
3004 inferior. For example, thread @code{2.3} refers to thread number 3 of
3005 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3006 then @value{GDBN} infers you're referring to a thread of the current
3009 Until you create a second inferior, @value{GDBN} does not show the
3010 @var{inferior-num} part of thread IDs, even though you can always use
3011 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3012 of inferior 1, the initial inferior.
3014 @anchor{thread ID lists}
3015 @cindex thread ID lists
3016 Some commands accept a space-separated @dfn{thread ID list} as
3017 argument. A list element can be:
3021 A thread ID as shown in the first field of the @samp{info threads}
3022 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3026 A range of thread numbers, again with or without an inferior
3027 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3028 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3031 All threads of an inferior, specified with a star wildcard, with or
3032 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3033 @samp{1.*}) or @code{*}. The former refers to all threads of the
3034 given inferior, and the latter form without an inferior qualifier
3035 refers to all threads of the current inferior.
3039 For example, if the current inferior is 1, and inferior 7 has one
3040 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3041 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3042 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3043 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3047 @anchor{global thread numbers}
3048 @cindex global thread number
3049 @cindex global thread identifier (GDB)
3050 In addition to a @emph{per-inferior} number, each thread is also
3051 assigned a unique @emph{global} number, also known as @dfn{global
3052 thread ID}, a single integer. Unlike the thread number component of
3053 the thread ID, no two threads have the same global ID, even when
3054 you're debugging multiple inferiors.
3056 From @value{GDBN}'s perspective, a process always has at least one
3057 thread. In other words, @value{GDBN} assigns a thread number to the
3058 program's ``main thread'' even if the program is not multi-threaded.
3060 @vindex $_thread@r{, convenience variable}
3061 @vindex $_gthread@r{, convenience variable}
3062 The debugger convenience variables @samp{$_thread} and
3063 @samp{$_gthread} contain, respectively, the per-inferior thread number
3064 and the global thread number of the current thread. You may find this
3065 useful in writing breakpoint conditional expressions, command scripts,
3066 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3067 general information on convenience variables.
3069 If @value{GDBN} detects the program is multi-threaded, it augments the
3070 usual message about stopping at a breakpoint with the ID and name of
3071 the thread that hit the breakpoint.
3074 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3077 Likewise when the program receives a signal:
3080 Thread 1 "main" received signal SIGINT, Interrupt.
3084 @kindex info threads
3085 @item info threads @r{[}@var{thread-id-list}@r{]}
3087 Display information about one or more threads. With no arguments
3088 displays information about all threads. You can specify the list of
3089 threads that you want to display using the thread ID list syntax
3090 (@pxref{thread ID lists}).
3092 @value{GDBN} displays for each thread (in this order):
3096 the per-inferior thread number assigned by @value{GDBN}
3099 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3100 option was specified
3103 the target system's thread identifier (@var{systag})
3106 the thread's name, if one is known. A thread can either be named by
3107 the user (see @code{thread name}, below), or, in some cases, by the
3111 the current stack frame summary for that thread
3115 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3116 indicates the current thread.
3120 @c end table here to get a little more width for example
3123 (@value{GDBP}) info threads
3125 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3126 2 process 35 thread 23 0x34e5 in sigpause ()
3127 3 process 35 thread 27 0x34e5 in sigpause ()
3131 If you're debugging multiple inferiors, @value{GDBN} displays thread
3132 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3133 Otherwise, only @var{thread-num} is shown.
3135 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3136 indicating each thread's global thread ID:
3139 (@value{GDBP}) info threads
3140 Id GId Target Id Frame
3141 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3142 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3143 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3144 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3147 On Solaris, you can display more information about user threads with a
3148 Solaris-specific command:
3151 @item maint info sol-threads
3152 @kindex maint info sol-threads
3153 @cindex thread info (Solaris)
3154 Display info on Solaris user threads.
3158 @kindex thread @var{thread-id}
3159 @item thread @var{thread-id}
3160 Make thread ID @var{thread-id} the current thread. The command
3161 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3162 the first field of the @samp{info threads} display, with or without an
3163 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3165 @value{GDBN} responds by displaying the system identifier of the
3166 thread you selected, and its current stack frame summary:
3169 (@value{GDBP}) thread 2
3170 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3171 #0 some_function (ignore=0x0) at example.c:8
3172 8 printf ("hello\n");
3176 As with the @samp{[New @dots{}]} message, the form of the text after
3177 @samp{Switching to} depends on your system's conventions for identifying
3180 @kindex thread apply
3181 @cindex apply command to several threads
3182 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3183 The @code{thread apply} command allows you to apply the named
3184 @var{command} to one or more threads. Specify the threads that you
3185 want affected using the thread ID list syntax (@pxref{thread ID
3186 lists}), or specify @code{all} to apply to all threads. To apply a
3187 command to all threads in descending order, type @kbd{thread apply all
3188 @var{command}}. To apply a command to all threads in ascending order,
3189 type @kbd{thread apply all -ascending @var{command}}.
3191 The @var{flag} arguments control what output to produce and how to handle
3192 errors raised when applying @var{command} to a thread. @var{flag}
3193 must start with a @code{-} directly followed by one letter in
3194 @code{qcs}. If several flags are provided, they must be given
3195 individually, such as @code{-c -q}.
3197 By default, @value{GDBN} displays some thread information before the
3198 output produced by @var{command}, and an error raised during the
3199 execution of a @var{command} will abort @code{thread apply}. The
3200 following flags can be used to fine-tune this behavior:
3204 The flag @code{-c}, which stands for @samp{continue}, causes any
3205 errors in @var{command} to be displayed, and the execution of
3206 @code{thread apply} then continues.
3208 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3209 or empty output produced by a @var{command} to be silently ignored.
3210 That is, the execution continues, but the thread information and errors
3213 The flag @code{-q} (@samp{quiet}) disables printing the thread
3217 Flags @code{-c} and @code{-s} cannot be used together.
3220 @cindex apply command to all threads (ignoring errors and empty output)
3221 @item taas @var{command}
3222 Shortcut for @code{thread apply all -s @var{command}}.
3223 Applies @var{command} on all threads, ignoring errors and empty output.
3226 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3227 @item tfaas @var{command}
3228 Shortcut for @code{thread apply all -s frame apply all -s @var{command}}.
3229 Applies @var{command} on all frames of all threads, ignoring errors
3230 and empty output. Note that the flag @code{-s} is specified twice:
3231 The first @code{-s} ensures that @code{thread apply} only shows the thread
3232 information of the threads for which @code{frame apply} produces
3233 some output. The second @code{-s} is needed to ensure that @code{frame
3234 apply} shows the frame information of a frame only if the
3235 @var{command} successfully produced some output.
3237 It can for example be used to print a local variable or a function
3238 argument without knowing the thread or frame where this variable or argument
3241 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3246 @cindex name a thread
3247 @item thread name [@var{name}]
3248 This command assigns a name to the current thread. If no argument is
3249 given, any existing user-specified name is removed. The thread name
3250 appears in the @samp{info threads} display.
3252 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3253 determine the name of the thread as given by the OS. On these
3254 systems, a name specified with @samp{thread name} will override the
3255 system-give name, and removing the user-specified name will cause
3256 @value{GDBN} to once again display the system-specified name.
3259 @cindex search for a thread
3260 @item thread find [@var{regexp}]
3261 Search for and display thread ids whose name or @var{systag}
3262 matches the supplied regular expression.
3264 As well as being the complement to the @samp{thread name} command,
3265 this command also allows you to identify a thread by its target
3266 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3270 (@value{GDBN}) thread find 26688
3271 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3272 (@value{GDBN}) info thread 4
3274 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3277 @kindex set print thread-events
3278 @cindex print messages on thread start and exit
3279 @item set print thread-events
3280 @itemx set print thread-events on
3281 @itemx set print thread-events off
3282 The @code{set print thread-events} command allows you to enable or
3283 disable printing of messages when @value{GDBN} notices that new threads have
3284 started or that threads have exited. By default, these messages will
3285 be printed if detection of these events is supported by the target.
3286 Note that these messages cannot be disabled on all targets.
3288 @kindex show print thread-events
3289 @item show print thread-events
3290 Show whether messages will be printed when @value{GDBN} detects that threads
3291 have started and exited.
3294 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3295 more information about how @value{GDBN} behaves when you stop and start
3296 programs with multiple threads.
3298 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3299 watchpoints in programs with multiple threads.
3301 @anchor{set libthread-db-search-path}
3303 @kindex set libthread-db-search-path
3304 @cindex search path for @code{libthread_db}
3305 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3306 If this variable is set, @var{path} is a colon-separated list of
3307 directories @value{GDBN} will use to search for @code{libthread_db}.
3308 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3309 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3310 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3313 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3314 @code{libthread_db} library to obtain information about threads in the
3315 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3316 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3317 specific thread debugging library loading is enabled
3318 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3320 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3321 refers to the default system directories that are
3322 normally searched for loading shared libraries. The @samp{$sdir} entry
3323 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3324 (@pxref{libthread_db.so.1 file}).
3326 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3327 refers to the directory from which @code{libpthread}
3328 was loaded in the inferior process.
3330 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3331 @value{GDBN} attempts to initialize it with the current inferior process.
3332 If this initialization fails (which could happen because of a version
3333 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3334 will unload @code{libthread_db}, and continue with the next directory.
3335 If none of @code{libthread_db} libraries initialize successfully,
3336 @value{GDBN} will issue a warning and thread debugging will be disabled.
3338 Setting @code{libthread-db-search-path} is currently implemented
3339 only on some platforms.
3341 @kindex show libthread-db-search-path
3342 @item show libthread-db-search-path
3343 Display current libthread_db search path.
3345 @kindex set debug libthread-db
3346 @kindex show debug libthread-db
3347 @cindex debugging @code{libthread_db}
3348 @item set debug libthread-db
3349 @itemx show debug libthread-db
3350 Turns on or off display of @code{libthread_db}-related events.
3351 Use @code{1} to enable, @code{0} to disable.
3355 @section Debugging Forks
3357 @cindex fork, debugging programs which call
3358 @cindex multiple processes
3359 @cindex processes, multiple
3360 On most systems, @value{GDBN} has no special support for debugging
3361 programs which create additional processes using the @code{fork}
3362 function. When a program forks, @value{GDBN} will continue to debug the
3363 parent process and the child process will run unimpeded. If you have
3364 set a breakpoint in any code which the child then executes, the child
3365 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3366 will cause it to terminate.
3368 However, if you want to debug the child process there is a workaround
3369 which isn't too painful. Put a call to @code{sleep} in the code which
3370 the child process executes after the fork. It may be useful to sleep
3371 only if a certain environment variable is set, or a certain file exists,
3372 so that the delay need not occur when you don't want to run @value{GDBN}
3373 on the child. While the child is sleeping, use the @code{ps} program to
3374 get its process ID. Then tell @value{GDBN} (a new invocation of
3375 @value{GDBN} if you are also debugging the parent process) to attach to
3376 the child process (@pxref{Attach}). From that point on you can debug
3377 the child process just like any other process which you attached to.
3379 On some systems, @value{GDBN} provides support for debugging programs
3380 that create additional processes using the @code{fork} or @code{vfork}
3381 functions. On @sc{gnu}/Linux platforms, this feature is supported
3382 with kernel version 2.5.46 and later.
3384 The fork debugging commands are supported in native mode and when
3385 connected to @code{gdbserver} in either @code{target remote} mode or
3386 @code{target extended-remote} mode.
3388 By default, when a program forks, @value{GDBN} will continue to debug
3389 the parent process and the child process will run unimpeded.
3391 If you want to follow the child process instead of the parent process,
3392 use the command @w{@code{set follow-fork-mode}}.
3395 @kindex set follow-fork-mode
3396 @item set follow-fork-mode @var{mode}
3397 Set the debugger response to a program call of @code{fork} or
3398 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3399 process. The @var{mode} argument can be:
3403 The original process is debugged after a fork. The child process runs
3404 unimpeded. This is the default.
3407 The new process is debugged after a fork. The parent process runs
3412 @kindex show follow-fork-mode
3413 @item show follow-fork-mode
3414 Display the current debugger response to a @code{fork} or @code{vfork} call.
3417 @cindex debugging multiple processes
3418 On Linux, if you want to debug both the parent and child processes, use the
3419 command @w{@code{set detach-on-fork}}.
3422 @kindex set detach-on-fork
3423 @item set detach-on-fork @var{mode}
3424 Tells gdb whether to detach one of the processes after a fork, or
3425 retain debugger control over them both.
3429 The child process (or parent process, depending on the value of
3430 @code{follow-fork-mode}) will be detached and allowed to run
3431 independently. This is the default.
3434 Both processes will be held under the control of @value{GDBN}.
3435 One process (child or parent, depending on the value of
3436 @code{follow-fork-mode}) is debugged as usual, while the other
3441 @kindex show detach-on-fork
3442 @item show detach-on-fork
3443 Show whether detach-on-fork mode is on/off.
3446 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3447 will retain control of all forked processes (including nested forks).
3448 You can list the forked processes under the control of @value{GDBN} by
3449 using the @w{@code{info inferiors}} command, and switch from one fork
3450 to another by using the @code{inferior} command (@pxref{Inferiors and
3451 Programs, ,Debugging Multiple Inferiors and Programs}).
3453 To quit debugging one of the forked processes, you can either detach
3454 from it by using the @w{@code{detach inferiors}} command (allowing it
3455 to run independently), or kill it using the @w{@code{kill inferiors}}
3456 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3459 If you ask to debug a child process and a @code{vfork} is followed by an
3460 @code{exec}, @value{GDBN} executes the new target up to the first
3461 breakpoint in the new target. If you have a breakpoint set on
3462 @code{main} in your original program, the breakpoint will also be set on
3463 the child process's @code{main}.
3465 On some systems, when a child process is spawned by @code{vfork}, you
3466 cannot debug the child or parent until an @code{exec} call completes.
3468 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3469 call executes, the new target restarts. To restart the parent
3470 process, use the @code{file} command with the parent executable name
3471 as its argument. By default, after an @code{exec} call executes,
3472 @value{GDBN} discards the symbols of the previous executable image.
3473 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3477 @kindex set follow-exec-mode
3478 @item set follow-exec-mode @var{mode}
3480 Set debugger response to a program call of @code{exec}. An
3481 @code{exec} call replaces the program image of a process.
3483 @code{follow-exec-mode} can be:
3487 @value{GDBN} creates a new inferior and rebinds the process to this
3488 new inferior. The program the process was running before the
3489 @code{exec} call can be restarted afterwards by restarting the
3495 (@value{GDBP}) info inferiors
3497 Id Description Executable
3500 process 12020 is executing new program: prog2
3501 Program exited normally.
3502 (@value{GDBP}) info inferiors
3503 Id Description Executable
3509 @value{GDBN} keeps the process bound to the same inferior. The new
3510 executable image replaces the previous executable loaded in the
3511 inferior. Restarting the inferior after the @code{exec} call, with
3512 e.g., the @code{run} command, restarts the executable the process was
3513 running after the @code{exec} call. This is the default mode.
3518 (@value{GDBP}) info inferiors
3519 Id Description Executable
3522 process 12020 is executing new program: prog2
3523 Program exited normally.
3524 (@value{GDBP}) info inferiors
3525 Id Description Executable
3532 @code{follow-exec-mode} is supported in native mode and
3533 @code{target extended-remote} mode.
3535 You can use the @code{catch} command to make @value{GDBN} stop whenever
3536 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3537 Catchpoints, ,Setting Catchpoints}.
3539 @node Checkpoint/Restart
3540 @section Setting a @emph{Bookmark} to Return to Later
3545 @cindex snapshot of a process
3546 @cindex rewind program state
3548 On certain operating systems@footnote{Currently, only
3549 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3550 program's state, called a @dfn{checkpoint}, and come back to it
3553 Returning to a checkpoint effectively undoes everything that has
3554 happened in the program since the @code{checkpoint} was saved. This
3555 includes changes in memory, registers, and even (within some limits)
3556 system state. Effectively, it is like going back in time to the
3557 moment when the checkpoint was saved.
3559 Thus, if you're stepping thru a program and you think you're
3560 getting close to the point where things go wrong, you can save
3561 a checkpoint. Then, if you accidentally go too far and miss
3562 the critical statement, instead of having to restart your program
3563 from the beginning, you can just go back to the checkpoint and
3564 start again from there.
3566 This can be especially useful if it takes a lot of time or
3567 steps to reach the point where you think the bug occurs.
3569 To use the @code{checkpoint}/@code{restart} method of debugging:
3574 Save a snapshot of the debugged program's current execution state.
3575 The @code{checkpoint} command takes no arguments, but each checkpoint
3576 is assigned a small integer id, similar to a breakpoint id.
3578 @kindex info checkpoints
3579 @item info checkpoints
3580 List the checkpoints that have been saved in the current debugging
3581 session. For each checkpoint, the following information will be
3588 @item Source line, or label
3591 @kindex restart @var{checkpoint-id}
3592 @item restart @var{checkpoint-id}
3593 Restore the program state that was saved as checkpoint number
3594 @var{checkpoint-id}. All program variables, registers, stack frames
3595 etc.@: will be returned to the values that they had when the checkpoint
3596 was saved. In essence, gdb will ``wind back the clock'' to the point
3597 in time when the checkpoint was saved.
3599 Note that breakpoints, @value{GDBN} variables, command history etc.
3600 are not affected by restoring a checkpoint. In general, a checkpoint
3601 only restores things that reside in the program being debugged, not in
3604 @kindex delete checkpoint @var{checkpoint-id}
3605 @item delete checkpoint @var{checkpoint-id}
3606 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3610 Returning to a previously saved checkpoint will restore the user state
3611 of the program being debugged, plus a significant subset of the system
3612 (OS) state, including file pointers. It won't ``un-write'' data from
3613 a file, but it will rewind the file pointer to the previous location,
3614 so that the previously written data can be overwritten. For files
3615 opened in read mode, the pointer will also be restored so that the
3616 previously read data can be read again.
3618 Of course, characters that have been sent to a printer (or other
3619 external device) cannot be ``snatched back'', and characters received
3620 from eg.@: a serial device can be removed from internal program buffers,
3621 but they cannot be ``pushed back'' into the serial pipeline, ready to
3622 be received again. Similarly, the actual contents of files that have
3623 been changed cannot be restored (at this time).
3625 However, within those constraints, you actually can ``rewind'' your
3626 program to a previously saved point in time, and begin debugging it
3627 again --- and you can change the course of events so as to debug a
3628 different execution path this time.
3630 @cindex checkpoints and process id
3631 Finally, there is one bit of internal program state that will be
3632 different when you return to a checkpoint --- the program's process
3633 id. Each checkpoint will have a unique process id (or @var{pid}),
3634 and each will be different from the program's original @var{pid}.
3635 If your program has saved a local copy of its process id, this could
3636 potentially pose a problem.
3638 @subsection A Non-obvious Benefit of Using Checkpoints
3640 On some systems such as @sc{gnu}/Linux, address space randomization
3641 is performed on new processes for security reasons. This makes it
3642 difficult or impossible to set a breakpoint, or watchpoint, on an
3643 absolute address if you have to restart the program, since the
3644 absolute location of a symbol will change from one execution to the
3647 A checkpoint, however, is an @emph{identical} copy of a process.
3648 Therefore if you create a checkpoint at (eg.@:) the start of main,
3649 and simply return to that checkpoint instead of restarting the
3650 process, you can avoid the effects of address randomization and
3651 your symbols will all stay in the same place.
3654 @chapter Stopping and Continuing
3656 The principal purposes of using a debugger are so that you can stop your
3657 program before it terminates; or so that, if your program runs into
3658 trouble, you can investigate and find out why.
3660 Inside @value{GDBN}, your program may stop for any of several reasons,
3661 such as a signal, a breakpoint, or reaching a new line after a
3662 @value{GDBN} command such as @code{step}. You may then examine and
3663 change variables, set new breakpoints or remove old ones, and then
3664 continue execution. Usually, the messages shown by @value{GDBN} provide
3665 ample explanation of the status of your program---but you can also
3666 explicitly request this information at any time.
3669 @kindex info program
3671 Display information about the status of your program: whether it is
3672 running or not, what process it is, and why it stopped.
3676 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3677 * Continuing and Stepping:: Resuming execution
3678 * Skipping Over Functions and Files::
3679 Skipping over functions and files
3681 * Thread Stops:: Stopping and starting multi-thread programs
3685 @section Breakpoints, Watchpoints, and Catchpoints
3688 A @dfn{breakpoint} makes your program stop whenever a certain point in
3689 the program is reached. For each breakpoint, you can add conditions to
3690 control in finer detail whether your program stops. You can set
3691 breakpoints with the @code{break} command and its variants (@pxref{Set
3692 Breaks, ,Setting Breakpoints}), to specify the place where your program
3693 should stop by line number, function name or exact address in the
3696 On some systems, you can set breakpoints in shared libraries before
3697 the executable is run.
3700 @cindex data breakpoints
3701 @cindex memory tracing
3702 @cindex breakpoint on memory address
3703 @cindex breakpoint on variable modification
3704 A @dfn{watchpoint} is a special breakpoint that stops your program
3705 when the value of an expression changes. The expression may be a value
3706 of a variable, or it could involve values of one or more variables
3707 combined by operators, such as @samp{a + b}. This is sometimes called
3708 @dfn{data breakpoints}. You must use a different command to set
3709 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3710 from that, you can manage a watchpoint like any other breakpoint: you
3711 enable, disable, and delete both breakpoints and watchpoints using the
3714 You can arrange to have values from your program displayed automatically
3715 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3719 @cindex breakpoint on events
3720 A @dfn{catchpoint} is another special breakpoint that stops your program
3721 when a certain kind of event occurs, such as the throwing of a C@t{++}
3722 exception or the loading of a library. As with watchpoints, you use a
3723 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3724 Catchpoints}), but aside from that, you can manage a catchpoint like any
3725 other breakpoint. (To stop when your program receives a signal, use the
3726 @code{handle} command; see @ref{Signals, ,Signals}.)
3728 @cindex breakpoint numbers
3729 @cindex numbers for breakpoints
3730 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3731 catchpoint when you create it; these numbers are successive integers
3732 starting with one. In many of the commands for controlling various
3733 features of breakpoints you use the breakpoint number to say which
3734 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3735 @dfn{disabled}; if disabled, it has no effect on your program until you
3738 @cindex breakpoint ranges
3739 @cindex breakpoint lists
3740 @cindex ranges of breakpoints
3741 @cindex lists of breakpoints
3742 Some @value{GDBN} commands accept a space-separated list of breakpoints
3743 on which to operate. A list element can be either a single breakpoint number,
3744 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3745 When a breakpoint list is given to a command, all breakpoints in that list
3749 * Set Breaks:: Setting breakpoints
3750 * Set Watchpoints:: Setting watchpoints
3751 * Set Catchpoints:: Setting catchpoints
3752 * Delete Breaks:: Deleting breakpoints
3753 * Disabling:: Disabling breakpoints
3754 * Conditions:: Break conditions
3755 * Break Commands:: Breakpoint command lists
3756 * Dynamic Printf:: Dynamic printf
3757 * Save Breakpoints:: How to save breakpoints in a file
3758 * Static Probe Points:: Listing static probe points
3759 * Error in Breakpoints:: ``Cannot insert breakpoints''
3760 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3764 @subsection Setting Breakpoints
3766 @c FIXME LMB what does GDB do if no code on line of breakpt?
3767 @c consider in particular declaration with/without initialization.
3769 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3772 @kindex b @r{(@code{break})}
3773 @vindex $bpnum@r{, convenience variable}
3774 @cindex latest breakpoint
3775 Breakpoints are set with the @code{break} command (abbreviated
3776 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3777 number of the breakpoint you've set most recently; see @ref{Convenience
3778 Vars,, Convenience Variables}, for a discussion of what you can do with
3779 convenience variables.
3782 @item break @var{location}
3783 Set a breakpoint at the given @var{location}, which can specify a
3784 function name, a line number, or an address of an instruction.
3785 (@xref{Specify Location}, for a list of all the possible ways to
3786 specify a @var{location}.) The breakpoint will stop your program just
3787 before it executes any of the code in the specified @var{location}.
3789 When using source languages that permit overloading of symbols, such as
3790 C@t{++}, a function name may refer to more than one possible place to break.
3791 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3794 It is also possible to insert a breakpoint that will stop the program
3795 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3796 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3799 When called without any arguments, @code{break} sets a breakpoint at
3800 the next instruction to be executed in the selected stack frame
3801 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3802 innermost, this makes your program stop as soon as control
3803 returns to that frame. This is similar to the effect of a
3804 @code{finish} command in the frame inside the selected frame---except
3805 that @code{finish} does not leave an active breakpoint. If you use
3806 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3807 the next time it reaches the current location; this may be useful
3810 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3811 least one instruction has been executed. If it did not do this, you
3812 would be unable to proceed past a breakpoint without first disabling the
3813 breakpoint. This rule applies whether or not the breakpoint already
3814 existed when your program stopped.
3816 @item break @dots{} if @var{cond}
3817 Set a breakpoint with condition @var{cond}; evaluate the expression
3818 @var{cond} each time the breakpoint is reached, and stop only if the
3819 value is nonzero---that is, if @var{cond} evaluates as true.
3820 @samp{@dots{}} stands for one of the possible arguments described
3821 above (or no argument) specifying where to break. @xref{Conditions,
3822 ,Break Conditions}, for more information on breakpoint conditions.
3825 @item tbreak @var{args}
3826 Set a breakpoint enabled only for one stop. The @var{args} are the
3827 same as for the @code{break} command, and the breakpoint is set in the same
3828 way, but the breakpoint is automatically deleted after the first time your
3829 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3832 @cindex hardware breakpoints
3833 @item hbreak @var{args}
3834 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3835 @code{break} command and the breakpoint is set in the same way, but the
3836 breakpoint requires hardware support and some target hardware may not
3837 have this support. The main purpose of this is EPROM/ROM code
3838 debugging, so you can set a breakpoint at an instruction without
3839 changing the instruction. This can be used with the new trap-generation
3840 provided by SPARClite DSU and most x86-based targets. These targets
3841 will generate traps when a program accesses some data or instruction
3842 address that is assigned to the debug registers. However the hardware
3843 breakpoint registers can take a limited number of breakpoints. For
3844 example, on the DSU, only two data breakpoints can be set at a time, and
3845 @value{GDBN} will reject this command if more than two are used. Delete
3846 or disable unused hardware breakpoints before setting new ones
3847 (@pxref{Disabling, ,Disabling Breakpoints}).
3848 @xref{Conditions, ,Break Conditions}.
3849 For remote targets, you can restrict the number of hardware
3850 breakpoints @value{GDBN} will use, see @ref{set remote
3851 hardware-breakpoint-limit}.
3854 @item thbreak @var{args}
3855 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3856 are the same as for the @code{hbreak} command and the breakpoint is set in
3857 the same way. However, like the @code{tbreak} command,
3858 the breakpoint is automatically deleted after the
3859 first time your program stops there. Also, like the @code{hbreak}
3860 command, the breakpoint requires hardware support and some target hardware
3861 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3862 See also @ref{Conditions, ,Break Conditions}.
3865 @cindex regular expression
3866 @cindex breakpoints at functions matching a regexp
3867 @cindex set breakpoints in many functions
3868 @item rbreak @var{regex}
3869 Set breakpoints on all functions matching the regular expression
3870 @var{regex}. This command sets an unconditional breakpoint on all
3871 matches, printing a list of all breakpoints it set. Once these
3872 breakpoints are set, they are treated just like the breakpoints set with
3873 the @code{break} command. You can delete them, disable them, or make
3874 them conditional the same way as any other breakpoint.
3876 In programs using different languages, @value{GDBN} chooses the syntax
3877 to print the list of all breakpoints it sets according to the
3878 @samp{set language} value: using @samp{set language auto}
3879 (see @ref{Automatically, ,Set Language Automatically}) means to use the
3880 language of the breakpoint's function, other values mean to use
3881 the manually specified language (see @ref{Manually, ,Set Language Manually}).
3883 The syntax of the regular expression is the standard one used with tools
3884 like @file{grep}. Note that this is different from the syntax used by
3885 shells, so for instance @code{foo*} matches all functions that include
3886 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3887 @code{.*} leading and trailing the regular expression you supply, so to
3888 match only functions that begin with @code{foo}, use @code{^foo}.
3890 @cindex non-member C@t{++} functions, set breakpoint in
3891 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3892 breakpoints on overloaded functions that are not members of any special
3895 @cindex set breakpoints on all functions
3896 The @code{rbreak} command can be used to set breakpoints in
3897 @strong{all} the functions in a program, like this:
3900 (@value{GDBP}) rbreak .
3903 @item rbreak @var{file}:@var{regex}
3904 If @code{rbreak} is called with a filename qualification, it limits
3905 the search for functions matching the given regular expression to the
3906 specified @var{file}. This can be used, for example, to set breakpoints on
3907 every function in a given file:
3910 (@value{GDBP}) rbreak file.c:.
3913 The colon separating the filename qualifier from the regex may
3914 optionally be surrounded by spaces.
3916 @kindex info breakpoints
3917 @cindex @code{$_} and @code{info breakpoints}
3918 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3919 @itemx info break @r{[}@var{list}@dots{}@r{]}
3920 Print a table of all breakpoints, watchpoints, and catchpoints set and
3921 not deleted. Optional argument @var{n} means print information only
3922 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3923 For each breakpoint, following columns are printed:
3926 @item Breakpoint Numbers
3928 Breakpoint, watchpoint, or catchpoint.
3930 Whether the breakpoint is marked to be disabled or deleted when hit.
3931 @item Enabled or Disabled
3932 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3933 that are not enabled.
3935 Where the breakpoint is in your program, as a memory address. For a
3936 pending breakpoint whose address is not yet known, this field will
3937 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3938 library that has the symbol or line referred by breakpoint is loaded.
3939 See below for details. A breakpoint with several locations will
3940 have @samp{<MULTIPLE>} in this field---see below for details.
3942 Where the breakpoint is in the source for your program, as a file and
3943 line number. For a pending breakpoint, the original string passed to
3944 the breakpoint command will be listed as it cannot be resolved until
3945 the appropriate shared library is loaded in the future.
3949 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3950 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3951 @value{GDBN} on the host's side. If it is ``target'', then the condition
3952 is evaluated by the target. The @code{info break} command shows
3953 the condition on the line following the affected breakpoint, together with
3954 its condition evaluation mode in between parentheses.
3956 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3957 allowed to have a condition specified for it. The condition is not parsed for
3958 validity until a shared library is loaded that allows the pending
3959 breakpoint to resolve to a valid location.
3962 @code{info break} with a breakpoint
3963 number @var{n} as argument lists only that breakpoint. The
3964 convenience variable @code{$_} and the default examining-address for
3965 the @code{x} command are set to the address of the last breakpoint
3966 listed (@pxref{Memory, ,Examining Memory}).
3969 @code{info break} displays a count of the number of times the breakpoint
3970 has been hit. This is especially useful in conjunction with the
3971 @code{ignore} command. You can ignore a large number of breakpoint
3972 hits, look at the breakpoint info to see how many times the breakpoint
3973 was hit, and then run again, ignoring one less than that number. This
3974 will get you quickly to the last hit of that breakpoint.
3977 For a breakpoints with an enable count (xref) greater than 1,
3978 @code{info break} also displays that count.
3982 @value{GDBN} allows you to set any number of breakpoints at the same place in
3983 your program. There is nothing silly or meaningless about this. When
3984 the breakpoints are conditional, this is even useful
3985 (@pxref{Conditions, ,Break Conditions}).
3987 @cindex multiple locations, breakpoints
3988 @cindex breakpoints, multiple locations
3989 It is possible that a breakpoint corresponds to several locations
3990 in your program. Examples of this situation are:
3994 Multiple functions in the program may have the same name.
3997 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3998 instances of the function body, used in different cases.
4001 For a C@t{++} template function, a given line in the function can
4002 correspond to any number of instantiations.
4005 For an inlined function, a given source line can correspond to
4006 several places where that function is inlined.
4009 In all those cases, @value{GDBN} will insert a breakpoint at all
4010 the relevant locations.
4012 A breakpoint with multiple locations is displayed in the breakpoint
4013 table using several rows---one header row, followed by one row for
4014 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4015 address column. The rows for individual locations contain the actual
4016 addresses for locations, and show the functions to which those
4017 locations belong. The number column for a location is of the form
4018 @var{breakpoint-number}.@var{location-number}.
4023 Num Type Disp Enb Address What
4024 1 breakpoint keep y <MULTIPLE>
4026 breakpoint already hit 1 time
4027 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4028 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4031 You cannot delete the individual locations from a breakpoint. However,
4032 each location can be individually enabled or disabled by passing
4033 @var{breakpoint-number}.@var{location-number} as argument to the
4034 @code{enable} and @code{disable} commands. It's also possible to
4035 @code{enable} and @code{disable} a range of @var{location-number}
4036 locations using a @var{breakpoint-number} and two @var{location-number}s,
4037 in increasing order, separated by a hyphen, like
4038 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4039 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4040 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4041 all of the locations that belong to that breakpoint.
4043 @cindex pending breakpoints
4044 It's quite common to have a breakpoint inside a shared library.
4045 Shared libraries can be loaded and unloaded explicitly,
4046 and possibly repeatedly, as the program is executed. To support
4047 this use case, @value{GDBN} updates breakpoint locations whenever
4048 any shared library is loaded or unloaded. Typically, you would
4049 set a breakpoint in a shared library at the beginning of your
4050 debugging session, when the library is not loaded, and when the
4051 symbols from the library are not available. When you try to set
4052 breakpoint, @value{GDBN} will ask you if you want to set
4053 a so called @dfn{pending breakpoint}---breakpoint whose address
4054 is not yet resolved.
4056 After the program is run, whenever a new shared library is loaded,
4057 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4058 shared library contains the symbol or line referred to by some
4059 pending breakpoint, that breakpoint is resolved and becomes an
4060 ordinary breakpoint. When a library is unloaded, all breakpoints
4061 that refer to its symbols or source lines become pending again.
4063 This logic works for breakpoints with multiple locations, too. For
4064 example, if you have a breakpoint in a C@t{++} template function, and
4065 a newly loaded shared library has an instantiation of that template,
4066 a new location is added to the list of locations for the breakpoint.
4068 Except for having unresolved address, pending breakpoints do not
4069 differ from regular breakpoints. You can set conditions or commands,
4070 enable and disable them and perform other breakpoint operations.
4072 @value{GDBN} provides some additional commands for controlling what
4073 happens when the @samp{break} command cannot resolve breakpoint
4074 address specification to an address:
4076 @kindex set breakpoint pending
4077 @kindex show breakpoint pending
4079 @item set breakpoint pending auto
4080 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4081 location, it queries you whether a pending breakpoint should be created.
4083 @item set breakpoint pending on
4084 This indicates that an unrecognized breakpoint location should automatically
4085 result in a pending breakpoint being created.
4087 @item set breakpoint pending off
4088 This indicates that pending breakpoints are not to be created. Any
4089 unrecognized breakpoint location results in an error. This setting does
4090 not affect any pending breakpoints previously created.
4092 @item show breakpoint pending
4093 Show the current behavior setting for creating pending breakpoints.
4096 The settings above only affect the @code{break} command and its
4097 variants. Once breakpoint is set, it will be automatically updated
4098 as shared libraries are loaded and unloaded.
4100 @cindex automatic hardware breakpoints
4101 For some targets, @value{GDBN} can automatically decide if hardware or
4102 software breakpoints should be used, depending on whether the
4103 breakpoint address is read-only or read-write. This applies to
4104 breakpoints set with the @code{break} command as well as to internal
4105 breakpoints set by commands like @code{next} and @code{finish}. For
4106 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4109 You can control this automatic behaviour with the following commands:
4111 @kindex set breakpoint auto-hw
4112 @kindex show breakpoint auto-hw
4114 @item set breakpoint auto-hw on
4115 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4116 will try to use the target memory map to decide if software or hardware
4117 breakpoint must be used.
4119 @item set breakpoint auto-hw off
4120 This indicates @value{GDBN} should not automatically select breakpoint
4121 type. If the target provides a memory map, @value{GDBN} will warn when
4122 trying to set software breakpoint at a read-only address.
4125 @value{GDBN} normally implements breakpoints by replacing the program code
4126 at the breakpoint address with a special instruction, which, when
4127 executed, given control to the debugger. By default, the program
4128 code is so modified only when the program is resumed. As soon as
4129 the program stops, @value{GDBN} restores the original instructions. This
4130 behaviour guards against leaving breakpoints inserted in the
4131 target should gdb abrubptly disconnect. However, with slow remote
4132 targets, inserting and removing breakpoint can reduce the performance.
4133 This behavior can be controlled with the following commands::
4135 @kindex set breakpoint always-inserted
4136 @kindex show breakpoint always-inserted
4138 @item set breakpoint always-inserted off
4139 All breakpoints, including newly added by the user, are inserted in
4140 the target only when the target is resumed. All breakpoints are
4141 removed from the target when it stops. This is the default mode.
4143 @item set breakpoint always-inserted on
4144 Causes all breakpoints to be inserted in the target at all times. If
4145 the user adds a new breakpoint, or changes an existing breakpoint, the
4146 breakpoints in the target are updated immediately. A breakpoint is
4147 removed from the target only when breakpoint itself is deleted.
4150 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4151 when a breakpoint breaks. If the condition is true, then the process being
4152 debugged stops, otherwise the process is resumed.
4154 If the target supports evaluating conditions on its end, @value{GDBN} may
4155 download the breakpoint, together with its conditions, to it.
4157 This feature can be controlled via the following commands:
4159 @kindex set breakpoint condition-evaluation
4160 @kindex show breakpoint condition-evaluation
4162 @item set breakpoint condition-evaluation host
4163 This option commands @value{GDBN} to evaluate the breakpoint
4164 conditions on the host's side. Unconditional breakpoints are sent to
4165 the target which in turn receives the triggers and reports them back to GDB
4166 for condition evaluation. This is the standard evaluation mode.
4168 @item set breakpoint condition-evaluation target
4169 This option commands @value{GDBN} to download breakpoint conditions
4170 to the target at the moment of their insertion. The target
4171 is responsible for evaluating the conditional expression and reporting
4172 breakpoint stop events back to @value{GDBN} whenever the condition
4173 is true. Due to limitations of target-side evaluation, some conditions
4174 cannot be evaluated there, e.g., conditions that depend on local data
4175 that is only known to the host. Examples include
4176 conditional expressions involving convenience variables, complex types
4177 that cannot be handled by the agent expression parser and expressions
4178 that are too long to be sent over to the target, specially when the
4179 target is a remote system. In these cases, the conditions will be
4180 evaluated by @value{GDBN}.
4182 @item set breakpoint condition-evaluation auto
4183 This is the default mode. If the target supports evaluating breakpoint
4184 conditions on its end, @value{GDBN} will download breakpoint conditions to
4185 the target (limitations mentioned previously apply). If the target does
4186 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4187 to evaluating all these conditions on the host's side.
4191 @cindex negative breakpoint numbers
4192 @cindex internal @value{GDBN} breakpoints
4193 @value{GDBN} itself sometimes sets breakpoints in your program for
4194 special purposes, such as proper handling of @code{longjmp} (in C
4195 programs). These internal breakpoints are assigned negative numbers,
4196 starting with @code{-1}; @samp{info breakpoints} does not display them.
4197 You can see these breakpoints with the @value{GDBN} maintenance command
4198 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4201 @node Set Watchpoints
4202 @subsection Setting Watchpoints
4204 @cindex setting watchpoints
4205 You can use a watchpoint to stop execution whenever the value of an
4206 expression changes, without having to predict a particular place where
4207 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4208 The expression may be as simple as the value of a single variable, or
4209 as complex as many variables combined by operators. Examples include:
4213 A reference to the value of a single variable.
4216 An address cast to an appropriate data type. For example,
4217 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4218 address (assuming an @code{int} occupies 4 bytes).
4221 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4222 expression can use any operators valid in the program's native
4223 language (@pxref{Languages}).
4226 You can set a watchpoint on an expression even if the expression can
4227 not be evaluated yet. For instance, you can set a watchpoint on
4228 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4229 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4230 the expression produces a valid value. If the expression becomes
4231 valid in some other way than changing a variable (e.g.@: if the memory
4232 pointed to by @samp{*global_ptr} becomes readable as the result of a
4233 @code{malloc} call), @value{GDBN} may not stop until the next time
4234 the expression changes.
4236 @cindex software watchpoints
4237 @cindex hardware watchpoints
4238 Depending on your system, watchpoints may be implemented in software or
4239 hardware. @value{GDBN} does software watchpointing by single-stepping your
4240 program and testing the variable's value each time, which is hundreds of
4241 times slower than normal execution. (But this may still be worth it, to
4242 catch errors where you have no clue what part of your program is the
4245 On some systems, such as most PowerPC or x86-based targets,
4246 @value{GDBN} includes support for hardware watchpoints, which do not
4247 slow down the running of your program.
4251 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4252 Set a watchpoint for an expression. @value{GDBN} will break when the
4253 expression @var{expr} is written into by the program and its value
4254 changes. The simplest (and the most popular) use of this command is
4255 to watch the value of a single variable:
4258 (@value{GDBP}) watch foo
4261 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4262 argument, @value{GDBN} breaks only when the thread identified by
4263 @var{thread-id} changes the value of @var{expr}. If any other threads
4264 change the value of @var{expr}, @value{GDBN} will not break. Note
4265 that watchpoints restricted to a single thread in this way only work
4266 with Hardware Watchpoints.
4268 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4269 (see below). The @code{-location} argument tells @value{GDBN} to
4270 instead watch the memory referred to by @var{expr}. In this case,
4271 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4272 and watch the memory at that address. The type of the result is used
4273 to determine the size of the watched memory. If the expression's
4274 result does not have an address, then @value{GDBN} will print an
4277 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4278 of masked watchpoints, if the current architecture supports this
4279 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4280 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4281 to an address to watch. The mask specifies that some bits of an address
4282 (the bits which are reset in the mask) should be ignored when matching
4283 the address accessed by the inferior against the watchpoint address.
4284 Thus, a masked watchpoint watches many addresses simultaneously---those
4285 addresses whose unmasked bits are identical to the unmasked bits in the
4286 watchpoint address. The @code{mask} argument implies @code{-location}.
4290 (@value{GDBP}) watch foo mask 0xffff00ff
4291 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4295 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4296 Set a watchpoint that will break when the value of @var{expr} is read
4300 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4301 Set a watchpoint that will break when @var{expr} is either read from
4302 or written into by the program.
4304 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4305 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4306 This command prints a list of watchpoints, using the same format as
4307 @code{info break} (@pxref{Set Breaks}).
4310 If you watch for a change in a numerically entered address you need to
4311 dereference it, as the address itself is just a constant number which will
4312 never change. @value{GDBN} refuses to create a watchpoint that watches
4313 a never-changing value:
4316 (@value{GDBP}) watch 0x600850
4317 Cannot watch constant value 0x600850.
4318 (@value{GDBP}) watch *(int *) 0x600850
4319 Watchpoint 1: *(int *) 6293584
4322 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4323 watchpoints execute very quickly, and the debugger reports a change in
4324 value at the exact instruction where the change occurs. If @value{GDBN}
4325 cannot set a hardware watchpoint, it sets a software watchpoint, which
4326 executes more slowly and reports the change in value at the next
4327 @emph{statement}, not the instruction, after the change occurs.
4329 @cindex use only software watchpoints
4330 You can force @value{GDBN} to use only software watchpoints with the
4331 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4332 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4333 the underlying system supports them. (Note that hardware-assisted
4334 watchpoints that were set @emph{before} setting
4335 @code{can-use-hw-watchpoints} to zero will still use the hardware
4336 mechanism of watching expression values.)
4339 @item set can-use-hw-watchpoints
4340 @kindex set can-use-hw-watchpoints
4341 Set whether or not to use hardware watchpoints.
4343 @item show can-use-hw-watchpoints
4344 @kindex show can-use-hw-watchpoints
4345 Show the current mode of using hardware watchpoints.
4348 For remote targets, you can restrict the number of hardware
4349 watchpoints @value{GDBN} will use, see @ref{set remote
4350 hardware-breakpoint-limit}.
4352 When you issue the @code{watch} command, @value{GDBN} reports
4355 Hardware watchpoint @var{num}: @var{expr}
4359 if it was able to set a hardware watchpoint.
4361 Currently, the @code{awatch} and @code{rwatch} commands can only set
4362 hardware watchpoints, because accesses to data that don't change the
4363 value of the watched expression cannot be detected without examining
4364 every instruction as it is being executed, and @value{GDBN} does not do
4365 that currently. If @value{GDBN} finds that it is unable to set a
4366 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4367 will print a message like this:
4370 Expression cannot be implemented with read/access watchpoint.
4373 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4374 data type of the watched expression is wider than what a hardware
4375 watchpoint on the target machine can handle. For example, some systems
4376 can only watch regions that are up to 4 bytes wide; on such systems you
4377 cannot set hardware watchpoints for an expression that yields a
4378 double-precision floating-point number (which is typically 8 bytes
4379 wide). As a work-around, it might be possible to break the large region
4380 into a series of smaller ones and watch them with separate watchpoints.
4382 If you set too many hardware watchpoints, @value{GDBN} might be unable
4383 to insert all of them when you resume the execution of your program.
4384 Since the precise number of active watchpoints is unknown until such
4385 time as the program is about to be resumed, @value{GDBN} might not be
4386 able to warn you about this when you set the watchpoints, and the
4387 warning will be printed only when the program is resumed:
4390 Hardware watchpoint @var{num}: Could not insert watchpoint
4394 If this happens, delete or disable some of the watchpoints.
4396 Watching complex expressions that reference many variables can also
4397 exhaust the resources available for hardware-assisted watchpoints.
4398 That's because @value{GDBN} needs to watch every variable in the
4399 expression with separately allocated resources.
4401 If you call a function interactively using @code{print} or @code{call},
4402 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4403 kind of breakpoint or the call completes.
4405 @value{GDBN} automatically deletes watchpoints that watch local
4406 (automatic) variables, or expressions that involve such variables, when
4407 they go out of scope, that is, when the execution leaves the block in
4408 which these variables were defined. In particular, when the program
4409 being debugged terminates, @emph{all} local variables go out of scope,
4410 and so only watchpoints that watch global variables remain set. If you
4411 rerun the program, you will need to set all such watchpoints again. One
4412 way of doing that would be to set a code breakpoint at the entry to the
4413 @code{main} function and when it breaks, set all the watchpoints.
4415 @cindex watchpoints and threads
4416 @cindex threads and watchpoints
4417 In multi-threaded programs, watchpoints will detect changes to the
4418 watched expression from every thread.
4421 @emph{Warning:} In multi-threaded programs, software watchpoints
4422 have only limited usefulness. If @value{GDBN} creates a software
4423 watchpoint, it can only watch the value of an expression @emph{in a
4424 single thread}. If you are confident that the expression can only
4425 change due to the current thread's activity (and if you are also
4426 confident that no other thread can become current), then you can use
4427 software watchpoints as usual. However, @value{GDBN} may not notice
4428 when a non-current thread's activity changes the expression. (Hardware
4429 watchpoints, in contrast, watch an expression in all threads.)
4432 @xref{set remote hardware-watchpoint-limit}.
4434 @node Set Catchpoints
4435 @subsection Setting Catchpoints
4436 @cindex catchpoints, setting
4437 @cindex exception handlers
4438 @cindex event handling
4440 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4441 kinds of program events, such as C@t{++} exceptions or the loading of a
4442 shared library. Use the @code{catch} command to set a catchpoint.
4446 @item catch @var{event}
4447 Stop when @var{event} occurs. The @var{event} can be any of the following:
4450 @item throw @r{[}@var{regexp}@r{]}
4451 @itemx rethrow @r{[}@var{regexp}@r{]}
4452 @itemx catch @r{[}@var{regexp}@r{]}
4454 @kindex catch rethrow
4456 @cindex stop on C@t{++} exceptions
4457 The throwing, re-throwing, or catching of a C@t{++} exception.
4459 If @var{regexp} is given, then only exceptions whose type matches the
4460 regular expression will be caught.
4462 @vindex $_exception@r{, convenience variable}
4463 The convenience variable @code{$_exception} is available at an
4464 exception-related catchpoint, on some systems. This holds the
4465 exception being thrown.
4467 There are currently some limitations to C@t{++} exception handling in
4472 The support for these commands is system-dependent. Currently, only
4473 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4477 The regular expression feature and the @code{$_exception} convenience
4478 variable rely on the presence of some SDT probes in @code{libstdc++}.
4479 If these probes are not present, then these features cannot be used.
4480 These probes were first available in the GCC 4.8 release, but whether
4481 or not they are available in your GCC also depends on how it was
4485 The @code{$_exception} convenience variable is only valid at the
4486 instruction at which an exception-related catchpoint is set.
4489 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4490 location in the system library which implements runtime exception
4491 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4492 (@pxref{Selection}) to get to your code.
4495 If you call a function interactively, @value{GDBN} normally returns
4496 control to you when the function has finished executing. If the call
4497 raises an exception, however, the call may bypass the mechanism that
4498 returns control to you and cause your program either to abort or to
4499 simply continue running until it hits a breakpoint, catches a signal
4500 that @value{GDBN} is listening for, or exits. This is the case even if
4501 you set a catchpoint for the exception; catchpoints on exceptions are
4502 disabled within interactive calls. @xref{Calling}, for information on
4503 controlling this with @code{set unwind-on-terminating-exception}.
4506 You cannot raise an exception interactively.
4509 You cannot install an exception handler interactively.
4513 @kindex catch exception
4514 @cindex Ada exception catching
4515 @cindex catch Ada exceptions
4516 An Ada exception being raised. If an exception name is specified
4517 at the end of the command (eg @code{catch exception Program_Error}),
4518 the debugger will stop only when this specific exception is raised.
4519 Otherwise, the debugger stops execution when any Ada exception is raised.
4521 When inserting an exception catchpoint on a user-defined exception whose
4522 name is identical to one of the exceptions defined by the language, the
4523 fully qualified name must be used as the exception name. Otherwise,
4524 @value{GDBN} will assume that it should stop on the pre-defined exception
4525 rather than the user-defined one. For instance, assuming an exception
4526 called @code{Constraint_Error} is defined in package @code{Pck}, then
4527 the command to use to catch such exceptions is @kbd{catch exception
4528 Pck.Constraint_Error}.
4531 @kindex catch handlers
4532 @cindex Ada exception handlers catching
4533 @cindex catch Ada exceptions when handled
4534 An Ada exception being handled. If an exception name is
4535 specified at the end of the command
4536 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4537 only when this specific exception is handled.
4538 Otherwise, the debugger stops execution when any Ada exception is handled.
4540 When inserting a handlers catchpoint on a user-defined
4541 exception whose name is identical to one of the exceptions
4542 defined by the language, the fully qualified name must be used
4543 as the exception name. Otherwise, @value{GDBN} will assume that it
4544 should stop on the pre-defined exception rather than the
4545 user-defined one. For instance, assuming an exception called
4546 @code{Constraint_Error} is defined in package @code{Pck}, then the
4547 command to use to catch such exceptions handling is
4548 @kbd{catch handlers Pck.Constraint_Error}.
4550 @item exception unhandled
4551 @kindex catch exception unhandled
4552 An exception that was raised but is not handled by the program.
4555 @kindex catch assert
4556 A failed Ada assertion.
4560 @cindex break on fork/exec
4561 A call to @code{exec}.
4563 @anchor{catch syscall}
4565 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4566 @kindex catch syscall
4567 @cindex break on a system call.
4568 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4569 syscall is a mechanism for application programs to request a service
4570 from the operating system (OS) or one of the OS system services.
4571 @value{GDBN} can catch some or all of the syscalls issued by the
4572 debuggee, and show the related information for each syscall. If no
4573 argument is specified, calls to and returns from all system calls
4576 @var{name} can be any system call name that is valid for the
4577 underlying OS. Just what syscalls are valid depends on the OS. On
4578 GNU and Unix systems, you can find the full list of valid syscall
4579 names on @file{/usr/include/asm/unistd.h}.
4581 @c For MS-Windows, the syscall names and the corresponding numbers
4582 @c can be found, e.g., on this URL:
4583 @c http://www.metasploit.com/users/opcode/syscalls.html
4584 @c but we don't support Windows syscalls yet.
4586 Normally, @value{GDBN} knows in advance which syscalls are valid for
4587 each OS, so you can use the @value{GDBN} command-line completion
4588 facilities (@pxref{Completion,, command completion}) to list the
4591 You may also specify the system call numerically. A syscall's
4592 number is the value passed to the OS's syscall dispatcher to
4593 identify the requested service. When you specify the syscall by its
4594 name, @value{GDBN} uses its database of syscalls to convert the name
4595 into the corresponding numeric code, but using the number directly
4596 may be useful if @value{GDBN}'s database does not have the complete
4597 list of syscalls on your system (e.g., because @value{GDBN} lags
4598 behind the OS upgrades).
4600 You may specify a group of related syscalls to be caught at once using
4601 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4602 instance, on some platforms @value{GDBN} allows you to catch all
4603 network related syscalls, by passing the argument @code{group:network}
4604 to @code{catch syscall}. Note that not all syscall groups are
4605 available in every system. You can use the command completion
4606 facilities (@pxref{Completion,, command completion}) to list the
4607 syscall groups available on your environment.
4609 The example below illustrates how this command works if you don't provide
4613 (@value{GDBP}) catch syscall
4614 Catchpoint 1 (syscall)
4616 Starting program: /tmp/catch-syscall
4618 Catchpoint 1 (call to syscall 'close'), \
4619 0xffffe424 in __kernel_vsyscall ()
4623 Catchpoint 1 (returned from syscall 'close'), \
4624 0xffffe424 in __kernel_vsyscall ()
4628 Here is an example of catching a system call by name:
4631 (@value{GDBP}) catch syscall chroot
4632 Catchpoint 1 (syscall 'chroot' [61])
4634 Starting program: /tmp/catch-syscall
4636 Catchpoint 1 (call to syscall 'chroot'), \
4637 0xffffe424 in __kernel_vsyscall ()
4641 Catchpoint 1 (returned from syscall 'chroot'), \
4642 0xffffe424 in __kernel_vsyscall ()
4646 An example of specifying a system call numerically. In the case
4647 below, the syscall number has a corresponding entry in the XML
4648 file, so @value{GDBN} finds its name and prints it:
4651 (@value{GDBP}) catch syscall 252
4652 Catchpoint 1 (syscall(s) 'exit_group')
4654 Starting program: /tmp/catch-syscall
4656 Catchpoint 1 (call to syscall 'exit_group'), \
4657 0xffffe424 in __kernel_vsyscall ()
4661 Program exited normally.
4665 Here is an example of catching a syscall group:
4668 (@value{GDBP}) catch syscall group:process
4669 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4670 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4671 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4673 Starting program: /tmp/catch-syscall
4675 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4676 from /lib64/ld-linux-x86-64.so.2
4682 However, there can be situations when there is no corresponding name
4683 in XML file for that syscall number. In this case, @value{GDBN} prints
4684 a warning message saying that it was not able to find the syscall name,
4685 but the catchpoint will be set anyway. See the example below:
4688 (@value{GDBP}) catch syscall 764
4689 warning: The number '764' does not represent a known syscall.
4690 Catchpoint 2 (syscall 764)
4694 If you configure @value{GDBN} using the @samp{--without-expat} option,
4695 it will not be able to display syscall names. Also, if your
4696 architecture does not have an XML file describing its system calls,
4697 you will not be able to see the syscall names. It is important to
4698 notice that these two features are used for accessing the syscall
4699 name database. In either case, you will see a warning like this:
4702 (@value{GDBP}) catch syscall
4703 warning: Could not open "syscalls/i386-linux.xml"
4704 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4705 GDB will not be able to display syscall names.
4706 Catchpoint 1 (syscall)
4710 Of course, the file name will change depending on your architecture and system.
4712 Still using the example above, you can also try to catch a syscall by its
4713 number. In this case, you would see something like:
4716 (@value{GDBP}) catch syscall 252
4717 Catchpoint 1 (syscall(s) 252)
4720 Again, in this case @value{GDBN} would not be able to display syscall's names.
4724 A call to @code{fork}.
4728 A call to @code{vfork}.
4730 @item load @r{[}regexp@r{]}
4731 @itemx unload @r{[}regexp@r{]}
4733 @kindex catch unload
4734 The loading or unloading of a shared library. If @var{regexp} is
4735 given, then the catchpoint will stop only if the regular expression
4736 matches one of the affected libraries.
4738 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4739 @kindex catch signal
4740 The delivery of a signal.
4742 With no arguments, this catchpoint will catch any signal that is not
4743 used internally by @value{GDBN}, specifically, all signals except
4744 @samp{SIGTRAP} and @samp{SIGINT}.
4746 With the argument @samp{all}, all signals, including those used by
4747 @value{GDBN}, will be caught. This argument cannot be used with other
4750 Otherwise, the arguments are a list of signal names as given to
4751 @code{handle} (@pxref{Signals}). Only signals specified in this list
4754 One reason that @code{catch signal} can be more useful than
4755 @code{handle} is that you can attach commands and conditions to the
4758 When a signal is caught by a catchpoint, the signal's @code{stop} and
4759 @code{print} settings, as specified by @code{handle}, are ignored.
4760 However, whether the signal is still delivered to the inferior depends
4761 on the @code{pass} setting; this can be changed in the catchpoint's
4766 @item tcatch @var{event}
4768 Set a catchpoint that is enabled only for one stop. The catchpoint is
4769 automatically deleted after the first time the event is caught.
4773 Use the @code{info break} command to list the current catchpoints.
4777 @subsection Deleting Breakpoints
4779 @cindex clearing breakpoints, watchpoints, catchpoints
4780 @cindex deleting breakpoints, watchpoints, catchpoints
4781 It is often necessary to eliminate a breakpoint, watchpoint, or
4782 catchpoint once it has done its job and you no longer want your program
4783 to stop there. This is called @dfn{deleting} the breakpoint. A
4784 breakpoint that has been deleted no longer exists; it is forgotten.
4786 With the @code{clear} command you can delete breakpoints according to
4787 where they are in your program. With the @code{delete} command you can
4788 delete individual breakpoints, watchpoints, or catchpoints by specifying
4789 their breakpoint numbers.
4791 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4792 automatically ignores breakpoints on the first instruction to be executed
4793 when you continue execution without changing the execution address.
4798 Delete any breakpoints at the next instruction to be executed in the
4799 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4800 the innermost frame is selected, this is a good way to delete a
4801 breakpoint where your program just stopped.
4803 @item clear @var{location}
4804 Delete any breakpoints set at the specified @var{location}.
4805 @xref{Specify Location}, for the various forms of @var{location}; the
4806 most useful ones are listed below:
4809 @item clear @var{function}
4810 @itemx clear @var{filename}:@var{function}
4811 Delete any breakpoints set at entry to the named @var{function}.
4813 @item clear @var{linenum}
4814 @itemx clear @var{filename}:@var{linenum}
4815 Delete any breakpoints set at or within the code of the specified
4816 @var{linenum} of the specified @var{filename}.
4819 @cindex delete breakpoints
4821 @kindex d @r{(@code{delete})}
4822 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4823 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4824 list specified as argument. If no argument is specified, delete all
4825 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4826 confirm off}). You can abbreviate this command as @code{d}.
4830 @subsection Disabling Breakpoints
4832 @cindex enable/disable a breakpoint
4833 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4834 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4835 it had been deleted, but remembers the information on the breakpoint so
4836 that you can @dfn{enable} it again later.
4838 You disable and enable breakpoints, watchpoints, and catchpoints with
4839 the @code{enable} and @code{disable} commands, optionally specifying
4840 one or more breakpoint numbers as arguments. Use @code{info break} to
4841 print a list of all breakpoints, watchpoints, and catchpoints if you
4842 do not know which numbers to use.
4844 Disabling and enabling a breakpoint that has multiple locations
4845 affects all of its locations.
4847 A breakpoint, watchpoint, or catchpoint can have any of several
4848 different states of enablement:
4852 Enabled. The breakpoint stops your program. A breakpoint set
4853 with the @code{break} command starts out in this state.
4855 Disabled. The breakpoint has no effect on your program.
4857 Enabled once. The breakpoint stops your program, but then becomes
4860 Enabled for a count. The breakpoint stops your program for the next
4861 N times, then becomes disabled.
4863 Enabled for deletion. The breakpoint stops your program, but
4864 immediately after it does so it is deleted permanently. A breakpoint
4865 set with the @code{tbreak} command starts out in this state.
4868 You can use the following commands to enable or disable breakpoints,
4869 watchpoints, and catchpoints:
4873 @kindex dis @r{(@code{disable})}
4874 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4875 Disable the specified breakpoints---or all breakpoints, if none are
4876 listed. A disabled breakpoint has no effect but is not forgotten. All
4877 options such as ignore-counts, conditions and commands are remembered in
4878 case the breakpoint is enabled again later. You may abbreviate
4879 @code{disable} as @code{dis}.
4882 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4883 Enable the specified breakpoints (or all defined breakpoints). They
4884 become effective once again in stopping your program.
4886 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4887 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4888 of these breakpoints immediately after stopping your program.
4890 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4891 Enable the specified breakpoints temporarily. @value{GDBN} records
4892 @var{count} with each of the specified breakpoints, and decrements a
4893 breakpoint's count when it is hit. When any count reaches 0,
4894 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4895 count (@pxref{Conditions, ,Break Conditions}), that will be
4896 decremented to 0 before @var{count} is affected.
4898 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4899 Enable the specified breakpoints to work once, then die. @value{GDBN}
4900 deletes any of these breakpoints as soon as your program stops there.
4901 Breakpoints set by the @code{tbreak} command start out in this state.
4904 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4905 @c confusing: tbreak is also initially enabled.
4906 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4907 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4908 subsequently, they become disabled or enabled only when you use one of
4909 the commands above. (The command @code{until} can set and delete a
4910 breakpoint of its own, but it does not change the state of your other
4911 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4915 @subsection Break Conditions
4916 @cindex conditional breakpoints
4917 @cindex breakpoint conditions
4919 @c FIXME what is scope of break condition expr? Context where wanted?
4920 @c in particular for a watchpoint?
4921 The simplest sort of breakpoint breaks every time your program reaches a
4922 specified place. You can also specify a @dfn{condition} for a
4923 breakpoint. A condition is just a Boolean expression in your
4924 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4925 a condition evaluates the expression each time your program reaches it,
4926 and your program stops only if the condition is @emph{true}.
4928 This is the converse of using assertions for program validation; in that
4929 situation, you want to stop when the assertion is violated---that is,
4930 when the condition is false. In C, if you want to test an assertion expressed
4931 by the condition @var{assert}, you should set the condition
4932 @samp{! @var{assert}} on the appropriate breakpoint.
4934 Conditions are also accepted for watchpoints; you may not need them,
4935 since a watchpoint is inspecting the value of an expression anyhow---but
4936 it might be simpler, say, to just set a watchpoint on a variable name,
4937 and specify a condition that tests whether the new value is an interesting
4940 Break conditions can have side effects, and may even call functions in
4941 your program. This can be useful, for example, to activate functions
4942 that log program progress, or to use your own print functions to
4943 format special data structures. The effects are completely predictable
4944 unless there is another enabled breakpoint at the same address. (In
4945 that case, @value{GDBN} might see the other breakpoint first and stop your
4946 program without checking the condition of this one.) Note that
4947 breakpoint commands are usually more convenient and flexible than break
4949 purpose of performing side effects when a breakpoint is reached
4950 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4952 Breakpoint conditions can also be evaluated on the target's side if
4953 the target supports it. Instead of evaluating the conditions locally,
4954 @value{GDBN} encodes the expression into an agent expression
4955 (@pxref{Agent Expressions}) suitable for execution on the target,
4956 independently of @value{GDBN}. Global variables become raw memory
4957 locations, locals become stack accesses, and so forth.
4959 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4960 when its condition evaluates to true. This mechanism may provide faster
4961 response times depending on the performance characteristics of the target
4962 since it does not need to keep @value{GDBN} informed about
4963 every breakpoint trigger, even those with false conditions.
4965 Break conditions can be specified when a breakpoint is set, by using
4966 @samp{if} in the arguments to the @code{break} command. @xref{Set
4967 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4968 with the @code{condition} command.
4970 You can also use the @code{if} keyword with the @code{watch} command.
4971 The @code{catch} command does not recognize the @code{if} keyword;
4972 @code{condition} is the only way to impose a further condition on a
4977 @item condition @var{bnum} @var{expression}
4978 Specify @var{expression} as the break condition for breakpoint,
4979 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4980 breakpoint @var{bnum} stops your program only if the value of
4981 @var{expression} is true (nonzero, in C). When you use
4982 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4983 syntactic correctness, and to determine whether symbols in it have
4984 referents in the context of your breakpoint. If @var{expression} uses
4985 symbols not referenced in the context of the breakpoint, @value{GDBN}
4986 prints an error message:
4989 No symbol "foo" in current context.
4994 not actually evaluate @var{expression} at the time the @code{condition}
4995 command (or a command that sets a breakpoint with a condition, like
4996 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4998 @item condition @var{bnum}
4999 Remove the condition from breakpoint number @var{bnum}. It becomes
5000 an ordinary unconditional breakpoint.
5003 @cindex ignore count (of breakpoint)
5004 A special case of a breakpoint condition is to stop only when the
5005 breakpoint has been reached a certain number of times. This is so
5006 useful that there is a special way to do it, using the @dfn{ignore
5007 count} of the breakpoint. Every breakpoint has an ignore count, which
5008 is an integer. Most of the time, the ignore count is zero, and
5009 therefore has no effect. But if your program reaches a breakpoint whose
5010 ignore count is positive, then instead of stopping, it just decrements
5011 the ignore count by one and continues. As a result, if the ignore count
5012 value is @var{n}, the breakpoint does not stop the next @var{n} times
5013 your program reaches it.
5017 @item ignore @var{bnum} @var{count}
5018 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5019 The next @var{count} times the breakpoint is reached, your program's
5020 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5023 To make the breakpoint stop the next time it is reached, specify
5026 When you use @code{continue} to resume execution of your program from a
5027 breakpoint, you can specify an ignore count directly as an argument to
5028 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5029 Stepping,,Continuing and Stepping}.
5031 If a breakpoint has a positive ignore count and a condition, the
5032 condition is not checked. Once the ignore count reaches zero,
5033 @value{GDBN} resumes checking the condition.
5035 You could achieve the effect of the ignore count with a condition such
5036 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5037 is decremented each time. @xref{Convenience Vars, ,Convenience
5041 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5044 @node Break Commands
5045 @subsection Breakpoint Command Lists
5047 @cindex breakpoint commands
5048 You can give any breakpoint (or watchpoint or catchpoint) a series of
5049 commands to execute when your program stops due to that breakpoint. For
5050 example, you might want to print the values of certain expressions, or
5051 enable other breakpoints.
5055 @kindex end@r{ (breakpoint commands)}
5056 @item commands @r{[}@var{list}@dots{}@r{]}
5057 @itemx @dots{} @var{command-list} @dots{}
5059 Specify a list of commands for the given breakpoints. The commands
5060 themselves appear on the following lines. Type a line containing just
5061 @code{end} to terminate the commands.
5063 To remove all commands from a breakpoint, type @code{commands} and
5064 follow it immediately with @code{end}; that is, give no commands.
5066 With no argument, @code{commands} refers to the last breakpoint,
5067 watchpoint, or catchpoint set (not to the breakpoint most recently
5068 encountered). If the most recent breakpoints were set with a single
5069 command, then the @code{commands} will apply to all the breakpoints
5070 set by that command. This applies to breakpoints set by
5071 @code{rbreak}, and also applies when a single @code{break} command
5072 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5076 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5077 disabled within a @var{command-list}.
5079 You can use breakpoint commands to start your program up again. Simply
5080 use the @code{continue} command, or @code{step}, or any other command
5081 that resumes execution.
5083 Any other commands in the command list, after a command that resumes
5084 execution, are ignored. This is because any time you resume execution
5085 (even with a simple @code{next} or @code{step}), you may encounter
5086 another breakpoint---which could have its own command list, leading to
5087 ambiguities about which list to execute.
5090 If the first command you specify in a command list is @code{silent}, the
5091 usual message about stopping at a breakpoint is not printed. This may
5092 be desirable for breakpoints that are to print a specific message and
5093 then continue. If none of the remaining commands print anything, you
5094 see no sign that the breakpoint was reached. @code{silent} is
5095 meaningful only at the beginning of a breakpoint command list.
5097 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5098 print precisely controlled output, and are often useful in silent
5099 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5101 For example, here is how you could use breakpoint commands to print the
5102 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5108 printf "x is %d\n",x
5113 One application for breakpoint commands is to compensate for one bug so
5114 you can test for another. Put a breakpoint just after the erroneous line
5115 of code, give it a condition to detect the case in which something
5116 erroneous has been done, and give it commands to assign correct values
5117 to any variables that need them. End with the @code{continue} command
5118 so that your program does not stop, and start with the @code{silent}
5119 command so that no output is produced. Here is an example:
5130 @node Dynamic Printf
5131 @subsection Dynamic Printf
5133 @cindex dynamic printf
5135 The dynamic printf command @code{dprintf} combines a breakpoint with
5136 formatted printing of your program's data to give you the effect of
5137 inserting @code{printf} calls into your program on-the-fly, without
5138 having to recompile it.
5140 In its most basic form, the output goes to the GDB console. However,
5141 you can set the variable @code{dprintf-style} for alternate handling.
5142 For instance, you can ask to format the output by calling your
5143 program's @code{printf} function. This has the advantage that the
5144 characters go to the program's output device, so they can recorded in
5145 redirects to files and so forth.
5147 If you are doing remote debugging with a stub or agent, you can also
5148 ask to have the printf handled by the remote agent. In addition to
5149 ensuring that the output goes to the remote program's device along
5150 with any other output the program might produce, you can also ask that
5151 the dprintf remain active even after disconnecting from the remote
5152 target. Using the stub/agent is also more efficient, as it can do
5153 everything without needing to communicate with @value{GDBN}.
5157 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5158 Whenever execution reaches @var{location}, print the values of one or
5159 more @var{expressions} under the control of the string @var{template}.
5160 To print several values, separate them with commas.
5162 @item set dprintf-style @var{style}
5163 Set the dprintf output to be handled in one of several different
5164 styles enumerated below. A change of style affects all existing
5165 dynamic printfs immediately. (If you need individual control over the
5166 print commands, simply define normal breakpoints with
5167 explicitly-supplied command lists.)
5171 @kindex dprintf-style gdb
5172 Handle the output using the @value{GDBN} @code{printf} command.
5175 @kindex dprintf-style call
5176 Handle the output by calling a function in your program (normally
5180 @kindex dprintf-style agent
5181 Have the remote debugging agent (such as @code{gdbserver}) handle
5182 the output itself. This style is only available for agents that
5183 support running commands on the target.
5186 @item set dprintf-function @var{function}
5187 Set the function to call if the dprintf style is @code{call}. By
5188 default its value is @code{printf}. You may set it to any expression.
5189 that @value{GDBN} can evaluate to a function, as per the @code{call}
5192 @item set dprintf-channel @var{channel}
5193 Set a ``channel'' for dprintf. If set to a non-empty value,
5194 @value{GDBN} will evaluate it as an expression and pass the result as
5195 a first argument to the @code{dprintf-function}, in the manner of
5196 @code{fprintf} and similar functions. Otherwise, the dprintf format
5197 string will be the first argument, in the manner of @code{printf}.
5199 As an example, if you wanted @code{dprintf} output to go to a logfile
5200 that is a standard I/O stream assigned to the variable @code{mylog},
5201 you could do the following:
5204 (gdb) set dprintf-style call
5205 (gdb) set dprintf-function fprintf
5206 (gdb) set dprintf-channel mylog
5207 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5208 Dprintf 1 at 0x123456: file main.c, line 25.
5210 1 dprintf keep y 0x00123456 in main at main.c:25
5211 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5216 Note that the @code{info break} displays the dynamic printf commands
5217 as normal breakpoint commands; you can thus easily see the effect of
5218 the variable settings.
5220 @item set disconnected-dprintf on
5221 @itemx set disconnected-dprintf off
5222 @kindex set disconnected-dprintf
5223 Choose whether @code{dprintf} commands should continue to run if
5224 @value{GDBN} has disconnected from the target. This only applies
5225 if the @code{dprintf-style} is @code{agent}.
5227 @item show disconnected-dprintf off
5228 @kindex show disconnected-dprintf
5229 Show the current choice for disconnected @code{dprintf}.
5233 @value{GDBN} does not check the validity of function and channel,
5234 relying on you to supply values that are meaningful for the contexts
5235 in which they are being used. For instance, the function and channel
5236 may be the values of local variables, but if that is the case, then
5237 all enabled dynamic prints must be at locations within the scope of
5238 those locals. If evaluation fails, @value{GDBN} will report an error.
5240 @node Save Breakpoints
5241 @subsection How to save breakpoints to a file
5243 To save breakpoint definitions to a file use the @w{@code{save
5244 breakpoints}} command.
5247 @kindex save breakpoints
5248 @cindex save breakpoints to a file for future sessions
5249 @item save breakpoints [@var{filename}]
5250 This command saves all current breakpoint definitions together with
5251 their commands and ignore counts, into a file @file{@var{filename}}
5252 suitable for use in a later debugging session. This includes all
5253 types of breakpoints (breakpoints, watchpoints, catchpoints,
5254 tracepoints). To read the saved breakpoint definitions, use the
5255 @code{source} command (@pxref{Command Files}). Note that watchpoints
5256 with expressions involving local variables may fail to be recreated
5257 because it may not be possible to access the context where the
5258 watchpoint is valid anymore. Because the saved breakpoint definitions
5259 are simply a sequence of @value{GDBN} commands that recreate the
5260 breakpoints, you can edit the file in your favorite editing program,
5261 and remove the breakpoint definitions you're not interested in, or
5262 that can no longer be recreated.
5265 @node Static Probe Points
5266 @subsection Static Probe Points
5268 @cindex static probe point, SystemTap
5269 @cindex static probe point, DTrace
5270 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5271 for Statically Defined Tracing, and the probes are designed to have a tiny
5272 runtime code and data footprint, and no dynamic relocations.
5274 Currently, the following types of probes are supported on
5275 ELF-compatible systems:
5279 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5280 @acronym{SDT} probes@footnote{See
5281 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5282 for more information on how to add @code{SystemTap} @acronym{SDT}
5283 probes in your applications.}. @code{SystemTap} probes are usable
5284 from assembly, C and C@t{++} languages@footnote{See
5285 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5286 for a good reference on how the @acronym{SDT} probes are implemented.}.
5288 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5289 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5293 @cindex semaphores on static probe points
5294 Some @code{SystemTap} probes have an associated semaphore variable;
5295 for instance, this happens automatically if you defined your probe
5296 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5297 @value{GDBN} will automatically enable it when you specify a
5298 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5299 breakpoint at a probe's location by some other method (e.g.,
5300 @code{break file:line}), then @value{GDBN} will not automatically set
5301 the semaphore. @code{DTrace} probes do not support semaphores.
5303 You can examine the available static static probes using @code{info
5304 probes}, with optional arguments:
5308 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5309 If given, @var{type} is either @code{stap} for listing
5310 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5311 probes. If omitted all probes are listed regardless of their types.
5313 If given, @var{provider} is a regular expression used to match against provider
5314 names when selecting which probes to list. If omitted, probes by all
5315 probes from all providers are listed.
5317 If given, @var{name} is a regular expression to match against probe names
5318 when selecting which probes to list. If omitted, probe names are not
5319 considered when deciding whether to display them.
5321 If given, @var{objfile} is a regular expression used to select which
5322 object files (executable or shared libraries) to examine. If not
5323 given, all object files are considered.
5325 @item info probes all
5326 List the available static probes, from all types.
5329 @cindex enabling and disabling probes
5330 Some probe points can be enabled and/or disabled. The effect of
5331 enabling or disabling a probe depends on the type of probe being
5332 handled. Some @code{DTrace} probes can be enabled or
5333 disabled, but @code{SystemTap} probes cannot be disabled.
5335 You can enable (or disable) one or more probes using the following
5336 commands, with optional arguments:
5339 @kindex enable probes
5340 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5341 If given, @var{provider} is a regular expression used to match against
5342 provider names when selecting which probes to enable. If omitted,
5343 all probes from all providers are enabled.
5345 If given, @var{name} is a regular expression to match against probe
5346 names when selecting which probes to enable. If omitted, probe names
5347 are not considered when deciding whether to enable them.
5349 If given, @var{objfile} is a regular expression used to select which
5350 object files (executable or shared libraries) to examine. If not
5351 given, all object files are considered.
5353 @kindex disable probes
5354 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5355 See the @code{enable probes} command above for a description of the
5356 optional arguments accepted by this command.
5359 @vindex $_probe_arg@r{, convenience variable}
5360 A probe may specify up to twelve arguments. These are available at the
5361 point at which the probe is defined---that is, when the current PC is
5362 at the probe's location. The arguments are available using the
5363 convenience variables (@pxref{Convenience Vars})
5364 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5365 probes each probe argument is an integer of the appropriate size;
5366 types are not preserved. In @code{DTrace} probes types are preserved
5367 provided that they are recognized as such by @value{GDBN}; otherwise
5368 the value of the probe argument will be a long integer. The
5369 convenience variable @code{$_probe_argc} holds the number of arguments
5370 at the current probe point.
5372 These variables are always available, but attempts to access them at
5373 any location other than a probe point will cause @value{GDBN} to give
5377 @c @ifclear BARETARGET
5378 @node Error in Breakpoints
5379 @subsection ``Cannot insert breakpoints''
5381 If you request too many active hardware-assisted breakpoints and
5382 watchpoints, you will see this error message:
5384 @c FIXME: the precise wording of this message may change; the relevant
5385 @c source change is not committed yet (Sep 3, 1999).
5387 Stopped; cannot insert breakpoints.
5388 You may have requested too many hardware breakpoints and watchpoints.
5392 This message is printed when you attempt to resume the program, since
5393 only then @value{GDBN} knows exactly how many hardware breakpoints and
5394 watchpoints it needs to insert.
5396 When this message is printed, you need to disable or remove some of the
5397 hardware-assisted breakpoints and watchpoints, and then continue.
5399 @node Breakpoint-related Warnings
5400 @subsection ``Breakpoint address adjusted...''
5401 @cindex breakpoint address adjusted
5403 Some processor architectures place constraints on the addresses at
5404 which breakpoints may be placed. For architectures thus constrained,
5405 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5406 with the constraints dictated by the architecture.
5408 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5409 a VLIW architecture in which a number of RISC-like instructions may be
5410 bundled together for parallel execution. The FR-V architecture
5411 constrains the location of a breakpoint instruction within such a
5412 bundle to the instruction with the lowest address. @value{GDBN}
5413 honors this constraint by adjusting a breakpoint's address to the
5414 first in the bundle.
5416 It is not uncommon for optimized code to have bundles which contain
5417 instructions from different source statements, thus it may happen that
5418 a breakpoint's address will be adjusted from one source statement to
5419 another. Since this adjustment may significantly alter @value{GDBN}'s
5420 breakpoint related behavior from what the user expects, a warning is
5421 printed when the breakpoint is first set and also when the breakpoint
5424 A warning like the one below is printed when setting a breakpoint
5425 that's been subject to address adjustment:
5428 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5431 Such warnings are printed both for user settable and @value{GDBN}'s
5432 internal breakpoints. If you see one of these warnings, you should
5433 verify that a breakpoint set at the adjusted address will have the
5434 desired affect. If not, the breakpoint in question may be removed and
5435 other breakpoints may be set which will have the desired behavior.
5436 E.g., it may be sufficient to place the breakpoint at a later
5437 instruction. A conditional breakpoint may also be useful in some
5438 cases to prevent the breakpoint from triggering too often.
5440 @value{GDBN} will also issue a warning when stopping at one of these
5441 adjusted breakpoints:
5444 warning: Breakpoint 1 address previously adjusted from 0x00010414
5448 When this warning is encountered, it may be too late to take remedial
5449 action except in cases where the breakpoint is hit earlier or more
5450 frequently than expected.
5452 @node Continuing and Stepping
5453 @section Continuing and Stepping
5457 @cindex resuming execution
5458 @dfn{Continuing} means resuming program execution until your program
5459 completes normally. In contrast, @dfn{stepping} means executing just
5460 one more ``step'' of your program, where ``step'' may mean either one
5461 line of source code, or one machine instruction (depending on what
5462 particular command you use). Either when continuing or when stepping,
5463 your program may stop even sooner, due to a breakpoint or a signal. (If
5464 it stops due to a signal, you may want to use @code{handle}, or use
5465 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5466 or you may step into the signal's handler (@pxref{stepping and signal
5471 @kindex c @r{(@code{continue})}
5472 @kindex fg @r{(resume foreground execution)}
5473 @item continue @r{[}@var{ignore-count}@r{]}
5474 @itemx c @r{[}@var{ignore-count}@r{]}
5475 @itemx fg @r{[}@var{ignore-count}@r{]}
5476 Resume program execution, at the address where your program last stopped;
5477 any breakpoints set at that address are bypassed. The optional argument
5478 @var{ignore-count} allows you to specify a further number of times to
5479 ignore a breakpoint at this location; its effect is like that of
5480 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5482 The argument @var{ignore-count} is meaningful only when your program
5483 stopped due to a breakpoint. At other times, the argument to
5484 @code{continue} is ignored.
5486 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5487 debugged program is deemed to be the foreground program) are provided
5488 purely for convenience, and have exactly the same behavior as
5492 To resume execution at a different place, you can use @code{return}
5493 (@pxref{Returning, ,Returning from a Function}) to go back to the
5494 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5495 Different Address}) to go to an arbitrary location in your program.
5497 A typical technique for using stepping is to set a breakpoint
5498 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5499 beginning of the function or the section of your program where a problem
5500 is believed to lie, run your program until it stops at that breakpoint,
5501 and then step through the suspect area, examining the variables that are
5502 interesting, until you see the problem happen.
5506 @kindex s @r{(@code{step})}
5508 Continue running your program until control reaches a different source
5509 line, then stop it and return control to @value{GDBN}. This command is
5510 abbreviated @code{s}.
5513 @c "without debugging information" is imprecise; actually "without line
5514 @c numbers in the debugging information". (gcc -g1 has debugging info but
5515 @c not line numbers). But it seems complex to try to make that
5516 @c distinction here.
5517 @emph{Warning:} If you use the @code{step} command while control is
5518 within a function that was compiled without debugging information,
5519 execution proceeds until control reaches a function that does have
5520 debugging information. Likewise, it will not step into a function which
5521 is compiled without debugging information. To step through functions
5522 without debugging information, use the @code{stepi} command, described
5526 The @code{step} command only stops at the first instruction of a source
5527 line. This prevents the multiple stops that could otherwise occur in
5528 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5529 to stop if a function that has debugging information is called within
5530 the line. In other words, @code{step} @emph{steps inside} any functions
5531 called within the line.
5533 Also, the @code{step} command only enters a function if there is line
5534 number information for the function. Otherwise it acts like the
5535 @code{next} command. This avoids problems when using @code{cc -gl}
5536 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5537 was any debugging information about the routine.
5539 @item step @var{count}
5540 Continue running as in @code{step}, but do so @var{count} times. If a
5541 breakpoint is reached, or a signal not related to stepping occurs before
5542 @var{count} steps, stepping stops right away.
5545 @kindex n @r{(@code{next})}
5546 @item next @r{[}@var{count}@r{]}
5547 Continue to the next source line in the current (innermost) stack frame.
5548 This is similar to @code{step}, but function calls that appear within
5549 the line of code are executed without stopping. Execution stops when
5550 control reaches a different line of code at the original stack level
5551 that was executing when you gave the @code{next} command. This command
5552 is abbreviated @code{n}.
5554 An argument @var{count} is a repeat count, as for @code{step}.
5557 @c FIX ME!! Do we delete this, or is there a way it fits in with
5558 @c the following paragraph? --- Vctoria
5560 @c @code{next} within a function that lacks debugging information acts like
5561 @c @code{step}, but any function calls appearing within the code of the
5562 @c function are executed without stopping.
5564 The @code{next} command only stops at the first instruction of a
5565 source line. This prevents multiple stops that could otherwise occur in
5566 @code{switch} statements, @code{for} loops, etc.
5568 @kindex set step-mode
5570 @cindex functions without line info, and stepping
5571 @cindex stepping into functions with no line info
5572 @itemx set step-mode on
5573 The @code{set step-mode on} command causes the @code{step} command to
5574 stop at the first instruction of a function which contains no debug line
5575 information rather than stepping over it.
5577 This is useful in cases where you may be interested in inspecting the
5578 machine instructions of a function which has no symbolic info and do not
5579 want @value{GDBN} to automatically skip over this function.
5581 @item set step-mode off
5582 Causes the @code{step} command to step over any functions which contains no
5583 debug information. This is the default.
5585 @item show step-mode
5586 Show whether @value{GDBN} will stop in or step over functions without
5587 source line debug information.
5590 @kindex fin @r{(@code{finish})}
5592 Continue running until just after function in the selected stack frame
5593 returns. Print the returned value (if any). This command can be
5594 abbreviated as @code{fin}.
5596 Contrast this with the @code{return} command (@pxref{Returning,
5597 ,Returning from a Function}).
5600 @kindex u @r{(@code{until})}
5601 @cindex run until specified location
5604 Continue running until a source line past the current line, in the
5605 current stack frame, is reached. This command is used to avoid single
5606 stepping through a loop more than once. It is like the @code{next}
5607 command, except that when @code{until} encounters a jump, it
5608 automatically continues execution until the program counter is greater
5609 than the address of the jump.
5611 This means that when you reach the end of a loop after single stepping
5612 though it, @code{until} makes your program continue execution until it
5613 exits the loop. In contrast, a @code{next} command at the end of a loop
5614 simply steps back to the beginning of the loop, which forces you to step
5615 through the next iteration.
5617 @code{until} always stops your program if it attempts to exit the current
5620 @code{until} may produce somewhat counterintuitive results if the order
5621 of machine code does not match the order of the source lines. For
5622 example, in the following excerpt from a debugging session, the @code{f}
5623 (@code{frame}) command shows that execution is stopped at line
5624 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5628 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5630 (@value{GDBP}) until
5631 195 for ( ; argc > 0; NEXTARG) @{
5634 This happened because, for execution efficiency, the compiler had
5635 generated code for the loop closure test at the end, rather than the
5636 start, of the loop---even though the test in a C @code{for}-loop is
5637 written before the body of the loop. The @code{until} command appeared
5638 to step back to the beginning of the loop when it advanced to this
5639 expression; however, it has not really gone to an earlier
5640 statement---not in terms of the actual machine code.
5642 @code{until} with no argument works by means of single
5643 instruction stepping, and hence is slower than @code{until} with an
5646 @item until @var{location}
5647 @itemx u @var{location}
5648 Continue running your program until either the specified @var{location} is
5649 reached, or the current stack frame returns. The location is any of
5650 the forms described in @ref{Specify Location}.
5651 This form of the command uses temporary breakpoints, and
5652 hence is quicker than @code{until} without an argument. The specified
5653 location is actually reached only if it is in the current frame. This
5654 implies that @code{until} can be used to skip over recursive function
5655 invocations. For instance in the code below, if the current location is
5656 line @code{96}, issuing @code{until 99} will execute the program up to
5657 line @code{99} in the same invocation of factorial, i.e., after the inner
5658 invocations have returned.
5661 94 int factorial (int value)
5663 96 if (value > 1) @{
5664 97 value *= factorial (value - 1);
5671 @kindex advance @var{location}
5672 @item advance @var{location}
5673 Continue running the program up to the given @var{location}. An argument is
5674 required, which should be of one of the forms described in
5675 @ref{Specify Location}.
5676 Execution will also stop upon exit from the current stack
5677 frame. This command is similar to @code{until}, but @code{advance} will
5678 not skip over recursive function calls, and the target location doesn't
5679 have to be in the same frame as the current one.
5683 @kindex si @r{(@code{stepi})}
5685 @itemx stepi @var{arg}
5687 Execute one machine instruction, then stop and return to the debugger.
5689 It is often useful to do @samp{display/i $pc} when stepping by machine
5690 instructions. This makes @value{GDBN} automatically display the next
5691 instruction to be executed, each time your program stops. @xref{Auto
5692 Display,, Automatic Display}.
5694 An argument is a repeat count, as in @code{step}.
5698 @kindex ni @r{(@code{nexti})}
5700 @itemx nexti @var{arg}
5702 Execute one machine instruction, but if it is a function call,
5703 proceed until the function returns.
5705 An argument is a repeat count, as in @code{next}.
5709 @anchor{range stepping}
5710 @cindex range stepping
5711 @cindex target-assisted range stepping
5712 By default, and if available, @value{GDBN} makes use of
5713 target-assisted @dfn{range stepping}. In other words, whenever you
5714 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5715 tells the target to step the corresponding range of instruction
5716 addresses instead of issuing multiple single-steps. This speeds up
5717 line stepping, particularly for remote targets. Ideally, there should
5718 be no reason you would want to turn range stepping off. However, it's
5719 possible that a bug in the debug info, a bug in the remote stub (for
5720 remote targets), or even a bug in @value{GDBN} could make line
5721 stepping behave incorrectly when target-assisted range stepping is
5722 enabled. You can use the following command to turn off range stepping
5726 @kindex set range-stepping
5727 @kindex show range-stepping
5728 @item set range-stepping
5729 @itemx show range-stepping
5730 Control whether range stepping is enabled.
5732 If @code{on}, and the target supports it, @value{GDBN} tells the
5733 target to step a range of addresses itself, instead of issuing
5734 multiple single-steps. If @code{off}, @value{GDBN} always issues
5735 single-steps, even if range stepping is supported by the target. The
5736 default is @code{on}.
5740 @node Skipping Over Functions and Files
5741 @section Skipping Over Functions and Files
5742 @cindex skipping over functions and files
5744 The program you are debugging may contain some functions which are
5745 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5746 skip a function, all functions in a file or a particular function in
5747 a particular file when stepping.
5749 For example, consider the following C function:
5760 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5761 are not interested in stepping through @code{boring}. If you run @code{step}
5762 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5763 step over both @code{foo} and @code{boring}!
5765 One solution is to @code{step} into @code{boring} and use the @code{finish}
5766 command to immediately exit it. But this can become tedious if @code{boring}
5767 is called from many places.
5769 A more flexible solution is to execute @kbd{skip boring}. This instructs
5770 @value{GDBN} never to step into @code{boring}. Now when you execute
5771 @code{step} at line 103, you'll step over @code{boring} and directly into
5774 Functions may be skipped by providing either a function name, linespec
5775 (@pxref{Specify Location}), regular expression that matches the function's
5776 name, file name or a @code{glob}-style pattern that matches the file name.
5778 On Posix systems the form of the regular expression is
5779 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5780 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5781 expression is whatever is provided by the @code{regcomp} function of
5782 the underlying system.
5783 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5784 description of @code{glob}-style patterns.
5788 @item skip @r{[}@var{options}@r{]}
5789 The basic form of the @code{skip} command takes zero or more options
5790 that specify what to skip.
5791 The @var{options} argument is any useful combination of the following:
5794 @item -file @var{file}
5795 @itemx -fi @var{file}
5796 Functions in @var{file} will be skipped over when stepping.
5798 @item -gfile @var{file-glob-pattern}
5799 @itemx -gfi @var{file-glob-pattern}
5800 @cindex skipping over files via glob-style patterns
5801 Functions in files matching @var{file-glob-pattern} will be skipped
5805 (gdb) skip -gfi utils/*.c
5808 @item -function @var{linespec}
5809 @itemx -fu @var{linespec}
5810 Functions named by @var{linespec} or the function containing the line
5811 named by @var{linespec} will be skipped over when stepping.
5812 @xref{Specify Location}.
5814 @item -rfunction @var{regexp}
5815 @itemx -rfu @var{regexp}
5816 @cindex skipping over functions via regular expressions
5817 Functions whose name matches @var{regexp} will be skipped over when stepping.
5819 This form is useful for complex function names.
5820 For example, there is generally no need to step into C@t{++} @code{std::string}
5821 constructors or destructors. Plus with C@t{++} templates it can be hard to
5822 write out the full name of the function, and often it doesn't matter what
5823 the template arguments are. Specifying the function to be skipped as a
5824 regular expression makes this easier.
5827 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5830 If you want to skip every templated C@t{++} constructor and destructor
5831 in the @code{std} namespace you can do:
5834 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5838 If no options are specified, the function you're currently debugging
5841 @kindex skip function
5842 @item skip function @r{[}@var{linespec}@r{]}
5843 After running this command, the function named by @var{linespec} or the
5844 function containing the line named by @var{linespec} will be skipped over when
5845 stepping. @xref{Specify Location}.
5847 If you do not specify @var{linespec}, the function you're currently debugging
5850 (If you have a function called @code{file} that you want to skip, use
5851 @kbd{skip function file}.)
5854 @item skip file @r{[}@var{filename}@r{]}
5855 After running this command, any function whose source lives in @var{filename}
5856 will be skipped over when stepping.
5859 (gdb) skip file boring.c
5860 File boring.c will be skipped when stepping.
5863 If you do not specify @var{filename}, functions whose source lives in the file
5864 you're currently debugging will be skipped.
5867 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5868 These are the commands for managing your list of skips:
5872 @item info skip @r{[}@var{range}@r{]}
5873 Print details about the specified skip(s). If @var{range} is not specified,
5874 print a table with details about all functions and files marked for skipping.
5875 @code{info skip} prints the following information about each skip:
5879 A number identifying this skip.
5880 @item Enabled or Disabled
5881 Enabled skips are marked with @samp{y}.
5882 Disabled skips are marked with @samp{n}.
5884 If the file name is a @samp{glob} pattern this is @samp{y}.
5885 Otherwise it is @samp{n}.
5887 The name or @samp{glob} pattern of the file to be skipped.
5888 If no file is specified this is @samp{<none>}.
5890 If the function name is a @samp{regular expression} this is @samp{y}.
5891 Otherwise it is @samp{n}.
5893 The name or regular expression of the function to skip.
5894 If no function is specified this is @samp{<none>}.
5898 @item skip delete @r{[}@var{range}@r{]}
5899 Delete the specified skip(s). If @var{range} is not specified, delete all
5903 @item skip enable @r{[}@var{range}@r{]}
5904 Enable the specified skip(s). If @var{range} is not specified, enable all
5907 @kindex skip disable
5908 @item skip disable @r{[}@var{range}@r{]}
5909 Disable the specified skip(s). If @var{range} is not specified, disable all
5912 @kindex set debug skip
5913 @item set debug skip @r{[}on|off@r{]}
5914 Set whether to print the debug output about skipping files and functions.
5916 @kindex show debug skip
5917 @item show debug skip
5918 Show whether the debug output about skipping files and functions is printed.
5926 A signal is an asynchronous event that can happen in a program. The
5927 operating system defines the possible kinds of signals, and gives each
5928 kind a name and a number. For example, in Unix @code{SIGINT} is the
5929 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5930 @code{SIGSEGV} is the signal a program gets from referencing a place in
5931 memory far away from all the areas in use; @code{SIGALRM} occurs when
5932 the alarm clock timer goes off (which happens only if your program has
5933 requested an alarm).
5935 @cindex fatal signals
5936 Some signals, including @code{SIGALRM}, are a normal part of the
5937 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5938 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5939 program has not specified in advance some other way to handle the signal.
5940 @code{SIGINT} does not indicate an error in your program, but it is normally
5941 fatal so it can carry out the purpose of the interrupt: to kill the program.
5943 @value{GDBN} has the ability to detect any occurrence of a signal in your
5944 program. You can tell @value{GDBN} in advance what to do for each kind of
5947 @cindex handling signals
5948 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5949 @code{SIGALRM} be silently passed to your program
5950 (so as not to interfere with their role in the program's functioning)
5951 but to stop your program immediately whenever an error signal happens.
5952 You can change these settings with the @code{handle} command.
5955 @kindex info signals
5959 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5960 handle each one. You can use this to see the signal numbers of all
5961 the defined types of signals.
5963 @item info signals @var{sig}
5964 Similar, but print information only about the specified signal number.
5966 @code{info handle} is an alias for @code{info signals}.
5968 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5969 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5970 for details about this command.
5973 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5974 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5975 can be the number of a signal or its name (with or without the
5976 @samp{SIG} at the beginning); a list of signal numbers of the form
5977 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5978 known signals. Optional arguments @var{keywords}, described below,
5979 say what change to make.
5983 The keywords allowed by the @code{handle} command can be abbreviated.
5984 Their full names are:
5988 @value{GDBN} should not stop your program when this signal happens. It may
5989 still print a message telling you that the signal has come in.
5992 @value{GDBN} should stop your program when this signal happens. This implies
5993 the @code{print} keyword as well.
5996 @value{GDBN} should print a message when this signal happens.
5999 @value{GDBN} should not mention the occurrence of the signal at all. This
6000 implies the @code{nostop} keyword as well.
6004 @value{GDBN} should allow your program to see this signal; your program
6005 can handle the signal, or else it may terminate if the signal is fatal
6006 and not handled. @code{pass} and @code{noignore} are synonyms.
6010 @value{GDBN} should not allow your program to see this signal.
6011 @code{nopass} and @code{ignore} are synonyms.
6015 When a signal stops your program, the signal is not visible to the
6017 continue. Your program sees the signal then, if @code{pass} is in
6018 effect for the signal in question @emph{at that time}. In other words,
6019 after @value{GDBN} reports a signal, you can use the @code{handle}
6020 command with @code{pass} or @code{nopass} to control whether your
6021 program sees that signal when you continue.
6023 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6024 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6025 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6028 You can also use the @code{signal} command to prevent your program from
6029 seeing a signal, or cause it to see a signal it normally would not see,
6030 or to give it any signal at any time. For example, if your program stopped
6031 due to some sort of memory reference error, you might store correct
6032 values into the erroneous variables and continue, hoping to see more
6033 execution; but your program would probably terminate immediately as
6034 a result of the fatal signal once it saw the signal. To prevent this,
6035 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6038 @cindex stepping and signal handlers
6039 @anchor{stepping and signal handlers}
6041 @value{GDBN} optimizes for stepping the mainline code. If a signal
6042 that has @code{handle nostop} and @code{handle pass} set arrives while
6043 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6044 in progress, @value{GDBN} lets the signal handler run and then resumes
6045 stepping the mainline code once the signal handler returns. In other
6046 words, @value{GDBN} steps over the signal handler. This prevents
6047 signals that you've specified as not interesting (with @code{handle
6048 nostop}) from changing the focus of debugging unexpectedly. Note that
6049 the signal handler itself may still hit a breakpoint, stop for another
6050 signal that has @code{handle stop} in effect, or for any other event
6051 that normally results in stopping the stepping command sooner. Also
6052 note that @value{GDBN} still informs you that the program received a
6053 signal if @code{handle print} is set.
6055 @anchor{stepping into signal handlers}
6057 If you set @code{handle pass} for a signal, and your program sets up a
6058 handler for it, then issuing a stepping command, such as @code{step}
6059 or @code{stepi}, when your program is stopped due to the signal will
6060 step @emph{into} the signal handler (if the target supports that).
6062 Likewise, if you use the @code{queue-signal} command to queue a signal
6063 to be delivered to the current thread when execution of the thread
6064 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6065 stepping command will step into the signal handler.
6067 Here's an example, using @code{stepi} to step to the first instruction
6068 of @code{SIGUSR1}'s handler:
6071 (@value{GDBP}) handle SIGUSR1
6072 Signal Stop Print Pass to program Description
6073 SIGUSR1 Yes Yes Yes User defined signal 1
6077 Program received signal SIGUSR1, User defined signal 1.
6078 main () sigusr1.c:28
6081 sigusr1_handler () at sigusr1.c:9
6085 The same, but using @code{queue-signal} instead of waiting for the
6086 program to receive the signal first:
6091 (@value{GDBP}) queue-signal SIGUSR1
6093 sigusr1_handler () at sigusr1.c:9
6098 @cindex extra signal information
6099 @anchor{extra signal information}
6101 On some targets, @value{GDBN} can inspect extra signal information
6102 associated with the intercepted signal, before it is actually
6103 delivered to the program being debugged. This information is exported
6104 by the convenience variable @code{$_siginfo}, and consists of data
6105 that is passed by the kernel to the signal handler at the time of the
6106 receipt of a signal. The data type of the information itself is
6107 target dependent. You can see the data type using the @code{ptype
6108 $_siginfo} command. On Unix systems, it typically corresponds to the
6109 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6112 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6113 referenced address that raised a segmentation fault.
6117 (@value{GDBP}) continue
6118 Program received signal SIGSEGV, Segmentation fault.
6119 0x0000000000400766 in main ()
6121 (@value{GDBP}) ptype $_siginfo
6128 struct @{...@} _kill;
6129 struct @{...@} _timer;
6131 struct @{...@} _sigchld;
6132 struct @{...@} _sigfault;
6133 struct @{...@} _sigpoll;
6136 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6140 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6141 $1 = (void *) 0x7ffff7ff7000
6145 Depending on target support, @code{$_siginfo} may also be writable.
6147 @cindex Intel MPX boundary violations
6148 @cindex boundary violations, Intel MPX
6149 On some targets, a @code{SIGSEGV} can be caused by a boundary
6150 violation, i.e., accessing an address outside of the allowed range.
6151 In those cases @value{GDBN} may displays additional information,
6152 depending on how @value{GDBN} has been told to handle the signal.
6153 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6154 kind: "Upper" or "Lower", the memory address accessed and the
6155 bounds, while with @code{handle nostop SIGSEGV} no additional
6156 information is displayed.
6158 The usual output of a segfault is:
6160 Program received signal SIGSEGV, Segmentation fault
6161 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6162 68 value = *(p + len);
6165 While a bound violation is presented as:
6167 Program received signal SIGSEGV, Segmentation fault
6168 Upper bound violation while accessing address 0x7fffffffc3b3
6169 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6170 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6171 68 value = *(p + len);
6175 @section Stopping and Starting Multi-thread Programs
6177 @cindex stopped threads
6178 @cindex threads, stopped
6180 @cindex continuing threads
6181 @cindex threads, continuing
6183 @value{GDBN} supports debugging programs with multiple threads
6184 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6185 are two modes of controlling execution of your program within the
6186 debugger. In the default mode, referred to as @dfn{all-stop mode},
6187 when any thread in your program stops (for example, at a breakpoint
6188 or while being stepped), all other threads in the program are also stopped by
6189 @value{GDBN}. On some targets, @value{GDBN} also supports
6190 @dfn{non-stop mode}, in which other threads can continue to run freely while
6191 you examine the stopped thread in the debugger.
6194 * All-Stop Mode:: All threads stop when GDB takes control
6195 * Non-Stop Mode:: Other threads continue to execute
6196 * Background Execution:: Running your program asynchronously
6197 * Thread-Specific Breakpoints:: Controlling breakpoints
6198 * Interrupted System Calls:: GDB may interfere with system calls
6199 * Observer Mode:: GDB does not alter program behavior
6203 @subsection All-Stop Mode
6205 @cindex all-stop mode
6207 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6208 @emph{all} threads of execution stop, not just the current thread. This
6209 allows you to examine the overall state of the program, including
6210 switching between threads, without worrying that things may change
6213 Conversely, whenever you restart the program, @emph{all} threads start
6214 executing. @emph{This is true even when single-stepping} with commands
6215 like @code{step} or @code{next}.
6217 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6218 Since thread scheduling is up to your debugging target's operating
6219 system (not controlled by @value{GDBN}), other threads may
6220 execute more than one statement while the current thread completes a
6221 single step. Moreover, in general other threads stop in the middle of a
6222 statement, rather than at a clean statement boundary, when the program
6225 You might even find your program stopped in another thread after
6226 continuing or even single-stepping. This happens whenever some other
6227 thread runs into a breakpoint, a signal, or an exception before the
6228 first thread completes whatever you requested.
6230 @cindex automatic thread selection
6231 @cindex switching threads automatically
6232 @cindex threads, automatic switching
6233 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6234 signal, it automatically selects the thread where that breakpoint or
6235 signal happened. @value{GDBN} alerts you to the context switch with a
6236 message such as @samp{[Switching to Thread @var{n}]} to identify the
6239 On some OSes, you can modify @value{GDBN}'s default behavior by
6240 locking the OS scheduler to allow only a single thread to run.
6243 @item set scheduler-locking @var{mode}
6244 @cindex scheduler locking mode
6245 @cindex lock scheduler
6246 Set the scheduler locking mode. It applies to normal execution,
6247 record mode, and replay mode. If it is @code{off}, then there is no
6248 locking and any thread may run at any time. If @code{on}, then only
6249 the current thread may run when the inferior is resumed. The
6250 @code{step} mode optimizes for single-stepping; it prevents other
6251 threads from preempting the current thread while you are stepping, so
6252 that the focus of debugging does not change unexpectedly. Other
6253 threads never get a chance to run when you step, and they are
6254 completely free to run when you use commands like @samp{continue},
6255 @samp{until}, or @samp{finish}. However, unless another thread hits a
6256 breakpoint during its timeslice, @value{GDBN} does not change the
6257 current thread away from the thread that you are debugging. The
6258 @code{replay} mode behaves like @code{off} in record mode and like
6259 @code{on} in replay mode.
6261 @item show scheduler-locking
6262 Display the current scheduler locking mode.
6265 @cindex resume threads of multiple processes simultaneously
6266 By default, when you issue one of the execution commands such as
6267 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6268 threads of the current inferior to run. For example, if @value{GDBN}
6269 is attached to two inferiors, each with two threads, the
6270 @code{continue} command resumes only the two threads of the current
6271 inferior. This is useful, for example, when you debug a program that
6272 forks and you want to hold the parent stopped (so that, for instance,
6273 it doesn't run to exit), while you debug the child. In other
6274 situations, you may not be interested in inspecting the current state
6275 of any of the processes @value{GDBN} is attached to, and you may want
6276 to resume them all until some breakpoint is hit. In the latter case,
6277 you can instruct @value{GDBN} to allow all threads of all the
6278 inferiors to run with the @w{@code{set schedule-multiple}} command.
6281 @kindex set schedule-multiple
6282 @item set schedule-multiple
6283 Set the mode for allowing threads of multiple processes to be resumed
6284 when an execution command is issued. When @code{on}, all threads of
6285 all processes are allowed to run. When @code{off}, only the threads
6286 of the current process are resumed. The default is @code{off}. The
6287 @code{scheduler-locking} mode takes precedence when set to @code{on},
6288 or while you are stepping and set to @code{step}.
6290 @item show schedule-multiple
6291 Display the current mode for resuming the execution of threads of
6296 @subsection Non-Stop Mode
6298 @cindex non-stop mode
6300 @c This section is really only a place-holder, and needs to be expanded
6301 @c with more details.
6303 For some multi-threaded targets, @value{GDBN} supports an optional
6304 mode of operation in which you can examine stopped program threads in
6305 the debugger while other threads continue to execute freely. This
6306 minimizes intrusion when debugging live systems, such as programs
6307 where some threads have real-time constraints or must continue to
6308 respond to external events. This is referred to as @dfn{non-stop} mode.
6310 In non-stop mode, when a thread stops to report a debugging event,
6311 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6312 threads as well, in contrast to the all-stop mode behavior. Additionally,
6313 execution commands such as @code{continue} and @code{step} apply by default
6314 only to the current thread in non-stop mode, rather than all threads as
6315 in all-stop mode. This allows you to control threads explicitly in
6316 ways that are not possible in all-stop mode --- for example, stepping
6317 one thread while allowing others to run freely, stepping
6318 one thread while holding all others stopped, or stepping several threads
6319 independently and simultaneously.
6321 To enter non-stop mode, use this sequence of commands before you run
6322 or attach to your program:
6325 # If using the CLI, pagination breaks non-stop.
6328 # Finally, turn it on!
6332 You can use these commands to manipulate the non-stop mode setting:
6335 @kindex set non-stop
6336 @item set non-stop on
6337 Enable selection of non-stop mode.
6338 @item set non-stop off
6339 Disable selection of non-stop mode.
6340 @kindex show non-stop
6342 Show the current non-stop enablement setting.
6345 Note these commands only reflect whether non-stop mode is enabled,
6346 not whether the currently-executing program is being run in non-stop mode.
6347 In particular, the @code{set non-stop} preference is only consulted when
6348 @value{GDBN} starts or connects to the target program, and it is generally
6349 not possible to switch modes once debugging has started. Furthermore,
6350 since not all targets support non-stop mode, even when you have enabled
6351 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6354 In non-stop mode, all execution commands apply only to the current thread
6355 by default. That is, @code{continue} only continues one thread.
6356 To continue all threads, issue @code{continue -a} or @code{c -a}.
6358 You can use @value{GDBN}'s background execution commands
6359 (@pxref{Background Execution}) to run some threads in the background
6360 while you continue to examine or step others from @value{GDBN}.
6361 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6362 always executed asynchronously in non-stop mode.
6364 Suspending execution is done with the @code{interrupt} command when
6365 running in the background, or @kbd{Ctrl-c} during foreground execution.
6366 In all-stop mode, this stops the whole process;
6367 but in non-stop mode the interrupt applies only to the current thread.
6368 To stop the whole program, use @code{interrupt -a}.
6370 Other execution commands do not currently support the @code{-a} option.
6372 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6373 that thread current, as it does in all-stop mode. This is because the
6374 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6375 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6376 changed to a different thread just as you entered a command to operate on the
6377 previously current thread.
6379 @node Background Execution
6380 @subsection Background Execution
6382 @cindex foreground execution
6383 @cindex background execution
6384 @cindex asynchronous execution
6385 @cindex execution, foreground, background and asynchronous
6387 @value{GDBN}'s execution commands have two variants: the normal
6388 foreground (synchronous) behavior, and a background
6389 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6390 the program to report that some thread has stopped before prompting for
6391 another command. In background execution, @value{GDBN} immediately gives
6392 a command prompt so that you can issue other commands while your program runs.
6394 If the target doesn't support async mode, @value{GDBN} issues an error
6395 message if you attempt to use the background execution commands.
6397 @cindex @code{&}, background execution of commands
6398 To specify background execution, add a @code{&} to the command. For example,
6399 the background form of the @code{continue} command is @code{continue&}, or
6400 just @code{c&}. The execution commands that accept background execution
6406 @xref{Starting, , Starting your Program}.
6410 @xref{Attach, , Debugging an Already-running Process}.
6414 @xref{Continuing and Stepping, step}.
6418 @xref{Continuing and Stepping, stepi}.
6422 @xref{Continuing and Stepping, next}.
6426 @xref{Continuing and Stepping, nexti}.
6430 @xref{Continuing and Stepping, continue}.
6434 @xref{Continuing and Stepping, finish}.
6438 @xref{Continuing and Stepping, until}.
6442 Background execution is especially useful in conjunction with non-stop
6443 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6444 However, you can also use these commands in the normal all-stop mode with
6445 the restriction that you cannot issue another execution command until the
6446 previous one finishes. Examples of commands that are valid in all-stop
6447 mode while the program is running include @code{help} and @code{info break}.
6449 You can interrupt your program while it is running in the background by
6450 using the @code{interrupt} command.
6457 Suspend execution of the running program. In all-stop mode,
6458 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6459 only the current thread. To stop the whole program in non-stop mode,
6460 use @code{interrupt -a}.
6463 @node Thread-Specific Breakpoints
6464 @subsection Thread-Specific Breakpoints
6466 When your program has multiple threads (@pxref{Threads,, Debugging
6467 Programs with Multiple Threads}), you can choose whether to set
6468 breakpoints on all threads, or on a particular thread.
6471 @cindex breakpoints and threads
6472 @cindex thread breakpoints
6473 @kindex break @dots{} thread @var{thread-id}
6474 @item break @var{location} thread @var{thread-id}
6475 @itemx break @var{location} thread @var{thread-id} if @dots{}
6476 @var{location} specifies source lines; there are several ways of
6477 writing them (@pxref{Specify Location}), but the effect is always to
6478 specify some source line.
6480 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6481 to specify that you only want @value{GDBN} to stop the program when a
6482 particular thread reaches this breakpoint. The @var{thread-id} specifier
6483 is one of the thread identifiers assigned by @value{GDBN}, shown
6484 in the first column of the @samp{info threads} display.
6486 If you do not specify @samp{thread @var{thread-id}} when you set a
6487 breakpoint, the breakpoint applies to @emph{all} threads of your
6490 You can use the @code{thread} qualifier on conditional breakpoints as
6491 well; in this case, place @samp{thread @var{thread-id}} before or
6492 after the breakpoint condition, like this:
6495 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6500 Thread-specific breakpoints are automatically deleted when
6501 @value{GDBN} detects the corresponding thread is no longer in the
6502 thread list. For example:
6506 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6509 There are several ways for a thread to disappear, such as a regular
6510 thread exit, but also when you detach from the process with the
6511 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6512 Process}), or if @value{GDBN} loses the remote connection
6513 (@pxref{Remote Debugging}), etc. Note that with some targets,
6514 @value{GDBN} is only able to detect a thread has exited when the user
6515 explictly asks for the thread list with the @code{info threads}
6518 @node Interrupted System Calls
6519 @subsection Interrupted System Calls
6521 @cindex thread breakpoints and system calls
6522 @cindex system calls and thread breakpoints
6523 @cindex premature return from system calls
6524 There is an unfortunate side effect when using @value{GDBN} to debug
6525 multi-threaded programs. If one thread stops for a
6526 breakpoint, or for some other reason, and another thread is blocked in a
6527 system call, then the system call may return prematurely. This is a
6528 consequence of the interaction between multiple threads and the signals
6529 that @value{GDBN} uses to implement breakpoints and other events that
6532 To handle this problem, your program should check the return value of
6533 each system call and react appropriately. This is good programming
6536 For example, do not write code like this:
6542 The call to @code{sleep} will return early if a different thread stops
6543 at a breakpoint or for some other reason.
6545 Instead, write this:
6550 unslept = sleep (unslept);
6553 A system call is allowed to return early, so the system is still
6554 conforming to its specification. But @value{GDBN} does cause your
6555 multi-threaded program to behave differently than it would without
6558 Also, @value{GDBN} uses internal breakpoints in the thread library to
6559 monitor certain events such as thread creation and thread destruction.
6560 When such an event happens, a system call in another thread may return
6561 prematurely, even though your program does not appear to stop.
6564 @subsection Observer Mode
6566 If you want to build on non-stop mode and observe program behavior
6567 without any chance of disruption by @value{GDBN}, you can set
6568 variables to disable all of the debugger's attempts to modify state,
6569 whether by writing memory, inserting breakpoints, etc. These operate
6570 at a low level, intercepting operations from all commands.
6572 When all of these are set to @code{off}, then @value{GDBN} is said to
6573 be @dfn{observer mode}. As a convenience, the variable
6574 @code{observer} can be set to disable these, plus enable non-stop
6577 Note that @value{GDBN} will not prevent you from making nonsensical
6578 combinations of these settings. For instance, if you have enabled
6579 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6580 then breakpoints that work by writing trap instructions into the code
6581 stream will still not be able to be placed.
6586 @item set observer on
6587 @itemx set observer off
6588 When set to @code{on}, this disables all the permission variables
6589 below (except for @code{insert-fast-tracepoints}), plus enables
6590 non-stop debugging. Setting this to @code{off} switches back to
6591 normal debugging, though remaining in non-stop mode.
6594 Show whether observer mode is on or off.
6596 @kindex may-write-registers
6597 @item set may-write-registers on
6598 @itemx set may-write-registers off
6599 This controls whether @value{GDBN} will attempt to alter the values of
6600 registers, such as with assignment expressions in @code{print}, or the
6601 @code{jump} command. It defaults to @code{on}.
6603 @item show may-write-registers
6604 Show the current permission to write registers.
6606 @kindex may-write-memory
6607 @item set may-write-memory on
6608 @itemx set may-write-memory off
6609 This controls whether @value{GDBN} will attempt to alter the contents
6610 of memory, such as with assignment expressions in @code{print}. It
6611 defaults to @code{on}.
6613 @item show may-write-memory
6614 Show the current permission to write memory.
6616 @kindex may-insert-breakpoints
6617 @item set may-insert-breakpoints on
6618 @itemx set may-insert-breakpoints off
6619 This controls whether @value{GDBN} will attempt to insert breakpoints.
6620 This affects all breakpoints, including internal breakpoints defined
6621 by @value{GDBN}. It defaults to @code{on}.
6623 @item show may-insert-breakpoints
6624 Show the current permission to insert breakpoints.
6626 @kindex may-insert-tracepoints
6627 @item set may-insert-tracepoints on
6628 @itemx set may-insert-tracepoints off
6629 This controls whether @value{GDBN} will attempt to insert (regular)
6630 tracepoints at the beginning of a tracing experiment. It affects only
6631 non-fast tracepoints, fast tracepoints being under the control of
6632 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6634 @item show may-insert-tracepoints
6635 Show the current permission to insert tracepoints.
6637 @kindex may-insert-fast-tracepoints
6638 @item set may-insert-fast-tracepoints on
6639 @itemx set may-insert-fast-tracepoints off
6640 This controls whether @value{GDBN} will attempt to insert fast
6641 tracepoints at the beginning of a tracing experiment. It affects only
6642 fast tracepoints, regular (non-fast) tracepoints being under the
6643 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6645 @item show may-insert-fast-tracepoints
6646 Show the current permission to insert fast tracepoints.
6648 @kindex may-interrupt
6649 @item set may-interrupt on
6650 @itemx set may-interrupt off
6651 This controls whether @value{GDBN} will attempt to interrupt or stop
6652 program execution. When this variable is @code{off}, the
6653 @code{interrupt} command will have no effect, nor will
6654 @kbd{Ctrl-c}. It defaults to @code{on}.
6656 @item show may-interrupt
6657 Show the current permission to interrupt or stop the program.
6661 @node Reverse Execution
6662 @chapter Running programs backward
6663 @cindex reverse execution
6664 @cindex running programs backward
6666 When you are debugging a program, it is not unusual to realize that
6667 you have gone too far, and some event of interest has already happened.
6668 If the target environment supports it, @value{GDBN} can allow you to
6669 ``rewind'' the program by running it backward.
6671 A target environment that supports reverse execution should be able
6672 to ``undo'' the changes in machine state that have taken place as the
6673 program was executing normally. Variables, registers etc.@: should
6674 revert to their previous values. Obviously this requires a great
6675 deal of sophistication on the part of the target environment; not
6676 all target environments can support reverse execution.
6678 When a program is executed in reverse, the instructions that
6679 have most recently been executed are ``un-executed'', in reverse
6680 order. The program counter runs backward, following the previous
6681 thread of execution in reverse. As each instruction is ``un-executed'',
6682 the values of memory and/or registers that were changed by that
6683 instruction are reverted to their previous states. After executing
6684 a piece of source code in reverse, all side effects of that code
6685 should be ``undone'', and all variables should be returned to their
6686 prior values@footnote{
6687 Note that some side effects are easier to undo than others. For instance,
6688 memory and registers are relatively easy, but device I/O is hard. Some
6689 targets may be able undo things like device I/O, and some may not.
6691 The contract between @value{GDBN} and the reverse executing target
6692 requires only that the target do something reasonable when
6693 @value{GDBN} tells it to execute backwards, and then report the
6694 results back to @value{GDBN}. Whatever the target reports back to
6695 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6696 assumes that the memory and registers that the target reports are in a
6697 consistant state, but @value{GDBN} accepts whatever it is given.
6700 If you are debugging in a target environment that supports
6701 reverse execution, @value{GDBN} provides the following commands.
6704 @kindex reverse-continue
6705 @kindex rc @r{(@code{reverse-continue})}
6706 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6707 @itemx rc @r{[}@var{ignore-count}@r{]}
6708 Beginning at the point where your program last stopped, start executing
6709 in reverse. Reverse execution will stop for breakpoints and synchronous
6710 exceptions (signals), just like normal execution. Behavior of
6711 asynchronous signals depends on the target environment.
6713 @kindex reverse-step
6714 @kindex rs @r{(@code{step})}
6715 @item reverse-step @r{[}@var{count}@r{]}
6716 Run the program backward until control reaches the start of a
6717 different source line; then stop it, and return control to @value{GDBN}.
6719 Like the @code{step} command, @code{reverse-step} will only stop
6720 at the beginning of a source line. It ``un-executes'' the previously
6721 executed source line. If the previous source line included calls to
6722 debuggable functions, @code{reverse-step} will step (backward) into
6723 the called function, stopping at the beginning of the @emph{last}
6724 statement in the called function (typically a return statement).
6726 Also, as with the @code{step} command, if non-debuggable functions are
6727 called, @code{reverse-step} will run thru them backward without stopping.
6729 @kindex reverse-stepi
6730 @kindex rsi @r{(@code{reverse-stepi})}
6731 @item reverse-stepi @r{[}@var{count}@r{]}
6732 Reverse-execute one machine instruction. Note that the instruction
6733 to be reverse-executed is @emph{not} the one pointed to by the program
6734 counter, but the instruction executed prior to that one. For instance,
6735 if the last instruction was a jump, @code{reverse-stepi} will take you
6736 back from the destination of the jump to the jump instruction itself.
6738 @kindex reverse-next
6739 @kindex rn @r{(@code{reverse-next})}
6740 @item reverse-next @r{[}@var{count}@r{]}
6741 Run backward to the beginning of the previous line executed in
6742 the current (innermost) stack frame. If the line contains function
6743 calls, they will be ``un-executed'' without stopping. Starting from
6744 the first line of a function, @code{reverse-next} will take you back
6745 to the caller of that function, @emph{before} the function was called,
6746 just as the normal @code{next} command would take you from the last
6747 line of a function back to its return to its caller
6748 @footnote{Unless the code is too heavily optimized.}.
6750 @kindex reverse-nexti
6751 @kindex rni @r{(@code{reverse-nexti})}
6752 @item reverse-nexti @r{[}@var{count}@r{]}
6753 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6754 in reverse, except that called functions are ``un-executed'' atomically.
6755 That is, if the previously executed instruction was a return from
6756 another function, @code{reverse-nexti} will continue to execute
6757 in reverse until the call to that function (from the current stack
6760 @kindex reverse-finish
6761 @item reverse-finish
6762 Just as the @code{finish} command takes you to the point where the
6763 current function returns, @code{reverse-finish} takes you to the point
6764 where it was called. Instead of ending up at the end of the current
6765 function invocation, you end up at the beginning.
6767 @kindex set exec-direction
6768 @item set exec-direction
6769 Set the direction of target execution.
6770 @item set exec-direction reverse
6771 @cindex execute forward or backward in time
6772 @value{GDBN} will perform all execution commands in reverse, until the
6773 exec-direction mode is changed to ``forward''. Affected commands include
6774 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6775 command cannot be used in reverse mode.
6776 @item set exec-direction forward
6777 @value{GDBN} will perform all execution commands in the normal fashion.
6778 This is the default.
6782 @node Process Record and Replay
6783 @chapter Recording Inferior's Execution and Replaying It
6784 @cindex process record and replay
6785 @cindex recording inferior's execution and replaying it
6787 On some platforms, @value{GDBN} provides a special @dfn{process record
6788 and replay} target that can record a log of the process execution, and
6789 replay it later with both forward and reverse execution commands.
6792 When this target is in use, if the execution log includes the record
6793 for the next instruction, @value{GDBN} will debug in @dfn{replay
6794 mode}. In the replay mode, the inferior does not really execute code
6795 instructions. Instead, all the events that normally happen during
6796 code execution are taken from the execution log. While code is not
6797 really executed in replay mode, the values of registers (including the
6798 program counter register) and the memory of the inferior are still
6799 changed as they normally would. Their contents are taken from the
6803 If the record for the next instruction is not in the execution log,
6804 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6805 inferior executes normally, and @value{GDBN} records the execution log
6808 The process record and replay target supports reverse execution
6809 (@pxref{Reverse Execution}), even if the platform on which the
6810 inferior runs does not. However, the reverse execution is limited in
6811 this case by the range of the instructions recorded in the execution
6812 log. In other words, reverse execution on platforms that don't
6813 support it directly can only be done in the replay mode.
6815 When debugging in the reverse direction, @value{GDBN} will work in
6816 replay mode as long as the execution log includes the record for the
6817 previous instruction; otherwise, it will work in record mode, if the
6818 platform supports reverse execution, or stop if not.
6820 For architecture environments that support process record and replay,
6821 @value{GDBN} provides the following commands:
6824 @kindex target record
6825 @kindex target record-full
6826 @kindex target record-btrace
6829 @kindex record btrace
6830 @kindex record btrace bts
6831 @kindex record btrace pt
6837 @kindex rec btrace bts
6838 @kindex rec btrace pt
6841 @item record @var{method}
6842 This command starts the process record and replay target. The
6843 recording method can be specified as parameter. Without a parameter
6844 the command uses the @code{full} recording method. The following
6845 recording methods are available:
6849 Full record/replay recording using @value{GDBN}'s software record and
6850 replay implementation. This method allows replaying and reverse
6853 @item btrace @var{format}
6854 Hardware-supported instruction recording. This method does not record
6855 data. Further, the data is collected in a ring buffer so old data will
6856 be overwritten when the buffer is full. It allows limited reverse
6857 execution. Variables and registers are not available during reverse
6858 execution. In remote debugging, recording continues on disconnect.
6859 Recorded data can be inspected after reconnecting. The recording may
6860 be stopped using @code{record stop}.
6862 The recording format can be specified as parameter. Without a parameter
6863 the command chooses the recording format. The following recording
6864 formats are available:
6868 @cindex branch trace store
6869 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6870 this format, the processor stores a from/to record for each executed
6871 branch in the btrace ring buffer.
6874 @cindex Intel Processor Trace
6875 Use the @dfn{Intel Processor Trace} recording format. In this
6876 format, the processor stores the execution trace in a compressed form
6877 that is afterwards decoded by @value{GDBN}.
6879 The trace can be recorded with very low overhead. The compressed
6880 trace format also allows small trace buffers to already contain a big
6881 number of instructions compared to @acronym{BTS}.
6883 Decoding the recorded execution trace, on the other hand, is more
6884 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6885 increased number of instructions to process. You should increase the
6886 buffer-size with care.
6889 Not all recording formats may be available on all processors.
6892 The process record and replay target can only debug a process that is
6893 already running. Therefore, you need first to start the process with
6894 the @kbd{run} or @kbd{start} commands, and then start the recording
6895 with the @kbd{record @var{method}} command.
6897 @cindex displaced stepping, and process record and replay
6898 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6899 will be automatically disabled when process record and replay target
6900 is started. That's because the process record and replay target
6901 doesn't support displaced stepping.
6903 @cindex non-stop mode, and process record and replay
6904 @cindex asynchronous execution, and process record and replay
6905 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6906 the asynchronous execution mode (@pxref{Background Execution}), not
6907 all recording methods are available. The @code{full} recording method
6908 does not support these two modes.
6913 Stop the process record and replay target. When process record and
6914 replay target stops, the entire execution log will be deleted and the
6915 inferior will either be terminated, or will remain in its final state.
6917 When you stop the process record and replay target in record mode (at
6918 the end of the execution log), the inferior will be stopped at the
6919 next instruction that would have been recorded. In other words, if
6920 you record for a while and then stop recording, the inferior process
6921 will be left in the same state as if the recording never happened.
6923 On the other hand, if the process record and replay target is stopped
6924 while in replay mode (that is, not at the end of the execution log,
6925 but at some earlier point), the inferior process will become ``live''
6926 at that earlier state, and it will then be possible to continue the
6927 usual ``live'' debugging of the process from that state.
6929 When the inferior process exits, or @value{GDBN} detaches from it,
6930 process record and replay target will automatically stop itself.
6934 Go to a specific location in the execution log. There are several
6935 ways to specify the location to go to:
6938 @item record goto begin
6939 @itemx record goto start
6940 Go to the beginning of the execution log.
6942 @item record goto end
6943 Go to the end of the execution log.
6945 @item record goto @var{n}
6946 Go to instruction number @var{n} in the execution log.
6950 @item record save @var{filename}
6951 Save the execution log to a file @file{@var{filename}}.
6952 Default filename is @file{gdb_record.@var{process_id}}, where
6953 @var{process_id} is the process ID of the inferior.
6955 This command may not be available for all recording methods.
6957 @kindex record restore
6958 @item record restore @var{filename}
6959 Restore the execution log from a file @file{@var{filename}}.
6960 File must have been created with @code{record save}.
6962 @kindex set record full
6963 @item set record full insn-number-max @var{limit}
6964 @itemx set record full insn-number-max unlimited
6965 Set the limit of instructions to be recorded for the @code{full}
6966 recording method. Default value is 200000.
6968 If @var{limit} is a positive number, then @value{GDBN} will start
6969 deleting instructions from the log once the number of the record
6970 instructions becomes greater than @var{limit}. For every new recorded
6971 instruction, @value{GDBN} will delete the earliest recorded
6972 instruction to keep the number of recorded instructions at the limit.
6973 (Since deleting recorded instructions loses information, @value{GDBN}
6974 lets you control what happens when the limit is reached, by means of
6975 the @code{stop-at-limit} option, described below.)
6977 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6978 delete recorded instructions from the execution log. The number of
6979 recorded instructions is limited only by the available memory.
6981 @kindex show record full
6982 @item show record full insn-number-max
6983 Show the limit of instructions to be recorded with the @code{full}
6986 @item set record full stop-at-limit
6987 Control the behavior of the @code{full} recording method when the
6988 number of recorded instructions reaches the limit. If ON (the
6989 default), @value{GDBN} will stop when the limit is reached for the
6990 first time and ask you whether you want to stop the inferior or
6991 continue running it and recording the execution log. If you decide
6992 to continue recording, each new recorded instruction will cause the
6993 oldest one to be deleted.
6995 If this option is OFF, @value{GDBN} will automatically delete the
6996 oldest record to make room for each new one, without asking.
6998 @item show record full stop-at-limit
6999 Show the current setting of @code{stop-at-limit}.
7001 @item set record full memory-query
7002 Control the behavior when @value{GDBN} is unable to record memory
7003 changes caused by an instruction for the @code{full} recording method.
7004 If ON, @value{GDBN} will query whether to stop the inferior in that
7007 If this option is OFF (the default), @value{GDBN} will automatically
7008 ignore the effect of such instructions on memory. Later, when
7009 @value{GDBN} replays this execution log, it will mark the log of this
7010 instruction as not accessible, and it will not affect the replay
7013 @item show record full memory-query
7014 Show the current setting of @code{memory-query}.
7016 @kindex set record btrace
7017 The @code{btrace} record target does not trace data. As a
7018 convenience, when replaying, @value{GDBN} reads read-only memory off
7019 the live program directly, assuming that the addresses of the
7020 read-only areas don't change. This for example makes it possible to
7021 disassemble code while replaying, but not to print variables.
7022 In some cases, being able to inspect variables might be useful.
7023 You can use the following command for that:
7025 @item set record btrace replay-memory-access
7026 Control the behavior of the @code{btrace} recording method when
7027 accessing memory during replay. If @code{read-only} (the default),
7028 @value{GDBN} will only allow accesses to read-only memory.
7029 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7030 and to read-write memory. Beware that the accessed memory corresponds
7031 to the live target and not necessarily to the current replay
7034 @item set record btrace cpu @var{identifier}
7035 Set the processor to be used for enabling workarounds for processor
7036 errata when decoding the trace.
7038 Processor errata are defects in processor operation, caused by its
7039 design or manufacture. They can cause a trace not to match the
7040 specification. This, in turn, may cause trace decode to fail.
7041 @value{GDBN} can detect erroneous trace packets and correct them, thus
7042 avoiding the decoding failures. These corrections are known as
7043 @dfn{errata workarounds}, and are enabled based on the processor on
7044 which the trace was recorded.
7046 By default, @value{GDBN} attempts to detect the processor
7047 automatically, and apply the necessary workarounds for it. However,
7048 you may need to specify the processor if @value{GDBN} does not yet
7049 support it. This command allows you to do that, and also allows to
7050 disable the workarounds.
7052 The argument @var{identifier} identifies the @sc{cpu} and is of the
7053 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7054 there are two special identifiers, @code{none} and @code{auto}
7057 The following vendor identifiers and corresponding processor
7058 identifiers are currently supported:
7060 @multitable @columnfractions .1 .9
7063 @tab @var{family}/@var{model}[/@var{stepping}]
7067 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7068 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7070 If @var{identifier} is @code{auto}, enable errata workarounds for the
7071 processor on which the trace was recorded. If @var{identifier} is
7072 @code{none}, errata workarounds are disabled.
7074 For example, when using an old @value{GDBN} on a new system, decode
7075 may fail because @value{GDBN} does not support the new processor. It
7076 often suffices to specify an older processor that @value{GDBN}
7081 Active record target: record-btrace
7082 Recording format: Intel Processor Trace.
7084 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7085 (gdb) set record btrace cpu intel:6/158
7087 Active record target: record-btrace
7088 Recording format: Intel Processor Trace.
7090 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7093 @kindex show record btrace
7094 @item show record btrace replay-memory-access
7095 Show the current setting of @code{replay-memory-access}.
7097 @item show record btrace cpu
7098 Show the processor to be used for enabling trace decode errata
7101 @kindex set record btrace bts
7102 @item set record btrace bts buffer-size @var{size}
7103 @itemx set record btrace bts buffer-size unlimited
7104 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7105 format. Default is 64KB.
7107 If @var{size} is a positive number, then @value{GDBN} will try to
7108 allocate a buffer of at least @var{size} bytes for each new thread
7109 that uses the btrace recording method and the @acronym{BTS} format.
7110 The actually obtained buffer size may differ from the requested
7111 @var{size}. Use the @code{info record} command to see the actual
7112 buffer size for each thread that uses the btrace recording method and
7113 the @acronym{BTS} format.
7115 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7116 allocate a buffer of 4MB.
7118 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7119 also need longer to process the branch trace data before it can be used.
7121 @item show record btrace bts buffer-size @var{size}
7122 Show the current setting of the requested ring buffer size for branch
7123 tracing in @acronym{BTS} format.
7125 @kindex set record btrace pt
7126 @item set record btrace pt buffer-size @var{size}
7127 @itemx set record btrace pt buffer-size unlimited
7128 Set the requested ring buffer size for branch tracing in Intel
7129 Processor Trace format. Default is 16KB.
7131 If @var{size} is a positive number, then @value{GDBN} will try to
7132 allocate a buffer of at least @var{size} bytes for each new thread
7133 that uses the btrace recording method and the Intel Processor Trace
7134 format. The actually obtained buffer size may differ from the
7135 requested @var{size}. Use the @code{info record} command to see the
7136 actual buffer size for each thread.
7138 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7139 allocate a buffer of 4MB.
7141 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7142 also need longer to process the branch trace data before it can be used.
7144 @item show record btrace pt buffer-size @var{size}
7145 Show the current setting of the requested ring buffer size for branch
7146 tracing in Intel Processor Trace format.
7150 Show various statistics about the recording depending on the recording
7155 For the @code{full} recording method, it shows the state of process
7156 record and its in-memory execution log buffer, including:
7160 Whether in record mode or replay mode.
7162 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7164 Highest recorded instruction number.
7166 Current instruction about to be replayed (if in replay mode).
7168 Number of instructions contained in the execution log.
7170 Maximum number of instructions that may be contained in the execution log.
7174 For the @code{btrace} recording method, it shows:
7180 Number of instructions that have been recorded.
7182 Number of blocks of sequential control-flow formed by the recorded
7185 Whether in record mode or replay mode.
7188 For the @code{bts} recording format, it also shows:
7191 Size of the perf ring buffer.
7194 For the @code{pt} recording format, it also shows:
7197 Size of the perf ring buffer.
7201 @kindex record delete
7204 When record target runs in replay mode (``in the past''), delete the
7205 subsequent execution log and begin to record a new execution log starting
7206 from the current address. This means you will abandon the previously
7207 recorded ``future'' and begin recording a new ``future''.
7209 @kindex record instruction-history
7210 @kindex rec instruction-history
7211 @item record instruction-history
7212 Disassembles instructions from the recorded execution log. By
7213 default, ten instructions are disassembled. This can be changed using
7214 the @code{set record instruction-history-size} command. Instructions
7215 are printed in execution order.
7217 It can also print mixed source+disassembly if you specify the the
7218 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7219 as well as in symbolic form by specifying the @code{/r} modifier.
7221 The current position marker is printed for the instruction at the
7222 current program counter value. This instruction can appear multiple
7223 times in the trace and the current position marker will be printed
7224 every time. To omit the current position marker, specify the
7227 To better align the printed instructions when the trace contains
7228 instructions from more than one function, the function name may be
7229 omitted by specifying the @code{/f} modifier.
7231 Speculatively executed instructions are prefixed with @samp{?}. This
7232 feature is not available for all recording formats.
7234 There are several ways to specify what part of the execution log to
7238 @item record instruction-history @var{insn}
7239 Disassembles ten instructions starting from instruction number
7242 @item record instruction-history @var{insn}, +/-@var{n}
7243 Disassembles @var{n} instructions around instruction number
7244 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7245 @var{n} instructions after instruction number @var{insn}. If
7246 @var{n} is preceded with @code{-}, disassembles @var{n}
7247 instructions before instruction number @var{insn}.
7249 @item record instruction-history
7250 Disassembles ten more instructions after the last disassembly.
7252 @item record instruction-history -
7253 Disassembles ten more instructions before the last disassembly.
7255 @item record instruction-history @var{begin}, @var{end}
7256 Disassembles instructions beginning with instruction number
7257 @var{begin} until instruction number @var{end}. The instruction
7258 number @var{end} is included.
7261 This command may not be available for all recording methods.
7264 @item set record instruction-history-size @var{size}
7265 @itemx set record instruction-history-size unlimited
7266 Define how many instructions to disassemble in the @code{record
7267 instruction-history} command. The default value is 10.
7268 A @var{size} of @code{unlimited} means unlimited instructions.
7271 @item show record instruction-history-size
7272 Show how many instructions to disassemble in the @code{record
7273 instruction-history} command.
7275 @kindex record function-call-history
7276 @kindex rec function-call-history
7277 @item record function-call-history
7278 Prints the execution history at function granularity. It prints one
7279 line for each sequence of instructions that belong to the same
7280 function giving the name of that function, the source lines
7281 for this instruction sequence (if the @code{/l} modifier is
7282 specified), and the instructions numbers that form the sequence (if
7283 the @code{/i} modifier is specified). The function names are indented
7284 to reflect the call stack depth if the @code{/c} modifier is
7285 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7289 (@value{GDBP}) @b{list 1, 10}
7300 (@value{GDBP}) @b{record function-call-history /ilc}
7301 1 bar inst 1,4 at foo.c:6,8
7302 2 foo inst 5,10 at foo.c:2,3
7303 3 bar inst 11,13 at foo.c:9,10
7306 By default, ten lines are printed. This can be changed using the
7307 @code{set record function-call-history-size} command. Functions are
7308 printed in execution order. There are several ways to specify what
7312 @item record function-call-history @var{func}
7313 Prints ten functions starting from function number @var{func}.
7315 @item record function-call-history @var{func}, +/-@var{n}
7316 Prints @var{n} functions around function number @var{func}. If
7317 @var{n} is preceded with @code{+}, prints @var{n} functions after
7318 function number @var{func}. If @var{n} is preceded with @code{-},
7319 prints @var{n} functions before function number @var{func}.
7321 @item record function-call-history
7322 Prints ten more functions after the last ten-line print.
7324 @item record function-call-history -
7325 Prints ten more functions before the last ten-line print.
7327 @item record function-call-history @var{begin}, @var{end}
7328 Prints functions beginning with function number @var{begin} until
7329 function number @var{end}. The function number @var{end} is included.
7332 This command may not be available for all recording methods.
7334 @item set record function-call-history-size @var{size}
7335 @itemx set record function-call-history-size unlimited
7336 Define how many lines to print in the
7337 @code{record function-call-history} command. The default value is 10.
7338 A size of @code{unlimited} means unlimited lines.
7340 @item show record function-call-history-size
7341 Show how many lines to print in the
7342 @code{record function-call-history} command.
7347 @chapter Examining the Stack
7349 When your program has stopped, the first thing you need to know is where it
7350 stopped and how it got there.
7353 Each time your program performs a function call, information about the call
7355 That information includes the location of the call in your program,
7356 the arguments of the call,
7357 and the local variables of the function being called.
7358 The information is saved in a block of data called a @dfn{stack frame}.
7359 The stack frames are allocated in a region of memory called the @dfn{call
7362 When your program stops, the @value{GDBN} commands for examining the
7363 stack allow you to see all of this information.
7365 @cindex selected frame
7366 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7367 @value{GDBN} commands refer implicitly to the selected frame. In
7368 particular, whenever you ask @value{GDBN} for the value of a variable in
7369 your program, the value is found in the selected frame. There are
7370 special @value{GDBN} commands to select whichever frame you are
7371 interested in. @xref{Selection, ,Selecting a Frame}.
7373 When your program stops, @value{GDBN} automatically selects the
7374 currently executing frame and describes it briefly, similar to the
7375 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7378 * Frames:: Stack frames
7379 * Backtrace:: Backtraces
7380 * Selection:: Selecting a frame
7381 * Frame Info:: Information on a frame
7382 * Frame Apply:: Applying a command to several frames
7383 * Frame Filter Management:: Managing frame filters
7388 @section Stack Frames
7390 @cindex frame, definition
7392 The call stack is divided up into contiguous pieces called @dfn{stack
7393 frames}, or @dfn{frames} for short; each frame is the data associated
7394 with one call to one function. The frame contains the arguments given
7395 to the function, the function's local variables, and the address at
7396 which the function is executing.
7398 @cindex initial frame
7399 @cindex outermost frame
7400 @cindex innermost frame
7401 When your program is started, the stack has only one frame, that of the
7402 function @code{main}. This is called the @dfn{initial} frame or the
7403 @dfn{outermost} frame. Each time a function is called, a new frame is
7404 made. Each time a function returns, the frame for that function invocation
7405 is eliminated. If a function is recursive, there can be many frames for
7406 the same function. The frame for the function in which execution is
7407 actually occurring is called the @dfn{innermost} frame. This is the most
7408 recently created of all the stack frames that still exist.
7410 @cindex frame pointer
7411 Inside your program, stack frames are identified by their addresses. A
7412 stack frame consists of many bytes, each of which has its own address; each
7413 kind of computer has a convention for choosing one byte whose
7414 address serves as the address of the frame. Usually this address is kept
7415 in a register called the @dfn{frame pointer register}
7416 (@pxref{Registers, $fp}) while execution is going on in that frame.
7419 @cindex frame number
7420 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7421 number that is zero for the innermost frame, one for the frame that
7422 called it, and so on upward. These level numbers give you a way of
7423 designating stack frames in @value{GDBN} commands. The terms
7424 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7425 describe this number.
7427 @c The -fomit-frame-pointer below perennially causes hbox overflow
7428 @c underflow problems.
7429 @cindex frameless execution
7430 Some compilers provide a way to compile functions so that they operate
7431 without stack frames. (For example, the @value{NGCC} option
7433 @samp{-fomit-frame-pointer}
7435 generates functions without a frame.)
7436 This is occasionally done with heavily used library functions to save
7437 the frame setup time. @value{GDBN} has limited facilities for dealing
7438 with these function invocations. If the innermost function invocation
7439 has no stack frame, @value{GDBN} nevertheless regards it as though
7440 it had a separate frame, which is numbered zero as usual, allowing
7441 correct tracing of the function call chain. However, @value{GDBN} has
7442 no provision for frameless functions elsewhere in the stack.
7448 @cindex call stack traces
7449 A backtrace is a summary of how your program got where it is. It shows one
7450 line per frame, for many frames, starting with the currently executing
7451 frame (frame zero), followed by its caller (frame one), and on up the
7454 @anchor{backtrace-command}
7456 @kindex bt @r{(@code{backtrace})}
7457 To print a backtrace of the entire stack, use the @code{backtrace}
7458 command, or its alias @code{bt}. This command will print one line per
7459 frame for frames in the stack. By default, all stack frames are
7460 printed. You can stop the backtrace at any time by typing the system
7461 interrupt character, normally @kbd{Ctrl-c}.
7464 @item backtrace [@var{args}@dots{}]
7465 @itemx bt [@var{args}@dots{}]
7466 Print the backtrace of the entire stack. The optional @var{args} can
7467 be one of the following:
7472 Print only the innermost @var{n} frames, where @var{n} is a positive
7477 Print only the outermost @var{n} frames, where @var{n} is a positive
7481 Print the values of the local variables also. This can be combined
7482 with a number to limit the number of frames shown.
7485 Do not run Python frame filters on this backtrace. @xref{Frame
7486 Filter API}, for more information. Additionally use @ref{disable
7487 frame-filter all} to turn off all frame filters. This is only
7488 relevant when @value{GDBN} has been configured with @code{Python}
7492 A Python frame filter might decide to ``elide'' some frames. Normally
7493 such elided frames are still printed, but they are indented relative
7494 to the filtered frames that cause them to be elided. The @code{hide}
7495 option causes elided frames to not be printed at all.
7501 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7502 are additional aliases for @code{backtrace}.
7504 @cindex multiple threads, backtrace
7505 In a multi-threaded program, @value{GDBN} by default shows the
7506 backtrace only for the current thread. To display the backtrace for
7507 several or all of the threads, use the command @code{thread apply}
7508 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7509 apply all backtrace}, @value{GDBN} will display the backtrace for all
7510 the threads; this is handy when you debug a core dump of a
7511 multi-threaded program.
7513 Each line in the backtrace shows the frame number and the function name.
7514 The program counter value is also shown---unless you use @code{set
7515 print address off}. The backtrace also shows the source file name and
7516 line number, as well as the arguments to the function. The program
7517 counter value is omitted if it is at the beginning of the code for that
7520 Here is an example of a backtrace. It was made with the command
7521 @samp{bt 3}, so it shows the innermost three frames.
7525 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7527 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7528 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7530 (More stack frames follow...)
7535 The display for frame zero does not begin with a program counter
7536 value, indicating that your program has stopped at the beginning of the
7537 code for line @code{993} of @code{builtin.c}.
7540 The value of parameter @code{data} in frame 1 has been replaced by
7541 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7542 only if it is a scalar (integer, pointer, enumeration, etc). See command
7543 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7544 on how to configure the way function parameter values are printed.
7546 @cindex optimized out, in backtrace
7547 @cindex function call arguments, optimized out
7548 If your program was compiled with optimizations, some compilers will
7549 optimize away arguments passed to functions if those arguments are
7550 never used after the call. Such optimizations generate code that
7551 passes arguments through registers, but doesn't store those arguments
7552 in the stack frame. @value{GDBN} has no way of displaying such
7553 arguments in stack frames other than the innermost one. Here's what
7554 such a backtrace might look like:
7558 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7560 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7561 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7563 (More stack frames follow...)
7568 The values of arguments that were not saved in their stack frames are
7569 shown as @samp{<optimized out>}.
7571 If you need to display the values of such optimized-out arguments,
7572 either deduce that from other variables whose values depend on the one
7573 you are interested in, or recompile without optimizations.
7575 @cindex backtrace beyond @code{main} function
7576 @cindex program entry point
7577 @cindex startup code, and backtrace
7578 Most programs have a standard user entry point---a place where system
7579 libraries and startup code transition into user code. For C this is
7580 @code{main}@footnote{
7581 Note that embedded programs (the so-called ``free-standing''
7582 environment) are not required to have a @code{main} function as the
7583 entry point. They could even have multiple entry points.}.
7584 When @value{GDBN} finds the entry function in a backtrace
7585 it will terminate the backtrace, to avoid tracing into highly
7586 system-specific (and generally uninteresting) code.
7588 If you need to examine the startup code, or limit the number of levels
7589 in a backtrace, you can change this behavior:
7592 @item set backtrace past-main
7593 @itemx set backtrace past-main on
7594 @kindex set backtrace
7595 Backtraces will continue past the user entry point.
7597 @item set backtrace past-main off
7598 Backtraces will stop when they encounter the user entry point. This is the
7601 @item show backtrace past-main
7602 @kindex show backtrace
7603 Display the current user entry point backtrace policy.
7605 @item set backtrace past-entry
7606 @itemx set backtrace past-entry on
7607 Backtraces will continue past the internal entry point of an application.
7608 This entry point is encoded by the linker when the application is built,
7609 and is likely before the user entry point @code{main} (or equivalent) is called.
7611 @item set backtrace past-entry off
7612 Backtraces will stop when they encounter the internal entry point of an
7613 application. This is the default.
7615 @item show backtrace past-entry
7616 Display the current internal entry point backtrace policy.
7618 @item set backtrace limit @var{n}
7619 @itemx set backtrace limit 0
7620 @itemx set backtrace limit unlimited
7621 @cindex backtrace limit
7622 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7623 or zero means unlimited levels.
7625 @item show backtrace limit
7626 Display the current limit on backtrace levels.
7629 You can control how file names are displayed.
7632 @item set filename-display
7633 @itemx set filename-display relative
7634 @cindex filename-display
7635 Display file names relative to the compilation directory. This is the default.
7637 @item set filename-display basename
7638 Display only basename of a filename.
7640 @item set filename-display absolute
7641 Display an absolute filename.
7643 @item show filename-display
7644 Show the current way to display filenames.
7648 @section Selecting a Frame
7650 Most commands for examining the stack and other data in your program work on
7651 whichever stack frame is selected at the moment. Here are the commands for
7652 selecting a stack frame; all of them finish by printing a brief description
7653 of the stack frame just selected.
7656 @kindex frame@r{, selecting}
7657 @kindex f @r{(@code{frame})}
7658 @item frame @r{[} @var{frame-selection-spec} @r{]}
7659 @item f @r{[} @var{frame-selection-spec} @r{]}
7660 The @command{frame} command allows different stack frames to be
7661 selected. The @var{frame-selection-spec} can be any of the following:
7666 @item level @var{num}
7667 Select frame level @var{num}. Recall that frame zero is the innermost
7668 (currently executing) frame, frame one is the frame that called the
7669 innermost one, and so on. The highest level frame is usually the one
7672 As this is the most common method of navigating the frame stack, the
7673 string @command{level} can be omitted. For example, the following two
7674 commands are equivalent:
7677 (@value{GDBP}) frame 3
7678 (@value{GDBP}) frame level 3
7681 @kindex frame address
7682 @item address @var{stack-address}
7683 Select the frame with stack address @var{stack-address}. The
7684 @var{stack-address} for a frame can be seen in the output of
7685 @command{info frame}, for example:
7689 Stack level 1, frame at 0x7fffffffda30:
7690 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7691 tail call frame, caller of frame at 0x7fffffffda30
7692 source language c++.
7693 Arglist at unknown address.
7694 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7697 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7698 indicated by the line:
7701 Stack level 1, frame at 0x7fffffffda30:
7704 @kindex frame function
7705 @item function @var{function-name}
7706 Select the stack frame for function @var{function-name}. If there are
7707 multiple stack frames for function @var{function-name} then the inner
7708 most stack frame is selected.
7711 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7712 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7713 viewed has stack address @var{stack-addr}, and optionally, a program
7714 counter address of @var{pc-addr}.
7716 This is useful mainly if the chaining of stack frames has been
7717 damaged by a bug, making it impossible for @value{GDBN} to assign
7718 numbers properly to all frames. In addition, this can be useful
7719 when your program has multiple stacks and switches between them.
7721 When viewing a frame outside the current backtrace using
7722 @command{frame view} then you can always return to the original
7723 stack using one of the previous stack frame selection instructions,
7724 for example @command{frame level 0}.
7730 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7731 numbers @var{n}, this advances toward the outermost frame, to higher
7732 frame numbers, to frames that have existed longer.
7735 @kindex do @r{(@code{down})}
7737 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7738 positive numbers @var{n}, this advances toward the innermost frame, to
7739 lower frame numbers, to frames that were created more recently.
7740 You may abbreviate @code{down} as @code{do}.
7743 All of these commands end by printing two lines of output describing the
7744 frame. The first line shows the frame number, the function name, the
7745 arguments, and the source file and line number of execution in that
7746 frame. The second line shows the text of that source line.
7754 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7756 10 read_input_file (argv[i]);
7760 After such a printout, the @code{list} command with no arguments
7761 prints ten lines centered on the point of execution in the frame.
7762 You can also edit the program at the point of execution with your favorite
7763 editing program by typing @code{edit}.
7764 @xref{List, ,Printing Source Lines},
7768 @kindex select-frame
7769 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7770 The @code{select-frame} command is a variant of @code{frame} that does
7771 not display the new frame after selecting it. This command is
7772 intended primarily for use in @value{GDBN} command scripts, where the
7773 output might be unnecessary and distracting. The
7774 @var{frame-selection-spec} is as for the @command{frame} command
7775 described in @ref{Selection, ,Selecting a Frame}.
7777 @kindex down-silently
7779 @item up-silently @var{n}
7780 @itemx down-silently @var{n}
7781 These two commands are variants of @code{up} and @code{down},
7782 respectively; they differ in that they do their work silently, without
7783 causing display of the new frame. They are intended primarily for use
7784 in @value{GDBN} command scripts, where the output might be unnecessary and
7789 @section Information About a Frame
7791 There are several other commands to print information about the selected
7797 When used without any argument, this command does not change which
7798 frame is selected, but prints a brief description of the currently
7799 selected stack frame. It can be abbreviated @code{f}. With an
7800 argument, this command is used to select a stack frame.
7801 @xref{Selection, ,Selecting a Frame}.
7804 @kindex info f @r{(@code{info frame})}
7807 This command prints a verbose description of the selected stack frame,
7812 the address of the frame
7814 the address of the next frame down (called by this frame)
7816 the address of the next frame up (caller of this frame)
7818 the language in which the source code corresponding to this frame is written
7820 the address of the frame's arguments
7822 the address of the frame's local variables
7824 the program counter saved in it (the address of execution in the caller frame)
7826 which registers were saved in the frame
7829 @noindent The verbose description is useful when
7830 something has gone wrong that has made the stack format fail to fit
7831 the usual conventions.
7833 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7834 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7835 Print a verbose description of the frame selected by
7836 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7837 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7838 a Frame}). The selected frame remains unchanged by this command.
7841 @item info args [-q]
7842 Print the arguments of the selected frame, each on a separate line.
7844 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7845 printing header information and messages explaining why no argument
7848 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7849 Like @kbd{info args}, but only print the arguments selected
7850 with the provided regexp(s).
7852 If @var{regexp} is provided, print only the arguments whose names
7853 match the regular expression @var{regexp}.
7855 If @var{type_regexp} is provided, print only the arguments whose
7856 types, as printed by the @code{whatis} command, match
7857 the regular expression @var{type_regexp}.
7858 If @var{type_regexp} contains space(s), it should be enclosed in
7859 quote characters. If needed, use backslash to escape the meaning
7860 of special characters or quotes.
7862 If both @var{regexp} and @var{type_regexp} are provided, an argument
7863 is printed only if its name matches @var{regexp} and its type matches
7866 @item info locals [-q]
7868 Print the local variables of the selected frame, each on a separate
7869 line. These are all variables (declared either static or automatic)
7870 accessible at the point of execution of the selected frame.
7872 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7873 printing header information and messages explaining why no local variables
7876 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7877 Like @kbd{info locals}, but only print the local variables selected
7878 with the provided regexp(s).
7880 If @var{regexp} is provided, print only the local variables whose names
7881 match the regular expression @var{regexp}.
7883 If @var{type_regexp} is provided, print only the local variables whose
7884 types, as printed by the @code{whatis} command, match
7885 the regular expression @var{type_regexp}.
7886 If @var{type_regexp} contains space(s), it should be enclosed in
7887 quote characters. If needed, use backslash to escape the meaning
7888 of special characters or quotes.
7890 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7891 is printed only if its name matches @var{regexp} and its type matches
7894 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7895 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7896 For example, your program might use Resource Acquisition Is
7897 Initialization types (RAII) such as @code{lock_something_t}: each
7898 local variable of type @code{lock_something_t} automatically places a
7899 lock that is destroyed when the variable goes out of scope. You can
7900 then list all acquired locks in your program by doing
7902 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7905 or the equivalent shorter form
7907 tfaas i lo -q -t lock_something_t
7913 @section Applying a Command to Several Frames.
7915 @cindex apply command to several frames
7917 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7918 The @code{frame apply} command allows you to apply the named
7919 @var{command} to one or more frames.
7923 Specify @code{all} to apply @var{command} to all frames.
7926 Use @var{count} to apply @var{command} to the innermost @var{count}
7927 frames, where @var{count} is a positive number.
7930 Use @var{-count} to apply @var{command} to the outermost @var{count}
7931 frames, where @var{count} is a positive number.
7934 Use @code{level} to apply @var{command} to the set of frames identified
7935 by the @var{level} list. @var{level} is a frame level or a range of frame
7936 levels as @var{level1}-@var{level2}. The frame level is the number shown
7937 in the first field of the @samp{backtrace} command output.
7938 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7939 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7945 Note that the frames on which @code{frame apply} applies a command are
7946 also influenced by the @code{set backtrace} settings such as @code{set
7947 backtrace past-main} and @code{set backtrace limit N}. See
7948 @xref{Backtrace,,Backtraces}.
7950 The @var{flag} arguments control what output to produce and how to handle
7951 errors raised when applying @var{command} to a frame. @var{flag}
7952 must start with a @code{-} directly followed by one letter in
7953 @code{qcs}. If several flags are provided, they must be given
7954 individually, such as @code{-c -q}.
7956 By default, @value{GDBN} displays some frame information before the
7957 output produced by @var{command}, and an error raised during the
7958 execution of a @var{command} will abort @code{frame apply}. The
7959 following flags can be used to fine-tune this behavior:
7963 The flag @code{-c}, which stands for @samp{continue}, causes any
7964 errors in @var{command} to be displayed, and the execution of
7965 @code{frame apply} then continues.
7967 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7968 or empty output produced by a @var{command} to be silently ignored.
7969 That is, the execution continues, but the frame information and errors
7972 The flag @code{-q} (@samp{quiet}) disables printing the frame
7976 The following example shows how the flags @code{-c} and @code{-s} are
7977 working when applying the command @code{p j} to all frames, where
7978 variable @code{j} can only be successfully printed in the outermost
7979 @code{#1 main} frame.
7983 (gdb) frame apply all p j
7984 #0 some_function (i=5) at fun.c:4
7985 No symbol "j" in current context.
7986 (gdb) frame apply all -c p j
7987 #0 some_function (i=5) at fun.c:4
7988 No symbol "j" in current context.
7989 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7991 (gdb) frame apply all -s p j
7992 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7998 By default, @samp{frame apply}, prints the frame location
7999 information before the command output:
8003 (gdb) frame apply all p $sp
8004 #0 some_function (i=5) at fun.c:4
8005 $4 = (void *) 0xffffd1e0
8006 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8007 $5 = (void *) 0xffffd1f0
8012 If flag @code{-q} is given, no frame information is printed:
8015 (gdb) frame apply all -q p $sp
8016 $12 = (void *) 0xffffd1e0
8017 $13 = (void *) 0xffffd1f0
8025 @cindex apply a command to all frames (ignoring errors and empty output)
8026 @item faas @var{command}
8027 Shortcut for @code{frame apply all -s @var{command}}.
8028 Applies @var{command} on all frames, ignoring errors and empty output.
8030 It can for example be used to print a local variable or a function
8031 argument without knowing the frame where this variable or argument
8034 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8037 Note that the command @code{tfaas @var{command}} applies @var{command}
8038 on all frames of all threads. See @xref{Threads,,Threads}.
8042 @node Frame Filter Management
8043 @section Management of Frame Filters.
8044 @cindex managing frame filters
8046 Frame filters are Python based utilities to manage and decorate the
8047 output of frames. @xref{Frame Filter API}, for further information.
8049 Managing frame filters is performed by several commands available
8050 within @value{GDBN}, detailed here.
8053 @kindex info frame-filter
8054 @item info frame-filter
8055 Print a list of installed frame filters from all dictionaries, showing
8056 their name, priority and enabled status.
8058 @kindex disable frame-filter
8059 @anchor{disable frame-filter all}
8060 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8061 Disable a frame filter in the dictionary matching
8062 @var{filter-dictionary} and @var{filter-name}. The
8063 @var{filter-dictionary} may be @code{all}, @code{global},
8064 @code{progspace}, or the name of the object file where the frame filter
8065 dictionary resides. When @code{all} is specified, all frame filters
8066 across all dictionaries are disabled. The @var{filter-name} is the name
8067 of the frame filter and is used when @code{all} is not the option for
8068 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8069 may be enabled again later.
8071 @kindex enable frame-filter
8072 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8073 Enable a frame filter in the dictionary matching
8074 @var{filter-dictionary} and @var{filter-name}. The
8075 @var{filter-dictionary} may be @code{all}, @code{global},
8076 @code{progspace} or the name of the object file where the frame filter
8077 dictionary resides. When @code{all} is specified, all frame filters across
8078 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8079 filter and is used when @code{all} is not the option for
8080 @var{filter-dictionary}.
8085 (gdb) info frame-filter
8087 global frame-filters:
8088 Priority Enabled Name
8089 1000 No PrimaryFunctionFilter
8092 progspace /build/test frame-filters:
8093 Priority Enabled Name
8094 100 Yes ProgspaceFilter
8096 objfile /build/test frame-filters:
8097 Priority Enabled Name
8098 999 Yes BuildProgra Filter
8100 (gdb) disable frame-filter /build/test BuildProgramFilter
8101 (gdb) info frame-filter
8103 global frame-filters:
8104 Priority Enabled Name
8105 1000 No PrimaryFunctionFilter
8108 progspace /build/test frame-filters:
8109 Priority Enabled Name
8110 100 Yes ProgspaceFilter
8112 objfile /build/test frame-filters:
8113 Priority Enabled Name
8114 999 No BuildProgramFilter
8116 (gdb) enable frame-filter global PrimaryFunctionFilter
8117 (gdb) info frame-filter
8119 global frame-filters:
8120 Priority Enabled Name
8121 1000 Yes PrimaryFunctionFilter
8124 progspace /build/test frame-filters:
8125 Priority Enabled Name
8126 100 Yes ProgspaceFilter
8128 objfile /build/test frame-filters:
8129 Priority Enabled Name
8130 999 No BuildProgramFilter
8133 @kindex set frame-filter priority
8134 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8135 Set the @var{priority} of a frame filter in the dictionary matching
8136 @var{filter-dictionary}, and the frame filter name matching
8137 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8138 @code{progspace} or the name of the object file where the frame filter
8139 dictionary resides. The @var{priority} is an integer.
8141 @kindex show frame-filter priority
8142 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8143 Show the @var{priority} of a frame filter in the dictionary matching
8144 @var{filter-dictionary}, and the frame filter name matching
8145 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8146 @code{progspace} or the name of the object file where the frame filter
8152 (gdb) info frame-filter
8154 global frame-filters:
8155 Priority Enabled Name
8156 1000 Yes PrimaryFunctionFilter
8159 progspace /build/test frame-filters:
8160 Priority Enabled Name
8161 100 Yes ProgspaceFilter
8163 objfile /build/test frame-filters:
8164 Priority Enabled Name
8165 999 No BuildProgramFilter
8167 (gdb) set frame-filter priority global Reverse 50
8168 (gdb) info frame-filter
8170 global frame-filters:
8171 Priority Enabled Name
8172 1000 Yes PrimaryFunctionFilter
8175 progspace /build/test frame-filters:
8176 Priority Enabled Name
8177 100 Yes ProgspaceFilter
8179 objfile /build/test frame-filters:
8180 Priority Enabled Name
8181 999 No BuildProgramFilter
8186 @chapter Examining Source Files
8188 @value{GDBN} can print parts of your program's source, since the debugging
8189 information recorded in the program tells @value{GDBN} what source files were
8190 used to build it. When your program stops, @value{GDBN} spontaneously prints
8191 the line where it stopped. Likewise, when you select a stack frame
8192 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8193 execution in that frame has stopped. You can print other portions of
8194 source files by explicit command.
8196 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8197 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8198 @value{GDBN} under @sc{gnu} Emacs}.
8201 * List:: Printing source lines
8202 * Specify Location:: How to specify code locations
8203 * Edit:: Editing source files
8204 * Search:: Searching source files
8205 * Source Path:: Specifying source directories
8206 * Machine Code:: Source and machine code
8210 @section Printing Source Lines
8213 @kindex l @r{(@code{list})}
8214 To print lines from a source file, use the @code{list} command
8215 (abbreviated @code{l}). By default, ten lines are printed.
8216 There are several ways to specify what part of the file you want to
8217 print; see @ref{Specify Location}, for the full list.
8219 Here are the forms of the @code{list} command most commonly used:
8222 @item list @var{linenum}
8223 Print lines centered around line number @var{linenum} in the
8224 current source file.
8226 @item list @var{function}
8227 Print lines centered around the beginning of function
8231 Print more lines. If the last lines printed were printed with a
8232 @code{list} command, this prints lines following the last lines
8233 printed; however, if the last line printed was a solitary line printed
8234 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8235 Stack}), this prints lines centered around that line.
8238 Print lines just before the lines last printed.
8241 @cindex @code{list}, how many lines to display
8242 By default, @value{GDBN} prints ten source lines with any of these forms of
8243 the @code{list} command. You can change this using @code{set listsize}:
8246 @kindex set listsize
8247 @item set listsize @var{count}
8248 @itemx set listsize unlimited
8249 Make the @code{list} command display @var{count} source lines (unless
8250 the @code{list} argument explicitly specifies some other number).
8251 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8253 @kindex show listsize
8255 Display the number of lines that @code{list} prints.
8258 Repeating a @code{list} command with @key{RET} discards the argument,
8259 so it is equivalent to typing just @code{list}. This is more useful
8260 than listing the same lines again. An exception is made for an
8261 argument of @samp{-}; that argument is preserved in repetition so that
8262 each repetition moves up in the source file.
8264 In general, the @code{list} command expects you to supply zero, one or two
8265 @dfn{locations}. Locations specify source lines; there are several ways
8266 of writing them (@pxref{Specify Location}), but the effect is always
8267 to specify some source line.
8269 Here is a complete description of the possible arguments for @code{list}:
8272 @item list @var{location}
8273 Print lines centered around the line specified by @var{location}.
8275 @item list @var{first},@var{last}
8276 Print lines from @var{first} to @var{last}. Both arguments are
8277 locations. When a @code{list} command has two locations, and the
8278 source file of the second location is omitted, this refers to
8279 the same source file as the first location.
8281 @item list ,@var{last}
8282 Print lines ending with @var{last}.
8284 @item list @var{first},
8285 Print lines starting with @var{first}.
8288 Print lines just after the lines last printed.
8291 Print lines just before the lines last printed.
8294 As described in the preceding table.
8297 @node Specify Location
8298 @section Specifying a Location
8299 @cindex specifying location
8301 @cindex source location
8304 * Linespec Locations:: Linespec locations
8305 * Explicit Locations:: Explicit locations
8306 * Address Locations:: Address locations
8309 Several @value{GDBN} commands accept arguments that specify a location
8310 of your program's code. Since @value{GDBN} is a source-level
8311 debugger, a location usually specifies some line in the source code.
8312 Locations may be specified using three different formats:
8313 linespec locations, explicit locations, or address locations.
8315 @node Linespec Locations
8316 @subsection Linespec Locations
8317 @cindex linespec locations
8319 A @dfn{linespec} is a colon-separated list of source location parameters such
8320 as file name, function name, etc. Here are all the different ways of
8321 specifying a linespec:
8325 Specifies the line number @var{linenum} of the current source file.
8328 @itemx +@var{offset}
8329 Specifies the line @var{offset} lines before or after the @dfn{current
8330 line}. For the @code{list} command, the current line is the last one
8331 printed; for the breakpoint commands, this is the line at which
8332 execution stopped in the currently selected @dfn{stack frame}
8333 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8334 used as the second of the two linespecs in a @code{list} command,
8335 this specifies the line @var{offset} lines up or down from the first
8338 @item @var{filename}:@var{linenum}
8339 Specifies the line @var{linenum} in the source file @var{filename}.
8340 If @var{filename} is a relative file name, then it will match any
8341 source file name with the same trailing components. For example, if
8342 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8343 name of @file{/build/trunk/gcc/expr.c}, but not
8344 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8346 @item @var{function}
8347 Specifies the line that begins the body of the function @var{function}.
8348 For example, in C, this is the line with the open brace.
8350 By default, in C@t{++} and Ada, @var{function} is interpreted as
8351 specifying all functions named @var{function} in all scopes. For
8352 C@t{++}, this means in all namespaces and classes. For Ada, this
8353 means in all packages.
8355 For example, assuming a program with C@t{++} symbols named
8356 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8357 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8359 Commands that accept a linespec let you override this with the
8360 @code{-qualified} option. For example, @w{@kbd{break -qualified
8361 func}} sets a breakpoint on a free-function named @code{func} ignoring
8362 any C@t{++} class methods and namespace functions called @code{func}.
8364 @xref{Explicit Locations}.
8366 @item @var{function}:@var{label}
8367 Specifies the line where @var{label} appears in @var{function}.
8369 @item @var{filename}:@var{function}
8370 Specifies the line that begins the body of the function @var{function}
8371 in the file @var{filename}. You only need the file name with a
8372 function name to avoid ambiguity when there are identically named
8373 functions in different source files.
8376 Specifies the line at which the label named @var{label} appears
8377 in the function corresponding to the currently selected stack frame.
8378 If there is no current selected stack frame (for instance, if the inferior
8379 is not running), then @value{GDBN} will not search for a label.
8381 @cindex breakpoint at static probe point
8382 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8383 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8384 applications to embed static probes. @xref{Static Probe Points}, for more
8385 information on finding and using static probes. This form of linespec
8386 specifies the location of such a static probe.
8388 If @var{objfile} is given, only probes coming from that shared library
8389 or executable matching @var{objfile} as a regular expression are considered.
8390 If @var{provider} is given, then only probes from that provider are considered.
8391 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8392 each one of those probes.
8395 @node Explicit Locations
8396 @subsection Explicit Locations
8397 @cindex explicit locations
8399 @dfn{Explicit locations} allow the user to directly specify the source
8400 location's parameters using option-value pairs.
8402 Explicit locations are useful when several functions, labels, or
8403 file names have the same name (base name for files) in the program's
8404 sources. In these cases, explicit locations point to the source
8405 line you meant more accurately and unambiguously. Also, using
8406 explicit locations might be faster in large programs.
8408 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8409 defined in the file named @file{foo} or the label @code{bar} in a function
8410 named @code{foo}. @value{GDBN} must search either the file system or
8411 the symbol table to know.
8413 The list of valid explicit location options is summarized in the
8417 @item -source @var{filename}
8418 The value specifies the source file name. To differentiate between
8419 files with the same base name, prepend as many directories as is necessary
8420 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8421 @value{GDBN} will use the first file it finds with the given base
8422 name. This option requires the use of either @code{-function} or @code{-line}.
8424 @item -function @var{function}
8425 The value specifies the name of a function. Operations
8426 on function locations unmodified by other options (such as @code{-label}
8427 or @code{-line}) refer to the line that begins the body of the function.
8428 In C, for example, this is the line with the open brace.
8430 By default, in C@t{++} and Ada, @var{function} is interpreted as
8431 specifying all functions named @var{function} in all scopes. For
8432 C@t{++}, this means in all namespaces and classes. For Ada, this
8433 means in all packages.
8435 For example, assuming a program with C@t{++} symbols named
8436 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8437 -function func}} and @w{@kbd{break -function B::func}} set a
8438 breakpoint on both symbols.
8440 You can use the @kbd{-qualified} flag to override this (see below).
8444 This flag makes @value{GDBN} interpret a function name specified with
8445 @kbd{-function} as a complete fully-qualified name.
8447 For example, assuming a C@t{++} program with symbols named
8448 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8449 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8451 (Note: the @kbd{-qualified} option can precede a linespec as well
8452 (@pxref{Linespec Locations}), so the particular example above could be
8453 simplified as @w{@kbd{break -qualified B::func}}.)
8455 @item -label @var{label}
8456 The value specifies the name of a label. When the function
8457 name is not specified, the label is searched in the function of the currently
8458 selected stack frame.
8460 @item -line @var{number}
8461 The value specifies a line offset for the location. The offset may either
8462 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8463 the command. When specified without any other options, the line offset is
8464 relative to the current line.
8467 Explicit location options may be abbreviated by omitting any non-unique
8468 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8470 @node Address Locations
8471 @subsection Address Locations
8472 @cindex address locations
8474 @dfn{Address locations} indicate a specific program address. They have
8475 the generalized form *@var{address}.
8477 For line-oriented commands, such as @code{list} and @code{edit}, this
8478 specifies a source line that contains @var{address}. For @code{break} and
8479 other breakpoint-oriented commands, this can be used to set breakpoints in
8480 parts of your program which do not have debugging information or
8483 Here @var{address} may be any expression valid in the current working
8484 language (@pxref{Languages, working language}) that specifies a code
8485 address. In addition, as a convenience, @value{GDBN} extends the
8486 semantics of expressions used in locations to cover several situations
8487 that frequently occur during debugging. Here are the various forms
8491 @item @var{expression}
8492 Any expression valid in the current working language.
8494 @item @var{funcaddr}
8495 An address of a function or procedure derived from its name. In C,
8496 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8497 simply the function's name @var{function} (and actually a special case
8498 of a valid expression). In Pascal and Modula-2, this is
8499 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8500 (although the Pascal form also works).
8502 This form specifies the address of the function's first instruction,
8503 before the stack frame and arguments have been set up.
8505 @item '@var{filename}':@var{funcaddr}
8506 Like @var{funcaddr} above, but also specifies the name of the source
8507 file explicitly. This is useful if the name of the function does not
8508 specify the function unambiguously, e.g., if there are several
8509 functions with identical names in different source files.
8513 @section Editing Source Files
8514 @cindex editing source files
8517 @kindex e @r{(@code{edit})}
8518 To edit the lines in a source file, use the @code{edit} command.
8519 The editing program of your choice
8520 is invoked with the current line set to
8521 the active line in the program.
8522 Alternatively, there are several ways to specify what part of the file you
8523 want to print if you want to see other parts of the program:
8526 @item edit @var{location}
8527 Edit the source file specified by @code{location}. Editing starts at
8528 that @var{location}, e.g., at the specified source line of the
8529 specified file. @xref{Specify Location}, for all the possible forms
8530 of the @var{location} argument; here are the forms of the @code{edit}
8531 command most commonly used:
8534 @item edit @var{number}
8535 Edit the current source file with @var{number} as the active line number.
8537 @item edit @var{function}
8538 Edit the file containing @var{function} at the beginning of its definition.
8543 @subsection Choosing your Editor
8544 You can customize @value{GDBN} to use any editor you want
8546 The only restriction is that your editor (say @code{ex}), recognizes the
8547 following command-line syntax:
8549 ex +@var{number} file
8551 The optional numeric value +@var{number} specifies the number of the line in
8552 the file where to start editing.}.
8553 By default, it is @file{@value{EDITOR}}, but you can change this
8554 by setting the environment variable @code{EDITOR} before using
8555 @value{GDBN}. For example, to configure @value{GDBN} to use the
8556 @code{vi} editor, you could use these commands with the @code{sh} shell:
8562 or in the @code{csh} shell,
8564 setenv EDITOR /usr/bin/vi
8569 @section Searching Source Files
8570 @cindex searching source files
8572 There are two commands for searching through the current source file for a
8577 @kindex forward-search
8578 @kindex fo @r{(@code{forward-search})}
8579 @item forward-search @var{regexp}
8580 @itemx search @var{regexp}
8581 The command @samp{forward-search @var{regexp}} checks each line,
8582 starting with the one following the last line listed, for a match for
8583 @var{regexp}. It lists the line that is found. You can use the
8584 synonym @samp{search @var{regexp}} or abbreviate the command name as
8587 @kindex reverse-search
8588 @item reverse-search @var{regexp}
8589 The command @samp{reverse-search @var{regexp}} checks each line, starting
8590 with the one before the last line listed and going backward, for a match
8591 for @var{regexp}. It lists the line that is found. You can abbreviate
8592 this command as @code{rev}.
8596 @section Specifying Source Directories
8599 @cindex directories for source files
8600 Executable programs sometimes do not record the directories of the source
8601 files from which they were compiled, just the names. Even when they do,
8602 the directories could be moved between the compilation and your debugging
8603 session. @value{GDBN} has a list of directories to search for source files;
8604 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8605 it tries all the directories in the list, in the order they are present
8606 in the list, until it finds a file with the desired name.
8608 For example, suppose an executable references the file
8609 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8610 @file{/mnt/cross}. The file is first looked up literally; if this
8611 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8612 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8613 message is printed. @value{GDBN} does not look up the parts of the
8614 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8615 Likewise, the subdirectories of the source path are not searched: if
8616 the source path is @file{/mnt/cross}, and the binary refers to
8617 @file{foo.c}, @value{GDBN} would not find it under
8618 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8620 Plain file names, relative file names with leading directories, file
8621 names containing dots, etc.@: are all treated as described above; for
8622 instance, if the source path is @file{/mnt/cross}, and the source file
8623 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8624 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8625 that---@file{/mnt/cross/foo.c}.
8627 Note that the executable search path is @emph{not} used to locate the
8630 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8631 any information it has cached about where source files are found and where
8632 each line is in the file.
8636 When you start @value{GDBN}, its source path includes only @samp{cdir}
8637 and @samp{cwd}, in that order.
8638 To add other directories, use the @code{directory} command.
8640 The search path is used to find both program source files and @value{GDBN}
8641 script files (read using the @samp{-command} option and @samp{source} command).
8643 In addition to the source path, @value{GDBN} provides a set of commands
8644 that manage a list of source path substitution rules. A @dfn{substitution
8645 rule} specifies how to rewrite source directories stored in the program's
8646 debug information in case the sources were moved to a different
8647 directory between compilation and debugging. A rule is made of
8648 two strings, the first specifying what needs to be rewritten in
8649 the path, and the second specifying how it should be rewritten.
8650 In @ref{set substitute-path}, we name these two parts @var{from} and
8651 @var{to} respectively. @value{GDBN} does a simple string replacement
8652 of @var{from} with @var{to} at the start of the directory part of the
8653 source file name, and uses that result instead of the original file
8654 name to look up the sources.
8656 Using the previous example, suppose the @file{foo-1.0} tree has been
8657 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8658 @value{GDBN} to replace @file{/usr/src} in all source path names with
8659 @file{/mnt/cross}. The first lookup will then be
8660 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8661 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8662 substitution rule, use the @code{set substitute-path} command
8663 (@pxref{set substitute-path}).
8665 To avoid unexpected substitution results, a rule is applied only if the
8666 @var{from} part of the directory name ends at a directory separator.
8667 For instance, a rule substituting @file{/usr/source} into
8668 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8669 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8670 is applied only at the beginning of the directory name, this rule will
8671 not be applied to @file{/root/usr/source/baz.c} either.
8673 In many cases, you can achieve the same result using the @code{directory}
8674 command. However, @code{set substitute-path} can be more efficient in
8675 the case where the sources are organized in a complex tree with multiple
8676 subdirectories. With the @code{directory} command, you need to add each
8677 subdirectory of your project. If you moved the entire tree while
8678 preserving its internal organization, then @code{set substitute-path}
8679 allows you to direct the debugger to all the sources with one single
8682 @code{set substitute-path} is also more than just a shortcut command.
8683 The source path is only used if the file at the original location no
8684 longer exists. On the other hand, @code{set substitute-path} modifies
8685 the debugger behavior to look at the rewritten location instead. So, if
8686 for any reason a source file that is not relevant to your executable is
8687 located at the original location, a substitution rule is the only
8688 method available to point @value{GDBN} at the new location.
8690 @cindex @samp{--with-relocated-sources}
8691 @cindex default source path substitution
8692 You can configure a default source path substitution rule by
8693 configuring @value{GDBN} with the
8694 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8695 should be the name of a directory under @value{GDBN}'s configured
8696 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8697 directory names in debug information under @var{dir} will be adjusted
8698 automatically if the installed @value{GDBN} is moved to a new
8699 location. This is useful if @value{GDBN}, libraries or executables
8700 with debug information and corresponding source code are being moved
8704 @item directory @var{dirname} @dots{}
8705 @item dir @var{dirname} @dots{}
8706 Add directory @var{dirname} to the front of the source path. Several
8707 directory names may be given to this command, separated by @samp{:}
8708 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8709 part of absolute file names) or
8710 whitespace. You may specify a directory that is already in the source
8711 path; this moves it forward, so @value{GDBN} searches it sooner.
8715 @vindex $cdir@r{, convenience variable}
8716 @vindex $cwd@r{, convenience variable}
8717 @cindex compilation directory
8718 @cindex current directory
8719 @cindex working directory
8720 @cindex directory, current
8721 @cindex directory, compilation
8722 You can use the string @samp{$cdir} to refer to the compilation
8723 directory (if one is recorded), and @samp{$cwd} to refer to the current
8724 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8725 tracks the current working directory as it changes during your @value{GDBN}
8726 session, while the latter is immediately expanded to the current
8727 directory at the time you add an entry to the source path.
8730 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8732 @c RET-repeat for @code{directory} is explicitly disabled, but since
8733 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8735 @item set directories @var{path-list}
8736 @kindex set directories
8737 Set the source path to @var{path-list}.
8738 @samp{$cdir:$cwd} are added if missing.
8740 @item show directories
8741 @kindex show directories
8742 Print the source path: show which directories it contains.
8744 @anchor{set substitute-path}
8745 @item set substitute-path @var{from} @var{to}
8746 @kindex set substitute-path
8747 Define a source path substitution rule, and add it at the end of the
8748 current list of existing substitution rules. If a rule with the same
8749 @var{from} was already defined, then the old rule is also deleted.
8751 For example, if the file @file{/foo/bar/baz.c} was moved to
8752 @file{/mnt/cross/baz.c}, then the command
8755 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8759 will tell @value{GDBN} to replace @samp{/foo/bar} with
8760 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8761 @file{baz.c} even though it was moved.
8763 In the case when more than one substitution rule have been defined,
8764 the rules are evaluated one by one in the order where they have been
8765 defined. The first one matching, if any, is selected to perform
8768 For instance, if we had entered the following commands:
8771 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8772 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8776 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8777 @file{/mnt/include/defs.h} by using the first rule. However, it would
8778 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8779 @file{/mnt/src/lib/foo.c}.
8782 @item unset substitute-path [path]
8783 @kindex unset substitute-path
8784 If a path is specified, search the current list of substitution rules
8785 for a rule that would rewrite that path. Delete that rule if found.
8786 A warning is emitted by the debugger if no rule could be found.
8788 If no path is specified, then all substitution rules are deleted.
8790 @item show substitute-path [path]
8791 @kindex show substitute-path
8792 If a path is specified, then print the source path substitution rule
8793 which would rewrite that path, if any.
8795 If no path is specified, then print all existing source path substitution
8800 If your source path is cluttered with directories that are no longer of
8801 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8802 versions of source. You can correct the situation as follows:
8806 Use @code{directory} with no argument to reset the source path to its default value.
8809 Use @code{directory} with suitable arguments to reinstall the
8810 directories you want in the source path. You can add all the
8811 directories in one command.
8815 @section Source and Machine Code
8816 @cindex source line and its code address
8818 You can use the command @code{info line} to map source lines to program
8819 addresses (and vice versa), and the command @code{disassemble} to display
8820 a range of addresses as machine instructions. You can use the command
8821 @code{set disassemble-next-line} to set whether to disassemble next
8822 source line when execution stops. When run under @sc{gnu} Emacs
8823 mode, the @code{info line} command causes the arrow to point to the
8824 line specified. Also, @code{info line} prints addresses in symbolic form as
8830 @itemx info line @var{location}
8831 Print the starting and ending addresses of the compiled code for
8832 source line @var{location}. You can specify source lines in any of
8833 the ways documented in @ref{Specify Location}. With no @var{location}
8834 information about the current source line is printed.
8837 For example, we can use @code{info line} to discover the location of
8838 the object code for the first line of function
8839 @code{m4_changequote}:
8842 (@value{GDBP}) info line m4_changequote
8843 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8844 ends at 0x6350 <m4_changequote+4>.
8848 @cindex code address and its source line
8849 We can also inquire (using @code{*@var{addr}} as the form for
8850 @var{location}) what source line covers a particular address:
8852 (@value{GDBP}) info line *0x63ff
8853 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8854 ends at 0x6404 <m4_changequote+184>.
8857 @cindex @code{$_} and @code{info line}
8858 @cindex @code{x} command, default address
8859 @kindex x@r{(examine), and} info line
8860 After @code{info line}, the default address for the @code{x} command
8861 is changed to the starting address of the line, so that @samp{x/i} is
8862 sufficient to begin examining the machine code (@pxref{Memory,
8863 ,Examining Memory}). Also, this address is saved as the value of the
8864 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8867 @cindex info line, repeated calls
8868 After @code{info line}, using @code{info line} again without
8869 specifying a location will display information about the next source
8874 @cindex assembly instructions
8875 @cindex instructions, assembly
8876 @cindex machine instructions
8877 @cindex listing machine instructions
8879 @itemx disassemble /m
8880 @itemx disassemble /s
8881 @itemx disassemble /r
8882 This specialized command dumps a range of memory as machine
8883 instructions. It can also print mixed source+disassembly by specifying
8884 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8885 as well as in symbolic form by specifying the @code{/r} modifier.
8886 The default memory range is the function surrounding the
8887 program counter of the selected frame. A single argument to this
8888 command is a program counter value; @value{GDBN} dumps the function
8889 surrounding this value. When two arguments are given, they should
8890 be separated by a comma, possibly surrounded by whitespace. The
8891 arguments specify a range of addresses to dump, in one of two forms:
8894 @item @var{start},@var{end}
8895 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8896 @item @var{start},+@var{length}
8897 the addresses from @var{start} (inclusive) to
8898 @code{@var{start}+@var{length}} (exclusive).
8902 When 2 arguments are specified, the name of the function is also
8903 printed (since there could be several functions in the given range).
8905 The argument(s) can be any expression yielding a numeric value, such as
8906 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8908 If the range of memory being disassembled contains current program counter,
8909 the instruction at that location is shown with a @code{=>} marker.
8912 The following example shows the disassembly of a range of addresses of
8913 HP PA-RISC 2.0 code:
8916 (@value{GDBP}) disas 0x32c4, 0x32e4
8917 Dump of assembler code from 0x32c4 to 0x32e4:
8918 0x32c4 <main+204>: addil 0,dp
8919 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8920 0x32cc <main+212>: ldil 0x3000,r31
8921 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8922 0x32d4 <main+220>: ldo 0(r31),rp
8923 0x32d8 <main+224>: addil -0x800,dp
8924 0x32dc <main+228>: ldo 0x588(r1),r26
8925 0x32e0 <main+232>: ldil 0x3000,r31
8926 End of assembler dump.
8929 Here is an example showing mixed source+assembly for Intel x86
8930 with @code{/m} or @code{/s}, when the program is stopped just after
8931 function prologue in a non-optimized function with no inline code.
8934 (@value{GDBP}) disas /m main
8935 Dump of assembler code for function main:
8937 0x08048330 <+0>: push %ebp
8938 0x08048331 <+1>: mov %esp,%ebp
8939 0x08048333 <+3>: sub $0x8,%esp
8940 0x08048336 <+6>: and $0xfffffff0,%esp
8941 0x08048339 <+9>: sub $0x10,%esp
8943 6 printf ("Hello.\n");
8944 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8945 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8949 0x08048348 <+24>: mov $0x0,%eax
8950 0x0804834d <+29>: leave
8951 0x0804834e <+30>: ret
8953 End of assembler dump.
8956 The @code{/m} option is deprecated as its output is not useful when
8957 there is either inlined code or re-ordered code.
8958 The @code{/s} option is the preferred choice.
8959 Here is an example for AMD x86-64 showing the difference between
8960 @code{/m} output and @code{/s} output.
8961 This example has one inline function defined in a header file,
8962 and the code is compiled with @samp{-O2} optimization.
8963 Note how the @code{/m} output is missing the disassembly of
8964 several instructions that are present in the @code{/s} output.
8994 (@value{GDBP}) disas /m main
8995 Dump of assembler code for function main:
8999 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9000 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9004 0x000000000040041d <+29>: xor %eax,%eax
9005 0x000000000040041f <+31>: retq
9006 0x0000000000400420 <+32>: add %eax,%eax
9007 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9009 End of assembler dump.
9010 (@value{GDBP}) disas /s main
9011 Dump of assembler code for function main:
9015 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9019 0x0000000000400406 <+6>: test %eax,%eax
9020 0x0000000000400408 <+8>: js 0x400420 <main+32>
9025 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9026 0x000000000040040d <+13>: test %eax,%eax
9027 0x000000000040040f <+15>: mov $0x1,%eax
9028 0x0000000000400414 <+20>: cmovne %edx,%eax
9032 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9036 0x000000000040041d <+29>: xor %eax,%eax
9037 0x000000000040041f <+31>: retq
9041 0x0000000000400420 <+32>: add %eax,%eax
9042 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9043 End of assembler dump.
9046 Here is another example showing raw instructions in hex for AMD x86-64,
9049 (gdb) disas /r 0x400281,+10
9050 Dump of assembler code from 0x400281 to 0x40028b:
9051 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9052 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9053 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9054 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9055 End of assembler dump.
9058 Addresses cannot be specified as a location (@pxref{Specify Location}).
9059 So, for example, if you want to disassemble function @code{bar}
9060 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9061 and not @samp{disassemble foo.c:bar}.
9063 Some architectures have more than one commonly-used set of instruction
9064 mnemonics or other syntax.
9066 For programs that were dynamically linked and use shared libraries,
9067 instructions that call functions or branch to locations in the shared
9068 libraries might show a seemingly bogus location---it's actually a
9069 location of the relocation table. On some architectures, @value{GDBN}
9070 might be able to resolve these to actual function names.
9073 @kindex set disassembler-options
9074 @cindex disassembler options
9075 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9076 This command controls the passing of target specific information to
9077 the disassembler. For a list of valid options, please refer to the
9078 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9079 manual and/or the output of @kbd{objdump --help}
9080 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9081 The default value is the empty string.
9083 If it is necessary to specify more than one disassembler option, then
9084 multiple options can be placed together into a comma separated list.
9085 Currently this command is only supported on targets ARM, MIPS, PowerPC
9088 @kindex show disassembler-options
9089 @item show disassembler-options
9090 Show the current setting of the disassembler options.
9094 @kindex set disassembly-flavor
9095 @cindex Intel disassembly flavor
9096 @cindex AT&T disassembly flavor
9097 @item set disassembly-flavor @var{instruction-set}
9098 Select the instruction set to use when disassembling the
9099 program via the @code{disassemble} or @code{x/i} commands.
9101 Currently this command is only defined for the Intel x86 family. You
9102 can set @var{instruction-set} to either @code{intel} or @code{att}.
9103 The default is @code{att}, the AT&T flavor used by default by Unix
9104 assemblers for x86-based targets.
9106 @kindex show disassembly-flavor
9107 @item show disassembly-flavor
9108 Show the current setting of the disassembly flavor.
9112 @kindex set disassemble-next-line
9113 @kindex show disassemble-next-line
9114 @item set disassemble-next-line
9115 @itemx show disassemble-next-line
9116 Control whether or not @value{GDBN} will disassemble the next source
9117 line or instruction when execution stops. If ON, @value{GDBN} will
9118 display disassembly of the next source line when execution of the
9119 program being debugged stops. This is @emph{in addition} to
9120 displaying the source line itself, which @value{GDBN} always does if
9121 possible. If the next source line cannot be displayed for some reason
9122 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9123 info in the debug info), @value{GDBN} will display disassembly of the
9124 next @emph{instruction} instead of showing the next source line. If
9125 AUTO, @value{GDBN} will display disassembly of next instruction only
9126 if the source line cannot be displayed. This setting causes
9127 @value{GDBN} to display some feedback when you step through a function
9128 with no line info or whose source file is unavailable. The default is
9129 OFF, which means never display the disassembly of the next line or
9135 @chapter Examining Data
9137 @cindex printing data
9138 @cindex examining data
9141 The usual way to examine data in your program is with the @code{print}
9142 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9143 evaluates and prints the value of an expression of the language your
9144 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9145 Different Languages}). It may also print the expression using a
9146 Python-based pretty-printer (@pxref{Pretty Printing}).
9149 @item print @var{expr}
9150 @itemx print /@var{f} @var{expr}
9151 @var{expr} is an expression (in the source language). By default the
9152 value of @var{expr} is printed in a format appropriate to its data type;
9153 you can choose a different format by specifying @samp{/@var{f}}, where
9154 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9158 @itemx print /@var{f}
9159 @cindex reprint the last value
9160 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9161 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9162 conveniently inspect the same value in an alternative format.
9165 A more low-level way of examining data is with the @code{x} command.
9166 It examines data in memory at a specified address and prints it in a
9167 specified format. @xref{Memory, ,Examining Memory}.
9169 If you are interested in information about types, or about how the
9170 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9171 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9174 @cindex exploring hierarchical data structures
9176 Another way of examining values of expressions and type information is
9177 through the Python extension command @code{explore} (available only if
9178 the @value{GDBN} build is configured with @code{--with-python}). It
9179 offers an interactive way to start at the highest level (or, the most
9180 abstract level) of the data type of an expression (or, the data type
9181 itself) and explore all the way down to leaf scalar values/fields
9182 embedded in the higher level data types.
9185 @item explore @var{arg}
9186 @var{arg} is either an expression (in the source language), or a type
9187 visible in the current context of the program being debugged.
9190 The working of the @code{explore} command can be illustrated with an
9191 example. If a data type @code{struct ComplexStruct} is defined in your
9201 struct ComplexStruct
9203 struct SimpleStruct *ss_p;
9209 followed by variable declarations as
9212 struct SimpleStruct ss = @{ 10, 1.11 @};
9213 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9217 then, the value of the variable @code{cs} can be explored using the
9218 @code{explore} command as follows.
9222 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9223 the following fields:
9225 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9226 arr = <Enter 1 to explore this field of type `int [10]'>
9228 Enter the field number of choice:
9232 Since the fields of @code{cs} are not scalar values, you are being
9233 prompted to chose the field you want to explore. Let's say you choose
9234 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9235 pointer, you will be asked if it is pointing to a single value. From
9236 the declaration of @code{cs} above, it is indeed pointing to a single
9237 value, hence you enter @code{y}. If you enter @code{n}, then you will
9238 be asked if it were pointing to an array of values, in which case this
9239 field will be explored as if it were an array.
9242 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9243 Continue exploring it as a pointer to a single value [y/n]: y
9244 The value of `*(cs.ss_p)' is a struct/class of type `struct
9245 SimpleStruct' with the following fields:
9247 i = 10 .. (Value of type `int')
9248 d = 1.1100000000000001 .. (Value of type `double')
9250 Press enter to return to parent value:
9254 If the field @code{arr} of @code{cs} was chosen for exploration by
9255 entering @code{1} earlier, then since it is as array, you will be
9256 prompted to enter the index of the element in the array that you want
9260 `cs.arr' is an array of `int'.
9261 Enter the index of the element you want to explore in `cs.arr': 5
9263 `(cs.arr)[5]' is a scalar value of type `int'.
9267 Press enter to return to parent value:
9270 In general, at any stage of exploration, you can go deeper towards the
9271 leaf values by responding to the prompts appropriately, or hit the
9272 return key to return to the enclosing data structure (the @i{higher}
9273 level data structure).
9275 Similar to exploring values, you can use the @code{explore} command to
9276 explore types. Instead of specifying a value (which is typically a
9277 variable name or an expression valid in the current context of the
9278 program being debugged), you specify a type name. If you consider the
9279 same example as above, your can explore the type
9280 @code{struct ComplexStruct} by passing the argument
9281 @code{struct ComplexStruct} to the @code{explore} command.
9284 (gdb) explore struct ComplexStruct
9288 By responding to the prompts appropriately in the subsequent interactive
9289 session, you can explore the type @code{struct ComplexStruct} in a
9290 manner similar to how the value @code{cs} was explored in the above
9293 The @code{explore} command also has two sub-commands,
9294 @code{explore value} and @code{explore type}. The former sub-command is
9295 a way to explicitly specify that value exploration of the argument is
9296 being invoked, while the latter is a way to explicitly specify that type
9297 exploration of the argument is being invoked.
9300 @item explore value @var{expr}
9301 @cindex explore value
9302 This sub-command of @code{explore} explores the value of the
9303 expression @var{expr} (if @var{expr} is an expression valid in the
9304 current context of the program being debugged). The behavior of this
9305 command is identical to that of the behavior of the @code{explore}
9306 command being passed the argument @var{expr}.
9308 @item explore type @var{arg}
9309 @cindex explore type
9310 This sub-command of @code{explore} explores the type of @var{arg} (if
9311 @var{arg} is a type visible in the current context of program being
9312 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9313 is an expression valid in the current context of the program being
9314 debugged). If @var{arg} is a type, then the behavior of this command is
9315 identical to that of the @code{explore} command being passed the
9316 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9317 this command will be identical to that of the @code{explore} command
9318 being passed the type of @var{arg} as the argument.
9322 * Expressions:: Expressions
9323 * Ambiguous Expressions:: Ambiguous Expressions
9324 * Variables:: Program variables
9325 * Arrays:: Artificial arrays
9326 * Output Formats:: Output formats
9327 * Memory:: Examining memory
9328 * Auto Display:: Automatic display
9329 * Print Settings:: Print settings
9330 * Pretty Printing:: Python pretty printing
9331 * Value History:: Value history
9332 * Convenience Vars:: Convenience variables
9333 * Convenience Funs:: Convenience functions
9334 * Registers:: Registers
9335 * Floating Point Hardware:: Floating point hardware
9336 * Vector Unit:: Vector Unit
9337 * OS Information:: Auxiliary data provided by operating system
9338 * Memory Region Attributes:: Memory region attributes
9339 * Dump/Restore Files:: Copy between memory and a file
9340 * Core File Generation:: Cause a program dump its core
9341 * Character Sets:: Debugging programs that use a different
9342 character set than GDB does
9343 * Caching Target Data:: Data caching for targets
9344 * Searching Memory:: Searching memory for a sequence of bytes
9345 * Value Sizes:: Managing memory allocated for values
9349 @section Expressions
9352 @code{print} and many other @value{GDBN} commands accept an expression and
9353 compute its value. Any kind of constant, variable or operator defined
9354 by the programming language you are using is valid in an expression in
9355 @value{GDBN}. This includes conditional expressions, function calls,
9356 casts, and string constants. It also includes preprocessor macros, if
9357 you compiled your program to include this information; see
9360 @cindex arrays in expressions
9361 @value{GDBN} supports array constants in expressions input by
9362 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9363 you can use the command @code{print @{1, 2, 3@}} to create an array
9364 of three integers. If you pass an array to a function or assign it
9365 to a program variable, @value{GDBN} copies the array to memory that
9366 is @code{malloc}ed in the target program.
9368 Because C is so widespread, most of the expressions shown in examples in
9369 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9370 Languages}, for information on how to use expressions in other
9373 In this section, we discuss operators that you can use in @value{GDBN}
9374 expressions regardless of your programming language.
9376 @cindex casts, in expressions
9377 Casts are supported in all languages, not just in C, because it is so
9378 useful to cast a number into a pointer in order to examine a structure
9379 at that address in memory.
9380 @c FIXME: casts supported---Mod2 true?
9382 @value{GDBN} supports these operators, in addition to those common
9383 to programming languages:
9387 @samp{@@} is a binary operator for treating parts of memory as arrays.
9388 @xref{Arrays, ,Artificial Arrays}, for more information.
9391 @samp{::} allows you to specify a variable in terms of the file or
9392 function where it is defined. @xref{Variables, ,Program Variables}.
9394 @cindex @{@var{type}@}
9395 @cindex type casting memory
9396 @cindex memory, viewing as typed object
9397 @cindex casts, to view memory
9398 @item @{@var{type}@} @var{addr}
9399 Refers to an object of type @var{type} stored at address @var{addr} in
9400 memory. The address @var{addr} may be any expression whose value is
9401 an integer or pointer (but parentheses are required around binary
9402 operators, just as in a cast). This construct is allowed regardless
9403 of what kind of data is normally supposed to reside at @var{addr}.
9406 @node Ambiguous Expressions
9407 @section Ambiguous Expressions
9408 @cindex ambiguous expressions
9410 Expressions can sometimes contain some ambiguous elements. For instance,
9411 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9412 a single function name to be defined several times, for application in
9413 different contexts. This is called @dfn{overloading}. Another example
9414 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9415 templates and is typically instantiated several times, resulting in
9416 the same function name being defined in different contexts.
9418 In some cases and depending on the language, it is possible to adjust
9419 the expression to remove the ambiguity. For instance in C@t{++}, you
9420 can specify the signature of the function you want to break on, as in
9421 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9422 qualified name of your function often makes the expression unambiguous
9425 When an ambiguity that needs to be resolved is detected, the debugger
9426 has the capability to display a menu of numbered choices for each
9427 possibility, and then waits for the selection with the prompt @samp{>}.
9428 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9429 aborts the current command. If the command in which the expression was
9430 used allows more than one choice to be selected, the next option in the
9431 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9434 For example, the following session excerpt shows an attempt to set a
9435 breakpoint at the overloaded symbol @code{String::after}.
9436 We choose three particular definitions of that function name:
9438 @c FIXME! This is likely to change to show arg type lists, at least
9441 (@value{GDBP}) b String::after
9444 [2] file:String.cc; line number:867
9445 [3] file:String.cc; line number:860
9446 [4] file:String.cc; line number:875
9447 [5] file:String.cc; line number:853
9448 [6] file:String.cc; line number:846
9449 [7] file:String.cc; line number:735
9451 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9452 Breakpoint 2 at 0xb344: file String.cc, line 875.
9453 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9454 Multiple breakpoints were set.
9455 Use the "delete" command to delete unwanted
9462 @kindex set multiple-symbols
9463 @item set multiple-symbols @var{mode}
9464 @cindex multiple-symbols menu
9466 This option allows you to adjust the debugger behavior when an expression
9469 By default, @var{mode} is set to @code{all}. If the command with which
9470 the expression is used allows more than one choice, then @value{GDBN}
9471 automatically selects all possible choices. For instance, inserting
9472 a breakpoint on a function using an ambiguous name results in a breakpoint
9473 inserted on each possible match. However, if a unique choice must be made,
9474 then @value{GDBN} uses the menu to help you disambiguate the expression.
9475 For instance, printing the address of an overloaded function will result
9476 in the use of the menu.
9478 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9479 when an ambiguity is detected.
9481 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9482 an error due to the ambiguity and the command is aborted.
9484 @kindex show multiple-symbols
9485 @item show multiple-symbols
9486 Show the current value of the @code{multiple-symbols} setting.
9490 @section Program Variables
9492 The most common kind of expression to use is the name of a variable
9495 Variables in expressions are understood in the selected stack frame
9496 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9500 global (or file-static)
9507 visible according to the scope rules of the
9508 programming language from the point of execution in that frame
9511 @noindent This means that in the function
9526 you can examine and use the variable @code{a} whenever your program is
9527 executing within the function @code{foo}, but you can only use or
9528 examine the variable @code{b} while your program is executing inside
9529 the block where @code{b} is declared.
9531 @cindex variable name conflict
9532 There is an exception: you can refer to a variable or function whose
9533 scope is a single source file even if the current execution point is not
9534 in this file. But it is possible to have more than one such variable or
9535 function with the same name (in different source files). If that
9536 happens, referring to that name has unpredictable effects. If you wish,
9537 you can specify a static variable in a particular function or file by
9538 using the colon-colon (@code{::}) notation:
9540 @cindex colon-colon, context for variables/functions
9542 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9543 @cindex @code{::}, context for variables/functions
9546 @var{file}::@var{variable}
9547 @var{function}::@var{variable}
9551 Here @var{file} or @var{function} is the name of the context for the
9552 static @var{variable}. In the case of file names, you can use quotes to
9553 make sure @value{GDBN} parses the file name as a single word---for example,
9554 to print a global value of @code{x} defined in @file{f2.c}:
9557 (@value{GDBP}) p 'f2.c'::x
9560 The @code{::} notation is normally used for referring to
9561 static variables, since you typically disambiguate uses of local variables
9562 in functions by selecting the appropriate frame and using the
9563 simple name of the variable. However, you may also use this notation
9564 to refer to local variables in frames enclosing the selected frame:
9573 process (a); /* Stop here */
9584 For example, if there is a breakpoint at the commented line,
9585 here is what you might see
9586 when the program stops after executing the call @code{bar(0)}:
9591 (@value{GDBP}) p bar::a
9594 #2 0x080483d0 in foo (a=5) at foobar.c:12
9597 (@value{GDBP}) p bar::a
9601 @cindex C@t{++} scope resolution
9602 These uses of @samp{::} are very rarely in conflict with the very
9603 similar use of the same notation in C@t{++}. When they are in
9604 conflict, the C@t{++} meaning takes precedence; however, this can be
9605 overridden by quoting the file or function name with single quotes.
9607 For example, suppose the program is stopped in a method of a class
9608 that has a field named @code{includefile}, and there is also an
9609 include file named @file{includefile} that defines a variable,
9613 (@value{GDBP}) p includefile
9615 (@value{GDBP}) p includefile::some_global
9616 A syntax error in expression, near `'.
9617 (@value{GDBP}) p 'includefile'::some_global
9621 @cindex wrong values
9622 @cindex variable values, wrong
9623 @cindex function entry/exit, wrong values of variables
9624 @cindex optimized code, wrong values of variables
9626 @emph{Warning:} Occasionally, a local variable may appear to have the
9627 wrong value at certain points in a function---just after entry to a new
9628 scope, and just before exit.
9630 You may see this problem when you are stepping by machine instructions.
9631 This is because, on most machines, it takes more than one instruction to
9632 set up a stack frame (including local variable definitions); if you are
9633 stepping by machine instructions, variables may appear to have the wrong
9634 values until the stack frame is completely built. On exit, it usually
9635 also takes more than one machine instruction to destroy a stack frame;
9636 after you begin stepping through that group of instructions, local
9637 variable definitions may be gone.
9639 This may also happen when the compiler does significant optimizations.
9640 To be sure of always seeing accurate values, turn off all optimization
9643 @cindex ``No symbol "foo" in current context''
9644 Another possible effect of compiler optimizations is to optimize
9645 unused variables out of existence, or assign variables to registers (as
9646 opposed to memory addresses). Depending on the support for such cases
9647 offered by the debug info format used by the compiler, @value{GDBN}
9648 might not be able to display values for such local variables. If that
9649 happens, @value{GDBN} will print a message like this:
9652 No symbol "foo" in current context.
9655 To solve such problems, either recompile without optimizations, or use a
9656 different debug info format, if the compiler supports several such
9657 formats. @xref{Compilation}, for more information on choosing compiler
9658 options. @xref{C, ,C and C@t{++}}, for more information about debug
9659 info formats that are best suited to C@t{++} programs.
9661 If you ask to print an object whose contents are unknown to
9662 @value{GDBN}, e.g., because its data type is not completely specified
9663 by the debug information, @value{GDBN} will say @samp{<incomplete
9664 type>}. @xref{Symbols, incomplete type}, for more about this.
9666 @cindex no debug info variables
9667 If you try to examine or use the value of a (global) variable for
9668 which @value{GDBN} has no type information, e.g., because the program
9669 includes no debug information, @value{GDBN} displays an error message.
9670 @xref{Symbols, unknown type}, for more about unknown types. If you
9671 cast the variable to its declared type, @value{GDBN} gets the
9672 variable's value using the cast-to type as the variable's type. For
9673 example, in a C program:
9676 (@value{GDBP}) p var
9677 'var' has unknown type; cast it to its declared type
9678 (@value{GDBP}) p (float) var
9682 If you append @kbd{@@entry} string to a function parameter name you get its
9683 value at the time the function got called. If the value is not available an
9684 error message is printed. Entry values are available only with some compilers.
9685 Entry values are normally also printed at the function parameter list according
9686 to @ref{set print entry-values}.
9689 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9695 (gdb) print i@@entry
9699 Strings are identified as arrays of @code{char} values without specified
9700 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9701 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9702 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9703 defines literal string type @code{"char"} as @code{char} without a sign.
9708 signed char var1[] = "A";
9711 You get during debugging
9716 $2 = @{65 'A', 0 '\0'@}
9720 @section Artificial Arrays
9722 @cindex artificial array
9724 @kindex @@@r{, referencing memory as an array}
9725 It is often useful to print out several successive objects of the
9726 same type in memory; a section of an array, or an array of
9727 dynamically determined size for which only a pointer exists in the
9730 You can do this by referring to a contiguous span of memory as an
9731 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9732 operand of @samp{@@} should be the first element of the desired array
9733 and be an individual object. The right operand should be the desired length
9734 of the array. The result is an array value whose elements are all of
9735 the type of the left argument. The first element is actually the left
9736 argument; the second element comes from bytes of memory immediately
9737 following those that hold the first element, and so on. Here is an
9738 example. If a program says
9741 int *array = (int *) malloc (len * sizeof (int));
9745 you can print the contents of @code{array} with
9751 The left operand of @samp{@@} must reside in memory. Array values made
9752 with @samp{@@} in this way behave just like other arrays in terms of
9753 subscripting, and are coerced to pointers when used in expressions.
9754 Artificial arrays most often appear in expressions via the value history
9755 (@pxref{Value History, ,Value History}), after printing one out.
9757 Another way to create an artificial array is to use a cast.
9758 This re-interprets a value as if it were an array.
9759 The value need not be in memory:
9761 (@value{GDBP}) p/x (short[2])0x12345678
9762 $1 = @{0x1234, 0x5678@}
9765 As a convenience, if you leave the array length out (as in
9766 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9767 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9769 (@value{GDBP}) p/x (short[])0x12345678
9770 $2 = @{0x1234, 0x5678@}
9773 Sometimes the artificial array mechanism is not quite enough; in
9774 moderately complex data structures, the elements of interest may not
9775 actually be adjacent---for example, if you are interested in the values
9776 of pointers in an array. One useful work-around in this situation is
9777 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9778 Variables}) as a counter in an expression that prints the first
9779 interesting value, and then repeat that expression via @key{RET}. For
9780 instance, suppose you have an array @code{dtab} of pointers to
9781 structures, and you are interested in the values of a field @code{fv}
9782 in each structure. Here is an example of what you might type:
9792 @node Output Formats
9793 @section Output Formats
9795 @cindex formatted output
9796 @cindex output formats
9797 By default, @value{GDBN} prints a value according to its data type. Sometimes
9798 this is not what you want. For example, you might want to print a number
9799 in hex, or a pointer in decimal. Or you might want to view data in memory
9800 at a certain address as a character string or as an instruction. To do
9801 these things, specify an @dfn{output format} when you print a value.
9803 The simplest use of output formats is to say how to print a value
9804 already computed. This is done by starting the arguments of the
9805 @code{print} command with a slash and a format letter. The format
9806 letters supported are:
9810 Regard the bits of the value as an integer, and print the integer in
9814 Print as integer in signed decimal.
9817 Print as integer in unsigned decimal.
9820 Print as integer in octal.
9823 Print as integer in binary. The letter @samp{t} stands for ``two''.
9824 @footnote{@samp{b} cannot be used because these format letters are also
9825 used with the @code{x} command, where @samp{b} stands for ``byte'';
9826 see @ref{Memory,,Examining Memory}.}
9829 @cindex unknown address, locating
9830 @cindex locate address
9831 Print as an address, both absolute in hexadecimal and as an offset from
9832 the nearest preceding symbol. You can use this format used to discover
9833 where (in what function) an unknown address is located:
9836 (@value{GDBP}) p/a 0x54320
9837 $3 = 0x54320 <_initialize_vx+396>
9841 The command @code{info symbol 0x54320} yields similar results.
9842 @xref{Symbols, info symbol}.
9845 Regard as an integer and print it as a character constant. This
9846 prints both the numerical value and its character representation. The
9847 character representation is replaced with the octal escape @samp{\nnn}
9848 for characters outside the 7-bit @sc{ascii} range.
9850 Without this format, @value{GDBN} displays @code{char},
9851 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9852 constants. Single-byte members of vectors are displayed as integer
9856 Regard the bits of the value as a floating point number and print
9857 using typical floating point syntax.
9860 @cindex printing strings
9861 @cindex printing byte arrays
9862 Regard as a string, if possible. With this format, pointers to single-byte
9863 data are displayed as null-terminated strings and arrays of single-byte data
9864 are displayed as fixed-length strings. Other values are displayed in their
9867 Without this format, @value{GDBN} displays pointers to and arrays of
9868 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9869 strings. Single-byte members of a vector are displayed as an integer
9873 Like @samp{x} formatting, the value is treated as an integer and
9874 printed as hexadecimal, but leading zeros are printed to pad the value
9875 to the size of the integer type.
9878 @cindex raw printing
9879 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9880 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9881 Printing}). This typically results in a higher-level display of the
9882 value's contents. The @samp{r} format bypasses any Python
9883 pretty-printer which might exist.
9886 For example, to print the program counter in hex (@pxref{Registers}), type
9893 Note that no space is required before the slash; this is because command
9894 names in @value{GDBN} cannot contain a slash.
9896 To reprint the last value in the value history with a different format,
9897 you can use the @code{print} command with just a format and no
9898 expression. For example, @samp{p/x} reprints the last value in hex.
9901 @section Examining Memory
9903 You can use the command @code{x} (for ``examine'') to examine memory in
9904 any of several formats, independently of your program's data types.
9906 @cindex examining memory
9908 @kindex x @r{(examine memory)}
9909 @item x/@var{nfu} @var{addr}
9912 Use the @code{x} command to examine memory.
9915 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9916 much memory to display and how to format it; @var{addr} is an
9917 expression giving the address where you want to start displaying memory.
9918 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9919 Several commands set convenient defaults for @var{addr}.
9922 @item @var{n}, the repeat count
9923 The repeat count is a decimal integer; the default is 1. It specifies
9924 how much memory (counting by units @var{u}) to display. If a negative
9925 number is specified, memory is examined backward from @var{addr}.
9926 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9929 @item @var{f}, the display format
9930 The display format is one of the formats used by @code{print}
9931 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9932 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9933 The default is @samp{x} (hexadecimal) initially. The default changes
9934 each time you use either @code{x} or @code{print}.
9936 @item @var{u}, the unit size
9937 The unit size is any of
9943 Halfwords (two bytes).
9945 Words (four bytes). This is the initial default.
9947 Giant words (eight bytes).
9950 Each time you specify a unit size with @code{x}, that size becomes the
9951 default unit the next time you use @code{x}. For the @samp{i} format,
9952 the unit size is ignored and is normally not written. For the @samp{s} format,
9953 the unit size defaults to @samp{b}, unless it is explicitly given.
9954 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9955 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9956 Note that the results depend on the programming language of the
9957 current compilation unit. If the language is C, the @samp{s}
9958 modifier will use the UTF-16 encoding while @samp{w} will use
9959 UTF-32. The encoding is set by the programming language and cannot
9962 @item @var{addr}, starting display address
9963 @var{addr} is the address where you want @value{GDBN} to begin displaying
9964 memory. The expression need not have a pointer value (though it may);
9965 it is always interpreted as an integer address of a byte of memory.
9966 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9967 @var{addr} is usually just after the last address examined---but several
9968 other commands also set the default address: @code{info breakpoints} (to
9969 the address of the last breakpoint listed), @code{info line} (to the
9970 starting address of a line), and @code{print} (if you use it to display
9971 a value from memory).
9974 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9975 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9976 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9977 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9978 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9980 You can also specify a negative repeat count to examine memory backward
9981 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9982 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9984 Since the letters indicating unit sizes are all distinct from the
9985 letters specifying output formats, you do not have to remember whether
9986 unit size or format comes first; either order works. The output
9987 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9988 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9990 Even though the unit size @var{u} is ignored for the formats @samp{s}
9991 and @samp{i}, you might still want to use a count @var{n}; for example,
9992 @samp{3i} specifies that you want to see three machine instructions,
9993 including any operands. For convenience, especially when used with
9994 the @code{display} command, the @samp{i} format also prints branch delay
9995 slot instructions, if any, beyond the count specified, which immediately
9996 follow the last instruction that is within the count. The command
9997 @code{disassemble} gives an alternative way of inspecting machine
9998 instructions; see @ref{Machine Code,,Source and Machine Code}.
10000 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10001 the command displays null-terminated strings or instructions before the given
10002 address as many as the absolute value of the given number. For the @samp{i}
10003 format, we use line number information in the debug info to accurately locate
10004 instruction boundaries while disassembling backward. If line info is not
10005 available, the command stops examining memory with an error message.
10007 All the defaults for the arguments to @code{x} are designed to make it
10008 easy to continue scanning memory with minimal specifications each time
10009 you use @code{x}. For example, after you have inspected three machine
10010 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10011 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10012 the repeat count @var{n} is used again; the other arguments default as
10013 for successive uses of @code{x}.
10015 When examining machine instructions, the instruction at current program
10016 counter is shown with a @code{=>} marker. For example:
10019 (@value{GDBP}) x/5i $pc-6
10020 0x804837f <main+11>: mov %esp,%ebp
10021 0x8048381 <main+13>: push %ecx
10022 0x8048382 <main+14>: sub $0x4,%esp
10023 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10024 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10027 @cindex @code{$_}, @code{$__}, and value history
10028 The addresses and contents printed by the @code{x} command are not saved
10029 in the value history because there is often too much of them and they
10030 would get in the way. Instead, @value{GDBN} makes these values available for
10031 subsequent use in expressions as values of the convenience variables
10032 @code{$_} and @code{$__}. After an @code{x} command, the last address
10033 examined is available for use in expressions in the convenience variable
10034 @code{$_}. The contents of that address, as examined, are available in
10035 the convenience variable @code{$__}.
10037 If the @code{x} command has a repeat count, the address and contents saved
10038 are from the last memory unit printed; this is not the same as the last
10039 address printed if several units were printed on the last line of output.
10041 @anchor{addressable memory unit}
10042 @cindex addressable memory unit
10043 Most targets have an addressable memory unit size of 8 bits. This means
10044 that to each memory address are associated 8 bits of data. Some
10045 targets, however, have other addressable memory unit sizes.
10046 Within @value{GDBN} and this document, the term
10047 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10048 when explicitly referring to a chunk of data of that size. The word
10049 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10050 the addressable memory unit size of the target. For most systems,
10051 addressable memory unit is a synonym of byte.
10053 @cindex remote memory comparison
10054 @cindex target memory comparison
10055 @cindex verify remote memory image
10056 @cindex verify target memory image
10057 When you are debugging a program running on a remote target machine
10058 (@pxref{Remote Debugging}), you may wish to verify the program's image
10059 in the remote machine's memory against the executable file you
10060 downloaded to the target. Or, on any target, you may want to check
10061 whether the program has corrupted its own read-only sections. The
10062 @code{compare-sections} command is provided for such situations.
10065 @kindex compare-sections
10066 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10067 Compare the data of a loadable section @var{section-name} in the
10068 executable file of the program being debugged with the same section in
10069 the target machine's memory, and report any mismatches. With no
10070 arguments, compares all loadable sections. With an argument of
10071 @code{-r}, compares all loadable read-only sections.
10073 Note: for remote targets, this command can be accelerated if the
10074 target supports computing the CRC checksum of a block of memory
10075 (@pxref{qCRC packet}).
10079 @section Automatic Display
10080 @cindex automatic display
10081 @cindex display of expressions
10083 If you find that you want to print the value of an expression frequently
10084 (to see how it changes), you might want to add it to the @dfn{automatic
10085 display list} so that @value{GDBN} prints its value each time your program stops.
10086 Each expression added to the list is given a number to identify it;
10087 to remove an expression from the list, you specify that number.
10088 The automatic display looks like this:
10092 3: bar[5] = (struct hack *) 0x3804
10096 This display shows item numbers, expressions and their current values. As with
10097 displays you request manually using @code{x} or @code{print}, you can
10098 specify the output format you prefer; in fact, @code{display} decides
10099 whether to use @code{print} or @code{x} depending your format
10100 specification---it uses @code{x} if you specify either the @samp{i}
10101 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10105 @item display @var{expr}
10106 Add the expression @var{expr} to the list of expressions to display
10107 each time your program stops. @xref{Expressions, ,Expressions}.
10109 @code{display} does not repeat if you press @key{RET} again after using it.
10111 @item display/@var{fmt} @var{expr}
10112 For @var{fmt} specifying only a display format and not a size or
10113 count, add the expression @var{expr} to the auto-display list but
10114 arrange to display it each time in the specified format @var{fmt}.
10115 @xref{Output Formats,,Output Formats}.
10117 @item display/@var{fmt} @var{addr}
10118 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10119 number of units, add the expression @var{addr} as a memory address to
10120 be examined each time your program stops. Examining means in effect
10121 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10124 For example, @samp{display/i $pc} can be helpful, to see the machine
10125 instruction about to be executed each time execution stops (@samp{$pc}
10126 is a common name for the program counter; @pxref{Registers, ,Registers}).
10129 @kindex delete display
10131 @item undisplay @var{dnums}@dots{}
10132 @itemx delete display @var{dnums}@dots{}
10133 Remove items from the list of expressions to display. Specify the
10134 numbers of the displays that you want affected with the command
10135 argument @var{dnums}. It can be a single display number, one of the
10136 numbers shown in the first field of the @samp{info display} display;
10137 or it could be a range of display numbers, as in @code{2-4}.
10139 @code{undisplay} does not repeat if you press @key{RET} after using it.
10140 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10142 @kindex disable display
10143 @item disable display @var{dnums}@dots{}
10144 Disable the display of item numbers @var{dnums}. A disabled display
10145 item is not printed automatically, but is not forgotten. It may be
10146 enabled again later. Specify the numbers of the displays that you
10147 want affected with the command argument @var{dnums}. It can be a
10148 single display number, one of the numbers shown in the first field of
10149 the @samp{info display} display; or it could be a range of display
10150 numbers, as in @code{2-4}.
10152 @kindex enable display
10153 @item enable display @var{dnums}@dots{}
10154 Enable display of item numbers @var{dnums}. It becomes effective once
10155 again in auto display of its expression, until you specify otherwise.
10156 Specify the numbers of the displays that you want affected with the
10157 command argument @var{dnums}. It can be a single display number, one
10158 of the numbers shown in the first field of the @samp{info display}
10159 display; or it could be a range of display numbers, as in @code{2-4}.
10162 Display the current values of the expressions on the list, just as is
10163 done when your program stops.
10165 @kindex info display
10167 Print the list of expressions previously set up to display
10168 automatically, each one with its item number, but without showing the
10169 values. This includes disabled expressions, which are marked as such.
10170 It also includes expressions which would not be displayed right now
10171 because they refer to automatic variables not currently available.
10174 @cindex display disabled out of scope
10175 If a display expression refers to local variables, then it does not make
10176 sense outside the lexical context for which it was set up. Such an
10177 expression is disabled when execution enters a context where one of its
10178 variables is not defined. For example, if you give the command
10179 @code{display last_char} while inside a function with an argument
10180 @code{last_char}, @value{GDBN} displays this argument while your program
10181 continues to stop inside that function. When it stops elsewhere---where
10182 there is no variable @code{last_char}---the display is disabled
10183 automatically. The next time your program stops where @code{last_char}
10184 is meaningful, you can enable the display expression once again.
10186 @node Print Settings
10187 @section Print Settings
10189 @cindex format options
10190 @cindex print settings
10191 @value{GDBN} provides the following ways to control how arrays, structures,
10192 and symbols are printed.
10195 These settings are useful for debugging programs in any language:
10199 @item set print address
10200 @itemx set print address on
10201 @cindex print/don't print memory addresses
10202 @value{GDBN} prints memory addresses showing the location of stack
10203 traces, structure values, pointer values, breakpoints, and so forth,
10204 even when it also displays the contents of those addresses. The default
10205 is @code{on}. For example, this is what a stack frame display looks like with
10206 @code{set print address on}:
10211 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10213 530 if (lquote != def_lquote)
10217 @item set print address off
10218 Do not print addresses when displaying their contents. For example,
10219 this is the same stack frame displayed with @code{set print address off}:
10223 (@value{GDBP}) set print addr off
10225 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10226 530 if (lquote != def_lquote)
10230 You can use @samp{set print address off} to eliminate all machine
10231 dependent displays from the @value{GDBN} interface. For example, with
10232 @code{print address off}, you should get the same text for backtraces on
10233 all machines---whether or not they involve pointer arguments.
10236 @item show print address
10237 Show whether or not addresses are to be printed.
10240 When @value{GDBN} prints a symbolic address, it normally prints the
10241 closest earlier symbol plus an offset. If that symbol does not uniquely
10242 identify the address (for example, it is a name whose scope is a single
10243 source file), you may need to clarify. One way to do this is with
10244 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10245 you can set @value{GDBN} to print the source file and line number when
10246 it prints a symbolic address:
10249 @item set print symbol-filename on
10250 @cindex source file and line of a symbol
10251 @cindex symbol, source file and line
10252 Tell @value{GDBN} to print the source file name and line number of a
10253 symbol in the symbolic form of an address.
10255 @item set print symbol-filename off
10256 Do not print source file name and line number of a symbol. This is the
10259 @item show print symbol-filename
10260 Show whether or not @value{GDBN} will print the source file name and
10261 line number of a symbol in the symbolic form of an address.
10264 Another situation where it is helpful to show symbol filenames and line
10265 numbers is when disassembling code; @value{GDBN} shows you the line
10266 number and source file that corresponds to each instruction.
10268 Also, you may wish to see the symbolic form only if the address being
10269 printed is reasonably close to the closest earlier symbol:
10272 @item set print max-symbolic-offset @var{max-offset}
10273 @itemx set print max-symbolic-offset unlimited
10274 @cindex maximum value for offset of closest symbol
10275 Tell @value{GDBN} to only display the symbolic form of an address if the
10276 offset between the closest earlier symbol and the address is less than
10277 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10278 to always print the symbolic form of an address if any symbol precedes
10279 it. Zero is equivalent to @code{unlimited}.
10281 @item show print max-symbolic-offset
10282 Ask how large the maximum offset is that @value{GDBN} prints in a
10286 @cindex wild pointer, interpreting
10287 @cindex pointer, finding referent
10288 If you have a pointer and you are not sure where it points, try
10289 @samp{set print symbol-filename on}. Then you can determine the name
10290 and source file location of the variable where it points, using
10291 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10292 For example, here @value{GDBN} shows that a variable @code{ptt} points
10293 at another variable @code{t}, defined in @file{hi2.c}:
10296 (@value{GDBP}) set print symbol-filename on
10297 (@value{GDBP}) p/a ptt
10298 $4 = 0xe008 <t in hi2.c>
10302 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10303 does not show the symbol name and filename of the referent, even with
10304 the appropriate @code{set print} options turned on.
10307 You can also enable @samp{/a}-like formatting all the time using
10308 @samp{set print symbol on}:
10311 @item set print symbol on
10312 Tell @value{GDBN} to print the symbol corresponding to an address, if
10315 @item set print symbol off
10316 Tell @value{GDBN} not to print the symbol corresponding to an
10317 address. In this mode, @value{GDBN} will still print the symbol
10318 corresponding to pointers to functions. This is the default.
10320 @item show print symbol
10321 Show whether @value{GDBN} will display the symbol corresponding to an
10325 Other settings control how different kinds of objects are printed:
10328 @item set print array
10329 @itemx set print array on
10330 @cindex pretty print arrays
10331 Pretty print arrays. This format is more convenient to read,
10332 but uses more space. The default is off.
10334 @item set print array off
10335 Return to compressed format for arrays.
10337 @item show print array
10338 Show whether compressed or pretty format is selected for displaying
10341 @cindex print array indexes
10342 @item set print array-indexes
10343 @itemx set print array-indexes on
10344 Print the index of each element when displaying arrays. May be more
10345 convenient to locate a given element in the array or quickly find the
10346 index of a given element in that printed array. The default is off.
10348 @item set print array-indexes off
10349 Stop printing element indexes when displaying arrays.
10351 @item show print array-indexes
10352 Show whether the index of each element is printed when displaying
10355 @item set print elements @var{number-of-elements}
10356 @itemx set print elements unlimited
10357 @cindex number of array elements to print
10358 @cindex limit on number of printed array elements
10359 Set a limit on how many elements of an array @value{GDBN} will print.
10360 If @value{GDBN} is printing a large array, it stops printing after it has
10361 printed the number of elements set by the @code{set print elements} command.
10362 This limit also applies to the display of strings.
10363 When @value{GDBN} starts, this limit is set to 200.
10364 Setting @var{number-of-elements} to @code{unlimited} or zero means
10365 that the number of elements to print is unlimited.
10367 @item show print elements
10368 Display the number of elements of a large array that @value{GDBN} will print.
10369 If the number is 0, then the printing is unlimited.
10371 @item set print frame-arguments @var{value}
10372 @kindex set print frame-arguments
10373 @cindex printing frame argument values
10374 @cindex print all frame argument values
10375 @cindex print frame argument values for scalars only
10376 @cindex do not print frame argument values
10377 This command allows to control how the values of arguments are printed
10378 when the debugger prints a frame (@pxref{Frames}). The possible
10383 The values of all arguments are printed.
10386 Print the value of an argument only if it is a scalar. The value of more
10387 complex arguments such as arrays, structures, unions, etc, is replaced
10388 by @code{@dots{}}. This is the default. Here is an example where
10389 only scalar arguments are shown:
10392 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10397 None of the argument values are printed. Instead, the value of each argument
10398 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10401 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10406 By default, only scalar arguments are printed. This command can be used
10407 to configure the debugger to print the value of all arguments, regardless
10408 of their type. However, it is often advantageous to not print the value
10409 of more complex parameters. For instance, it reduces the amount of
10410 information printed in each frame, making the backtrace more readable.
10411 Also, it improves performance when displaying Ada frames, because
10412 the computation of large arguments can sometimes be CPU-intensive,
10413 especially in large applications. Setting @code{print frame-arguments}
10414 to @code{scalars} (the default) or @code{none} avoids this computation,
10415 thus speeding up the display of each Ada frame.
10417 @item show print frame-arguments
10418 Show how the value of arguments should be displayed when printing a frame.
10420 @item set print raw frame-arguments on
10421 Print frame arguments in raw, non pretty-printed, form.
10423 @item set print raw frame-arguments off
10424 Print frame arguments in pretty-printed form, if there is a pretty-printer
10425 for the value (@pxref{Pretty Printing}),
10426 otherwise print the value in raw form.
10427 This is the default.
10429 @item show print raw frame-arguments
10430 Show whether to print frame arguments in raw form.
10432 @anchor{set print entry-values}
10433 @item set print entry-values @var{value}
10434 @kindex set print entry-values
10435 Set printing of frame argument values at function entry. In some cases
10436 @value{GDBN} can determine the value of function argument which was passed by
10437 the function caller, even if the value was modified inside the called function
10438 and therefore is different. With optimized code, the current value could be
10439 unavailable, but the entry value may still be known.
10441 The default value is @code{default} (see below for its description). Older
10442 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10443 this feature will behave in the @code{default} setting the same way as with the
10446 This functionality is currently supported only by DWARF 2 debugging format and
10447 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10448 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10451 The @var{value} parameter can be one of the following:
10455 Print only actual parameter values, never print values from function entry
10459 #0 different (val=6)
10460 #0 lost (val=<optimized out>)
10462 #0 invalid (val=<optimized out>)
10466 Print only parameter values from function entry point. The actual parameter
10467 values are never printed.
10469 #0 equal (val@@entry=5)
10470 #0 different (val@@entry=5)
10471 #0 lost (val@@entry=5)
10472 #0 born (val@@entry=<optimized out>)
10473 #0 invalid (val@@entry=<optimized out>)
10477 Print only parameter values from function entry point. If value from function
10478 entry point is not known while the actual value is known, print the actual
10479 value for such parameter.
10481 #0 equal (val@@entry=5)
10482 #0 different (val@@entry=5)
10483 #0 lost (val@@entry=5)
10485 #0 invalid (val@@entry=<optimized out>)
10489 Print actual parameter values. If actual parameter value is not known while
10490 value from function entry point is known, print the entry point value for such
10494 #0 different (val=6)
10495 #0 lost (val@@entry=5)
10497 #0 invalid (val=<optimized out>)
10501 Always print both the actual parameter value and its value from function entry
10502 point, even if values of one or both are not available due to compiler
10505 #0 equal (val=5, val@@entry=5)
10506 #0 different (val=6, val@@entry=5)
10507 #0 lost (val=<optimized out>, val@@entry=5)
10508 #0 born (val=10, val@@entry=<optimized out>)
10509 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10513 Print the actual parameter value if it is known and also its value from
10514 function entry point if it is known. If neither is known, print for the actual
10515 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10516 values are known and identical, print the shortened
10517 @code{param=param@@entry=VALUE} notation.
10519 #0 equal (val=val@@entry=5)
10520 #0 different (val=6, val@@entry=5)
10521 #0 lost (val@@entry=5)
10523 #0 invalid (val=<optimized out>)
10527 Always print the actual parameter value. Print also its value from function
10528 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10529 if both values are known and identical, print the shortened
10530 @code{param=param@@entry=VALUE} notation.
10532 #0 equal (val=val@@entry=5)
10533 #0 different (val=6, val@@entry=5)
10534 #0 lost (val=<optimized out>, val@@entry=5)
10536 #0 invalid (val=<optimized out>)
10540 For analysis messages on possible failures of frame argument values at function
10541 entry resolution see @ref{set debug entry-values}.
10543 @item show print entry-values
10544 Show the method being used for printing of frame argument values at function
10547 @item set print repeats @var{number-of-repeats}
10548 @itemx set print repeats unlimited
10549 @cindex repeated array elements
10550 Set the threshold for suppressing display of repeated array
10551 elements. When the number of consecutive identical elements of an
10552 array exceeds the threshold, @value{GDBN} prints the string
10553 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10554 identical repetitions, instead of displaying the identical elements
10555 themselves. Setting the threshold to @code{unlimited} or zero will
10556 cause all elements to be individually printed. The default threshold
10559 @item show print repeats
10560 Display the current threshold for printing repeated identical
10563 @item set print null-stop
10564 @cindex @sc{null} elements in arrays
10565 Cause @value{GDBN} to stop printing the characters of an array when the first
10566 @sc{null} is encountered. This is useful when large arrays actually
10567 contain only short strings.
10568 The default is off.
10570 @item show print null-stop
10571 Show whether @value{GDBN} stops printing an array on the first
10572 @sc{null} character.
10574 @item set print pretty on
10575 @cindex print structures in indented form
10576 @cindex indentation in structure display
10577 Cause @value{GDBN} to print structures in an indented format with one member
10578 per line, like this:
10593 @item set print pretty off
10594 Cause @value{GDBN} to print structures in a compact format, like this:
10598 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10599 meat = 0x54 "Pork"@}
10604 This is the default format.
10606 @item show print pretty
10607 Show which format @value{GDBN} is using to print structures.
10609 @item set print sevenbit-strings on
10610 @cindex eight-bit characters in strings
10611 @cindex octal escapes in strings
10612 Print using only seven-bit characters; if this option is set,
10613 @value{GDBN} displays any eight-bit characters (in strings or
10614 character values) using the notation @code{\}@var{nnn}. This setting is
10615 best if you are working in English (@sc{ascii}) and you use the
10616 high-order bit of characters as a marker or ``meta'' bit.
10618 @item set print sevenbit-strings off
10619 Print full eight-bit characters. This allows the use of more
10620 international character sets, and is the default.
10622 @item show print sevenbit-strings
10623 Show whether or not @value{GDBN} is printing only seven-bit characters.
10625 @item set print union on
10626 @cindex unions in structures, printing
10627 Tell @value{GDBN} to print unions which are contained in structures
10628 and other unions. This is the default setting.
10630 @item set print union off
10631 Tell @value{GDBN} not to print unions which are contained in
10632 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10635 @item show print union
10636 Ask @value{GDBN} whether or not it will print unions which are contained in
10637 structures and other unions.
10639 For example, given the declarations
10642 typedef enum @{Tree, Bug@} Species;
10643 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10644 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10655 struct thing foo = @{Tree, @{Acorn@}@};
10659 with @code{set print union on} in effect @samp{p foo} would print
10662 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10666 and with @code{set print union off} in effect it would print
10669 $1 = @{it = Tree, form = @{...@}@}
10673 @code{set print union} affects programs written in C-like languages
10679 These settings are of interest when debugging C@t{++} programs:
10682 @cindex demangling C@t{++} names
10683 @item set print demangle
10684 @itemx set print demangle on
10685 Print C@t{++} names in their source form rather than in the encoded
10686 (``mangled'') form passed to the assembler and linker for type-safe
10687 linkage. The default is on.
10689 @item show print demangle
10690 Show whether C@t{++} names are printed in mangled or demangled form.
10692 @item set print asm-demangle
10693 @itemx set print asm-demangle on
10694 Print C@t{++} names in their source form rather than their mangled form, even
10695 in assembler code printouts such as instruction disassemblies.
10696 The default is off.
10698 @item show print asm-demangle
10699 Show whether C@t{++} names in assembly listings are printed in mangled
10702 @cindex C@t{++} symbol decoding style
10703 @cindex symbol decoding style, C@t{++}
10704 @kindex set demangle-style
10705 @item set demangle-style @var{style}
10706 Choose among several encoding schemes used by different compilers to represent
10707 C@t{++} names. If you omit @var{style}, you will see a list of possible
10708 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
10709 decoding style by inspecting your program.
10711 @item show demangle-style
10712 Display the encoding style currently in use for decoding C@t{++} symbols.
10714 @item set print object
10715 @itemx set print object on
10716 @cindex derived type of an object, printing
10717 @cindex display derived types
10718 When displaying a pointer to an object, identify the @emph{actual}
10719 (derived) type of the object rather than the @emph{declared} type, using
10720 the virtual function table. Note that the virtual function table is
10721 required---this feature can only work for objects that have run-time
10722 type identification; a single virtual method in the object's declared
10723 type is sufficient. Note that this setting is also taken into account when
10724 working with variable objects via MI (@pxref{GDB/MI}).
10726 @item set print object off
10727 Display only the declared type of objects, without reference to the
10728 virtual function table. This is the default setting.
10730 @item show print object
10731 Show whether actual, or declared, object types are displayed.
10733 @item set print static-members
10734 @itemx set print static-members on
10735 @cindex static members of C@t{++} objects
10736 Print static members when displaying a C@t{++} object. The default is on.
10738 @item set print static-members off
10739 Do not print static members when displaying a C@t{++} object.
10741 @item show print static-members
10742 Show whether C@t{++} static members are printed or not.
10744 @item set print pascal_static-members
10745 @itemx set print pascal_static-members on
10746 @cindex static members of Pascal objects
10747 @cindex Pascal objects, static members display
10748 Print static members when displaying a Pascal object. The default is on.
10750 @item set print pascal_static-members off
10751 Do not print static members when displaying a Pascal object.
10753 @item show print pascal_static-members
10754 Show whether Pascal static members are printed or not.
10756 @c These don't work with HP ANSI C++ yet.
10757 @item set print vtbl
10758 @itemx set print vtbl on
10759 @cindex pretty print C@t{++} virtual function tables
10760 @cindex virtual functions (C@t{++}) display
10761 @cindex VTBL display
10762 Pretty print C@t{++} virtual function tables. The default is off.
10763 (The @code{vtbl} commands do not work on programs compiled with the HP
10764 ANSI C@t{++} compiler (@code{aCC}).)
10766 @item set print vtbl off
10767 Do not pretty print C@t{++} virtual function tables.
10769 @item show print vtbl
10770 Show whether C@t{++} virtual function tables are pretty printed, or not.
10773 @node Pretty Printing
10774 @section Pretty Printing
10776 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10777 Python code. It greatly simplifies the display of complex objects. This
10778 mechanism works for both MI and the CLI.
10781 * Pretty-Printer Introduction:: Introduction to pretty-printers
10782 * Pretty-Printer Example:: An example pretty-printer
10783 * Pretty-Printer Commands:: Pretty-printer commands
10786 @node Pretty-Printer Introduction
10787 @subsection Pretty-Printer Introduction
10789 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10790 registered for the value. If there is then @value{GDBN} invokes the
10791 pretty-printer to print the value. Otherwise the value is printed normally.
10793 Pretty-printers are normally named. This makes them easy to manage.
10794 The @samp{info pretty-printer} command will list all the installed
10795 pretty-printers with their names.
10796 If a pretty-printer can handle multiple data types, then its
10797 @dfn{subprinters} are the printers for the individual data types.
10798 Each such subprinter has its own name.
10799 The format of the name is @var{printer-name};@var{subprinter-name}.
10801 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10802 Typically they are automatically loaded and registered when the corresponding
10803 debug information is loaded, thus making them available without having to
10804 do anything special.
10806 There are three places where a pretty-printer can be registered.
10810 Pretty-printers registered globally are available when debugging
10814 Pretty-printers registered with a program space are available only
10815 when debugging that program.
10816 @xref{Progspaces In Python}, for more details on program spaces in Python.
10819 Pretty-printers registered with an objfile are loaded and unloaded
10820 with the corresponding objfile (e.g., shared library).
10821 @xref{Objfiles In Python}, for more details on objfiles in Python.
10824 @xref{Selecting Pretty-Printers}, for further information on how
10825 pretty-printers are selected,
10827 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10830 @node Pretty-Printer Example
10831 @subsection Pretty-Printer Example
10833 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10836 (@value{GDBP}) print s
10838 static npos = 4294967295,
10840 <std::allocator<char>> = @{
10841 <__gnu_cxx::new_allocator<char>> = @{
10842 <No data fields>@}, <No data fields>
10844 members of std::basic_string<char, std::char_traits<char>,
10845 std::allocator<char> >::_Alloc_hider:
10846 _M_p = 0x804a014 "abcd"
10851 With a pretty-printer for @code{std::string} only the contents are printed:
10854 (@value{GDBP}) print s
10858 @node Pretty-Printer Commands
10859 @subsection Pretty-Printer Commands
10860 @cindex pretty-printer commands
10863 @kindex info pretty-printer
10864 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10865 Print the list of installed pretty-printers.
10866 This includes disabled pretty-printers, which are marked as such.
10868 @var{object-regexp} is a regular expression matching the objects
10869 whose pretty-printers to list.
10870 Objects can be @code{global}, the program space's file
10871 (@pxref{Progspaces In Python}),
10872 and the object files within that program space (@pxref{Objfiles In Python}).
10873 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10874 looks up a printer from these three objects.
10876 @var{name-regexp} is a regular expression matching the name of the printers
10879 @kindex disable pretty-printer
10880 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10881 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10882 A disabled pretty-printer is not forgotten, it may be enabled again later.
10884 @kindex enable pretty-printer
10885 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10886 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10891 Suppose we have three pretty-printers installed: one from library1.so
10892 named @code{foo} that prints objects of type @code{foo}, and
10893 another from library2.so named @code{bar} that prints two types of objects,
10894 @code{bar1} and @code{bar2}.
10897 (gdb) info pretty-printer
10904 (gdb) info pretty-printer library2
10909 (gdb) disable pretty-printer library1
10911 2 of 3 printers enabled
10912 (gdb) info pretty-printer
10919 (gdb) disable pretty-printer library2 bar;bar1
10921 1 of 3 printers enabled
10922 (gdb) info pretty-printer library2
10929 (gdb) disable pretty-printer library2 bar
10931 0 of 3 printers enabled
10932 (gdb) info pretty-printer library2
10941 Note that for @code{bar} the entire printer can be disabled,
10942 as can each individual subprinter.
10944 @node Value History
10945 @section Value History
10947 @cindex value history
10948 @cindex history of values printed by @value{GDBN}
10949 Values printed by the @code{print} command are saved in the @value{GDBN}
10950 @dfn{value history}. This allows you to refer to them in other expressions.
10951 Values are kept until the symbol table is re-read or discarded
10952 (for example with the @code{file} or @code{symbol-file} commands).
10953 When the symbol table changes, the value history is discarded,
10954 since the values may contain pointers back to the types defined in the
10959 @cindex history number
10960 The values printed are given @dfn{history numbers} by which you can
10961 refer to them. These are successive integers starting with one.
10962 @code{print} shows you the history number assigned to a value by
10963 printing @samp{$@var{num} = } before the value; here @var{num} is the
10966 To refer to any previous value, use @samp{$} followed by the value's
10967 history number. The way @code{print} labels its output is designed to
10968 remind you of this. Just @code{$} refers to the most recent value in
10969 the history, and @code{$$} refers to the value before that.
10970 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10971 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10972 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10974 For example, suppose you have just printed a pointer to a structure and
10975 want to see the contents of the structure. It suffices to type
10981 If you have a chain of structures where the component @code{next} points
10982 to the next one, you can print the contents of the next one with this:
10989 You can print successive links in the chain by repeating this
10990 command---which you can do by just typing @key{RET}.
10992 Note that the history records values, not expressions. If the value of
10993 @code{x} is 4 and you type these commands:
11001 then the value recorded in the value history by the @code{print} command
11002 remains 4 even though the value of @code{x} has changed.
11005 @kindex show values
11007 Print the last ten values in the value history, with their item numbers.
11008 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11009 values} does not change the history.
11011 @item show values @var{n}
11012 Print ten history values centered on history item number @var{n}.
11014 @item show values +
11015 Print ten history values just after the values last printed. If no more
11016 values are available, @code{show values +} produces no display.
11019 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11020 same effect as @samp{show values +}.
11022 @node Convenience Vars
11023 @section Convenience Variables
11025 @cindex convenience variables
11026 @cindex user-defined variables
11027 @value{GDBN} provides @dfn{convenience variables} that you can use within
11028 @value{GDBN} to hold on to a value and refer to it later. These variables
11029 exist entirely within @value{GDBN}; they are not part of your program, and
11030 setting a convenience variable has no direct effect on further execution
11031 of your program. That is why you can use them freely.
11033 Convenience variables are prefixed with @samp{$}. Any name preceded by
11034 @samp{$} can be used for a convenience variable, unless it is one of
11035 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11036 (Value history references, in contrast, are @emph{numbers} preceded
11037 by @samp{$}. @xref{Value History, ,Value History}.)
11039 You can save a value in a convenience variable with an assignment
11040 expression, just as you would set a variable in your program.
11044 set $foo = *object_ptr
11048 would save in @code{$foo} the value contained in the object pointed to by
11051 Using a convenience variable for the first time creates it, but its
11052 value is @code{void} until you assign a new value. You can alter the
11053 value with another assignment at any time.
11055 Convenience variables have no fixed types. You can assign a convenience
11056 variable any type of value, including structures and arrays, even if
11057 that variable already has a value of a different type. The convenience
11058 variable, when used as an expression, has the type of its current value.
11061 @kindex show convenience
11062 @cindex show all user variables and functions
11063 @item show convenience
11064 Print a list of convenience variables used so far, and their values,
11065 as well as a list of the convenience functions.
11066 Abbreviated @code{show conv}.
11068 @kindex init-if-undefined
11069 @cindex convenience variables, initializing
11070 @item init-if-undefined $@var{variable} = @var{expression}
11071 Set a convenience variable if it has not already been set. This is useful
11072 for user-defined commands that keep some state. It is similar, in concept,
11073 to using local static variables with initializers in C (except that
11074 convenience variables are global). It can also be used to allow users to
11075 override default values used in a command script.
11077 If the variable is already defined then the expression is not evaluated so
11078 any side-effects do not occur.
11081 One of the ways to use a convenience variable is as a counter to be
11082 incremented or a pointer to be advanced. For example, to print
11083 a field from successive elements of an array of structures:
11087 print bar[$i++]->contents
11091 Repeat that command by typing @key{RET}.
11093 Some convenience variables are created automatically by @value{GDBN} and given
11094 values likely to be useful.
11097 @vindex $_@r{, convenience variable}
11099 The variable @code{$_} is automatically set by the @code{x} command to
11100 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11101 commands which provide a default address for @code{x} to examine also
11102 set @code{$_} to that address; these commands include @code{info line}
11103 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11104 except when set by the @code{x} command, in which case it is a pointer
11105 to the type of @code{$__}.
11107 @vindex $__@r{, convenience variable}
11109 The variable @code{$__} is automatically set by the @code{x} command
11110 to the value found in the last address examined. Its type is chosen
11111 to match the format in which the data was printed.
11114 @vindex $_exitcode@r{, convenience variable}
11115 When the program being debugged terminates normally, @value{GDBN}
11116 automatically sets this variable to the exit code of the program, and
11117 resets @code{$_exitsignal} to @code{void}.
11120 @vindex $_exitsignal@r{, convenience variable}
11121 When the program being debugged dies due to an uncaught signal,
11122 @value{GDBN} automatically sets this variable to that signal's number,
11123 and resets @code{$_exitcode} to @code{void}.
11125 To distinguish between whether the program being debugged has exited
11126 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11127 @code{$_exitsignal} is not @code{void}), the convenience function
11128 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11129 Functions}). For example, considering the following source code:
11132 #include <signal.h>
11135 main (int argc, char *argv[])
11142 A valid way of telling whether the program being debugged has exited
11143 or signalled would be:
11146 (@value{GDBP}) define has_exited_or_signalled
11147 Type commands for definition of ``has_exited_or_signalled''.
11148 End with a line saying just ``end''.
11149 >if $_isvoid ($_exitsignal)
11150 >echo The program has exited\n
11152 >echo The program has signalled\n
11158 Program terminated with signal SIGALRM, Alarm clock.
11159 The program no longer exists.
11160 (@value{GDBP}) has_exited_or_signalled
11161 The program has signalled
11164 As can be seen, @value{GDBN} correctly informs that the program being
11165 debugged has signalled, since it calls @code{raise} and raises a
11166 @code{SIGALRM} signal. If the program being debugged had not called
11167 @code{raise}, then @value{GDBN} would report a normal exit:
11170 (@value{GDBP}) has_exited_or_signalled
11171 The program has exited
11175 The variable @code{$_exception} is set to the exception object being
11176 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11179 @itemx $_probe_arg0@dots{}$_probe_arg11
11180 Arguments to a static probe. @xref{Static Probe Points}.
11183 @vindex $_sdata@r{, inspect, convenience variable}
11184 The variable @code{$_sdata} contains extra collected static tracepoint
11185 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11186 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11187 if extra static tracepoint data has not been collected.
11190 @vindex $_siginfo@r{, convenience variable}
11191 The variable @code{$_siginfo} contains extra signal information
11192 (@pxref{extra signal information}). Note that @code{$_siginfo}
11193 could be empty, if the application has not yet received any signals.
11194 For example, it will be empty before you execute the @code{run} command.
11197 @vindex $_tlb@r{, convenience variable}
11198 The variable @code{$_tlb} is automatically set when debugging
11199 applications running on MS-Windows in native mode or connected to
11200 gdbserver that supports the @code{qGetTIBAddr} request.
11201 @xref{General Query Packets}.
11202 This variable contains the address of the thread information block.
11205 The number of the current inferior. @xref{Inferiors and
11206 Programs, ,Debugging Multiple Inferiors and Programs}.
11209 The thread number of the current thread. @xref{thread numbers}.
11212 The global number of the current thread. @xref{global thread numbers}.
11216 @node Convenience Funs
11217 @section Convenience Functions
11219 @cindex convenience functions
11220 @value{GDBN} also supplies some @dfn{convenience functions}. These
11221 have a syntax similar to convenience variables. A convenience
11222 function can be used in an expression just like an ordinary function;
11223 however, a convenience function is implemented internally to
11226 These functions do not require @value{GDBN} to be configured with
11227 @code{Python} support, which means that they are always available.
11231 @item $_isvoid (@var{expr})
11232 @findex $_isvoid@r{, convenience function}
11233 Return one if the expression @var{expr} is @code{void}. Otherwise it
11236 A @code{void} expression is an expression where the type of the result
11237 is @code{void}. For example, you can examine a convenience variable
11238 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11242 (@value{GDBP}) print $_exitcode
11244 (@value{GDBP}) print $_isvoid ($_exitcode)
11247 Starting program: ./a.out
11248 [Inferior 1 (process 29572) exited normally]
11249 (@value{GDBP}) print $_exitcode
11251 (@value{GDBP}) print $_isvoid ($_exitcode)
11255 In the example above, we used @code{$_isvoid} to check whether
11256 @code{$_exitcode} is @code{void} before and after the execution of the
11257 program being debugged. Before the execution there is no exit code to
11258 be examined, therefore @code{$_exitcode} is @code{void}. After the
11259 execution the program being debugged returned zero, therefore
11260 @code{$_exitcode} is zero, which means that it is not @code{void}
11263 The @code{void} expression can also be a call of a function from the
11264 program being debugged. For example, given the following function:
11273 The result of calling it inside @value{GDBN} is @code{void}:
11276 (@value{GDBP}) print foo ()
11278 (@value{GDBP}) print $_isvoid (foo ())
11280 (@value{GDBP}) set $v = foo ()
11281 (@value{GDBP}) print $v
11283 (@value{GDBP}) print $_isvoid ($v)
11289 These functions require @value{GDBN} to be configured with
11290 @code{Python} support.
11294 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11295 @findex $_memeq@r{, convenience function}
11296 Returns one if the @var{length} bytes at the addresses given by
11297 @var{buf1} and @var{buf2} are equal.
11298 Otherwise it returns zero.
11300 @item $_regex(@var{str}, @var{regex})
11301 @findex $_regex@r{, convenience function}
11302 Returns one if the string @var{str} matches the regular expression
11303 @var{regex}. Otherwise it returns zero.
11304 The syntax of the regular expression is that specified by @code{Python}'s
11305 regular expression support.
11307 @item $_streq(@var{str1}, @var{str2})
11308 @findex $_streq@r{, convenience function}
11309 Returns one if the strings @var{str1} and @var{str2} are equal.
11310 Otherwise it returns zero.
11312 @item $_strlen(@var{str})
11313 @findex $_strlen@r{, convenience function}
11314 Returns the length of string @var{str}.
11316 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11317 @findex $_caller_is@r{, convenience function}
11318 Returns one if the calling function's name is equal to @var{name}.
11319 Otherwise it returns zero.
11321 If the optional argument @var{number_of_frames} is provided,
11322 it is the number of frames up in the stack to look.
11330 at testsuite/gdb.python/py-caller-is.c:21
11331 #1 0x00000000004005a0 in middle_func ()
11332 at testsuite/gdb.python/py-caller-is.c:27
11333 #2 0x00000000004005ab in top_func ()
11334 at testsuite/gdb.python/py-caller-is.c:33
11335 #3 0x00000000004005b6 in main ()
11336 at testsuite/gdb.python/py-caller-is.c:39
11337 (gdb) print $_caller_is ("middle_func")
11339 (gdb) print $_caller_is ("top_func", 2)
11343 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11344 @findex $_caller_matches@r{, convenience function}
11345 Returns one if the calling function's name matches the regular expression
11346 @var{regexp}. Otherwise it returns zero.
11348 If the optional argument @var{number_of_frames} is provided,
11349 it is the number of frames up in the stack to look.
11352 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11353 @findex $_any_caller_is@r{, convenience function}
11354 Returns one if any calling function's name is equal to @var{name}.
11355 Otherwise it returns zero.
11357 If the optional argument @var{number_of_frames} is provided,
11358 it is the number of frames up in the stack to look.
11361 This function differs from @code{$_caller_is} in that this function
11362 checks all stack frames from the immediate caller to the frame specified
11363 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11364 frame specified by @var{number_of_frames}.
11366 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11367 @findex $_any_caller_matches@r{, convenience function}
11368 Returns one if any calling function's name matches the regular expression
11369 @var{regexp}. Otherwise it returns zero.
11371 If the optional argument @var{number_of_frames} is provided,
11372 it is the number of frames up in the stack to look.
11375 This function differs from @code{$_caller_matches} in that this function
11376 checks all stack frames from the immediate caller to the frame specified
11377 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11378 frame specified by @var{number_of_frames}.
11380 @item $_as_string(@var{value})
11381 @findex $_as_string@r{, convenience function}
11382 Return the string representation of @var{value}.
11384 This function is useful to obtain the textual label (enumerator) of an
11385 enumeration value. For example, assuming the variable @var{node} is of
11386 an enumerated type:
11389 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11390 Visiting node of type NODE_INTEGER
11395 @value{GDBN} provides the ability to list and get help on
11396 convenience functions.
11399 @item help function
11400 @kindex help function
11401 @cindex show all convenience functions
11402 Print a list of all convenience functions.
11409 You can refer to machine register contents, in expressions, as variables
11410 with names starting with @samp{$}. The names of registers are different
11411 for each machine; use @code{info registers} to see the names used on
11415 @kindex info registers
11416 @item info registers
11417 Print the names and values of all registers except floating-point
11418 and vector registers (in the selected stack frame).
11420 @kindex info all-registers
11421 @cindex floating point registers
11422 @item info all-registers
11423 Print the names and values of all registers, including floating-point
11424 and vector registers (in the selected stack frame).
11426 @item info registers @var{reggroup} @dots{}
11427 Print the name and value of the registers in each of the specified
11428 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11429 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11431 @item info registers @var{regname} @dots{}
11432 Print the @dfn{relativized} value of each specified register @var{regname}.
11433 As discussed in detail below, register values are normally relative to
11434 the selected stack frame. The @var{regname} may be any register name valid on
11435 the machine you are using, with or without the initial @samp{$}.
11438 @anchor{standard registers}
11439 @cindex stack pointer register
11440 @cindex program counter register
11441 @cindex process status register
11442 @cindex frame pointer register
11443 @cindex standard registers
11444 @value{GDBN} has four ``standard'' register names that are available (in
11445 expressions) on most machines---whenever they do not conflict with an
11446 architecture's canonical mnemonics for registers. The register names
11447 @code{$pc} and @code{$sp} are used for the program counter register and
11448 the stack pointer. @code{$fp} is used for a register that contains a
11449 pointer to the current stack frame, and @code{$ps} is used for a
11450 register that contains the processor status. For example,
11451 you could print the program counter in hex with
11458 or print the instruction to be executed next with
11465 or add four to the stack pointer@footnote{This is a way of removing
11466 one word from the stack, on machines where stacks grow downward in
11467 memory (most machines, nowadays). This assumes that the innermost
11468 stack frame is selected; setting @code{$sp} is not allowed when other
11469 stack frames are selected. To pop entire frames off the stack,
11470 regardless of machine architecture, use @code{return};
11471 see @ref{Returning, ,Returning from a Function}.} with
11477 Whenever possible, these four standard register names are available on
11478 your machine even though the machine has different canonical mnemonics,
11479 so long as there is no conflict. The @code{info registers} command
11480 shows the canonical names. For example, on the SPARC, @code{info
11481 registers} displays the processor status register as @code{$psr} but you
11482 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11483 is an alias for the @sc{eflags} register.
11485 @value{GDBN} always considers the contents of an ordinary register as an
11486 integer when the register is examined in this way. Some machines have
11487 special registers which can hold nothing but floating point; these
11488 registers are considered to have floating point values. There is no way
11489 to refer to the contents of an ordinary register as floating point value
11490 (although you can @emph{print} it as a floating point value with
11491 @samp{print/f $@var{regname}}).
11493 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11494 means that the data format in which the register contents are saved by
11495 the operating system is not the same one that your program normally
11496 sees. For example, the registers of the 68881 floating point
11497 coprocessor are always saved in ``extended'' (raw) format, but all C
11498 programs expect to work with ``double'' (virtual) format. In such
11499 cases, @value{GDBN} normally works with the virtual format only (the format
11500 that makes sense for your program), but the @code{info registers} command
11501 prints the data in both formats.
11503 @cindex SSE registers (x86)
11504 @cindex MMX registers (x86)
11505 Some machines have special registers whose contents can be interpreted
11506 in several different ways. For example, modern x86-based machines
11507 have SSE and MMX registers that can hold several values packed
11508 together in several different formats. @value{GDBN} refers to such
11509 registers in @code{struct} notation:
11512 (@value{GDBP}) print $xmm1
11514 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11515 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11516 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11517 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11518 v4_int32 = @{0, 20657912, 11, 13@},
11519 v2_int64 = @{88725056443645952, 55834574859@},
11520 uint128 = 0x0000000d0000000b013b36f800000000
11525 To set values of such registers, you need to tell @value{GDBN} which
11526 view of the register you wish to change, as if you were assigning
11527 value to a @code{struct} member:
11530 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11533 Normally, register values are relative to the selected stack frame
11534 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11535 value that the register would contain if all stack frames farther in
11536 were exited and their saved registers restored. In order to see the
11537 true contents of hardware registers, you must select the innermost
11538 frame (with @samp{frame 0}).
11540 @cindex caller-saved registers
11541 @cindex call-clobbered registers
11542 @cindex volatile registers
11543 @cindex <not saved> values
11544 Usually ABIs reserve some registers as not needed to be saved by the
11545 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11546 registers). It may therefore not be possible for @value{GDBN} to know
11547 the value a register had before the call (in other words, in the outer
11548 frame), if the register value has since been changed by the callee.
11549 @value{GDBN} tries to deduce where the inner frame saved
11550 (``callee-saved'') registers, from the debug info, unwind info, or the
11551 machine code generated by your compiler. If some register is not
11552 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11553 its own knowledge of the ABI, or because the debug/unwind info
11554 explicitly says the register's value is undefined), @value{GDBN}
11555 displays @w{@samp{<not saved>}} as the register's value. With targets
11556 that @value{GDBN} has no knowledge of the register saving convention,
11557 if a register was not saved by the callee, then its value and location
11558 in the outer frame are assumed to be the same of the inner frame.
11559 This is usually harmless, because if the register is call-clobbered,
11560 the caller either does not care what is in the register after the
11561 call, or has code to restore the value that it does care about. Note,
11562 however, that if you change such a register in the outer frame, you
11563 may also be affecting the inner frame. Also, the more ``outer'' the
11564 frame is you're looking at, the more likely a call-clobbered
11565 register's value is to be wrong, in the sense that it doesn't actually
11566 represent the value the register had just before the call.
11568 @node Floating Point Hardware
11569 @section Floating Point Hardware
11570 @cindex floating point
11572 Depending on the configuration, @value{GDBN} may be able to give
11573 you more information about the status of the floating point hardware.
11578 Display hardware-dependent information about the floating
11579 point unit. The exact contents and layout vary depending on the
11580 floating point chip. Currently, @samp{info float} is supported on
11581 the ARM and x86 machines.
11585 @section Vector Unit
11586 @cindex vector unit
11588 Depending on the configuration, @value{GDBN} may be able to give you
11589 more information about the status of the vector unit.
11592 @kindex info vector
11594 Display information about the vector unit. The exact contents and
11595 layout vary depending on the hardware.
11598 @node OS Information
11599 @section Operating System Auxiliary Information
11600 @cindex OS information
11602 @value{GDBN} provides interfaces to useful OS facilities that can help
11603 you debug your program.
11605 @cindex auxiliary vector
11606 @cindex vector, auxiliary
11607 Some operating systems supply an @dfn{auxiliary vector} to programs at
11608 startup. This is akin to the arguments and environment that you
11609 specify for a program, but contains a system-dependent variety of
11610 binary values that tell system libraries important details about the
11611 hardware, operating system, and process. Each value's purpose is
11612 identified by an integer tag; the meanings are well-known but system-specific.
11613 Depending on the configuration and operating system facilities,
11614 @value{GDBN} may be able to show you this information. For remote
11615 targets, this functionality may further depend on the remote stub's
11616 support of the @samp{qXfer:auxv:read} packet, see
11617 @ref{qXfer auxiliary vector read}.
11622 Display the auxiliary vector of the inferior, which can be either a
11623 live process or a core dump file. @value{GDBN} prints each tag value
11624 numerically, and also shows names and text descriptions for recognized
11625 tags. Some values in the vector are numbers, some bit masks, and some
11626 pointers to strings or other data. @value{GDBN} displays each value in the
11627 most appropriate form for a recognized tag, and in hexadecimal for
11628 an unrecognized tag.
11631 On some targets, @value{GDBN} can access operating system-specific
11632 information and show it to you. The types of information available
11633 will differ depending on the type of operating system running on the
11634 target. The mechanism used to fetch the data is described in
11635 @ref{Operating System Information}. For remote targets, this
11636 functionality depends on the remote stub's support of the
11637 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11641 @item info os @var{infotype}
11643 Display OS information of the requested type.
11645 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11647 @anchor{linux info os infotypes}
11649 @kindex info os cpus
11651 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11652 the available fields from /proc/cpuinfo. For each supported architecture
11653 different fields are available. Two common entries are processor which gives
11654 CPU number and bogomips; a system constant that is calculated during
11655 kernel initialization.
11657 @kindex info os files
11659 Display the list of open file descriptors on the target. For each
11660 file descriptor, @value{GDBN} prints the identifier of the process
11661 owning the descriptor, the command of the owning process, the value
11662 of the descriptor, and the target of the descriptor.
11664 @kindex info os modules
11666 Display the list of all loaded kernel modules on the target. For each
11667 module, @value{GDBN} prints the module name, the size of the module in
11668 bytes, the number of times the module is used, the dependencies of the
11669 module, the status of the module, and the address of the loaded module
11672 @kindex info os msg
11674 Display the list of all System V message queues on the target. For each
11675 message queue, @value{GDBN} prints the message queue key, the message
11676 queue identifier, the access permissions, the current number of bytes
11677 on the queue, the current number of messages on the queue, the processes
11678 that last sent and received a message on the queue, the user and group
11679 of the owner and creator of the message queue, the times at which a
11680 message was last sent and received on the queue, and the time at which
11681 the message queue was last changed.
11683 @kindex info os processes
11685 Display the list of processes on the target. For each process,
11686 @value{GDBN} prints the process identifier, the name of the user, the
11687 command corresponding to the process, and the list of processor cores
11688 that the process is currently running on. (To understand what these
11689 properties mean, for this and the following info types, please consult
11690 the general @sc{gnu}/Linux documentation.)
11692 @kindex info os procgroups
11694 Display the list of process groups on the target. For each process,
11695 @value{GDBN} prints the identifier of the process group that it belongs
11696 to, the command corresponding to the process group leader, the process
11697 identifier, and the command line of the process. The list is sorted
11698 first by the process group identifier, then by the process identifier,
11699 so that processes belonging to the same process group are grouped together
11700 and the process group leader is listed first.
11702 @kindex info os semaphores
11704 Display the list of all System V semaphore sets on the target. For each
11705 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11706 set identifier, the access permissions, the number of semaphores in the
11707 set, the user and group of the owner and creator of the semaphore set,
11708 and the times at which the semaphore set was operated upon and changed.
11710 @kindex info os shm
11712 Display the list of all System V shared-memory regions on the target.
11713 For each shared-memory region, @value{GDBN} prints the region key,
11714 the shared-memory identifier, the access permissions, the size of the
11715 region, the process that created the region, the process that last
11716 attached to or detached from the region, the current number of live
11717 attaches to the region, and the times at which the region was last
11718 attached to, detach from, and changed.
11720 @kindex info os sockets
11722 Display the list of Internet-domain sockets on the target. For each
11723 socket, @value{GDBN} prints the address and port of the local and
11724 remote endpoints, the current state of the connection, the creator of
11725 the socket, the IP address family of the socket, and the type of the
11728 @kindex info os threads
11730 Display the list of threads running on the target. For each thread,
11731 @value{GDBN} prints the identifier of the process that the thread
11732 belongs to, the command of the process, the thread identifier, and the
11733 processor core that it is currently running on. The main thread of a
11734 process is not listed.
11738 If @var{infotype} is omitted, then list the possible values for
11739 @var{infotype} and the kind of OS information available for each
11740 @var{infotype}. If the target does not return a list of possible
11741 types, this command will report an error.
11744 @node Memory Region Attributes
11745 @section Memory Region Attributes
11746 @cindex memory region attributes
11748 @dfn{Memory region attributes} allow you to describe special handling
11749 required by regions of your target's memory. @value{GDBN} uses
11750 attributes to determine whether to allow certain types of memory
11751 accesses; whether to use specific width accesses; and whether to cache
11752 target memory. By default the description of memory regions is
11753 fetched from the target (if the current target supports this), but the
11754 user can override the fetched regions.
11756 Defined memory regions can be individually enabled and disabled. When a
11757 memory region is disabled, @value{GDBN} uses the default attributes when
11758 accessing memory in that region. Similarly, if no memory regions have
11759 been defined, @value{GDBN} uses the default attributes when accessing
11762 When a memory region is defined, it is given a number to identify it;
11763 to enable, disable, or remove a memory region, you specify that number.
11767 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11768 Define a memory region bounded by @var{lower} and @var{upper} with
11769 attributes @var{attributes}@dots{}, and add it to the list of regions
11770 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11771 case: it is treated as the target's maximum memory address.
11772 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11775 Discard any user changes to the memory regions and use target-supplied
11776 regions, if available, or no regions if the target does not support.
11779 @item delete mem @var{nums}@dots{}
11780 Remove memory regions @var{nums}@dots{} from the list of regions
11781 monitored by @value{GDBN}.
11783 @kindex disable mem
11784 @item disable mem @var{nums}@dots{}
11785 Disable monitoring of memory regions @var{nums}@dots{}.
11786 A disabled memory region is not forgotten.
11787 It may be enabled again later.
11790 @item enable mem @var{nums}@dots{}
11791 Enable monitoring of memory regions @var{nums}@dots{}.
11795 Print a table of all defined memory regions, with the following columns
11799 @item Memory Region Number
11800 @item Enabled or Disabled.
11801 Enabled memory regions are marked with @samp{y}.
11802 Disabled memory regions are marked with @samp{n}.
11805 The address defining the inclusive lower bound of the memory region.
11808 The address defining the exclusive upper bound of the memory region.
11811 The list of attributes set for this memory region.
11816 @subsection Attributes
11818 @subsubsection Memory Access Mode
11819 The access mode attributes set whether @value{GDBN} may make read or
11820 write accesses to a memory region.
11822 While these attributes prevent @value{GDBN} from performing invalid
11823 memory accesses, they do nothing to prevent the target system, I/O DMA,
11824 etc.@: from accessing memory.
11828 Memory is read only.
11830 Memory is write only.
11832 Memory is read/write. This is the default.
11835 @subsubsection Memory Access Size
11836 The access size attribute tells @value{GDBN} to use specific sized
11837 accesses in the memory region. Often memory mapped device registers
11838 require specific sized accesses. If no access size attribute is
11839 specified, @value{GDBN} may use accesses of any size.
11843 Use 8 bit memory accesses.
11845 Use 16 bit memory accesses.
11847 Use 32 bit memory accesses.
11849 Use 64 bit memory accesses.
11852 @c @subsubsection Hardware/Software Breakpoints
11853 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11854 @c will use hardware or software breakpoints for the internal breakpoints
11855 @c used by the step, next, finish, until, etc. commands.
11859 @c Always use hardware breakpoints
11860 @c @item swbreak (default)
11863 @subsubsection Data Cache
11864 The data cache attributes set whether @value{GDBN} will cache target
11865 memory. While this generally improves performance by reducing debug
11866 protocol overhead, it can lead to incorrect results because @value{GDBN}
11867 does not know about volatile variables or memory mapped device
11872 Enable @value{GDBN} to cache target memory.
11874 Disable @value{GDBN} from caching target memory. This is the default.
11877 @subsection Memory Access Checking
11878 @value{GDBN} can be instructed to refuse accesses to memory that is
11879 not explicitly described. This can be useful if accessing such
11880 regions has undesired effects for a specific target, or to provide
11881 better error checking. The following commands control this behaviour.
11884 @kindex set mem inaccessible-by-default
11885 @item set mem inaccessible-by-default [on|off]
11886 If @code{on} is specified, make @value{GDBN} treat memory not
11887 explicitly described by the memory ranges as non-existent and refuse accesses
11888 to such memory. The checks are only performed if there's at least one
11889 memory range defined. If @code{off} is specified, make @value{GDBN}
11890 treat the memory not explicitly described by the memory ranges as RAM.
11891 The default value is @code{on}.
11892 @kindex show mem inaccessible-by-default
11893 @item show mem inaccessible-by-default
11894 Show the current handling of accesses to unknown memory.
11898 @c @subsubsection Memory Write Verification
11899 @c The memory write verification attributes set whether @value{GDBN}
11900 @c will re-reads data after each write to verify the write was successful.
11904 @c @item noverify (default)
11907 @node Dump/Restore Files
11908 @section Copy Between Memory and a File
11909 @cindex dump/restore files
11910 @cindex append data to a file
11911 @cindex dump data to a file
11912 @cindex restore data from a file
11914 You can use the commands @code{dump}, @code{append}, and
11915 @code{restore} to copy data between target memory and a file. The
11916 @code{dump} and @code{append} commands write data to a file, and the
11917 @code{restore} command reads data from a file back into the inferior's
11918 memory. Files may be in binary, Motorola S-record, Intel hex,
11919 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11920 append to binary files, and cannot read from Verilog Hex files.
11925 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11926 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11927 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11928 or the value of @var{expr}, to @var{filename} in the given format.
11930 The @var{format} parameter may be any one of:
11937 Motorola S-record format.
11939 Tektronix Hex format.
11941 Verilog Hex format.
11944 @value{GDBN} uses the same definitions of these formats as the
11945 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11946 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11950 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11951 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11952 Append the contents of memory from @var{start_addr} to @var{end_addr},
11953 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11954 (@value{GDBN} can only append data to files in raw binary form.)
11957 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11958 Restore the contents of file @var{filename} into memory. The
11959 @code{restore} command can automatically recognize any known @sc{bfd}
11960 file format, except for raw binary. To restore a raw binary file you
11961 must specify the optional keyword @code{binary} after the filename.
11963 If @var{bias} is non-zero, its value will be added to the addresses
11964 contained in the file. Binary files always start at address zero, so
11965 they will be restored at address @var{bias}. Other bfd files have
11966 a built-in location; they will be restored at offset @var{bias}
11967 from that location.
11969 If @var{start} and/or @var{end} are non-zero, then only data between
11970 file offset @var{start} and file offset @var{end} will be restored.
11971 These offsets are relative to the addresses in the file, before
11972 the @var{bias} argument is applied.
11976 @node Core File Generation
11977 @section How to Produce a Core File from Your Program
11978 @cindex dump core from inferior
11980 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11981 image of a running process and its process status (register values
11982 etc.). Its primary use is post-mortem debugging of a program that
11983 crashed while it ran outside a debugger. A program that crashes
11984 automatically produces a core file, unless this feature is disabled by
11985 the user. @xref{Files}, for information on invoking @value{GDBN} in
11986 the post-mortem debugging mode.
11988 Occasionally, you may wish to produce a core file of the program you
11989 are debugging in order to preserve a snapshot of its state.
11990 @value{GDBN} has a special command for that.
11994 @kindex generate-core-file
11995 @item generate-core-file [@var{file}]
11996 @itemx gcore [@var{file}]
11997 Produce a core dump of the inferior process. The optional argument
11998 @var{file} specifies the file name where to put the core dump. If not
11999 specified, the file name defaults to @file{core.@var{pid}}, where
12000 @var{pid} is the inferior process ID.
12002 Note that this command is implemented only for some systems (as of
12003 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12005 On @sc{gnu}/Linux, this command can take into account the value of the
12006 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12007 dump (@pxref{set use-coredump-filter}), and by default honors the
12008 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12009 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12011 @kindex set use-coredump-filter
12012 @anchor{set use-coredump-filter}
12013 @item set use-coredump-filter on
12014 @itemx set use-coredump-filter off
12015 Enable or disable the use of the file
12016 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12017 files. This file is used by the Linux kernel to decide what types of
12018 memory mappings will be dumped or ignored when generating a core dump
12019 file. @var{pid} is the process ID of a currently running process.
12021 To make use of this feature, you have to write in the
12022 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12023 which is a bit mask representing the memory mapping types. If a bit
12024 is set in the bit mask, then the memory mappings of the corresponding
12025 types will be dumped; otherwise, they will be ignored. This
12026 configuration is inherited by child processes. For more information
12027 about the bits that can be set in the
12028 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12029 manpage of @code{core(5)}.
12031 By default, this option is @code{on}. If this option is turned
12032 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12033 and instead uses the same default value as the Linux kernel in order
12034 to decide which pages will be dumped in the core dump file. This
12035 value is currently @code{0x33}, which means that bits @code{0}
12036 (anonymous private mappings), @code{1} (anonymous shared mappings),
12037 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12038 This will cause these memory mappings to be dumped automatically.
12040 @kindex set dump-excluded-mappings
12041 @anchor{set dump-excluded-mappings}
12042 @item set dump-excluded-mappings on
12043 @itemx set dump-excluded-mappings off
12044 If @code{on} is specified, @value{GDBN} will dump memory mappings
12045 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12046 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12048 The default value is @code{off}.
12051 @node Character Sets
12052 @section Character Sets
12053 @cindex character sets
12055 @cindex translating between character sets
12056 @cindex host character set
12057 @cindex target character set
12059 If the program you are debugging uses a different character set to
12060 represent characters and strings than the one @value{GDBN} uses itself,
12061 @value{GDBN} can automatically translate between the character sets for
12062 you. The character set @value{GDBN} uses we call the @dfn{host
12063 character set}; the one the inferior program uses we call the
12064 @dfn{target character set}.
12066 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12067 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12068 remote protocol (@pxref{Remote Debugging}) to debug a program
12069 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12070 then the host character set is Latin-1, and the target character set is
12071 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12072 target-charset EBCDIC-US}, then @value{GDBN} translates between
12073 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12074 character and string literals in expressions.
12076 @value{GDBN} has no way to automatically recognize which character set
12077 the inferior program uses; you must tell it, using the @code{set
12078 target-charset} command, described below.
12080 Here are the commands for controlling @value{GDBN}'s character set
12084 @item set target-charset @var{charset}
12085 @kindex set target-charset
12086 Set the current target character set to @var{charset}. To display the
12087 list of supported target character sets, type
12088 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12090 @item set host-charset @var{charset}
12091 @kindex set host-charset
12092 Set the current host character set to @var{charset}.
12094 By default, @value{GDBN} uses a host character set appropriate to the
12095 system it is running on; you can override that default using the
12096 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12097 automatically determine the appropriate host character set. In this
12098 case, @value{GDBN} uses @samp{UTF-8}.
12100 @value{GDBN} can only use certain character sets as its host character
12101 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12102 @value{GDBN} will list the host character sets it supports.
12104 @item set charset @var{charset}
12105 @kindex set charset
12106 Set the current host and target character sets to @var{charset}. As
12107 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12108 @value{GDBN} will list the names of the character sets that can be used
12109 for both host and target.
12112 @kindex show charset
12113 Show the names of the current host and target character sets.
12115 @item show host-charset
12116 @kindex show host-charset
12117 Show the name of the current host character set.
12119 @item show target-charset
12120 @kindex show target-charset
12121 Show the name of the current target character set.
12123 @item set target-wide-charset @var{charset}
12124 @kindex set target-wide-charset
12125 Set the current target's wide character set to @var{charset}. This is
12126 the character set used by the target's @code{wchar_t} type. To
12127 display the list of supported wide character sets, type
12128 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12130 @item show target-wide-charset
12131 @kindex show target-wide-charset
12132 Show the name of the current target's wide character set.
12135 Here is an example of @value{GDBN}'s character set support in action.
12136 Assume that the following source code has been placed in the file
12137 @file{charset-test.c}:
12143 = @{72, 101, 108, 108, 111, 44, 32, 119,
12144 111, 114, 108, 100, 33, 10, 0@};
12145 char ibm1047_hello[]
12146 = @{200, 133, 147, 147, 150, 107, 64, 166,
12147 150, 153, 147, 132, 90, 37, 0@};
12151 printf ("Hello, world!\n");
12155 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12156 containing the string @samp{Hello, world!} followed by a newline,
12157 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12159 We compile the program, and invoke the debugger on it:
12162 $ gcc -g charset-test.c -o charset-test
12163 $ gdb -nw charset-test
12164 GNU gdb 2001-12-19-cvs
12165 Copyright 2001 Free Software Foundation, Inc.
12170 We can use the @code{show charset} command to see what character sets
12171 @value{GDBN} is currently using to interpret and display characters and
12175 (@value{GDBP}) show charset
12176 The current host and target character set is `ISO-8859-1'.
12180 For the sake of printing this manual, let's use @sc{ascii} as our
12181 initial character set:
12183 (@value{GDBP}) set charset ASCII
12184 (@value{GDBP}) show charset
12185 The current host and target character set is `ASCII'.
12189 Let's assume that @sc{ascii} is indeed the correct character set for our
12190 host system --- in other words, let's assume that if @value{GDBN} prints
12191 characters using the @sc{ascii} character set, our terminal will display
12192 them properly. Since our current target character set is also
12193 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12196 (@value{GDBP}) print ascii_hello
12197 $1 = 0x401698 "Hello, world!\n"
12198 (@value{GDBP}) print ascii_hello[0]
12203 @value{GDBN} uses the target character set for character and string
12204 literals you use in expressions:
12207 (@value{GDBP}) print '+'
12212 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12215 @value{GDBN} relies on the user to tell it which character set the
12216 target program uses. If we print @code{ibm1047_hello} while our target
12217 character set is still @sc{ascii}, we get jibberish:
12220 (@value{GDBP}) print ibm1047_hello
12221 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12222 (@value{GDBP}) print ibm1047_hello[0]
12227 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12228 @value{GDBN} tells us the character sets it supports:
12231 (@value{GDBP}) set target-charset
12232 ASCII EBCDIC-US IBM1047 ISO-8859-1
12233 (@value{GDBP}) set target-charset
12236 We can select @sc{ibm1047} as our target character set, and examine the
12237 program's strings again. Now the @sc{ascii} string is wrong, but
12238 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12239 target character set, @sc{ibm1047}, to the host character set,
12240 @sc{ascii}, and they display correctly:
12243 (@value{GDBP}) set target-charset IBM1047
12244 (@value{GDBP}) show charset
12245 The current host character set is `ASCII'.
12246 The current target character set is `IBM1047'.
12247 (@value{GDBP}) print ascii_hello
12248 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12249 (@value{GDBP}) print ascii_hello[0]
12251 (@value{GDBP}) print ibm1047_hello
12252 $8 = 0x4016a8 "Hello, world!\n"
12253 (@value{GDBP}) print ibm1047_hello[0]
12258 As above, @value{GDBN} uses the target character set for character and
12259 string literals you use in expressions:
12262 (@value{GDBP}) print '+'
12267 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12270 @node Caching Target Data
12271 @section Caching Data of Targets
12272 @cindex caching data of targets
12274 @value{GDBN} caches data exchanged between the debugger and a target.
12275 Each cache is associated with the address space of the inferior.
12276 @xref{Inferiors and Programs}, about inferior and address space.
12277 Such caching generally improves performance in remote debugging
12278 (@pxref{Remote Debugging}), because it reduces the overhead of the
12279 remote protocol by bundling memory reads and writes into large chunks.
12280 Unfortunately, simply caching everything would lead to incorrect results,
12281 since @value{GDBN} does not necessarily know anything about volatile
12282 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12283 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12285 Therefore, by default, @value{GDBN} only caches data
12286 known to be on the stack@footnote{In non-stop mode, it is moderately
12287 rare for a running thread to modify the stack of a stopped thread
12288 in a way that would interfere with a backtrace, and caching of
12289 stack reads provides a significant speed up of remote backtraces.} or
12290 in the code segment.
12291 Other regions of memory can be explicitly marked as
12292 cacheable; @pxref{Memory Region Attributes}.
12295 @kindex set remotecache
12296 @item set remotecache on
12297 @itemx set remotecache off
12298 This option no longer does anything; it exists for compatibility
12301 @kindex show remotecache
12302 @item show remotecache
12303 Show the current state of the obsolete remotecache flag.
12305 @kindex set stack-cache
12306 @item set stack-cache on
12307 @itemx set stack-cache off
12308 Enable or disable caching of stack accesses. When @code{on}, use
12309 caching. By default, this option is @code{on}.
12311 @kindex show stack-cache
12312 @item show stack-cache
12313 Show the current state of data caching for memory accesses.
12315 @kindex set code-cache
12316 @item set code-cache on
12317 @itemx set code-cache off
12318 Enable or disable caching of code segment accesses. When @code{on},
12319 use caching. By default, this option is @code{on}. This improves
12320 performance of disassembly in remote debugging.
12322 @kindex show code-cache
12323 @item show code-cache
12324 Show the current state of target memory cache for code segment
12327 @kindex info dcache
12328 @item info dcache @r{[}line@r{]}
12329 Print the information about the performance of data cache of the
12330 current inferior's address space. The information displayed
12331 includes the dcache width and depth, and for each cache line, its
12332 number, address, and how many times it was referenced. This
12333 command is useful for debugging the data cache operation.
12335 If a line number is specified, the contents of that line will be
12338 @item set dcache size @var{size}
12339 @cindex dcache size
12340 @kindex set dcache size
12341 Set maximum number of entries in dcache (dcache depth above).
12343 @item set dcache line-size @var{line-size}
12344 @cindex dcache line-size
12345 @kindex set dcache line-size
12346 Set number of bytes each dcache entry caches (dcache width above).
12347 Must be a power of 2.
12349 @item show dcache size
12350 @kindex show dcache size
12351 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12353 @item show dcache line-size
12354 @kindex show dcache line-size
12355 Show default size of dcache lines.
12359 @node Searching Memory
12360 @section Search Memory
12361 @cindex searching memory
12363 Memory can be searched for a particular sequence of bytes with the
12364 @code{find} command.
12368 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12369 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12370 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12371 etc. The search begins at address @var{start_addr} and continues for either
12372 @var{len} bytes or through to @var{end_addr} inclusive.
12375 @var{s} and @var{n} are optional parameters.
12376 They may be specified in either order, apart or together.
12379 @item @var{s}, search query size
12380 The size of each search query value.
12386 halfwords (two bytes)
12390 giant words (eight bytes)
12393 All values are interpreted in the current language.
12394 This means, for example, that if the current source language is C/C@t{++}
12395 then searching for the string ``hello'' includes the trailing '\0'.
12396 The null terminator can be removed from searching by using casts,
12397 e.g.: @samp{@{char[5]@}"hello"}.
12399 If the value size is not specified, it is taken from the
12400 value's type in the current language.
12401 This is useful when one wants to specify the search
12402 pattern as a mixture of types.
12403 Note that this means, for example, that in the case of C-like languages
12404 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12405 which is typically four bytes.
12407 @item @var{n}, maximum number of finds
12408 The maximum number of matches to print. The default is to print all finds.
12411 You can use strings as search values. Quote them with double-quotes
12413 The string value is copied into the search pattern byte by byte,
12414 regardless of the endianness of the target and the size specification.
12416 The address of each match found is printed as well as a count of the
12417 number of matches found.
12419 The address of the last value found is stored in convenience variable
12421 A count of the number of matches is stored in @samp{$numfound}.
12423 For example, if stopped at the @code{printf} in this function:
12429 static char hello[] = "hello-hello";
12430 static struct @{ char c; short s; int i; @}
12431 __attribute__ ((packed)) mixed
12432 = @{ 'c', 0x1234, 0x87654321 @};
12433 printf ("%s\n", hello);
12438 you get during debugging:
12441 (gdb) find &hello[0], +sizeof(hello), "hello"
12442 0x804956d <hello.1620+6>
12444 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12445 0x8049567 <hello.1620>
12446 0x804956d <hello.1620+6>
12448 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12449 0x8049567 <hello.1620>
12450 0x804956d <hello.1620+6>
12452 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12453 0x8049567 <hello.1620>
12455 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12456 0x8049560 <mixed.1625>
12458 (gdb) print $numfound
12461 $2 = (void *) 0x8049560
12465 @section Value Sizes
12467 Whenever @value{GDBN} prints a value memory will be allocated within
12468 @value{GDBN} to hold the contents of the value. It is possible in
12469 some languages with dynamic typing systems, that an invalid program
12470 may indicate a value that is incorrectly large, this in turn may cause
12471 @value{GDBN} to try and allocate an overly large ammount of memory.
12474 @kindex set max-value-size
12475 @item set max-value-size @var{bytes}
12476 @itemx set max-value-size unlimited
12477 Set the maximum size of memory that @value{GDBN} will allocate for the
12478 contents of a value to @var{bytes}, trying to display a value that
12479 requires more memory than that will result in an error.
12481 Setting this variable does not effect values that have already been
12482 allocated within @value{GDBN}, only future allocations.
12484 There's a minimum size that @code{max-value-size} can be set to in
12485 order that @value{GDBN} can still operate correctly, this minimum is
12486 currently 16 bytes.
12488 The limit applies to the results of some subexpressions as well as to
12489 complete expressions. For example, an expression denoting a simple
12490 integer component, such as @code{x.y.z}, may fail if the size of
12491 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12492 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12493 @var{A} is an array variable with non-constant size, will generally
12494 succeed regardless of the bounds on @var{A}, as long as the component
12495 size is less than @var{bytes}.
12497 The default value of @code{max-value-size} is currently 64k.
12499 @kindex show max-value-size
12500 @item show max-value-size
12501 Show the maximum size of memory, in bytes, that @value{GDBN} will
12502 allocate for the contents of a value.
12505 @node Optimized Code
12506 @chapter Debugging Optimized Code
12507 @cindex optimized code, debugging
12508 @cindex debugging optimized code
12510 Almost all compilers support optimization. With optimization
12511 disabled, the compiler generates assembly code that corresponds
12512 directly to your source code, in a simplistic way. As the compiler
12513 applies more powerful optimizations, the generated assembly code
12514 diverges from your original source code. With help from debugging
12515 information generated by the compiler, @value{GDBN} can map from
12516 the running program back to constructs from your original source.
12518 @value{GDBN} is more accurate with optimization disabled. If you
12519 can recompile without optimization, it is easier to follow the
12520 progress of your program during debugging. But, there are many cases
12521 where you may need to debug an optimized version.
12523 When you debug a program compiled with @samp{-g -O}, remember that the
12524 optimizer has rearranged your code; the debugger shows you what is
12525 really there. Do not be too surprised when the execution path does not
12526 exactly match your source file! An extreme example: if you define a
12527 variable, but never use it, @value{GDBN} never sees that
12528 variable---because the compiler optimizes it out of existence.
12530 Some things do not work as well with @samp{-g -O} as with just
12531 @samp{-g}, particularly on machines with instruction scheduling. If in
12532 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12533 please report it to us as a bug (including a test case!).
12534 @xref{Variables}, for more information about debugging optimized code.
12537 * Inline Functions:: How @value{GDBN} presents inlining
12538 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12541 @node Inline Functions
12542 @section Inline Functions
12543 @cindex inline functions, debugging
12545 @dfn{Inlining} is an optimization that inserts a copy of the function
12546 body directly at each call site, instead of jumping to a shared
12547 routine. @value{GDBN} displays inlined functions just like
12548 non-inlined functions. They appear in backtraces. You can view their
12549 arguments and local variables, step into them with @code{step}, skip
12550 them with @code{next}, and escape from them with @code{finish}.
12551 You can check whether a function was inlined by using the
12552 @code{info frame} command.
12554 For @value{GDBN} to support inlined functions, the compiler must
12555 record information about inlining in the debug information ---
12556 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12557 other compilers do also. @value{GDBN} only supports inlined functions
12558 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12559 do not emit two required attributes (@samp{DW_AT_call_file} and
12560 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12561 function calls with earlier versions of @value{NGCC}. It instead
12562 displays the arguments and local variables of inlined functions as
12563 local variables in the caller.
12565 The body of an inlined function is directly included at its call site;
12566 unlike a non-inlined function, there are no instructions devoted to
12567 the call. @value{GDBN} still pretends that the call site and the
12568 start of the inlined function are different instructions. Stepping to
12569 the call site shows the call site, and then stepping again shows
12570 the first line of the inlined function, even though no additional
12571 instructions are executed.
12573 This makes source-level debugging much clearer; you can see both the
12574 context of the call and then the effect of the call. Only stepping by
12575 a single instruction using @code{stepi} or @code{nexti} does not do
12576 this; single instruction steps always show the inlined body.
12578 There are some ways that @value{GDBN} does not pretend that inlined
12579 function calls are the same as normal calls:
12583 Setting breakpoints at the call site of an inlined function may not
12584 work, because the call site does not contain any code. @value{GDBN}
12585 may incorrectly move the breakpoint to the next line of the enclosing
12586 function, after the call. This limitation will be removed in a future
12587 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12588 or inside the inlined function instead.
12591 @value{GDBN} cannot locate the return value of inlined calls after
12592 using the @code{finish} command. This is a limitation of compiler-generated
12593 debugging information; after @code{finish}, you can step to the next line
12594 and print a variable where your program stored the return value.
12598 @node Tail Call Frames
12599 @section Tail Call Frames
12600 @cindex tail call frames, debugging
12602 Function @code{B} can call function @code{C} in its very last statement. In
12603 unoptimized compilation the call of @code{C} is immediately followed by return
12604 instruction at the end of @code{B} code. Optimizing compiler may replace the
12605 call and return in function @code{B} into one jump to function @code{C}
12606 instead. Such use of a jump instruction is called @dfn{tail call}.
12608 During execution of function @code{C}, there will be no indication in the
12609 function call stack frames that it was tail-called from @code{B}. If function
12610 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12611 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12612 some cases @value{GDBN} can determine that @code{C} was tail-called from
12613 @code{B}, and it will then create fictitious call frame for that, with the
12614 return address set up as if @code{B} called @code{C} normally.
12616 This functionality is currently supported only by DWARF 2 debugging format and
12617 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12618 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12621 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12622 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12626 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12628 Stack level 1, frame at 0x7fffffffda30:
12629 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12630 tail call frame, caller of frame at 0x7fffffffda30
12631 source language c++.
12632 Arglist at unknown address.
12633 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12636 The detection of all the possible code path executions can find them ambiguous.
12637 There is no execution history stored (possible @ref{Reverse Execution} is never
12638 used for this purpose) and the last known caller could have reached the known
12639 callee by multiple different jump sequences. In such case @value{GDBN} still
12640 tries to show at least all the unambiguous top tail callers and all the
12641 unambiguous bottom tail calees, if any.
12644 @anchor{set debug entry-values}
12645 @item set debug entry-values
12646 @kindex set debug entry-values
12647 When set to on, enables printing of analysis messages for both frame argument
12648 values at function entry and tail calls. It will show all the possible valid
12649 tail calls code paths it has considered. It will also print the intersection
12650 of them with the final unambiguous (possibly partial or even empty) code path
12653 @item show debug entry-values
12654 @kindex show debug entry-values
12655 Show the current state of analysis messages printing for both frame argument
12656 values at function entry and tail calls.
12659 The analysis messages for tail calls can for example show why the virtual tail
12660 call frame for function @code{c} has not been recognized (due to the indirect
12661 reference by variable @code{x}):
12664 static void __attribute__((noinline, noclone)) c (void);
12665 void (*x) (void) = c;
12666 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12667 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12668 int main (void) @{ x (); return 0; @}
12670 Breakpoint 1, DW_OP_entry_value resolving cannot find
12671 DW_TAG_call_site 0x40039a in main
12673 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12676 #1 0x000000000040039a in main () at t.c:5
12679 Another possibility is an ambiguous virtual tail call frames resolution:
12683 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12684 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12685 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12686 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12687 static void __attribute__((noinline, noclone)) b (void)
12688 @{ if (i) c (); else e (); @}
12689 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12690 int main (void) @{ a (); return 0; @}
12692 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12693 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12694 tailcall: reduced: 0x4004d2(a) |
12697 #1 0x00000000004004d2 in a () at t.c:8
12698 #2 0x0000000000400395 in main () at t.c:9
12701 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12702 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12704 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12705 @ifset HAVE_MAKEINFO_CLICK
12706 @set ARROW @click{}
12707 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12708 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12710 @ifclear HAVE_MAKEINFO_CLICK
12712 @set CALLSEQ1B @value{CALLSEQ1A}
12713 @set CALLSEQ2B @value{CALLSEQ2A}
12716 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12717 The code can have possible execution paths @value{CALLSEQ1B} or
12718 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12720 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12721 has found. It then finds another possible calling sequcen - that one is
12722 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12723 printed as the @code{reduced:} calling sequence. That one could have many
12724 futher @code{compare:} and @code{reduced:} statements as long as there remain
12725 any non-ambiguous sequence entries.
12727 For the frame of function @code{b} in both cases there are different possible
12728 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12729 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12730 therefore this one is displayed to the user while the ambiguous frames are
12733 There can be also reasons why printing of frame argument values at function
12738 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12739 static void __attribute__((noinline, noclone)) a (int i);
12740 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12741 static void __attribute__((noinline, noclone)) a (int i)
12742 @{ if (i) b (i - 1); else c (0); @}
12743 int main (void) @{ a (5); return 0; @}
12746 #0 c (i=i@@entry=0) at t.c:2
12747 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12748 function "a" at 0x400420 can call itself via tail calls
12749 i=<optimized out>) at t.c:6
12750 #2 0x000000000040036e in main () at t.c:7
12753 @value{GDBN} cannot find out from the inferior state if and how many times did
12754 function @code{a} call itself (via function @code{b}) as these calls would be
12755 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12756 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12757 prints @code{<optimized out>} instead.
12760 @chapter C Preprocessor Macros
12762 Some languages, such as C and C@t{++}, provide a way to define and invoke
12763 ``preprocessor macros'' which expand into strings of tokens.
12764 @value{GDBN} can evaluate expressions containing macro invocations, show
12765 the result of macro expansion, and show a macro's definition, including
12766 where it was defined.
12768 You may need to compile your program specially to provide @value{GDBN}
12769 with information about preprocessor macros. Most compilers do not
12770 include macros in their debugging information, even when you compile
12771 with the @option{-g} flag. @xref{Compilation}.
12773 A program may define a macro at one point, remove that definition later,
12774 and then provide a different definition after that. Thus, at different
12775 points in the program, a macro may have different definitions, or have
12776 no definition at all. If there is a current stack frame, @value{GDBN}
12777 uses the macros in scope at that frame's source code line. Otherwise,
12778 @value{GDBN} uses the macros in scope at the current listing location;
12781 Whenever @value{GDBN} evaluates an expression, it always expands any
12782 macro invocations present in the expression. @value{GDBN} also provides
12783 the following commands for working with macros explicitly.
12787 @kindex macro expand
12788 @cindex macro expansion, showing the results of preprocessor
12789 @cindex preprocessor macro expansion, showing the results of
12790 @cindex expanding preprocessor macros
12791 @item macro expand @var{expression}
12792 @itemx macro exp @var{expression}
12793 Show the results of expanding all preprocessor macro invocations in
12794 @var{expression}. Since @value{GDBN} simply expands macros, but does
12795 not parse the result, @var{expression} need not be a valid expression;
12796 it can be any string of tokens.
12799 @item macro expand-once @var{expression}
12800 @itemx macro exp1 @var{expression}
12801 @cindex expand macro once
12802 @i{(This command is not yet implemented.)} Show the results of
12803 expanding those preprocessor macro invocations that appear explicitly in
12804 @var{expression}. Macro invocations appearing in that expansion are
12805 left unchanged. This command allows you to see the effect of a
12806 particular macro more clearly, without being confused by further
12807 expansions. Since @value{GDBN} simply expands macros, but does not
12808 parse the result, @var{expression} need not be a valid expression; it
12809 can be any string of tokens.
12812 @cindex macro definition, showing
12813 @cindex definition of a macro, showing
12814 @cindex macros, from debug info
12815 @item info macro [-a|-all] [--] @var{macro}
12816 Show the current definition or all definitions of the named @var{macro},
12817 and describe the source location or compiler command-line where that
12818 definition was established. The optional double dash is to signify the end of
12819 argument processing and the beginning of @var{macro} for non C-like macros where
12820 the macro may begin with a hyphen.
12822 @kindex info macros
12823 @item info macros @var{location}
12824 Show all macro definitions that are in effect at the location specified
12825 by @var{location}, and describe the source location or compiler
12826 command-line where those definitions were established.
12828 @kindex macro define
12829 @cindex user-defined macros
12830 @cindex defining macros interactively
12831 @cindex macros, user-defined
12832 @item macro define @var{macro} @var{replacement-list}
12833 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12834 Introduce a definition for a preprocessor macro named @var{macro},
12835 invocations of which are replaced by the tokens given in
12836 @var{replacement-list}. The first form of this command defines an
12837 ``object-like'' macro, which takes no arguments; the second form
12838 defines a ``function-like'' macro, which takes the arguments given in
12841 A definition introduced by this command is in scope in every
12842 expression evaluated in @value{GDBN}, until it is removed with the
12843 @code{macro undef} command, described below. The definition overrides
12844 all definitions for @var{macro} present in the program being debugged,
12845 as well as any previous user-supplied definition.
12847 @kindex macro undef
12848 @item macro undef @var{macro}
12849 Remove any user-supplied definition for the macro named @var{macro}.
12850 This command only affects definitions provided with the @code{macro
12851 define} command, described above; it cannot remove definitions present
12852 in the program being debugged.
12856 List all the macros defined using the @code{macro define} command.
12859 @cindex macros, example of debugging with
12860 Here is a transcript showing the above commands in action. First, we
12861 show our source files:
12866 #include "sample.h"
12869 #define ADD(x) (M + x)
12874 printf ("Hello, world!\n");
12876 printf ("We're so creative.\n");
12878 printf ("Goodbye, world!\n");
12885 Now, we compile the program using the @sc{gnu} C compiler,
12886 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12887 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12888 and @option{-gdwarf-4}; we recommend always choosing the most recent
12889 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12890 includes information about preprocessor macros in the debugging
12894 $ gcc -gdwarf-2 -g3 sample.c -o sample
12898 Now, we start @value{GDBN} on our sample program:
12902 GNU gdb 2002-05-06-cvs
12903 Copyright 2002 Free Software Foundation, Inc.
12904 GDB is free software, @dots{}
12908 We can expand macros and examine their definitions, even when the
12909 program is not running. @value{GDBN} uses the current listing position
12910 to decide which macro definitions are in scope:
12913 (@value{GDBP}) list main
12916 5 #define ADD(x) (M + x)
12921 10 printf ("Hello, world!\n");
12923 12 printf ("We're so creative.\n");
12924 (@value{GDBP}) info macro ADD
12925 Defined at /home/jimb/gdb/macros/play/sample.c:5
12926 #define ADD(x) (M + x)
12927 (@value{GDBP}) info macro Q
12928 Defined at /home/jimb/gdb/macros/play/sample.h:1
12929 included at /home/jimb/gdb/macros/play/sample.c:2
12931 (@value{GDBP}) macro expand ADD(1)
12932 expands to: (42 + 1)
12933 (@value{GDBP}) macro expand-once ADD(1)
12934 expands to: once (M + 1)
12938 In the example above, note that @code{macro expand-once} expands only
12939 the macro invocation explicit in the original text --- the invocation of
12940 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12941 which was introduced by @code{ADD}.
12943 Once the program is running, @value{GDBN} uses the macro definitions in
12944 force at the source line of the current stack frame:
12947 (@value{GDBP}) break main
12948 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12950 Starting program: /home/jimb/gdb/macros/play/sample
12952 Breakpoint 1, main () at sample.c:10
12953 10 printf ("Hello, world!\n");
12957 At line 10, the definition of the macro @code{N} at line 9 is in force:
12960 (@value{GDBP}) info macro N
12961 Defined at /home/jimb/gdb/macros/play/sample.c:9
12963 (@value{GDBP}) macro expand N Q M
12964 expands to: 28 < 42
12965 (@value{GDBP}) print N Q M
12970 As we step over directives that remove @code{N}'s definition, and then
12971 give it a new definition, @value{GDBN} finds the definition (or lack
12972 thereof) in force at each point:
12975 (@value{GDBP}) next
12977 12 printf ("We're so creative.\n");
12978 (@value{GDBP}) info macro N
12979 The symbol `N' has no definition as a C/C++ preprocessor macro
12980 at /home/jimb/gdb/macros/play/sample.c:12
12981 (@value{GDBP}) next
12983 14 printf ("Goodbye, world!\n");
12984 (@value{GDBP}) info macro N
12985 Defined at /home/jimb/gdb/macros/play/sample.c:13
12987 (@value{GDBP}) macro expand N Q M
12988 expands to: 1729 < 42
12989 (@value{GDBP}) print N Q M
12994 In addition to source files, macros can be defined on the compilation command
12995 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12996 such a way, @value{GDBN} displays the location of their definition as line zero
12997 of the source file submitted to the compiler.
13000 (@value{GDBP}) info macro __STDC__
13001 Defined at /home/jimb/gdb/macros/play/sample.c:0
13008 @chapter Tracepoints
13009 @c This chapter is based on the documentation written by Michael
13010 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13012 @cindex tracepoints
13013 In some applications, it is not feasible for the debugger to interrupt
13014 the program's execution long enough for the developer to learn
13015 anything helpful about its behavior. If the program's correctness
13016 depends on its real-time behavior, delays introduced by a debugger
13017 might cause the program to change its behavior drastically, or perhaps
13018 fail, even when the code itself is correct. It is useful to be able
13019 to observe the program's behavior without interrupting it.
13021 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13022 specify locations in the program, called @dfn{tracepoints}, and
13023 arbitrary expressions to evaluate when those tracepoints are reached.
13024 Later, using the @code{tfind} command, you can examine the values
13025 those expressions had when the program hit the tracepoints. The
13026 expressions may also denote objects in memory---structures or arrays,
13027 for example---whose values @value{GDBN} should record; while visiting
13028 a particular tracepoint, you may inspect those objects as if they were
13029 in memory at that moment. However, because @value{GDBN} records these
13030 values without interacting with you, it can do so quickly and
13031 unobtrusively, hopefully not disturbing the program's behavior.
13033 The tracepoint facility is currently available only for remote
13034 targets. @xref{Targets}. In addition, your remote target must know
13035 how to collect trace data. This functionality is implemented in the
13036 remote stub; however, none of the stubs distributed with @value{GDBN}
13037 support tracepoints as of this writing. The format of the remote
13038 packets used to implement tracepoints are described in @ref{Tracepoint
13041 It is also possible to get trace data from a file, in a manner reminiscent
13042 of corefiles; you specify the filename, and use @code{tfind} to search
13043 through the file. @xref{Trace Files}, for more details.
13045 This chapter describes the tracepoint commands and features.
13048 * Set Tracepoints::
13049 * Analyze Collected Data::
13050 * Tracepoint Variables::
13054 @node Set Tracepoints
13055 @section Commands to Set Tracepoints
13057 Before running such a @dfn{trace experiment}, an arbitrary number of
13058 tracepoints can be set. A tracepoint is actually a special type of
13059 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13060 standard breakpoint commands. For instance, as with breakpoints,
13061 tracepoint numbers are successive integers starting from one, and many
13062 of the commands associated with tracepoints take the tracepoint number
13063 as their argument, to identify which tracepoint to work on.
13065 For each tracepoint, you can specify, in advance, some arbitrary set
13066 of data that you want the target to collect in the trace buffer when
13067 it hits that tracepoint. The collected data can include registers,
13068 local variables, or global data. Later, you can use @value{GDBN}
13069 commands to examine the values these data had at the time the
13070 tracepoint was hit.
13072 Tracepoints do not support every breakpoint feature. Ignore counts on
13073 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13074 commands when they are hit. Tracepoints may not be thread-specific
13077 @cindex fast tracepoints
13078 Some targets may support @dfn{fast tracepoints}, which are inserted in
13079 a different way (such as with a jump instead of a trap), that is
13080 faster but possibly restricted in where they may be installed.
13082 @cindex static tracepoints
13083 @cindex markers, static tracepoints
13084 @cindex probing markers, static tracepoints
13085 Regular and fast tracepoints are dynamic tracing facilities, meaning
13086 that they can be used to insert tracepoints at (almost) any location
13087 in the target. Some targets may also support controlling @dfn{static
13088 tracepoints} from @value{GDBN}. With static tracing, a set of
13089 instrumentation points, also known as @dfn{markers}, are embedded in
13090 the target program, and can be activated or deactivated by name or
13091 address. These are usually placed at locations which facilitate
13092 investigating what the target is actually doing. @value{GDBN}'s
13093 support for static tracing includes being able to list instrumentation
13094 points, and attach them with @value{GDBN} defined high level
13095 tracepoints that expose the whole range of convenience of
13096 @value{GDBN}'s tracepoints support. Namely, support for collecting
13097 registers values and values of global or local (to the instrumentation
13098 point) variables; tracepoint conditions and trace state variables.
13099 The act of installing a @value{GDBN} static tracepoint on an
13100 instrumentation point, or marker, is referred to as @dfn{probing} a
13101 static tracepoint marker.
13103 @code{gdbserver} supports tracepoints on some target systems.
13104 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13106 This section describes commands to set tracepoints and associated
13107 conditions and actions.
13110 * Create and Delete Tracepoints::
13111 * Enable and Disable Tracepoints::
13112 * Tracepoint Passcounts::
13113 * Tracepoint Conditions::
13114 * Trace State Variables::
13115 * Tracepoint Actions::
13116 * Listing Tracepoints::
13117 * Listing Static Tracepoint Markers::
13118 * Starting and Stopping Trace Experiments::
13119 * Tracepoint Restrictions::
13122 @node Create and Delete Tracepoints
13123 @subsection Create and Delete Tracepoints
13126 @cindex set tracepoint
13128 @item trace @var{location}
13129 The @code{trace} command is very similar to the @code{break} command.
13130 Its argument @var{location} can be any valid location.
13131 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13132 which is a point in the target program where the debugger will briefly stop,
13133 collect some data, and then allow the program to continue. Setting a tracepoint
13134 or changing its actions takes effect immediately if the remote stub
13135 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13137 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13138 these changes don't take effect until the next @code{tstart}
13139 command, and once a trace experiment is running, further changes will
13140 not have any effect until the next trace experiment starts. In addition,
13141 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13142 address is not yet resolved. (This is similar to pending breakpoints.)
13143 Pending tracepoints are not downloaded to the target and not installed
13144 until they are resolved. The resolution of pending tracepoints requires
13145 @value{GDBN} support---when debugging with the remote target, and
13146 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13147 tracing}), pending tracepoints can not be resolved (and downloaded to
13148 the remote stub) while @value{GDBN} is disconnected.
13150 Here are some examples of using the @code{trace} command:
13153 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13155 (@value{GDBP}) @b{trace +2} // 2 lines forward
13157 (@value{GDBP}) @b{trace my_function} // first source line of function
13159 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13161 (@value{GDBP}) @b{trace *0x2117c4} // an address
13165 You can abbreviate @code{trace} as @code{tr}.
13167 @item trace @var{location} if @var{cond}
13168 Set a tracepoint with condition @var{cond}; evaluate the expression
13169 @var{cond} each time the tracepoint is reached, and collect data only
13170 if the value is nonzero---that is, if @var{cond} evaluates as true.
13171 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13172 information on tracepoint conditions.
13174 @item ftrace @var{location} [ if @var{cond} ]
13175 @cindex set fast tracepoint
13176 @cindex fast tracepoints, setting
13178 The @code{ftrace} command sets a fast tracepoint. For targets that
13179 support them, fast tracepoints will use a more efficient but possibly
13180 less general technique to trigger data collection, such as a jump
13181 instruction instead of a trap, or some sort of hardware support. It
13182 may not be possible to create a fast tracepoint at the desired
13183 location, in which case the command will exit with an explanatory
13186 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13189 On 32-bit x86-architecture systems, fast tracepoints normally need to
13190 be placed at an instruction that is 5 bytes or longer, but can be
13191 placed at 4-byte instructions if the low 64K of memory of the target
13192 program is available to install trampolines. Some Unix-type systems,
13193 such as @sc{gnu}/Linux, exclude low addresses from the program's
13194 address space; but for instance with the Linux kernel it is possible
13195 to let @value{GDBN} use this area by doing a @command{sysctl} command
13196 to set the @code{mmap_min_addr} kernel parameter, as in
13199 sudo sysctl -w vm.mmap_min_addr=32768
13203 which sets the low address to 32K, which leaves plenty of room for
13204 trampolines. The minimum address should be set to a page boundary.
13206 @item strace @var{location} [ if @var{cond} ]
13207 @cindex set static tracepoint
13208 @cindex static tracepoints, setting
13209 @cindex probe static tracepoint marker
13211 The @code{strace} command sets a static tracepoint. For targets that
13212 support it, setting a static tracepoint probes a static
13213 instrumentation point, or marker, found at @var{location}. It may not
13214 be possible to set a static tracepoint at the desired location, in
13215 which case the command will exit with an explanatory message.
13217 @value{GDBN} handles arguments to @code{strace} exactly as for
13218 @code{trace}, with the addition that the user can also specify
13219 @code{-m @var{marker}} as @var{location}. This probes the marker
13220 identified by the @var{marker} string identifier. This identifier
13221 depends on the static tracepoint backend library your program is
13222 using. You can find all the marker identifiers in the @samp{ID} field
13223 of the @code{info static-tracepoint-markers} command output.
13224 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13225 Markers}. For example, in the following small program using the UST
13231 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13236 the marker id is composed of joining the first two arguments to the
13237 @code{trace_mark} call with a slash, which translates to:
13240 (@value{GDBP}) info static-tracepoint-markers
13241 Cnt Enb ID Address What
13242 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13248 so you may probe the marker above with:
13251 (@value{GDBP}) strace -m ust/bar33
13254 Static tracepoints accept an extra collect action --- @code{collect
13255 $_sdata}. This collects arbitrary user data passed in the probe point
13256 call to the tracing library. In the UST example above, you'll see
13257 that the third argument to @code{trace_mark} is a printf-like format
13258 string. The user data is then the result of running that formating
13259 string against the following arguments. Note that @code{info
13260 static-tracepoint-markers} command output lists that format string in
13261 the @samp{Data:} field.
13263 You can inspect this data when analyzing the trace buffer, by printing
13264 the $_sdata variable like any other variable available to
13265 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13268 @cindex last tracepoint number
13269 @cindex recent tracepoint number
13270 @cindex tracepoint number
13271 The convenience variable @code{$tpnum} records the tracepoint number
13272 of the most recently set tracepoint.
13274 @kindex delete tracepoint
13275 @cindex tracepoint deletion
13276 @item delete tracepoint @r{[}@var{num}@r{]}
13277 Permanently delete one or more tracepoints. With no argument, the
13278 default is to delete all tracepoints. Note that the regular
13279 @code{delete} command can remove tracepoints also.
13284 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13286 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13290 You can abbreviate this command as @code{del tr}.
13293 @node Enable and Disable Tracepoints
13294 @subsection Enable and Disable Tracepoints
13296 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13299 @kindex disable tracepoint
13300 @item disable tracepoint @r{[}@var{num}@r{]}
13301 Disable tracepoint @var{num}, or all tracepoints if no argument
13302 @var{num} is given. A disabled tracepoint will have no effect during
13303 a trace experiment, but it is not forgotten. You can re-enable
13304 a disabled tracepoint using the @code{enable tracepoint} command.
13305 If the command is issued during a trace experiment and the debug target
13306 has support for disabling tracepoints during a trace experiment, then the
13307 change will be effective immediately. Otherwise, it will be applied to the
13308 next trace experiment.
13310 @kindex enable tracepoint
13311 @item enable tracepoint @r{[}@var{num}@r{]}
13312 Enable tracepoint @var{num}, or all tracepoints. If this command is
13313 issued during a trace experiment and the debug target supports enabling
13314 tracepoints during a trace experiment, then the enabled tracepoints will
13315 become effective immediately. Otherwise, they will become effective the
13316 next time a trace experiment is run.
13319 @node Tracepoint Passcounts
13320 @subsection Tracepoint Passcounts
13324 @cindex tracepoint pass count
13325 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13326 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13327 automatically stop a trace experiment. If a tracepoint's passcount is
13328 @var{n}, then the trace experiment will be automatically stopped on
13329 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13330 @var{num} is not specified, the @code{passcount} command sets the
13331 passcount of the most recently defined tracepoint. If no passcount is
13332 given, the trace experiment will run until stopped explicitly by the
13338 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13339 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13341 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13342 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13343 (@value{GDBP}) @b{trace foo}
13344 (@value{GDBP}) @b{pass 3}
13345 (@value{GDBP}) @b{trace bar}
13346 (@value{GDBP}) @b{pass 2}
13347 (@value{GDBP}) @b{trace baz}
13348 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13349 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13350 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13351 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13355 @node Tracepoint Conditions
13356 @subsection Tracepoint Conditions
13357 @cindex conditional tracepoints
13358 @cindex tracepoint conditions
13360 The simplest sort of tracepoint collects data every time your program
13361 reaches a specified place. You can also specify a @dfn{condition} for
13362 a tracepoint. A condition is just a Boolean expression in your
13363 programming language (@pxref{Expressions, ,Expressions}). A
13364 tracepoint with a condition evaluates the expression each time your
13365 program reaches it, and data collection happens only if the condition
13368 Tracepoint conditions can be specified when a tracepoint is set, by
13369 using @samp{if} in the arguments to the @code{trace} command.
13370 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13371 also be set or changed at any time with the @code{condition} command,
13372 just as with breakpoints.
13374 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13375 the conditional expression itself. Instead, @value{GDBN} encodes the
13376 expression into an agent expression (@pxref{Agent Expressions})
13377 suitable for execution on the target, independently of @value{GDBN}.
13378 Global variables become raw memory locations, locals become stack
13379 accesses, and so forth.
13381 For instance, suppose you have a function that is usually called
13382 frequently, but should not be called after an error has occurred. You
13383 could use the following tracepoint command to collect data about calls
13384 of that function that happen while the error code is propagating
13385 through the program; an unconditional tracepoint could end up
13386 collecting thousands of useless trace frames that you would have to
13390 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13393 @node Trace State Variables
13394 @subsection Trace State Variables
13395 @cindex trace state variables
13397 A @dfn{trace state variable} is a special type of variable that is
13398 created and managed by target-side code. The syntax is the same as
13399 that for GDB's convenience variables (a string prefixed with ``$''),
13400 but they are stored on the target. They must be created explicitly,
13401 using a @code{tvariable} command. They are always 64-bit signed
13404 Trace state variables are remembered by @value{GDBN}, and downloaded
13405 to the target along with tracepoint information when the trace
13406 experiment starts. There are no intrinsic limits on the number of
13407 trace state variables, beyond memory limitations of the target.
13409 @cindex convenience variables, and trace state variables
13410 Although trace state variables are managed by the target, you can use
13411 them in print commands and expressions as if they were convenience
13412 variables; @value{GDBN} will get the current value from the target
13413 while the trace experiment is running. Trace state variables share
13414 the same namespace as other ``$'' variables, which means that you
13415 cannot have trace state variables with names like @code{$23} or
13416 @code{$pc}, nor can you have a trace state variable and a convenience
13417 variable with the same name.
13421 @item tvariable $@var{name} [ = @var{expression} ]
13423 The @code{tvariable} command creates a new trace state variable named
13424 @code{$@var{name}}, and optionally gives it an initial value of
13425 @var{expression}. The @var{expression} is evaluated when this command is
13426 entered; the result will be converted to an integer if possible,
13427 otherwise @value{GDBN} will report an error. A subsequent
13428 @code{tvariable} command specifying the same name does not create a
13429 variable, but instead assigns the supplied initial value to the
13430 existing variable of that name, overwriting any previous initial
13431 value. The default initial value is 0.
13433 @item info tvariables
13434 @kindex info tvariables
13435 List all the trace state variables along with their initial values.
13436 Their current values may also be displayed, if the trace experiment is
13439 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13440 @kindex delete tvariable
13441 Delete the given trace state variables, or all of them if no arguments
13446 @node Tracepoint Actions
13447 @subsection Tracepoint Action Lists
13451 @cindex tracepoint actions
13452 @item actions @r{[}@var{num}@r{]}
13453 This command will prompt for a list of actions to be taken when the
13454 tracepoint is hit. If the tracepoint number @var{num} is not
13455 specified, this command sets the actions for the one that was most
13456 recently defined (so that you can define a tracepoint and then say
13457 @code{actions} without bothering about its number). You specify the
13458 actions themselves on the following lines, one action at a time, and
13459 terminate the actions list with a line containing just @code{end}. So
13460 far, the only defined actions are @code{collect}, @code{teval}, and
13461 @code{while-stepping}.
13463 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13464 Commands, ,Breakpoint Command Lists}), except that only the defined
13465 actions are allowed; any other @value{GDBN} command is rejected.
13467 @cindex remove actions from a tracepoint
13468 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13469 and follow it immediately with @samp{end}.
13472 (@value{GDBP}) @b{collect @var{data}} // collect some data
13474 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13476 (@value{GDBP}) @b{end} // signals the end of actions.
13479 In the following example, the action list begins with @code{collect}
13480 commands indicating the things to be collected when the tracepoint is
13481 hit. Then, in order to single-step and collect additional data
13482 following the tracepoint, a @code{while-stepping} command is used,
13483 followed by the list of things to be collected after each step in a
13484 sequence of single steps. The @code{while-stepping} command is
13485 terminated by its own separate @code{end} command. Lastly, the action
13486 list is terminated by an @code{end} command.
13489 (@value{GDBP}) @b{trace foo}
13490 (@value{GDBP}) @b{actions}
13491 Enter actions for tracepoint 1, one per line:
13494 > while-stepping 12
13495 > collect $pc, arr[i]
13500 @kindex collect @r{(tracepoints)}
13501 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13502 Collect values of the given expressions when the tracepoint is hit.
13503 This command accepts a comma-separated list of any valid expressions.
13504 In addition to global, static, or local variables, the following
13505 special arguments are supported:
13509 Collect all registers.
13512 Collect all function arguments.
13515 Collect all local variables.
13518 Collect the return address. This is helpful if you want to see more
13521 @emph{Note:} The return address location can not always be reliably
13522 determined up front, and the wrong address / registers may end up
13523 collected instead. On some architectures the reliability is higher
13524 for tracepoints at function entry, while on others it's the opposite.
13525 When this happens, backtracing will stop because the return address is
13526 found unavailable (unless another collect rule happened to match it).
13529 Collects the number of arguments from the static probe at which the
13530 tracepoint is located.
13531 @xref{Static Probe Points}.
13533 @item $_probe_arg@var{n}
13534 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13535 from the static probe at which the tracepoint is located.
13536 @xref{Static Probe Points}.
13539 @vindex $_sdata@r{, collect}
13540 Collect static tracepoint marker specific data. Only available for
13541 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13542 Lists}. On the UST static tracepoints library backend, an
13543 instrumentation point resembles a @code{printf} function call. The
13544 tracing library is able to collect user specified data formatted to a
13545 character string using the format provided by the programmer that
13546 instrumented the program. Other backends have similar mechanisms.
13547 Here's an example of a UST marker call:
13550 const char master_name[] = "$your_name";
13551 trace_mark(channel1, marker1, "hello %s", master_name)
13554 In this case, collecting @code{$_sdata} collects the string
13555 @samp{hello $yourname}. When analyzing the trace buffer, you can
13556 inspect @samp{$_sdata} like any other variable available to
13560 You can give several consecutive @code{collect} commands, each one
13561 with a single argument, or one @code{collect} command with several
13562 arguments separated by commas; the effect is the same.
13564 The optional @var{mods} changes the usual handling of the arguments.
13565 @code{s} requests that pointers to chars be handled as strings, in
13566 particular collecting the contents of the memory being pointed at, up
13567 to the first zero. The upper bound is by default the value of the
13568 @code{print elements} variable; if @code{s} is followed by a decimal
13569 number, that is the upper bound instead. So for instance
13570 @samp{collect/s25 mystr} collects as many as 25 characters at
13573 The command @code{info scope} (@pxref{Symbols, info scope}) is
13574 particularly useful for figuring out what data to collect.
13576 @kindex teval @r{(tracepoints)}
13577 @item teval @var{expr1}, @var{expr2}, @dots{}
13578 Evaluate the given expressions when the tracepoint is hit. This
13579 command accepts a comma-separated list of expressions. The results
13580 are discarded, so this is mainly useful for assigning values to trace
13581 state variables (@pxref{Trace State Variables}) without adding those
13582 values to the trace buffer, as would be the case if the @code{collect}
13585 @kindex while-stepping @r{(tracepoints)}
13586 @item while-stepping @var{n}
13587 Perform @var{n} single-step instruction traces after the tracepoint,
13588 collecting new data after each step. The @code{while-stepping}
13589 command is followed by the list of what to collect while stepping
13590 (followed by its own @code{end} command):
13593 > while-stepping 12
13594 > collect $regs, myglobal
13600 Note that @code{$pc} is not automatically collected by
13601 @code{while-stepping}; you need to explicitly collect that register if
13602 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13605 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13606 @kindex set default-collect
13607 @cindex default collection action
13608 This variable is a list of expressions to collect at each tracepoint
13609 hit. It is effectively an additional @code{collect} action prepended
13610 to every tracepoint action list. The expressions are parsed
13611 individually for each tracepoint, so for instance a variable named
13612 @code{xyz} may be interpreted as a global for one tracepoint, and a
13613 local for another, as appropriate to the tracepoint's location.
13615 @item show default-collect
13616 @kindex show default-collect
13617 Show the list of expressions that are collected by default at each
13622 @node Listing Tracepoints
13623 @subsection Listing Tracepoints
13626 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13627 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13628 @cindex information about tracepoints
13629 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13630 Display information about the tracepoint @var{num}. If you don't
13631 specify a tracepoint number, displays information about all the
13632 tracepoints defined so far. The format is similar to that used for
13633 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13634 command, simply restricting itself to tracepoints.
13636 A tracepoint's listing may include additional information specific to
13641 its passcount as given by the @code{passcount @var{n}} command
13644 the state about installed on target of each location
13648 (@value{GDBP}) @b{info trace}
13649 Num Type Disp Enb Address What
13650 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13652 collect globfoo, $regs
13657 2 tracepoint keep y <MULTIPLE>
13659 2.1 y 0x0804859c in func4 at change-loc.h:35
13660 installed on target
13661 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13662 installed on target
13663 2.3 y <PENDING> set_tracepoint
13664 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13665 not installed on target
13670 This command can be abbreviated @code{info tp}.
13673 @node Listing Static Tracepoint Markers
13674 @subsection Listing Static Tracepoint Markers
13677 @kindex info static-tracepoint-markers
13678 @cindex information about static tracepoint markers
13679 @item info static-tracepoint-markers
13680 Display information about all static tracepoint markers defined in the
13683 For each marker, the following columns are printed:
13687 An incrementing counter, output to help readability. This is not a
13690 The marker ID, as reported by the target.
13691 @item Enabled or Disabled
13692 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13693 that are not enabled.
13695 Where the marker is in your program, as a memory address.
13697 Where the marker is in the source for your program, as a file and line
13698 number. If the debug information included in the program does not
13699 allow @value{GDBN} to locate the source of the marker, this column
13700 will be left blank.
13704 In addition, the following information may be printed for each marker:
13708 User data passed to the tracing library by the marker call. In the
13709 UST backend, this is the format string passed as argument to the
13711 @item Static tracepoints probing the marker
13712 The list of static tracepoints attached to the marker.
13716 (@value{GDBP}) info static-tracepoint-markers
13717 Cnt ID Enb Address What
13718 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13719 Data: number1 %d number2 %d
13720 Probed by static tracepoints: #2
13721 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13727 @node Starting and Stopping Trace Experiments
13728 @subsection Starting and Stopping Trace Experiments
13731 @kindex tstart [ @var{notes} ]
13732 @cindex start a new trace experiment
13733 @cindex collected data discarded
13735 This command starts the trace experiment, and begins collecting data.
13736 It has the side effect of discarding all the data collected in the
13737 trace buffer during the previous trace experiment. If any arguments
13738 are supplied, they are taken as a note and stored with the trace
13739 experiment's state. The notes may be arbitrary text, and are
13740 especially useful with disconnected tracing in a multi-user context;
13741 the notes can explain what the trace is doing, supply user contact
13742 information, and so forth.
13744 @kindex tstop [ @var{notes} ]
13745 @cindex stop a running trace experiment
13747 This command stops the trace experiment. If any arguments are
13748 supplied, they are recorded with the experiment as a note. This is
13749 useful if you are stopping a trace started by someone else, for
13750 instance if the trace is interfering with the system's behavior and
13751 needs to be stopped quickly.
13753 @strong{Note}: a trace experiment and data collection may stop
13754 automatically if any tracepoint's passcount is reached
13755 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13758 @cindex status of trace data collection
13759 @cindex trace experiment, status of
13761 This command displays the status of the current trace data
13765 Here is an example of the commands we described so far:
13768 (@value{GDBP}) @b{trace gdb_c_test}
13769 (@value{GDBP}) @b{actions}
13770 Enter actions for tracepoint #1, one per line.
13771 > collect $regs,$locals,$args
13772 > while-stepping 11
13776 (@value{GDBP}) @b{tstart}
13777 [time passes @dots{}]
13778 (@value{GDBP}) @b{tstop}
13781 @anchor{disconnected tracing}
13782 @cindex disconnected tracing
13783 You can choose to continue running the trace experiment even if
13784 @value{GDBN} disconnects from the target, voluntarily or
13785 involuntarily. For commands such as @code{detach}, the debugger will
13786 ask what you want to do with the trace. But for unexpected
13787 terminations (@value{GDBN} crash, network outage), it would be
13788 unfortunate to lose hard-won trace data, so the variable
13789 @code{disconnected-tracing} lets you decide whether the trace should
13790 continue running without @value{GDBN}.
13793 @item set disconnected-tracing on
13794 @itemx set disconnected-tracing off
13795 @kindex set disconnected-tracing
13796 Choose whether a tracing run should continue to run if @value{GDBN}
13797 has disconnected from the target. Note that @code{detach} or
13798 @code{quit} will ask you directly what to do about a running trace no
13799 matter what this variable's setting, so the variable is mainly useful
13800 for handling unexpected situations, such as loss of the network.
13802 @item show disconnected-tracing
13803 @kindex show disconnected-tracing
13804 Show the current choice for disconnected tracing.
13808 When you reconnect to the target, the trace experiment may or may not
13809 still be running; it might have filled the trace buffer in the
13810 meantime, or stopped for one of the other reasons. If it is running,
13811 it will continue after reconnection.
13813 Upon reconnection, the target will upload information about the
13814 tracepoints in effect. @value{GDBN} will then compare that
13815 information to the set of tracepoints currently defined, and attempt
13816 to match them up, allowing for the possibility that the numbers may
13817 have changed due to creation and deletion in the meantime. If one of
13818 the target's tracepoints does not match any in @value{GDBN}, the
13819 debugger will create a new tracepoint, so that you have a number with
13820 which to specify that tracepoint. This matching-up process is
13821 necessarily heuristic, and it may result in useless tracepoints being
13822 created; you may simply delete them if they are of no use.
13824 @cindex circular trace buffer
13825 If your target agent supports a @dfn{circular trace buffer}, then you
13826 can run a trace experiment indefinitely without filling the trace
13827 buffer; when space runs out, the agent deletes already-collected trace
13828 frames, oldest first, until there is enough room to continue
13829 collecting. This is especially useful if your tracepoints are being
13830 hit too often, and your trace gets terminated prematurely because the
13831 buffer is full. To ask for a circular trace buffer, simply set
13832 @samp{circular-trace-buffer} to on. You can set this at any time,
13833 including during tracing; if the agent can do it, it will change
13834 buffer handling on the fly, otherwise it will not take effect until
13838 @item set circular-trace-buffer on
13839 @itemx set circular-trace-buffer off
13840 @kindex set circular-trace-buffer
13841 Choose whether a tracing run should use a linear or circular buffer
13842 for trace data. A linear buffer will not lose any trace data, but may
13843 fill up prematurely, while a circular buffer will discard old trace
13844 data, but it will have always room for the latest tracepoint hits.
13846 @item show circular-trace-buffer
13847 @kindex show circular-trace-buffer
13848 Show the current choice for the trace buffer. Note that this may not
13849 match the agent's current buffer handling, nor is it guaranteed to
13850 match the setting that might have been in effect during a past run,
13851 for instance if you are looking at frames from a trace file.
13856 @item set trace-buffer-size @var{n}
13857 @itemx set trace-buffer-size unlimited
13858 @kindex set trace-buffer-size
13859 Request that the target use a trace buffer of @var{n} bytes. Not all
13860 targets will honor the request; they may have a compiled-in size for
13861 the trace buffer, or some other limitation. Set to a value of
13862 @code{unlimited} or @code{-1} to let the target use whatever size it
13863 likes. This is also the default.
13865 @item show trace-buffer-size
13866 @kindex show trace-buffer-size
13867 Show the current requested size for the trace buffer. Note that this
13868 will only match the actual size if the target supports size-setting,
13869 and was able to handle the requested size. For instance, if the
13870 target can only change buffer size between runs, this variable will
13871 not reflect the change until the next run starts. Use @code{tstatus}
13872 to get a report of the actual buffer size.
13876 @item set trace-user @var{text}
13877 @kindex set trace-user
13879 @item show trace-user
13880 @kindex show trace-user
13882 @item set trace-notes @var{text}
13883 @kindex set trace-notes
13884 Set the trace run's notes.
13886 @item show trace-notes
13887 @kindex show trace-notes
13888 Show the trace run's notes.
13890 @item set trace-stop-notes @var{text}
13891 @kindex set trace-stop-notes
13892 Set the trace run's stop notes. The handling of the note is as for
13893 @code{tstop} arguments; the set command is convenient way to fix a
13894 stop note that is mistaken or incomplete.
13896 @item show trace-stop-notes
13897 @kindex show trace-stop-notes
13898 Show the trace run's stop notes.
13902 @node Tracepoint Restrictions
13903 @subsection Tracepoint Restrictions
13905 @cindex tracepoint restrictions
13906 There are a number of restrictions on the use of tracepoints. As
13907 described above, tracepoint data gathering occurs on the target
13908 without interaction from @value{GDBN}. Thus the full capabilities of
13909 the debugger are not available during data gathering, and then at data
13910 examination time, you will be limited by only having what was
13911 collected. The following items describe some common problems, but it
13912 is not exhaustive, and you may run into additional difficulties not
13918 Tracepoint expressions are intended to gather objects (lvalues). Thus
13919 the full flexibility of GDB's expression evaluator is not available.
13920 You cannot call functions, cast objects to aggregate types, access
13921 convenience variables or modify values (except by assignment to trace
13922 state variables). Some language features may implicitly call
13923 functions (for instance Objective-C fields with accessors), and therefore
13924 cannot be collected either.
13927 Collection of local variables, either individually or in bulk with
13928 @code{$locals} or @code{$args}, during @code{while-stepping} may
13929 behave erratically. The stepping action may enter a new scope (for
13930 instance by stepping into a function), or the location of the variable
13931 may change (for instance it is loaded into a register). The
13932 tracepoint data recorded uses the location information for the
13933 variables that is correct for the tracepoint location. When the
13934 tracepoint is created, it is not possible, in general, to determine
13935 where the steps of a @code{while-stepping} sequence will advance the
13936 program---particularly if a conditional branch is stepped.
13939 Collection of an incompletely-initialized or partially-destroyed object
13940 may result in something that @value{GDBN} cannot display, or displays
13941 in a misleading way.
13944 When @value{GDBN} displays a pointer to character it automatically
13945 dereferences the pointer to also display characters of the string
13946 being pointed to. However, collecting the pointer during tracing does
13947 not automatically collect the string. You need to explicitly
13948 dereference the pointer and provide size information if you want to
13949 collect not only the pointer, but the memory pointed to. For example,
13950 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13954 It is not possible to collect a complete stack backtrace at a
13955 tracepoint. Instead, you may collect the registers and a few hundred
13956 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13957 (adjust to use the name of the actual stack pointer register on your
13958 target architecture, and the amount of stack you wish to capture).
13959 Then the @code{backtrace} command will show a partial backtrace when
13960 using a trace frame. The number of stack frames that can be examined
13961 depends on the sizes of the frames in the collected stack. Note that
13962 if you ask for a block so large that it goes past the bottom of the
13963 stack, the target agent may report an error trying to read from an
13967 If you do not collect registers at a tracepoint, @value{GDBN} can
13968 infer that the value of @code{$pc} must be the same as the address of
13969 the tracepoint and use that when you are looking at a trace frame
13970 for that tracepoint. However, this cannot work if the tracepoint has
13971 multiple locations (for instance if it was set in a function that was
13972 inlined), or if it has a @code{while-stepping} loop. In those cases
13973 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13978 @node Analyze Collected Data
13979 @section Using the Collected Data
13981 After the tracepoint experiment ends, you use @value{GDBN} commands
13982 for examining the trace data. The basic idea is that each tracepoint
13983 collects a trace @dfn{snapshot} every time it is hit and another
13984 snapshot every time it single-steps. All these snapshots are
13985 consecutively numbered from zero and go into a buffer, and you can
13986 examine them later. The way you examine them is to @dfn{focus} on a
13987 specific trace snapshot. When the remote stub is focused on a trace
13988 snapshot, it will respond to all @value{GDBN} requests for memory and
13989 registers by reading from the buffer which belongs to that snapshot,
13990 rather than from @emph{real} memory or registers of the program being
13991 debugged. This means that @strong{all} @value{GDBN} commands
13992 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13993 behave as if we were currently debugging the program state as it was
13994 when the tracepoint occurred. Any requests for data that are not in
13995 the buffer will fail.
13998 * tfind:: How to select a trace snapshot
13999 * tdump:: How to display all data for a snapshot
14000 * save tracepoints:: How to save tracepoints for a future run
14004 @subsection @code{tfind @var{n}}
14007 @cindex select trace snapshot
14008 @cindex find trace snapshot
14009 The basic command for selecting a trace snapshot from the buffer is
14010 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14011 counting from zero. If no argument @var{n} is given, the next
14012 snapshot is selected.
14014 Here are the various forms of using the @code{tfind} command.
14018 Find the first snapshot in the buffer. This is a synonym for
14019 @code{tfind 0} (since 0 is the number of the first snapshot).
14022 Stop debugging trace snapshots, resume @emph{live} debugging.
14025 Same as @samp{tfind none}.
14028 No argument means find the next trace snapshot or find the first
14029 one if no trace snapshot is selected.
14032 Find the previous trace snapshot before the current one. This permits
14033 retracing earlier steps.
14035 @item tfind tracepoint @var{num}
14036 Find the next snapshot associated with tracepoint @var{num}. Search
14037 proceeds forward from the last examined trace snapshot. If no
14038 argument @var{num} is given, it means find the next snapshot collected
14039 for the same tracepoint as the current snapshot.
14041 @item tfind pc @var{addr}
14042 Find the next snapshot associated with the value @var{addr} of the
14043 program counter. Search proceeds forward from the last examined trace
14044 snapshot. If no argument @var{addr} is given, it means find the next
14045 snapshot with the same value of PC as the current snapshot.
14047 @item tfind outside @var{addr1}, @var{addr2}
14048 Find the next snapshot whose PC is outside the given range of
14049 addresses (exclusive).
14051 @item tfind range @var{addr1}, @var{addr2}
14052 Find the next snapshot whose PC is between @var{addr1} and
14053 @var{addr2} (inclusive).
14055 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14056 Find the next snapshot associated with the source line @var{n}. If
14057 the optional argument @var{file} is given, refer to line @var{n} in
14058 that source file. Search proceeds forward from the last examined
14059 trace snapshot. If no argument @var{n} is given, it means find the
14060 next line other than the one currently being examined; thus saying
14061 @code{tfind line} repeatedly can appear to have the same effect as
14062 stepping from line to line in a @emph{live} debugging session.
14065 The default arguments for the @code{tfind} commands are specifically
14066 designed to make it easy to scan through the trace buffer. For
14067 instance, @code{tfind} with no argument selects the next trace
14068 snapshot, and @code{tfind -} with no argument selects the previous
14069 trace snapshot. So, by giving one @code{tfind} command, and then
14070 simply hitting @key{RET} repeatedly you can examine all the trace
14071 snapshots in order. Or, by saying @code{tfind -} and then hitting
14072 @key{RET} repeatedly you can examine the snapshots in reverse order.
14073 The @code{tfind line} command with no argument selects the snapshot
14074 for the next source line executed. The @code{tfind pc} command with
14075 no argument selects the next snapshot with the same program counter
14076 (PC) as the current frame. The @code{tfind tracepoint} command with
14077 no argument selects the next trace snapshot collected by the same
14078 tracepoint as the current one.
14080 In addition to letting you scan through the trace buffer manually,
14081 these commands make it easy to construct @value{GDBN} scripts that
14082 scan through the trace buffer and print out whatever collected data
14083 you are interested in. Thus, if we want to examine the PC, FP, and SP
14084 registers from each trace frame in the buffer, we can say this:
14087 (@value{GDBP}) @b{tfind start}
14088 (@value{GDBP}) @b{while ($trace_frame != -1)}
14089 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14090 $trace_frame, $pc, $sp, $fp
14094 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14095 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14096 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14097 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14098 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14099 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14100 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14101 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14102 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14103 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14104 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14107 Or, if we want to examine the variable @code{X} at each source line in
14111 (@value{GDBP}) @b{tfind start}
14112 (@value{GDBP}) @b{while ($trace_frame != -1)}
14113 > printf "Frame %d, X == %d\n", $trace_frame, X
14123 @subsection @code{tdump}
14125 @cindex dump all data collected at tracepoint
14126 @cindex tracepoint data, display
14128 This command takes no arguments. It prints all the data collected at
14129 the current trace snapshot.
14132 (@value{GDBP}) @b{trace 444}
14133 (@value{GDBP}) @b{actions}
14134 Enter actions for tracepoint #2, one per line:
14135 > collect $regs, $locals, $args, gdb_long_test
14138 (@value{GDBP}) @b{tstart}
14140 (@value{GDBP}) @b{tfind line 444}
14141 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14143 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14145 (@value{GDBP}) @b{tdump}
14146 Data collected at tracepoint 2, trace frame 1:
14147 d0 0xc4aa0085 -995491707
14151 d4 0x71aea3d 119204413
14154 d7 0x380035 3670069
14155 a0 0x19e24a 1696330
14156 a1 0x3000668 50333288
14158 a3 0x322000 3284992
14159 a4 0x3000698 50333336
14160 a5 0x1ad3cc 1758156
14161 fp 0x30bf3c 0x30bf3c
14162 sp 0x30bf34 0x30bf34
14164 pc 0x20b2c8 0x20b2c8
14168 p = 0x20e5b4 "gdb-test"
14175 gdb_long_test = 17 '\021'
14180 @code{tdump} works by scanning the tracepoint's current collection
14181 actions and printing the value of each expression listed. So
14182 @code{tdump} can fail, if after a run, you change the tracepoint's
14183 actions to mention variables that were not collected during the run.
14185 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14186 uses the collected value of @code{$pc} to distinguish between trace
14187 frames that were collected at the tracepoint hit, and frames that were
14188 collected while stepping. This allows it to correctly choose whether
14189 to display the basic list of collections, or the collections from the
14190 body of the while-stepping loop. However, if @code{$pc} was not collected,
14191 then @code{tdump} will always attempt to dump using the basic collection
14192 list, and may fail if a while-stepping frame does not include all the
14193 same data that is collected at the tracepoint hit.
14194 @c This is getting pretty arcane, example would be good.
14196 @node save tracepoints
14197 @subsection @code{save tracepoints @var{filename}}
14198 @kindex save tracepoints
14199 @kindex save-tracepoints
14200 @cindex save tracepoints for future sessions
14202 This command saves all current tracepoint definitions together with
14203 their actions and passcounts, into a file @file{@var{filename}}
14204 suitable for use in a later debugging session. To read the saved
14205 tracepoint definitions, use the @code{source} command (@pxref{Command
14206 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14207 alias for @w{@code{save tracepoints}}
14209 @node Tracepoint Variables
14210 @section Convenience Variables for Tracepoints
14211 @cindex tracepoint variables
14212 @cindex convenience variables for tracepoints
14215 @vindex $trace_frame
14216 @item (int) $trace_frame
14217 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14218 snapshot is selected.
14220 @vindex $tracepoint
14221 @item (int) $tracepoint
14222 The tracepoint for the current trace snapshot.
14224 @vindex $trace_line
14225 @item (int) $trace_line
14226 The line number for the current trace snapshot.
14228 @vindex $trace_file
14229 @item (char []) $trace_file
14230 The source file for the current trace snapshot.
14232 @vindex $trace_func
14233 @item (char []) $trace_func
14234 The name of the function containing @code{$tracepoint}.
14237 Note: @code{$trace_file} is not suitable for use in @code{printf},
14238 use @code{output} instead.
14240 Here's a simple example of using these convenience variables for
14241 stepping through all the trace snapshots and printing some of their
14242 data. Note that these are not the same as trace state variables,
14243 which are managed by the target.
14246 (@value{GDBP}) @b{tfind start}
14248 (@value{GDBP}) @b{while $trace_frame != -1}
14249 > output $trace_file
14250 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14256 @section Using Trace Files
14257 @cindex trace files
14259 In some situations, the target running a trace experiment may no
14260 longer be available; perhaps it crashed, or the hardware was needed
14261 for a different activity. To handle these cases, you can arrange to
14262 dump the trace data into a file, and later use that file as a source
14263 of trace data, via the @code{target tfile} command.
14268 @item tsave [ -r ] @var{filename}
14269 @itemx tsave [-ctf] @var{dirname}
14270 Save the trace data to @var{filename}. By default, this command
14271 assumes that @var{filename} refers to the host filesystem, so if
14272 necessary @value{GDBN} will copy raw trace data up from the target and
14273 then save it. If the target supports it, you can also supply the
14274 optional argument @code{-r} (``remote'') to direct the target to save
14275 the data directly into @var{filename} in its own filesystem, which may be
14276 more efficient if the trace buffer is very large. (Note, however, that
14277 @code{target tfile} can only read from files accessible to the host.)
14278 By default, this command will save trace frame in tfile format.
14279 You can supply the optional argument @code{-ctf} to save data in CTF
14280 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14281 that can be shared by multiple debugging and tracing tools. Please go to
14282 @indicateurl{http://www.efficios.com/ctf} to get more information.
14284 @kindex target tfile
14288 @item target tfile @var{filename}
14289 @itemx target ctf @var{dirname}
14290 Use the file named @var{filename} or directory named @var{dirname} as
14291 a source of trace data. Commands that examine data work as they do with
14292 a live target, but it is not possible to run any new trace experiments.
14293 @code{tstatus} will report the state of the trace run at the moment
14294 the data was saved, as well as the current trace frame you are examining.
14295 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14299 (@value{GDBP}) target ctf ctf.ctf
14300 (@value{GDBP}) tfind
14301 Found trace frame 0, tracepoint 2
14302 39 ++a; /* set tracepoint 1 here */
14303 (@value{GDBP}) tdump
14304 Data collected at tracepoint 2, trace frame 0:
14308 c = @{"123", "456", "789", "123", "456", "789"@}
14309 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14317 @chapter Debugging Programs That Use Overlays
14320 If your program is too large to fit completely in your target system's
14321 memory, you can sometimes use @dfn{overlays} to work around this
14322 problem. @value{GDBN} provides some support for debugging programs that
14326 * How Overlays Work:: A general explanation of overlays.
14327 * Overlay Commands:: Managing overlays in @value{GDBN}.
14328 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14329 mapped by asking the inferior.
14330 * Overlay Sample Program:: A sample program using overlays.
14333 @node How Overlays Work
14334 @section How Overlays Work
14335 @cindex mapped overlays
14336 @cindex unmapped overlays
14337 @cindex load address, overlay's
14338 @cindex mapped address
14339 @cindex overlay area
14341 Suppose you have a computer whose instruction address space is only 64
14342 kilobytes long, but which has much more memory which can be accessed by
14343 other means: special instructions, segment registers, or memory
14344 management hardware, for example. Suppose further that you want to
14345 adapt a program which is larger than 64 kilobytes to run on this system.
14347 One solution is to identify modules of your program which are relatively
14348 independent, and need not call each other directly; call these modules
14349 @dfn{overlays}. Separate the overlays from the main program, and place
14350 their machine code in the larger memory. Place your main program in
14351 instruction memory, but leave at least enough space there to hold the
14352 largest overlay as well.
14354 Now, to call a function located in an overlay, you must first copy that
14355 overlay's machine code from the large memory into the space set aside
14356 for it in the instruction memory, and then jump to its entry point
14359 @c NB: In the below the mapped area's size is greater or equal to the
14360 @c size of all overlays. This is intentional to remind the developer
14361 @c that overlays don't necessarily need to be the same size.
14365 Data Instruction Larger
14366 Address Space Address Space Address Space
14367 +-----------+ +-----------+ +-----------+
14369 +-----------+ +-----------+ +-----------+<-- overlay 1
14370 | program | | main | .----| overlay 1 | load address
14371 | variables | | program | | +-----------+
14372 | and heap | | | | | |
14373 +-----------+ | | | +-----------+<-- overlay 2
14374 | | +-----------+ | | | load address
14375 +-----------+ | | | .-| overlay 2 |
14377 mapped --->+-----------+ | | +-----------+
14378 address | | | | | |
14379 | overlay | <-' | | |
14380 | area | <---' +-----------+<-- overlay 3
14381 | | <---. | | load address
14382 +-----------+ `--| overlay 3 |
14389 @anchor{A code overlay}A code overlay
14393 The diagram (@pxref{A code overlay}) shows a system with separate data
14394 and instruction address spaces. To map an overlay, the program copies
14395 its code from the larger address space to the instruction address space.
14396 Since the overlays shown here all use the same mapped address, only one
14397 may be mapped at a time. For a system with a single address space for
14398 data and instructions, the diagram would be similar, except that the
14399 program variables and heap would share an address space with the main
14400 program and the overlay area.
14402 An overlay loaded into instruction memory and ready for use is called a
14403 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14404 instruction memory. An overlay not present (or only partially present)
14405 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14406 is its address in the larger memory. The mapped address is also called
14407 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14408 called the @dfn{load memory address}, or @dfn{LMA}.
14410 Unfortunately, overlays are not a completely transparent way to adapt a
14411 program to limited instruction memory. They introduce a new set of
14412 global constraints you must keep in mind as you design your program:
14417 Before calling or returning to a function in an overlay, your program
14418 must make sure that overlay is actually mapped. Otherwise, the call or
14419 return will transfer control to the right address, but in the wrong
14420 overlay, and your program will probably crash.
14423 If the process of mapping an overlay is expensive on your system, you
14424 will need to choose your overlays carefully to minimize their effect on
14425 your program's performance.
14428 The executable file you load onto your system must contain each
14429 overlay's instructions, appearing at the overlay's load address, not its
14430 mapped address. However, each overlay's instructions must be relocated
14431 and its symbols defined as if the overlay were at its mapped address.
14432 You can use GNU linker scripts to specify different load and relocation
14433 addresses for pieces of your program; see @ref{Overlay Description,,,
14434 ld.info, Using ld: the GNU linker}.
14437 The procedure for loading executable files onto your system must be able
14438 to load their contents into the larger address space as well as the
14439 instruction and data spaces.
14443 The overlay system described above is rather simple, and could be
14444 improved in many ways:
14449 If your system has suitable bank switch registers or memory management
14450 hardware, you could use those facilities to make an overlay's load area
14451 contents simply appear at their mapped address in instruction space.
14452 This would probably be faster than copying the overlay to its mapped
14453 area in the usual way.
14456 If your overlays are small enough, you could set aside more than one
14457 overlay area, and have more than one overlay mapped at a time.
14460 You can use overlays to manage data, as well as instructions. In
14461 general, data overlays are even less transparent to your design than
14462 code overlays: whereas code overlays only require care when you call or
14463 return to functions, data overlays require care every time you access
14464 the data. Also, if you change the contents of a data overlay, you
14465 must copy its contents back out to its load address before you can copy a
14466 different data overlay into the same mapped area.
14471 @node Overlay Commands
14472 @section Overlay Commands
14474 To use @value{GDBN}'s overlay support, each overlay in your program must
14475 correspond to a separate section of the executable file. The section's
14476 virtual memory address and load memory address must be the overlay's
14477 mapped and load addresses. Identifying overlays with sections allows
14478 @value{GDBN} to determine the appropriate address of a function or
14479 variable, depending on whether the overlay is mapped or not.
14481 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14482 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14487 Disable @value{GDBN}'s overlay support. When overlay support is
14488 disabled, @value{GDBN} assumes that all functions and variables are
14489 always present at their mapped addresses. By default, @value{GDBN}'s
14490 overlay support is disabled.
14492 @item overlay manual
14493 @cindex manual overlay debugging
14494 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14495 relies on you to tell it which overlays are mapped, and which are not,
14496 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14497 commands described below.
14499 @item overlay map-overlay @var{overlay}
14500 @itemx overlay map @var{overlay}
14501 @cindex map an overlay
14502 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14503 be the name of the object file section containing the overlay. When an
14504 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14505 functions and variables at their mapped addresses. @value{GDBN} assumes
14506 that any other overlays whose mapped ranges overlap that of
14507 @var{overlay} are now unmapped.
14509 @item overlay unmap-overlay @var{overlay}
14510 @itemx overlay unmap @var{overlay}
14511 @cindex unmap an overlay
14512 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14513 must be the name of the object file section containing the overlay.
14514 When an overlay is unmapped, @value{GDBN} assumes it can find the
14515 overlay's functions and variables at their load addresses.
14518 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14519 consults a data structure the overlay manager maintains in the inferior
14520 to see which overlays are mapped. For details, see @ref{Automatic
14521 Overlay Debugging}.
14523 @item overlay load-target
14524 @itemx overlay load
14525 @cindex reloading the overlay table
14526 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14527 re-reads the table @value{GDBN} automatically each time the inferior
14528 stops, so this command should only be necessary if you have changed the
14529 overlay mapping yourself using @value{GDBN}. This command is only
14530 useful when using automatic overlay debugging.
14532 @item overlay list-overlays
14533 @itemx overlay list
14534 @cindex listing mapped overlays
14535 Display a list of the overlays currently mapped, along with their mapped
14536 addresses, load addresses, and sizes.
14540 Normally, when @value{GDBN} prints a code address, it includes the name
14541 of the function the address falls in:
14544 (@value{GDBP}) print main
14545 $3 = @{int ()@} 0x11a0 <main>
14548 When overlay debugging is enabled, @value{GDBN} recognizes code in
14549 unmapped overlays, and prints the names of unmapped functions with
14550 asterisks around them. For example, if @code{foo} is a function in an
14551 unmapped overlay, @value{GDBN} prints it this way:
14554 (@value{GDBP}) overlay list
14555 No sections are mapped.
14556 (@value{GDBP}) print foo
14557 $5 = @{int (int)@} 0x100000 <*foo*>
14560 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14564 (@value{GDBP}) overlay list
14565 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14566 mapped at 0x1016 - 0x104a
14567 (@value{GDBP}) print foo
14568 $6 = @{int (int)@} 0x1016 <foo>
14571 When overlay debugging is enabled, @value{GDBN} can find the correct
14572 address for functions and variables in an overlay, whether or not the
14573 overlay is mapped. This allows most @value{GDBN} commands, like
14574 @code{break} and @code{disassemble}, to work normally, even on unmapped
14575 code. However, @value{GDBN}'s breakpoint support has some limitations:
14579 @cindex breakpoints in overlays
14580 @cindex overlays, setting breakpoints in
14581 You can set breakpoints in functions in unmapped overlays, as long as
14582 @value{GDBN} can write to the overlay at its load address.
14584 @value{GDBN} can not set hardware or simulator-based breakpoints in
14585 unmapped overlays. However, if you set a breakpoint at the end of your
14586 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14587 you are using manual overlay management), @value{GDBN} will re-set its
14588 breakpoints properly.
14592 @node Automatic Overlay Debugging
14593 @section Automatic Overlay Debugging
14594 @cindex automatic overlay debugging
14596 @value{GDBN} can automatically track which overlays are mapped and which
14597 are not, given some simple co-operation from the overlay manager in the
14598 inferior. If you enable automatic overlay debugging with the
14599 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14600 looks in the inferior's memory for certain variables describing the
14601 current state of the overlays.
14603 Here are the variables your overlay manager must define to support
14604 @value{GDBN}'s automatic overlay debugging:
14608 @item @code{_ovly_table}:
14609 This variable must be an array of the following structures:
14614 /* The overlay's mapped address. */
14617 /* The size of the overlay, in bytes. */
14618 unsigned long size;
14620 /* The overlay's load address. */
14623 /* Non-zero if the overlay is currently mapped;
14625 unsigned long mapped;
14629 @item @code{_novlys}:
14630 This variable must be a four-byte signed integer, holding the total
14631 number of elements in @code{_ovly_table}.
14635 To decide whether a particular overlay is mapped or not, @value{GDBN}
14636 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14637 @code{lma} members equal the VMA and LMA of the overlay's section in the
14638 executable file. When @value{GDBN} finds a matching entry, it consults
14639 the entry's @code{mapped} member to determine whether the overlay is
14642 In addition, your overlay manager may define a function called
14643 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14644 will silently set a breakpoint there. If the overlay manager then
14645 calls this function whenever it has changed the overlay table, this
14646 will enable @value{GDBN} to accurately keep track of which overlays
14647 are in program memory, and update any breakpoints that may be set
14648 in overlays. This will allow breakpoints to work even if the
14649 overlays are kept in ROM or other non-writable memory while they
14650 are not being executed.
14652 @node Overlay Sample Program
14653 @section Overlay Sample Program
14654 @cindex overlay example program
14656 When linking a program which uses overlays, you must place the overlays
14657 at their load addresses, while relocating them to run at their mapped
14658 addresses. To do this, you must write a linker script (@pxref{Overlay
14659 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14660 since linker scripts are specific to a particular host system, target
14661 architecture, and target memory layout, this manual cannot provide
14662 portable sample code demonstrating @value{GDBN}'s overlay support.
14664 However, the @value{GDBN} source distribution does contain an overlaid
14665 program, with linker scripts for a few systems, as part of its test
14666 suite. The program consists of the following files from
14667 @file{gdb/testsuite/gdb.base}:
14671 The main program file.
14673 A simple overlay manager, used by @file{overlays.c}.
14678 Overlay modules, loaded and used by @file{overlays.c}.
14681 Linker scripts for linking the test program on the @code{d10v-elf}
14682 and @code{m32r-elf} targets.
14685 You can build the test program using the @code{d10v-elf} GCC
14686 cross-compiler like this:
14689 $ d10v-elf-gcc -g -c overlays.c
14690 $ d10v-elf-gcc -g -c ovlymgr.c
14691 $ d10v-elf-gcc -g -c foo.c
14692 $ d10v-elf-gcc -g -c bar.c
14693 $ d10v-elf-gcc -g -c baz.c
14694 $ d10v-elf-gcc -g -c grbx.c
14695 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14696 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14699 The build process is identical for any other architecture, except that
14700 you must substitute the appropriate compiler and linker script for the
14701 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14705 @chapter Using @value{GDBN} with Different Languages
14708 Although programming languages generally have common aspects, they are
14709 rarely expressed in the same manner. For instance, in ANSI C,
14710 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14711 Modula-2, it is accomplished by @code{p^}. Values can also be
14712 represented (and displayed) differently. Hex numbers in C appear as
14713 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14715 @cindex working language
14716 Language-specific information is built into @value{GDBN} for some languages,
14717 allowing you to express operations like the above in your program's
14718 native language, and allowing @value{GDBN} to output values in a manner
14719 consistent with the syntax of your program's native language. The
14720 language you use to build expressions is called the @dfn{working
14724 * Setting:: Switching between source languages
14725 * Show:: Displaying the language
14726 * Checks:: Type and range checks
14727 * Supported Languages:: Supported languages
14728 * Unsupported Languages:: Unsupported languages
14732 @section Switching Between Source Languages
14734 There are two ways to control the working language---either have @value{GDBN}
14735 set it automatically, or select it manually yourself. You can use the
14736 @code{set language} command for either purpose. On startup, @value{GDBN}
14737 defaults to setting the language automatically. The working language is
14738 used to determine how expressions you type are interpreted, how values
14741 In addition to the working language, every source file that
14742 @value{GDBN} knows about has its own working language. For some object
14743 file formats, the compiler might indicate which language a particular
14744 source file is in. However, most of the time @value{GDBN} infers the
14745 language from the name of the file. The language of a source file
14746 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14747 show each frame appropriately for its own language. There is no way to
14748 set the language of a source file from within @value{GDBN}, but you can
14749 set the language associated with a filename extension. @xref{Show, ,
14750 Displaying the Language}.
14752 This is most commonly a problem when you use a program, such
14753 as @code{cfront} or @code{f2c}, that generates C but is written in
14754 another language. In that case, make the
14755 program use @code{#line} directives in its C output; that way
14756 @value{GDBN} will know the correct language of the source code of the original
14757 program, and will display that source code, not the generated C code.
14760 * Filenames:: Filename extensions and languages.
14761 * Manually:: Setting the working language manually
14762 * Automatically:: Having @value{GDBN} infer the source language
14766 @subsection List of Filename Extensions and Languages
14768 If a source file name ends in one of the following extensions, then
14769 @value{GDBN} infers that its language is the one indicated.
14787 C@t{++} source file
14793 Objective-C source file
14797 Fortran source file
14800 Modula-2 source file
14804 Assembler source file. This actually behaves almost like C, but
14805 @value{GDBN} does not skip over function prologues when stepping.
14808 In addition, you may set the language associated with a filename
14809 extension. @xref{Show, , Displaying the Language}.
14812 @subsection Setting the Working Language
14814 If you allow @value{GDBN} to set the language automatically,
14815 expressions are interpreted the same way in your debugging session and
14818 @kindex set language
14819 If you wish, you may set the language manually. To do this, issue the
14820 command @samp{set language @var{lang}}, where @var{lang} is the name of
14821 a language, such as
14822 @code{c} or @code{modula-2}.
14823 For a list of the supported languages, type @samp{set language}.
14825 Setting the language manually prevents @value{GDBN} from updating the working
14826 language automatically. This can lead to confusion if you try
14827 to debug a program when the working language is not the same as the
14828 source language, when an expression is acceptable to both
14829 languages---but means different things. For instance, if the current
14830 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14838 might not have the effect you intended. In C, this means to add
14839 @code{b} and @code{c} and place the result in @code{a}. The result
14840 printed would be the value of @code{a}. In Modula-2, this means to compare
14841 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14843 @node Automatically
14844 @subsection Having @value{GDBN} Infer the Source Language
14846 To have @value{GDBN} set the working language automatically, use
14847 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14848 then infers the working language. That is, when your program stops in a
14849 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14850 working language to the language recorded for the function in that
14851 frame. If the language for a frame is unknown (that is, if the function
14852 or block corresponding to the frame was defined in a source file that
14853 does not have a recognized extension), the current working language is
14854 not changed, and @value{GDBN} issues a warning.
14856 This may not seem necessary for most programs, which are written
14857 entirely in one source language. However, program modules and libraries
14858 written in one source language can be used by a main program written in
14859 a different source language. Using @samp{set language auto} in this
14860 case frees you from having to set the working language manually.
14863 @section Displaying the Language
14865 The following commands help you find out which language is the
14866 working language, and also what language source files were written in.
14869 @item show language
14870 @anchor{show language}
14871 @kindex show language
14872 Display the current working language. This is the
14873 language you can use with commands such as @code{print} to
14874 build and compute expressions that may involve variables in your program.
14877 @kindex info frame@r{, show the source language}
14878 Display the source language for this frame. This language becomes the
14879 working language if you use an identifier from this frame.
14880 @xref{Frame Info, ,Information about a Frame}, to identify the other
14881 information listed here.
14884 @kindex info source@r{, show the source language}
14885 Display the source language of this source file.
14886 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14887 information listed here.
14890 In unusual circumstances, you may have source files with extensions
14891 not in the standard list. You can then set the extension associated
14892 with a language explicitly:
14895 @item set extension-language @var{ext} @var{language}
14896 @kindex set extension-language
14897 Tell @value{GDBN} that source files with extension @var{ext} are to be
14898 assumed as written in the source language @var{language}.
14900 @item info extensions
14901 @kindex info extensions
14902 List all the filename extensions and the associated languages.
14906 @section Type and Range Checking
14908 Some languages are designed to guard you against making seemingly common
14909 errors through a series of compile- and run-time checks. These include
14910 checking the type of arguments to functions and operators and making
14911 sure mathematical overflows are caught at run time. Checks such as
14912 these help to ensure a program's correctness once it has been compiled
14913 by eliminating type mismatches and providing active checks for range
14914 errors when your program is running.
14916 By default @value{GDBN} checks for these errors according to the
14917 rules of the current source language. Although @value{GDBN} does not check
14918 the statements in your program, it can check expressions entered directly
14919 into @value{GDBN} for evaluation via the @code{print} command, for example.
14922 * Type Checking:: An overview of type checking
14923 * Range Checking:: An overview of range checking
14926 @cindex type checking
14927 @cindex checks, type
14928 @node Type Checking
14929 @subsection An Overview of Type Checking
14931 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14932 arguments to operators and functions have to be of the correct type,
14933 otherwise an error occurs. These checks prevent type mismatch
14934 errors from ever causing any run-time problems. For example,
14937 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14939 (@value{GDBP}) print obj.my_method (0)
14942 (@value{GDBP}) print obj.my_method (0x1234)
14943 Cannot resolve method klass::my_method to any overloaded instance
14946 The second example fails because in C@t{++} the integer constant
14947 @samp{0x1234} is not type-compatible with the pointer parameter type.
14949 For the expressions you use in @value{GDBN} commands, you can tell
14950 @value{GDBN} to not enforce strict type checking or
14951 to treat any mismatches as errors and abandon the expression;
14952 When type checking is disabled, @value{GDBN} successfully evaluates
14953 expressions like the second example above.
14955 Even if type checking is off, there may be other reasons
14956 related to type that prevent @value{GDBN} from evaluating an expression.
14957 For instance, @value{GDBN} does not know how to add an @code{int} and
14958 a @code{struct foo}. These particular type errors have nothing to do
14959 with the language in use and usually arise from expressions which make
14960 little sense to evaluate anyway.
14962 @value{GDBN} provides some additional commands for controlling type checking:
14964 @kindex set check type
14965 @kindex show check type
14967 @item set check type on
14968 @itemx set check type off
14969 Set strict type checking on or off. If any type mismatches occur in
14970 evaluating an expression while type checking is on, @value{GDBN} prints a
14971 message and aborts evaluation of the expression.
14973 @item show check type
14974 Show the current setting of type checking and whether @value{GDBN}
14975 is enforcing strict type checking rules.
14978 @cindex range checking
14979 @cindex checks, range
14980 @node Range Checking
14981 @subsection An Overview of Range Checking
14983 In some languages (such as Modula-2), it is an error to exceed the
14984 bounds of a type; this is enforced with run-time checks. Such range
14985 checking is meant to ensure program correctness by making sure
14986 computations do not overflow, or indices on an array element access do
14987 not exceed the bounds of the array.
14989 For expressions you use in @value{GDBN} commands, you can tell
14990 @value{GDBN} to treat range errors in one of three ways: ignore them,
14991 always treat them as errors and abandon the expression, or issue
14992 warnings but evaluate the expression anyway.
14994 A range error can result from numerical overflow, from exceeding an
14995 array index bound, or when you type a constant that is not a member
14996 of any type. Some languages, however, do not treat overflows as an
14997 error. In many implementations of C, mathematical overflow causes the
14998 result to ``wrap around'' to lower values---for example, if @var{m} is
14999 the largest integer value, and @var{s} is the smallest, then
15002 @var{m} + 1 @result{} @var{s}
15005 This, too, is specific to individual languages, and in some cases
15006 specific to individual compilers or machines. @xref{Supported Languages, ,
15007 Supported Languages}, for further details on specific languages.
15009 @value{GDBN} provides some additional commands for controlling the range checker:
15011 @kindex set check range
15012 @kindex show check range
15014 @item set check range auto
15015 Set range checking on or off based on the current working language.
15016 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15019 @item set check range on
15020 @itemx set check range off
15021 Set range checking on or off, overriding the default setting for the
15022 current working language. A warning is issued if the setting does not
15023 match the language default. If a range error occurs and range checking is on,
15024 then a message is printed and evaluation of the expression is aborted.
15026 @item set check range warn
15027 Output messages when the @value{GDBN} range checker detects a range error,
15028 but attempt to evaluate the expression anyway. Evaluating the
15029 expression may still be impossible for other reasons, such as accessing
15030 memory that the process does not own (a typical example from many Unix
15034 Show the current setting of the range checker, and whether or not it is
15035 being set automatically by @value{GDBN}.
15038 @node Supported Languages
15039 @section Supported Languages
15041 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15042 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15043 @c This is false ...
15044 Some @value{GDBN} features may be used in expressions regardless of the
15045 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15046 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15047 ,Expressions}) can be used with the constructs of any supported
15050 The following sections detail to what degree each source language is
15051 supported by @value{GDBN}. These sections are not meant to be language
15052 tutorials or references, but serve only as a reference guide to what the
15053 @value{GDBN} expression parser accepts, and what input and output
15054 formats should look like for different languages. There are many good
15055 books written on each of these languages; please look to these for a
15056 language reference or tutorial.
15059 * C:: C and C@t{++}
15062 * Objective-C:: Objective-C
15063 * OpenCL C:: OpenCL C
15064 * Fortran:: Fortran
15067 * Modula-2:: Modula-2
15072 @subsection C and C@t{++}
15074 @cindex C and C@t{++}
15075 @cindex expressions in C or C@t{++}
15077 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15078 to both languages. Whenever this is the case, we discuss those languages
15082 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15083 @cindex @sc{gnu} C@t{++}
15084 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15085 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15086 effectively, you must compile your C@t{++} programs with a supported
15087 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15088 compiler (@code{aCC}).
15091 * C Operators:: C and C@t{++} operators
15092 * C Constants:: C and C@t{++} constants
15093 * C Plus Plus Expressions:: C@t{++} expressions
15094 * C Defaults:: Default settings for C and C@t{++}
15095 * C Checks:: C and C@t{++} type and range checks
15096 * Debugging C:: @value{GDBN} and C
15097 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15098 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15102 @subsubsection C and C@t{++} Operators
15104 @cindex C and C@t{++} operators
15106 Operators must be defined on values of specific types. For instance,
15107 @code{+} is defined on numbers, but not on structures. Operators are
15108 often defined on groups of types.
15110 For the purposes of C and C@t{++}, the following definitions hold:
15115 @emph{Integral types} include @code{int} with any of its storage-class
15116 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15119 @emph{Floating-point types} include @code{float}, @code{double}, and
15120 @code{long double} (if supported by the target platform).
15123 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15126 @emph{Scalar types} include all of the above.
15131 The following operators are supported. They are listed here
15132 in order of increasing precedence:
15136 The comma or sequencing operator. Expressions in a comma-separated list
15137 are evaluated from left to right, with the result of the entire
15138 expression being the last expression evaluated.
15141 Assignment. The value of an assignment expression is the value
15142 assigned. Defined on scalar types.
15145 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15146 and translated to @w{@code{@var{a} = @var{a op b}}}.
15147 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15148 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15149 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15152 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15153 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15154 should be of an integral type.
15157 Logical @sc{or}. Defined on integral types.
15160 Logical @sc{and}. Defined on integral types.
15163 Bitwise @sc{or}. Defined on integral types.
15166 Bitwise exclusive-@sc{or}. Defined on integral types.
15169 Bitwise @sc{and}. Defined on integral types.
15172 Equality and inequality. Defined on scalar types. The value of these
15173 expressions is 0 for false and non-zero for true.
15175 @item <@r{, }>@r{, }<=@r{, }>=
15176 Less than, greater than, less than or equal, greater than or equal.
15177 Defined on scalar types. The value of these expressions is 0 for false
15178 and non-zero for true.
15181 left shift, and right shift. Defined on integral types.
15184 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15187 Addition and subtraction. Defined on integral types, floating-point types and
15190 @item *@r{, }/@r{, }%
15191 Multiplication, division, and modulus. Multiplication and division are
15192 defined on integral and floating-point types. Modulus is defined on
15196 Increment and decrement. When appearing before a variable, the
15197 operation is performed before the variable is used in an expression;
15198 when appearing after it, the variable's value is used before the
15199 operation takes place.
15202 Pointer dereferencing. Defined on pointer types. Same precedence as
15206 Address operator. Defined on variables. Same precedence as @code{++}.
15208 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15209 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15210 to examine the address
15211 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15215 Negative. Defined on integral and floating-point types. Same
15216 precedence as @code{++}.
15219 Logical negation. Defined on integral types. Same precedence as
15223 Bitwise complement operator. Defined on integral types. Same precedence as
15228 Structure member, and pointer-to-structure member. For convenience,
15229 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15230 pointer based on the stored type information.
15231 Defined on @code{struct} and @code{union} data.
15234 Dereferences of pointers to members.
15237 Array indexing. @code{@var{a}[@var{i}]} is defined as
15238 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15241 Function parameter list. Same precedence as @code{->}.
15244 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15245 and @code{class} types.
15248 Doubled colons also represent the @value{GDBN} scope operator
15249 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15253 If an operator is redefined in the user code, @value{GDBN} usually
15254 attempts to invoke the redefined version instead of using the operator's
15255 predefined meaning.
15258 @subsubsection C and C@t{++} Constants
15260 @cindex C and C@t{++} constants
15262 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15267 Integer constants are a sequence of digits. Octal constants are
15268 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15269 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15270 @samp{l}, specifying that the constant should be treated as a
15274 Floating point constants are a sequence of digits, followed by a decimal
15275 point, followed by a sequence of digits, and optionally followed by an
15276 exponent. An exponent is of the form:
15277 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15278 sequence of digits. The @samp{+} is optional for positive exponents.
15279 A floating-point constant may also end with a letter @samp{f} or
15280 @samp{F}, specifying that the constant should be treated as being of
15281 the @code{float} (as opposed to the default @code{double}) type; or with
15282 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15286 Enumerated constants consist of enumerated identifiers, or their
15287 integral equivalents.
15290 Character constants are a single character surrounded by single quotes
15291 (@code{'}), or a number---the ordinal value of the corresponding character
15292 (usually its @sc{ascii} value). Within quotes, the single character may
15293 be represented by a letter or by @dfn{escape sequences}, which are of
15294 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15295 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15296 @samp{@var{x}} is a predefined special character---for example,
15297 @samp{\n} for newline.
15299 Wide character constants can be written by prefixing a character
15300 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15301 form of @samp{x}. The target wide character set is used when
15302 computing the value of this constant (@pxref{Character Sets}).
15305 String constants are a sequence of character constants surrounded by
15306 double quotes (@code{"}). Any valid character constant (as described
15307 above) may appear. Double quotes within the string must be preceded by
15308 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15311 Wide string constants can be written by prefixing a string constant
15312 with @samp{L}, as in C. The target wide character set is used when
15313 computing the value of this constant (@pxref{Character Sets}).
15316 Pointer constants are an integral value. You can also write pointers
15317 to constants using the C operator @samp{&}.
15320 Array constants are comma-separated lists surrounded by braces @samp{@{}
15321 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15322 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15323 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15326 @node C Plus Plus Expressions
15327 @subsubsection C@t{++} Expressions
15329 @cindex expressions in C@t{++}
15330 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15332 @cindex debugging C@t{++} programs
15333 @cindex C@t{++} compilers
15334 @cindex debug formats and C@t{++}
15335 @cindex @value{NGCC} and C@t{++}
15337 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15338 the proper compiler and the proper debug format. Currently,
15339 @value{GDBN} works best when debugging C@t{++} code that is compiled
15340 with the most recent version of @value{NGCC} possible. The DWARF
15341 debugging format is preferred; @value{NGCC} defaults to this on most
15342 popular platforms. Other compilers and/or debug formats are likely to
15343 work badly or not at all when using @value{GDBN} to debug C@t{++}
15344 code. @xref{Compilation}.
15349 @cindex member functions
15351 Member function calls are allowed; you can use expressions like
15354 count = aml->GetOriginal(x, y)
15357 @vindex this@r{, inside C@t{++} member functions}
15358 @cindex namespace in C@t{++}
15360 While a member function is active (in the selected stack frame), your
15361 expressions have the same namespace available as the member function;
15362 that is, @value{GDBN} allows implicit references to the class instance
15363 pointer @code{this} following the same rules as C@t{++}. @code{using}
15364 declarations in the current scope are also respected by @value{GDBN}.
15366 @cindex call overloaded functions
15367 @cindex overloaded functions, calling
15368 @cindex type conversions in C@t{++}
15370 You can call overloaded functions; @value{GDBN} resolves the function
15371 call to the right definition, with some restrictions. @value{GDBN} does not
15372 perform overload resolution involving user-defined type conversions,
15373 calls to constructors, or instantiations of templates that do not exist
15374 in the program. It also cannot handle ellipsis argument lists or
15377 It does perform integral conversions and promotions, floating-point
15378 promotions, arithmetic conversions, pointer conversions, conversions of
15379 class objects to base classes, and standard conversions such as those of
15380 functions or arrays to pointers; it requires an exact match on the
15381 number of function arguments.
15383 Overload resolution is always performed, unless you have specified
15384 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15385 ,@value{GDBN} Features for C@t{++}}.
15387 You must specify @code{set overload-resolution off} in order to use an
15388 explicit function signature to call an overloaded function, as in
15390 p 'foo(char,int)'('x', 13)
15393 The @value{GDBN} command-completion facility can simplify this;
15394 see @ref{Completion, ,Command Completion}.
15396 @cindex reference declarations
15398 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15399 references; you can use them in expressions just as you do in C@t{++}
15400 source---they are automatically dereferenced.
15402 In the parameter list shown when @value{GDBN} displays a frame, the values of
15403 reference variables are not displayed (unlike other variables); this
15404 avoids clutter, since references are often used for large structures.
15405 The @emph{address} of a reference variable is always shown, unless
15406 you have specified @samp{set print address off}.
15409 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15410 expressions can use it just as expressions in your program do. Since
15411 one scope may be defined in another, you can use @code{::} repeatedly if
15412 necessary, for example in an expression like
15413 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15414 resolving name scope by reference to source files, in both C and C@t{++}
15415 debugging (@pxref{Variables, ,Program Variables}).
15418 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15423 @subsubsection C and C@t{++} Defaults
15425 @cindex C and C@t{++} defaults
15427 If you allow @value{GDBN} to set range checking automatically, it
15428 defaults to @code{off} whenever the working language changes to
15429 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15430 selects the working language.
15432 If you allow @value{GDBN} to set the language automatically, it
15433 recognizes source files whose names end with @file{.c}, @file{.C}, or
15434 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15435 these files, it sets the working language to C or C@t{++}.
15436 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15437 for further details.
15440 @subsubsection C and C@t{++} Type and Range Checks
15442 @cindex C and C@t{++} checks
15444 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15445 checking is used. However, if you turn type checking off, @value{GDBN}
15446 will allow certain non-standard conversions, such as promoting integer
15447 constants to pointers.
15449 Range checking, if turned on, is done on mathematical operations. Array
15450 indices are not checked, since they are often used to index a pointer
15451 that is not itself an array.
15454 @subsubsection @value{GDBN} and C
15456 The @code{set print union} and @code{show print union} commands apply to
15457 the @code{union} type. When set to @samp{on}, any @code{union} that is
15458 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15459 appears as @samp{@{...@}}.
15461 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15462 with pointers and a memory allocation function. @xref{Expressions,
15465 @node Debugging C Plus Plus
15466 @subsubsection @value{GDBN} Features for C@t{++}
15468 @cindex commands for C@t{++}
15470 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15471 designed specifically for use with C@t{++}. Here is a summary:
15474 @cindex break in overloaded functions
15475 @item @r{breakpoint menus}
15476 When you want a breakpoint in a function whose name is overloaded,
15477 @value{GDBN} has the capability to display a menu of possible breakpoint
15478 locations to help you specify which function definition you want.
15479 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15481 @cindex overloading in C@t{++}
15482 @item rbreak @var{regex}
15483 Setting breakpoints using regular expressions is helpful for setting
15484 breakpoints on overloaded functions that are not members of any special
15486 @xref{Set Breaks, ,Setting Breakpoints}.
15488 @cindex C@t{++} exception handling
15490 @itemx catch rethrow
15492 Debug C@t{++} exception handling using these commands. @xref{Set
15493 Catchpoints, , Setting Catchpoints}.
15495 @cindex inheritance
15496 @item ptype @var{typename}
15497 Print inheritance relationships as well as other information for type
15499 @xref{Symbols, ,Examining the Symbol Table}.
15501 @item info vtbl @var{expression}.
15502 The @code{info vtbl} command can be used to display the virtual
15503 method tables of the object computed by @var{expression}. This shows
15504 one entry per virtual table; there may be multiple virtual tables when
15505 multiple inheritance is in use.
15507 @cindex C@t{++} demangling
15508 @item demangle @var{name}
15509 Demangle @var{name}.
15510 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15512 @cindex C@t{++} symbol display
15513 @item set print demangle
15514 @itemx show print demangle
15515 @itemx set print asm-demangle
15516 @itemx show print asm-demangle
15517 Control whether C@t{++} symbols display in their source form, both when
15518 displaying code as C@t{++} source and when displaying disassemblies.
15519 @xref{Print Settings, ,Print Settings}.
15521 @item set print object
15522 @itemx show print object
15523 Choose whether to print derived (actual) or declared types of objects.
15524 @xref{Print Settings, ,Print Settings}.
15526 @item set print vtbl
15527 @itemx show print vtbl
15528 Control the format for printing virtual function tables.
15529 @xref{Print Settings, ,Print Settings}.
15530 (The @code{vtbl} commands do not work on programs compiled with the HP
15531 ANSI C@t{++} compiler (@code{aCC}).)
15533 @kindex set overload-resolution
15534 @cindex overloaded functions, overload resolution
15535 @item set overload-resolution on
15536 Enable overload resolution for C@t{++} expression evaluation. The default
15537 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15538 and searches for a function whose signature matches the argument types,
15539 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15540 Expressions, ,C@t{++} Expressions}, for details).
15541 If it cannot find a match, it emits a message.
15543 @item set overload-resolution off
15544 Disable overload resolution for C@t{++} expression evaluation. For
15545 overloaded functions that are not class member functions, @value{GDBN}
15546 chooses the first function of the specified name that it finds in the
15547 symbol table, whether or not its arguments are of the correct type. For
15548 overloaded functions that are class member functions, @value{GDBN}
15549 searches for a function whose signature @emph{exactly} matches the
15552 @kindex show overload-resolution
15553 @item show overload-resolution
15554 Show the current setting of overload resolution.
15556 @item @r{Overloaded symbol names}
15557 You can specify a particular definition of an overloaded symbol, using
15558 the same notation that is used to declare such symbols in C@t{++}: type
15559 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15560 also use the @value{GDBN} command-line word completion facilities to list the
15561 available choices, or to finish the type list for you.
15562 @xref{Completion,, Command Completion}, for details on how to do this.
15564 @item @r{Breakpoints in functions with ABI tags}
15566 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15567 correspond to changes in the ABI of a type, function, or variable that
15568 would not otherwise be reflected in a mangled name. See
15569 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15572 The ABI tags are visible in C@t{++} demangled names. For example, a
15573 function that returns a std::string:
15576 std::string function(int);
15580 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15581 tag, and @value{GDBN} displays the symbol like this:
15584 function[abi:cxx11](int)
15587 You can set a breakpoint on such functions simply as if they had no
15591 (gdb) b function(int)
15592 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15593 (gdb) info breakpoints
15594 Num Type Disp Enb Address What
15595 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15599 On the rare occasion you need to disambiguate between different ABI
15600 tags, you can do so by simply including the ABI tag in the function
15604 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15608 @node Decimal Floating Point
15609 @subsubsection Decimal Floating Point format
15610 @cindex decimal floating point format
15612 @value{GDBN} can examine, set and perform computations with numbers in
15613 decimal floating point format, which in the C language correspond to the
15614 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15615 specified by the extension to support decimal floating-point arithmetic.
15617 There are two encodings in use, depending on the architecture: BID (Binary
15618 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15619 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15622 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15623 to manipulate decimal floating point numbers, it is not possible to convert
15624 (using a cast, for example) integers wider than 32-bit to decimal float.
15626 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15627 point computations, error checking in decimal float operations ignores
15628 underflow, overflow and divide by zero exceptions.
15630 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15631 to inspect @code{_Decimal128} values stored in floating point registers.
15632 See @ref{PowerPC,,PowerPC} for more details.
15638 @value{GDBN} can be used to debug programs written in D and compiled with
15639 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15640 specific feature --- dynamic arrays.
15645 @cindex Go (programming language)
15646 @value{GDBN} can be used to debug programs written in Go and compiled with
15647 @file{gccgo} or @file{6g} compilers.
15649 Here is a summary of the Go-specific features and restrictions:
15652 @cindex current Go package
15653 @item The current Go package
15654 The name of the current package does not need to be specified when
15655 specifying global variables and functions.
15657 For example, given the program:
15661 var myglob = "Shall we?"
15667 When stopped inside @code{main} either of these work:
15671 (gdb) p main.myglob
15674 @cindex builtin Go types
15675 @item Builtin Go types
15676 The @code{string} type is recognized by @value{GDBN} and is printed
15679 @cindex builtin Go functions
15680 @item Builtin Go functions
15681 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15682 function and handles it internally.
15684 @cindex restrictions on Go expressions
15685 @item Restrictions on Go expressions
15686 All Go operators are supported except @code{&^}.
15687 The Go @code{_} ``blank identifier'' is not supported.
15688 Automatic dereferencing of pointers is not supported.
15692 @subsection Objective-C
15694 @cindex Objective-C
15695 This section provides information about some commands and command
15696 options that are useful for debugging Objective-C code. See also
15697 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15698 few more commands specific to Objective-C support.
15701 * Method Names in Commands::
15702 * The Print Command with Objective-C::
15705 @node Method Names in Commands
15706 @subsubsection Method Names in Commands
15708 The following commands have been extended to accept Objective-C method
15709 names as line specifications:
15711 @kindex clear@r{, and Objective-C}
15712 @kindex break@r{, and Objective-C}
15713 @kindex info line@r{, and Objective-C}
15714 @kindex jump@r{, and Objective-C}
15715 @kindex list@r{, and Objective-C}
15719 @item @code{info line}
15724 A fully qualified Objective-C method name is specified as
15727 -[@var{Class} @var{methodName}]
15730 where the minus sign is used to indicate an instance method and a
15731 plus sign (not shown) is used to indicate a class method. The class
15732 name @var{Class} and method name @var{methodName} are enclosed in
15733 brackets, similar to the way messages are specified in Objective-C
15734 source code. For example, to set a breakpoint at the @code{create}
15735 instance method of class @code{Fruit} in the program currently being
15739 break -[Fruit create]
15742 To list ten program lines around the @code{initialize} class method,
15746 list +[NSText initialize]
15749 In the current version of @value{GDBN}, the plus or minus sign is
15750 required. In future versions of @value{GDBN}, the plus or minus
15751 sign will be optional, but you can use it to narrow the search. It
15752 is also possible to specify just a method name:
15758 You must specify the complete method name, including any colons. If
15759 your program's source files contain more than one @code{create} method,
15760 you'll be presented with a numbered list of classes that implement that
15761 method. Indicate your choice by number, or type @samp{0} to exit if
15764 As another example, to clear a breakpoint established at the
15765 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15768 clear -[NSWindow makeKeyAndOrderFront:]
15771 @node The Print Command with Objective-C
15772 @subsubsection The Print Command With Objective-C
15773 @cindex Objective-C, print objects
15774 @kindex print-object
15775 @kindex po @r{(@code{print-object})}
15777 The print command has also been extended to accept methods. For example:
15780 print -[@var{object} hash]
15783 @cindex print an Objective-C object description
15784 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15786 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15787 and print the result. Also, an additional command has been added,
15788 @code{print-object} or @code{po} for short, which is meant to print
15789 the description of an object. However, this command may only work
15790 with certain Objective-C libraries that have a particular hook
15791 function, @code{_NSPrintForDebugger}, defined.
15794 @subsection OpenCL C
15797 This section provides information about @value{GDBN}s OpenCL C support.
15800 * OpenCL C Datatypes::
15801 * OpenCL C Expressions::
15802 * OpenCL C Operators::
15805 @node OpenCL C Datatypes
15806 @subsubsection OpenCL C Datatypes
15808 @cindex OpenCL C Datatypes
15809 @value{GDBN} supports the builtin scalar and vector datatypes specified
15810 by OpenCL 1.1. In addition the half- and double-precision floating point
15811 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15812 extensions are also known to @value{GDBN}.
15814 @node OpenCL C Expressions
15815 @subsubsection OpenCL C Expressions
15817 @cindex OpenCL C Expressions
15818 @value{GDBN} supports accesses to vector components including the access as
15819 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15820 supported by @value{GDBN} can be used as well.
15822 @node OpenCL C Operators
15823 @subsubsection OpenCL C Operators
15825 @cindex OpenCL C Operators
15826 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15830 @subsection Fortran
15831 @cindex Fortran-specific support in @value{GDBN}
15833 @value{GDBN} can be used to debug programs written in Fortran, but it
15834 currently supports only the features of Fortran 77 language.
15836 @cindex trailing underscore, in Fortran symbols
15837 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15838 among them) append an underscore to the names of variables and
15839 functions. When you debug programs compiled by those compilers, you
15840 will need to refer to variables and functions with a trailing
15844 * Fortran Operators:: Fortran operators and expressions
15845 * Fortran Defaults:: Default settings for Fortran
15846 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15849 @node Fortran Operators
15850 @subsubsection Fortran Operators and Expressions
15852 @cindex Fortran operators and expressions
15854 Operators must be defined on values of specific types. For instance,
15855 @code{+} is defined on numbers, but not on characters or other non-
15856 arithmetic types. Operators are often defined on groups of types.
15860 The exponentiation operator. It raises the first operand to the power
15864 The range operator. Normally used in the form of array(low:high) to
15865 represent a section of array.
15868 The access component operator. Normally used to access elements in derived
15869 types. Also suitable for unions. As unions aren't part of regular Fortran,
15870 this can only happen when accessing a register that uses a gdbarch-defined
15874 @node Fortran Defaults
15875 @subsubsection Fortran Defaults
15877 @cindex Fortran Defaults
15879 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15880 default uses case-insensitive matches for Fortran symbols. You can
15881 change that with the @samp{set case-insensitive} command, see
15882 @ref{Symbols}, for the details.
15884 @node Special Fortran Commands
15885 @subsubsection Special Fortran Commands
15887 @cindex Special Fortran commands
15889 @value{GDBN} has some commands to support Fortran-specific features,
15890 such as displaying common blocks.
15893 @cindex @code{COMMON} blocks, Fortran
15894 @kindex info common
15895 @item info common @r{[}@var{common-name}@r{]}
15896 This command prints the values contained in the Fortran @code{COMMON}
15897 block whose name is @var{common-name}. With no argument, the names of
15898 all @code{COMMON} blocks visible at the current program location are
15905 @cindex Pascal support in @value{GDBN}, limitations
15906 Debugging Pascal programs which use sets, subranges, file variables, or
15907 nested functions does not currently work. @value{GDBN} does not support
15908 entering expressions, printing values, or similar features using Pascal
15911 The Pascal-specific command @code{set print pascal_static-members}
15912 controls whether static members of Pascal objects are displayed.
15913 @xref{Print Settings, pascal_static-members}.
15918 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15919 Programming Language}. Type- and value-printing, and expression
15920 parsing, are reasonably complete. However, there are a few
15921 peculiarities and holes to be aware of.
15925 Linespecs (@pxref{Specify Location}) are never relative to the current
15926 crate. Instead, they act as if there were a global namespace of
15927 crates, somewhat similar to the way @code{extern crate} behaves.
15929 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15930 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15931 to set a breakpoint in a function named @samp{f} in a crate named
15934 As a consequence of this approach, linespecs also cannot refer to
15935 items using @samp{self::} or @samp{super::}.
15938 Because @value{GDBN} implements Rust name-lookup semantics in
15939 expressions, it will sometimes prepend the current crate to a name.
15940 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15941 @samp{K}, then @code{print ::x::y} will try to find the symbol
15944 However, since it is useful to be able to refer to other crates when
15945 debugging, @value{GDBN} provides the @code{extern} extension to
15946 circumvent this. To use the extension, just put @code{extern} before
15947 a path expression to refer to the otherwise unavailable ``global''
15950 In the above example, if you wanted to refer to the symbol @samp{y} in
15951 the crate @samp{x}, you would use @code{print extern x::y}.
15954 The Rust expression evaluator does not support ``statement-like''
15955 expressions such as @code{if} or @code{match}, or lambda expressions.
15958 Tuple expressions are not implemented.
15961 The Rust expression evaluator does not currently implement the
15962 @code{Drop} trait. Objects that may be created by the evaluator will
15963 never be destroyed.
15966 @value{GDBN} does not implement type inference for generics. In order
15967 to call generic functions or otherwise refer to generic items, you
15968 will have to specify the type parameters manually.
15971 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15972 cases this does not cause any problems. However, in an expression
15973 context, completing a generic function name will give syntactically
15974 invalid results. This happens because Rust requires the @samp{::}
15975 operator between the function name and its generic arguments. For
15976 example, @value{GDBN} might provide a completion like
15977 @code{crate::f<u32>}, where the parser would require
15978 @code{crate::f::<u32>}.
15981 As of this writing, the Rust compiler (version 1.8) has a few holes in
15982 the debugging information it generates. These holes prevent certain
15983 features from being implemented by @value{GDBN}:
15987 Method calls cannot be made via traits.
15990 Operator overloading is not implemented.
15993 When debugging in a monomorphized function, you cannot use the generic
15997 The type @code{Self} is not available.
16000 @code{use} statements are not available, so some names may not be
16001 available in the crate.
16006 @subsection Modula-2
16008 @cindex Modula-2, @value{GDBN} support
16010 The extensions made to @value{GDBN} to support Modula-2 only support
16011 output from the @sc{gnu} Modula-2 compiler (which is currently being
16012 developed). Other Modula-2 compilers are not currently supported, and
16013 attempting to debug executables produced by them is most likely
16014 to give an error as @value{GDBN} reads in the executable's symbol
16017 @cindex expressions in Modula-2
16019 * M2 Operators:: Built-in operators
16020 * Built-In Func/Proc:: Built-in functions and procedures
16021 * M2 Constants:: Modula-2 constants
16022 * M2 Types:: Modula-2 types
16023 * M2 Defaults:: Default settings for Modula-2
16024 * Deviations:: Deviations from standard Modula-2
16025 * M2 Checks:: Modula-2 type and range checks
16026 * M2 Scope:: The scope operators @code{::} and @code{.}
16027 * GDB/M2:: @value{GDBN} and Modula-2
16031 @subsubsection Operators
16032 @cindex Modula-2 operators
16034 Operators must be defined on values of specific types. For instance,
16035 @code{+} is defined on numbers, but not on structures. Operators are
16036 often defined on groups of types. For the purposes of Modula-2, the
16037 following definitions hold:
16042 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16046 @emph{Character types} consist of @code{CHAR} and its subranges.
16049 @emph{Floating-point types} consist of @code{REAL}.
16052 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16056 @emph{Scalar types} consist of all of the above.
16059 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16062 @emph{Boolean types} consist of @code{BOOLEAN}.
16066 The following operators are supported, and appear in order of
16067 increasing precedence:
16071 Function argument or array index separator.
16074 Assignment. The value of @var{var} @code{:=} @var{value} is
16078 Less than, greater than on integral, floating-point, or enumerated
16082 Less than or equal to, greater than or equal to
16083 on integral, floating-point and enumerated types, or set inclusion on
16084 set types. Same precedence as @code{<}.
16086 @item =@r{, }<>@r{, }#
16087 Equality and two ways of expressing inequality, valid on scalar types.
16088 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16089 available for inequality, since @code{#} conflicts with the script
16093 Set membership. Defined on set types and the types of their members.
16094 Same precedence as @code{<}.
16097 Boolean disjunction. Defined on boolean types.
16100 Boolean conjunction. Defined on boolean types.
16103 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16106 Addition and subtraction on integral and floating-point types, or union
16107 and difference on set types.
16110 Multiplication on integral and floating-point types, or set intersection
16114 Division on floating-point types, or symmetric set difference on set
16115 types. Same precedence as @code{*}.
16118 Integer division and remainder. Defined on integral types. Same
16119 precedence as @code{*}.
16122 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16125 Pointer dereferencing. Defined on pointer types.
16128 Boolean negation. Defined on boolean types. Same precedence as
16132 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16133 precedence as @code{^}.
16136 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16139 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16143 @value{GDBN} and Modula-2 scope operators.
16147 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16148 treats the use of the operator @code{IN}, or the use of operators
16149 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16150 @code{<=}, and @code{>=} on sets as an error.
16154 @node Built-In Func/Proc
16155 @subsubsection Built-in Functions and Procedures
16156 @cindex Modula-2 built-ins
16158 Modula-2 also makes available several built-in procedures and functions.
16159 In describing these, the following metavariables are used:
16164 represents an @code{ARRAY} variable.
16167 represents a @code{CHAR} constant or variable.
16170 represents a variable or constant of integral type.
16173 represents an identifier that belongs to a set. Generally used in the
16174 same function with the metavariable @var{s}. The type of @var{s} should
16175 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16178 represents a variable or constant of integral or floating-point type.
16181 represents a variable or constant of floating-point type.
16187 represents a variable.
16190 represents a variable or constant of one of many types. See the
16191 explanation of the function for details.
16194 All Modula-2 built-in procedures also return a result, described below.
16198 Returns the absolute value of @var{n}.
16201 If @var{c} is a lower case letter, it returns its upper case
16202 equivalent, otherwise it returns its argument.
16205 Returns the character whose ordinal value is @var{i}.
16208 Decrements the value in the variable @var{v} by one. Returns the new value.
16210 @item DEC(@var{v},@var{i})
16211 Decrements the value in the variable @var{v} by @var{i}. Returns the
16214 @item EXCL(@var{m},@var{s})
16215 Removes the element @var{m} from the set @var{s}. Returns the new
16218 @item FLOAT(@var{i})
16219 Returns the floating point equivalent of the integer @var{i}.
16221 @item HIGH(@var{a})
16222 Returns the index of the last member of @var{a}.
16225 Increments the value in the variable @var{v} by one. Returns the new value.
16227 @item INC(@var{v},@var{i})
16228 Increments the value in the variable @var{v} by @var{i}. Returns the
16231 @item INCL(@var{m},@var{s})
16232 Adds the element @var{m} to the set @var{s} if it is not already
16233 there. Returns the new set.
16236 Returns the maximum value of the type @var{t}.
16239 Returns the minimum value of the type @var{t}.
16242 Returns boolean TRUE if @var{i} is an odd number.
16245 Returns the ordinal value of its argument. For example, the ordinal
16246 value of a character is its @sc{ascii} value (on machines supporting
16247 the @sc{ascii} character set). The argument @var{x} must be of an
16248 ordered type, which include integral, character and enumerated types.
16250 @item SIZE(@var{x})
16251 Returns the size of its argument. The argument @var{x} can be a
16252 variable or a type.
16254 @item TRUNC(@var{r})
16255 Returns the integral part of @var{r}.
16257 @item TSIZE(@var{x})
16258 Returns the size of its argument. The argument @var{x} can be a
16259 variable or a type.
16261 @item VAL(@var{t},@var{i})
16262 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16266 @emph{Warning:} Sets and their operations are not yet supported, so
16267 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16271 @cindex Modula-2 constants
16273 @subsubsection Constants
16275 @value{GDBN} allows you to express the constants of Modula-2 in the following
16281 Integer constants are simply a sequence of digits. When used in an
16282 expression, a constant is interpreted to be type-compatible with the
16283 rest of the expression. Hexadecimal integers are specified by a
16284 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16287 Floating point constants appear as a sequence of digits, followed by a
16288 decimal point and another sequence of digits. An optional exponent can
16289 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16290 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16291 digits of the floating point constant must be valid decimal (base 10)
16295 Character constants consist of a single character enclosed by a pair of
16296 like quotes, either single (@code{'}) or double (@code{"}). They may
16297 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16298 followed by a @samp{C}.
16301 String constants consist of a sequence of characters enclosed by a
16302 pair of like quotes, either single (@code{'}) or double (@code{"}).
16303 Escape sequences in the style of C are also allowed. @xref{C
16304 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16308 Enumerated constants consist of an enumerated identifier.
16311 Boolean constants consist of the identifiers @code{TRUE} and
16315 Pointer constants consist of integral values only.
16318 Set constants are not yet supported.
16322 @subsubsection Modula-2 Types
16323 @cindex Modula-2 types
16325 Currently @value{GDBN} can print the following data types in Modula-2
16326 syntax: array types, record types, set types, pointer types, procedure
16327 types, enumerated types, subrange types and base types. You can also
16328 print the contents of variables declared using these type.
16329 This section gives a number of simple source code examples together with
16330 sample @value{GDBN} sessions.
16332 The first example contains the following section of code:
16341 and you can request @value{GDBN} to interrogate the type and value of
16342 @code{r} and @code{s}.
16345 (@value{GDBP}) print s
16347 (@value{GDBP}) ptype s
16349 (@value{GDBP}) print r
16351 (@value{GDBP}) ptype r
16356 Likewise if your source code declares @code{s} as:
16360 s: SET ['A'..'Z'] ;
16364 then you may query the type of @code{s} by:
16367 (@value{GDBP}) ptype s
16368 type = SET ['A'..'Z']
16372 Note that at present you cannot interactively manipulate set
16373 expressions using the debugger.
16375 The following example shows how you might declare an array in Modula-2
16376 and how you can interact with @value{GDBN} to print its type and contents:
16380 s: ARRAY [-10..10] OF CHAR ;
16384 (@value{GDBP}) ptype s
16385 ARRAY [-10..10] OF CHAR
16388 Note that the array handling is not yet complete and although the type
16389 is printed correctly, expression handling still assumes that all
16390 arrays have a lower bound of zero and not @code{-10} as in the example
16393 Here are some more type related Modula-2 examples:
16397 colour = (blue, red, yellow, green) ;
16398 t = [blue..yellow] ;
16406 The @value{GDBN} interaction shows how you can query the data type
16407 and value of a variable.
16410 (@value{GDBP}) print s
16412 (@value{GDBP}) ptype t
16413 type = [blue..yellow]
16417 In this example a Modula-2 array is declared and its contents
16418 displayed. Observe that the contents are written in the same way as
16419 their @code{C} counterparts.
16423 s: ARRAY [1..5] OF CARDINAL ;
16429 (@value{GDBP}) print s
16430 $1 = @{1, 0, 0, 0, 0@}
16431 (@value{GDBP}) ptype s
16432 type = ARRAY [1..5] OF CARDINAL
16435 The Modula-2 language interface to @value{GDBN} also understands
16436 pointer types as shown in this example:
16440 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16447 and you can request that @value{GDBN} describes the type of @code{s}.
16450 (@value{GDBP}) ptype s
16451 type = POINTER TO ARRAY [1..5] OF CARDINAL
16454 @value{GDBN} handles compound types as we can see in this example.
16455 Here we combine array types, record types, pointer types and subrange
16466 myarray = ARRAY myrange OF CARDINAL ;
16467 myrange = [-2..2] ;
16469 s: POINTER TO ARRAY myrange OF foo ;
16473 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16477 (@value{GDBP}) ptype s
16478 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16481 f3 : ARRAY [-2..2] OF CARDINAL;
16486 @subsubsection Modula-2 Defaults
16487 @cindex Modula-2 defaults
16489 If type and range checking are set automatically by @value{GDBN}, they
16490 both default to @code{on} whenever the working language changes to
16491 Modula-2. This happens regardless of whether you or @value{GDBN}
16492 selected the working language.
16494 If you allow @value{GDBN} to set the language automatically, then entering
16495 code compiled from a file whose name ends with @file{.mod} sets the
16496 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16497 Infer the Source Language}, for further details.
16500 @subsubsection Deviations from Standard Modula-2
16501 @cindex Modula-2, deviations from
16503 A few changes have been made to make Modula-2 programs easier to debug.
16504 This is done primarily via loosening its type strictness:
16508 Unlike in standard Modula-2, pointer constants can be formed by
16509 integers. This allows you to modify pointer variables during
16510 debugging. (In standard Modula-2, the actual address contained in a
16511 pointer variable is hidden from you; it can only be modified
16512 through direct assignment to another pointer variable or expression that
16513 returned a pointer.)
16516 C escape sequences can be used in strings and characters to represent
16517 non-printable characters. @value{GDBN} prints out strings with these
16518 escape sequences embedded. Single non-printable characters are
16519 printed using the @samp{CHR(@var{nnn})} format.
16522 The assignment operator (@code{:=}) returns the value of its right-hand
16526 All built-in procedures both modify @emph{and} return their argument.
16530 @subsubsection Modula-2 Type and Range Checks
16531 @cindex Modula-2 checks
16534 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16537 @c FIXME remove warning when type/range checks added
16539 @value{GDBN} considers two Modula-2 variables type equivalent if:
16543 They are of types that have been declared equivalent via a @code{TYPE
16544 @var{t1} = @var{t2}} statement
16547 They have been declared on the same line. (Note: This is true of the
16548 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16551 As long as type checking is enabled, any attempt to combine variables
16552 whose types are not equivalent is an error.
16554 Range checking is done on all mathematical operations, assignment, array
16555 index bounds, and all built-in functions and procedures.
16558 @subsubsection The Scope Operators @code{::} and @code{.}
16560 @cindex @code{.}, Modula-2 scope operator
16561 @cindex colon, doubled as scope operator
16563 @vindex colon-colon@r{, in Modula-2}
16564 @c Info cannot handle :: but TeX can.
16567 @vindex ::@r{, in Modula-2}
16570 There are a few subtle differences between the Modula-2 scope operator
16571 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16576 @var{module} . @var{id}
16577 @var{scope} :: @var{id}
16581 where @var{scope} is the name of a module or a procedure,
16582 @var{module} the name of a module, and @var{id} is any declared
16583 identifier within your program, except another module.
16585 Using the @code{::} operator makes @value{GDBN} search the scope
16586 specified by @var{scope} for the identifier @var{id}. If it is not
16587 found in the specified scope, then @value{GDBN} searches all scopes
16588 enclosing the one specified by @var{scope}.
16590 Using the @code{.} operator makes @value{GDBN} search the current scope for
16591 the identifier specified by @var{id} that was imported from the
16592 definition module specified by @var{module}. With this operator, it is
16593 an error if the identifier @var{id} was not imported from definition
16594 module @var{module}, or if @var{id} is not an identifier in
16598 @subsubsection @value{GDBN} and Modula-2
16600 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16601 Five subcommands of @code{set print} and @code{show print} apply
16602 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16603 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16604 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16605 analogue in Modula-2.
16607 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16608 with any language, is not useful with Modula-2. Its
16609 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16610 created in Modula-2 as they can in C or C@t{++}. However, because an
16611 address can be specified by an integral constant, the construct
16612 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16614 @cindex @code{#} in Modula-2
16615 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16616 interpreted as the beginning of a comment. Use @code{<>} instead.
16622 The extensions made to @value{GDBN} for Ada only support
16623 output from the @sc{gnu} Ada (GNAT) compiler.
16624 Other Ada compilers are not currently supported, and
16625 attempting to debug executables produced by them is most likely
16629 @cindex expressions in Ada
16631 * Ada Mode Intro:: General remarks on the Ada syntax
16632 and semantics supported by Ada mode
16634 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16635 * Additions to Ada:: Extensions of the Ada expression syntax.
16636 * Overloading support for Ada:: Support for expressions involving overloaded
16638 * Stopping Before Main Program:: Debugging the program during elaboration.
16639 * Ada Exceptions:: Ada Exceptions
16640 * Ada Tasks:: Listing and setting breakpoints in tasks.
16641 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16642 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16644 * Ada Settings:: New settable GDB parameters for Ada.
16645 * Ada Glitches:: Known peculiarities of Ada mode.
16648 @node Ada Mode Intro
16649 @subsubsection Introduction
16650 @cindex Ada mode, general
16652 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16653 syntax, with some extensions.
16654 The philosophy behind the design of this subset is
16658 That @value{GDBN} should provide basic literals and access to operations for
16659 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16660 leaving more sophisticated computations to subprograms written into the
16661 program (which therefore may be called from @value{GDBN}).
16664 That type safety and strict adherence to Ada language restrictions
16665 are not particularly important to the @value{GDBN} user.
16668 That brevity is important to the @value{GDBN} user.
16671 Thus, for brevity, the debugger acts as if all names declared in
16672 user-written packages are directly visible, even if they are not visible
16673 according to Ada rules, thus making it unnecessary to fully qualify most
16674 names with their packages, regardless of context. Where this causes
16675 ambiguity, @value{GDBN} asks the user's intent.
16677 The debugger will start in Ada mode if it detects an Ada main program.
16678 As for other languages, it will enter Ada mode when stopped in a program that
16679 was translated from an Ada source file.
16681 While in Ada mode, you may use `@t{--}' for comments. This is useful
16682 mostly for documenting command files. The standard @value{GDBN} comment
16683 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16684 middle (to allow based literals).
16686 @node Omissions from Ada
16687 @subsubsection Omissions from Ada
16688 @cindex Ada, omissions from
16690 Here are the notable omissions from the subset:
16694 Only a subset of the attributes are supported:
16698 @t{'First}, @t{'Last}, and @t{'Length}
16699 on array objects (not on types and subtypes).
16702 @t{'Min} and @t{'Max}.
16705 @t{'Pos} and @t{'Val}.
16711 @t{'Range} on array objects (not subtypes), but only as the right
16712 operand of the membership (@code{in}) operator.
16715 @t{'Access}, @t{'Unchecked_Access}, and
16716 @t{'Unrestricted_Access} (a GNAT extension).
16724 @code{Characters.Latin_1} are not available and
16725 concatenation is not implemented. Thus, escape characters in strings are
16726 not currently available.
16729 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16730 equality of representations. They will generally work correctly
16731 for strings and arrays whose elements have integer or enumeration types.
16732 They may not work correctly for arrays whose element
16733 types have user-defined equality, for arrays of real values
16734 (in particular, IEEE-conformant floating point, because of negative
16735 zeroes and NaNs), and for arrays whose elements contain unused bits with
16736 indeterminate values.
16739 The other component-by-component array operations (@code{and}, @code{or},
16740 @code{xor}, @code{not}, and relational tests other than equality)
16741 are not implemented.
16744 @cindex array aggregates (Ada)
16745 @cindex record aggregates (Ada)
16746 @cindex aggregates (Ada)
16747 There is limited support for array and record aggregates. They are
16748 permitted only on the right sides of assignments, as in these examples:
16751 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16752 (@value{GDBP}) set An_Array := (1, others => 0)
16753 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16754 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16755 (@value{GDBP}) set A_Record := (1, "Peter", True);
16756 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16760 discriminant's value by assigning an aggregate has an
16761 undefined effect if that discriminant is used within the record.
16762 However, you can first modify discriminants by directly assigning to
16763 them (which normally would not be allowed in Ada), and then performing an
16764 aggregate assignment. For example, given a variable @code{A_Rec}
16765 declared to have a type such as:
16768 type Rec (Len : Small_Integer := 0) is record
16770 Vals : IntArray (1 .. Len);
16774 you can assign a value with a different size of @code{Vals} with two
16778 (@value{GDBP}) set A_Rec.Len := 4
16779 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16782 As this example also illustrates, @value{GDBN} is very loose about the usual
16783 rules concerning aggregates. You may leave out some of the
16784 components of an array or record aggregate (such as the @code{Len}
16785 component in the assignment to @code{A_Rec} above); they will retain their
16786 original values upon assignment. You may freely use dynamic values as
16787 indices in component associations. You may even use overlapping or
16788 redundant component associations, although which component values are
16789 assigned in such cases is not defined.
16792 Calls to dispatching subprograms are not implemented.
16795 The overloading algorithm is much more limited (i.e., less selective)
16796 than that of real Ada. It makes only limited use of the context in
16797 which a subexpression appears to resolve its meaning, and it is much
16798 looser in its rules for allowing type matches. As a result, some
16799 function calls will be ambiguous, and the user will be asked to choose
16800 the proper resolution.
16803 The @code{new} operator is not implemented.
16806 Entry calls are not implemented.
16809 Aside from printing, arithmetic operations on the native VAX floating-point
16810 formats are not supported.
16813 It is not possible to slice a packed array.
16816 The names @code{True} and @code{False}, when not part of a qualified name,
16817 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16819 Should your program
16820 redefine these names in a package or procedure (at best a dubious practice),
16821 you will have to use fully qualified names to access their new definitions.
16824 @node Additions to Ada
16825 @subsubsection Additions to Ada
16826 @cindex Ada, deviations from
16828 As it does for other languages, @value{GDBN} makes certain generic
16829 extensions to Ada (@pxref{Expressions}):
16833 If the expression @var{E} is a variable residing in memory (typically
16834 a local variable or array element) and @var{N} is a positive integer,
16835 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16836 @var{N}-1 adjacent variables following it in memory as an array. In
16837 Ada, this operator is generally not necessary, since its prime use is
16838 in displaying parts of an array, and slicing will usually do this in
16839 Ada. However, there are occasional uses when debugging programs in
16840 which certain debugging information has been optimized away.
16843 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16844 appears in function or file @var{B}.'' When @var{B} is a file name,
16845 you must typically surround it in single quotes.
16848 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16849 @var{type} that appears at address @var{addr}.''
16852 A name starting with @samp{$} is a convenience variable
16853 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16856 In addition, @value{GDBN} provides a few other shortcuts and outright
16857 additions specific to Ada:
16861 The assignment statement is allowed as an expression, returning
16862 its right-hand operand as its value. Thus, you may enter
16865 (@value{GDBP}) set x := y + 3
16866 (@value{GDBP}) print A(tmp := y + 1)
16870 The semicolon is allowed as an ``operator,'' returning as its value
16871 the value of its right-hand operand.
16872 This allows, for example,
16873 complex conditional breaks:
16876 (@value{GDBP}) break f
16877 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16881 Rather than use catenation and symbolic character names to introduce special
16882 characters into strings, one may instead use a special bracket notation,
16883 which is also used to print strings. A sequence of characters of the form
16884 @samp{["@var{XX}"]} within a string or character literal denotes the
16885 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16886 sequence of characters @samp{["""]} also denotes a single quotation mark
16887 in strings. For example,
16889 "One line.["0a"]Next line.["0a"]"
16892 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16896 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16897 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16901 (@value{GDBP}) print 'max(x, y)
16905 When printing arrays, @value{GDBN} uses positional notation when the
16906 array has a lower bound of 1, and uses a modified named notation otherwise.
16907 For example, a one-dimensional array of three integers with a lower bound
16908 of 3 might print as
16915 That is, in contrast to valid Ada, only the first component has a @code{=>}
16919 You may abbreviate attributes in expressions with any unique,
16920 multi-character subsequence of
16921 their names (an exact match gets preference).
16922 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16923 in place of @t{a'length}.
16926 @cindex quoting Ada internal identifiers
16927 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16928 to lower case. The GNAT compiler uses upper-case characters for
16929 some of its internal identifiers, which are normally of no interest to users.
16930 For the rare occasions when you actually have to look at them,
16931 enclose them in angle brackets to avoid the lower-case mapping.
16934 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16938 Printing an object of class-wide type or dereferencing an
16939 access-to-class-wide value will display all the components of the object's
16940 specific type (as indicated by its run-time tag). Likewise, component
16941 selection on such a value will operate on the specific type of the
16946 @node Overloading support for Ada
16947 @subsubsection Overloading support for Ada
16948 @cindex overloading, Ada
16950 The debugger supports limited overloading. Given a subprogram call in which
16951 the function symbol has multiple definitions, it will use the number of
16952 actual parameters and some information about their types to attempt to narrow
16953 the set of definitions. It also makes very limited use of context, preferring
16954 procedures to functions in the context of the @code{call} command, and
16955 functions to procedures elsewhere.
16957 If, after narrowing, the set of matching definitions still contains more than
16958 one definition, @value{GDBN} will display a menu to query which one it should
16962 (@value{GDBP}) print f(1)
16963 Multiple matches for f
16965 [1] foo.f (integer) return boolean at foo.adb:23
16966 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16970 In this case, just select one menu entry either to cancel expression evaluation
16971 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16972 instance (type the corresponding number and press @key{RET}).
16974 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16979 @kindex set ada print-signatures
16980 @item set ada print-signatures
16981 Control whether parameter types and return types are displayed in overloads
16982 selection menus. It is @code{on} by default.
16983 @xref{Overloading support for Ada}.
16985 @kindex show ada print-signatures
16986 @item show ada print-signatures
16987 Show the current setting for displaying parameter types and return types in
16988 overloads selection menu.
16989 @xref{Overloading support for Ada}.
16993 @node Stopping Before Main Program
16994 @subsubsection Stopping at the Very Beginning
16996 @cindex breakpointing Ada elaboration code
16997 It is sometimes necessary to debug the program during elaboration, and
16998 before reaching the main procedure.
16999 As defined in the Ada Reference
17000 Manual, the elaboration code is invoked from a procedure called
17001 @code{adainit}. To run your program up to the beginning of
17002 elaboration, simply use the following two commands:
17003 @code{tbreak adainit} and @code{run}.
17005 @node Ada Exceptions
17006 @subsubsection Ada Exceptions
17008 A command is provided to list all Ada exceptions:
17011 @kindex info exceptions
17012 @item info exceptions
17013 @itemx info exceptions @var{regexp}
17014 The @code{info exceptions} command allows you to list all Ada exceptions
17015 defined within the program being debugged, as well as their addresses.
17016 With a regular expression, @var{regexp}, as argument, only those exceptions
17017 whose names match @var{regexp} are listed.
17020 Below is a small example, showing how the command can be used, first
17021 without argument, and next with a regular expression passed as an
17025 (@value{GDBP}) info exceptions
17026 All defined Ada exceptions:
17027 constraint_error: 0x613da0
17028 program_error: 0x613d20
17029 storage_error: 0x613ce0
17030 tasking_error: 0x613ca0
17031 const.aint_global_e: 0x613b00
17032 (@value{GDBP}) info exceptions const.aint
17033 All Ada exceptions matching regular expression "const.aint":
17034 constraint_error: 0x613da0
17035 const.aint_global_e: 0x613b00
17038 It is also possible to ask @value{GDBN} to stop your program's execution
17039 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17042 @subsubsection Extensions for Ada Tasks
17043 @cindex Ada, tasking
17045 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17046 @value{GDBN} provides the following task-related commands:
17051 This command shows a list of current Ada tasks, as in the following example:
17058 (@value{GDBP}) info tasks
17059 ID TID P-ID Pri State Name
17060 1 8088000 0 15 Child Activation Wait main_task
17061 2 80a4000 1 15 Accept Statement b
17062 3 809a800 1 15 Child Activation Wait a
17063 * 4 80ae800 3 15 Runnable c
17068 In this listing, the asterisk before the last task indicates it to be the
17069 task currently being inspected.
17073 Represents @value{GDBN}'s internal task number.
17079 The parent's task ID (@value{GDBN}'s internal task number).
17082 The base priority of the task.
17085 Current state of the task.
17089 The task has been created but has not been activated. It cannot be
17093 The task is not blocked for any reason known to Ada. (It may be waiting
17094 for a mutex, though.) It is conceptually "executing" in normal mode.
17097 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17098 that were waiting on terminate alternatives have been awakened and have
17099 terminated themselves.
17101 @item Child Activation Wait
17102 The task is waiting for created tasks to complete activation.
17104 @item Accept Statement
17105 The task is waiting on an accept or selective wait statement.
17107 @item Waiting on entry call
17108 The task is waiting on an entry call.
17110 @item Async Select Wait
17111 The task is waiting to start the abortable part of an asynchronous
17115 The task is waiting on a select statement with only a delay
17118 @item Child Termination Wait
17119 The task is sleeping having completed a master within itself, and is
17120 waiting for the tasks dependent on that master to become terminated or
17121 waiting on a terminate Phase.
17123 @item Wait Child in Term Alt
17124 The task is sleeping waiting for tasks on terminate alternatives to
17125 finish terminating.
17127 @item Accepting RV with @var{taskno}
17128 The task is accepting a rendez-vous with the task @var{taskno}.
17132 Name of the task in the program.
17136 @kindex info task @var{taskno}
17137 @item info task @var{taskno}
17138 This command shows detailled informations on the specified task, as in
17139 the following example:
17144 (@value{GDBP}) info tasks
17145 ID TID P-ID Pri State Name
17146 1 8077880 0 15 Child Activation Wait main_task
17147 * 2 807c468 1 15 Runnable task_1
17148 (@value{GDBP}) info task 2
17149 Ada Task: 0x807c468
17153 Parent: 1 (main_task)
17159 @kindex task@r{ (Ada)}
17160 @cindex current Ada task ID
17161 This command prints the ID of the current task.
17167 (@value{GDBP}) info tasks
17168 ID TID P-ID Pri State Name
17169 1 8077870 0 15 Child Activation Wait main_task
17170 * 2 807c458 1 15 Runnable t
17171 (@value{GDBP}) task
17172 [Current task is 2]
17175 @item task @var{taskno}
17176 @cindex Ada task switching
17177 This command is like the @code{thread @var{thread-id}}
17178 command (@pxref{Threads}). It switches the context of debugging
17179 from the current task to the given task.
17185 (@value{GDBP}) info tasks
17186 ID TID P-ID Pri State Name
17187 1 8077870 0 15 Child Activation Wait main_task
17188 * 2 807c458 1 15 Runnable t
17189 (@value{GDBP}) task 1
17190 [Switching to task 1]
17191 #0 0x8067726 in pthread_cond_wait ()
17193 #0 0x8067726 in pthread_cond_wait ()
17194 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17195 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17196 #3 0x806153e in system.tasking.stages.activate_tasks ()
17197 #4 0x804aacc in un () at un.adb:5
17200 @item break @var{location} task @var{taskno}
17201 @itemx break @var{location} task @var{taskno} if @dots{}
17202 @cindex breakpoints and tasks, in Ada
17203 @cindex task breakpoints, in Ada
17204 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17205 These commands are like the @code{break @dots{} thread @dots{}}
17206 command (@pxref{Thread Stops}). The
17207 @var{location} argument specifies source lines, as described
17208 in @ref{Specify Location}.
17210 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17211 to specify that you only want @value{GDBN} to stop the program when a
17212 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17213 numeric task identifiers assigned by @value{GDBN}, shown in the first
17214 column of the @samp{info tasks} display.
17216 If you do not specify @samp{task @var{taskno}} when you set a
17217 breakpoint, the breakpoint applies to @emph{all} tasks of your
17220 You can use the @code{task} qualifier on conditional breakpoints as
17221 well; in this case, place @samp{task @var{taskno}} before the
17222 breakpoint condition (before the @code{if}).
17230 (@value{GDBP}) info tasks
17231 ID TID P-ID Pri State Name
17232 1 140022020 0 15 Child Activation Wait main_task
17233 2 140045060 1 15 Accept/Select Wait t2
17234 3 140044840 1 15 Runnable t1
17235 * 4 140056040 1 15 Runnable t3
17236 (@value{GDBP}) b 15 task 2
17237 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17238 (@value{GDBP}) cont
17243 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17245 (@value{GDBP}) info tasks
17246 ID TID P-ID Pri State Name
17247 1 140022020 0 15 Child Activation Wait main_task
17248 * 2 140045060 1 15 Runnable t2
17249 3 140044840 1 15 Runnable t1
17250 4 140056040 1 15 Delay Sleep t3
17254 @node Ada Tasks and Core Files
17255 @subsubsection Tasking Support when Debugging Core Files
17256 @cindex Ada tasking and core file debugging
17258 When inspecting a core file, as opposed to debugging a live program,
17259 tasking support may be limited or even unavailable, depending on
17260 the platform being used.
17261 For instance, on x86-linux, the list of tasks is available, but task
17262 switching is not supported.
17264 On certain platforms, the debugger needs to perform some
17265 memory writes in order to provide Ada tasking support. When inspecting
17266 a core file, this means that the core file must be opened with read-write
17267 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17268 Under these circumstances, you should make a backup copy of the core
17269 file before inspecting it with @value{GDBN}.
17271 @node Ravenscar Profile
17272 @subsubsection Tasking Support when using the Ravenscar Profile
17273 @cindex Ravenscar Profile
17275 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17276 specifically designed for systems with safety-critical real-time
17280 @kindex set ravenscar task-switching on
17281 @cindex task switching with program using Ravenscar Profile
17282 @item set ravenscar task-switching on
17283 Allows task switching when debugging a program that uses the Ravenscar
17284 Profile. This is the default.
17286 @kindex set ravenscar task-switching off
17287 @item set ravenscar task-switching off
17288 Turn off task switching when debugging a program that uses the Ravenscar
17289 Profile. This is mostly intended to disable the code that adds support
17290 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17291 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17292 To be effective, this command should be run before the program is started.
17294 @kindex show ravenscar task-switching
17295 @item show ravenscar task-switching
17296 Show whether it is possible to switch from task to task in a program
17297 using the Ravenscar Profile.
17302 @subsubsection Ada Settings
17303 @cindex Ada settings
17306 @kindex set varsize-limit
17307 @item set varsize-limit @var{size}
17308 Prevent @value{GDBN} from attempting to evaluate objects whose size
17309 is above the given limit (@var{size}) when those sizes are computed
17310 from run-time quantities. This is typically the case when the object
17311 has a variable size, such as an array whose bounds are not known at
17312 compile time for example. Setting @var{size} to @code{unlimited}
17313 removes the size limitation. By default, the limit is about 65KB.
17315 The purpose of having such a limit is to prevent @value{GDBN} from
17316 trying to grab enormous chunks of virtual memory when asked to evaluate
17317 a quantity whose bounds have been corrupted or have not yet been fully
17318 initialized. The limit applies to the results of some subexpressions
17319 as well as to complete expressions. For example, an expression denoting
17320 a simple integer component, such as @code{x.y.z}, may fail if the size of
17321 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17322 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17323 @code{A} is an array variable with non-constant size, will generally
17324 succeed regardless of the bounds on @code{A}, as long as the component
17325 size is less than @var{size}.
17327 @kindex show varsize-limit
17328 @item show varsize-limit
17329 Show the limit on types whose size is determined by run-time quantities.
17333 @subsubsection Known Peculiarities of Ada Mode
17334 @cindex Ada, problems
17336 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17337 we know of several problems with and limitations of Ada mode in
17339 some of which will be fixed with planned future releases of the debugger
17340 and the GNU Ada compiler.
17344 Static constants that the compiler chooses not to materialize as objects in
17345 storage are invisible to the debugger.
17348 Named parameter associations in function argument lists are ignored (the
17349 argument lists are treated as positional).
17352 Many useful library packages are currently invisible to the debugger.
17355 Fixed-point arithmetic, conversions, input, and output is carried out using
17356 floating-point arithmetic, and may give results that only approximate those on
17360 The GNAT compiler never generates the prefix @code{Standard} for any of
17361 the standard symbols defined by the Ada language. @value{GDBN} knows about
17362 this: it will strip the prefix from names when you use it, and will never
17363 look for a name you have so qualified among local symbols, nor match against
17364 symbols in other packages or subprograms. If you have
17365 defined entities anywhere in your program other than parameters and
17366 local variables whose simple names match names in @code{Standard},
17367 GNAT's lack of qualification here can cause confusion. When this happens,
17368 you can usually resolve the confusion
17369 by qualifying the problematic names with package
17370 @code{Standard} explicitly.
17373 Older versions of the compiler sometimes generate erroneous debugging
17374 information, resulting in the debugger incorrectly printing the value
17375 of affected entities. In some cases, the debugger is able to work
17376 around an issue automatically. In other cases, the debugger is able
17377 to work around the issue, but the work-around has to be specifically
17380 @kindex set ada trust-PAD-over-XVS
17381 @kindex show ada trust-PAD-over-XVS
17384 @item set ada trust-PAD-over-XVS on
17385 Configure GDB to strictly follow the GNAT encoding when computing the
17386 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17387 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17388 a complete description of the encoding used by the GNAT compiler).
17389 This is the default.
17391 @item set ada trust-PAD-over-XVS off
17392 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17393 sometimes prints the wrong value for certain entities, changing @code{ada
17394 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17395 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17396 @code{off}, but this incurs a slight performance penalty, so it is
17397 recommended to leave this setting to @code{on} unless necessary.
17401 @cindex GNAT descriptive types
17402 @cindex GNAT encoding
17403 Internally, the debugger also relies on the compiler following a number
17404 of conventions known as the @samp{GNAT Encoding}, all documented in
17405 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17406 how the debugging information should be generated for certain types.
17407 In particular, this convention makes use of @dfn{descriptive types},
17408 which are artificial types generated purely to help the debugger.
17410 These encodings were defined at a time when the debugging information
17411 format used was not powerful enough to describe some of the more complex
17412 types available in Ada. Since DWARF allows us to express nearly all
17413 Ada features, the long-term goal is to slowly replace these descriptive
17414 types by their pure DWARF equivalent. To facilitate that transition,
17415 a new maintenance option is available to force the debugger to ignore
17416 those descriptive types. It allows the user to quickly evaluate how
17417 well @value{GDBN} works without them.
17421 @kindex maint ada set ignore-descriptive-types
17422 @item maintenance ada set ignore-descriptive-types [on|off]
17423 Control whether the debugger should ignore descriptive types.
17424 The default is not to ignore descriptives types (@code{off}).
17426 @kindex maint ada show ignore-descriptive-types
17427 @item maintenance ada show ignore-descriptive-types
17428 Show if descriptive types are ignored by @value{GDBN}.
17432 @node Unsupported Languages
17433 @section Unsupported Languages
17435 @cindex unsupported languages
17436 @cindex minimal language
17437 In addition to the other fully-supported programming languages,
17438 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17439 It does not represent a real programming language, but provides a set
17440 of capabilities close to what the C or assembly languages provide.
17441 This should allow most simple operations to be performed while debugging
17442 an application that uses a language currently not supported by @value{GDBN}.
17444 If the language is set to @code{auto}, @value{GDBN} will automatically
17445 select this language if the current frame corresponds to an unsupported
17449 @chapter Examining the Symbol Table
17451 The commands described in this chapter allow you to inquire about the
17452 symbols (names of variables, functions and types) defined in your
17453 program. This information is inherent in the text of your program and
17454 does not change as your program executes. @value{GDBN} finds it in your
17455 program's symbol table, in the file indicated when you started @value{GDBN}
17456 (@pxref{File Options, ,Choosing Files}), or by one of the
17457 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17459 @cindex symbol names
17460 @cindex names of symbols
17461 @cindex quoting names
17462 @anchor{quoting names}
17463 Occasionally, you may need to refer to symbols that contain unusual
17464 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17465 most frequent case is in referring to static variables in other
17466 source files (@pxref{Variables,,Program Variables}). File names
17467 are recorded in object files as debugging symbols, but @value{GDBN} would
17468 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17469 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17470 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17477 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17480 @cindex case-insensitive symbol names
17481 @cindex case sensitivity in symbol names
17482 @kindex set case-sensitive
17483 @item set case-sensitive on
17484 @itemx set case-sensitive off
17485 @itemx set case-sensitive auto
17486 Normally, when @value{GDBN} looks up symbols, it matches their names
17487 with case sensitivity determined by the current source language.
17488 Occasionally, you may wish to control that. The command @code{set
17489 case-sensitive} lets you do that by specifying @code{on} for
17490 case-sensitive matches or @code{off} for case-insensitive ones. If
17491 you specify @code{auto}, case sensitivity is reset to the default
17492 suitable for the source language. The default is case-sensitive
17493 matches for all languages except for Fortran, for which the default is
17494 case-insensitive matches.
17496 @kindex show case-sensitive
17497 @item show case-sensitive
17498 This command shows the current setting of case sensitivity for symbols
17501 @kindex set print type methods
17502 @item set print type methods
17503 @itemx set print type methods on
17504 @itemx set print type methods off
17505 Normally, when @value{GDBN} prints a class, it displays any methods
17506 declared in that class. You can control this behavior either by
17507 passing the appropriate flag to @code{ptype}, or using @command{set
17508 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17509 display the methods; this is the default. Specifying @code{off} will
17510 cause @value{GDBN} to omit the methods.
17512 @kindex show print type methods
17513 @item show print type methods
17514 This command shows the current setting of method display when printing
17517 @kindex set print type nested-type-limit
17518 @item set print type nested-type-limit @var{limit}
17519 @itemx set print type nested-type-limit unlimited
17520 Set the limit of displayed nested types that the type printer will
17521 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17522 nested definitions. By default, the type printer will not show any nested
17523 types defined in classes.
17525 @kindex show print type nested-type-limit
17526 @item show print type nested-type-limit
17527 This command shows the current display limit of nested types when
17530 @kindex set print type typedefs
17531 @item set print type typedefs
17532 @itemx set print type typedefs on
17533 @itemx set print type typedefs off
17535 Normally, when @value{GDBN} prints a class, it displays any typedefs
17536 defined in that class. You can control this behavior either by
17537 passing the appropriate flag to @code{ptype}, or using @command{set
17538 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17539 display the typedef definitions; this is the default. Specifying
17540 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17541 Note that this controls whether the typedef definition itself is
17542 printed, not whether typedef names are substituted when printing other
17545 @kindex show print type typedefs
17546 @item show print type typedefs
17547 This command shows the current setting of typedef display when
17550 @kindex info address
17551 @cindex address of a symbol
17552 @item info address @var{symbol}
17553 Describe where the data for @var{symbol} is stored. For a register
17554 variable, this says which register it is kept in. For a non-register
17555 local variable, this prints the stack-frame offset at which the variable
17558 Note the contrast with @samp{print &@var{symbol}}, which does not work
17559 at all for a register variable, and for a stack local variable prints
17560 the exact address of the current instantiation of the variable.
17562 @kindex info symbol
17563 @cindex symbol from address
17564 @cindex closest symbol and offset for an address
17565 @item info symbol @var{addr}
17566 Print the name of a symbol which is stored at the address @var{addr}.
17567 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17568 nearest symbol and an offset from it:
17571 (@value{GDBP}) info symbol 0x54320
17572 _initialize_vx + 396 in section .text
17576 This is the opposite of the @code{info address} command. You can use
17577 it to find out the name of a variable or a function given its address.
17579 For dynamically linked executables, the name of executable or shared
17580 library containing the symbol is also printed:
17583 (@value{GDBP}) info symbol 0x400225
17584 _start + 5 in section .text of /tmp/a.out
17585 (@value{GDBP}) info symbol 0x2aaaac2811cf
17586 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17591 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17592 Demangle @var{name}.
17593 If @var{language} is provided it is the name of the language to demangle
17594 @var{name} in. Otherwise @var{name} is demangled in the current language.
17596 The @samp{--} option specifies the end of options,
17597 and is useful when @var{name} begins with a dash.
17599 The parameter @code{demangle-style} specifies how to interpret the kind
17600 of mangling used. @xref{Print Settings}.
17603 @item whatis[/@var{flags}] [@var{arg}]
17604 Print the data type of @var{arg}, which can be either an expression
17605 or a name of a data type. With no argument, print the data type of
17606 @code{$}, the last value in the value history.
17608 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17609 is not actually evaluated, and any side-effecting operations (such as
17610 assignments or function calls) inside it do not take place.
17612 If @var{arg} is a variable or an expression, @code{whatis} prints its
17613 literal type as it is used in the source code. If the type was
17614 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17615 the data type underlying the @code{typedef}. If the type of the
17616 variable or the expression is a compound data type, such as
17617 @code{struct} or @code{class}, @code{whatis} never prints their
17618 fields or methods. It just prints the @code{struct}/@code{class}
17619 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17620 such a compound data type, use @code{ptype}.
17622 If @var{arg} is a type name that was defined using @code{typedef},
17623 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17624 Unrolling means that @code{whatis} will show the underlying type used
17625 in the @code{typedef} declaration of @var{arg}. However, if that
17626 underlying type is also a @code{typedef}, @code{whatis} will not
17629 For C code, the type names may also have the form @samp{class
17630 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17631 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17633 @var{flags} can be used to modify how the type is displayed.
17634 Available flags are:
17638 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17639 parameters and typedefs defined in a class when printing the class'
17640 members. The @code{/r} flag disables this.
17643 Do not print methods defined in the class.
17646 Print methods defined in the class. This is the default, but the flag
17647 exists in case you change the default with @command{set print type methods}.
17650 Do not print typedefs defined in the class. Note that this controls
17651 whether the typedef definition itself is printed, not whether typedef
17652 names are substituted when printing other types.
17655 Print typedefs defined in the class. This is the default, but the flag
17656 exists in case you change the default with @command{set print type typedefs}.
17659 Print the offsets and sizes of fields in a struct, similar to what the
17660 @command{pahole} tool does. This option implies the @code{/tm} flags.
17662 For example, given the following declarations:
17698 Issuing a @kbd{ptype /o struct tuv} command would print:
17701 (@value{GDBP}) ptype /o struct tuv
17702 /* offset | size */ type = struct tuv @{
17703 /* 0 | 4 */ int a1;
17704 /* XXX 4-byte hole */
17705 /* 8 | 8 */ char *a2;
17706 /* 16 | 4 */ int a3;
17708 /* total size (bytes): 24 */
17712 Notice the format of the first column of comments. There, you can
17713 find two parts separated by the @samp{|} character: the @emph{offset},
17714 which indicates where the field is located inside the struct, in
17715 bytes, and the @emph{size} of the field. Another interesting line is
17716 the marker of a @emph{hole} in the struct, indicating that it may be
17717 possible to pack the struct and make it use less space by reorganizing
17720 It is also possible to print offsets inside an union:
17723 (@value{GDBP}) ptype /o union qwe
17724 /* offset | size */ type = union qwe @{
17725 /* 24 */ struct tuv @{
17726 /* 0 | 4 */ int a1;
17727 /* XXX 4-byte hole */
17728 /* 8 | 8 */ char *a2;
17729 /* 16 | 4 */ int a3;
17731 /* total size (bytes): 24 */
17733 /* 40 */ struct xyz @{
17734 /* 0 | 4 */ int f1;
17735 /* 4 | 1 */ char f2;
17736 /* XXX 3-byte hole */
17737 /* 8 | 8 */ void *f3;
17738 /* 16 | 24 */ struct tuv @{
17739 /* 16 | 4 */ int a1;
17740 /* XXX 4-byte hole */
17741 /* 24 | 8 */ char *a2;
17742 /* 32 | 4 */ int a3;
17744 /* total size (bytes): 24 */
17747 /* total size (bytes): 40 */
17750 /* total size (bytes): 40 */
17754 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17755 same space (because we are dealing with an union), the offset is not
17756 printed for them. However, you can still examine the offset of each
17757 of these structures' fields.
17759 Another useful scenario is printing the offsets of a struct containing
17763 (@value{GDBP}) ptype /o struct tyu
17764 /* offset | size */ type = struct tyu @{
17765 /* 0:31 | 4 */ int a1 : 1;
17766 /* 0:28 | 4 */ int a2 : 3;
17767 /* 0: 5 | 4 */ int a3 : 23;
17768 /* 3: 3 | 1 */ signed char a4 : 2;
17769 /* XXX 3-bit hole */
17770 /* XXX 4-byte hole */
17771 /* 8 | 8 */ int64_t a5;
17772 /* 16:27 | 4 */ int a6 : 5;
17773 /* 16:56 | 8 */ int64_t a7 : 3;
17775 /* total size (bytes): 24 */
17779 Note how the offset information is now extended to also include how
17780 many bits are left to be used in each bitfield.
17784 @item ptype[/@var{flags}] [@var{arg}]
17785 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17786 detailed description of the type, instead of just the name of the type.
17787 @xref{Expressions, ,Expressions}.
17789 Contrary to @code{whatis}, @code{ptype} always unrolls any
17790 @code{typedef}s in its argument declaration, whether the argument is
17791 a variable, expression, or a data type. This means that @code{ptype}
17792 of a variable or an expression will not print literally its type as
17793 present in the source code---use @code{whatis} for that. @code{typedef}s at
17794 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17795 fields, methods and inner @code{class typedef}s of @code{struct}s,
17796 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17798 For example, for this variable declaration:
17801 typedef double real_t;
17802 struct complex @{ real_t real; double imag; @};
17803 typedef struct complex complex_t;
17805 real_t *real_pointer_var;
17809 the two commands give this output:
17813 (@value{GDBP}) whatis var
17815 (@value{GDBP}) ptype var
17816 type = struct complex @{
17820 (@value{GDBP}) whatis complex_t
17821 type = struct complex
17822 (@value{GDBP}) whatis struct complex
17823 type = struct complex
17824 (@value{GDBP}) ptype struct complex
17825 type = struct complex @{
17829 (@value{GDBP}) whatis real_pointer_var
17831 (@value{GDBP}) ptype real_pointer_var
17837 As with @code{whatis}, using @code{ptype} without an argument refers to
17838 the type of @code{$}, the last value in the value history.
17840 @cindex incomplete type
17841 Sometimes, programs use opaque data types or incomplete specifications
17842 of complex data structure. If the debug information included in the
17843 program does not allow @value{GDBN} to display a full declaration of
17844 the data type, it will say @samp{<incomplete type>}. For example,
17845 given these declarations:
17849 struct foo *fooptr;
17853 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17856 (@value{GDBP}) ptype foo
17857 $1 = <incomplete type>
17861 ``Incomplete type'' is C terminology for data types that are not
17862 completely specified.
17864 @cindex unknown type
17865 Othertimes, information about a variable's type is completely absent
17866 from the debug information included in the program. This most often
17867 happens when the program or library where the variable is defined
17868 includes no debug information at all. @value{GDBN} knows the variable
17869 exists from inspecting the linker/loader symbol table (e.g., the ELF
17870 dynamic symbol table), but such symbols do not contain type
17871 information. Inspecting the type of a (global) variable for which
17872 @value{GDBN} has no type information shows:
17875 (@value{GDBP}) ptype var
17876 type = <data variable, no debug info>
17879 @xref{Variables, no debug info variables}, for how to print the values
17883 @item info types @var{regexp}
17885 Print a brief description of all types whose names match the regular
17886 expression @var{regexp} (or all types in your program, if you supply
17887 no argument). Each complete typename is matched as though it were a
17888 complete line; thus, @samp{i type value} gives information on all
17889 types in your program whose names include the string @code{value}, but
17890 @samp{i type ^value$} gives information only on types whose complete
17891 name is @code{value}.
17893 In programs using different languages, @value{GDBN} chooses the syntax
17894 to print the type description according to the
17895 @samp{set language} value: using @samp{set language auto}
17896 (see @ref{Automatically, ,Set Language Automatically}) means to use the
17897 language of the type, other values mean to use
17898 the manually specified language (see @ref{Manually, ,Set Language Manually}).
17900 This command differs from @code{ptype} in two ways: first, like
17901 @code{whatis}, it does not print a detailed description; second, it
17902 lists all source files and line numbers where a type is defined.
17904 @kindex info type-printers
17905 @item info type-printers
17906 Versions of @value{GDBN} that ship with Python scripting enabled may
17907 have ``type printers'' available. When using @command{ptype} or
17908 @command{whatis}, these printers are consulted when the name of a type
17909 is needed. @xref{Type Printing API}, for more information on writing
17912 @code{info type-printers} displays all the available type printers.
17914 @kindex enable type-printer
17915 @kindex disable type-printer
17916 @item enable type-printer @var{name}@dots{}
17917 @item disable type-printer @var{name}@dots{}
17918 These commands can be used to enable or disable type printers.
17921 @cindex local variables
17922 @item info scope @var{location}
17923 List all the variables local to a particular scope. This command
17924 accepts a @var{location} argument---a function name, a source line, or
17925 an address preceded by a @samp{*}, and prints all the variables local
17926 to the scope defined by that location. (@xref{Specify Location}, for
17927 details about supported forms of @var{location}.) For example:
17930 (@value{GDBP}) @b{info scope command_line_handler}
17931 Scope for command_line_handler:
17932 Symbol rl is an argument at stack/frame offset 8, length 4.
17933 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17934 Symbol linelength is in static storage at address 0x150a1c, length 4.
17935 Symbol p is a local variable in register $esi, length 4.
17936 Symbol p1 is a local variable in register $ebx, length 4.
17937 Symbol nline is a local variable in register $edx, length 4.
17938 Symbol repeat is a local variable at frame offset -8, length 4.
17942 This command is especially useful for determining what data to collect
17943 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17946 @kindex info source
17948 Show information about the current source file---that is, the source file for
17949 the function containing the current point of execution:
17952 the name of the source file, and the directory containing it,
17954 the directory it was compiled in,
17956 its length, in lines,
17958 which programming language it is written in,
17960 if the debug information provides it, the program that compiled the file
17961 (which may include, e.g., the compiler version and command line arguments),
17963 whether the executable includes debugging information for that file, and
17964 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17966 whether the debugging information includes information about
17967 preprocessor macros.
17971 @kindex info sources
17973 Print the names of all source files in your program for which there is
17974 debugging information, organized into two lists: files whose symbols
17975 have already been read, and files whose symbols will be read when needed.
17977 @kindex info functions
17978 @item info functions [-q]
17979 Print the names and data types of all defined functions.
17980 Similarly to @samp{info types}, this command groups its output by source
17981 files and annotates each function definition with its source line
17984 In programs using different languages, @value{GDBN} chooses the syntax
17985 to print the function name and type according to the
17986 @samp{set language} value: using @samp{set language auto}
17987 (see @ref{Automatically, ,Set Language Automatically}) means to use the
17988 language of the function, other values mean to use
17989 the manually specified language (see @ref{Manually, ,Set Language Manually}).
17991 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
17992 printing header information and messages explaining why no functions
17995 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
17996 Like @samp{info functions}, but only print the names and data types
17997 of the functions selected with the provided regexp(s).
17999 If @var{regexp} is provided, print only the functions whose names
18000 match the regular expression @var{regexp}.
18001 Thus, @samp{info fun step} finds all functions whose
18002 names include @code{step}; @samp{info fun ^step} finds those whose names
18003 start with @code{step}. If a function name contains characters that
18004 conflict with the regular expression language (e.g.@:
18005 @samp{operator*()}), they may be quoted with a backslash.
18007 If @var{type_regexp} is provided, print only the functions whose
18008 types, as printed by the @code{whatis} command, match
18009 the regular expression @var{type_regexp}.
18010 If @var{type_regexp} contains space(s), it should be enclosed in
18011 quote characters. If needed, use backslash to escape the meaning
18012 of special characters or quotes.
18013 Thus, @samp{info fun -t '^int ('} finds the functions that return
18014 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18015 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18016 finds the functions whose names start with @code{step} and that return
18019 If both @var{regexp} and @var{type_regexp} are provided, a function
18020 is printed only if its name matches @var{regexp} and its type matches
18024 @kindex info variables
18025 @item info variables [-q]
18026 Print the names and data types of all variables that are defined
18027 outside of functions (i.e.@: excluding local variables).
18028 The printed variables are grouped by source files and annotated with
18029 their respective source line numbers.
18031 In programs using different languages, @value{GDBN} chooses the syntax
18032 to print the variable name and type according to the
18033 @samp{set language} value: using @samp{set language auto}
18034 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18035 language of the variable, other values mean to use
18036 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18038 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18039 printing header information and messages explaining why no variables
18042 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18043 Like @kbd{info variables}, but only print the variables selected
18044 with the provided regexp(s).
18046 If @var{regexp} is provided, print only the variables whose names
18047 match the regular expression @var{regexp}.
18049 If @var{type_regexp} is provided, print only the variables whose
18050 types, as printed by the @code{whatis} command, match
18051 the regular expression @var{type_regexp}.
18052 If @var{type_regexp} contains space(s), it should be enclosed in
18053 quote characters. If needed, use backslash to escape the meaning
18054 of special characters or quotes.
18056 If both @var{regexp} and @var{type_regexp} are provided, an argument
18057 is printed only if its name matches @var{regexp} and its type matches
18060 @kindex info classes
18061 @cindex Objective-C, classes and selectors
18063 @itemx info classes @var{regexp}
18064 Display all Objective-C classes in your program, or
18065 (with the @var{regexp} argument) all those matching a particular regular
18068 @kindex info selectors
18069 @item info selectors
18070 @itemx info selectors @var{regexp}
18071 Display all Objective-C selectors in your program, or
18072 (with the @var{regexp} argument) all those matching a particular regular
18076 This was never implemented.
18077 @kindex info methods
18079 @itemx info methods @var{regexp}
18080 The @code{info methods} command permits the user to examine all defined
18081 methods within C@t{++} program, or (with the @var{regexp} argument) a
18082 specific set of methods found in the various C@t{++} classes. Many
18083 C@t{++} classes provide a large number of methods. Thus, the output
18084 from the @code{ptype} command can be overwhelming and hard to use. The
18085 @code{info-methods} command filters the methods, printing only those
18086 which match the regular-expression @var{regexp}.
18089 @cindex opaque data types
18090 @kindex set opaque-type-resolution
18091 @item set opaque-type-resolution on
18092 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18093 declared as a pointer to a @code{struct}, @code{class}, or
18094 @code{union}---for example, @code{struct MyType *}---that is used in one
18095 source file although the full declaration of @code{struct MyType} is in
18096 another source file. The default is on.
18098 A change in the setting of this subcommand will not take effect until
18099 the next time symbols for a file are loaded.
18101 @item set opaque-type-resolution off
18102 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18103 is printed as follows:
18105 @{<no data fields>@}
18108 @kindex show opaque-type-resolution
18109 @item show opaque-type-resolution
18110 Show whether opaque types are resolved or not.
18112 @kindex set print symbol-loading
18113 @cindex print messages when symbols are loaded
18114 @item set print symbol-loading
18115 @itemx set print symbol-loading full
18116 @itemx set print symbol-loading brief
18117 @itemx set print symbol-loading off
18118 The @code{set print symbol-loading} command allows you to control the
18119 printing of messages when @value{GDBN} loads symbol information.
18120 By default a message is printed for the executable and one for each
18121 shared library, and normally this is what you want. However, when
18122 debugging apps with large numbers of shared libraries these messages
18124 When set to @code{brief} a message is printed for each executable,
18125 and when @value{GDBN} loads a collection of shared libraries at once
18126 it will only print one message regardless of the number of shared
18127 libraries. When set to @code{off} no messages are printed.
18129 @kindex show print symbol-loading
18130 @item show print symbol-loading
18131 Show whether messages will be printed when a @value{GDBN} command
18132 entered from the keyboard causes symbol information to be loaded.
18134 @kindex maint print symbols
18135 @cindex symbol dump
18136 @kindex maint print psymbols
18137 @cindex partial symbol dump
18138 @kindex maint print msymbols
18139 @cindex minimal symbol dump
18140 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18141 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18142 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18143 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18144 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18145 Write a dump of debugging symbol data into the file @var{filename} or
18146 the terminal if @var{filename} is unspecified.
18147 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18149 If @code{-pc @var{address}} is specified, only dump symbols for the file
18150 with code at that address. Note that @var{address} may be a symbol like
18152 If @code{-source @var{source}} is specified, only dump symbols for that
18155 These commands are used to debug the @value{GDBN} symbol-reading code.
18156 These commands do not modify internal @value{GDBN} state, therefore
18157 @samp{maint print symbols} will only print symbols for already expanded symbol
18159 You can use the command @code{info sources} to find out which files these are.
18160 If you use @samp{maint print psymbols} instead, the dump shows information
18161 about symbols that @value{GDBN} only knows partially---that is, symbols
18162 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18163 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18166 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18167 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18169 @kindex maint info symtabs
18170 @kindex maint info psymtabs
18171 @cindex listing @value{GDBN}'s internal symbol tables
18172 @cindex symbol tables, listing @value{GDBN}'s internal
18173 @cindex full symbol tables, listing @value{GDBN}'s internal
18174 @cindex partial symbol tables, listing @value{GDBN}'s internal
18175 @item maint info symtabs @r{[} @var{regexp} @r{]}
18176 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18178 List the @code{struct symtab} or @code{struct partial_symtab}
18179 structures whose names match @var{regexp}. If @var{regexp} is not
18180 given, list them all. The output includes expressions which you can
18181 copy into a @value{GDBN} debugging this one to examine a particular
18182 structure in more detail. For example:
18185 (@value{GDBP}) maint info psymtabs dwarf2read
18186 @{ objfile /home/gnu/build/gdb/gdb
18187 ((struct objfile *) 0x82e69d0)
18188 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18189 ((struct partial_symtab *) 0x8474b10)
18192 text addresses 0x814d3c8 -- 0x8158074
18193 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18194 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18195 dependencies (none)
18198 (@value{GDBP}) maint info symtabs
18202 We see that there is one partial symbol table whose filename contains
18203 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18204 and we see that @value{GDBN} has not read in any symtabs yet at all.
18205 If we set a breakpoint on a function, that will cause @value{GDBN} to
18206 read the symtab for the compilation unit containing that function:
18209 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18210 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18212 (@value{GDBP}) maint info symtabs
18213 @{ objfile /home/gnu/build/gdb/gdb
18214 ((struct objfile *) 0x82e69d0)
18215 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18216 ((struct symtab *) 0x86c1f38)
18219 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18220 linetable ((struct linetable *) 0x8370fa0)
18221 debugformat DWARF 2
18227 @kindex maint info line-table
18228 @cindex listing @value{GDBN}'s internal line tables
18229 @cindex line tables, listing @value{GDBN}'s internal
18230 @item maint info line-table @r{[} @var{regexp} @r{]}
18232 List the @code{struct linetable} from all @code{struct symtab}
18233 instances whose name matches @var{regexp}. If @var{regexp} is not
18234 given, list the @code{struct linetable} from all @code{struct symtab}.
18236 @kindex maint set symbol-cache-size
18237 @cindex symbol cache size
18238 @item maint set symbol-cache-size @var{size}
18239 Set the size of the symbol cache to @var{size}.
18240 The default size is intended to be good enough for debugging
18241 most applications. This option exists to allow for experimenting
18242 with different sizes.
18244 @kindex maint show symbol-cache-size
18245 @item maint show symbol-cache-size
18246 Show the size of the symbol cache.
18248 @kindex maint print symbol-cache
18249 @cindex symbol cache, printing its contents
18250 @item maint print symbol-cache
18251 Print the contents of the symbol cache.
18252 This is useful when debugging symbol cache issues.
18254 @kindex maint print symbol-cache-statistics
18255 @cindex symbol cache, printing usage statistics
18256 @item maint print symbol-cache-statistics
18257 Print symbol cache usage statistics.
18258 This helps determine how well the cache is being utilized.
18260 @kindex maint flush-symbol-cache
18261 @cindex symbol cache, flushing
18262 @item maint flush-symbol-cache
18263 Flush the contents of the symbol cache, all entries are removed.
18264 This command is useful when debugging the symbol cache.
18265 It is also useful when collecting performance data.
18270 @chapter Altering Execution
18272 Once you think you have found an error in your program, you might want to
18273 find out for certain whether correcting the apparent error would lead to
18274 correct results in the rest of the run. You can find the answer by
18275 experiment, using the @value{GDBN} features for altering execution of the
18278 For example, you can store new values into variables or memory
18279 locations, give your program a signal, restart it at a different
18280 address, or even return prematurely from a function.
18283 * Assignment:: Assignment to variables
18284 * Jumping:: Continuing at a different address
18285 * Signaling:: Giving your program a signal
18286 * Returning:: Returning from a function
18287 * Calling:: Calling your program's functions
18288 * Patching:: Patching your program
18289 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18293 @section Assignment to Variables
18296 @cindex setting variables
18297 To alter the value of a variable, evaluate an assignment expression.
18298 @xref{Expressions, ,Expressions}. For example,
18305 stores the value 4 into the variable @code{x}, and then prints the
18306 value of the assignment expression (which is 4).
18307 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18308 information on operators in supported languages.
18310 @kindex set variable
18311 @cindex variables, setting
18312 If you are not interested in seeing the value of the assignment, use the
18313 @code{set} command instead of the @code{print} command. @code{set} is
18314 really the same as @code{print} except that the expression's value is
18315 not printed and is not put in the value history (@pxref{Value History,
18316 ,Value History}). The expression is evaluated only for its effects.
18318 If the beginning of the argument string of the @code{set} command
18319 appears identical to a @code{set} subcommand, use the @code{set
18320 variable} command instead of just @code{set}. This command is identical
18321 to @code{set} except for its lack of subcommands. For example, if your
18322 program has a variable @code{width}, you get an error if you try to set
18323 a new value with just @samp{set width=13}, because @value{GDBN} has the
18324 command @code{set width}:
18327 (@value{GDBP}) whatis width
18329 (@value{GDBP}) p width
18331 (@value{GDBP}) set width=47
18332 Invalid syntax in expression.
18336 The invalid expression, of course, is @samp{=47}. In
18337 order to actually set the program's variable @code{width}, use
18340 (@value{GDBP}) set var width=47
18343 Because the @code{set} command has many subcommands that can conflict
18344 with the names of program variables, it is a good idea to use the
18345 @code{set variable} command instead of just @code{set}. For example, if
18346 your program has a variable @code{g}, you run into problems if you try
18347 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18348 the command @code{set gnutarget}, abbreviated @code{set g}:
18352 (@value{GDBP}) whatis g
18356 (@value{GDBP}) set g=4
18360 The program being debugged has been started already.
18361 Start it from the beginning? (y or n) y
18362 Starting program: /home/smith/cc_progs/a.out
18363 "/home/smith/cc_progs/a.out": can't open to read symbols:
18364 Invalid bfd target.
18365 (@value{GDBP}) show g
18366 The current BFD target is "=4".
18371 The program variable @code{g} did not change, and you silently set the
18372 @code{gnutarget} to an invalid value. In order to set the variable
18376 (@value{GDBP}) set var g=4
18379 @value{GDBN} allows more implicit conversions in assignments than C; you can
18380 freely store an integer value into a pointer variable or vice versa,
18381 and you can convert any structure to any other structure that is the
18382 same length or shorter.
18383 @comment FIXME: how do structs align/pad in these conversions?
18384 @comment /doc@cygnus.com 18dec1990
18386 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18387 construct to generate a value of specified type at a specified address
18388 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18389 to memory location @code{0x83040} as an integer (which implies a certain size
18390 and representation in memory), and
18393 set @{int@}0x83040 = 4
18397 stores the value 4 into that memory location.
18400 @section Continuing at a Different Address
18402 Ordinarily, when you continue your program, you do so at the place where
18403 it stopped, with the @code{continue} command. You can instead continue at
18404 an address of your own choosing, with the following commands:
18408 @kindex j @r{(@code{jump})}
18409 @item jump @var{location}
18410 @itemx j @var{location}
18411 Resume execution at @var{location}. Execution stops again immediately
18412 if there is a breakpoint there. @xref{Specify Location}, for a description
18413 of the different forms of @var{location}. It is common
18414 practice to use the @code{tbreak} command in conjunction with
18415 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18417 The @code{jump} command does not change the current stack frame, or
18418 the stack pointer, or the contents of any memory location or any
18419 register other than the program counter. If @var{location} is in
18420 a different function from the one currently executing, the results may
18421 be bizarre if the two functions expect different patterns of arguments or
18422 of local variables. For this reason, the @code{jump} command requests
18423 confirmation if the specified line is not in the function currently
18424 executing. However, even bizarre results are predictable if you are
18425 well acquainted with the machine-language code of your program.
18428 On many systems, you can get much the same effect as the @code{jump}
18429 command by storing a new value into the register @code{$pc}. The
18430 difference is that this does not start your program running; it only
18431 changes the address of where it @emph{will} run when you continue. For
18439 makes the next @code{continue} command or stepping command execute at
18440 address @code{0x485}, rather than at the address where your program stopped.
18441 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18443 The most common occasion to use the @code{jump} command is to back
18444 up---perhaps with more breakpoints set---over a portion of a program
18445 that has already executed, in order to examine its execution in more
18450 @section Giving your Program a Signal
18451 @cindex deliver a signal to a program
18455 @item signal @var{signal}
18456 Resume execution where your program is stopped, but immediately give it the
18457 signal @var{signal}. The @var{signal} can be the name or the number of a
18458 signal. For example, on many systems @code{signal 2} and @code{signal
18459 SIGINT} are both ways of sending an interrupt signal.
18461 Alternatively, if @var{signal} is zero, continue execution without
18462 giving a signal. This is useful when your program stopped on account of
18463 a signal and would ordinarily see the signal when resumed with the
18464 @code{continue} command; @samp{signal 0} causes it to resume without a
18467 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18468 delivered to the currently selected thread, not the thread that last
18469 reported a stop. This includes the situation where a thread was
18470 stopped due to a signal. So if you want to continue execution
18471 suppressing the signal that stopped a thread, you should select that
18472 same thread before issuing the @samp{signal 0} command. If you issue
18473 the @samp{signal 0} command with another thread as the selected one,
18474 @value{GDBN} detects that and asks for confirmation.
18476 Invoking the @code{signal} command is not the same as invoking the
18477 @code{kill} utility from the shell. Sending a signal with @code{kill}
18478 causes @value{GDBN} to decide what to do with the signal depending on
18479 the signal handling tables (@pxref{Signals}). The @code{signal} command
18480 passes the signal directly to your program.
18482 @code{signal} does not repeat when you press @key{RET} a second time
18483 after executing the command.
18485 @kindex queue-signal
18486 @item queue-signal @var{signal}
18487 Queue @var{signal} to be delivered immediately to the current thread
18488 when execution of the thread resumes. The @var{signal} can be the name or
18489 the number of a signal. For example, on many systems @code{signal 2} and
18490 @code{signal SIGINT} are both ways of sending an interrupt signal.
18491 The handling of the signal must be set to pass the signal to the program,
18492 otherwise @value{GDBN} will report an error.
18493 You can control the handling of signals from @value{GDBN} with the
18494 @code{handle} command (@pxref{Signals}).
18496 Alternatively, if @var{signal} is zero, any currently queued signal
18497 for the current thread is discarded and when execution resumes no signal
18498 will be delivered. This is useful when your program stopped on account
18499 of a signal and would ordinarily see the signal when resumed with the
18500 @code{continue} command.
18502 This command differs from the @code{signal} command in that the signal
18503 is just queued, execution is not resumed. And @code{queue-signal} cannot
18504 be used to pass a signal whose handling state has been set to @code{nopass}
18509 @xref{stepping into signal handlers}, for information on how stepping
18510 commands behave when the thread has a signal queued.
18513 @section Returning from a Function
18516 @cindex returning from a function
18519 @itemx return @var{expression}
18520 You can cancel execution of a function call with the @code{return}
18521 command. If you give an
18522 @var{expression} argument, its value is used as the function's return
18526 When you use @code{return}, @value{GDBN} discards the selected stack frame
18527 (and all frames within it). You can think of this as making the
18528 discarded frame return prematurely. If you wish to specify a value to
18529 be returned, give that value as the argument to @code{return}.
18531 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18532 Frame}), and any other frames inside of it, leaving its caller as the
18533 innermost remaining frame. That frame becomes selected. The
18534 specified value is stored in the registers used for returning values
18537 The @code{return} command does not resume execution; it leaves the
18538 program stopped in the state that would exist if the function had just
18539 returned. In contrast, the @code{finish} command (@pxref{Continuing
18540 and Stepping, ,Continuing and Stepping}) resumes execution until the
18541 selected stack frame returns naturally.
18543 @value{GDBN} needs to know how the @var{expression} argument should be set for
18544 the inferior. The concrete registers assignment depends on the OS ABI and the
18545 type being returned by the selected stack frame. For example it is common for
18546 OS ABI to return floating point values in FPU registers while integer values in
18547 CPU registers. Still some ABIs return even floating point values in CPU
18548 registers. Larger integer widths (such as @code{long long int}) also have
18549 specific placement rules. @value{GDBN} already knows the OS ABI from its
18550 current target so it needs to find out also the type being returned to make the
18551 assignment into the right register(s).
18553 Normally, the selected stack frame has debug info. @value{GDBN} will always
18554 use the debug info instead of the implicit type of @var{expression} when the
18555 debug info is available. For example, if you type @kbd{return -1}, and the
18556 function in the current stack frame is declared to return a @code{long long
18557 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18558 into a @code{long long int}:
18561 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18563 (@value{GDBP}) return -1
18564 Make func return now? (y or n) y
18565 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18566 43 printf ("result=%lld\n", func ());
18570 However, if the selected stack frame does not have a debug info, e.g., if the
18571 function was compiled without debug info, @value{GDBN} has to find out the type
18572 to return from user. Specifying a different type by mistake may set the value
18573 in different inferior registers than the caller code expects. For example,
18574 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18575 of a @code{long long int} result for a debug info less function (on 32-bit
18576 architectures). Therefore the user is required to specify the return type by
18577 an appropriate cast explicitly:
18580 Breakpoint 2, 0x0040050b in func ()
18581 (@value{GDBP}) return -1
18582 Return value type not available for selected stack frame.
18583 Please use an explicit cast of the value to return.
18584 (@value{GDBP}) return (long long int) -1
18585 Make selected stack frame return now? (y or n) y
18586 #0 0x00400526 in main ()
18591 @section Calling Program Functions
18594 @cindex calling functions
18595 @cindex inferior functions, calling
18596 @item print @var{expr}
18597 Evaluate the expression @var{expr} and display the resulting value.
18598 The expression may include calls to functions in the program being
18602 @item call @var{expr}
18603 Evaluate the expression @var{expr} without displaying @code{void}
18606 You can use this variant of the @code{print} command if you want to
18607 execute a function from your program that does not return anything
18608 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18609 with @code{void} returned values that @value{GDBN} will otherwise
18610 print. If the result is not void, it is printed and saved in the
18614 It is possible for the function you call via the @code{print} or
18615 @code{call} command to generate a signal (e.g., if there's a bug in
18616 the function, or if you passed it incorrect arguments). What happens
18617 in that case is controlled by the @code{set unwindonsignal} command.
18619 Similarly, with a C@t{++} program it is possible for the function you
18620 call via the @code{print} or @code{call} command to generate an
18621 exception that is not handled due to the constraints of the dummy
18622 frame. In this case, any exception that is raised in the frame, but has
18623 an out-of-frame exception handler will not be found. GDB builds a
18624 dummy-frame for the inferior function call, and the unwinder cannot
18625 seek for exception handlers outside of this dummy-frame. What happens
18626 in that case is controlled by the
18627 @code{set unwind-on-terminating-exception} command.
18630 @item set unwindonsignal
18631 @kindex set unwindonsignal
18632 @cindex unwind stack in called functions
18633 @cindex call dummy stack unwinding
18634 Set unwinding of the stack if a signal is received while in a function
18635 that @value{GDBN} called in the program being debugged. If set to on,
18636 @value{GDBN} unwinds the stack it created for the call and restores
18637 the context to what it was before the call. If set to off (the
18638 default), @value{GDBN} stops in the frame where the signal was
18641 @item show unwindonsignal
18642 @kindex show unwindonsignal
18643 Show the current setting of stack unwinding in the functions called by
18646 @item set unwind-on-terminating-exception
18647 @kindex set unwind-on-terminating-exception
18648 @cindex unwind stack in called functions with unhandled exceptions
18649 @cindex call dummy stack unwinding on unhandled exception.
18650 Set unwinding of the stack if a C@t{++} exception is raised, but left
18651 unhandled while in a function that @value{GDBN} called in the program being
18652 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18653 it created for the call and restores the context to what it was before
18654 the call. If set to off, @value{GDBN} the exception is delivered to
18655 the default C@t{++} exception handler and the inferior terminated.
18657 @item show unwind-on-terminating-exception
18658 @kindex show unwind-on-terminating-exception
18659 Show the current setting of stack unwinding in the functions called by
18664 @subsection Calling functions with no debug info
18666 @cindex no debug info functions
18667 Sometimes, a function you wish to call is missing debug information.
18668 In such case, @value{GDBN} does not know the type of the function,
18669 including the types of the function's parameters. To avoid calling
18670 the inferior function incorrectly, which could result in the called
18671 function functioning erroneously and even crash, @value{GDBN} refuses
18672 to call the function unless you tell it the type of the function.
18674 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18675 to do that. The simplest is to cast the call to the function's
18676 declared return type. For example:
18679 (@value{GDBP}) p getenv ("PATH")
18680 'getenv' has unknown return type; cast the call to its declared return type
18681 (@value{GDBP}) p (char *) getenv ("PATH")
18682 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18685 Casting the return type of a no-debug function is equivalent to
18686 casting the function to a pointer to a prototyped function that has a
18687 prototype that matches the types of the passed-in arguments, and
18688 calling that. I.e., the call above is equivalent to:
18691 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18695 and given this prototyped C or C++ function with float parameters:
18698 float multiply (float v1, float v2) @{ return v1 * v2; @}
18702 these calls are equivalent:
18705 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18706 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18709 If the function you wish to call is declared as unprototyped (i.e.@:
18710 old K&R style), you must use the cast-to-function-pointer syntax, so
18711 that @value{GDBN} knows that it needs to apply default argument
18712 promotions (promote float arguments to double). @xref{ABI, float
18713 promotion}. For example, given this unprototyped C function with
18714 float parameters, and no debug info:
18718 multiply_noproto (v1, v2)
18726 you call it like this:
18729 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18733 @section Patching Programs
18735 @cindex patching binaries
18736 @cindex writing into executables
18737 @cindex writing into corefiles
18739 By default, @value{GDBN} opens the file containing your program's
18740 executable code (or the corefile) read-only. This prevents accidental
18741 alterations to machine code; but it also prevents you from intentionally
18742 patching your program's binary.
18744 If you'd like to be able to patch the binary, you can specify that
18745 explicitly with the @code{set write} command. For example, you might
18746 want to turn on internal debugging flags, or even to make emergency
18752 @itemx set write off
18753 If you specify @samp{set write on}, @value{GDBN} opens executable and
18754 core files for both reading and writing; if you specify @kbd{set write
18755 off} (the default), @value{GDBN} opens them read-only.
18757 If you have already loaded a file, you must load it again (using the
18758 @code{exec-file} or @code{core-file} command) after changing @code{set
18759 write}, for your new setting to take effect.
18763 Display whether executable files and core files are opened for writing
18764 as well as reading.
18767 @node Compiling and Injecting Code
18768 @section Compiling and injecting code in @value{GDBN}
18769 @cindex injecting code
18770 @cindex writing into executables
18771 @cindex compiling code
18773 @value{GDBN} supports on-demand compilation and code injection into
18774 programs running under @value{GDBN}. GCC 5.0 or higher built with
18775 @file{libcc1.so} must be installed for this functionality to be enabled.
18776 This functionality is implemented with the following commands.
18779 @kindex compile code
18780 @item compile code @var{source-code}
18781 @itemx compile code -raw @var{--} @var{source-code}
18782 Compile @var{source-code} with the compiler language found as the current
18783 language in @value{GDBN} (@pxref{Languages}). If compilation and
18784 injection is not supported with the current language specified in
18785 @value{GDBN}, or the compiler does not support this feature, an error
18786 message will be printed. If @var{source-code} compiles and links
18787 successfully, @value{GDBN} will load the object-code emitted,
18788 and execute it within the context of the currently selected inferior.
18789 It is important to note that the compiled code is executed immediately.
18790 After execution, the compiled code is removed from @value{GDBN} and any
18791 new types or variables you have defined will be deleted.
18793 The command allows you to specify @var{source-code} in two ways.
18794 The simplest method is to provide a single line of code to the command.
18798 compile code printf ("hello world\n");
18801 If you specify options on the command line as well as source code, they
18802 may conflict. The @samp{--} delimiter can be used to separate options
18803 from actual source code. E.g.:
18806 compile code -r -- printf ("hello world\n");
18809 Alternatively you can enter source code as multiple lines of text. To
18810 enter this mode, invoke the @samp{compile code} command without any text
18811 following the command. This will start the multiple-line editor and
18812 allow you to type as many lines of source code as required. When you
18813 have completed typing, enter @samp{end} on its own line to exit the
18818 >printf ("hello\n");
18819 >printf ("world\n");
18823 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18824 provided @var{source-code} in a callable scope. In this case, you must
18825 specify the entry point of the code by defining a function named
18826 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18827 inferior. Using @samp{-raw} option may be needed for example when
18828 @var{source-code} requires @samp{#include} lines which may conflict with
18829 inferior symbols otherwise.
18831 @kindex compile file
18832 @item compile file @var{filename}
18833 @itemx compile file -raw @var{filename}
18834 Like @code{compile code}, but take the source code from @var{filename}.
18837 compile file /home/user/example.c
18842 @item compile print @var{expr}
18843 @itemx compile print /@var{f} @var{expr}
18844 Compile and execute @var{expr} with the compiler language found as the
18845 current language in @value{GDBN} (@pxref{Languages}). By default the
18846 value of @var{expr} is printed in a format appropriate to its data type;
18847 you can choose a different format by specifying @samp{/@var{f}}, where
18848 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18851 @item compile print
18852 @itemx compile print /@var{f}
18853 @cindex reprint the last value
18854 Alternatively you can enter the expression (source code producing it) as
18855 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18856 command without any text following the command. This will start the
18857 multiple-line editor.
18861 The process of compiling and injecting the code can be inspected using:
18864 @anchor{set debug compile}
18865 @item set debug compile
18866 @cindex compile command debugging info
18867 Turns on or off display of @value{GDBN} process of compiling and
18868 injecting the code. The default is off.
18870 @item show debug compile
18871 Displays the current state of displaying @value{GDBN} process of
18872 compiling and injecting the code.
18874 @anchor{set debug compile-cplus-types}
18875 @item set debug compile-cplus-types
18876 @cindex compile C@t{++} type conversion
18877 Turns on or off the display of C@t{++} type conversion debugging information.
18878 The default is off.
18880 @item show debug compile-cplus-types
18881 Displays the current state of displaying debugging information for
18882 C@t{++} type conversion.
18885 @subsection Compilation options for the @code{compile} command
18887 @value{GDBN} needs to specify the right compilation options for the code
18888 to be injected, in part to make its ABI compatible with the inferior
18889 and in part to make the injected code compatible with @value{GDBN}'s
18893 The options used, in increasing precedence:
18896 @item target architecture and OS options (@code{gdbarch})
18897 These options depend on target processor type and target operating
18898 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18899 (@code{-m64}) compilation option.
18901 @item compilation options recorded in the target
18902 @value{NGCC} (since version 4.7) stores the options used for compilation
18903 into @code{DW_AT_producer} part of DWARF debugging information according
18904 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18905 explicitly specify @code{-g} during inferior compilation otherwise
18906 @value{NGCC} produces no DWARF. This feature is only relevant for
18907 platforms where @code{-g} produces DWARF by default, otherwise one may
18908 try to enforce DWARF by using @code{-gdwarf-4}.
18910 @item compilation options set by @code{set compile-args}
18914 You can override compilation options using the following command:
18917 @item set compile-args
18918 @cindex compile command options override
18919 Set compilation options used for compiling and injecting code with the
18920 @code{compile} commands. These options override any conflicting ones
18921 from the target architecture and/or options stored during inferior
18924 @item show compile-args
18925 Displays the current state of compilation options override.
18926 This does not show all the options actually used during compilation,
18927 use @ref{set debug compile} for that.
18930 @subsection Caveats when using the @code{compile} command
18932 There are a few caveats to keep in mind when using the @code{compile}
18933 command. As the caveats are different per language, the table below
18934 highlights specific issues on a per language basis.
18937 @item C code examples and caveats
18938 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18939 attempt to compile the source code with a @samp{C} compiler. The source
18940 code provided to the @code{compile} command will have much the same
18941 access to variables and types as it normally would if it were part of
18942 the program currently being debugged in @value{GDBN}.
18944 Below is a sample program that forms the basis of the examples that
18945 follow. This program has been compiled and loaded into @value{GDBN},
18946 much like any other normal debugging session.
18949 void function1 (void)
18952 printf ("function 1\n");
18955 void function2 (void)
18970 For the purposes of the examples in this section, the program above has
18971 been compiled, loaded into @value{GDBN}, stopped at the function
18972 @code{main}, and @value{GDBN} is awaiting input from the user.
18974 To access variables and types for any program in @value{GDBN}, the
18975 program must be compiled and packaged with debug information. The
18976 @code{compile} command is not an exception to this rule. Without debug
18977 information, you can still use the @code{compile} command, but you will
18978 be very limited in what variables and types you can access.
18980 So with that in mind, the example above has been compiled with debug
18981 information enabled. The @code{compile} command will have access to
18982 all variables and types (except those that may have been optimized
18983 out). Currently, as @value{GDBN} has stopped the program in the
18984 @code{main} function, the @code{compile} command would have access to
18985 the variable @code{k}. You could invoke the @code{compile} command
18986 and type some source code to set the value of @code{k}. You can also
18987 read it, or do anything with that variable you would normally do in
18988 @code{C}. Be aware that changes to inferior variables in the
18989 @code{compile} command are persistent. In the following example:
18992 compile code k = 3;
18996 the variable @code{k} is now 3. It will retain that value until
18997 something else in the example program changes it, or another
18998 @code{compile} command changes it.
19000 Normal scope and access rules apply to source code compiled and
19001 injected by the @code{compile} command. In the example, the variables
19002 @code{j} and @code{k} are not accessible yet, because the program is
19003 currently stopped in the @code{main} function, where these variables
19004 are not in scope. Therefore, the following command
19007 compile code j = 3;
19011 will result in a compilation error message.
19013 Once the program is continued, execution will bring these variables in
19014 scope, and they will become accessible; then the code you specify via
19015 the @code{compile} command will be able to access them.
19017 You can create variables and types with the @code{compile} command as
19018 part of your source code. Variables and types that are created as part
19019 of the @code{compile} command are not visible to the rest of the program for
19020 the duration of its run. This example is valid:
19023 compile code int ff = 5; printf ("ff is %d\n", ff);
19026 However, if you were to type the following into @value{GDBN} after that
19027 command has completed:
19030 compile code printf ("ff is %d\n'', ff);
19034 a compiler error would be raised as the variable @code{ff} no longer
19035 exists. Object code generated and injected by the @code{compile}
19036 command is removed when its execution ends. Caution is advised
19037 when assigning to program variables values of variables created by the
19038 code submitted to the @code{compile} command. This example is valid:
19041 compile code int ff = 5; k = ff;
19044 The value of the variable @code{ff} is assigned to @code{k}. The variable
19045 @code{k} does not require the existence of @code{ff} to maintain the value
19046 it has been assigned. However, pointers require particular care in
19047 assignment. If the source code compiled with the @code{compile} command
19048 changed the address of a pointer in the example program, perhaps to a
19049 variable created in the @code{compile} command, that pointer would point
19050 to an invalid location when the command exits. The following example
19051 would likely cause issues with your debugged program:
19054 compile code int ff = 5; p = &ff;
19057 In this example, @code{p} would point to @code{ff} when the
19058 @code{compile} command is executing the source code provided to it.
19059 However, as variables in the (example) program persist with their
19060 assigned values, the variable @code{p} would point to an invalid
19061 location when the command exists. A general rule should be followed
19062 in that you should either assign @code{NULL} to any assigned pointers,
19063 or restore a valid location to the pointer before the command exits.
19065 Similar caution must be exercised with any structs, unions, and typedefs
19066 defined in @code{compile} command. Types defined in the @code{compile}
19067 command will no longer be available in the next @code{compile} command.
19068 Therefore, if you cast a variable to a type defined in the
19069 @code{compile} command, care must be taken to ensure that any future
19070 need to resolve the type can be achieved.
19073 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19074 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19075 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19076 Compilation failed.
19077 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19081 Variables that have been optimized away by the compiler are not
19082 accessible to the code submitted to the @code{compile} command.
19083 Access to those variables will generate a compiler error which @value{GDBN}
19084 will print to the console.
19087 @subsection Compiler search for the @code{compile} command
19089 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19090 which may not be obvious for remote targets of different architecture
19091 than where @value{GDBN} is running. Environment variable @code{PATH} on
19092 @value{GDBN} host is searched for @value{NGCC} binary matching the
19093 target architecture and operating system. This search can be overriden
19094 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19095 taken from shell that executed @value{GDBN}, it is not the value set by
19096 @value{GDBN} command @code{set environment}). @xref{Environment}.
19099 Specifically @code{PATH} is searched for binaries matching regular expression
19100 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19101 debugged. @var{arch} is processor name --- multiarch is supported, so for
19102 example both @code{i386} and @code{x86_64} targets look for pattern
19103 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19104 for pattern @code{s390x?}. @var{os} is currently supported only for
19105 pattern @code{linux(-gnu)?}.
19107 On Posix hosts the compiler driver @value{GDBN} needs to find also
19108 shared library @file{libcc1.so} from the compiler. It is searched in
19109 default shared library search path (overridable with usual environment
19110 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19111 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19112 according to the installation of the found compiler --- as possibly
19113 specified by the @code{set compile-gcc} command.
19116 @item set compile-gcc
19117 @cindex compile command driver filename override
19118 Set compilation command used for compiling and injecting code with the
19119 @code{compile} commands. If this option is not set (it is set to
19120 an empty string), the search described above will occur --- that is the
19123 @item show compile-gcc
19124 Displays the current compile command @value{NGCC} driver filename.
19125 If set, it is the main command @command{gcc}, found usually for example
19126 under name @file{x86_64-linux-gnu-gcc}.
19130 @chapter @value{GDBN} Files
19132 @value{GDBN} needs to know the file name of the program to be debugged,
19133 both in order to read its symbol table and in order to start your
19134 program. To debug a core dump of a previous run, you must also tell
19135 @value{GDBN} the name of the core dump file.
19138 * Files:: Commands to specify files
19139 * File Caching:: Information about @value{GDBN}'s file caching
19140 * Separate Debug Files:: Debugging information in separate files
19141 * MiniDebugInfo:: Debugging information in a special section
19142 * Index Files:: Index files speed up GDB
19143 * Symbol Errors:: Errors reading symbol files
19144 * Data Files:: GDB data files
19148 @section Commands to Specify Files
19150 @cindex symbol table
19151 @cindex core dump file
19153 You may want to specify executable and core dump file names. The usual
19154 way to do this is at start-up time, using the arguments to
19155 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19156 Out of @value{GDBN}}).
19158 Occasionally it is necessary to change to a different file during a
19159 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19160 specify a file you want to use. Or you are debugging a remote target
19161 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19162 Program}). In these situations the @value{GDBN} commands to specify
19163 new files are useful.
19166 @cindex executable file
19168 @item file @var{filename}
19169 Use @var{filename} as the program to be debugged. It is read for its
19170 symbols and for the contents of pure memory. It is also the program
19171 executed when you use the @code{run} command. If you do not specify a
19172 directory and the file is not found in the @value{GDBN} working directory,
19173 @value{GDBN} uses the environment variable @code{PATH} as a list of
19174 directories to search, just as the shell does when looking for a program
19175 to run. You can change the value of this variable, for both @value{GDBN}
19176 and your program, using the @code{path} command.
19178 @cindex unlinked object files
19179 @cindex patching object files
19180 You can load unlinked object @file{.o} files into @value{GDBN} using
19181 the @code{file} command. You will not be able to ``run'' an object
19182 file, but you can disassemble functions and inspect variables. Also,
19183 if the underlying BFD functionality supports it, you could use
19184 @kbd{gdb -write} to patch object files using this technique. Note
19185 that @value{GDBN} can neither interpret nor modify relocations in this
19186 case, so branches and some initialized variables will appear to go to
19187 the wrong place. But this feature is still handy from time to time.
19190 @code{file} with no argument makes @value{GDBN} discard any information it
19191 has on both executable file and the symbol table.
19194 @item exec-file @r{[} @var{filename} @r{]}
19195 Specify that the program to be run (but not the symbol table) is found
19196 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19197 if necessary to locate your program. Omitting @var{filename} means to
19198 discard information on the executable file.
19200 @kindex symbol-file
19201 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19202 Read symbol table information from file @var{filename}. @code{PATH} is
19203 searched when necessary. Use the @code{file} command to get both symbol
19204 table and program to run from the same file.
19206 If an optional @var{offset} is specified, it is added to the start
19207 address of each section in the symbol file. This is useful if the
19208 program is relocated at runtime, such as the Linux kernel with kASLR
19211 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19212 program's symbol table.
19214 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19215 some breakpoints and auto-display expressions. This is because they may
19216 contain pointers to the internal data recording symbols and data types,
19217 which are part of the old symbol table data being discarded inside
19220 @code{symbol-file} does not repeat if you press @key{RET} again after
19223 When @value{GDBN} is configured for a particular environment, it
19224 understands debugging information in whatever format is the standard
19225 generated for that environment; you may use either a @sc{gnu} compiler, or
19226 other compilers that adhere to the local conventions.
19227 Best results are usually obtained from @sc{gnu} compilers; for example,
19228 using @code{@value{NGCC}} you can generate debugging information for
19231 For most kinds of object files, with the exception of old SVR3 systems
19232 using COFF, the @code{symbol-file} command does not normally read the
19233 symbol table in full right away. Instead, it scans the symbol table
19234 quickly to find which source files and which symbols are present. The
19235 details are read later, one source file at a time, as they are needed.
19237 The purpose of this two-stage reading strategy is to make @value{GDBN}
19238 start up faster. For the most part, it is invisible except for
19239 occasional pauses while the symbol table details for a particular source
19240 file are being read. (The @code{set verbose} command can turn these
19241 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19242 Warnings and Messages}.)
19244 We have not implemented the two-stage strategy for COFF yet. When the
19245 symbol table is stored in COFF format, @code{symbol-file} reads the
19246 symbol table data in full right away. Note that ``stabs-in-COFF''
19247 still does the two-stage strategy, since the debug info is actually
19251 @cindex reading symbols immediately
19252 @cindex symbols, reading immediately
19253 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19254 @itemx file @r{[} -readnow @r{]} @var{filename}
19255 You can override the @value{GDBN} two-stage strategy for reading symbol
19256 tables by using the @samp{-readnow} option with any of the commands that
19257 load symbol table information, if you want to be sure @value{GDBN} has the
19258 entire symbol table available.
19260 @cindex @code{-readnever}, option for symbol-file command
19261 @cindex never read symbols
19262 @cindex symbols, never read
19263 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19264 @itemx file @r{[} -readnever @r{]} @var{filename}
19265 You can instruct @value{GDBN} to never read the symbolic information
19266 contained in @var{filename} by using the @samp{-readnever} option.
19267 @xref{--readnever}.
19269 @c FIXME: for now no mention of directories, since this seems to be in
19270 @c flux. 13mar1992 status is that in theory GDB would look either in
19271 @c current dir or in same dir as myprog; but issues like competing
19272 @c GDB's, or clutter in system dirs, mean that in practice right now
19273 @c only current dir is used. FFish says maybe a special GDB hierarchy
19274 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19278 @item core-file @r{[}@var{filename}@r{]}
19280 Specify the whereabouts of a core dump file to be used as the ``contents
19281 of memory''. Traditionally, core files contain only some parts of the
19282 address space of the process that generated them; @value{GDBN} can access the
19283 executable file itself for other parts.
19285 @code{core-file} with no argument specifies that no core file is
19288 Note that the core file is ignored when your program is actually running
19289 under @value{GDBN}. So, if you have been running your program and you
19290 wish to debug a core file instead, you must kill the subprocess in which
19291 the program is running. To do this, use the @code{kill} command
19292 (@pxref{Kill Process, ,Killing the Child Process}).
19294 @kindex add-symbol-file
19295 @cindex dynamic linking
19296 @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{]}
19297 The @code{add-symbol-file} command reads additional symbol table
19298 information from the file @var{filename}. You would use this command
19299 when @var{filename} has been dynamically loaded (by some other means)
19300 into the program that is running. The @var{textaddress} parameter gives
19301 the memory address at which the file's text section has been loaded.
19302 You can additionally specify the base address of other sections using
19303 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19304 If a section is omitted, @value{GDBN} will use its default addresses
19305 as found in @var{filename}. Any @var{address} or @var{textaddress}
19306 can be given as an expression.
19308 If an optional @var{offset} is specified, it is added to the start
19309 address of each section, except those for which the address was
19310 specified explicitly.
19312 The symbol table of the file @var{filename} is added to the symbol table
19313 originally read with the @code{symbol-file} command. You can use the
19314 @code{add-symbol-file} command any number of times; the new symbol data
19315 thus read is kept in addition to the old.
19317 Changes can be reverted using the command @code{remove-symbol-file}.
19319 @cindex relocatable object files, reading symbols from
19320 @cindex object files, relocatable, reading symbols from
19321 @cindex reading symbols from relocatable object files
19322 @cindex symbols, reading from relocatable object files
19323 @cindex @file{.o} files, reading symbols from
19324 Although @var{filename} is typically a shared library file, an
19325 executable file, or some other object file which has been fully
19326 relocated for loading into a process, you can also load symbolic
19327 information from relocatable @file{.o} files, as long as:
19331 the file's symbolic information refers only to linker symbols defined in
19332 that file, not to symbols defined by other object files,
19334 every section the file's symbolic information refers to has actually
19335 been loaded into the inferior, as it appears in the file, and
19337 you can determine the address at which every section was loaded, and
19338 provide these to the @code{add-symbol-file} command.
19342 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19343 relocatable files into an already running program; such systems
19344 typically make the requirements above easy to meet. However, it's
19345 important to recognize that many native systems use complex link
19346 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19347 assembly, for example) that make the requirements difficult to meet. In
19348 general, one cannot assume that using @code{add-symbol-file} to read a
19349 relocatable object file's symbolic information will have the same effect
19350 as linking the relocatable object file into the program in the normal
19353 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19355 @kindex remove-symbol-file
19356 @item remove-symbol-file @var{filename}
19357 @item remove-symbol-file -a @var{address}
19358 Remove a symbol file added via the @code{add-symbol-file} command. The
19359 file to remove can be identified by its @var{filename} or by an @var{address}
19360 that lies within the boundaries of this symbol file in memory. Example:
19363 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19364 add symbol table from file "/home/user/gdb/mylib.so" at
19365 .text_addr = 0x7ffff7ff9480
19367 Reading symbols from /home/user/gdb/mylib.so...done.
19368 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19369 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19374 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19376 @kindex add-symbol-file-from-memory
19377 @cindex @code{syscall DSO}
19378 @cindex load symbols from memory
19379 @item add-symbol-file-from-memory @var{address}
19380 Load symbols from the given @var{address} in a dynamically loaded
19381 object file whose image is mapped directly into the inferior's memory.
19382 For example, the Linux kernel maps a @code{syscall DSO} into each
19383 process's address space; this DSO provides kernel-specific code for
19384 some system calls. The argument can be any expression whose
19385 evaluation yields the address of the file's shared object file header.
19386 For this command to work, you must have used @code{symbol-file} or
19387 @code{exec-file} commands in advance.
19390 @item section @var{section} @var{addr}
19391 The @code{section} command changes the base address of the named
19392 @var{section} of the exec file to @var{addr}. This can be used if the
19393 exec file does not contain section addresses, (such as in the
19394 @code{a.out} format), or when the addresses specified in the file
19395 itself are wrong. Each section must be changed separately. The
19396 @code{info files} command, described below, lists all the sections and
19400 @kindex info target
19403 @code{info files} and @code{info target} are synonymous; both print the
19404 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19405 including the names of the executable and core dump files currently in
19406 use by @value{GDBN}, and the files from which symbols were loaded. The
19407 command @code{help target} lists all possible targets rather than
19410 @kindex maint info sections
19411 @item maint info sections
19412 Another command that can give you extra information about program sections
19413 is @code{maint info sections}. In addition to the section information
19414 displayed by @code{info files}, this command displays the flags and file
19415 offset of each section in the executable and core dump files. In addition,
19416 @code{maint info sections} provides the following command options (which
19417 may be arbitrarily combined):
19421 Display sections for all loaded object files, including shared libraries.
19422 @item @var{sections}
19423 Display info only for named @var{sections}.
19424 @item @var{section-flags}
19425 Display info only for sections for which @var{section-flags} are true.
19426 The section flags that @value{GDBN} currently knows about are:
19429 Section will have space allocated in the process when loaded.
19430 Set for all sections except those containing debug information.
19432 Section will be loaded from the file into the child process memory.
19433 Set for pre-initialized code and data, clear for @code{.bss} sections.
19435 Section needs to be relocated before loading.
19437 Section cannot be modified by the child process.
19439 Section contains executable code only.
19441 Section contains data only (no executable code).
19443 Section will reside in ROM.
19445 Section contains data for constructor/destructor lists.
19447 Section is not empty.
19449 An instruction to the linker to not output the section.
19450 @item COFF_SHARED_LIBRARY
19451 A notification to the linker that the section contains
19452 COFF shared library information.
19454 Section contains common symbols.
19457 @kindex set trust-readonly-sections
19458 @cindex read-only sections
19459 @item set trust-readonly-sections on
19460 Tell @value{GDBN} that readonly sections in your object file
19461 really are read-only (i.e.@: that their contents will not change).
19462 In that case, @value{GDBN} can fetch values from these sections
19463 out of the object file, rather than from the target program.
19464 For some targets (notably embedded ones), this can be a significant
19465 enhancement to debugging performance.
19467 The default is off.
19469 @item set trust-readonly-sections off
19470 Tell @value{GDBN} not to trust readonly sections. This means that
19471 the contents of the section might change while the program is running,
19472 and must therefore be fetched from the target when needed.
19474 @item show trust-readonly-sections
19475 Show the current setting of trusting readonly sections.
19478 All file-specifying commands allow both absolute and relative file names
19479 as arguments. @value{GDBN} always converts the file name to an absolute file
19480 name and remembers it that way.
19482 @cindex shared libraries
19483 @anchor{Shared Libraries}
19484 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19485 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19486 DSBT (TIC6X) shared libraries.
19488 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19489 shared libraries. @xref{Expat}.
19491 @value{GDBN} automatically loads symbol definitions from shared libraries
19492 when you use the @code{run} command, or when you examine a core file.
19493 (Before you issue the @code{run} command, @value{GDBN} does not understand
19494 references to a function in a shared library, however---unless you are
19495 debugging a core file).
19497 @c FIXME: some @value{GDBN} release may permit some refs to undef
19498 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19499 @c FIXME...lib; check this from time to time when updating manual
19501 There are times, however, when you may wish to not automatically load
19502 symbol definitions from shared libraries, such as when they are
19503 particularly large or there are many of them.
19505 To control the automatic loading of shared library symbols, use the
19509 @kindex set auto-solib-add
19510 @item set auto-solib-add @var{mode}
19511 If @var{mode} is @code{on}, symbols from all shared object libraries
19512 will be loaded automatically when the inferior begins execution, you
19513 attach to an independently started inferior, or when the dynamic linker
19514 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19515 is @code{off}, symbols must be loaded manually, using the
19516 @code{sharedlibrary} command. The default value is @code{on}.
19518 @cindex memory used for symbol tables
19519 If your program uses lots of shared libraries with debug info that
19520 takes large amounts of memory, you can decrease the @value{GDBN}
19521 memory footprint by preventing it from automatically loading the
19522 symbols from shared libraries. To that end, type @kbd{set
19523 auto-solib-add off} before running the inferior, then load each
19524 library whose debug symbols you do need with @kbd{sharedlibrary
19525 @var{regexp}}, where @var{regexp} is a regular expression that matches
19526 the libraries whose symbols you want to be loaded.
19528 @kindex show auto-solib-add
19529 @item show auto-solib-add
19530 Display the current autoloading mode.
19533 @cindex load shared library
19534 To explicitly load shared library symbols, use the @code{sharedlibrary}
19538 @kindex info sharedlibrary
19540 @item info share @var{regex}
19541 @itemx info sharedlibrary @var{regex}
19542 Print the names of the shared libraries which are currently loaded
19543 that match @var{regex}. If @var{regex} is omitted then print
19544 all shared libraries that are loaded.
19547 @item info dll @var{regex}
19548 This is an alias of @code{info sharedlibrary}.
19550 @kindex sharedlibrary
19552 @item sharedlibrary @var{regex}
19553 @itemx share @var{regex}
19554 Load shared object library symbols for files matching a
19555 Unix regular expression.
19556 As with files loaded automatically, it only loads shared libraries
19557 required by your program for a core file or after typing @code{run}. If
19558 @var{regex} is omitted all shared libraries required by your program are
19561 @item nosharedlibrary
19562 @kindex nosharedlibrary
19563 @cindex unload symbols from shared libraries
19564 Unload all shared object library symbols. This discards all symbols
19565 that have been loaded from all shared libraries. Symbols from shared
19566 libraries that were loaded by explicit user requests are not
19570 Sometimes you may wish that @value{GDBN} stops and gives you control
19571 when any of shared library events happen. The best way to do this is
19572 to use @code{catch load} and @code{catch unload} (@pxref{Set
19575 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19576 command for this. This command exists for historical reasons. It is
19577 less useful than setting a catchpoint, because it does not allow for
19578 conditions or commands as a catchpoint does.
19581 @item set stop-on-solib-events
19582 @kindex set stop-on-solib-events
19583 This command controls whether @value{GDBN} should give you control
19584 when the dynamic linker notifies it about some shared library event.
19585 The most common event of interest is loading or unloading of a new
19588 @item show stop-on-solib-events
19589 @kindex show stop-on-solib-events
19590 Show whether @value{GDBN} stops and gives you control when shared
19591 library events happen.
19594 Shared libraries are also supported in many cross or remote debugging
19595 configurations. @value{GDBN} needs to have access to the target's libraries;
19596 this can be accomplished either by providing copies of the libraries
19597 on the host system, or by asking @value{GDBN} to automatically retrieve the
19598 libraries from the target. If copies of the target libraries are
19599 provided, they need to be the same as the target libraries, although the
19600 copies on the target can be stripped as long as the copies on the host are
19603 @cindex where to look for shared libraries
19604 For remote debugging, you need to tell @value{GDBN} where the target
19605 libraries are, so that it can load the correct copies---otherwise, it
19606 may try to load the host's libraries. @value{GDBN} has two variables
19607 to specify the search directories for target libraries.
19610 @cindex prefix for executable and shared library file names
19611 @cindex system root, alternate
19612 @kindex set solib-absolute-prefix
19613 @kindex set sysroot
19614 @item set sysroot @var{path}
19615 Use @var{path} as the system root for the program being debugged. Any
19616 absolute shared library paths will be prefixed with @var{path}; many
19617 runtime loaders store the absolute paths to the shared library in the
19618 target program's memory. When starting processes remotely, and when
19619 attaching to already-running processes (local or remote), their
19620 executable filenames will be prefixed with @var{path} if reported to
19621 @value{GDBN} as absolute by the operating system. If you use
19622 @code{set sysroot} to find executables and shared libraries, they need
19623 to be laid out in the same way that they are on the target, with
19624 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19627 If @var{path} starts with the sequence @file{target:} and the target
19628 system is remote then @value{GDBN} will retrieve the target binaries
19629 from the remote system. This is only supported when using a remote
19630 target that supports the @code{remote get} command (@pxref{File
19631 Transfer,,Sending files to a remote system}). The part of @var{path}
19632 following the initial @file{target:} (if present) is used as system
19633 root prefix on the remote file system. If @var{path} starts with the
19634 sequence @file{remote:} this is converted to the sequence
19635 @file{target:} by @code{set sysroot}@footnote{Historically the
19636 functionality to retrieve binaries from the remote system was
19637 provided by prefixing @var{path} with @file{remote:}}. If you want
19638 to specify a local system root using a directory that happens to be
19639 named @file{target:} or @file{remote:}, you need to use some
19640 equivalent variant of the name like @file{./target:}.
19642 For targets with an MS-DOS based filesystem, such as MS-Windows and
19643 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19644 absolute file name with @var{path}. But first, on Unix hosts,
19645 @value{GDBN} converts all backslash directory separators into forward
19646 slashes, because the backslash is not a directory separator on Unix:
19649 c:\foo\bar.dll @result{} c:/foo/bar.dll
19652 Then, @value{GDBN} attempts prefixing the target file name with
19653 @var{path}, and looks for the resulting file name in the host file
19657 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19660 If that does not find the binary, @value{GDBN} tries removing
19661 the @samp{:} character from the drive spec, both for convenience, and,
19662 for the case of the host file system not supporting file names with
19666 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19669 This makes it possible to have a system root that mirrors a target
19670 with more than one drive. E.g., you may want to setup your local
19671 copies of the target system shared libraries like so (note @samp{c} vs
19675 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19676 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19677 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19681 and point the system root at @file{/path/to/sysroot}, so that
19682 @value{GDBN} can find the correct copies of both
19683 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19685 If that still does not find the binary, @value{GDBN} tries
19686 removing the whole drive spec from the target file name:
19689 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19692 This last lookup makes it possible to not care about the drive name,
19693 if you don't want or need to.
19695 The @code{set solib-absolute-prefix} command is an alias for @code{set
19698 @cindex default system root
19699 @cindex @samp{--with-sysroot}
19700 You can set the default system root by using the configure-time
19701 @samp{--with-sysroot} option. If the system root is inside
19702 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19703 @samp{--exec-prefix}), then the default system root will be updated
19704 automatically if the installed @value{GDBN} is moved to a new
19707 @kindex show sysroot
19709 Display the current executable and shared library prefix.
19711 @kindex set solib-search-path
19712 @item set solib-search-path @var{path}
19713 If this variable is set, @var{path} is a colon-separated list of
19714 directories to search for shared libraries. @samp{solib-search-path}
19715 is used after @samp{sysroot} fails to locate the library, or if the
19716 path to the library is relative instead of absolute. If you want to
19717 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19718 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19719 finding your host's libraries. @samp{sysroot} is preferred; setting
19720 it to a nonexistent directory may interfere with automatic loading
19721 of shared library symbols.
19723 @kindex show solib-search-path
19724 @item show solib-search-path
19725 Display the current shared library search path.
19727 @cindex DOS file-name semantics of file names.
19728 @kindex set target-file-system-kind (unix|dos-based|auto)
19729 @kindex show target-file-system-kind
19730 @item set target-file-system-kind @var{kind}
19731 Set assumed file system kind for target reported file names.
19733 Shared library file names as reported by the target system may not
19734 make sense as is on the system @value{GDBN} is running on. For
19735 example, when remote debugging a target that has MS-DOS based file
19736 system semantics, from a Unix host, the target may be reporting to
19737 @value{GDBN} a list of loaded shared libraries with file names such as
19738 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19739 drive letters, so the @samp{c:\} prefix is not normally understood as
19740 indicating an absolute file name, and neither is the backslash
19741 normally considered a directory separator character. In that case,
19742 the native file system would interpret this whole absolute file name
19743 as a relative file name with no directory components. This would make
19744 it impossible to point @value{GDBN} at a copy of the remote target's
19745 shared libraries on the host using @code{set sysroot}, and impractical
19746 with @code{set solib-search-path}. Setting
19747 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19748 to interpret such file names similarly to how the target would, and to
19749 map them to file names valid on @value{GDBN}'s native file system
19750 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19751 to one of the supported file system kinds. In that case, @value{GDBN}
19752 tries to determine the appropriate file system variant based on the
19753 current target's operating system (@pxref{ABI, ,Configuring the
19754 Current ABI}). The supported file system settings are:
19758 Instruct @value{GDBN} to assume the target file system is of Unix
19759 kind. Only file names starting the forward slash (@samp{/}) character
19760 are considered absolute, and the directory separator character is also
19764 Instruct @value{GDBN} to assume the target file system is DOS based.
19765 File names starting with either a forward slash, or a drive letter
19766 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19767 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19768 considered directory separators.
19771 Instruct @value{GDBN} to use the file system kind associated with the
19772 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19773 This is the default.
19777 @cindex file name canonicalization
19778 @cindex base name differences
19779 When processing file names provided by the user, @value{GDBN}
19780 frequently needs to compare them to the file names recorded in the
19781 program's debug info. Normally, @value{GDBN} compares just the
19782 @dfn{base names} of the files as strings, which is reasonably fast
19783 even for very large programs. (The base name of a file is the last
19784 portion of its name, after stripping all the leading directories.)
19785 This shortcut in comparison is based upon the assumption that files
19786 cannot have more than one base name. This is usually true, but
19787 references to files that use symlinks or similar filesystem
19788 facilities violate that assumption. If your program records files
19789 using such facilities, or if you provide file names to @value{GDBN}
19790 using symlinks etc., you can set @code{basenames-may-differ} to
19791 @code{true} to instruct @value{GDBN} to completely canonicalize each
19792 pair of file names it needs to compare. This will make file-name
19793 comparisons accurate, but at a price of a significant slowdown.
19796 @item set basenames-may-differ
19797 @kindex set basenames-may-differ
19798 Set whether a source file may have multiple base names.
19800 @item show basenames-may-differ
19801 @kindex show basenames-may-differ
19802 Show whether a source file may have multiple base names.
19806 @section File Caching
19807 @cindex caching of opened files
19808 @cindex caching of bfd objects
19810 To speed up file loading, and reduce memory usage, @value{GDBN} will
19811 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19812 BFD, bfd, The Binary File Descriptor Library}. The following commands
19813 allow visibility and control of the caching behavior.
19816 @kindex maint info bfds
19817 @item maint info bfds
19818 This prints information about each @code{bfd} object that is known to
19821 @kindex maint set bfd-sharing
19822 @kindex maint show bfd-sharing
19823 @kindex bfd caching
19824 @item maint set bfd-sharing
19825 @item maint show bfd-sharing
19826 Control whether @code{bfd} objects can be shared. When sharing is
19827 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19828 than reopening the same file. Turning sharing off does not cause
19829 already shared @code{bfd} objects to be unshared, but all future files
19830 that are opened will create a new @code{bfd} object. Similarly,
19831 re-enabling sharing does not cause multiple existing @code{bfd}
19832 objects to be collapsed into a single shared @code{bfd} object.
19834 @kindex set debug bfd-cache @var{level}
19835 @kindex bfd caching
19836 @item set debug bfd-cache @var{level}
19837 Turns on debugging of the bfd cache, setting the level to @var{level}.
19839 @kindex show debug bfd-cache
19840 @kindex bfd caching
19841 @item show debug bfd-cache
19842 Show the current debugging level of the bfd cache.
19845 @node Separate Debug Files
19846 @section Debugging Information in Separate Files
19847 @cindex separate debugging information files
19848 @cindex debugging information in separate files
19849 @cindex @file{.debug} subdirectories
19850 @cindex debugging information directory, global
19851 @cindex global debugging information directories
19852 @cindex build ID, and separate debugging files
19853 @cindex @file{.build-id} directory
19855 @value{GDBN} allows you to put a program's debugging information in a
19856 file separate from the executable itself, in a way that allows
19857 @value{GDBN} to find and load the debugging information automatically.
19858 Since debugging information can be very large---sometimes larger
19859 than the executable code itself---some systems distribute debugging
19860 information for their executables in separate files, which users can
19861 install only when they need to debug a problem.
19863 @value{GDBN} supports two ways of specifying the separate debug info
19868 The executable contains a @dfn{debug link} that specifies the name of
19869 the separate debug info file. The separate debug file's name is
19870 usually @file{@var{executable}.debug}, where @var{executable} is the
19871 name of the corresponding executable file without leading directories
19872 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19873 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19874 checksum for the debug file, which @value{GDBN} uses to validate that
19875 the executable and the debug file came from the same build.
19878 The executable contains a @dfn{build ID}, a unique bit string that is
19879 also present in the corresponding debug info file. (This is supported
19880 only on some operating systems, when using the ELF or PE file formats
19881 for binary files and the @sc{gnu} Binutils.) For more details about
19882 this feature, see the description of the @option{--build-id}
19883 command-line option in @ref{Options, , Command Line Options, ld,
19884 The GNU Linker}. The debug info file's name is not specified
19885 explicitly by the build ID, but can be computed from the build ID, see
19889 Depending on the way the debug info file is specified, @value{GDBN}
19890 uses two different methods of looking for the debug file:
19894 For the ``debug link'' method, @value{GDBN} looks up the named file in
19895 the directory of the executable file, then in a subdirectory of that
19896 directory named @file{.debug}, and finally under each one of the global debug
19897 directories, in a subdirectory whose name is identical to the leading
19898 directories of the executable's absolute file name.
19901 For the ``build ID'' method, @value{GDBN} looks in the
19902 @file{.build-id} subdirectory of each one of the global debug directories for
19903 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19904 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19905 are the rest of the bit string. (Real build ID strings are 32 or more
19906 hex characters, not 10.)
19909 So, for example, suppose you ask @value{GDBN} to debug
19910 @file{/usr/bin/ls}, which has a debug link that specifies the
19911 file @file{ls.debug}, and a build ID whose value in hex is
19912 @code{abcdef1234}. If the list of the global debug directories includes
19913 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19914 debug information files, in the indicated order:
19918 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19920 @file{/usr/bin/ls.debug}
19922 @file{/usr/bin/.debug/ls.debug}
19924 @file{/usr/lib/debug/usr/bin/ls.debug}.
19927 @anchor{debug-file-directory}
19928 Global debugging info directories default to what is set by @value{GDBN}
19929 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19930 you can also set the global debugging info directories, and view the list
19931 @value{GDBN} is currently using.
19935 @kindex set debug-file-directory
19936 @item set debug-file-directory @var{directories}
19937 Set the directories which @value{GDBN} searches for separate debugging
19938 information files to @var{directory}. Multiple path components can be set
19939 concatenating them by a path separator.
19941 @kindex show debug-file-directory
19942 @item show debug-file-directory
19943 Show the directories @value{GDBN} searches for separate debugging
19948 @cindex @code{.gnu_debuglink} sections
19949 @cindex debug link sections
19950 A debug link is a special section of the executable file named
19951 @code{.gnu_debuglink}. The section must contain:
19955 A filename, with any leading directory components removed, followed by
19958 zero to three bytes of padding, as needed to reach the next four-byte
19959 boundary within the section, and
19961 a four-byte CRC checksum, stored in the same endianness used for the
19962 executable file itself. The checksum is computed on the debugging
19963 information file's full contents by the function given below, passing
19964 zero as the @var{crc} argument.
19967 Any executable file format can carry a debug link, as long as it can
19968 contain a section named @code{.gnu_debuglink} with the contents
19971 @cindex @code{.note.gnu.build-id} sections
19972 @cindex build ID sections
19973 The build ID is a special section in the executable file (and in other
19974 ELF binary files that @value{GDBN} may consider). This section is
19975 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19976 It contains unique identification for the built files---the ID remains
19977 the same across multiple builds of the same build tree. The default
19978 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19979 content for the build ID string. The same section with an identical
19980 value is present in the original built binary with symbols, in its
19981 stripped variant, and in the separate debugging information file.
19983 The debugging information file itself should be an ordinary
19984 executable, containing a full set of linker symbols, sections, and
19985 debugging information. The sections of the debugging information file
19986 should have the same names, addresses, and sizes as the original file,
19987 but they need not contain any data---much like a @code{.bss} section
19988 in an ordinary executable.
19990 The @sc{gnu} binary utilities (Binutils) package includes the
19991 @samp{objcopy} utility that can produce
19992 the separated executable / debugging information file pairs using the
19993 following commands:
19996 @kbd{objcopy --only-keep-debug foo foo.debug}
20001 These commands remove the debugging
20002 information from the executable file @file{foo} and place it in the file
20003 @file{foo.debug}. You can use the first, second or both methods to link the
20008 The debug link method needs the following additional command to also leave
20009 behind a debug link in @file{foo}:
20012 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20015 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20016 a version of the @code{strip} command such that the command @kbd{strip foo -f
20017 foo.debug} has the same functionality as the two @code{objcopy} commands and
20018 the @code{ln -s} command above, together.
20021 Build ID gets embedded into the main executable using @code{ld --build-id} or
20022 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20023 compatibility fixes for debug files separation are present in @sc{gnu} binary
20024 utilities (Binutils) package since version 2.18.
20029 @cindex CRC algorithm definition
20030 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20031 IEEE 802.3 using the polynomial:
20033 @c TexInfo requires naked braces for multi-digit exponents for Tex
20034 @c output, but this causes HTML output to barf. HTML has to be set using
20035 @c raw commands. So we end up having to specify this equation in 2
20040 <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>
20041 + <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
20047 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20048 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20052 The function is computed byte at a time, taking the least
20053 significant bit of each byte first. The initial pattern
20054 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20055 the final result is inverted to ensure trailing zeros also affect the
20058 @emph{Note:} This is the same CRC polynomial as used in handling the
20059 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20060 However in the case of the Remote Serial Protocol, the CRC is computed
20061 @emph{most} significant bit first, and the result is not inverted, so
20062 trailing zeros have no effect on the CRC value.
20064 To complete the description, we show below the code of the function
20065 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20066 initially supplied @code{crc} argument means that an initial call to
20067 this function passing in zero will start computing the CRC using
20070 @kindex gnu_debuglink_crc32
20073 gnu_debuglink_crc32 (unsigned long crc,
20074 unsigned char *buf, size_t len)
20076 static const unsigned long crc32_table[256] =
20078 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20079 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20080 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20081 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20082 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20083 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20084 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20085 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20086 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20087 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20088 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20089 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20090 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20091 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20092 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20093 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20094 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20095 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20096 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20097 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20098 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20099 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20100 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20101 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20102 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20103 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20104 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20105 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20106 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20107 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20108 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20109 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20110 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20111 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20112 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20113 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20114 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20115 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20116 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20117 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20118 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20119 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20120 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20121 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20122 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20123 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20124 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20125 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20126 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20127 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20128 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20131 unsigned char *end;
20133 crc = ~crc & 0xffffffff;
20134 for (end = buf + len; buf < end; ++buf)
20135 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20136 return ~crc & 0xffffffff;
20141 This computation does not apply to the ``build ID'' method.
20143 @node MiniDebugInfo
20144 @section Debugging information in a special section
20145 @cindex separate debug sections
20146 @cindex @samp{.gnu_debugdata} section
20148 Some systems ship pre-built executables and libraries that have a
20149 special @samp{.gnu_debugdata} section. This feature is called
20150 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20151 is used to supply extra symbols for backtraces.
20153 The intent of this section is to provide extra minimal debugging
20154 information for use in simple backtraces. It is not intended to be a
20155 replacement for full separate debugging information (@pxref{Separate
20156 Debug Files}). The example below shows the intended use; however,
20157 @value{GDBN} does not currently put restrictions on what sort of
20158 debugging information might be included in the section.
20160 @value{GDBN} has support for this extension. If the section exists,
20161 then it is used provided that no other source of debugging information
20162 can be found, and that @value{GDBN} was configured with LZMA support.
20164 This section can be easily created using @command{objcopy} and other
20165 standard utilities:
20168 # Extract the dynamic symbols from the main binary, there is no need
20169 # to also have these in the normal symbol table.
20170 nm -D @var{binary} --format=posix --defined-only \
20171 | awk '@{ print $1 @}' | sort > dynsyms
20173 # Extract all the text (i.e. function) symbols from the debuginfo.
20174 # (Note that we actually also accept "D" symbols, for the benefit
20175 # of platforms like PowerPC64 that use function descriptors.)
20176 nm @var{binary} --format=posix --defined-only \
20177 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20180 # Keep all the function symbols not already in the dynamic symbol
20182 comm -13 dynsyms funcsyms > keep_symbols
20184 # Separate full debug info into debug binary.
20185 objcopy --only-keep-debug @var{binary} debug
20187 # Copy the full debuginfo, keeping only a minimal set of symbols and
20188 # removing some unnecessary sections.
20189 objcopy -S --remove-section .gdb_index --remove-section .comment \
20190 --keep-symbols=keep_symbols debug mini_debuginfo
20192 # Drop the full debug info from the original binary.
20193 strip --strip-all -R .comment @var{binary}
20195 # Inject the compressed data into the .gnu_debugdata section of the
20198 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20202 @section Index Files Speed Up @value{GDBN}
20203 @cindex index files
20204 @cindex @samp{.gdb_index} section
20206 When @value{GDBN} finds a symbol file, it scans the symbols in the
20207 file in order to construct an internal symbol table. This lets most
20208 @value{GDBN} operations work quickly---at the cost of a delay early
20209 on. For large programs, this delay can be quite lengthy, so
20210 @value{GDBN} provides a way to build an index, which speeds up
20213 For convenience, @value{GDBN} comes with a program,
20214 @command{gdb-add-index}, which can be used to add the index to a
20215 symbol file. It takes the symbol file as its only argument:
20218 $ gdb-add-index symfile
20221 @xref{gdb-add-index}.
20223 It is also possible to do the work manually. Here is what
20224 @command{gdb-add-index} does behind the curtains.
20226 The index is stored as a section in the symbol file. @value{GDBN} can
20227 write the index to a file, then you can put it into the symbol file
20228 using @command{objcopy}.
20230 To create an index file, use the @code{save gdb-index} command:
20233 @item save gdb-index [-dwarf-5] @var{directory}
20234 @kindex save gdb-index
20235 Create index files for all symbol files currently known by
20236 @value{GDBN}. For each known @var{symbol-file}, this command by
20237 default creates it produces a single file
20238 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20239 the @option{-dwarf-5} option, it produces 2 files:
20240 @file{@var{symbol-file}.debug_names} and
20241 @file{@var{symbol-file}.debug_str}. The files are created in the
20242 given @var{directory}.
20245 Once you have created an index file you can merge it into your symbol
20246 file, here named @file{symfile}, using @command{objcopy}:
20249 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20250 --set-section-flags .gdb_index=readonly symfile symfile
20253 Or for @code{-dwarf-5}:
20256 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20257 $ cat symfile.debug_str >>symfile.debug_str.new
20258 $ objcopy --add-section .debug_names=symfile.gdb-index \
20259 --set-section-flags .debug_names=readonly \
20260 --update-section .debug_str=symfile.debug_str.new symfile symfile
20263 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20264 sections that have been deprecated. Usually they are deprecated because
20265 they are missing a new feature or have performance issues.
20266 To tell @value{GDBN} to use a deprecated index section anyway
20267 specify @code{set use-deprecated-index-sections on}.
20268 The default is @code{off}.
20269 This can speed up startup, but may result in some functionality being lost.
20270 @xref{Index Section Format}.
20272 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20273 must be done before gdb reads the file. The following will not work:
20276 $ gdb -ex "set use-deprecated-index-sections on" <program>
20279 Instead you must do, for example,
20282 $ gdb -iex "set use-deprecated-index-sections on" <program>
20285 There are currently some limitation on indices. They only work when
20286 for DWARF debugging information, not stabs. And, they do not
20287 currently work for programs using Ada.
20289 @subsection Automatic symbol index cache
20291 It is possible for @value{GDBN} to automatically save a copy of this index in a
20292 cache on disk and retrieve it from there when loading the same binary in the
20293 future. This feature can be turned on with @kbd{set index-cache on}. The
20294 following commands can be used to tweak the behavior of the index cache.
20298 @item set index-cache on
20299 @itemx set index-cache off
20300 Enable or disable the use of the symbol index cache.
20302 @item set index-cache directory @var{directory}
20303 @itemx show index-cache directory
20304 Set/show the directory where index files will be saved.
20306 The default value for this directory depends on the host platform. On
20307 most systems, the index is cached in the @file{gdb} subdirectory of
20308 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20309 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20310 of your home directory. However, on some systems, the default may
20311 differ according to local convention.
20313 There is no limit on the disk space used by index cache. It is perfectly safe
20314 to delete the content of that directory to free up disk space.
20316 @item show index-cache stats
20317 Print the number of cache hits and misses since the launch of @value{GDBN}.
20321 @node Symbol Errors
20322 @section Errors Reading Symbol Files
20324 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20325 such as symbol types it does not recognize, or known bugs in compiler
20326 output. By default, @value{GDBN} does not notify you of such problems, since
20327 they are relatively common and primarily of interest to people
20328 debugging compilers. If you are interested in seeing information
20329 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20330 only one message about each such type of problem, no matter how many
20331 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20332 to see how many times the problems occur, with the @code{set
20333 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20336 The messages currently printed, and their meanings, include:
20339 @item inner block not inside outer block in @var{symbol}
20341 The symbol information shows where symbol scopes begin and end
20342 (such as at the start of a function or a block of statements). This
20343 error indicates that an inner scope block is not fully contained
20344 in its outer scope blocks.
20346 @value{GDBN} circumvents the problem by treating the inner block as if it had
20347 the same scope as the outer block. In the error message, @var{symbol}
20348 may be shown as ``@code{(don't know)}'' if the outer block is not a
20351 @item block at @var{address} out of order
20353 The symbol information for symbol scope blocks should occur in
20354 order of increasing addresses. This error indicates that it does not
20357 @value{GDBN} does not circumvent this problem, and has trouble
20358 locating symbols in the source file whose symbols it is reading. (You
20359 can often determine what source file is affected by specifying
20360 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20363 @item bad block start address patched
20365 The symbol information for a symbol scope block has a start address
20366 smaller than the address of the preceding source line. This is known
20367 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20369 @value{GDBN} circumvents the problem by treating the symbol scope block as
20370 starting on the previous source line.
20372 @item bad string table offset in symbol @var{n}
20375 Symbol number @var{n} contains a pointer into the string table which is
20376 larger than the size of the string table.
20378 @value{GDBN} circumvents the problem by considering the symbol to have the
20379 name @code{foo}, which may cause other problems if many symbols end up
20382 @item unknown symbol type @code{0x@var{nn}}
20384 The symbol information contains new data types that @value{GDBN} does
20385 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20386 uncomprehended information, in hexadecimal.
20388 @value{GDBN} circumvents the error by ignoring this symbol information.
20389 This usually allows you to debug your program, though certain symbols
20390 are not accessible. If you encounter such a problem and feel like
20391 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20392 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20393 and examine @code{*bufp} to see the symbol.
20395 @item stub type has NULL name
20397 @value{GDBN} could not find the full definition for a struct or class.
20399 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20400 The symbol information for a C@t{++} member function is missing some
20401 information that recent versions of the compiler should have output for
20404 @item info mismatch between compiler and debugger
20406 @value{GDBN} could not parse a type specification output by the compiler.
20411 @section GDB Data Files
20413 @cindex prefix for data files
20414 @value{GDBN} will sometimes read an auxiliary data file. These files
20415 are kept in a directory known as the @dfn{data directory}.
20417 You can set the data directory's name, and view the name @value{GDBN}
20418 is currently using.
20421 @kindex set data-directory
20422 @item set data-directory @var{directory}
20423 Set the directory which @value{GDBN} searches for auxiliary data files
20424 to @var{directory}.
20426 @kindex show data-directory
20427 @item show data-directory
20428 Show the directory @value{GDBN} searches for auxiliary data files.
20431 @cindex default data directory
20432 @cindex @samp{--with-gdb-datadir}
20433 You can set the default data directory by using the configure-time
20434 @samp{--with-gdb-datadir} option. If the data directory is inside
20435 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20436 @samp{--exec-prefix}), then the default data directory will be updated
20437 automatically if the installed @value{GDBN} is moved to a new
20440 The data directory may also be specified with the
20441 @code{--data-directory} command line option.
20442 @xref{Mode Options}.
20445 @chapter Specifying a Debugging Target
20447 @cindex debugging target
20448 A @dfn{target} is the execution environment occupied by your program.
20450 Often, @value{GDBN} runs in the same host environment as your program;
20451 in that case, the debugging target is specified as a side effect when
20452 you use the @code{file} or @code{core} commands. When you need more
20453 flexibility---for example, running @value{GDBN} on a physically separate
20454 host, or controlling a standalone system over a serial port or a
20455 realtime system over a TCP/IP connection---you can use the @code{target}
20456 command to specify one of the target types configured for @value{GDBN}
20457 (@pxref{Target Commands, ,Commands for Managing Targets}).
20459 @cindex target architecture
20460 It is possible to build @value{GDBN} for several different @dfn{target
20461 architectures}. When @value{GDBN} is built like that, you can choose
20462 one of the available architectures with the @kbd{set architecture}
20466 @kindex set architecture
20467 @kindex show architecture
20468 @item set architecture @var{arch}
20469 This command sets the current target architecture to @var{arch}. The
20470 value of @var{arch} can be @code{"auto"}, in addition to one of the
20471 supported architectures.
20473 @item show architecture
20474 Show the current target architecture.
20476 @item set processor
20478 @kindex set processor
20479 @kindex show processor
20480 These are alias commands for, respectively, @code{set architecture}
20481 and @code{show architecture}.
20485 * Active Targets:: Active targets
20486 * Target Commands:: Commands for managing targets
20487 * Byte Order:: Choosing target byte order
20490 @node Active Targets
20491 @section Active Targets
20493 @cindex stacking targets
20494 @cindex active targets
20495 @cindex multiple targets
20497 There are multiple classes of targets such as: processes, executable files or
20498 recording sessions. Core files belong to the process class, making core file
20499 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20500 on multiple active targets, one in each class. This allows you to (for
20501 example) start a process and inspect its activity, while still having access to
20502 the executable file after the process finishes. Or if you start process
20503 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20504 presented a virtual layer of the recording target, while the process target
20505 remains stopped at the chronologically last point of the process execution.
20507 Use the @code{core-file} and @code{exec-file} commands to select a new core
20508 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20509 specify as a target a process that is already running, use the @code{attach}
20510 command (@pxref{Attach, ,Debugging an Already-running Process}).
20512 @node Target Commands
20513 @section Commands for Managing Targets
20516 @item target @var{type} @var{parameters}
20517 Connects the @value{GDBN} host environment to a target machine or
20518 process. A target is typically a protocol for talking to debugging
20519 facilities. You use the argument @var{type} to specify the type or
20520 protocol of the target machine.
20522 Further @var{parameters} are interpreted by the target protocol, but
20523 typically include things like device names or host names to connect
20524 with, process numbers, and baud rates.
20526 The @code{target} command does not repeat if you press @key{RET} again
20527 after executing the command.
20529 @kindex help target
20531 Displays the names of all targets available. To display targets
20532 currently selected, use either @code{info target} or @code{info files}
20533 (@pxref{Files, ,Commands to Specify Files}).
20535 @item help target @var{name}
20536 Describe a particular target, including any parameters necessary to
20539 @kindex set gnutarget
20540 @item set gnutarget @var{args}
20541 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20542 knows whether it is reading an @dfn{executable},
20543 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20544 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20545 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20548 @emph{Warning:} To specify a file format with @code{set gnutarget},
20549 you must know the actual BFD name.
20553 @xref{Files, , Commands to Specify Files}.
20555 @kindex show gnutarget
20556 @item show gnutarget
20557 Use the @code{show gnutarget} command to display what file format
20558 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20559 @value{GDBN} will determine the file format for each file automatically,
20560 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20563 @cindex common targets
20564 Here are some common targets (available, or not, depending on the GDB
20569 @item target exec @var{program}
20570 @cindex executable file target
20571 An executable file. @samp{target exec @var{program}} is the same as
20572 @samp{exec-file @var{program}}.
20574 @item target core @var{filename}
20575 @cindex core dump file target
20576 A core dump file. @samp{target core @var{filename}} is the same as
20577 @samp{core-file @var{filename}}.
20579 @item target remote @var{medium}
20580 @cindex remote target
20581 A remote system connected to @value{GDBN} via a serial line or network
20582 connection. This command tells @value{GDBN} to use its own remote
20583 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20585 For example, if you have a board connected to @file{/dev/ttya} on the
20586 machine running @value{GDBN}, you could say:
20589 target remote /dev/ttya
20592 @code{target remote} supports the @code{load} command. This is only
20593 useful if you have some other way of getting the stub to the target
20594 system, and you can put it somewhere in memory where it won't get
20595 clobbered by the download.
20597 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20598 @cindex built-in simulator target
20599 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20607 works; however, you cannot assume that a specific memory map, device
20608 drivers, or even basic I/O is available, although some simulators do
20609 provide these. For info about any processor-specific simulator details,
20610 see the appropriate section in @ref{Embedded Processors, ,Embedded
20613 @item target native
20614 @cindex native target
20615 Setup for local/native process debugging. Useful to make the
20616 @code{run} command spawn native processes (likewise @code{attach},
20617 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20618 (@pxref{set auto-connect-native-target}).
20622 Different targets are available on different configurations of @value{GDBN};
20623 your configuration may have more or fewer targets.
20625 Many remote targets require you to download the executable's code once
20626 you've successfully established a connection. You may wish to control
20627 various aspects of this process.
20632 @kindex set hash@r{, for remote monitors}
20633 @cindex hash mark while downloading
20634 This command controls whether a hash mark @samp{#} is displayed while
20635 downloading a file to the remote monitor. If on, a hash mark is
20636 displayed after each S-record is successfully downloaded to the
20640 @kindex show hash@r{, for remote monitors}
20641 Show the current status of displaying the hash mark.
20643 @item set debug monitor
20644 @kindex set debug monitor
20645 @cindex display remote monitor communications
20646 Enable or disable display of communications messages between
20647 @value{GDBN} and the remote monitor.
20649 @item show debug monitor
20650 @kindex show debug monitor
20651 Show the current status of displaying communications between
20652 @value{GDBN} and the remote monitor.
20657 @kindex load @var{filename} @var{offset}
20658 @item load @var{filename} @var{offset}
20660 Depending on what remote debugging facilities are configured into
20661 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20662 is meant to make @var{filename} (an executable) available for debugging
20663 on the remote system---by downloading, or dynamic linking, for example.
20664 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20665 the @code{add-symbol-file} command.
20667 If your @value{GDBN} does not have a @code{load} command, attempting to
20668 execute it gets the error message ``@code{You can't do that when your
20669 target is @dots{}}''
20671 The file is loaded at whatever address is specified in the executable.
20672 For some object file formats, you can specify the load address when you
20673 link the program; for other formats, like a.out, the object file format
20674 specifies a fixed address.
20675 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20677 It is also possible to tell @value{GDBN} to load the executable file at a
20678 specific offset described by the optional argument @var{offset}. When
20679 @var{offset} is provided, @var{filename} must also be provided.
20681 Depending on the remote side capabilities, @value{GDBN} may be able to
20682 load programs into flash memory.
20684 @code{load} does not repeat if you press @key{RET} again after using it.
20689 @kindex flash-erase
20691 @anchor{flash-erase}
20693 Erases all known flash memory regions on the target.
20698 @section Choosing Target Byte Order
20700 @cindex choosing target byte order
20701 @cindex target byte order
20703 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20704 offer the ability to run either big-endian or little-endian byte
20705 orders. Usually the executable or symbol will include a bit to
20706 designate the endian-ness, and you will not need to worry about
20707 which to use. However, you may still find it useful to adjust
20708 @value{GDBN}'s idea of processor endian-ness manually.
20712 @item set endian big
20713 Instruct @value{GDBN} to assume the target is big-endian.
20715 @item set endian little
20716 Instruct @value{GDBN} to assume the target is little-endian.
20718 @item set endian auto
20719 Instruct @value{GDBN} to use the byte order associated with the
20723 Display @value{GDBN}'s current idea of the target byte order.
20727 If the @code{set endian auto} mode is in effect and no executable has
20728 been selected, then the endianness used is the last one chosen either
20729 by one of the @code{set endian big} and @code{set endian little}
20730 commands or by inferring from the last executable used. If no
20731 endianness has been previously chosen, then the default for this mode
20732 is inferred from the target @value{GDBN} has been built for, and is
20733 @code{little} if the name of the target CPU has an @code{el} suffix
20734 and @code{big} otherwise.
20736 Note that these commands merely adjust interpretation of symbolic
20737 data on the host, and that they have absolutely no effect on the
20741 @node Remote Debugging
20742 @chapter Debugging Remote Programs
20743 @cindex remote debugging
20745 If you are trying to debug a program running on a machine that cannot run
20746 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20747 For example, you might use remote debugging on an operating system kernel,
20748 or on a small system which does not have a general purpose operating system
20749 powerful enough to run a full-featured debugger.
20751 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20752 to make this work with particular debugging targets. In addition,
20753 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20754 but not specific to any particular target system) which you can use if you
20755 write the remote stubs---the code that runs on the remote system to
20756 communicate with @value{GDBN}.
20758 Other remote targets may be available in your
20759 configuration of @value{GDBN}; use @code{help target} to list them.
20762 * Connecting:: Connecting to a remote target
20763 * File Transfer:: Sending files to a remote system
20764 * Server:: Using the gdbserver program
20765 * Remote Configuration:: Remote configuration
20766 * Remote Stub:: Implementing a remote stub
20770 @section Connecting to a Remote Target
20771 @cindex remote debugging, connecting
20772 @cindex @code{gdbserver}, connecting
20773 @cindex remote debugging, types of connections
20774 @cindex @code{gdbserver}, types of connections
20775 @cindex @code{gdbserver}, @code{target remote} mode
20776 @cindex @code{gdbserver}, @code{target extended-remote} mode
20778 This section describes how to connect to a remote target, including the
20779 types of connections and their differences, how to set up executable and
20780 symbol files on the host and target, and the commands used for
20781 connecting to and disconnecting from the remote target.
20783 @subsection Types of Remote Connections
20785 @value{GDBN} supports two types of remote connections, @code{target remote}
20786 mode and @code{target extended-remote} mode. Note that many remote targets
20787 support only @code{target remote} mode. There are several major
20788 differences between the two types of connections, enumerated here:
20792 @cindex remote debugging, detach and program exit
20793 @item Result of detach or program exit
20794 @strong{With target remote mode:} When the debugged program exits or you
20795 detach from it, @value{GDBN} disconnects from the target. When using
20796 @code{gdbserver}, @code{gdbserver} will exit.
20798 @strong{With target extended-remote mode:} When the debugged program exits or
20799 you detach from it, @value{GDBN} remains connected to the target, even
20800 though no program is running. You can rerun the program, attach to a
20801 running program, or use @code{monitor} commands specific to the target.
20803 When using @code{gdbserver} in this case, it does not exit unless it was
20804 invoked using the @option{--once} option. If the @option{--once} option
20805 was not used, you can ask @code{gdbserver} to exit using the
20806 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20808 @item Specifying the program to debug
20809 For both connection types you use the @code{file} command to specify the
20810 program on the host system. If you are using @code{gdbserver} there are
20811 some differences in how to specify the location of the program on the
20814 @strong{With target remote mode:} You must either specify the program to debug
20815 on the @code{gdbserver} command line or use the @option{--attach} option
20816 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20818 @cindex @option{--multi}, @code{gdbserver} option
20819 @strong{With target extended-remote mode:} You may specify the program to debug
20820 on the @code{gdbserver} command line, or you can load the program or attach
20821 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20823 @anchor{--multi Option in Types of Remote Connnections}
20824 You can start @code{gdbserver} without supplying an initial command to run
20825 or process ID to attach. To do this, use the @option{--multi} command line
20826 option. Then you can connect using @code{target extended-remote} and start
20827 the program you want to debug (see below for details on using the
20828 @code{run} command in this scenario). Note that the conditions under which
20829 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20830 (@code{target remote} or @code{target extended-remote}). The
20831 @option{--multi} option to @code{gdbserver} has no influence on that.
20833 @item The @code{run} command
20834 @strong{With target remote mode:} The @code{run} command is not
20835 supported. Once a connection has been established, you can use all
20836 the usual @value{GDBN} commands to examine and change data. The
20837 remote program is already running, so you can use commands like
20838 @kbd{step} and @kbd{continue}.
20840 @strong{With target extended-remote mode:} The @code{run} command is
20841 supported. The @code{run} command uses the value set by
20842 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20843 the program to run. Command line arguments are supported, except for
20844 wildcard expansion and I/O redirection (@pxref{Arguments}).
20846 If you specify the program to debug on the command line, then the
20847 @code{run} command is not required to start execution, and you can
20848 resume using commands like @kbd{step} and @kbd{continue} as with
20849 @code{target remote} mode.
20851 @anchor{Attaching in Types of Remote Connections}
20853 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20854 not supported. To attach to a running program using @code{gdbserver}, you
20855 must use the @option{--attach} option (@pxref{Running gdbserver}).
20857 @strong{With target extended-remote mode:} To attach to a running program,
20858 you may use the @code{attach} command after the connection has been
20859 established. If you are using @code{gdbserver}, you may also invoke
20860 @code{gdbserver} using the @option{--attach} option
20861 (@pxref{Running gdbserver}).
20865 @anchor{Host and target files}
20866 @subsection Host and Target Files
20867 @cindex remote debugging, symbol files
20868 @cindex symbol files, remote debugging
20870 @value{GDBN}, running on the host, needs access to symbol and debugging
20871 information for your program running on the target. This requires
20872 access to an unstripped copy of your program, and possibly any associated
20873 symbol files. Note that this section applies equally to both @code{target
20874 remote} mode and @code{target extended-remote} mode.
20876 Some remote targets (@pxref{qXfer executable filename read}, and
20877 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20878 the same connection used to communicate with @value{GDBN}. With such a
20879 target, if the remote program is unstripped, the only command you need is
20880 @code{target remote} (or @code{target extended-remote}).
20882 If the remote program is stripped, or the target does not support remote
20883 program file access, start up @value{GDBN} using the name of the local
20884 unstripped copy of your program as the first argument, or use the
20885 @code{file} command. Use @code{set sysroot} to specify the location (on
20886 the host) of target libraries (unless your @value{GDBN} was compiled with
20887 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20888 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20891 The symbol file and target libraries must exactly match the executable
20892 and libraries on the target, with one exception: the files on the host
20893 system should not be stripped, even if the files on the target system
20894 are. Mismatched or missing files will lead to confusing results
20895 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20896 files may also prevent @code{gdbserver} from debugging multi-threaded
20899 @subsection Remote Connection Commands
20900 @cindex remote connection commands
20901 @value{GDBN} can communicate with the target over a serial line, a
20902 local Unix domain socket, or
20903 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20904 each case, @value{GDBN} uses the same protocol for debugging your
20905 program; only the medium carrying the debugging packets varies. The
20906 @code{target remote} and @code{target extended-remote} commands
20907 establish a connection to the target. Both commands accept the same
20908 arguments, which indicate the medium to use:
20912 @item target remote @var{serial-device}
20913 @itemx target extended-remote @var{serial-device}
20914 @cindex serial line, @code{target remote}
20915 Use @var{serial-device} to communicate with the target. For example,
20916 to use a serial line connected to the device named @file{/dev/ttyb}:
20919 target remote /dev/ttyb
20922 If you're using a serial line, you may want to give @value{GDBN} the
20923 @samp{--baud} option, or use the @code{set serial baud} command
20924 (@pxref{Remote Configuration, set serial baud}) before the
20925 @code{target} command.
20927 @item target remote @var{local-socket}
20928 @itemx target extended-remote @var{local-socket}
20929 @cindex local socket, @code{target remote}
20930 @cindex Unix domain socket
20931 Use @var{local-socket} to communicate with the target. For example,
20932 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
20935 target remote /tmp/gdb-socket0
20938 Note that this command has the same form as the command to connect
20939 to a serial line. @value{GDBN} will automatically determine which
20940 kind of file you have specified and will make the appropriate kind
20942 This feature is not available if the host system does not support
20943 Unix domain sockets.
20945 @item target remote @code{@var{host}:@var{port}}
20946 @itemx target remote @code{@var{[host]}:@var{port}}
20947 @itemx target remote @code{tcp:@var{host}:@var{port}}
20948 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
20949 @itemx target remote @code{tcp4:@var{host}:@var{port}}
20950 @itemx target remote @code{tcp6:@var{host}:@var{port}}
20951 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
20952 @itemx target extended-remote @code{@var{host}:@var{port}}
20953 @itemx target extended-remote @code{@var{[host]}:@var{port}}
20954 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20955 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
20956 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
20957 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
20958 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
20959 @cindex @acronym{TCP} port, @code{target remote}
20960 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20961 The @var{host} may be either a host name, a numeric @acronym{IPv4}
20962 address, or a numeric @acronym{IPv6} address (with or without the
20963 square brackets to separate the address from the port); @var{port}
20964 must be a decimal number. The @var{host} could be the target machine
20965 itself, if it is directly connected to the net, or it might be a
20966 terminal server which in turn has a serial line to the target.
20968 For example, to connect to port 2828 on a terminal server named
20972 target remote manyfarms:2828
20975 To connect to port 2828 on a terminal server whose address is
20976 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
20977 square bracket syntax:
20980 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
20984 or explicitly specify the @acronym{IPv6} protocol:
20987 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
20990 This last example may be confusing to the reader, because there is no
20991 visible separation between the hostname and the port number.
20992 Therefore, we recommend the user to provide @acronym{IPv6} addresses
20993 using square brackets for clarity. However, it is important to
20994 mention that for @value{GDBN} there is no ambiguity: the number after
20995 the last colon is considered to be the port number.
20997 If your remote target is actually running on the same machine as your
20998 debugger session (e.g.@: a simulator for your target running on the
20999 same host), you can omit the hostname. For example, to connect to
21000 port 1234 on your local machine:
21003 target remote :1234
21007 Note that the colon is still required here.
21009 @item target remote @code{udp:@var{host}:@var{port}}
21010 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21011 @itemx target remote @code{udp4:@var{host}:@var{port}}
21012 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21013 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21014 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21015 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21016 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21017 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21018 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21019 @cindex @acronym{UDP} port, @code{target remote}
21020 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21021 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21024 target remote udp:manyfarms:2828
21027 When using a @acronym{UDP} connection for remote debugging, you should
21028 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21029 can silently drop packets on busy or unreliable networks, which will
21030 cause havoc with your debugging session.
21032 @item target remote | @var{command}
21033 @itemx target extended-remote | @var{command}
21034 @cindex pipe, @code{target remote} to
21035 Run @var{command} in the background and communicate with it using a
21036 pipe. The @var{command} is a shell command, to be parsed and expanded
21037 by the system's command shell, @code{/bin/sh}; it should expect remote
21038 protocol packets on its standard input, and send replies on its
21039 standard output. You could use this to run a stand-alone simulator
21040 that speaks the remote debugging protocol, to make net connections
21041 using programs like @code{ssh}, or for other similar tricks.
21043 If @var{command} closes its standard output (perhaps by exiting),
21044 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21045 program has already exited, this will have no effect.)
21049 @cindex interrupting remote programs
21050 @cindex remote programs, interrupting
21051 Whenever @value{GDBN} is waiting for the remote program, if you type the
21052 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21053 program. This may or may not succeed, depending in part on the hardware
21054 and the serial drivers the remote system uses. If you type the
21055 interrupt character once again, @value{GDBN} displays this prompt:
21058 Interrupted while waiting for the program.
21059 Give up (and stop debugging it)? (y or n)
21062 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21063 the remote debugging session. (If you decide you want to try again later,
21064 you can use @kbd{target remote} again to connect once more.) If you type
21065 @kbd{n}, @value{GDBN} goes back to waiting.
21067 In @code{target extended-remote} mode, typing @kbd{n} will leave
21068 @value{GDBN} connected to the target.
21071 @kindex detach (remote)
21073 When you have finished debugging the remote program, you can use the
21074 @code{detach} command to release it from @value{GDBN} control.
21075 Detaching from the target normally resumes its execution, but the results
21076 will depend on your particular remote stub. After the @code{detach}
21077 command in @code{target remote} mode, @value{GDBN} is free to connect to
21078 another target. In @code{target extended-remote} mode, @value{GDBN} is
21079 still connected to the target.
21083 The @code{disconnect} command closes the connection to the target, and
21084 the target is generally not resumed. It will wait for @value{GDBN}
21085 (this instance or another one) to connect and continue debugging. After
21086 the @code{disconnect} command, @value{GDBN} is again free to connect to
21089 @cindex send command to remote monitor
21090 @cindex extend @value{GDBN} for remote targets
21091 @cindex add new commands for external monitor
21093 @item monitor @var{cmd}
21094 This command allows you to send arbitrary commands directly to the
21095 remote monitor. Since @value{GDBN} doesn't care about the commands it
21096 sends like this, this command is the way to extend @value{GDBN}---you
21097 can add new commands that only the external monitor will understand
21101 @node File Transfer
21102 @section Sending files to a remote system
21103 @cindex remote target, file transfer
21104 @cindex file transfer
21105 @cindex sending files to remote systems
21107 Some remote targets offer the ability to transfer files over the same
21108 connection used to communicate with @value{GDBN}. This is convenient
21109 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21110 running @code{gdbserver} over a network interface. For other targets,
21111 e.g.@: embedded devices with only a single serial port, this may be
21112 the only way to upload or download files.
21114 Not all remote targets support these commands.
21118 @item remote put @var{hostfile} @var{targetfile}
21119 Copy file @var{hostfile} from the host system (the machine running
21120 @value{GDBN}) to @var{targetfile} on the target system.
21123 @item remote get @var{targetfile} @var{hostfile}
21124 Copy file @var{targetfile} from the target system to @var{hostfile}
21125 on the host system.
21127 @kindex remote delete
21128 @item remote delete @var{targetfile}
21129 Delete @var{targetfile} from the target system.
21134 @section Using the @code{gdbserver} Program
21137 @cindex remote connection without stubs
21138 @code{gdbserver} is a control program for Unix-like systems, which
21139 allows you to connect your program with a remote @value{GDBN} via
21140 @code{target remote} or @code{target extended-remote}---but without
21141 linking in the usual debugging stub.
21143 @code{gdbserver} is not a complete replacement for the debugging stubs,
21144 because it requires essentially the same operating-system facilities
21145 that @value{GDBN} itself does. In fact, a system that can run
21146 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21147 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21148 because it is a much smaller program than @value{GDBN} itself. It is
21149 also easier to port than all of @value{GDBN}, so you may be able to get
21150 started more quickly on a new system by using @code{gdbserver}.
21151 Finally, if you develop code for real-time systems, you may find that
21152 the tradeoffs involved in real-time operation make it more convenient to
21153 do as much development work as possible on another system, for example
21154 by cross-compiling. You can use @code{gdbserver} to make a similar
21155 choice for debugging.
21157 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21158 or a TCP connection, using the standard @value{GDBN} remote serial
21162 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21163 Do not run @code{gdbserver} connected to any public network; a
21164 @value{GDBN} connection to @code{gdbserver} provides access to the
21165 target system with the same privileges as the user running
21169 @anchor{Running gdbserver}
21170 @subsection Running @code{gdbserver}
21171 @cindex arguments, to @code{gdbserver}
21172 @cindex @code{gdbserver}, command-line arguments
21174 Run @code{gdbserver} on the target system. You need a copy of the
21175 program you want to debug, including any libraries it requires.
21176 @code{gdbserver} does not need your program's symbol table, so you can
21177 strip the program if necessary to save space. @value{GDBN} on the host
21178 system does all the symbol handling.
21180 To use the server, you must tell it how to communicate with @value{GDBN};
21181 the name of your program; and the arguments for your program. The usual
21185 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21188 @var{comm} is either a device name (to use a serial line), or a TCP
21189 hostname and portnumber, or @code{-} or @code{stdio} to use
21190 stdin/stdout of @code{gdbserver}.
21191 For example, to debug Emacs with the argument
21192 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21196 target> gdbserver /dev/com1 emacs foo.txt
21199 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21202 To use a TCP connection instead of a serial line:
21205 target> gdbserver host:2345 emacs foo.txt
21208 The only difference from the previous example is the first argument,
21209 specifying that you are communicating with the host @value{GDBN} via
21210 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21211 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21212 (Currently, the @samp{host} part is ignored.) You can choose any number
21213 you want for the port number as long as it does not conflict with any
21214 TCP ports already in use on the target system (for example, @code{23} is
21215 reserved for @code{telnet}).@footnote{If you choose a port number that
21216 conflicts with another service, @code{gdbserver} prints an error message
21217 and exits.} You must use the same port number with the host @value{GDBN}
21218 @code{target remote} command.
21220 The @code{stdio} connection is useful when starting @code{gdbserver}
21224 (gdb) target remote | ssh -T hostname gdbserver - hello
21227 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21228 and we don't want escape-character handling. Ssh does this by default when
21229 a command is provided, the flag is provided to make it explicit.
21230 You could elide it if you want to.
21232 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21233 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21234 display through a pipe connected to gdbserver.
21235 Both @code{stdout} and @code{stderr} use the same pipe.
21237 @anchor{Attaching to a program}
21238 @subsubsection Attaching to a Running Program
21239 @cindex attach to a program, @code{gdbserver}
21240 @cindex @option{--attach}, @code{gdbserver} option
21242 On some targets, @code{gdbserver} can also attach to running programs.
21243 This is accomplished via the @code{--attach} argument. The syntax is:
21246 target> gdbserver --attach @var{comm} @var{pid}
21249 @var{pid} is the process ID of a currently running process. It isn't
21250 necessary to point @code{gdbserver} at a binary for the running process.
21252 In @code{target extended-remote} mode, you can also attach using the
21253 @value{GDBN} attach command
21254 (@pxref{Attaching in Types of Remote Connections}).
21257 You can debug processes by name instead of process ID if your target has the
21258 @code{pidof} utility:
21261 target> gdbserver --attach @var{comm} `pidof @var{program}`
21264 In case more than one copy of @var{program} is running, or @var{program}
21265 has multiple threads, most versions of @code{pidof} support the
21266 @code{-s} option to only return the first process ID.
21268 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21270 This section applies only when @code{gdbserver} is run to listen on a TCP
21273 @code{gdbserver} normally terminates after all of its debugged processes have
21274 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21275 extended-remote}, @code{gdbserver} stays running even with no processes left.
21276 @value{GDBN} normally terminates the spawned debugged process on its exit,
21277 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21278 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21279 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21280 stays running even in the @kbd{target remote} mode.
21282 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21283 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21284 completeness, at most one @value{GDBN} can be connected at a time.
21286 @cindex @option{--once}, @code{gdbserver} option
21287 By default, @code{gdbserver} keeps the listening TCP port open, so that
21288 subsequent connections are possible. However, if you start @code{gdbserver}
21289 with the @option{--once} option, it will stop listening for any further
21290 connection attempts after connecting to the first @value{GDBN} session. This
21291 means no further connections to @code{gdbserver} will be possible after the
21292 first one. It also means @code{gdbserver} will terminate after the first
21293 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21294 connections and even in the @kbd{target extended-remote} mode. The
21295 @option{--once} option allows reusing the same port number for connecting to
21296 multiple instances of @code{gdbserver} running on the same host, since each
21297 instance closes its port after the first connection.
21299 @anchor{Other Command-Line Arguments for gdbserver}
21300 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21302 You can use the @option{--multi} option to start @code{gdbserver} without
21303 specifying a program to debug or a process to attach to. Then you can
21304 attach in @code{target extended-remote} mode and run or attach to a
21305 program. For more information,
21306 @pxref{--multi Option in Types of Remote Connnections}.
21308 @cindex @option{--debug}, @code{gdbserver} option
21309 The @option{--debug} option tells @code{gdbserver} to display extra
21310 status information about the debugging process.
21311 @cindex @option{--remote-debug}, @code{gdbserver} option
21312 The @option{--remote-debug} option tells @code{gdbserver} to display
21313 remote protocol debug output. These options are intended for
21314 @code{gdbserver} development and for bug reports to the developers.
21316 @cindex @option{--debug-format}, @code{gdbserver} option
21317 The @option{--debug-format=option1[,option2,...]} option tells
21318 @code{gdbserver} to include additional information in each output.
21319 Possible options are:
21323 Turn off all extra information in debugging output.
21325 Turn on all extra information in debugging output.
21327 Include a timestamp in each line of debugging output.
21330 Options are processed in order. Thus, for example, if @option{none}
21331 appears last then no additional information is added to debugging output.
21333 @cindex @option{--wrapper}, @code{gdbserver} option
21334 The @option{--wrapper} option specifies a wrapper to launch programs
21335 for debugging. The option should be followed by the name of the
21336 wrapper, then any command-line arguments to pass to the wrapper, then
21337 @kbd{--} indicating the end of the wrapper arguments.
21339 @code{gdbserver} runs the specified wrapper program with a combined
21340 command line including the wrapper arguments, then the name of the
21341 program to debug, then any arguments to the program. The wrapper
21342 runs until it executes your program, and then @value{GDBN} gains control.
21344 You can use any program that eventually calls @code{execve} with
21345 its arguments as a wrapper. Several standard Unix utilities do
21346 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21347 with @code{exec "$@@"} will also work.
21349 For example, you can use @code{env} to pass an environment variable to
21350 the debugged program, without setting the variable in @code{gdbserver}'s
21354 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21357 @cindex @option{--selftest}
21358 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21361 $ gdbserver --selftest
21362 Ran 2 unit tests, 0 failed
21365 These tests are disabled in release.
21366 @subsection Connecting to @code{gdbserver}
21368 The basic procedure for connecting to the remote target is:
21372 Run @value{GDBN} on the host system.
21375 Make sure you have the necessary symbol files
21376 (@pxref{Host and target files}).
21377 Load symbols for your application using the @code{file} command before you
21378 connect. Use @code{set sysroot} to locate target libraries (unless your
21379 @value{GDBN} was compiled with the correct sysroot using
21380 @code{--with-sysroot}).
21383 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21384 For TCP connections, you must start up @code{gdbserver} prior to using
21385 the @code{target} command. Otherwise you may get an error whose
21386 text depends on the host system, but which usually looks something like
21387 @samp{Connection refused}. Don't use the @code{load}
21388 command in @value{GDBN} when using @code{target remote} mode, since the
21389 program is already on the target.
21393 @anchor{Monitor Commands for gdbserver}
21394 @subsection Monitor Commands for @code{gdbserver}
21395 @cindex monitor commands, for @code{gdbserver}
21397 During a @value{GDBN} session using @code{gdbserver}, you can use the
21398 @code{monitor} command to send special requests to @code{gdbserver}.
21399 Here are the available commands.
21403 List the available monitor commands.
21405 @item monitor set debug 0
21406 @itemx monitor set debug 1
21407 Disable or enable general debugging messages.
21409 @item monitor set remote-debug 0
21410 @itemx monitor set remote-debug 1
21411 Disable or enable specific debugging messages associated with the remote
21412 protocol (@pxref{Remote Protocol}).
21414 @item monitor set debug-format option1@r{[},option2,...@r{]}
21415 Specify additional text to add to debugging messages.
21416 Possible options are:
21420 Turn off all extra information in debugging output.
21422 Turn on all extra information in debugging output.
21424 Include a timestamp in each line of debugging output.
21427 Options are processed in order. Thus, for example, if @option{none}
21428 appears last then no additional information is added to debugging output.
21430 @item monitor set libthread-db-search-path [PATH]
21431 @cindex gdbserver, search path for @code{libthread_db}
21432 When this command is issued, @var{path} is a colon-separated list of
21433 directories to search for @code{libthread_db} (@pxref{Threads,,set
21434 libthread-db-search-path}). If you omit @var{path},
21435 @samp{libthread-db-search-path} will be reset to its default value.
21437 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21438 not supported in @code{gdbserver}.
21441 Tell gdbserver to exit immediately. This command should be followed by
21442 @code{disconnect} to close the debugging session. @code{gdbserver} will
21443 detach from any attached processes and kill any processes it created.
21444 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21445 of a multi-process mode debug session.
21449 @subsection Tracepoints support in @code{gdbserver}
21450 @cindex tracepoints support in @code{gdbserver}
21452 On some targets, @code{gdbserver} supports tracepoints, fast
21453 tracepoints and static tracepoints.
21455 For fast or static tracepoints to work, a special library called the
21456 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21457 This library is built and distributed as an integral part of
21458 @code{gdbserver}. In addition, support for static tracepoints
21459 requires building the in-process agent library with static tracepoints
21460 support. At present, the UST (LTTng Userspace Tracer,
21461 @url{http://lttng.org/ust}) tracing engine is supported. This support
21462 is automatically available if UST development headers are found in the
21463 standard include path when @code{gdbserver} is built, or if
21464 @code{gdbserver} was explicitly configured using @option{--with-ust}
21465 to point at such headers. You can explicitly disable the support
21466 using @option{--with-ust=no}.
21468 There are several ways to load the in-process agent in your program:
21471 @item Specifying it as dependency at link time
21473 You can link your program dynamically with the in-process agent
21474 library. On most systems, this is accomplished by adding
21475 @code{-linproctrace} to the link command.
21477 @item Using the system's preloading mechanisms
21479 You can force loading the in-process agent at startup time by using
21480 your system's support for preloading shared libraries. Many Unixes
21481 support the concept of preloading user defined libraries. In most
21482 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21483 in the environment. See also the description of @code{gdbserver}'s
21484 @option{--wrapper} command line option.
21486 @item Using @value{GDBN} to force loading the agent at run time
21488 On some systems, you can force the inferior to load a shared library,
21489 by calling a dynamic loader function in the inferior that takes care
21490 of dynamically looking up and loading a shared library. On most Unix
21491 systems, the function is @code{dlopen}. You'll use the @code{call}
21492 command for that. For example:
21495 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21498 Note that on most Unix systems, for the @code{dlopen} function to be
21499 available, the program needs to be linked with @code{-ldl}.
21502 On systems that have a userspace dynamic loader, like most Unix
21503 systems, when you connect to @code{gdbserver} using @code{target
21504 remote}, you'll find that the program is stopped at the dynamic
21505 loader's entry point, and no shared library has been loaded in the
21506 program's address space yet, including the in-process agent. In that
21507 case, before being able to use any of the fast or static tracepoints
21508 features, you need to let the loader run and load the shared
21509 libraries. The simplest way to do that is to run the program to the
21510 main procedure. E.g., if debugging a C or C@t{++} program, start
21511 @code{gdbserver} like so:
21514 $ gdbserver :9999 myprogram
21517 Start GDB and connect to @code{gdbserver} like so, and run to main:
21521 (@value{GDBP}) target remote myhost:9999
21522 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21523 (@value{GDBP}) b main
21524 (@value{GDBP}) continue
21527 The in-process tracing agent library should now be loaded into the
21528 process; you can confirm it with the @code{info sharedlibrary}
21529 command, which will list @file{libinproctrace.so} as loaded in the
21530 process. You are now ready to install fast tracepoints, list static
21531 tracepoint markers, probe static tracepoints markers, and start
21534 @node Remote Configuration
21535 @section Remote Configuration
21538 @kindex show remote
21539 This section documents the configuration options available when
21540 debugging remote programs. For the options related to the File I/O
21541 extensions of the remote protocol, see @ref{system,
21542 system-call-allowed}.
21545 @item set remoteaddresssize @var{bits}
21546 @cindex address size for remote targets
21547 @cindex bits in remote address
21548 Set the maximum size of address in a memory packet to the specified
21549 number of bits. @value{GDBN} will mask off the address bits above
21550 that number, when it passes addresses to the remote target. The
21551 default value is the number of bits in the target's address.
21553 @item show remoteaddresssize
21554 Show the current value of remote address size in bits.
21556 @item set serial baud @var{n}
21557 @cindex baud rate for remote targets
21558 Set the baud rate for the remote serial I/O to @var{n} baud. The
21559 value is used to set the speed of the serial port used for debugging
21562 @item show serial baud
21563 Show the current speed of the remote connection.
21565 @item set serial parity @var{parity}
21566 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21567 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21569 @item show serial parity
21570 Show the current parity of the serial port.
21572 @item set remotebreak
21573 @cindex interrupt remote programs
21574 @cindex BREAK signal instead of Ctrl-C
21575 @anchor{set remotebreak}
21576 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21577 when you type @kbd{Ctrl-c} to interrupt the program running
21578 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21579 character instead. The default is off, since most remote systems
21580 expect to see @samp{Ctrl-C} as the interrupt signal.
21582 @item show remotebreak
21583 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21584 interrupt the remote program.
21586 @item set remoteflow on
21587 @itemx set remoteflow off
21588 @kindex set remoteflow
21589 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21590 on the serial port used to communicate to the remote target.
21592 @item show remoteflow
21593 @kindex show remoteflow
21594 Show the current setting of hardware flow control.
21596 @item set remotelogbase @var{base}
21597 Set the base (a.k.a.@: radix) of logging serial protocol
21598 communications to @var{base}. Supported values of @var{base} are:
21599 @code{ascii}, @code{octal}, and @code{hex}. The default is
21602 @item show remotelogbase
21603 Show the current setting of the radix for logging remote serial
21606 @item set remotelogfile @var{file}
21607 @cindex record serial communications on file
21608 Record remote serial communications on the named @var{file}. The
21609 default is not to record at all.
21611 @item show remotelogfile
21612 Show the current setting of the file name on which to record the
21613 serial communications.
21615 @item set remotetimeout @var{num}
21616 @cindex timeout for serial communications
21617 @cindex remote timeout
21618 Set the timeout limit to wait for the remote target to respond to
21619 @var{num} seconds. The default is 2 seconds.
21621 @item show remotetimeout
21622 Show the current number of seconds to wait for the remote target
21625 @cindex limit hardware breakpoints and watchpoints
21626 @cindex remote target, limit break- and watchpoints
21627 @anchor{set remote hardware-watchpoint-limit}
21628 @anchor{set remote hardware-breakpoint-limit}
21629 @item set remote hardware-watchpoint-limit @var{limit}
21630 @itemx set remote hardware-breakpoint-limit @var{limit}
21631 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21632 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21633 watchpoints or breakpoints, and @code{unlimited} for unlimited
21634 watchpoints or breakpoints.
21636 @item show remote hardware-watchpoint-limit
21637 @itemx show remote hardware-breakpoint-limit
21638 Show the current limit for the number of hardware watchpoints or
21639 breakpoints that @value{GDBN} can use.
21641 @cindex limit hardware watchpoints length
21642 @cindex remote target, limit watchpoints length
21643 @anchor{set remote hardware-watchpoint-length-limit}
21644 @item set remote hardware-watchpoint-length-limit @var{limit}
21645 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21646 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21647 hardware watchpoints and @code{unlimited} allows watchpoints of any
21650 @item show remote hardware-watchpoint-length-limit
21651 Show the current limit (in bytes) of the maximum length of
21652 a remote hardware watchpoint.
21654 @item set remote exec-file @var{filename}
21655 @itemx show remote exec-file
21656 @anchor{set remote exec-file}
21657 @cindex executable file, for remote target
21658 Select the file used for @code{run} with @code{target
21659 extended-remote}. This should be set to a filename valid on the
21660 target system. If it is not set, the target will use a default
21661 filename (e.g.@: the last program run).
21663 @item set remote interrupt-sequence
21664 @cindex interrupt remote programs
21665 @cindex select Ctrl-C, BREAK or BREAK-g
21666 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21667 @samp{BREAK-g} as the
21668 sequence to the remote target in order to interrupt the execution.
21669 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21670 is high level of serial line for some certain time.
21671 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21672 It is @code{BREAK} signal followed by character @code{g}.
21674 @item show interrupt-sequence
21675 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21676 is sent by @value{GDBN} to interrupt the remote program.
21677 @code{BREAK-g} is BREAK signal followed by @code{g} and
21678 also known as Magic SysRq g.
21680 @item set remote interrupt-on-connect
21681 @cindex send interrupt-sequence on start
21682 Specify whether interrupt-sequence is sent to remote target when
21683 @value{GDBN} connects to it. This is mostly needed when you debug
21684 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21685 which is known as Magic SysRq g in order to connect @value{GDBN}.
21687 @item show interrupt-on-connect
21688 Show whether interrupt-sequence is sent
21689 to remote target when @value{GDBN} connects to it.
21693 @item set tcp auto-retry on
21694 @cindex auto-retry, for remote TCP target
21695 Enable auto-retry for remote TCP connections. This is useful if the remote
21696 debugging agent is launched in parallel with @value{GDBN}; there is a race
21697 condition because the agent may not become ready to accept the connection
21698 before @value{GDBN} attempts to connect. When auto-retry is
21699 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21700 to establish the connection using the timeout specified by
21701 @code{set tcp connect-timeout}.
21703 @item set tcp auto-retry off
21704 Do not auto-retry failed TCP connections.
21706 @item show tcp auto-retry
21707 Show the current auto-retry setting.
21709 @item set tcp connect-timeout @var{seconds}
21710 @itemx set tcp connect-timeout unlimited
21711 @cindex connection timeout, for remote TCP target
21712 @cindex timeout, for remote target connection
21713 Set the timeout for establishing a TCP connection to the remote target to
21714 @var{seconds}. The timeout affects both polling to retry failed connections
21715 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21716 that are merely slow to complete, and represents an approximate cumulative
21717 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21718 @value{GDBN} will keep attempting to establish a connection forever,
21719 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21721 @item show tcp connect-timeout
21722 Show the current connection timeout setting.
21725 @cindex remote packets, enabling and disabling
21726 The @value{GDBN} remote protocol autodetects the packets supported by
21727 your debugging stub. If you need to override the autodetection, you
21728 can use these commands to enable or disable individual packets. Each
21729 packet can be set to @samp{on} (the remote target supports this
21730 packet), @samp{off} (the remote target does not support this packet),
21731 or @samp{auto} (detect remote target support for this packet). They
21732 all default to @samp{auto}. For more information about each packet,
21733 see @ref{Remote Protocol}.
21735 During normal use, you should not have to use any of these commands.
21736 If you do, that may be a bug in your remote debugging stub, or a bug
21737 in @value{GDBN}. You may want to report the problem to the
21738 @value{GDBN} developers.
21740 For each packet @var{name}, the command to enable or disable the
21741 packet is @code{set remote @var{name}-packet}. The available settings
21744 @multitable @columnfractions 0.28 0.32 0.25
21747 @tab Related Features
21749 @item @code{fetch-register}
21751 @tab @code{info registers}
21753 @item @code{set-register}
21757 @item @code{binary-download}
21759 @tab @code{load}, @code{set}
21761 @item @code{read-aux-vector}
21762 @tab @code{qXfer:auxv:read}
21763 @tab @code{info auxv}
21765 @item @code{symbol-lookup}
21766 @tab @code{qSymbol}
21767 @tab Detecting multiple threads
21769 @item @code{attach}
21770 @tab @code{vAttach}
21773 @item @code{verbose-resume}
21775 @tab Stepping or resuming multiple threads
21781 @item @code{software-breakpoint}
21785 @item @code{hardware-breakpoint}
21789 @item @code{write-watchpoint}
21793 @item @code{read-watchpoint}
21797 @item @code{access-watchpoint}
21801 @item @code{pid-to-exec-file}
21802 @tab @code{qXfer:exec-file:read}
21803 @tab @code{attach}, @code{run}
21805 @item @code{target-features}
21806 @tab @code{qXfer:features:read}
21807 @tab @code{set architecture}
21809 @item @code{library-info}
21810 @tab @code{qXfer:libraries:read}
21811 @tab @code{info sharedlibrary}
21813 @item @code{memory-map}
21814 @tab @code{qXfer:memory-map:read}
21815 @tab @code{info mem}
21817 @item @code{read-sdata-object}
21818 @tab @code{qXfer:sdata:read}
21819 @tab @code{print $_sdata}
21821 @item @code{read-spu-object}
21822 @tab @code{qXfer:spu:read}
21823 @tab @code{info spu}
21825 @item @code{write-spu-object}
21826 @tab @code{qXfer:spu:write}
21827 @tab @code{info spu}
21829 @item @code{read-siginfo-object}
21830 @tab @code{qXfer:siginfo:read}
21831 @tab @code{print $_siginfo}
21833 @item @code{write-siginfo-object}
21834 @tab @code{qXfer:siginfo:write}
21835 @tab @code{set $_siginfo}
21837 @item @code{threads}
21838 @tab @code{qXfer:threads:read}
21839 @tab @code{info threads}
21841 @item @code{get-thread-local-@*storage-address}
21842 @tab @code{qGetTLSAddr}
21843 @tab Displaying @code{__thread} variables
21845 @item @code{get-thread-information-block-address}
21846 @tab @code{qGetTIBAddr}
21847 @tab Display MS-Windows Thread Information Block.
21849 @item @code{search-memory}
21850 @tab @code{qSearch:memory}
21853 @item @code{supported-packets}
21854 @tab @code{qSupported}
21855 @tab Remote communications parameters
21857 @item @code{catch-syscalls}
21858 @tab @code{QCatchSyscalls}
21859 @tab @code{catch syscall}
21861 @item @code{pass-signals}
21862 @tab @code{QPassSignals}
21863 @tab @code{handle @var{signal}}
21865 @item @code{program-signals}
21866 @tab @code{QProgramSignals}
21867 @tab @code{handle @var{signal}}
21869 @item @code{hostio-close-packet}
21870 @tab @code{vFile:close}
21871 @tab @code{remote get}, @code{remote put}
21873 @item @code{hostio-open-packet}
21874 @tab @code{vFile:open}
21875 @tab @code{remote get}, @code{remote put}
21877 @item @code{hostio-pread-packet}
21878 @tab @code{vFile:pread}
21879 @tab @code{remote get}, @code{remote put}
21881 @item @code{hostio-pwrite-packet}
21882 @tab @code{vFile:pwrite}
21883 @tab @code{remote get}, @code{remote put}
21885 @item @code{hostio-unlink-packet}
21886 @tab @code{vFile:unlink}
21887 @tab @code{remote delete}
21889 @item @code{hostio-readlink-packet}
21890 @tab @code{vFile:readlink}
21893 @item @code{hostio-fstat-packet}
21894 @tab @code{vFile:fstat}
21897 @item @code{hostio-setfs-packet}
21898 @tab @code{vFile:setfs}
21901 @item @code{noack-packet}
21902 @tab @code{QStartNoAckMode}
21903 @tab Packet acknowledgment
21905 @item @code{osdata}
21906 @tab @code{qXfer:osdata:read}
21907 @tab @code{info os}
21909 @item @code{query-attached}
21910 @tab @code{qAttached}
21911 @tab Querying remote process attach state.
21913 @item @code{trace-buffer-size}
21914 @tab @code{QTBuffer:size}
21915 @tab @code{set trace-buffer-size}
21917 @item @code{trace-status}
21918 @tab @code{qTStatus}
21919 @tab @code{tstatus}
21921 @item @code{traceframe-info}
21922 @tab @code{qXfer:traceframe-info:read}
21923 @tab Traceframe info
21925 @item @code{install-in-trace}
21926 @tab @code{InstallInTrace}
21927 @tab Install tracepoint in tracing
21929 @item @code{disable-randomization}
21930 @tab @code{QDisableRandomization}
21931 @tab @code{set disable-randomization}
21933 @item @code{startup-with-shell}
21934 @tab @code{QStartupWithShell}
21935 @tab @code{set startup-with-shell}
21937 @item @code{environment-hex-encoded}
21938 @tab @code{QEnvironmentHexEncoded}
21939 @tab @code{set environment}
21941 @item @code{environment-unset}
21942 @tab @code{QEnvironmentUnset}
21943 @tab @code{unset environment}
21945 @item @code{environment-reset}
21946 @tab @code{QEnvironmentReset}
21947 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21949 @item @code{set-working-dir}
21950 @tab @code{QSetWorkingDir}
21951 @tab @code{set cwd}
21953 @item @code{conditional-breakpoints-packet}
21954 @tab @code{Z0 and Z1}
21955 @tab @code{Support for target-side breakpoint condition evaluation}
21957 @item @code{multiprocess-extensions}
21958 @tab @code{multiprocess extensions}
21959 @tab Debug multiple processes and remote process PID awareness
21961 @item @code{swbreak-feature}
21962 @tab @code{swbreak stop reason}
21965 @item @code{hwbreak-feature}
21966 @tab @code{hwbreak stop reason}
21969 @item @code{fork-event-feature}
21970 @tab @code{fork stop reason}
21973 @item @code{vfork-event-feature}
21974 @tab @code{vfork stop reason}
21977 @item @code{exec-event-feature}
21978 @tab @code{exec stop reason}
21981 @item @code{thread-events}
21982 @tab @code{QThreadEvents}
21983 @tab Tracking thread lifetime.
21985 @item @code{no-resumed-stop-reply}
21986 @tab @code{no resumed thread left stop reply}
21987 @tab Tracking thread lifetime.
21992 @section Implementing a Remote Stub
21994 @cindex debugging stub, example
21995 @cindex remote stub, example
21996 @cindex stub example, remote debugging
21997 The stub files provided with @value{GDBN} implement the target side of the
21998 communication protocol, and the @value{GDBN} side is implemented in the
21999 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22000 these subroutines to communicate, and ignore the details. (If you're
22001 implementing your own stub file, you can still ignore the details: start
22002 with one of the existing stub files. @file{sparc-stub.c} is the best
22003 organized, and therefore the easiest to read.)
22005 @cindex remote serial debugging, overview
22006 To debug a program running on another machine (the debugging
22007 @dfn{target} machine), you must first arrange for all the usual
22008 prerequisites for the program to run by itself. For example, for a C
22013 A startup routine to set up the C runtime environment; these usually
22014 have a name like @file{crt0}. The startup routine may be supplied by
22015 your hardware supplier, or you may have to write your own.
22018 A C subroutine library to support your program's
22019 subroutine calls, notably managing input and output.
22022 A way of getting your program to the other machine---for example, a
22023 download program. These are often supplied by the hardware
22024 manufacturer, but you may have to write your own from hardware
22028 The next step is to arrange for your program to use a serial port to
22029 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22030 machine). In general terms, the scheme looks like this:
22034 @value{GDBN} already understands how to use this protocol; when everything
22035 else is set up, you can simply use the @samp{target remote} command
22036 (@pxref{Targets,,Specifying a Debugging Target}).
22038 @item On the target,
22039 you must link with your program a few special-purpose subroutines that
22040 implement the @value{GDBN} remote serial protocol. The file containing these
22041 subroutines is called a @dfn{debugging stub}.
22043 On certain remote targets, you can use an auxiliary program
22044 @code{gdbserver} instead of linking a stub into your program.
22045 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22048 The debugging stub is specific to the architecture of the remote
22049 machine; for example, use @file{sparc-stub.c} to debug programs on
22052 @cindex remote serial stub list
22053 These working remote stubs are distributed with @value{GDBN}:
22058 @cindex @file{i386-stub.c}
22061 For Intel 386 and compatible architectures.
22064 @cindex @file{m68k-stub.c}
22065 @cindex Motorola 680x0
22067 For Motorola 680x0 architectures.
22070 @cindex @file{sh-stub.c}
22073 For Renesas SH architectures.
22076 @cindex @file{sparc-stub.c}
22078 For @sc{sparc} architectures.
22080 @item sparcl-stub.c
22081 @cindex @file{sparcl-stub.c}
22084 For Fujitsu @sc{sparclite} architectures.
22088 The @file{README} file in the @value{GDBN} distribution may list other
22089 recently added stubs.
22092 * Stub Contents:: What the stub can do for you
22093 * Bootstrapping:: What you must do for the stub
22094 * Debug Session:: Putting it all together
22097 @node Stub Contents
22098 @subsection What the Stub Can Do for You
22100 @cindex remote serial stub
22101 The debugging stub for your architecture supplies these three
22105 @item set_debug_traps
22106 @findex set_debug_traps
22107 @cindex remote serial stub, initialization
22108 This routine arranges for @code{handle_exception} to run when your
22109 program stops. You must call this subroutine explicitly in your
22110 program's startup code.
22112 @item handle_exception
22113 @findex handle_exception
22114 @cindex remote serial stub, main routine
22115 This is the central workhorse, but your program never calls it
22116 explicitly---the setup code arranges for @code{handle_exception} to
22117 run when a trap is triggered.
22119 @code{handle_exception} takes control when your program stops during
22120 execution (for example, on a breakpoint), and mediates communications
22121 with @value{GDBN} on the host machine. This is where the communications
22122 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22123 representative on the target machine. It begins by sending summary
22124 information on the state of your program, then continues to execute,
22125 retrieving and transmitting any information @value{GDBN} needs, until you
22126 execute a @value{GDBN} command that makes your program resume; at that point,
22127 @code{handle_exception} returns control to your own code on the target
22131 @cindex @code{breakpoint} subroutine, remote
22132 Use this auxiliary subroutine to make your program contain a
22133 breakpoint. Depending on the particular situation, this may be the only
22134 way for @value{GDBN} to get control. For instance, if your target
22135 machine has some sort of interrupt button, you won't need to call this;
22136 pressing the interrupt button transfers control to
22137 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22138 simply receiving characters on the serial port may also trigger a trap;
22139 again, in that situation, you don't need to call @code{breakpoint} from
22140 your own program---simply running @samp{target remote} from the host
22141 @value{GDBN} session gets control.
22143 Call @code{breakpoint} if none of these is true, or if you simply want
22144 to make certain your program stops at a predetermined point for the
22145 start of your debugging session.
22148 @node Bootstrapping
22149 @subsection What You Must Do for the Stub
22151 @cindex remote stub, support routines
22152 The debugging stubs that come with @value{GDBN} are set up for a particular
22153 chip architecture, but they have no information about the rest of your
22154 debugging target machine.
22156 First of all you need to tell the stub how to communicate with the
22160 @item int getDebugChar()
22161 @findex getDebugChar
22162 Write this subroutine to read a single character from the serial port.
22163 It may be identical to @code{getchar} for your target system; a
22164 different name is used to allow you to distinguish the two if you wish.
22166 @item void putDebugChar(int)
22167 @findex putDebugChar
22168 Write this subroutine to write a single character to the serial port.
22169 It may be identical to @code{putchar} for your target system; a
22170 different name is used to allow you to distinguish the two if you wish.
22173 @cindex control C, and remote debugging
22174 @cindex interrupting remote targets
22175 If you want @value{GDBN} to be able to stop your program while it is
22176 running, you need to use an interrupt-driven serial driver, and arrange
22177 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22178 character). That is the character which @value{GDBN} uses to tell the
22179 remote system to stop.
22181 Getting the debugging target to return the proper status to @value{GDBN}
22182 probably requires changes to the standard stub; one quick and dirty way
22183 is to just execute a breakpoint instruction (the ``dirty'' part is that
22184 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22186 Other routines you need to supply are:
22189 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22190 @findex exceptionHandler
22191 Write this function to install @var{exception_address} in the exception
22192 handling tables. You need to do this because the stub does not have any
22193 way of knowing what the exception handling tables on your target system
22194 are like (for example, the processor's table might be in @sc{rom},
22195 containing entries which point to a table in @sc{ram}).
22196 The @var{exception_number} specifies the exception which should be changed;
22197 its meaning is architecture-dependent (for example, different numbers
22198 might represent divide by zero, misaligned access, etc). When this
22199 exception occurs, control should be transferred directly to
22200 @var{exception_address}, and the processor state (stack, registers,
22201 and so on) should be just as it is when a processor exception occurs. So if
22202 you want to use a jump instruction to reach @var{exception_address}, it
22203 should be a simple jump, not a jump to subroutine.
22205 For the 386, @var{exception_address} should be installed as an interrupt
22206 gate so that interrupts are masked while the handler runs. The gate
22207 should be at privilege level 0 (the most privileged level). The
22208 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22209 help from @code{exceptionHandler}.
22211 @item void flush_i_cache()
22212 @findex flush_i_cache
22213 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22214 instruction cache, if any, on your target machine. If there is no
22215 instruction cache, this subroutine may be a no-op.
22217 On target machines that have instruction caches, @value{GDBN} requires this
22218 function to make certain that the state of your program is stable.
22222 You must also make sure this library routine is available:
22225 @item void *memset(void *, int, int)
22227 This is the standard library function @code{memset} that sets an area of
22228 memory to a known value. If you have one of the free versions of
22229 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22230 either obtain it from your hardware manufacturer, or write your own.
22233 If you do not use the GNU C compiler, you may need other standard
22234 library subroutines as well; this varies from one stub to another,
22235 but in general the stubs are likely to use any of the common library
22236 subroutines which @code{@value{NGCC}} generates as inline code.
22239 @node Debug Session
22240 @subsection Putting it All Together
22242 @cindex remote serial debugging summary
22243 In summary, when your program is ready to debug, you must follow these
22248 Make sure you have defined the supporting low-level routines
22249 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22251 @code{getDebugChar}, @code{putDebugChar},
22252 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22256 Insert these lines in your program's startup code, before the main
22257 procedure is called:
22264 On some machines, when a breakpoint trap is raised, the hardware
22265 automatically makes the PC point to the instruction after the
22266 breakpoint. If your machine doesn't do that, you may need to adjust
22267 @code{handle_exception} to arrange for it to return to the instruction
22268 after the breakpoint on this first invocation, so that your program
22269 doesn't keep hitting the initial breakpoint instead of making
22273 For the 680x0 stub only, you need to provide a variable called
22274 @code{exceptionHook}. Normally you just use:
22277 void (*exceptionHook)() = 0;
22281 but if before calling @code{set_debug_traps}, you set it to point to a
22282 function in your program, that function is called when
22283 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22284 error). The function indicated by @code{exceptionHook} is called with
22285 one parameter: an @code{int} which is the exception number.
22288 Compile and link together: your program, the @value{GDBN} debugging stub for
22289 your target architecture, and the supporting subroutines.
22292 Make sure you have a serial connection between your target machine and
22293 the @value{GDBN} host, and identify the serial port on the host.
22296 @c The "remote" target now provides a `load' command, so we should
22297 @c document that. FIXME.
22298 Download your program to your target machine (or get it there by
22299 whatever means the manufacturer provides), and start it.
22302 Start @value{GDBN} on the host, and connect to the target
22303 (@pxref{Connecting,,Connecting to a Remote Target}).
22307 @node Configurations
22308 @chapter Configuration-Specific Information
22310 While nearly all @value{GDBN} commands are available for all native and
22311 cross versions of the debugger, there are some exceptions. This chapter
22312 describes things that are only available in certain configurations.
22314 There are three major categories of configurations: native
22315 configurations, where the host and target are the same, embedded
22316 operating system configurations, which are usually the same for several
22317 different processor architectures, and bare embedded processors, which
22318 are quite different from each other.
22323 * Embedded Processors::
22330 This section describes details specific to particular native
22334 * BSD libkvm Interface:: Debugging BSD kernel memory images
22335 * Process Information:: Process information
22336 * DJGPP Native:: Features specific to the DJGPP port
22337 * Cygwin Native:: Features specific to the Cygwin port
22338 * Hurd Native:: Features specific to @sc{gnu} Hurd
22339 * Darwin:: Features specific to Darwin
22340 * FreeBSD:: Features specific to FreeBSD
22343 @node BSD libkvm Interface
22344 @subsection BSD libkvm Interface
22347 @cindex kernel memory image
22348 @cindex kernel crash dump
22350 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22351 interface that provides a uniform interface for accessing kernel virtual
22352 memory images, including live systems and crash dumps. @value{GDBN}
22353 uses this interface to allow you to debug live kernels and kernel crash
22354 dumps on many native BSD configurations. This is implemented as a
22355 special @code{kvm} debugging target. For debugging a live system, load
22356 the currently running kernel into @value{GDBN} and connect to the
22360 (@value{GDBP}) @b{target kvm}
22363 For debugging crash dumps, provide the file name of the crash dump as an
22367 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22370 Once connected to the @code{kvm} target, the following commands are
22376 Set current context from the @dfn{Process Control Block} (PCB) address.
22379 Set current context from proc address. This command isn't available on
22380 modern FreeBSD systems.
22383 @node Process Information
22384 @subsection Process Information
22386 @cindex examine process image
22387 @cindex process info via @file{/proc}
22389 Some operating systems provide interfaces to fetch additional
22390 information about running processes beyond memory and per-thread
22391 register state. If @value{GDBN} is configured for an operating system
22392 with a supported interface, the command @code{info proc} is available
22393 to report information about the process running your program, or about
22394 any process running on your system.
22396 One supported interface is a facility called @samp{/proc} that can be
22397 used to examine the image of a running process using file-system
22398 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22401 On FreeBSD systems, system control nodes are used to query process
22404 In addition, some systems may provide additional process information
22405 in core files. Note that a core file may include a subset of the
22406 information available from a live process. Process information is
22407 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22414 @itemx info proc @var{process-id}
22415 Summarize available information about a process. If a
22416 process ID is specified by @var{process-id}, display information about
22417 that process; otherwise display information about the program being
22418 debugged. The summary includes the debugged process ID, the command
22419 line used to invoke it, its current working directory, and its
22420 executable file's absolute file name.
22422 On some systems, @var{process-id} can be of the form
22423 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22424 within a process. If the optional @var{pid} part is missing, it means
22425 a thread from the process being debugged (the leading @samp{/} still
22426 needs to be present, or else @value{GDBN} will interpret the number as
22427 a process ID rather than a thread ID).
22429 @item info proc cmdline
22430 @cindex info proc cmdline
22431 Show the original command line of the process. This command is
22432 supported on @sc{gnu}/Linux and FreeBSD.
22434 @item info proc cwd
22435 @cindex info proc cwd
22436 Show the current working directory of the process. This command is
22437 supported on @sc{gnu}/Linux and FreeBSD.
22439 @item info proc exe
22440 @cindex info proc exe
22441 Show the name of executable of the process. This command is supported
22442 on @sc{gnu}/Linux and FreeBSD.
22444 @item info proc files
22445 @cindex info proc files
22446 Show the file descriptors open by the process. For each open file
22447 descriptor, @value{GDBN} shows its number, type (file, directory,
22448 character device, socket), file pointer offset, and the name of the
22449 resource open on the descriptor. The resource name can be a file name
22450 (for files, directories, and devices) or a protocol followed by socket
22451 address (for network connections). This command is supported on
22454 This example shows the open file descriptors for a process using a
22455 tty for standard input and output as well as two network sockets:
22458 (gdb) info proc files 22136
22462 FD Type Offset Flags Name
22463 text file - r-------- /usr/bin/ssh
22464 ctty chr - rw------- /dev/pts/20
22465 cwd dir - r-------- /usr/home/john
22466 root dir - r-------- /
22467 0 chr 0x32933a4 rw------- /dev/pts/20
22468 1 chr 0x32933a4 rw------- /dev/pts/20
22469 2 chr 0x32933a4 rw------- /dev/pts/20
22470 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22471 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22474 @item info proc mappings
22475 @cindex memory address space mappings
22476 Report the memory address space ranges accessible in a process. On
22477 Solaris and FreeBSD systems, each memory range includes information on
22478 whether the process has read, write, or execute access rights to each
22479 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22480 includes the object file which is mapped to that range.
22482 @item info proc stat
22483 @itemx info proc status
22484 @cindex process detailed status information
22485 Show additional process-related information, including the user ID and
22486 group ID; virtual memory usage; the signals that are pending, blocked,
22487 and ignored; its TTY; its consumption of system and user time; its
22488 stack size; its @samp{nice} value; etc. These commands are supported
22489 on @sc{gnu}/Linux and FreeBSD.
22491 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22492 information (type @kbd{man 5 proc} from your shell prompt).
22494 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22497 @item info proc all
22498 Show all the information about the process described under all of the
22499 above @code{info proc} subcommands.
22502 @comment These sub-options of 'info proc' were not included when
22503 @comment procfs.c was re-written. Keep their descriptions around
22504 @comment against the day when someone finds the time to put them back in.
22505 @kindex info proc times
22506 @item info proc times
22507 Starting time, user CPU time, and system CPU time for your program and
22510 @kindex info proc id
22512 Report on the process IDs related to your program: its own process ID,
22513 the ID of its parent, the process group ID, and the session ID.
22516 @item set procfs-trace
22517 @kindex set procfs-trace
22518 @cindex @code{procfs} API calls
22519 This command enables and disables tracing of @code{procfs} API calls.
22521 @item show procfs-trace
22522 @kindex show procfs-trace
22523 Show the current state of @code{procfs} API call tracing.
22525 @item set procfs-file @var{file}
22526 @kindex set procfs-file
22527 Tell @value{GDBN} to write @code{procfs} API trace to the named
22528 @var{file}. @value{GDBN} appends the trace info to the previous
22529 contents of the file. The default is to display the trace on the
22532 @item show procfs-file
22533 @kindex show procfs-file
22534 Show the file to which @code{procfs} API trace is written.
22536 @item proc-trace-entry
22537 @itemx proc-trace-exit
22538 @itemx proc-untrace-entry
22539 @itemx proc-untrace-exit
22540 @kindex proc-trace-entry
22541 @kindex proc-trace-exit
22542 @kindex proc-untrace-entry
22543 @kindex proc-untrace-exit
22544 These commands enable and disable tracing of entries into and exits
22545 from the @code{syscall} interface.
22548 @kindex info pidlist
22549 @cindex process list, QNX Neutrino
22550 For QNX Neutrino only, this command displays the list of all the
22551 processes and all the threads within each process.
22554 @kindex info meminfo
22555 @cindex mapinfo list, QNX Neutrino
22556 For QNX Neutrino only, this command displays the list of all mapinfos.
22560 @subsection Features for Debugging @sc{djgpp} Programs
22561 @cindex @sc{djgpp} debugging
22562 @cindex native @sc{djgpp} debugging
22563 @cindex MS-DOS-specific commands
22566 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22567 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22568 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22569 top of real-mode DOS systems and their emulations.
22571 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22572 defines a few commands specific to the @sc{djgpp} port. This
22573 subsection describes those commands.
22578 This is a prefix of @sc{djgpp}-specific commands which print
22579 information about the target system and important OS structures.
22582 @cindex MS-DOS system info
22583 @cindex free memory information (MS-DOS)
22584 @item info dos sysinfo
22585 This command displays assorted information about the underlying
22586 platform: the CPU type and features, the OS version and flavor, the
22587 DPMI version, and the available conventional and DPMI memory.
22592 @cindex segment descriptor tables
22593 @cindex descriptor tables display
22595 @itemx info dos ldt
22596 @itemx info dos idt
22597 These 3 commands display entries from, respectively, Global, Local,
22598 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22599 tables are data structures which store a descriptor for each segment
22600 that is currently in use. The segment's selector is an index into a
22601 descriptor table; the table entry for that index holds the
22602 descriptor's base address and limit, and its attributes and access
22605 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22606 segment (used for both data and the stack), and a DOS segment (which
22607 allows access to DOS/BIOS data structures and absolute addresses in
22608 conventional memory). However, the DPMI host will usually define
22609 additional segments in order to support the DPMI environment.
22611 @cindex garbled pointers
22612 These commands allow to display entries from the descriptor tables.
22613 Without an argument, all entries from the specified table are
22614 displayed. An argument, which should be an integer expression, means
22615 display a single entry whose index is given by the argument. For
22616 example, here's a convenient way to display information about the
22617 debugged program's data segment:
22620 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22621 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22625 This comes in handy when you want to see whether a pointer is outside
22626 the data segment's limit (i.e.@: @dfn{garbled}).
22628 @cindex page tables display (MS-DOS)
22630 @itemx info dos pte
22631 These two commands display entries from, respectively, the Page
22632 Directory and the Page Tables. Page Directories and Page Tables are
22633 data structures which control how virtual memory addresses are mapped
22634 into physical addresses. A Page Table includes an entry for every
22635 page of memory that is mapped into the program's address space; there
22636 may be several Page Tables, each one holding up to 4096 entries. A
22637 Page Directory has up to 4096 entries, one each for every Page Table
22638 that is currently in use.
22640 Without an argument, @kbd{info dos pde} displays the entire Page
22641 Directory, and @kbd{info dos pte} displays all the entries in all of
22642 the Page Tables. An argument, an integer expression, given to the
22643 @kbd{info dos pde} command means display only that entry from the Page
22644 Directory table. An argument given to the @kbd{info dos pte} command
22645 means display entries from a single Page Table, the one pointed to by
22646 the specified entry in the Page Directory.
22648 @cindex direct memory access (DMA) on MS-DOS
22649 These commands are useful when your program uses @dfn{DMA} (Direct
22650 Memory Access), which needs physical addresses to program the DMA
22653 These commands are supported only with some DPMI servers.
22655 @cindex physical address from linear address
22656 @item info dos address-pte @var{addr}
22657 This command displays the Page Table entry for a specified linear
22658 address. The argument @var{addr} is a linear address which should
22659 already have the appropriate segment's base address added to it,
22660 because this command accepts addresses which may belong to @emph{any}
22661 segment. For example, here's how to display the Page Table entry for
22662 the page where a variable @code{i} is stored:
22665 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22666 @exdent @code{Page Table entry for address 0x11a00d30:}
22667 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22671 This says that @code{i} is stored at offset @code{0xd30} from the page
22672 whose physical base address is @code{0x02698000}, and shows all the
22673 attributes of that page.
22675 Note that you must cast the addresses of variables to a @code{char *},
22676 since otherwise the value of @code{__djgpp_base_address}, the base
22677 address of all variables and functions in a @sc{djgpp} program, will
22678 be added using the rules of C pointer arithmetics: if @code{i} is
22679 declared an @code{int}, @value{GDBN} will add 4 times the value of
22680 @code{__djgpp_base_address} to the address of @code{i}.
22682 Here's another example, it displays the Page Table entry for the
22686 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22687 @exdent @code{Page Table entry for address 0x29110:}
22688 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22692 (The @code{+ 3} offset is because the transfer buffer's address is the
22693 3rd member of the @code{_go32_info_block} structure.) The output
22694 clearly shows that this DPMI server maps the addresses in conventional
22695 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22696 linear (@code{0x29110}) addresses are identical.
22698 This command is supported only with some DPMI servers.
22701 @cindex DOS serial data link, remote debugging
22702 In addition to native debugging, the DJGPP port supports remote
22703 debugging via a serial data link. The following commands are specific
22704 to remote serial debugging in the DJGPP port of @value{GDBN}.
22707 @kindex set com1base
22708 @kindex set com1irq
22709 @kindex set com2base
22710 @kindex set com2irq
22711 @kindex set com3base
22712 @kindex set com3irq
22713 @kindex set com4base
22714 @kindex set com4irq
22715 @item set com1base @var{addr}
22716 This command sets the base I/O port address of the @file{COM1} serial
22719 @item set com1irq @var{irq}
22720 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22721 for the @file{COM1} serial port.
22723 There are similar commands @samp{set com2base}, @samp{set com3irq},
22724 etc.@: for setting the port address and the @code{IRQ} lines for the
22727 @kindex show com1base
22728 @kindex show com1irq
22729 @kindex show com2base
22730 @kindex show com2irq
22731 @kindex show com3base
22732 @kindex show com3irq
22733 @kindex show com4base
22734 @kindex show com4irq
22735 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22736 display the current settings of the base address and the @code{IRQ}
22737 lines used by the COM ports.
22740 @kindex info serial
22741 @cindex DOS serial port status
22742 This command prints the status of the 4 DOS serial ports. For each
22743 port, it prints whether it's active or not, its I/O base address and
22744 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22745 counts of various errors encountered so far.
22749 @node Cygwin Native
22750 @subsection Features for Debugging MS Windows PE Executables
22751 @cindex MS Windows debugging
22752 @cindex native Cygwin debugging
22753 @cindex Cygwin-specific commands
22755 @value{GDBN} supports native debugging of MS Windows programs, including
22756 DLLs with and without symbolic debugging information.
22758 @cindex Ctrl-BREAK, MS-Windows
22759 @cindex interrupt debuggee on MS-Windows
22760 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22761 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22762 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22763 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22764 sequence, which can be used to interrupt the debuggee even if it
22767 There are various additional Cygwin-specific commands, described in
22768 this section. Working with DLLs that have no debugging symbols is
22769 described in @ref{Non-debug DLL Symbols}.
22774 This is a prefix of MS Windows-specific commands which print
22775 information about the target system and important OS structures.
22777 @item info w32 selector
22778 This command displays information returned by
22779 the Win32 API @code{GetThreadSelectorEntry} function.
22780 It takes an optional argument that is evaluated to
22781 a long value to give the information about this given selector.
22782 Without argument, this command displays information
22783 about the six segment registers.
22785 @item info w32 thread-information-block
22786 This command displays thread specific information stored in the
22787 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22788 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22790 @kindex signal-event
22791 @item signal-event @var{id}
22792 This command signals an event with user-provided @var{id}. Used to resume
22793 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22795 To use it, create or edit the following keys in
22796 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22797 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22798 (for x86_64 versions):
22802 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22803 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22804 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22806 The first @code{%ld} will be replaced by the process ID of the
22807 crashing process, the second @code{%ld} will be replaced by the ID of
22808 the event that blocks the crashing process, waiting for @value{GDBN}
22812 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22813 make the system run debugger specified by the Debugger key
22814 automatically, @code{0} will cause a dialog box with ``OK'' and
22815 ``Cancel'' buttons to appear, which allows the user to either
22816 terminate the crashing process (OK) or debug it (Cancel).
22819 @kindex set cygwin-exceptions
22820 @cindex debugging the Cygwin DLL
22821 @cindex Cygwin DLL, debugging
22822 @item set cygwin-exceptions @var{mode}
22823 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22824 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22825 @value{GDBN} will delay recognition of exceptions, and may ignore some
22826 exceptions which seem to be caused by internal Cygwin DLL
22827 ``bookkeeping''. This option is meant primarily for debugging the
22828 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22829 @value{GDBN} users with false @code{SIGSEGV} signals.
22831 @kindex show cygwin-exceptions
22832 @item show cygwin-exceptions
22833 Displays whether @value{GDBN} will break on exceptions that happen
22834 inside the Cygwin DLL itself.
22836 @kindex set new-console
22837 @item set new-console @var{mode}
22838 If @var{mode} is @code{on} the debuggee will
22839 be started in a new console on next start.
22840 If @var{mode} is @code{off}, the debuggee will
22841 be started in the same console as the debugger.
22843 @kindex show new-console
22844 @item show new-console
22845 Displays whether a new console is used
22846 when the debuggee is started.
22848 @kindex set new-group
22849 @item set new-group @var{mode}
22850 This boolean value controls whether the debuggee should
22851 start a new group or stay in the same group as the debugger.
22852 This affects the way the Windows OS handles
22855 @kindex show new-group
22856 @item show new-group
22857 Displays current value of new-group boolean.
22859 @kindex set debugevents
22860 @item set debugevents
22861 This boolean value adds debug output concerning kernel events related
22862 to the debuggee seen by the debugger. This includes events that
22863 signal thread and process creation and exit, DLL loading and
22864 unloading, console interrupts, and debugging messages produced by the
22865 Windows @code{OutputDebugString} API call.
22867 @kindex set debugexec
22868 @item set debugexec
22869 This boolean value adds debug output concerning execute events
22870 (such as resume thread) seen by the debugger.
22872 @kindex set debugexceptions
22873 @item set debugexceptions
22874 This boolean value adds debug output concerning exceptions in the
22875 debuggee seen by the debugger.
22877 @kindex set debugmemory
22878 @item set debugmemory
22879 This boolean value adds debug output concerning debuggee memory reads
22880 and writes by the debugger.
22884 This boolean values specifies whether the debuggee is called
22885 via a shell or directly (default value is on).
22889 Displays if the debuggee will be started with a shell.
22894 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22897 @node Non-debug DLL Symbols
22898 @subsubsection Support for DLLs without Debugging Symbols
22899 @cindex DLLs with no debugging symbols
22900 @cindex Minimal symbols and DLLs
22902 Very often on windows, some of the DLLs that your program relies on do
22903 not include symbolic debugging information (for example,
22904 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22905 symbols in a DLL, it relies on the minimal amount of symbolic
22906 information contained in the DLL's export table. This section
22907 describes working with such symbols, known internally to @value{GDBN} as
22908 ``minimal symbols''.
22910 Note that before the debugged program has started execution, no DLLs
22911 will have been loaded. The easiest way around this problem is simply to
22912 start the program --- either by setting a breakpoint or letting the
22913 program run once to completion.
22915 @subsubsection DLL Name Prefixes
22917 In keeping with the naming conventions used by the Microsoft debugging
22918 tools, DLL export symbols are made available with a prefix based on the
22919 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22920 also entered into the symbol table, so @code{CreateFileA} is often
22921 sufficient. In some cases there will be name clashes within a program
22922 (particularly if the executable itself includes full debugging symbols)
22923 necessitating the use of the fully qualified name when referring to the
22924 contents of the DLL. Use single-quotes around the name to avoid the
22925 exclamation mark (``!'') being interpreted as a language operator.
22927 Note that the internal name of the DLL may be all upper-case, even
22928 though the file name of the DLL is lower-case, or vice-versa. Since
22929 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22930 some confusion. If in doubt, try the @code{info functions} and
22931 @code{info variables} commands or even @code{maint print msymbols}
22932 (@pxref{Symbols}). Here's an example:
22935 (@value{GDBP}) info function CreateFileA
22936 All functions matching regular expression "CreateFileA":
22938 Non-debugging symbols:
22939 0x77e885f4 CreateFileA
22940 0x77e885f4 KERNEL32!CreateFileA
22944 (@value{GDBP}) info function !
22945 All functions matching regular expression "!":
22947 Non-debugging symbols:
22948 0x6100114c cygwin1!__assert
22949 0x61004034 cygwin1!_dll_crt0@@0
22950 0x61004240 cygwin1!dll_crt0(per_process *)
22954 @subsubsection Working with Minimal Symbols
22956 Symbols extracted from a DLL's export table do not contain very much
22957 type information. All that @value{GDBN} can do is guess whether a symbol
22958 refers to a function or variable depending on the linker section that
22959 contains the symbol. Also note that the actual contents of the memory
22960 contained in a DLL are not available unless the program is running. This
22961 means that you cannot examine the contents of a variable or disassemble
22962 a function within a DLL without a running program.
22964 Variables are generally treated as pointers and dereferenced
22965 automatically. For this reason, it is often necessary to prefix a
22966 variable name with the address-of operator (``&'') and provide explicit
22967 type information in the command. Here's an example of the type of
22971 (@value{GDBP}) print 'cygwin1!__argv'
22972 'cygwin1!__argv' has unknown type; cast it to its declared type
22976 (@value{GDBP}) x 'cygwin1!__argv'
22977 'cygwin1!__argv' has unknown type; cast it to its declared type
22980 And two possible solutions:
22983 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22984 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22988 (@value{GDBP}) x/2x &'cygwin1!__argv'
22989 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22990 (@value{GDBP}) x/x 0x10021608
22991 0x10021608: 0x0022fd98
22992 (@value{GDBP}) x/s 0x0022fd98
22993 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22996 Setting a break point within a DLL is possible even before the program
22997 starts execution. However, under these circumstances, @value{GDBN} can't
22998 examine the initial instructions of the function in order to skip the
22999 function's frame set-up code. You can work around this by using ``*&''
23000 to set the breakpoint at a raw memory address:
23003 (@value{GDBP}) break *&'python22!PyOS_Readline'
23004 Breakpoint 1 at 0x1e04eff0
23007 The author of these extensions is not entirely convinced that setting a
23008 break point within a shared DLL like @file{kernel32.dll} is completely
23012 @subsection Commands Specific to @sc{gnu} Hurd Systems
23013 @cindex @sc{gnu} Hurd debugging
23015 This subsection describes @value{GDBN} commands specific to the
23016 @sc{gnu} Hurd native debugging.
23021 @kindex set signals@r{, Hurd command}
23022 @kindex set sigs@r{, Hurd command}
23023 This command toggles the state of inferior signal interception by
23024 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23025 affected by this command. @code{sigs} is a shorthand alias for
23030 @kindex show signals@r{, Hurd command}
23031 @kindex show sigs@r{, Hurd command}
23032 Show the current state of intercepting inferior's signals.
23034 @item set signal-thread
23035 @itemx set sigthread
23036 @kindex set signal-thread
23037 @kindex set sigthread
23038 This command tells @value{GDBN} which thread is the @code{libc} signal
23039 thread. That thread is run when a signal is delivered to a running
23040 process. @code{set sigthread} is the shorthand alias of @code{set
23043 @item show signal-thread
23044 @itemx show sigthread
23045 @kindex show signal-thread
23046 @kindex show sigthread
23047 These two commands show which thread will run when the inferior is
23048 delivered a signal.
23051 @kindex set stopped@r{, Hurd command}
23052 This commands tells @value{GDBN} that the inferior process is stopped,
23053 as with the @code{SIGSTOP} signal. The stopped process can be
23054 continued by delivering a signal to it.
23057 @kindex show stopped@r{, Hurd command}
23058 This command shows whether @value{GDBN} thinks the debuggee is
23061 @item set exceptions
23062 @kindex set exceptions@r{, Hurd command}
23063 Use this command to turn off trapping of exceptions in the inferior.
23064 When exception trapping is off, neither breakpoints nor
23065 single-stepping will work. To restore the default, set exception
23068 @item show exceptions
23069 @kindex show exceptions@r{, Hurd command}
23070 Show the current state of trapping exceptions in the inferior.
23072 @item set task pause
23073 @kindex set task@r{, Hurd commands}
23074 @cindex task attributes (@sc{gnu} Hurd)
23075 @cindex pause current task (@sc{gnu} Hurd)
23076 This command toggles task suspension when @value{GDBN} has control.
23077 Setting it to on takes effect immediately, and the task is suspended
23078 whenever @value{GDBN} gets control. Setting it to off will take
23079 effect the next time the inferior is continued. If this option is set
23080 to off, you can use @code{set thread default pause on} or @code{set
23081 thread pause on} (see below) to pause individual threads.
23083 @item show task pause
23084 @kindex show task@r{, Hurd commands}
23085 Show the current state of task suspension.
23087 @item set task detach-suspend-count
23088 @cindex task suspend count
23089 @cindex detach from task, @sc{gnu} Hurd
23090 This command sets the suspend count the task will be left with when
23091 @value{GDBN} detaches from it.
23093 @item show task detach-suspend-count
23094 Show the suspend count the task will be left with when detaching.
23096 @item set task exception-port
23097 @itemx set task excp
23098 @cindex task exception port, @sc{gnu} Hurd
23099 This command sets the task exception port to which @value{GDBN} will
23100 forward exceptions. The argument should be the value of the @dfn{send
23101 rights} of the task. @code{set task excp} is a shorthand alias.
23103 @item set noninvasive
23104 @cindex noninvasive task options
23105 This command switches @value{GDBN} to a mode that is the least
23106 invasive as far as interfering with the inferior is concerned. This
23107 is the same as using @code{set task pause}, @code{set exceptions}, and
23108 @code{set signals} to values opposite to the defaults.
23110 @item info send-rights
23111 @itemx info receive-rights
23112 @itemx info port-rights
23113 @itemx info port-sets
23114 @itemx info dead-names
23117 @cindex send rights, @sc{gnu} Hurd
23118 @cindex receive rights, @sc{gnu} Hurd
23119 @cindex port rights, @sc{gnu} Hurd
23120 @cindex port sets, @sc{gnu} Hurd
23121 @cindex dead names, @sc{gnu} Hurd
23122 These commands display information about, respectively, send rights,
23123 receive rights, port rights, port sets, and dead names of a task.
23124 There are also shorthand aliases: @code{info ports} for @code{info
23125 port-rights} and @code{info psets} for @code{info port-sets}.
23127 @item set thread pause
23128 @kindex set thread@r{, Hurd command}
23129 @cindex thread properties, @sc{gnu} Hurd
23130 @cindex pause current thread (@sc{gnu} Hurd)
23131 This command toggles current thread suspension when @value{GDBN} has
23132 control. Setting it to on takes effect immediately, and the current
23133 thread is suspended whenever @value{GDBN} gets control. Setting it to
23134 off will take effect the next time the inferior is continued.
23135 Normally, this command has no effect, since when @value{GDBN} has
23136 control, the whole task is suspended. However, if you used @code{set
23137 task pause off} (see above), this command comes in handy to suspend
23138 only the current thread.
23140 @item show thread pause
23141 @kindex show thread@r{, Hurd command}
23142 This command shows the state of current thread suspension.
23144 @item set thread run
23145 This command sets whether the current thread is allowed to run.
23147 @item show thread run
23148 Show whether the current thread is allowed to run.
23150 @item set thread detach-suspend-count
23151 @cindex thread suspend count, @sc{gnu} Hurd
23152 @cindex detach from thread, @sc{gnu} Hurd
23153 This command sets the suspend count @value{GDBN} will leave on a
23154 thread when detaching. This number is relative to the suspend count
23155 found by @value{GDBN} when it notices the thread; use @code{set thread
23156 takeover-suspend-count} to force it to an absolute value.
23158 @item show thread detach-suspend-count
23159 Show the suspend count @value{GDBN} will leave on the thread when
23162 @item set thread exception-port
23163 @itemx set thread excp
23164 Set the thread exception port to which to forward exceptions. This
23165 overrides the port set by @code{set task exception-port} (see above).
23166 @code{set thread excp} is the shorthand alias.
23168 @item set thread takeover-suspend-count
23169 Normally, @value{GDBN}'s thread suspend counts are relative to the
23170 value @value{GDBN} finds when it notices each thread. This command
23171 changes the suspend counts to be absolute instead.
23173 @item set thread default
23174 @itemx show thread default
23175 @cindex thread default settings, @sc{gnu} Hurd
23176 Each of the above @code{set thread} commands has a @code{set thread
23177 default} counterpart (e.g., @code{set thread default pause}, @code{set
23178 thread default exception-port}, etc.). The @code{thread default}
23179 variety of commands sets the default thread properties for all
23180 threads; you can then change the properties of individual threads with
23181 the non-default commands.
23188 @value{GDBN} provides the following commands specific to the Darwin target:
23191 @item set debug darwin @var{num}
23192 @kindex set debug darwin
23193 When set to a non zero value, enables debugging messages specific to
23194 the Darwin support. Higher values produce more verbose output.
23196 @item show debug darwin
23197 @kindex show debug darwin
23198 Show the current state of Darwin messages.
23200 @item set debug mach-o @var{num}
23201 @kindex set debug mach-o
23202 When set to a non zero value, enables debugging messages while
23203 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23204 file format used on Darwin for object and executable files.) Higher
23205 values produce more verbose output. This is a command to diagnose
23206 problems internal to @value{GDBN} and should not be needed in normal
23209 @item show debug mach-o
23210 @kindex show debug mach-o
23211 Show the current state of Mach-O file messages.
23213 @item set mach-exceptions on
23214 @itemx set mach-exceptions off
23215 @kindex set mach-exceptions
23216 On Darwin, faults are first reported as a Mach exception and are then
23217 mapped to a Posix signal. Use this command to turn on trapping of
23218 Mach exceptions in the inferior. This might be sometimes useful to
23219 better understand the cause of a fault. The default is off.
23221 @item show mach-exceptions
23222 @kindex show mach-exceptions
23223 Show the current state of exceptions trapping.
23227 @subsection FreeBSD
23230 When the ABI of a system call is changed in the FreeBSD kernel, this
23231 is implemented by leaving a compatibility system call using the old
23232 ABI at the existing number and allocating a new system call number for
23233 the version using the new ABI. As a convenience, when a system call
23234 is caught by name (@pxref{catch syscall}), compatibility system calls
23237 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23238 system call and catching the @code{kevent} system call by name catches
23242 (@value{GDBP}) catch syscall kevent
23243 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
23249 @section Embedded Operating Systems
23251 This section describes configurations involving the debugging of
23252 embedded operating systems that are available for several different
23255 @value{GDBN} includes the ability to debug programs running on
23256 various real-time operating systems.
23258 @node Embedded Processors
23259 @section Embedded Processors
23261 This section goes into details specific to particular embedded
23264 @cindex send command to simulator
23265 Whenever a specific embedded processor has a simulator, @value{GDBN}
23266 allows to send an arbitrary command to the simulator.
23269 @item sim @var{command}
23270 @kindex sim@r{, a command}
23271 Send an arbitrary @var{command} string to the simulator. Consult the
23272 documentation for the specific simulator in use for information about
23273 acceptable commands.
23278 * ARC:: Synopsys ARC
23280 * M68K:: Motorola M68K
23281 * MicroBlaze:: Xilinx MicroBlaze
23282 * MIPS Embedded:: MIPS Embedded
23283 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23284 * PowerPC Embedded:: PowerPC Embedded
23287 * Super-H:: Renesas Super-H
23291 @subsection Synopsys ARC
23292 @cindex Synopsys ARC
23293 @cindex ARC specific commands
23299 @value{GDBN} provides the following ARC-specific commands:
23302 @item set debug arc
23303 @kindex set debug arc
23304 Control the level of ARC specific debug messages. Use 0 for no messages (the
23305 default), 1 for debug messages, and 2 for even more debug messages.
23307 @item show debug arc
23308 @kindex show debug arc
23309 Show the level of ARC specific debugging in operation.
23311 @item maint print arc arc-instruction @var{address}
23312 @kindex maint print arc arc-instruction
23313 Print internal disassembler information about instruction at a given address.
23320 @value{GDBN} provides the following ARM-specific commands:
23323 @item set arm disassembler
23325 This commands selects from a list of disassembly styles. The
23326 @code{"std"} style is the standard style.
23328 @item show arm disassembler
23330 Show the current disassembly style.
23332 @item set arm apcs32
23333 @cindex ARM 32-bit mode
23334 This command toggles ARM operation mode between 32-bit and 26-bit.
23336 @item show arm apcs32
23337 Display the current usage of the ARM 32-bit mode.
23339 @item set arm fpu @var{fputype}
23340 This command sets the ARM floating-point unit (FPU) type. The
23341 argument @var{fputype} can be one of these:
23345 Determine the FPU type by querying the OS ABI.
23347 Software FPU, with mixed-endian doubles on little-endian ARM
23350 GCC-compiled FPA co-processor.
23352 Software FPU with pure-endian doubles.
23358 Show the current type of the FPU.
23361 This command forces @value{GDBN} to use the specified ABI.
23364 Show the currently used ABI.
23366 @item set arm fallback-mode (arm|thumb|auto)
23367 @value{GDBN} uses the symbol table, when available, to determine
23368 whether instructions are ARM or Thumb. This command controls
23369 @value{GDBN}'s default behavior when the symbol table is not
23370 available. The default is @samp{auto}, which causes @value{GDBN} to
23371 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23374 @item show arm fallback-mode
23375 Show the current fallback instruction mode.
23377 @item set arm force-mode (arm|thumb|auto)
23378 This command overrides use of the symbol table to determine whether
23379 instructions are ARM or Thumb. The default is @samp{auto}, which
23380 causes @value{GDBN} to use the symbol table and then the setting
23381 of @samp{set arm fallback-mode}.
23383 @item show arm force-mode
23384 Show the current forced instruction mode.
23386 @item set debug arm
23387 Toggle whether to display ARM-specific debugging messages from the ARM
23388 target support subsystem.
23390 @item show debug arm
23391 Show whether ARM-specific debugging messages are enabled.
23395 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23396 The @value{GDBN} ARM simulator accepts the following optional arguments.
23399 @item --swi-support=@var{type}
23400 Tell the simulator which SWI interfaces to support. The argument
23401 @var{type} may be a comma separated list of the following values.
23402 The default value is @code{all}.
23417 The Motorola m68k configuration includes ColdFire support.
23420 @subsection MicroBlaze
23421 @cindex Xilinx MicroBlaze
23422 @cindex XMD, Xilinx Microprocessor Debugger
23424 The MicroBlaze is a soft-core processor supported on various Xilinx
23425 FPGAs, such as Spartan or Virtex series. Boards with these processors
23426 usually have JTAG ports which connect to a host system running the Xilinx
23427 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23428 This host system is used to download the configuration bitstream to
23429 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23430 communicates with the target board using the JTAG interface and
23431 presents a @code{gdbserver} interface to the board. By default
23432 @code{xmd} uses port @code{1234}. (While it is possible to change
23433 this default port, it requires the use of undocumented @code{xmd}
23434 commands. Contact Xilinx support if you need to do this.)
23436 Use these GDB commands to connect to the MicroBlaze target processor.
23439 @item target remote :1234
23440 Use this command to connect to the target if you are running @value{GDBN}
23441 on the same system as @code{xmd}.
23443 @item target remote @var{xmd-host}:1234
23444 Use this command to connect to the target if it is connected to @code{xmd}
23445 running on a different system named @var{xmd-host}.
23448 Use this command to download a program to the MicroBlaze target.
23450 @item set debug microblaze @var{n}
23451 Enable MicroBlaze-specific debugging messages if non-zero.
23453 @item show debug microblaze @var{n}
23454 Show MicroBlaze-specific debugging level.
23457 @node MIPS Embedded
23458 @subsection @acronym{MIPS} Embedded
23461 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23464 @item set mipsfpu double
23465 @itemx set mipsfpu single
23466 @itemx set mipsfpu none
23467 @itemx set mipsfpu auto
23468 @itemx show mipsfpu
23469 @kindex set mipsfpu
23470 @kindex show mipsfpu
23471 @cindex @acronym{MIPS} remote floating point
23472 @cindex floating point, @acronym{MIPS} remote
23473 If your target board does not support the @acronym{MIPS} floating point
23474 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23475 need this, you may wish to put the command in your @value{GDBN} init
23476 file). This tells @value{GDBN} how to find the return value of
23477 functions which return floating point values. It also allows
23478 @value{GDBN} to avoid saving the floating point registers when calling
23479 functions on the board. If you are using a floating point coprocessor
23480 with only single precision floating point support, as on the @sc{r4650}
23481 processor, use the command @samp{set mipsfpu single}. The default
23482 double precision floating point coprocessor may be selected using
23483 @samp{set mipsfpu double}.
23485 In previous versions the only choices were double precision or no
23486 floating point, so @samp{set mipsfpu on} will select double precision
23487 and @samp{set mipsfpu off} will select no floating point.
23489 As usual, you can inquire about the @code{mipsfpu} variable with
23490 @samp{show mipsfpu}.
23493 @node OpenRISC 1000
23494 @subsection OpenRISC 1000
23495 @cindex OpenRISC 1000
23498 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23499 mainly provided as a soft-core which can run on Xilinx, Altera and other
23502 @value{GDBN} for OpenRISC supports the below commands when connecting to
23510 Runs the builtin CPU simulator which can run very basic
23511 programs but does not support most hardware functions like MMU.
23512 For more complex use cases the user is advised to run an external
23513 target, and connect using @samp{target remote}.
23515 Example: @code{target sim}
23517 @item set debug or1k
23518 Toggle whether to display OpenRISC-specific debugging messages from the
23519 OpenRISC target support subsystem.
23521 @item show debug or1k
23522 Show whether OpenRISC-specific debugging messages are enabled.
23525 @node PowerPC Embedded
23526 @subsection PowerPC Embedded
23528 @cindex DVC register
23529 @value{GDBN} supports using the DVC (Data Value Compare) register to
23530 implement in hardware simple hardware watchpoint conditions of the form:
23533 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23534 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23537 The DVC register will be automatically used when @value{GDBN} detects
23538 such pattern in a condition expression, and the created watchpoint uses one
23539 debug register (either the @code{exact-watchpoints} option is on and the
23540 variable is scalar, or the variable has a length of one byte). This feature
23541 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23544 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23545 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23546 in which case watchpoints using only one debug register are created when
23547 watching variables of scalar types.
23549 You can create an artificial array to watch an arbitrary memory
23550 region using one of the following commands (@pxref{Expressions}):
23553 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23554 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23557 PowerPC embedded processors support masked watchpoints. See the discussion
23558 about the @code{mask} argument in @ref{Set Watchpoints}.
23560 @cindex ranged breakpoint
23561 PowerPC embedded processors support hardware accelerated
23562 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23563 the inferior whenever it executes an instruction at any address within
23564 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23565 use the @code{break-range} command.
23567 @value{GDBN} provides the following PowerPC-specific commands:
23570 @kindex break-range
23571 @item break-range @var{start-location}, @var{end-location}
23572 Set a breakpoint for an address range given by
23573 @var{start-location} and @var{end-location}, which can specify a function name,
23574 a line number, an offset of lines from the current line or from the start
23575 location, or an address of an instruction (see @ref{Specify Location},
23576 for a list of all the possible ways to specify a @var{location}.)
23577 The breakpoint will stop execution of the inferior whenever it
23578 executes an instruction at any address within the specified range,
23579 (including @var{start-location} and @var{end-location}.)
23581 @kindex set powerpc
23582 @item set powerpc soft-float
23583 @itemx show powerpc soft-float
23584 Force @value{GDBN} to use (or not use) a software floating point calling
23585 convention. By default, @value{GDBN} selects the calling convention based
23586 on the selected architecture and the provided executable file.
23588 @item set powerpc vector-abi
23589 @itemx show powerpc vector-abi
23590 Force @value{GDBN} to use the specified calling convention for vector
23591 arguments and return values. The valid options are @samp{auto};
23592 @samp{generic}, to avoid vector registers even if they are present;
23593 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23594 registers. By default, @value{GDBN} selects the calling convention
23595 based on the selected architecture and the provided executable file.
23597 @item set powerpc exact-watchpoints
23598 @itemx show powerpc exact-watchpoints
23599 Allow @value{GDBN} to use only one debug register when watching a variable
23600 of scalar type, thus assuming that the variable is accessed through the
23601 address of its first byte.
23606 @subsection Atmel AVR
23609 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23610 following AVR-specific commands:
23613 @item info io_registers
23614 @kindex info io_registers@r{, AVR}
23615 @cindex I/O registers (Atmel AVR)
23616 This command displays information about the AVR I/O registers. For
23617 each register, @value{GDBN} prints its number and value.
23624 When configured for debugging CRIS, @value{GDBN} provides the
23625 following CRIS-specific commands:
23628 @item set cris-version @var{ver}
23629 @cindex CRIS version
23630 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23631 The CRIS version affects register names and sizes. This command is useful in
23632 case autodetection of the CRIS version fails.
23634 @item show cris-version
23635 Show the current CRIS version.
23637 @item set cris-dwarf2-cfi
23638 @cindex DWARF-2 CFI and CRIS
23639 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23640 Change to @samp{off} when using @code{gcc-cris} whose version is below
23643 @item show cris-dwarf2-cfi
23644 Show the current state of using DWARF-2 CFI.
23646 @item set cris-mode @var{mode}
23648 Set the current CRIS mode to @var{mode}. It should only be changed when
23649 debugging in guru mode, in which case it should be set to
23650 @samp{guru} (the default is @samp{normal}).
23652 @item show cris-mode
23653 Show the current CRIS mode.
23657 @subsection Renesas Super-H
23660 For the Renesas Super-H processor, @value{GDBN} provides these
23664 @item set sh calling-convention @var{convention}
23665 @kindex set sh calling-convention
23666 Set the calling-convention used when calling functions from @value{GDBN}.
23667 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23668 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23669 convention. If the DWARF-2 information of the called function specifies
23670 that the function follows the Renesas calling convention, the function
23671 is called using the Renesas calling convention. If the calling convention
23672 is set to @samp{renesas}, the Renesas calling convention is always used,
23673 regardless of the DWARF-2 information. This can be used to override the
23674 default of @samp{gcc} if debug information is missing, or the compiler
23675 does not emit the DWARF-2 calling convention entry for a function.
23677 @item show sh calling-convention
23678 @kindex show sh calling-convention
23679 Show the current calling convention setting.
23684 @node Architectures
23685 @section Architectures
23687 This section describes characteristics of architectures that affect
23688 all uses of @value{GDBN} with the architecture, both native and cross.
23695 * HPPA:: HP PA architecture
23696 * SPU:: Cell Broadband Engine SPU architecture
23704 @subsection AArch64
23705 @cindex AArch64 support
23707 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23708 following special commands:
23711 @item set debug aarch64
23712 @kindex set debug aarch64
23713 This command determines whether AArch64 architecture-specific debugging
23714 messages are to be displayed.
23716 @item show debug aarch64
23717 Show whether AArch64 debugging messages are displayed.
23721 @subsubsection AArch64 SVE.
23722 @cindex AArch64 SVE.
23724 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23725 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23726 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23727 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23728 @code{$vg} will be provided. This is the vector granule for the current thread
23729 and represents the number of 64-bit chunks in an SVE @code{z} register.
23731 If the vector length changes, then the @code{$vg} register will be updated,
23732 but the lengths of the @code{z} and @code{p} registers will not change. This
23733 is a known limitation of @value{GDBN} and does not affect the execution of the
23738 @subsection x86 Architecture-specific Issues
23741 @item set struct-convention @var{mode}
23742 @kindex set struct-convention
23743 @cindex struct return convention
23744 @cindex struct/union returned in registers
23745 Set the convention used by the inferior to return @code{struct}s and
23746 @code{union}s from functions to @var{mode}. Possible values of
23747 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23748 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23749 are returned on the stack, while @code{"reg"} means that a
23750 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23751 be returned in a register.
23753 @item show struct-convention
23754 @kindex show struct-convention
23755 Show the current setting of the convention to return @code{struct}s
23760 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23761 @cindex Intel Memory Protection Extensions (MPX).
23763 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23764 @footnote{The register named with capital letters represent the architecture
23765 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23766 which are the lower bound and upper bound. Bounds are effective addresses or
23767 memory locations. The upper bounds are architecturally represented in 1's
23768 complement form. A bound having lower bound = 0, and upper bound = 0
23769 (1's complement of all bits set) will allow access to the entire address space.
23771 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23772 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23773 display the upper bound performing the complement of one operation on the
23774 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23775 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23776 can also be noted that the upper bounds are inclusive.
23778 As an example, assume that the register BND0 holds bounds for a pointer having
23779 access allowed for the range between 0x32 and 0x71. The values present on
23780 bnd0raw and bnd registers are presented as follows:
23783 bnd0raw = @{0x32, 0xffffffff8e@}
23784 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23787 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23788 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23789 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23790 Python, the display includes the memory size, in bits, accessible to
23793 Bounds can also be stored in bounds tables, which are stored in
23794 application memory. These tables store bounds for pointers by specifying
23795 the bounds pointer's value along with its bounds. Evaluating and changing
23796 bounds located in bound tables is therefore interesting while investigating
23797 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23800 @item show mpx bound @var{pointer}
23801 @kindex show mpx bound
23802 Display bounds of the given @var{pointer}.
23804 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23805 @kindex set mpx bound
23806 Set the bounds of a pointer in the bound table.
23807 This command takes three parameters: @var{pointer} is the pointers
23808 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23809 for lower and upper bounds respectively.
23812 When you call an inferior function on an Intel MPX enabled program,
23813 GDB sets the inferior's bound registers to the init (disabled) state
23814 before calling the function. As a consequence, bounds checks for the
23815 pointer arguments passed to the function will always pass.
23817 This is necessary because when you call an inferior function, the
23818 program is usually in the middle of the execution of other function.
23819 Since at that point bound registers are in an arbitrary state, not
23820 clearing them would lead to random bound violations in the called
23823 You can still examine the influence of the bound registers on the
23824 execution of the called function by stopping the execution of the
23825 called function at its prologue, setting bound registers, and
23826 continuing the execution. For example:
23830 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23831 $ print upper (a, b, c, d, 1)
23832 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23834 @{lbound = 0x0, ubound = ffffffff@} : size -1
23837 At this last step the value of bnd0 can be changed for investigation of bound
23838 violations caused along the execution of the call. In order to know how to
23839 set the bound registers or bound table for the call consult the ABI.
23844 See the following section.
23847 @subsection @acronym{MIPS}
23849 @cindex stack on Alpha
23850 @cindex stack on @acronym{MIPS}
23851 @cindex Alpha stack
23852 @cindex @acronym{MIPS} stack
23853 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23854 sometimes requires @value{GDBN} to search backward in the object code to
23855 find the beginning of a function.
23857 @cindex response time, @acronym{MIPS} debugging
23858 To improve response time (especially for embedded applications, where
23859 @value{GDBN} may be restricted to a slow serial line for this search)
23860 you may want to limit the size of this search, using one of these
23864 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23865 @item set heuristic-fence-post @var{limit}
23866 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23867 search for the beginning of a function. A value of @var{0} (the
23868 default) means there is no limit. However, except for @var{0}, the
23869 larger the limit the more bytes @code{heuristic-fence-post} must search
23870 and therefore the longer it takes to run. You should only need to use
23871 this command when debugging a stripped executable.
23873 @item show heuristic-fence-post
23874 Display the current limit.
23878 These commands are available @emph{only} when @value{GDBN} is configured
23879 for debugging programs on Alpha or @acronym{MIPS} processors.
23881 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23885 @item set mips abi @var{arg}
23886 @kindex set mips abi
23887 @cindex set ABI for @acronym{MIPS}
23888 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23889 values of @var{arg} are:
23893 The default ABI associated with the current binary (this is the
23903 @item show mips abi
23904 @kindex show mips abi
23905 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23907 @item set mips compression @var{arg}
23908 @kindex set mips compression
23909 @cindex code compression, @acronym{MIPS}
23910 Tell @value{GDBN} which @acronym{MIPS} compressed
23911 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23912 inferior. @value{GDBN} uses this for code disassembly and other
23913 internal interpretation purposes. This setting is only referred to
23914 when no executable has been associated with the debugging session or
23915 the executable does not provide information about the encoding it uses.
23916 Otherwise this setting is automatically updated from information
23917 provided by the executable.
23919 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23920 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23921 executables containing @acronym{MIPS16} code frequently are not
23922 identified as such.
23924 This setting is ``sticky''; that is, it retains its value across
23925 debugging sessions until reset either explicitly with this command or
23926 implicitly from an executable.
23928 The compiler and/or assembler typically add symbol table annotations to
23929 identify functions compiled for the @acronym{MIPS16} or
23930 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23931 are present, @value{GDBN} uses them in preference to the global
23932 compressed @acronym{ISA} encoding setting.
23934 @item show mips compression
23935 @kindex show mips compression
23936 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23937 @value{GDBN} to debug the inferior.
23940 @itemx show mipsfpu
23941 @xref{MIPS Embedded, set mipsfpu}.
23943 @item set mips mask-address @var{arg}
23944 @kindex set mips mask-address
23945 @cindex @acronym{MIPS} addresses, masking
23946 This command determines whether the most-significant 32 bits of 64-bit
23947 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23948 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23949 setting, which lets @value{GDBN} determine the correct value.
23951 @item show mips mask-address
23952 @kindex show mips mask-address
23953 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23956 @item set remote-mips64-transfers-32bit-regs
23957 @kindex set remote-mips64-transfers-32bit-regs
23958 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23959 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23960 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23961 and 64 bits for other registers, set this option to @samp{on}.
23963 @item show remote-mips64-transfers-32bit-regs
23964 @kindex show remote-mips64-transfers-32bit-regs
23965 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23967 @item set debug mips
23968 @kindex set debug mips
23969 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23970 target code in @value{GDBN}.
23972 @item show debug mips
23973 @kindex show debug mips
23974 Show the current setting of @acronym{MIPS} debugging messages.
23980 @cindex HPPA support
23982 When @value{GDBN} is debugging the HP PA architecture, it provides the
23983 following special commands:
23986 @item set debug hppa
23987 @kindex set debug hppa
23988 This command determines whether HPPA architecture-specific debugging
23989 messages are to be displayed.
23991 @item show debug hppa
23992 Show whether HPPA debugging messages are displayed.
23994 @item maint print unwind @var{address}
23995 @kindex maint print unwind@r{, HPPA}
23996 This command displays the contents of the unwind table entry at the
23997 given @var{address}.
24003 @subsection Cell Broadband Engine SPU architecture
24004 @cindex Cell Broadband Engine
24007 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24008 it provides the following special commands:
24011 @item info spu event
24013 Display SPU event facility status. Shows current event mask
24014 and pending event status.
24016 @item info spu signal
24017 Display SPU signal notification facility status. Shows pending
24018 signal-control word and signal notification mode of both signal
24019 notification channels.
24021 @item info spu mailbox
24022 Display SPU mailbox facility status. Shows all pending entries,
24023 in order of processing, in each of the SPU Write Outbound,
24024 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24027 Display MFC DMA status. Shows all pending commands in the MFC
24028 DMA queue. For each entry, opcode, tag, class IDs, effective
24029 and local store addresses and transfer size are shown.
24031 @item info spu proxydma
24032 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24033 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24034 and local store addresses and transfer size are shown.
24038 When @value{GDBN} is debugging a combined PowerPC/SPU application
24039 on the Cell Broadband Engine, it provides in addition the following
24043 @item set spu stop-on-load @var{arg}
24045 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24046 will give control to the user when a new SPE thread enters its @code{main}
24047 function. The default is @code{off}.
24049 @item show spu stop-on-load
24051 Show whether to stop for new SPE threads.
24053 @item set spu auto-flush-cache @var{arg}
24054 Set whether to automatically flush the software-managed cache. When set to
24055 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24056 cache to be flushed whenever SPE execution stops. This provides a consistent
24057 view of PowerPC memory that is accessed via the cache. If an application
24058 does not use the software-managed cache, this option has no effect.
24060 @item show spu auto-flush-cache
24061 Show whether to automatically flush the software-managed cache.
24066 @subsection PowerPC
24067 @cindex PowerPC architecture
24069 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24070 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24071 numbers stored in the floating point registers. These values must be stored
24072 in two consecutive registers, always starting at an even register like
24073 @code{f0} or @code{f2}.
24075 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24076 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24077 @code{f2} and @code{f3} for @code{$dl1} and so on.
24079 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24080 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24083 @subsection Nios II
24084 @cindex Nios II architecture
24086 When @value{GDBN} is debugging the Nios II architecture,
24087 it provides the following special commands:
24091 @item set debug nios2
24092 @kindex set debug nios2
24093 This command turns on and off debugging messages for the Nios II
24094 target code in @value{GDBN}.
24096 @item show debug nios2
24097 @kindex show debug nios2
24098 Show the current setting of Nios II debugging messages.
24102 @subsection Sparc64
24103 @cindex Sparc64 support
24104 @cindex Application Data Integrity
24105 @subsubsection ADI Support
24107 The M7 processor supports an Application Data Integrity (ADI) feature that
24108 detects invalid data accesses. When software allocates memory and enables
24109 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24110 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24111 the 4-bit version in every cacheline of that data. Hardware saves the latter
24112 in spare bits in the cache and memory hierarchy. On each load and store,
24113 the processor compares the upper 4 VA (virtual address) bits to the
24114 cacheline's version. If there is a mismatch, the processor generates a
24115 version mismatch trap which can be either precise or disrupting. The trap
24116 is an error condition which the kernel delivers to the process as a SIGSEGV
24119 Note that only 64-bit applications can use ADI and need to be built with
24122 Values of the ADI version tags, which are in granularity of a
24123 cacheline (64 bytes), can be viewed or modified.
24127 @kindex adi examine
24128 @item adi (examine | x) [ / @var{n} ] @var{addr}
24130 The @code{adi examine} command displays the value of one ADI version tag per
24133 @var{n} is a decimal integer specifying the number in bytes; the default
24134 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24135 block size, to display.
24137 @var{addr} is the address in user address space where you want @value{GDBN}
24138 to begin displaying the ADI version tags.
24140 Below is an example of displaying ADI versions of variable "shmaddr".
24143 (@value{GDBP}) adi x/100 shmaddr
24144 0xfff800010002c000: 0 0
24148 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24150 The @code{adi assign} command is used to assign new ADI version tag
24153 @var{n} is a decimal integer specifying the number in bytes;
24154 the default is 1. It specifies how much ADI version information, at the
24155 ratio of 1:ADI block size, to modify.
24157 @var{addr} is the address in user address space where you want @value{GDBN}
24158 to begin modifying the ADI version tags.
24160 @var{tag} is the new ADI version tag.
24162 For example, do the following to modify then verify ADI versions of
24163 variable "shmaddr":
24166 (@value{GDBP}) adi a/100 shmaddr = 7
24167 (@value{GDBP}) adi x/100 shmaddr
24168 0xfff800010002c000: 7 7
24175 @cindex S12Z support
24177 When @value{GDBN} is debugging the S12Z architecture,
24178 it provides the following special command:
24181 @item maint info bdccsr
24182 @kindex maint info bdccsr@r{, S12Z}
24183 This command displays the current value of the microprocessor's
24188 @node Controlling GDB
24189 @chapter Controlling @value{GDBN}
24191 You can alter the way @value{GDBN} interacts with you by using the
24192 @code{set} command. For commands controlling how @value{GDBN} displays
24193 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24198 * Editing:: Command editing
24199 * Command History:: Command history
24200 * Screen Size:: Screen size
24201 * Output Styling:: Output styling
24202 * Numbers:: Numbers
24203 * ABI:: Configuring the current ABI
24204 * Auto-loading:: Automatically loading associated files
24205 * Messages/Warnings:: Optional warnings and messages
24206 * Debugging Output:: Optional messages about internal happenings
24207 * Other Misc Settings:: Other Miscellaneous Settings
24215 @value{GDBN} indicates its readiness to read a command by printing a string
24216 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24217 can change the prompt string with the @code{set prompt} command. For
24218 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24219 the prompt in one of the @value{GDBN} sessions so that you can always tell
24220 which one you are talking to.
24222 @emph{Note:} @code{set prompt} does not add a space for you after the
24223 prompt you set. This allows you to set a prompt which ends in a space
24224 or a prompt that does not.
24228 @item set prompt @var{newprompt}
24229 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24231 @kindex show prompt
24233 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24236 Versions of @value{GDBN} that ship with Python scripting enabled have
24237 prompt extensions. The commands for interacting with these extensions
24241 @kindex set extended-prompt
24242 @item set extended-prompt @var{prompt}
24243 Set an extended prompt that allows for substitutions.
24244 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24245 substitution. Any escape sequences specified as part of the prompt
24246 string are replaced with the corresponding strings each time the prompt
24252 set extended-prompt Current working directory: \w (gdb)
24255 Note that when an extended-prompt is set, it takes control of the
24256 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24258 @kindex show extended-prompt
24259 @item show extended-prompt
24260 Prints the extended prompt. Any escape sequences specified as part of
24261 the prompt string with @code{set extended-prompt}, are replaced with the
24262 corresponding strings each time the prompt is displayed.
24266 @section Command Editing
24268 @cindex command line editing
24270 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24271 @sc{gnu} library provides consistent behavior for programs which provide a
24272 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24273 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24274 substitution, and a storage and recall of command history across
24275 debugging sessions.
24277 You may control the behavior of command line editing in @value{GDBN} with the
24278 command @code{set}.
24281 @kindex set editing
24284 @itemx set editing on
24285 Enable command line editing (enabled by default).
24287 @item set editing off
24288 Disable command line editing.
24290 @kindex show editing
24292 Show whether command line editing is enabled.
24295 @ifset SYSTEM_READLINE
24296 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24298 @ifclear SYSTEM_READLINE
24299 @xref{Command Line Editing},
24301 for more details about the Readline
24302 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24303 encouraged to read that chapter.
24305 @node Command History
24306 @section Command History
24307 @cindex command history
24309 @value{GDBN} can keep track of the commands you type during your
24310 debugging sessions, so that you can be certain of precisely what
24311 happened. Use these commands to manage the @value{GDBN} command
24314 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24315 package, to provide the history facility.
24316 @ifset SYSTEM_READLINE
24317 @xref{Using History Interactively, , , history, GNU History Library},
24319 @ifclear SYSTEM_READLINE
24320 @xref{Using History Interactively},
24322 for the detailed description of the History library.
24324 To issue a command to @value{GDBN} without affecting certain aspects of
24325 the state which is seen by users, prefix it with @samp{server }
24326 (@pxref{Server Prefix}). This
24327 means that this command will not affect the command history, nor will it
24328 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24329 pressed on a line by itself.
24331 @cindex @code{server}, command prefix
24332 The server prefix does not affect the recording of values into the value
24333 history; to print a value without recording it into the value history,
24334 use the @code{output} command instead of the @code{print} command.
24336 Here is the description of @value{GDBN} commands related to command
24340 @cindex history substitution
24341 @cindex history file
24342 @kindex set history filename
24343 @cindex @env{GDBHISTFILE}, environment variable
24344 @item set history filename @var{fname}
24345 Set the name of the @value{GDBN} command history file to @var{fname}.
24346 This is the file where @value{GDBN} reads an initial command history
24347 list, and where it writes the command history from this session when it
24348 exits. You can access this list through history expansion or through
24349 the history command editing characters listed below. This file defaults
24350 to the value of the environment variable @code{GDBHISTFILE}, or to
24351 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24354 @cindex save command history
24355 @kindex set history save
24356 @item set history save
24357 @itemx set history save on
24358 Record command history in a file, whose name may be specified with the
24359 @code{set history filename} command. By default, this option is disabled.
24361 @item set history save off
24362 Stop recording command history in a file.
24364 @cindex history size
24365 @kindex set history size
24366 @cindex @env{GDBHISTSIZE}, environment variable
24367 @item set history size @var{size}
24368 @itemx set history size unlimited
24369 Set the number of commands which @value{GDBN} keeps in its history list.
24370 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24371 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24372 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24373 either a negative number or the empty string, then the number of commands
24374 @value{GDBN} keeps in the history list is unlimited.
24376 @cindex remove duplicate history
24377 @kindex set history remove-duplicates
24378 @item set history remove-duplicates @var{count}
24379 @itemx set history remove-duplicates unlimited
24380 Control the removal of duplicate history entries in the command history list.
24381 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24382 history entries and remove the first entry that is a duplicate of the current
24383 entry being added to the command history list. If @var{count} is
24384 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24385 removal of duplicate history entries is disabled.
24387 Only history entries added during the current session are considered for
24388 removal. This option is set to 0 by default.
24392 History expansion assigns special meaning to the character @kbd{!}.
24393 @ifset SYSTEM_READLINE
24394 @xref{Event Designators, , , history, GNU History Library},
24396 @ifclear SYSTEM_READLINE
24397 @xref{Event Designators},
24401 @cindex history expansion, turn on/off
24402 Since @kbd{!} is also the logical not operator in C, history expansion
24403 is off by default. If you decide to enable history expansion with the
24404 @code{set history expansion on} command, you may sometimes need to
24405 follow @kbd{!} (when it is used as logical not, in an expression) with
24406 a space or a tab to prevent it from being expanded. The readline
24407 history facilities do not attempt substitution on the strings
24408 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24410 The commands to control history expansion are:
24413 @item set history expansion on
24414 @itemx set history expansion
24415 @kindex set history expansion
24416 Enable history expansion. History expansion is off by default.
24418 @item set history expansion off
24419 Disable history expansion.
24422 @kindex show history
24424 @itemx show history filename
24425 @itemx show history save
24426 @itemx show history size
24427 @itemx show history expansion
24428 These commands display the state of the @value{GDBN} history parameters.
24429 @code{show history} by itself displays all four states.
24434 @kindex show commands
24435 @cindex show last commands
24436 @cindex display command history
24437 @item show commands
24438 Display the last ten commands in the command history.
24440 @item show commands @var{n}
24441 Print ten commands centered on command number @var{n}.
24443 @item show commands +
24444 Print ten commands just after the commands last printed.
24448 @section Screen Size
24449 @cindex size of screen
24450 @cindex screen size
24453 @cindex pauses in output
24455 Certain commands to @value{GDBN} may produce large amounts of
24456 information output to the screen. To help you read all of it,
24457 @value{GDBN} pauses and asks you for input at the end of each page of
24458 output. Type @key{RET} when you want to see one more page of output,
24459 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24460 without paging for the rest of the current command. Also, the screen
24461 width setting determines when to wrap lines of output. Depending on
24462 what is being printed, @value{GDBN} tries to break the line at a
24463 readable place, rather than simply letting it overflow onto the
24466 Normally @value{GDBN} knows the size of the screen from the terminal
24467 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24468 together with the value of the @code{TERM} environment variable and the
24469 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24470 you can override it with the @code{set height} and @code{set
24477 @kindex show height
24478 @item set height @var{lpp}
24479 @itemx set height unlimited
24481 @itemx set width @var{cpl}
24482 @itemx set width unlimited
24484 These @code{set} commands specify a screen height of @var{lpp} lines and
24485 a screen width of @var{cpl} characters. The associated @code{show}
24486 commands display the current settings.
24488 If you specify a height of either @code{unlimited} or zero lines,
24489 @value{GDBN} does not pause during output no matter how long the
24490 output is. This is useful if output is to a file or to an editor
24493 Likewise, you can specify @samp{set width unlimited} or @samp{set
24494 width 0} to prevent @value{GDBN} from wrapping its output.
24496 @item set pagination on
24497 @itemx set pagination off
24498 @kindex set pagination
24499 Turn the output pagination on or off; the default is on. Turning
24500 pagination off is the alternative to @code{set height unlimited}. Note that
24501 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24502 Options, -batch}) also automatically disables pagination.
24504 @item show pagination
24505 @kindex show pagination
24506 Show the current pagination mode.
24509 @node Output Styling
24510 @section Output Styling
24516 @value{GDBN} can style its output on a capable terminal. This is
24517 enabled by default on most systems, but disabled by default when in
24518 batch mode (@pxref{Mode Options}). Various style settings are available;
24519 and styles can also be disabled entirely.
24522 @item set style enabled @samp{on|off}
24523 Enable or disable all styling. The default is host-dependent, with
24524 most hosts defaulting to @samp{on}.
24526 @item show style enabled
24527 Show the current state of styling.
24529 @item set style sources @samp{on|off}
24530 Enable or disable source code styling. This affects whether source
24531 code, such as the output of the @code{list} command, is styled. Note
24532 that source styling only works if styling in general is enabled, and
24533 if @value{GDBN} was linked with the GNU Source Highlight library. The
24534 default is @samp{on}.
24536 @item show style sources
24537 Show the current state of source code styling.
24540 Subcommands of @code{set style} control specific forms of styling.
24541 These subcommands all follow the same pattern: each style-able object
24542 can be styled with a foreground color, a background color, and an
24545 For example, the style of file names can be controlled using the
24546 @code{set style filename} group of commands:
24549 @item set style filename background @var{color}
24550 Set the background to @var{color}. Valid colors are @samp{none}
24551 (meaning the terminal's default color), @samp{black}, @samp{red},
24552 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24555 @item set style filename foreground @var{color}
24556 Set the foreground to @var{color}. Valid colors are @samp{none}
24557 (meaning the terminal's default color), @samp{black}, @samp{red},
24558 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24561 @item set style filename intensity @var{value}
24562 Set the intensity to @var{value}. Valid intensities are @samp{normal}
24563 (the default), @samp{bold}, and @samp{dim}.
24566 The style-able objects are:
24569 Control the styling of file names. By default, this style's
24570 foreground color is green.
24573 Control the styling of function names. These are managed with the
24574 @code{set style function} family of commands. By default, this
24575 style's foreground color is yellow.
24578 Control the styling of variable names. These are managed with the
24579 @code{set style variable} family of commands. By default, this style's
24580 foreground color is cyan.
24583 Control the styling of addresses. These are managed with the
24584 @code{set style address} family of commands. By default, this style's
24585 foreground color is blue.
24590 @cindex number representation
24591 @cindex entering numbers
24593 You can always enter numbers in octal, decimal, or hexadecimal in
24594 @value{GDBN} by the usual conventions: octal numbers begin with
24595 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24596 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24597 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24598 10; likewise, the default display for numbers---when no particular
24599 format is specified---is base 10. You can change the default base for
24600 both input and output with the commands described below.
24603 @kindex set input-radix
24604 @item set input-radix @var{base}
24605 Set the default base for numeric input. Supported choices
24606 for @var{base} are decimal 8, 10, or 16. The base must itself be
24607 specified either unambiguously or using the current input radix; for
24611 set input-radix 012
24612 set input-radix 10.
24613 set input-radix 0xa
24617 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24618 leaves the input radix unchanged, no matter what it was, since
24619 @samp{10}, being without any leading or trailing signs of its base, is
24620 interpreted in the current radix. Thus, if the current radix is 16,
24621 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24624 @kindex set output-radix
24625 @item set output-radix @var{base}
24626 Set the default base for numeric display. Supported choices
24627 for @var{base} are decimal 8, 10, or 16. The base must itself be
24628 specified either unambiguously or using the current input radix.
24630 @kindex show input-radix
24631 @item show input-radix
24632 Display the current default base for numeric input.
24634 @kindex show output-radix
24635 @item show output-radix
24636 Display the current default base for numeric display.
24638 @item set radix @r{[}@var{base}@r{]}
24642 These commands set and show the default base for both input and output
24643 of numbers. @code{set radix} sets the radix of input and output to
24644 the same base; without an argument, it resets the radix back to its
24645 default value of 10.
24650 @section Configuring the Current ABI
24652 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24653 application automatically. However, sometimes you need to override its
24654 conclusions. Use these commands to manage @value{GDBN}'s view of the
24660 @cindex Newlib OS ABI and its influence on the longjmp handling
24662 One @value{GDBN} configuration can debug binaries for multiple operating
24663 system targets, either via remote debugging or native emulation.
24664 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24665 but you can override its conclusion using the @code{set osabi} command.
24666 One example where this is useful is in debugging of binaries which use
24667 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24668 not have the same identifying marks that the standard C library for your
24671 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24672 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24673 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24674 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24678 Show the OS ABI currently in use.
24681 With no argument, show the list of registered available OS ABI's.
24683 @item set osabi @var{abi}
24684 Set the current OS ABI to @var{abi}.
24687 @cindex float promotion
24689 Generally, the way that an argument of type @code{float} is passed to a
24690 function depends on whether the function is prototyped. For a prototyped
24691 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24692 according to the architecture's convention for @code{float}. For unprototyped
24693 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24694 @code{double} and then passed.
24696 Unfortunately, some forms of debug information do not reliably indicate whether
24697 a function is prototyped. If @value{GDBN} calls a function that is not marked
24698 as prototyped, it consults @kbd{set coerce-float-to-double}.
24701 @kindex set coerce-float-to-double
24702 @item set coerce-float-to-double
24703 @itemx set coerce-float-to-double on
24704 Arguments of type @code{float} will be promoted to @code{double} when passed
24705 to an unprototyped function. This is the default setting.
24707 @item set coerce-float-to-double off
24708 Arguments of type @code{float} will be passed directly to unprototyped
24711 @kindex show coerce-float-to-double
24712 @item show coerce-float-to-double
24713 Show the current setting of promoting @code{float} to @code{double}.
24717 @kindex show cp-abi
24718 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24719 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24720 used to build your application. @value{GDBN} only fully supports
24721 programs with a single C@t{++} ABI; if your program contains code using
24722 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24723 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24724 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24725 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24726 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24727 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24732 Show the C@t{++} ABI currently in use.
24735 With no argument, show the list of supported C@t{++} ABI's.
24737 @item set cp-abi @var{abi}
24738 @itemx set cp-abi auto
24739 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24743 @section Automatically loading associated files
24744 @cindex auto-loading
24746 @value{GDBN} sometimes reads files with commands and settings automatically,
24747 without being explicitly told so by the user. We call this feature
24748 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24749 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24750 results or introduce security risks (e.g., if the file comes from untrusted
24754 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24755 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24757 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24758 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24761 There are various kinds of files @value{GDBN} can automatically load.
24762 In addition to these files, @value{GDBN} supports auto-loading code written
24763 in various extension languages. @xref{Auto-loading extensions}.
24765 Note that loading of these associated files (including the local @file{.gdbinit}
24766 file) requires accordingly configured @code{auto-load safe-path}
24767 (@pxref{Auto-loading safe path}).
24769 For these reasons, @value{GDBN} includes commands and options to let you
24770 control when to auto-load files and which files should be auto-loaded.
24773 @anchor{set auto-load off}
24774 @kindex set auto-load off
24775 @item set auto-load off
24776 Globally disable loading of all auto-loaded files.
24777 You may want to use this command with the @samp{-iex} option
24778 (@pxref{Option -init-eval-command}) such as:
24780 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24783 Be aware that system init file (@pxref{System-wide configuration})
24784 and init files from your home directory (@pxref{Home Directory Init File})
24785 still get read (as they come from generally trusted directories).
24786 To prevent @value{GDBN} from auto-loading even those init files, use the
24787 @option{-nx} option (@pxref{Mode Options}), in addition to
24788 @code{set auto-load no}.
24790 @anchor{show auto-load}
24791 @kindex show auto-load
24792 @item show auto-load
24793 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24797 (gdb) show auto-load
24798 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24799 libthread-db: Auto-loading of inferior specific libthread_db is on.
24800 local-gdbinit: Auto-loading of .gdbinit script from current directory
24802 python-scripts: Auto-loading of Python scripts is on.
24803 safe-path: List of directories from which it is safe to auto-load files
24804 is $debugdir:$datadir/auto-load.
24805 scripts-directory: List of directories from which to load auto-loaded scripts
24806 is $debugdir:$datadir/auto-load.
24809 @anchor{info auto-load}
24810 @kindex info auto-load
24811 @item info auto-load
24812 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24816 (gdb) info auto-load
24819 Yes /home/user/gdb/gdb-gdb.gdb
24820 libthread-db: No auto-loaded libthread-db.
24821 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24825 Yes /home/user/gdb/gdb-gdb.py
24829 These are @value{GDBN} control commands for the auto-loading:
24831 @multitable @columnfractions .5 .5
24832 @item @xref{set auto-load off}.
24833 @tab Disable auto-loading globally.
24834 @item @xref{show auto-load}.
24835 @tab Show setting of all kinds of files.
24836 @item @xref{info auto-load}.
24837 @tab Show state of all kinds of files.
24838 @item @xref{set auto-load gdb-scripts}.
24839 @tab Control for @value{GDBN} command scripts.
24840 @item @xref{show auto-load gdb-scripts}.
24841 @tab Show setting of @value{GDBN} command scripts.
24842 @item @xref{info auto-load gdb-scripts}.
24843 @tab Show state of @value{GDBN} command scripts.
24844 @item @xref{set auto-load python-scripts}.
24845 @tab Control for @value{GDBN} Python scripts.
24846 @item @xref{show auto-load python-scripts}.
24847 @tab Show setting of @value{GDBN} Python scripts.
24848 @item @xref{info auto-load python-scripts}.
24849 @tab Show state of @value{GDBN} Python scripts.
24850 @item @xref{set auto-load guile-scripts}.
24851 @tab Control for @value{GDBN} Guile scripts.
24852 @item @xref{show auto-load guile-scripts}.
24853 @tab Show setting of @value{GDBN} Guile scripts.
24854 @item @xref{info auto-load guile-scripts}.
24855 @tab Show state of @value{GDBN} Guile scripts.
24856 @item @xref{set auto-load scripts-directory}.
24857 @tab Control for @value{GDBN} auto-loaded scripts location.
24858 @item @xref{show auto-load scripts-directory}.
24859 @tab Show @value{GDBN} auto-loaded scripts location.
24860 @item @xref{add-auto-load-scripts-directory}.
24861 @tab Add directory for auto-loaded scripts location list.
24862 @item @xref{set auto-load local-gdbinit}.
24863 @tab Control for init file in the current directory.
24864 @item @xref{show auto-load local-gdbinit}.
24865 @tab Show setting of init file in the current directory.
24866 @item @xref{info auto-load local-gdbinit}.
24867 @tab Show state of init file in the current directory.
24868 @item @xref{set auto-load libthread-db}.
24869 @tab Control for thread debugging library.
24870 @item @xref{show auto-load libthread-db}.
24871 @tab Show setting of thread debugging library.
24872 @item @xref{info auto-load libthread-db}.
24873 @tab Show state of thread debugging library.
24874 @item @xref{set auto-load safe-path}.
24875 @tab Control directories trusted for automatic loading.
24876 @item @xref{show auto-load safe-path}.
24877 @tab Show directories trusted for automatic loading.
24878 @item @xref{add-auto-load-safe-path}.
24879 @tab Add directory trusted for automatic loading.
24882 @node Init File in the Current Directory
24883 @subsection Automatically loading init file in the current directory
24884 @cindex auto-loading init file in the current directory
24886 By default, @value{GDBN} reads and executes the canned sequences of commands
24887 from init file (if any) in the current working directory,
24888 see @ref{Init File in the Current Directory during Startup}.
24890 Note that loading of this local @file{.gdbinit} file also requires accordingly
24891 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24894 @anchor{set auto-load local-gdbinit}
24895 @kindex set auto-load local-gdbinit
24896 @item set auto-load local-gdbinit [on|off]
24897 Enable or disable the auto-loading of canned sequences of commands
24898 (@pxref{Sequences}) found in init file in the current directory.
24900 @anchor{show auto-load local-gdbinit}
24901 @kindex show auto-load local-gdbinit
24902 @item show auto-load local-gdbinit
24903 Show whether auto-loading of canned sequences of commands from init file in the
24904 current directory is enabled or disabled.
24906 @anchor{info auto-load local-gdbinit}
24907 @kindex info auto-load local-gdbinit
24908 @item info auto-load local-gdbinit
24909 Print whether canned sequences of commands from init file in the
24910 current directory have been auto-loaded.
24913 @node libthread_db.so.1 file
24914 @subsection Automatically loading thread debugging library
24915 @cindex auto-loading libthread_db.so.1
24917 This feature is currently present only on @sc{gnu}/Linux native hosts.
24919 @value{GDBN} reads in some cases thread debugging library from places specific
24920 to the inferior (@pxref{set libthread-db-search-path}).
24922 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24923 without checking this @samp{set auto-load libthread-db} switch as system
24924 libraries have to be trusted in general. In all other cases of
24925 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24926 auto-load libthread-db} is enabled before trying to open such thread debugging
24929 Note that loading of this debugging library also requires accordingly configured
24930 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24933 @anchor{set auto-load libthread-db}
24934 @kindex set auto-load libthread-db
24935 @item set auto-load libthread-db [on|off]
24936 Enable or disable the auto-loading of inferior specific thread debugging library.
24938 @anchor{show auto-load libthread-db}
24939 @kindex show auto-load libthread-db
24940 @item show auto-load libthread-db
24941 Show whether auto-loading of inferior specific thread debugging library is
24942 enabled or disabled.
24944 @anchor{info auto-load libthread-db}
24945 @kindex info auto-load libthread-db
24946 @item info auto-load libthread-db
24947 Print the list of all loaded inferior specific thread debugging libraries and
24948 for each such library print list of inferior @var{pid}s using it.
24951 @node Auto-loading safe path
24952 @subsection Security restriction for auto-loading
24953 @cindex auto-loading safe-path
24955 As the files of inferior can come from untrusted source (such as submitted by
24956 an application user) @value{GDBN} does not always load any files automatically.
24957 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24958 directories trusted for loading files not explicitly requested by user.
24959 Each directory can also be a shell wildcard pattern.
24961 If the path is not set properly you will see a warning and the file will not
24966 Reading symbols from /home/user/gdb/gdb...done.
24967 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24968 declined by your `auto-load safe-path' set
24969 to "$debugdir:$datadir/auto-load".
24970 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24971 declined by your `auto-load safe-path' set
24972 to "$debugdir:$datadir/auto-load".
24976 To instruct @value{GDBN} to go ahead and use the init files anyway,
24977 invoke @value{GDBN} like this:
24980 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24983 The list of trusted directories is controlled by the following commands:
24986 @anchor{set auto-load safe-path}
24987 @kindex set auto-load safe-path
24988 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24989 Set the list of directories (and their subdirectories) trusted for automatic
24990 loading and execution of scripts. You can also enter a specific trusted file.
24991 Each directory can also be a shell wildcard pattern; wildcards do not match
24992 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24993 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24994 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24995 its default value as specified during @value{GDBN} compilation.
24997 The list of directories uses path separator (@samp{:} on GNU and Unix
24998 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24999 to the @env{PATH} environment variable.
25001 @anchor{show auto-load safe-path}
25002 @kindex show auto-load safe-path
25003 @item show auto-load safe-path
25004 Show the list of directories trusted for automatic loading and execution of
25007 @anchor{add-auto-load-safe-path}
25008 @kindex add-auto-load-safe-path
25009 @item add-auto-load-safe-path
25010 Add an entry (or list of entries) to the list of directories trusted for
25011 automatic loading and execution of scripts. Multiple entries may be delimited
25012 by the host platform path separator in use.
25015 This variable defaults to what @code{--with-auto-load-dir} has been configured
25016 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25017 substitution applies the same as for @ref{set auto-load scripts-directory}.
25018 The default @code{set auto-load safe-path} value can be also overriden by
25019 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25021 Setting this variable to @file{/} disables this security protection,
25022 corresponding @value{GDBN} configuration option is
25023 @option{--without-auto-load-safe-path}.
25024 This variable is supposed to be set to the system directories writable by the
25025 system superuser only. Users can add their source directories in init files in
25026 their home directories (@pxref{Home Directory Init File}). See also deprecated
25027 init file in the current directory
25028 (@pxref{Init File in the Current Directory during Startup}).
25030 To force @value{GDBN} to load the files it declined to load in the previous
25031 example, you could use one of the following ways:
25034 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25035 Specify this trusted directory (or a file) as additional component of the list.
25036 You have to specify also any existing directories displayed by
25037 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25039 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25040 Specify this directory as in the previous case but just for a single
25041 @value{GDBN} session.
25043 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25044 Disable auto-loading safety for a single @value{GDBN} session.
25045 This assumes all the files you debug during this @value{GDBN} session will come
25046 from trusted sources.
25048 @item @kbd{./configure --without-auto-load-safe-path}
25049 During compilation of @value{GDBN} you may disable any auto-loading safety.
25050 This assumes all the files you will ever debug with this @value{GDBN} come from
25054 On the other hand you can also explicitly forbid automatic files loading which
25055 also suppresses any such warning messages:
25058 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25059 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25061 @item @file{~/.gdbinit}: @samp{set auto-load no}
25062 Disable auto-loading globally for the user
25063 (@pxref{Home Directory Init File}). While it is improbable, you could also
25064 use system init file instead (@pxref{System-wide configuration}).
25067 This setting applies to the file names as entered by user. If no entry matches
25068 @value{GDBN} tries as a last resort to also resolve all the file names into
25069 their canonical form (typically resolving symbolic links) and compare the
25070 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25071 own before starting the comparison so a canonical form of directories is
25072 recommended to be entered.
25074 @node Auto-loading verbose mode
25075 @subsection Displaying files tried for auto-load
25076 @cindex auto-loading verbose mode
25078 For better visibility of all the file locations where you can place scripts to
25079 be auto-loaded with inferior --- or to protect yourself against accidental
25080 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25081 all the files attempted to be loaded. Both existing and non-existing files may
25084 For example the list of directories from which it is safe to auto-load files
25085 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25086 may not be too obvious while setting it up.
25089 (gdb) set debug auto-load on
25090 (gdb) file ~/src/t/true
25091 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25092 for objfile "/tmp/true".
25093 auto-load: Updating directories of "/usr:/opt".
25094 auto-load: Using directory "/usr".
25095 auto-load: Using directory "/opt".
25096 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25097 by your `auto-load safe-path' set to "/usr:/opt".
25101 @anchor{set debug auto-load}
25102 @kindex set debug auto-load
25103 @item set debug auto-load [on|off]
25104 Set whether to print the filenames attempted to be auto-loaded.
25106 @anchor{show debug auto-load}
25107 @kindex show debug auto-load
25108 @item show debug auto-load
25109 Show whether printing of the filenames attempted to be auto-loaded is turned
25113 @node Messages/Warnings
25114 @section Optional Warnings and Messages
25116 @cindex verbose operation
25117 @cindex optional warnings
25118 By default, @value{GDBN} is silent about its inner workings. If you are
25119 running on a slow machine, you may want to use the @code{set verbose}
25120 command. This makes @value{GDBN} tell you when it does a lengthy
25121 internal operation, so you will not think it has crashed.
25123 Currently, the messages controlled by @code{set verbose} are those
25124 which announce that the symbol table for a source file is being read;
25125 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25128 @kindex set verbose
25129 @item set verbose on
25130 Enables @value{GDBN} output of certain informational messages.
25132 @item set verbose off
25133 Disables @value{GDBN} output of certain informational messages.
25135 @kindex show verbose
25137 Displays whether @code{set verbose} is on or off.
25140 By default, if @value{GDBN} encounters bugs in the symbol table of an
25141 object file, it is silent; but if you are debugging a compiler, you may
25142 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25147 @kindex set complaints
25148 @item set complaints @var{limit}
25149 Permits @value{GDBN} to output @var{limit} complaints about each type of
25150 unusual symbols before becoming silent about the problem. Set
25151 @var{limit} to zero to suppress all complaints; set it to a large number
25152 to prevent complaints from being suppressed.
25154 @kindex show complaints
25155 @item show complaints
25156 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25160 @anchor{confirmation requests}
25161 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25162 lot of stupid questions to confirm certain commands. For example, if
25163 you try to run a program which is already running:
25167 The program being debugged has been started already.
25168 Start it from the beginning? (y or n)
25171 If you are willing to unflinchingly face the consequences of your own
25172 commands, you can disable this ``feature'':
25176 @kindex set confirm
25178 @cindex confirmation
25179 @cindex stupid questions
25180 @item set confirm off
25181 Disables confirmation requests. Note that running @value{GDBN} with
25182 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25183 automatically disables confirmation requests.
25185 @item set confirm on
25186 Enables confirmation requests (the default).
25188 @kindex show confirm
25190 Displays state of confirmation requests.
25194 @cindex command tracing
25195 If you need to debug user-defined commands or sourced files you may find it
25196 useful to enable @dfn{command tracing}. In this mode each command will be
25197 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25198 quantity denoting the call depth of each command.
25201 @kindex set trace-commands
25202 @cindex command scripts, debugging
25203 @item set trace-commands on
25204 Enable command tracing.
25205 @item set trace-commands off
25206 Disable command tracing.
25207 @item show trace-commands
25208 Display the current state of command tracing.
25211 @node Debugging Output
25212 @section Optional Messages about Internal Happenings
25213 @cindex optional debugging messages
25215 @value{GDBN} has commands that enable optional debugging messages from
25216 various @value{GDBN} subsystems; normally these commands are of
25217 interest to @value{GDBN} maintainers, or when reporting a bug. This
25218 section documents those commands.
25221 @kindex set exec-done-display
25222 @item set exec-done-display
25223 Turns on or off the notification of asynchronous commands'
25224 completion. When on, @value{GDBN} will print a message when an
25225 asynchronous command finishes its execution. The default is off.
25226 @kindex show exec-done-display
25227 @item show exec-done-display
25228 Displays the current setting of asynchronous command completion
25231 @cindex ARM AArch64
25232 @item set debug aarch64
25233 Turns on or off display of debugging messages related to ARM AArch64.
25234 The default is off.
25236 @item show debug aarch64
25237 Displays the current state of displaying debugging messages related to
25239 @cindex gdbarch debugging info
25240 @cindex architecture debugging info
25241 @item set debug arch
25242 Turns on or off display of gdbarch debugging info. The default is off
25243 @item show debug arch
25244 Displays the current state of displaying gdbarch debugging info.
25245 @item set debug aix-solib
25246 @cindex AIX shared library debugging
25247 Control display of debugging messages from the AIX shared library
25248 support module. The default is off.
25249 @item show debug aix-thread
25250 Show the current state of displaying AIX shared library debugging messages.
25251 @item set debug aix-thread
25252 @cindex AIX threads
25253 Display debugging messages about inner workings of the AIX thread
25255 @item show debug aix-thread
25256 Show the current state of AIX thread debugging info display.
25257 @item set debug check-physname
25259 Check the results of the ``physname'' computation. When reading DWARF
25260 debugging information for C@t{++}, @value{GDBN} attempts to compute
25261 each entity's name. @value{GDBN} can do this computation in two
25262 different ways, depending on exactly what information is present.
25263 When enabled, this setting causes @value{GDBN} to compute the names
25264 both ways and display any discrepancies.
25265 @item show debug check-physname
25266 Show the current state of ``physname'' checking.
25267 @item set debug coff-pe-read
25268 @cindex COFF/PE exported symbols
25269 Control display of debugging messages related to reading of COFF/PE
25270 exported symbols. The default is off.
25271 @item show debug coff-pe-read
25272 Displays the current state of displaying debugging messages related to
25273 reading of COFF/PE exported symbols.
25274 @item set debug dwarf-die
25276 Dump DWARF DIEs after they are read in.
25277 The value is the number of nesting levels to print.
25278 A value of zero turns off the display.
25279 @item show debug dwarf-die
25280 Show the current state of DWARF DIE debugging.
25281 @item set debug dwarf-line
25282 @cindex DWARF Line Tables
25283 Turns on or off display of debugging messages related to reading
25284 DWARF line tables. The default is 0 (off).
25285 A value of 1 provides basic information.
25286 A value greater than 1 provides more verbose information.
25287 @item show debug dwarf-line
25288 Show the current state of DWARF line table debugging.
25289 @item set debug dwarf-read
25290 @cindex DWARF Reading
25291 Turns on or off display of debugging messages related to reading
25292 DWARF debug info. The default is 0 (off).
25293 A value of 1 provides basic information.
25294 A value greater than 1 provides more verbose information.
25295 @item show debug dwarf-read
25296 Show the current state of DWARF reader debugging.
25297 @item set debug displaced
25298 @cindex displaced stepping debugging info
25299 Turns on or off display of @value{GDBN} debugging info for the
25300 displaced stepping support. The default is off.
25301 @item show debug displaced
25302 Displays the current state of displaying @value{GDBN} debugging info
25303 related to displaced stepping.
25304 @item set debug event
25305 @cindex event debugging info
25306 Turns on or off display of @value{GDBN} event debugging info. The
25308 @item show debug event
25309 Displays the current state of displaying @value{GDBN} event debugging
25311 @item set debug expression
25312 @cindex expression debugging info
25313 Turns on or off display of debugging info about @value{GDBN}
25314 expression parsing. The default is off.
25315 @item show debug expression
25316 Displays the current state of displaying debugging info about
25317 @value{GDBN} expression parsing.
25318 @item set debug fbsd-lwp
25319 @cindex FreeBSD LWP debug messages
25320 Turns on or off debugging messages from the FreeBSD LWP debug support.
25321 @item show debug fbsd-lwp
25322 Show the current state of FreeBSD LWP debugging messages.
25323 @item set debug fbsd-nat
25324 @cindex FreeBSD native target debug messages
25325 Turns on or off debugging messages from the FreeBSD native target.
25326 @item show debug fbsd-nat
25327 Show the current state of FreeBSD native target debugging messages.
25328 @item set debug frame
25329 @cindex frame debugging info
25330 Turns on or off display of @value{GDBN} frame debugging info. The
25332 @item show debug frame
25333 Displays the current state of displaying @value{GDBN} frame debugging
25335 @item set debug gnu-nat
25336 @cindex @sc{gnu}/Hurd debug messages
25337 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25338 @item show debug gnu-nat
25339 Show the current state of @sc{gnu}/Hurd debugging messages.
25340 @item set debug infrun
25341 @cindex inferior debugging info
25342 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25343 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25344 for implementing operations such as single-stepping the inferior.
25345 @item show debug infrun
25346 Displays the current state of @value{GDBN} inferior debugging.
25347 @item set debug jit
25348 @cindex just-in-time compilation, debugging messages
25349 Turn on or off debugging messages from JIT debug support.
25350 @item show debug jit
25351 Displays the current state of @value{GDBN} JIT debugging.
25352 @item set debug lin-lwp
25353 @cindex @sc{gnu}/Linux LWP debug messages
25354 @cindex Linux lightweight processes
25355 Turn on or off debugging messages from the Linux LWP debug support.
25356 @item show debug lin-lwp
25357 Show the current state of Linux LWP debugging messages.
25358 @item set debug linux-namespaces
25359 @cindex @sc{gnu}/Linux namespaces debug messages
25360 Turn on or off debugging messages from the Linux namespaces debug support.
25361 @item show debug linux-namespaces
25362 Show the current state of Linux namespaces debugging messages.
25363 @item set debug mach-o
25364 @cindex Mach-O symbols processing
25365 Control display of debugging messages related to Mach-O symbols
25366 processing. The default is off.
25367 @item show debug mach-o
25368 Displays the current state of displaying debugging messages related to
25369 reading of COFF/PE exported symbols.
25370 @item set debug notification
25371 @cindex remote async notification debugging info
25372 Turn on or off debugging messages about remote async notification.
25373 The default is off.
25374 @item show debug notification
25375 Displays the current state of remote async notification debugging messages.
25376 @item set debug observer
25377 @cindex observer debugging info
25378 Turns on or off display of @value{GDBN} observer debugging. This
25379 includes info such as the notification of observable events.
25380 @item show debug observer
25381 Displays the current state of observer debugging.
25382 @item set debug overload
25383 @cindex C@t{++} overload debugging info
25384 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25385 info. This includes info such as ranking of functions, etc. The default
25387 @item show debug overload
25388 Displays the current state of displaying @value{GDBN} C@t{++} overload
25390 @cindex expression parser, debugging info
25391 @cindex debug expression parser
25392 @item set debug parser
25393 Turns on or off the display of expression parser debugging output.
25394 Internally, this sets the @code{yydebug} variable in the expression
25395 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25396 details. The default is off.
25397 @item show debug parser
25398 Show the current state of expression parser debugging.
25399 @cindex packets, reporting on stdout
25400 @cindex serial connections, debugging
25401 @cindex debug remote protocol
25402 @cindex remote protocol debugging
25403 @cindex display remote packets
25404 @item set debug remote
25405 Turns on or off display of reports on all packets sent back and forth across
25406 the serial line to the remote machine. The info is printed on the
25407 @value{GDBN} standard output stream. The default is off.
25408 @item show debug remote
25409 Displays the state of display of remote packets.
25411 @item set debug separate-debug-file
25412 Turns on or off display of debug output about separate debug file search.
25413 @item show debug separate-debug-file
25414 Displays the state of separate debug file search debug output.
25416 @item set debug serial
25417 Turns on or off display of @value{GDBN} serial debugging info. The
25419 @item show debug serial
25420 Displays the current state of displaying @value{GDBN} serial debugging
25422 @item set debug solib-frv
25423 @cindex FR-V shared-library debugging
25424 Turn on or off debugging messages for FR-V shared-library code.
25425 @item show debug solib-frv
25426 Display the current state of FR-V shared-library code debugging
25428 @item set debug symbol-lookup
25429 @cindex symbol lookup
25430 Turns on or off display of debugging messages related to symbol lookup.
25431 The default is 0 (off).
25432 A value of 1 provides basic information.
25433 A value greater than 1 provides more verbose information.
25434 @item show debug symbol-lookup
25435 Show the current state of symbol lookup debugging messages.
25436 @item set debug symfile
25437 @cindex symbol file functions
25438 Turns on or off display of debugging messages related to symbol file functions.
25439 The default is off. @xref{Files}.
25440 @item show debug symfile
25441 Show the current state of symbol file debugging messages.
25442 @item set debug symtab-create
25443 @cindex symbol table creation
25444 Turns on or off display of debugging messages related to symbol table creation.
25445 The default is 0 (off).
25446 A value of 1 provides basic information.
25447 A value greater than 1 provides more verbose information.
25448 @item show debug symtab-create
25449 Show the current state of symbol table creation debugging.
25450 @item set debug target
25451 @cindex target debugging info
25452 Turns on or off display of @value{GDBN} target debugging info. This info
25453 includes what is going on at the target level of GDB, as it happens. The
25454 default is 0. Set it to 1 to track events, and to 2 to also track the
25455 value of large memory transfers.
25456 @item show debug target
25457 Displays the current state of displaying @value{GDBN} target debugging
25459 @item set debug timestamp
25460 @cindex timestampping debugging info
25461 Turns on or off display of timestamps with @value{GDBN} debugging info.
25462 When enabled, seconds and microseconds are displayed before each debugging
25464 @item show debug timestamp
25465 Displays the current state of displaying timestamps with @value{GDBN}
25467 @item set debug varobj
25468 @cindex variable object debugging info
25469 Turns on or off display of @value{GDBN} variable object debugging
25470 info. The default is off.
25471 @item show debug varobj
25472 Displays the current state of displaying @value{GDBN} variable object
25474 @item set debug xml
25475 @cindex XML parser debugging
25476 Turn on or off debugging messages for built-in XML parsers.
25477 @item show debug xml
25478 Displays the current state of XML debugging messages.
25481 @node Other Misc Settings
25482 @section Other Miscellaneous Settings
25483 @cindex miscellaneous settings
25486 @kindex set interactive-mode
25487 @item set interactive-mode
25488 If @code{on}, forces @value{GDBN} to assume that GDB was started
25489 in a terminal. In practice, this means that @value{GDBN} should wait
25490 for the user to answer queries generated by commands entered at
25491 the command prompt. If @code{off}, forces @value{GDBN} to operate
25492 in the opposite mode, and it uses the default answers to all queries.
25493 If @code{auto} (the default), @value{GDBN} tries to determine whether
25494 its standard input is a terminal, and works in interactive-mode if it
25495 is, non-interactively otherwise.
25497 In the vast majority of cases, the debugger should be able to guess
25498 correctly which mode should be used. But this setting can be useful
25499 in certain specific cases, such as running a MinGW @value{GDBN}
25500 inside a cygwin window.
25502 @kindex show interactive-mode
25503 @item show interactive-mode
25504 Displays whether the debugger is operating in interactive mode or not.
25507 @node Extending GDB
25508 @chapter Extending @value{GDBN}
25509 @cindex extending GDB
25511 @value{GDBN} provides several mechanisms for extension.
25512 @value{GDBN} also provides the ability to automatically load
25513 extensions when it reads a file for debugging. This allows the
25514 user to automatically customize @value{GDBN} for the program
25518 * Sequences:: Canned Sequences of @value{GDBN} Commands
25519 * Python:: Extending @value{GDBN} using Python
25520 * Guile:: Extending @value{GDBN} using Guile
25521 * Auto-loading extensions:: Automatically loading extensions
25522 * Multiple Extension Languages:: Working with multiple extension languages
25523 * Aliases:: Creating new spellings of existing commands
25526 To facilitate the use of extension languages, @value{GDBN} is capable
25527 of evaluating the contents of a file. When doing so, @value{GDBN}
25528 can recognize which extension language is being used by looking at
25529 the filename extension. Files with an unrecognized filename extension
25530 are always treated as a @value{GDBN} Command Files.
25531 @xref{Command Files,, Command files}.
25533 You can control how @value{GDBN} evaluates these files with the following
25537 @kindex set script-extension
25538 @kindex show script-extension
25539 @item set script-extension off
25540 All scripts are always evaluated as @value{GDBN} Command Files.
25542 @item set script-extension soft
25543 The debugger determines the scripting language based on filename
25544 extension. If this scripting language is supported, @value{GDBN}
25545 evaluates the script using that language. Otherwise, it evaluates
25546 the file as a @value{GDBN} Command File.
25548 @item set script-extension strict
25549 The debugger determines the scripting language based on filename
25550 extension, and evaluates the script using that language. If the
25551 language is not supported, then the evaluation fails.
25553 @item show script-extension
25554 Display the current value of the @code{script-extension} option.
25559 @section Canned Sequences of Commands
25561 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25562 Command Lists}), @value{GDBN} provides two ways to store sequences of
25563 commands for execution as a unit: user-defined commands and command
25567 * Define:: How to define your own commands
25568 * Hooks:: Hooks for user-defined commands
25569 * Command Files:: How to write scripts of commands to be stored in a file
25570 * Output:: Commands for controlled output
25571 * Auto-loading sequences:: Controlling auto-loaded command files
25575 @subsection User-defined Commands
25577 @cindex user-defined command
25578 @cindex arguments, to user-defined commands
25579 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25580 which you assign a new name as a command. This is done with the
25581 @code{define} command. User commands may accept an unlimited number of arguments
25582 separated by whitespace. Arguments are accessed within the user command
25583 via @code{$arg0@dots{}$argN}. A trivial example:
25587 print $arg0 + $arg1 + $arg2
25592 To execute the command use:
25599 This defines the command @code{adder}, which prints the sum of
25600 its three arguments. Note the arguments are text substitutions, so they may
25601 reference variables, use complex expressions, or even perform inferior
25604 @cindex argument count in user-defined commands
25605 @cindex how many arguments (user-defined commands)
25606 In addition, @code{$argc} may be used to find out how many arguments have
25612 print $arg0 + $arg1
25615 print $arg0 + $arg1 + $arg2
25620 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25621 to process a variable number of arguments:
25628 eval "set $sum = $sum + $arg%d", $i
25638 @item define @var{commandname}
25639 Define a command named @var{commandname}. If there is already a command
25640 by that name, you are asked to confirm that you want to redefine it.
25641 The argument @var{commandname} may be a bare command name consisting of letters,
25642 numbers, dashes, and underscores. It may also start with any predefined
25643 prefix command. For example, @samp{define target my-target} creates
25644 a user-defined @samp{target my-target} command.
25646 The definition of the command is made up of other @value{GDBN} command lines,
25647 which are given following the @code{define} command. The end of these
25648 commands is marked by a line containing @code{end}.
25651 @kindex end@r{ (user-defined commands)}
25652 @item document @var{commandname}
25653 Document the user-defined command @var{commandname}, so that it can be
25654 accessed by @code{help}. The command @var{commandname} must already be
25655 defined. This command reads lines of documentation just as @code{define}
25656 reads the lines of the command definition, ending with @code{end}.
25657 After the @code{document} command is finished, @code{help} on command
25658 @var{commandname} displays the documentation you have written.
25660 You may use the @code{document} command again to change the
25661 documentation of a command. Redefining the command with @code{define}
25662 does not change the documentation.
25664 @kindex dont-repeat
25665 @cindex don't repeat command
25667 Used inside a user-defined command, this tells @value{GDBN} that this
25668 command should not be repeated when the user hits @key{RET}
25669 (@pxref{Command Syntax, repeat last command}).
25671 @kindex help user-defined
25672 @item help user-defined
25673 List all user-defined commands and all python commands defined in class
25674 COMAND_USER. The first line of the documentation or docstring is
25679 @itemx show user @var{commandname}
25680 Display the @value{GDBN} commands used to define @var{commandname} (but
25681 not its documentation). If no @var{commandname} is given, display the
25682 definitions for all user-defined commands.
25683 This does not work for user-defined python commands.
25685 @cindex infinite recursion in user-defined commands
25686 @kindex show max-user-call-depth
25687 @kindex set max-user-call-depth
25688 @item show max-user-call-depth
25689 @itemx set max-user-call-depth
25690 The value of @code{max-user-call-depth} controls how many recursion
25691 levels are allowed in user-defined commands before @value{GDBN} suspects an
25692 infinite recursion and aborts the command.
25693 This does not apply to user-defined python commands.
25696 In addition to the above commands, user-defined commands frequently
25697 use control flow commands, described in @ref{Command Files}.
25699 When user-defined commands are executed, the
25700 commands of the definition are not printed. An error in any command
25701 stops execution of the user-defined command.
25703 If used interactively, commands that would ask for confirmation proceed
25704 without asking when used inside a user-defined command. Many @value{GDBN}
25705 commands that normally print messages to say what they are doing omit the
25706 messages when used in a user-defined command.
25709 @subsection User-defined Command Hooks
25710 @cindex command hooks
25711 @cindex hooks, for commands
25712 @cindex hooks, pre-command
25715 You may define @dfn{hooks}, which are a special kind of user-defined
25716 command. Whenever you run the command @samp{foo}, if the user-defined
25717 command @samp{hook-foo} exists, it is executed (with no arguments)
25718 before that command.
25720 @cindex hooks, post-command
25722 A hook may also be defined which is run after the command you executed.
25723 Whenever you run the command @samp{foo}, if the user-defined command
25724 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25725 that command. Post-execution hooks may exist simultaneously with
25726 pre-execution hooks, for the same command.
25728 It is valid for a hook to call the command which it hooks. If this
25729 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25731 @c It would be nice if hookpost could be passed a parameter indicating
25732 @c if the command it hooks executed properly or not. FIXME!
25734 @kindex stop@r{, a pseudo-command}
25735 In addition, a pseudo-command, @samp{stop} exists. Defining
25736 (@samp{hook-stop}) makes the associated commands execute every time
25737 execution stops in your program: before breakpoint commands are run,
25738 displays are printed, or the stack frame is printed.
25740 For example, to ignore @code{SIGALRM} signals while
25741 single-stepping, but treat them normally during normal execution,
25746 handle SIGALRM nopass
25750 handle SIGALRM pass
25753 define hook-continue
25754 handle SIGALRM pass
25758 As a further example, to hook at the beginning and end of the @code{echo}
25759 command, and to add extra text to the beginning and end of the message,
25767 define hookpost-echo
25771 (@value{GDBP}) echo Hello World
25772 <<<---Hello World--->>>
25777 You can define a hook for any single-word command in @value{GDBN}, but
25778 not for command aliases; you should define a hook for the basic command
25779 name, e.g.@: @code{backtrace} rather than @code{bt}.
25780 @c FIXME! So how does Joe User discover whether a command is an alias
25782 You can hook a multi-word command by adding @code{hook-} or
25783 @code{hookpost-} to the last word of the command, e.g.@:
25784 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25786 If an error occurs during the execution of your hook, execution of
25787 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25788 (before the command that you actually typed had a chance to run).
25790 If you try to define a hook which does not match any known command, you
25791 get a warning from the @code{define} command.
25793 @node Command Files
25794 @subsection Command Files
25796 @cindex command files
25797 @cindex scripting commands
25798 A command file for @value{GDBN} is a text file made of lines that are
25799 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25800 also be included. An empty line in a command file does nothing; it
25801 does not mean to repeat the last command, as it would from the
25804 You can request the execution of a command file with the @code{source}
25805 command. Note that the @code{source} command is also used to evaluate
25806 scripts that are not Command Files. The exact behavior can be configured
25807 using the @code{script-extension} setting.
25808 @xref{Extending GDB,, Extending GDB}.
25812 @cindex execute commands from a file
25813 @item source [-s] [-v] @var{filename}
25814 Execute the command file @var{filename}.
25817 The lines in a command file are generally executed sequentially,
25818 unless the order of execution is changed by one of the
25819 @emph{flow-control commands} described below. The commands are not
25820 printed as they are executed. An error in any command terminates
25821 execution of the command file and control is returned to the console.
25823 @value{GDBN} first searches for @var{filename} in the current directory.
25824 If the file is not found there, and @var{filename} does not specify a
25825 directory, then @value{GDBN} also looks for the file on the source search path
25826 (specified with the @samp{directory} command);
25827 except that @file{$cdir} is not searched because the compilation directory
25828 is not relevant to scripts.
25830 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25831 on the search path even if @var{filename} specifies a directory.
25832 The search is done by appending @var{filename} to each element of the
25833 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25834 and the search path contains @file{/home/user} then @value{GDBN} will
25835 look for the script @file{/home/user/mylib/myscript}.
25836 The search is also done if @var{filename} is an absolute path.
25837 For example, if @var{filename} is @file{/tmp/myscript} and
25838 the search path contains @file{/home/user} then @value{GDBN} will
25839 look for the script @file{/home/user/tmp/myscript}.
25840 For DOS-like systems, if @var{filename} contains a drive specification,
25841 it is stripped before concatenation. For example, if @var{filename} is
25842 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25843 will look for the script @file{c:/tmp/myscript}.
25845 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25846 each command as it is executed. The option must be given before
25847 @var{filename}, and is interpreted as part of the filename anywhere else.
25849 Commands that would ask for confirmation if used interactively proceed
25850 without asking when used in a command file. Many @value{GDBN} commands that
25851 normally print messages to say what they are doing omit the messages
25852 when called from command files.
25854 @value{GDBN} also accepts command input from standard input. In this
25855 mode, normal output goes to standard output and error output goes to
25856 standard error. Errors in a command file supplied on standard input do
25857 not terminate execution of the command file---execution continues with
25861 gdb < cmds > log 2>&1
25864 (The syntax above will vary depending on the shell used.) This example
25865 will execute commands from the file @file{cmds}. All output and errors
25866 would be directed to @file{log}.
25868 Since commands stored on command files tend to be more general than
25869 commands typed interactively, they frequently need to deal with
25870 complicated situations, such as different or unexpected values of
25871 variables and symbols, changes in how the program being debugged is
25872 built, etc. @value{GDBN} provides a set of flow-control commands to
25873 deal with these complexities. Using these commands, you can write
25874 complex scripts that loop over data structures, execute commands
25875 conditionally, etc.
25882 This command allows to include in your script conditionally executed
25883 commands. The @code{if} command takes a single argument, which is an
25884 expression to evaluate. It is followed by a series of commands that
25885 are executed only if the expression is true (its value is nonzero).
25886 There can then optionally be an @code{else} line, followed by a series
25887 of commands that are only executed if the expression was false. The
25888 end of the list is marked by a line containing @code{end}.
25892 This command allows to write loops. Its syntax is similar to
25893 @code{if}: the command takes a single argument, which is an expression
25894 to evaluate, and must be followed by the commands to execute, one per
25895 line, terminated by an @code{end}. These commands are called the
25896 @dfn{body} of the loop. The commands in the body of @code{while} are
25897 executed repeatedly as long as the expression evaluates to true.
25901 This command exits the @code{while} loop in whose body it is included.
25902 Execution of the script continues after that @code{while}s @code{end}
25905 @kindex loop_continue
25906 @item loop_continue
25907 This command skips the execution of the rest of the body of commands
25908 in the @code{while} loop in whose body it is included. Execution
25909 branches to the beginning of the @code{while} loop, where it evaluates
25910 the controlling expression.
25912 @kindex end@r{ (if/else/while commands)}
25914 Terminate the block of commands that are the body of @code{if},
25915 @code{else}, or @code{while} flow-control commands.
25920 @subsection Commands for Controlled Output
25922 During the execution of a command file or a user-defined command, normal
25923 @value{GDBN} output is suppressed; the only output that appears is what is
25924 explicitly printed by the commands in the definition. This section
25925 describes three commands useful for generating exactly the output you
25930 @item echo @var{text}
25931 @c I do not consider backslash-space a standard C escape sequence
25932 @c because it is not in ANSI.
25933 Print @var{text}. Nonprinting characters can be included in
25934 @var{text} using C escape sequences, such as @samp{\n} to print a
25935 newline. @strong{No newline is printed unless you specify one.}
25936 In addition to the standard C escape sequences, a backslash followed
25937 by a space stands for a space. This is useful for displaying a
25938 string with spaces at the beginning or the end, since leading and
25939 trailing spaces are otherwise trimmed from all arguments.
25940 To print @samp{@w{ }and foo =@w{ }}, use the command
25941 @samp{echo \@w{ }and foo = \@w{ }}.
25943 A backslash at the end of @var{text} can be used, as in C, to continue
25944 the command onto subsequent lines. For example,
25947 echo This is some text\n\
25948 which is continued\n\
25949 onto several lines.\n
25952 produces the same output as
25955 echo This is some text\n
25956 echo which is continued\n
25957 echo onto several lines.\n
25961 @item output @var{expression}
25962 Print the value of @var{expression} and nothing but that value: no
25963 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25964 value history either. @xref{Expressions, ,Expressions}, for more information
25967 @item output/@var{fmt} @var{expression}
25968 Print the value of @var{expression} in format @var{fmt}. You can use
25969 the same formats as for @code{print}. @xref{Output Formats,,Output
25970 Formats}, for more information.
25973 @item printf @var{template}, @var{expressions}@dots{}
25974 Print the values of one or more @var{expressions} under the control of
25975 the string @var{template}. To print several values, make
25976 @var{expressions} be a comma-separated list of individual expressions,
25977 which may be either numbers or pointers. Their values are printed as
25978 specified by @var{template}, exactly as a C program would do by
25979 executing the code below:
25982 printf (@var{template}, @var{expressions}@dots{});
25985 As in @code{C} @code{printf}, ordinary characters in @var{template}
25986 are printed verbatim, while @dfn{conversion specification} introduced
25987 by the @samp{%} character cause subsequent @var{expressions} to be
25988 evaluated, their values converted and formatted according to type and
25989 style information encoded in the conversion specifications, and then
25992 For example, you can print two values in hex like this:
25995 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25998 @code{printf} supports all the standard @code{C} conversion
25999 specifications, including the flags and modifiers between the @samp{%}
26000 character and the conversion letter, with the following exceptions:
26004 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26007 The modifier @samp{*} is not supported for specifying precision or
26011 The @samp{'} flag (for separation of digits into groups according to
26012 @code{LC_NUMERIC'}) is not supported.
26015 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26019 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26022 The conversion letters @samp{a} and @samp{A} are not supported.
26026 Note that the @samp{ll} type modifier is supported only if the
26027 underlying @code{C} implementation used to build @value{GDBN} supports
26028 the @code{long long int} type, and the @samp{L} type modifier is
26029 supported only if @code{long double} type is available.
26031 As in @code{C}, @code{printf} supports simple backslash-escape
26032 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26033 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26034 single character. Octal and hexadecimal escape sequences are not
26037 Additionally, @code{printf} supports conversion specifications for DFP
26038 (@dfn{Decimal Floating Point}) types using the following length modifiers
26039 together with a floating point specifier.
26044 @samp{H} for printing @code{Decimal32} types.
26047 @samp{D} for printing @code{Decimal64} types.
26050 @samp{DD} for printing @code{Decimal128} types.
26053 If the underlying @code{C} implementation used to build @value{GDBN} has
26054 support for the three length modifiers for DFP types, other modifiers
26055 such as width and precision will also be available for @value{GDBN} to use.
26057 In case there is no such @code{C} support, no additional modifiers will be
26058 available and the value will be printed in the standard way.
26060 Here's an example of printing DFP types using the above conversion letters:
26062 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26067 @item eval @var{template}, @var{expressions}@dots{}
26068 Convert the values of one or more @var{expressions} under the control of
26069 the string @var{template} to a command line, and call it.
26073 @node Auto-loading sequences
26074 @subsection Controlling auto-loading native @value{GDBN} scripts
26075 @cindex native script auto-loading
26077 When a new object file is read (for example, due to the @code{file}
26078 command, or because the inferior has loaded a shared library),
26079 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26080 @xref{Auto-loading extensions}.
26082 Auto-loading can be enabled or disabled,
26083 and the list of auto-loaded scripts can be printed.
26086 @anchor{set auto-load gdb-scripts}
26087 @kindex set auto-load gdb-scripts
26088 @item set auto-load gdb-scripts [on|off]
26089 Enable or disable the auto-loading of canned sequences of commands scripts.
26091 @anchor{show auto-load gdb-scripts}
26092 @kindex show auto-load gdb-scripts
26093 @item show auto-load gdb-scripts
26094 Show whether auto-loading of canned sequences of commands scripts is enabled or
26097 @anchor{info auto-load gdb-scripts}
26098 @kindex info auto-load gdb-scripts
26099 @cindex print list of auto-loaded canned sequences of commands scripts
26100 @item info auto-load gdb-scripts [@var{regexp}]
26101 Print the list of all canned sequences of commands scripts that @value{GDBN}
26105 If @var{regexp} is supplied only canned sequences of commands scripts with
26106 matching names are printed.
26108 @c Python docs live in a separate file.
26109 @include python.texi
26111 @c Guile docs live in a separate file.
26112 @include guile.texi
26114 @node Auto-loading extensions
26115 @section Auto-loading extensions
26116 @cindex auto-loading extensions
26118 @value{GDBN} provides two mechanisms for automatically loading extensions
26119 when a new object file is read (for example, due to the @code{file}
26120 command, or because the inferior has loaded a shared library):
26121 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26122 section of modern file formats like ELF.
26125 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26126 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26127 * Which flavor to choose?::
26130 The auto-loading feature is useful for supplying application-specific
26131 debugging commands and features.
26133 Auto-loading can be enabled or disabled,
26134 and the list of auto-loaded scripts can be printed.
26135 See the @samp{auto-loading} section of each extension language
26136 for more information.
26137 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26138 For Python files see @ref{Python Auto-loading}.
26140 Note that loading of this script file also requires accordingly configured
26141 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26143 @node objfile-gdbdotext file
26144 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26145 @cindex @file{@var{objfile}-gdb.gdb}
26146 @cindex @file{@var{objfile}-gdb.py}
26147 @cindex @file{@var{objfile}-gdb.scm}
26149 When a new object file is read, @value{GDBN} looks for a file named
26150 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26151 where @var{objfile} is the object file's name and
26152 where @var{ext} is the file extension for the extension language:
26155 @item @file{@var{objfile}-gdb.gdb}
26156 GDB's own command language
26157 @item @file{@var{objfile}-gdb.py}
26159 @item @file{@var{objfile}-gdb.scm}
26163 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26164 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26165 components, and appending the @file{-gdb.@var{ext}} suffix.
26166 If this file exists and is readable, @value{GDBN} will evaluate it as a
26167 script in the specified extension language.
26169 If this file does not exist, then @value{GDBN} will look for
26170 @var{script-name} file in all of the directories as specified below.
26172 Note that loading of these files requires an accordingly configured
26173 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26175 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26176 scripts normally according to its @file{.exe} filename. But if no scripts are
26177 found @value{GDBN} also tries script filenames matching the object file without
26178 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26179 is attempted on any platform. This makes the script filenames compatible
26180 between Unix and MS-Windows hosts.
26183 @anchor{set auto-load scripts-directory}
26184 @kindex set auto-load scripts-directory
26185 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26186 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26187 may be delimited by the host platform path separator in use
26188 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26190 Each entry here needs to be covered also by the security setting
26191 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26193 @anchor{with-auto-load-dir}
26194 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26195 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26196 configuration option @option{--with-auto-load-dir}.
26198 Any reference to @file{$debugdir} will get replaced by
26199 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26200 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26201 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26202 @file{$datadir} must be placed as a directory component --- either alone or
26203 delimited by @file{/} or @file{\} directory separators, depending on the host
26206 The list of directories uses path separator (@samp{:} on GNU and Unix
26207 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26208 to the @env{PATH} environment variable.
26210 @anchor{show auto-load scripts-directory}
26211 @kindex show auto-load scripts-directory
26212 @item show auto-load scripts-directory
26213 Show @value{GDBN} auto-loaded scripts location.
26215 @anchor{add-auto-load-scripts-directory}
26216 @kindex add-auto-load-scripts-directory
26217 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26218 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26219 Multiple entries may be delimited by the host platform path separator in use.
26222 @value{GDBN} does not track which files it has already auto-loaded this way.
26223 @value{GDBN} will load the associated script every time the corresponding
26224 @var{objfile} is opened.
26225 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26226 is evaluated more than once.
26228 @node dotdebug_gdb_scripts section
26229 @subsection The @code{.debug_gdb_scripts} section
26230 @cindex @code{.debug_gdb_scripts} section
26232 For systems using file formats like ELF and COFF,
26233 when @value{GDBN} loads a new object file
26234 it will look for a special section named @code{.debug_gdb_scripts}.
26235 If this section exists, its contents is a list of null-terminated entries
26236 specifying scripts to load. Each entry begins with a non-null prefix byte that
26237 specifies the kind of entry, typically the extension language and whether the
26238 script is in a file or inlined in @code{.debug_gdb_scripts}.
26240 The following entries are supported:
26243 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26244 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26245 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26246 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26249 @subsubsection Script File Entries
26251 If the entry specifies a file, @value{GDBN} will look for the file first
26252 in the current directory and then along the source search path
26253 (@pxref{Source Path, ,Specifying Source Directories}),
26254 except that @file{$cdir} is not searched, since the compilation
26255 directory is not relevant to scripts.
26257 File entries can be placed in section @code{.debug_gdb_scripts} with,
26258 for example, this GCC macro for Python scripts.
26261 /* Note: The "MS" section flags are to remove duplicates. */
26262 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26264 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26265 .byte 1 /* Python */\n\
26266 .asciz \"" script_name "\"\n\
26272 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26273 Then one can reference the macro in a header or source file like this:
26276 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26279 The script name may include directories if desired.
26281 Note that loading of this script file also requires accordingly configured
26282 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26284 If the macro invocation is put in a header, any application or library
26285 using this header will get a reference to the specified script,
26286 and with the use of @code{"MS"} attributes on the section, the linker
26287 will remove duplicates.
26289 @subsubsection Script Text Entries
26291 Script text entries allow to put the executable script in the entry
26292 itself instead of loading it from a file.
26293 The first line of the entry, everything after the prefix byte and up to
26294 the first newline (@code{0xa}) character, is the script name, and must not
26295 contain any kind of space character, e.g., spaces or tabs.
26296 The rest of the entry, up to the trailing null byte, is the script to
26297 execute in the specified language. The name needs to be unique among
26298 all script names, as @value{GDBN} executes each script only once based
26301 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26305 #include "symcat.h"
26306 #include "gdb/section-scripts.h"
26308 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26309 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26310 ".ascii \"gdb.inlined-script\\n\"\n"
26311 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26312 ".ascii \" def __init__ (self):\\n\"\n"
26313 ".ascii \" super (test_cmd, self).__init__ ("
26314 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26315 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26316 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26317 ".ascii \"test_cmd ()\\n\"\n"
26323 Loading of inlined scripts requires a properly configured
26324 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26325 The path to specify in @code{auto-load safe-path} is the path of the file
26326 containing the @code{.debug_gdb_scripts} section.
26328 @node Which flavor to choose?
26329 @subsection Which flavor to choose?
26331 Given the multiple ways of auto-loading extensions, it might not always
26332 be clear which one to choose. This section provides some guidance.
26335 Benefits of the @file{-gdb.@var{ext}} way:
26339 Can be used with file formats that don't support multiple sections.
26342 Ease of finding scripts for public libraries.
26344 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26345 in the source search path.
26346 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26347 isn't a source directory in which to find the script.
26350 Doesn't require source code additions.
26354 Benefits of the @code{.debug_gdb_scripts} way:
26358 Works with static linking.
26360 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26361 trigger their loading. When an application is statically linked the only
26362 objfile available is the executable, and it is cumbersome to attach all the
26363 scripts from all the input libraries to the executable's
26364 @file{-gdb.@var{ext}} script.
26367 Works with classes that are entirely inlined.
26369 Some classes can be entirely inlined, and thus there may not be an associated
26370 shared library to attach a @file{-gdb.@var{ext}} script to.
26373 Scripts needn't be copied out of the source tree.
26375 In some circumstances, apps can be built out of large collections of internal
26376 libraries, and the build infrastructure necessary to install the
26377 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26378 cumbersome. It may be easier to specify the scripts in the
26379 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26380 top of the source tree to the source search path.
26383 @node Multiple Extension Languages
26384 @section Multiple Extension Languages
26386 The Guile and Python extension languages do not share any state,
26387 and generally do not interfere with each other.
26388 There are some things to be aware of, however.
26390 @subsection Python comes first
26392 Python was @value{GDBN}'s first extension language, and to avoid breaking
26393 existing behaviour Python comes first. This is generally solved by the
26394 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26395 extension languages, and when it makes a call to an extension language,
26396 (say to pretty-print a value), it tries each in turn until an extension
26397 language indicates it has performed the request (e.g., has returned the
26398 pretty-printed form of a value).
26399 This extends to errors while performing such requests: If an error happens
26400 while, for example, trying to pretty-print an object then the error is
26401 reported and any following extension languages are not tried.
26404 @section Creating new spellings of existing commands
26405 @cindex aliases for commands
26407 It is often useful to define alternate spellings of existing commands.
26408 For example, if a new @value{GDBN} command defined in Python has
26409 a long name to type, it is handy to have an abbreviated version of it
26410 that involves less typing.
26412 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26413 of the @samp{step} command even though it is otherwise an ambiguous
26414 abbreviation of other commands like @samp{set} and @samp{show}.
26416 Aliases are also used to provide shortened or more common versions
26417 of multi-word commands. For example, @value{GDBN} provides the
26418 @samp{tty} alias of the @samp{set inferior-tty} command.
26420 You can define a new alias with the @samp{alias} command.
26425 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26429 @var{ALIAS} specifies the name of the new alias.
26430 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26433 @var{COMMAND} specifies the name of an existing command
26434 that is being aliased.
26436 The @samp{-a} option specifies that the new alias is an abbreviation
26437 of the command. Abbreviations are not shown in command
26438 lists displayed by the @samp{help} command.
26440 The @samp{--} option specifies the end of options,
26441 and is useful when @var{ALIAS} begins with a dash.
26443 Here is a simple example showing how to make an abbreviation
26444 of a command so that there is less to type.
26445 Suppose you were tired of typing @samp{disas}, the current
26446 shortest unambiguous abbreviation of the @samp{disassemble} command
26447 and you wanted an even shorter version named @samp{di}.
26448 The following will accomplish this.
26451 (gdb) alias -a di = disas
26454 Note that aliases are different from user-defined commands.
26455 With a user-defined command, you also need to write documentation
26456 for it with the @samp{document} command.
26457 An alias automatically picks up the documentation of the existing command.
26459 Here is an example where we make @samp{elms} an abbreviation of
26460 @samp{elements} in the @samp{set print elements} command.
26461 This is to show that you can make an abbreviation of any part
26465 (gdb) alias -a set print elms = set print elements
26466 (gdb) alias -a show print elms = show print elements
26467 (gdb) set p elms 20
26469 Limit on string chars or array elements to print is 200.
26472 Note that if you are defining an alias of a @samp{set} command,
26473 and you want to have an alias for the corresponding @samp{show}
26474 command, then you need to define the latter separately.
26476 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26477 @var{ALIAS}, just as they are normally.
26480 (gdb) alias -a set pr elms = set p ele
26483 Finally, here is an example showing the creation of a one word
26484 alias for a more complex command.
26485 This creates alias @samp{spe} of the command @samp{set print elements}.
26488 (gdb) alias spe = set print elements
26493 @chapter Command Interpreters
26494 @cindex command interpreters
26496 @value{GDBN} supports multiple command interpreters, and some command
26497 infrastructure to allow users or user interface writers to switch
26498 between interpreters or run commands in other interpreters.
26500 @value{GDBN} currently supports two command interpreters, the console
26501 interpreter (sometimes called the command-line interpreter or @sc{cli})
26502 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26503 describes both of these interfaces in great detail.
26505 By default, @value{GDBN} will start with the console interpreter.
26506 However, the user may choose to start @value{GDBN} with another
26507 interpreter by specifying the @option{-i} or @option{--interpreter}
26508 startup options. Defined interpreters include:
26512 @cindex console interpreter
26513 The traditional console or command-line interpreter. This is the most often
26514 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26515 @value{GDBN} will use this interpreter.
26518 @cindex mi interpreter
26519 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
26520 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26521 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26525 @cindex mi3 interpreter
26526 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
26529 @cindex mi2 interpreter
26530 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
26533 @cindex mi1 interpreter
26534 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
26538 @cindex invoke another interpreter
26540 @kindex interpreter-exec
26541 You may execute commands in any interpreter from the current
26542 interpreter using the appropriate command. If you are running the
26543 console interpreter, simply use the @code{interpreter-exec} command:
26546 interpreter-exec mi "-data-list-register-names"
26549 @sc{gdb/mi} has a similar command, although it is only available in versions of
26550 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26552 Note that @code{interpreter-exec} only changes the interpreter for the
26553 duration of the specified command. It does not change the interpreter
26556 @cindex start a new independent interpreter
26558 Although you may only choose a single interpreter at startup, it is
26559 possible to run an independent interpreter on a specified input/output
26560 device (usually a tty).
26562 For example, consider a debugger GUI or IDE that wants to provide a
26563 @value{GDBN} console view. It may do so by embedding a terminal
26564 emulator widget in its GUI, starting @value{GDBN} in the traditional
26565 command-line mode with stdin/stdout/stderr redirected to that
26566 terminal, and then creating an MI interpreter running on a specified
26567 input/output device. The console interpreter created by @value{GDBN}
26568 at startup handles commands the user types in the terminal widget,
26569 while the GUI controls and synchronizes state with @value{GDBN} using
26570 the separate MI interpreter.
26572 To start a new secondary @dfn{user interface} running MI, use the
26573 @code{new-ui} command:
26576 @cindex new user interface
26578 new-ui @var{interpreter} @var{tty}
26581 The @var{interpreter} parameter specifies the interpreter to run.
26582 This accepts the same values as the @code{interpreter-exec} command.
26583 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26584 @var{tty} parameter specifies the name of the bidirectional file the
26585 interpreter uses for input/output, usually the name of a
26586 pseudoterminal slave on Unix systems. For example:
26589 (@value{GDBP}) new-ui mi /dev/pts/9
26593 runs an MI interpreter on @file{/dev/pts/9}.
26596 @chapter @value{GDBN} Text User Interface
26598 @cindex Text User Interface
26601 * TUI Overview:: TUI overview
26602 * TUI Keys:: TUI key bindings
26603 * TUI Single Key Mode:: TUI single key mode
26604 * TUI Commands:: TUI-specific commands
26605 * TUI Configuration:: TUI configuration variables
26608 The @value{GDBN} Text User Interface (TUI) is a terminal
26609 interface which uses the @code{curses} library to show the source
26610 file, the assembly output, the program registers and @value{GDBN}
26611 commands in separate text windows. The TUI mode is supported only
26612 on platforms where a suitable version of the @code{curses} library
26615 The TUI mode is enabled by default when you invoke @value{GDBN} as
26616 @samp{@value{GDBP} -tui}.
26617 You can also switch in and out of TUI mode while @value{GDBN} runs by
26618 using various TUI commands and key bindings, such as @command{tui
26619 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26620 @ref{TUI Keys, ,TUI Key Bindings}.
26623 @section TUI Overview
26625 In TUI mode, @value{GDBN} can display several text windows:
26629 This window is the @value{GDBN} command window with the @value{GDBN}
26630 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26631 managed using readline.
26634 The source window shows the source file of the program. The current
26635 line and active breakpoints are displayed in this window.
26638 The assembly window shows the disassembly output of the program.
26641 This window shows the processor registers. Registers are highlighted
26642 when their values change.
26645 The source and assembly windows show the current program position
26646 by highlighting the current line and marking it with a @samp{>} marker.
26647 Breakpoints are indicated with two markers. The first marker
26648 indicates the breakpoint type:
26652 Breakpoint which was hit at least once.
26655 Breakpoint which was never hit.
26658 Hardware breakpoint which was hit at least once.
26661 Hardware breakpoint which was never hit.
26664 The second marker indicates whether the breakpoint is enabled or not:
26668 Breakpoint is enabled.
26671 Breakpoint is disabled.
26674 The source, assembly and register windows are updated when the current
26675 thread changes, when the frame changes, or when the program counter
26678 These windows are not all visible at the same time. The command
26679 window is always visible. The others can be arranged in several
26690 source and assembly,
26693 source and registers, or
26696 assembly and registers.
26699 A status line above the command window shows the following information:
26703 Indicates the current @value{GDBN} target.
26704 (@pxref{Targets, ,Specifying a Debugging Target}).
26707 Gives the current process or thread number.
26708 When no process is being debugged, this field is set to @code{No process}.
26711 Gives the current function name for the selected frame.
26712 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26713 When there is no symbol corresponding to the current program counter,
26714 the string @code{??} is displayed.
26717 Indicates the current line number for the selected frame.
26718 When the current line number is not known, the string @code{??} is displayed.
26721 Indicates the current program counter address.
26725 @section TUI Key Bindings
26726 @cindex TUI key bindings
26728 The TUI installs several key bindings in the readline keymaps
26729 @ifset SYSTEM_READLINE
26730 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26732 @ifclear SYSTEM_READLINE
26733 (@pxref{Command Line Editing}).
26735 The following key bindings are installed for both TUI mode and the
26736 @value{GDBN} standard mode.
26745 Enter or leave the TUI mode. When leaving the TUI mode,
26746 the curses window management stops and @value{GDBN} operates using
26747 its standard mode, writing on the terminal directly. When reentering
26748 the TUI mode, control is given back to the curses windows.
26749 The screen is then refreshed.
26753 Use a TUI layout with only one window. The layout will
26754 either be @samp{source} or @samp{assembly}. When the TUI mode
26755 is not active, it will switch to the TUI mode.
26757 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26761 Use a TUI layout with at least two windows. When the current
26762 layout already has two windows, the next layout with two windows is used.
26763 When a new layout is chosen, one window will always be common to the
26764 previous layout and the new one.
26766 Think of it as the Emacs @kbd{C-x 2} binding.
26770 Change the active window. The TUI associates several key bindings
26771 (like scrolling and arrow keys) with the active window. This command
26772 gives the focus to the next TUI window.
26774 Think of it as the Emacs @kbd{C-x o} binding.
26778 Switch in and out of the TUI SingleKey mode that binds single
26779 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26782 The following key bindings only work in the TUI mode:
26787 Scroll the active window one page up.
26791 Scroll the active window one page down.
26795 Scroll the active window one line up.
26799 Scroll the active window one line down.
26803 Scroll the active window one column left.
26807 Scroll the active window one column right.
26811 Refresh the screen.
26814 Because the arrow keys scroll the active window in the TUI mode, they
26815 are not available for their normal use by readline unless the command
26816 window has the focus. When another window is active, you must use
26817 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26818 and @kbd{C-f} to control the command window.
26820 @node TUI Single Key Mode
26821 @section TUI Single Key Mode
26822 @cindex TUI single key mode
26824 The TUI also provides a @dfn{SingleKey} mode, which binds several
26825 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26826 switch into this mode, where the following key bindings are used:
26829 @kindex c @r{(SingleKey TUI key)}
26833 @kindex d @r{(SingleKey TUI key)}
26837 @kindex f @r{(SingleKey TUI key)}
26841 @kindex n @r{(SingleKey TUI key)}
26845 @kindex o @r{(SingleKey TUI key)}
26847 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26849 @kindex q @r{(SingleKey TUI key)}
26851 exit the SingleKey mode.
26853 @kindex r @r{(SingleKey TUI key)}
26857 @kindex s @r{(SingleKey TUI key)}
26861 @kindex i @r{(SingleKey TUI key)}
26863 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26865 @kindex u @r{(SingleKey TUI key)}
26869 @kindex v @r{(SingleKey TUI key)}
26873 @kindex w @r{(SingleKey TUI key)}
26878 Other keys temporarily switch to the @value{GDBN} command prompt.
26879 The key that was pressed is inserted in the editing buffer so that
26880 it is possible to type most @value{GDBN} commands without interaction
26881 with the TUI SingleKey mode. Once the command is entered the TUI
26882 SingleKey mode is restored. The only way to permanently leave
26883 this mode is by typing @kbd{q} or @kbd{C-x s}.
26887 @section TUI-specific Commands
26888 @cindex TUI commands
26890 The TUI has specific commands to control the text windows.
26891 These commands are always available, even when @value{GDBN} is not in
26892 the TUI mode. When @value{GDBN} is in the standard mode, most
26893 of these commands will automatically switch to the TUI mode.
26895 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26896 terminal, or @value{GDBN} has been started with the machine interface
26897 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26898 these commands will fail with an error, because it would not be
26899 possible or desirable to enable curses window management.
26904 Activate TUI mode. The last active TUI window layout will be used if
26905 TUI mode has prevsiouly been used in the current debugging session,
26906 otherwise a default layout is used.
26909 @kindex tui disable
26910 Disable TUI mode, returning to the console interpreter.
26914 List and give the size of all displayed windows.
26916 @item layout @var{name}
26918 Changes which TUI windows are displayed. In each layout the command
26919 window is always displayed, the @var{name} parameter controls which
26920 additional windows are displayed, and can be any of the following:
26924 Display the next layout.
26927 Display the previous layout.
26930 Display the source and command windows.
26933 Display the assembly and command windows.
26936 Display the source, assembly, and command windows.
26939 When in @code{src} layout display the register, source, and command
26940 windows. When in @code{asm} or @code{split} layout display the
26941 register, assembler, and command windows.
26944 @item focus @var{name}
26946 Changes which TUI window is currently active for scrolling. The
26947 @var{name} parameter can be any of the following:
26951 Make the next window active for scrolling.
26954 Make the previous window active for scrolling.
26957 Make the source window active for scrolling.
26960 Make the assembly window active for scrolling.
26963 Make the register window active for scrolling.
26966 Make the command window active for scrolling.
26971 Refresh the screen. This is similar to typing @kbd{C-L}.
26973 @item tui reg @var{group}
26975 Changes the register group displayed in the tui register window to
26976 @var{group}. If the register window is not currently displayed this
26977 command will cause the register window to be displayed. The list of
26978 register groups, as well as their order is target specific. The
26979 following groups are available on most targets:
26982 Repeatedly selecting this group will cause the display to cycle
26983 through all of the available register groups.
26986 Repeatedly selecting this group will cause the display to cycle
26987 through all of the available register groups in the reverse order to
26991 Display the general registers.
26993 Display the floating point registers.
26995 Display the system registers.
26997 Display the vector registers.
26999 Display all registers.
27004 Update the source window and the current execution point.
27006 @item winheight @var{name} +@var{count}
27007 @itemx winheight @var{name} -@var{count}
27009 Change the height of the window @var{name} by @var{count}
27010 lines. Positive counts increase the height, while negative counts
27011 decrease it. The @var{name} parameter can be one of @code{src} (the
27012 source window), @code{cmd} (the command window), @code{asm} (the
27013 disassembly window), or @code{regs} (the register display window).
27016 @node TUI Configuration
27017 @section TUI Configuration Variables
27018 @cindex TUI configuration variables
27020 Several configuration variables control the appearance of TUI windows.
27023 @item set tui border-kind @var{kind}
27024 @kindex set tui border-kind
27025 Select the border appearance for the source, assembly and register windows.
27026 The possible values are the following:
27029 Use a space character to draw the border.
27032 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27035 Use the Alternate Character Set to draw the border. The border is
27036 drawn using character line graphics if the terminal supports them.
27039 @item set tui border-mode @var{mode}
27040 @kindex set tui border-mode
27041 @itemx set tui active-border-mode @var{mode}
27042 @kindex set tui active-border-mode
27043 Select the display attributes for the borders of the inactive windows
27044 or the active window. The @var{mode} can be one of the following:
27047 Use normal attributes to display the border.
27053 Use reverse video mode.
27056 Use half bright mode.
27058 @item half-standout
27059 Use half bright and standout mode.
27062 Use extra bright or bold mode.
27064 @item bold-standout
27065 Use extra bright or bold and standout mode.
27068 @item set tui tab-width @var{nchars}
27069 @kindex set tui tab-width
27071 Set the width of tab stops to be @var{nchars} characters. This
27072 setting affects the display of TAB characters in the source and
27077 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27080 @cindex @sc{gnu} Emacs
27081 A special interface allows you to use @sc{gnu} Emacs to view (and
27082 edit) the source files for the program you are debugging with
27085 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27086 executable file you want to debug as an argument. This command starts
27087 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27088 created Emacs buffer.
27089 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27091 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27096 All ``terminal'' input and output goes through an Emacs buffer, called
27099 This applies both to @value{GDBN} commands and their output, and to the input
27100 and output done by the program you are debugging.
27102 This is useful because it means that you can copy the text of previous
27103 commands and input them again; you can even use parts of the output
27106 All the facilities of Emacs' Shell mode are available for interacting
27107 with your program. In particular, you can send signals the usual
27108 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27112 @value{GDBN} displays source code through Emacs.
27114 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27115 source file for that frame and puts an arrow (@samp{=>}) at the
27116 left margin of the current line. Emacs uses a separate buffer for
27117 source display, and splits the screen to show both your @value{GDBN} session
27120 Explicit @value{GDBN} @code{list} or search commands still produce output as
27121 usual, but you probably have no reason to use them from Emacs.
27124 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27125 a graphical mode, enabled by default, which provides further buffers
27126 that can control the execution and describe the state of your program.
27127 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27129 If you specify an absolute file name when prompted for the @kbd{M-x
27130 gdb} argument, then Emacs sets your current working directory to where
27131 your program resides. If you only specify the file name, then Emacs
27132 sets your current working directory to the directory associated
27133 with the previous buffer. In this case, @value{GDBN} may find your
27134 program by searching your environment's @code{PATH} variable, but on
27135 some operating systems it might not find the source. So, although the
27136 @value{GDBN} input and output session proceeds normally, the auxiliary
27137 buffer does not display the current source and line of execution.
27139 The initial working directory of @value{GDBN} is printed on the top
27140 line of the GUD buffer and this serves as a default for the commands
27141 that specify files for @value{GDBN} to operate on. @xref{Files,
27142 ,Commands to Specify Files}.
27144 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27145 need to call @value{GDBN} by a different name (for example, if you
27146 keep several configurations around, with different names) you can
27147 customize the Emacs variable @code{gud-gdb-command-name} to run the
27150 In the GUD buffer, you can use these special Emacs commands in
27151 addition to the standard Shell mode commands:
27155 Describe the features of Emacs' GUD Mode.
27158 Execute to another source line, like the @value{GDBN} @code{step} command; also
27159 update the display window to show the current file and location.
27162 Execute to next source line in this function, skipping all function
27163 calls, like the @value{GDBN} @code{next} command. Then update the display window
27164 to show the current file and location.
27167 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27168 display window accordingly.
27171 Execute until exit from the selected stack frame, like the @value{GDBN}
27172 @code{finish} command.
27175 Continue execution of your program, like the @value{GDBN} @code{continue}
27179 Go up the number of frames indicated by the numeric argument
27180 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27181 like the @value{GDBN} @code{up} command.
27184 Go down the number of frames indicated by the numeric argument, like the
27185 @value{GDBN} @code{down} command.
27188 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27189 tells @value{GDBN} to set a breakpoint on the source line point is on.
27191 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27192 separate frame which shows a backtrace when the GUD buffer is current.
27193 Move point to any frame in the stack and type @key{RET} to make it
27194 become the current frame and display the associated source in the
27195 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27196 selected frame become the current one. In graphical mode, the
27197 speedbar displays watch expressions.
27199 If you accidentally delete the source-display buffer, an easy way to get
27200 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27201 request a frame display; when you run under Emacs, this recreates
27202 the source buffer if necessary to show you the context of the current
27205 The source files displayed in Emacs are in ordinary Emacs buffers
27206 which are visiting the source files in the usual way. You can edit
27207 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27208 communicates with Emacs in terms of line numbers. If you add or
27209 delete lines from the text, the line numbers that @value{GDBN} knows cease
27210 to correspond properly with the code.
27212 A more detailed description of Emacs' interaction with @value{GDBN} is
27213 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27217 @chapter The @sc{gdb/mi} Interface
27219 @unnumberedsec Function and Purpose
27221 @cindex @sc{gdb/mi}, its purpose
27222 @sc{gdb/mi} is a line based machine oriented text interface to
27223 @value{GDBN} and is activated by specifying using the
27224 @option{--interpreter} command line option (@pxref{Mode Options}). It
27225 is specifically intended to support the development of systems which
27226 use the debugger as just one small component of a larger system.
27228 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27229 in the form of a reference manual.
27231 Note that @sc{gdb/mi} is still under construction, so some of the
27232 features described below are incomplete and subject to change
27233 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27235 @unnumberedsec Notation and Terminology
27237 @cindex notational conventions, for @sc{gdb/mi}
27238 This chapter uses the following notation:
27242 @code{|} separates two alternatives.
27245 @code{[ @var{something} ]} indicates that @var{something} is optional:
27246 it may or may not be given.
27249 @code{( @var{group} )*} means that @var{group} inside the parentheses
27250 may repeat zero or more times.
27253 @code{( @var{group} )+} means that @var{group} inside the parentheses
27254 may repeat one or more times.
27257 @code{"@var{string}"} means a literal @var{string}.
27261 @heading Dependencies
27265 * GDB/MI General Design::
27266 * GDB/MI Command Syntax::
27267 * GDB/MI Compatibility with CLI::
27268 * GDB/MI Development and Front Ends::
27269 * GDB/MI Output Records::
27270 * GDB/MI Simple Examples::
27271 * GDB/MI Command Description Format::
27272 * GDB/MI Breakpoint Commands::
27273 * GDB/MI Catchpoint Commands::
27274 * GDB/MI Program Context::
27275 * GDB/MI Thread Commands::
27276 * GDB/MI Ada Tasking Commands::
27277 * GDB/MI Program Execution::
27278 * GDB/MI Stack Manipulation::
27279 * GDB/MI Variable Objects::
27280 * GDB/MI Data Manipulation::
27281 * GDB/MI Tracepoint Commands::
27282 * GDB/MI Symbol Query::
27283 * GDB/MI File Commands::
27285 * GDB/MI Kod Commands::
27286 * GDB/MI Memory Overlay Commands::
27287 * GDB/MI Signal Handling Commands::
27289 * GDB/MI Target Manipulation::
27290 * GDB/MI File Transfer Commands::
27291 * GDB/MI Ada Exceptions Commands::
27292 * GDB/MI Support Commands::
27293 * GDB/MI Miscellaneous Commands::
27296 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27297 @node GDB/MI General Design
27298 @section @sc{gdb/mi} General Design
27299 @cindex GDB/MI General Design
27301 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27302 parts---commands sent to @value{GDBN}, responses to those commands
27303 and notifications. Each command results in exactly one response,
27304 indicating either successful completion of the command, or an error.
27305 For the commands that do not resume the target, the response contains the
27306 requested information. For the commands that resume the target, the
27307 response only indicates whether the target was successfully resumed.
27308 Notifications is the mechanism for reporting changes in the state of the
27309 target, or in @value{GDBN} state, that cannot conveniently be associated with
27310 a command and reported as part of that command response.
27312 The important examples of notifications are:
27316 Exec notifications. These are used to report changes in
27317 target state---when a target is resumed, or stopped. It would not
27318 be feasible to include this information in response of resuming
27319 commands, because one resume commands can result in multiple events in
27320 different threads. Also, quite some time may pass before any event
27321 happens in the target, while a frontend needs to know whether the resuming
27322 command itself was successfully executed.
27325 Console output, and status notifications. Console output
27326 notifications are used to report output of CLI commands, as well as
27327 diagnostics for other commands. Status notifications are used to
27328 report the progress of a long-running operation. Naturally, including
27329 this information in command response would mean no output is produced
27330 until the command is finished, which is undesirable.
27333 General notifications. Commands may have various side effects on
27334 the @value{GDBN} or target state beyond their official purpose. For example,
27335 a command may change the selected thread. Although such changes can
27336 be included in command response, using notification allows for more
27337 orthogonal frontend design.
27341 There's no guarantee that whenever an MI command reports an error,
27342 @value{GDBN} or the target are in any specific state, and especially,
27343 the state is not reverted to the state before the MI command was
27344 processed. Therefore, whenever an MI command results in an error,
27345 we recommend that the frontend refreshes all the information shown in
27346 the user interface.
27350 * Context management::
27351 * Asynchronous and non-stop modes::
27355 @node Context management
27356 @subsection Context management
27358 @subsubsection Threads and Frames
27360 In most cases when @value{GDBN} accesses the target, this access is
27361 done in context of a specific thread and frame (@pxref{Frames}).
27362 Often, even when accessing global data, the target requires that a thread
27363 be specified. The CLI interface maintains the selected thread and frame,
27364 and supplies them to target on each command. This is convenient,
27365 because a command line user would not want to specify that information
27366 explicitly on each command, and because user interacts with
27367 @value{GDBN} via a single terminal, so no confusion is possible as
27368 to what thread and frame are the current ones.
27370 In the case of MI, the concept of selected thread and frame is less
27371 useful. First, a frontend can easily remember this information
27372 itself. Second, a graphical frontend can have more than one window,
27373 each one used for debugging a different thread, and the frontend might
27374 want to access additional threads for internal purposes. This
27375 increases the risk that by relying on implicitly selected thread, the
27376 frontend may be operating on a wrong one. Therefore, each MI command
27377 should explicitly specify which thread and frame to operate on. To
27378 make it possible, each MI command accepts the @samp{--thread} and
27379 @samp{--frame} options, the value to each is @value{GDBN} global
27380 identifier for thread and frame to operate on.
27382 Usually, each top-level window in a frontend allows the user to select
27383 a thread and a frame, and remembers the user selection for further
27384 operations. However, in some cases @value{GDBN} may suggest that the
27385 current thread or frame be changed. For example, when stopping on a
27386 breakpoint it is reasonable to switch to the thread where breakpoint is
27387 hit. For another example, if the user issues the CLI @samp{thread} or
27388 @samp{frame} commands via the frontend, it is desirable to change the
27389 frontend's selection to the one specified by user. @value{GDBN}
27390 communicates the suggestion to change current thread and frame using the
27391 @samp{=thread-selected} notification.
27393 Note that historically, MI shares the selected thread with CLI, so
27394 frontends used the @code{-thread-select} to execute commands in the
27395 right context. However, getting this to work right is cumbersome. The
27396 simplest way is for frontend to emit @code{-thread-select} command
27397 before every command. This doubles the number of commands that need
27398 to be sent. The alternative approach is to suppress @code{-thread-select}
27399 if the selected thread in @value{GDBN} is supposed to be identical to the
27400 thread the frontend wants to operate on. However, getting this
27401 optimization right can be tricky. In particular, if the frontend
27402 sends several commands to @value{GDBN}, and one of the commands changes the
27403 selected thread, then the behaviour of subsequent commands will
27404 change. So, a frontend should either wait for response from such
27405 problematic commands, or explicitly add @code{-thread-select} for
27406 all subsequent commands. No frontend is known to do this exactly
27407 right, so it is suggested to just always pass the @samp{--thread} and
27408 @samp{--frame} options.
27410 @subsubsection Language
27412 The execution of several commands depends on which language is selected.
27413 By default, the current language (@pxref{show language}) is used.
27414 But for commands known to be language-sensitive, it is recommended
27415 to use the @samp{--language} option. This option takes one argument,
27416 which is the name of the language to use while executing the command.
27420 -data-evaluate-expression --language c "sizeof (void*)"
27425 The valid language names are the same names accepted by the
27426 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27427 @samp{local} or @samp{unknown}.
27429 @node Asynchronous and non-stop modes
27430 @subsection Asynchronous command execution and non-stop mode
27432 On some targets, @value{GDBN} is capable of processing MI commands
27433 even while the target is running. This is called @dfn{asynchronous
27434 command execution} (@pxref{Background Execution}). The frontend may
27435 specify a preferrence for asynchronous execution using the
27436 @code{-gdb-set mi-async 1} command, which should be emitted before
27437 either running the executable or attaching to the target. After the
27438 frontend has started the executable or attached to the target, it can
27439 find if asynchronous execution is enabled using the
27440 @code{-list-target-features} command.
27443 @item -gdb-set mi-async on
27444 @item -gdb-set mi-async off
27445 Set whether MI is in asynchronous mode.
27447 When @code{off}, which is the default, MI execution commands (e.g.,
27448 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27449 for the program to stop before processing further commands.
27451 When @code{on}, MI execution commands are background execution
27452 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27453 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27454 MI commands even while the target is running.
27456 @item -gdb-show mi-async
27457 Show whether MI asynchronous mode is enabled.
27460 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27461 @code{target-async} instead of @code{mi-async}, and it had the effect
27462 of both putting MI in asynchronous mode and making CLI background
27463 commands possible. CLI background commands are now always possible
27464 ``out of the box'' if the target supports them. The old spelling is
27465 kept as a deprecated alias for backwards compatibility.
27467 Even if @value{GDBN} can accept a command while target is running,
27468 many commands that access the target do not work when the target is
27469 running. Therefore, asynchronous command execution is most useful
27470 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27471 it is possible to examine the state of one thread, while other threads
27474 When a given thread is running, MI commands that try to access the
27475 target in the context of that thread may not work, or may work only on
27476 some targets. In particular, commands that try to operate on thread's
27477 stack will not work, on any target. Commands that read memory, or
27478 modify breakpoints, may work or not work, depending on the target. Note
27479 that even commands that operate on global state, such as @code{print},
27480 @code{set}, and breakpoint commands, still access the target in the
27481 context of a specific thread, so frontend should try to find a
27482 stopped thread and perform the operation on that thread (using the
27483 @samp{--thread} option).
27485 Which commands will work in the context of a running thread is
27486 highly target dependent. However, the two commands
27487 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27488 to find the state of a thread, will always work.
27490 @node Thread groups
27491 @subsection Thread groups
27492 @value{GDBN} may be used to debug several processes at the same time.
27493 On some platfroms, @value{GDBN} may support debugging of several
27494 hardware systems, each one having several cores with several different
27495 processes running on each core. This section describes the MI
27496 mechanism to support such debugging scenarios.
27498 The key observation is that regardless of the structure of the
27499 target, MI can have a global list of threads, because most commands that
27500 accept the @samp{--thread} option do not need to know what process that
27501 thread belongs to. Therefore, it is not necessary to introduce
27502 neither additional @samp{--process} option, nor an notion of the
27503 current process in the MI interface. The only strictly new feature
27504 that is required is the ability to find how the threads are grouped
27507 To allow the user to discover such grouping, and to support arbitrary
27508 hierarchy of machines/cores/processes, MI introduces the concept of a
27509 @dfn{thread group}. Thread group is a collection of threads and other
27510 thread groups. A thread group always has a string identifier, a type,
27511 and may have additional attributes specific to the type. A new
27512 command, @code{-list-thread-groups}, returns the list of top-level
27513 thread groups, which correspond to processes that @value{GDBN} is
27514 debugging at the moment. By passing an identifier of a thread group
27515 to the @code{-list-thread-groups} command, it is possible to obtain
27516 the members of specific thread group.
27518 To allow the user to easily discover processes, and other objects, he
27519 wishes to debug, a concept of @dfn{available thread group} is
27520 introduced. Available thread group is an thread group that
27521 @value{GDBN} is not debugging, but that can be attached to, using the
27522 @code{-target-attach} command. The list of available top-level thread
27523 groups can be obtained using @samp{-list-thread-groups --available}.
27524 In general, the content of a thread group may be only retrieved only
27525 after attaching to that thread group.
27527 Thread groups are related to inferiors (@pxref{Inferiors and
27528 Programs}). Each inferior corresponds to a thread group of a special
27529 type @samp{process}, and some additional operations are permitted on
27530 such thread groups.
27532 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27533 @node GDB/MI Command Syntax
27534 @section @sc{gdb/mi} Command Syntax
27537 * GDB/MI Input Syntax::
27538 * GDB/MI Output Syntax::
27541 @node GDB/MI Input Syntax
27542 @subsection @sc{gdb/mi} Input Syntax
27544 @cindex input syntax for @sc{gdb/mi}
27545 @cindex @sc{gdb/mi}, input syntax
27547 @item @var{command} @expansion{}
27548 @code{@var{cli-command} | @var{mi-command}}
27550 @item @var{cli-command} @expansion{}
27551 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27552 @var{cli-command} is any existing @value{GDBN} CLI command.
27554 @item @var{mi-command} @expansion{}
27555 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27556 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27558 @item @var{token} @expansion{}
27559 "any sequence of digits"
27561 @item @var{option} @expansion{}
27562 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27564 @item @var{parameter} @expansion{}
27565 @code{@var{non-blank-sequence} | @var{c-string}}
27567 @item @var{operation} @expansion{}
27568 @emph{any of the operations described in this chapter}
27570 @item @var{non-blank-sequence} @expansion{}
27571 @emph{anything, provided it doesn't contain special characters such as
27572 "-", @var{nl}, """ and of course " "}
27574 @item @var{c-string} @expansion{}
27575 @code{""" @var{seven-bit-iso-c-string-content} """}
27577 @item @var{nl} @expansion{}
27586 The CLI commands are still handled by the @sc{mi} interpreter; their
27587 output is described below.
27590 The @code{@var{token}}, when present, is passed back when the command
27594 Some @sc{mi} commands accept optional arguments as part of the parameter
27595 list. Each option is identified by a leading @samp{-} (dash) and may be
27596 followed by an optional argument parameter. Options occur first in the
27597 parameter list and can be delimited from normal parameters using
27598 @samp{--} (this is useful when some parameters begin with a dash).
27605 We want easy access to the existing CLI syntax (for debugging).
27608 We want it to be easy to spot a @sc{mi} operation.
27611 @node GDB/MI Output Syntax
27612 @subsection @sc{gdb/mi} Output Syntax
27614 @cindex output syntax of @sc{gdb/mi}
27615 @cindex @sc{gdb/mi}, output syntax
27616 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27617 followed, optionally, by a single result record. This result record
27618 is for the most recent command. The sequence of output records is
27619 terminated by @samp{(gdb)}.
27621 If an input command was prefixed with a @code{@var{token}} then the
27622 corresponding output for that command will also be prefixed by that same
27626 @item @var{output} @expansion{}
27627 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27629 @item @var{result-record} @expansion{}
27630 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27632 @item @var{out-of-band-record} @expansion{}
27633 @code{@var{async-record} | @var{stream-record}}
27635 @item @var{async-record} @expansion{}
27636 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27638 @item @var{exec-async-output} @expansion{}
27639 @code{[ @var{token} ] "*" @var{async-output nl}}
27641 @item @var{status-async-output} @expansion{}
27642 @code{[ @var{token} ] "+" @var{async-output nl}}
27644 @item @var{notify-async-output} @expansion{}
27645 @code{[ @var{token} ] "=" @var{async-output nl}}
27647 @item @var{async-output} @expansion{}
27648 @code{@var{async-class} ( "," @var{result} )*}
27650 @item @var{result-class} @expansion{}
27651 @code{"done" | "running" | "connected" | "error" | "exit"}
27653 @item @var{async-class} @expansion{}
27654 @code{"stopped" | @var{others}} (where @var{others} will be added
27655 depending on the needs---this is still in development).
27657 @item @var{result} @expansion{}
27658 @code{ @var{variable} "=" @var{value}}
27660 @item @var{variable} @expansion{}
27661 @code{ @var{string} }
27663 @item @var{value} @expansion{}
27664 @code{ @var{const} | @var{tuple} | @var{list} }
27666 @item @var{const} @expansion{}
27667 @code{@var{c-string}}
27669 @item @var{tuple} @expansion{}
27670 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27672 @item @var{list} @expansion{}
27673 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27674 @var{result} ( "," @var{result} )* "]" }
27676 @item @var{stream-record} @expansion{}
27677 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27679 @item @var{console-stream-output} @expansion{}
27680 @code{"~" @var{c-string nl}}
27682 @item @var{target-stream-output} @expansion{}
27683 @code{"@@" @var{c-string nl}}
27685 @item @var{log-stream-output} @expansion{}
27686 @code{"&" @var{c-string nl}}
27688 @item @var{nl} @expansion{}
27691 @item @var{token} @expansion{}
27692 @emph{any sequence of digits}.
27700 All output sequences end in a single line containing a period.
27703 The @code{@var{token}} is from the corresponding request. Note that
27704 for all async output, while the token is allowed by the grammar and
27705 may be output by future versions of @value{GDBN} for select async
27706 output messages, it is generally omitted. Frontends should treat
27707 all async output as reporting general changes in the state of the
27708 target and there should be no need to associate async output to any
27712 @cindex status output in @sc{gdb/mi}
27713 @var{status-async-output} contains on-going status information about the
27714 progress of a slow operation. It can be discarded. All status output is
27715 prefixed by @samp{+}.
27718 @cindex async output in @sc{gdb/mi}
27719 @var{exec-async-output} contains asynchronous state change on the target
27720 (stopped, started, disappeared). All async output is prefixed by
27724 @cindex notify output in @sc{gdb/mi}
27725 @var{notify-async-output} contains supplementary information that the
27726 client should handle (e.g., a new breakpoint information). All notify
27727 output is prefixed by @samp{=}.
27730 @cindex console output in @sc{gdb/mi}
27731 @var{console-stream-output} is output that should be displayed as is in the
27732 console. It is the textual response to a CLI command. All the console
27733 output is prefixed by @samp{~}.
27736 @cindex target output in @sc{gdb/mi}
27737 @var{target-stream-output} is the output produced by the target program.
27738 All the target output is prefixed by @samp{@@}.
27741 @cindex log output in @sc{gdb/mi}
27742 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27743 instance messages that should be displayed as part of an error log. All
27744 the log output is prefixed by @samp{&}.
27747 @cindex list output in @sc{gdb/mi}
27748 New @sc{gdb/mi} commands should only output @var{lists} containing
27754 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27755 details about the various output records.
27757 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27758 @node GDB/MI Compatibility with CLI
27759 @section @sc{gdb/mi} Compatibility with CLI
27761 @cindex compatibility, @sc{gdb/mi} and CLI
27762 @cindex @sc{gdb/mi}, compatibility with CLI
27764 For the developers convenience CLI commands can be entered directly,
27765 but there may be some unexpected behaviour. For example, commands
27766 that query the user will behave as if the user replied yes, breakpoint
27767 command lists are not executed and some CLI commands, such as
27768 @code{if}, @code{when} and @code{define}, prompt for further input with
27769 @samp{>}, which is not valid MI output.
27771 This feature may be removed at some stage in the future and it is
27772 recommended that front ends use the @code{-interpreter-exec} command
27773 (@pxref{-interpreter-exec}).
27775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27776 @node GDB/MI Development and Front Ends
27777 @section @sc{gdb/mi} Development and Front Ends
27778 @cindex @sc{gdb/mi} development
27780 The application which takes the MI output and presents the state of the
27781 program being debugged to the user is called a @dfn{front end}.
27783 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
27784 to the MI interface may break existing usage. This section describes how the
27785 protocol changes and how to request previous version of the protocol when it
27788 Some changes in MI need not break a carefully designed front end, and
27789 for these the MI version will remain unchanged. The following is a
27790 list of changes that may occur within one level, so front ends should
27791 parse MI output in a way that can handle them:
27795 New MI commands may be added.
27798 New fields may be added to the output of any MI command.
27801 The range of values for fields with specified values, e.g.,
27802 @code{in_scope} (@pxref{-var-update}) may be extended.
27804 @c The format of field's content e.g type prefix, may change so parse it
27805 @c at your own risk. Yes, in general?
27807 @c The order of fields may change? Shouldn't really matter but it might
27808 @c resolve inconsistencies.
27811 If the changes are likely to break front ends, the MI version level
27812 will be increased by one. The new versions of the MI protocol are not compatible
27813 with the old versions. Old versions of MI remain available, allowing front ends
27814 to keep using them until they are modified to use the latest MI version.
27816 Since @code{--interpreter=mi} always points to the latest MI version, it is
27817 recommended that front ends request a specific version of MI when launching
27818 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
27819 interpreter with the MI version they expect.
27821 The following table gives a summary of the the released versions of the MI
27822 interface: the version number, the version of GDB in which it first appeared
27823 and the breaking changes compared to the previous version.
27825 @multitable @columnfractions .05 .05 .9
27826 @headitem MI version @tab GDB version @tab Breaking changes
27843 The @code{-environment-pwd}, @code{-environment-directory} and
27844 @code{-environment-path} commands now returns values using the MI output
27845 syntax, rather than CLI output syntax.
27848 @code{-var-list-children}'s @code{children} result field is now a list, rather
27852 @code{-var-update}'s @code{changelist} result field is now a list, rather than
27864 The output of information about multi-location breakpoints has changed in the
27865 responses to the @code{-break-insert} and @code{-break-info} commands, as well
27866 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
27867 The multiple locations are now placed in a @code{locations} field, whose value
27873 If your front end cannot yet migrate to a more recent version of the
27874 MI protocol, you can nevertheless selectively enable specific features
27875 available in those recent MI versions, using the following commands:
27879 @item -fix-multi-location-breakpoint-output
27880 Use the output for multi-location breakpoints which was introduced by
27881 MI 3, even when using MI versions 2 or 1. This command has no
27882 effect when using MI version 3 or later.
27886 The best way to avoid unexpected changes in MI that might break your front
27887 end is to make your project known to @value{GDBN} developers and
27888 follow development on @email{gdb@@sourceware.org} and
27889 @email{gdb-patches@@sourceware.org}.
27890 @cindex mailing lists
27892 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27893 @node GDB/MI Output Records
27894 @section @sc{gdb/mi} Output Records
27897 * GDB/MI Result Records::
27898 * GDB/MI Stream Records::
27899 * GDB/MI Async Records::
27900 * GDB/MI Breakpoint Information::
27901 * GDB/MI Frame Information::
27902 * GDB/MI Thread Information::
27903 * GDB/MI Ada Exception Information::
27906 @node GDB/MI Result Records
27907 @subsection @sc{gdb/mi} Result Records
27909 @cindex result records in @sc{gdb/mi}
27910 @cindex @sc{gdb/mi}, result records
27911 In addition to a number of out-of-band notifications, the response to a
27912 @sc{gdb/mi} command includes one of the following result indications:
27916 @item "^done" [ "," @var{results} ]
27917 The synchronous operation was successful, @code{@var{results}} are the return
27922 This result record is equivalent to @samp{^done}. Historically, it
27923 was output instead of @samp{^done} if the command has resumed the
27924 target. This behaviour is maintained for backward compatibility, but
27925 all frontends should treat @samp{^done} and @samp{^running}
27926 identically and rely on the @samp{*running} output record to determine
27927 which threads are resumed.
27931 @value{GDBN} has connected to a remote target.
27933 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27935 The operation failed. The @code{msg=@var{c-string}} variable contains
27936 the corresponding error message.
27938 If present, the @code{code=@var{c-string}} variable provides an error
27939 code on which consumers can rely on to detect the corresponding
27940 error condition. At present, only one error code is defined:
27943 @item "undefined-command"
27944 Indicates that the command causing the error does not exist.
27949 @value{GDBN} has terminated.
27953 @node GDB/MI Stream Records
27954 @subsection @sc{gdb/mi} Stream Records
27956 @cindex @sc{gdb/mi}, stream records
27957 @cindex stream records in @sc{gdb/mi}
27958 @value{GDBN} internally maintains a number of output streams: the console, the
27959 target, and the log. The output intended for each of these streams is
27960 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27962 Each stream record begins with a unique @dfn{prefix character} which
27963 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27964 Syntax}). In addition to the prefix, each stream record contains a
27965 @code{@var{string-output}}. This is either raw text (with an implicit new
27966 line) or a quoted C string (which does not contain an implicit newline).
27969 @item "~" @var{string-output}
27970 The console output stream contains text that should be displayed in the
27971 CLI console window. It contains the textual responses to CLI commands.
27973 @item "@@" @var{string-output}
27974 The target output stream contains any textual output from the running
27975 target. This is only present when GDB's event loop is truly
27976 asynchronous, which is currently only the case for remote targets.
27978 @item "&" @var{string-output}
27979 The log stream contains debugging messages being produced by @value{GDBN}'s
27983 @node GDB/MI Async Records
27984 @subsection @sc{gdb/mi} Async Records
27986 @cindex async records in @sc{gdb/mi}
27987 @cindex @sc{gdb/mi}, async records
27988 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27989 additional changes that have occurred. Those changes can either be a
27990 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27991 target activity (e.g., target stopped).
27993 The following is the list of possible async records:
27997 @item *running,thread-id="@var{thread}"
27998 The target is now running. The @var{thread} field can be the global
27999 thread ID of the the thread that is now running, and it can be
28000 @samp{all} if all threads are running. The frontend should assume
28001 that no interaction with a running thread is possible after this
28002 notification is produced. The frontend should not assume that this
28003 notification is output only once for any command. @value{GDBN} may
28004 emit this notification several times, either for different threads,
28005 because it cannot resume all threads together, or even for a single
28006 thread, if the thread must be stepped though some code before letting
28009 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28010 The target has stopped. The @var{reason} field can have one of the
28014 @item breakpoint-hit
28015 A breakpoint was reached.
28016 @item watchpoint-trigger
28017 A watchpoint was triggered.
28018 @item read-watchpoint-trigger
28019 A read watchpoint was triggered.
28020 @item access-watchpoint-trigger
28021 An access watchpoint was triggered.
28022 @item function-finished
28023 An -exec-finish or similar CLI command was accomplished.
28024 @item location-reached
28025 An -exec-until or similar CLI command was accomplished.
28026 @item watchpoint-scope
28027 A watchpoint has gone out of scope.
28028 @item end-stepping-range
28029 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28030 similar CLI command was accomplished.
28031 @item exited-signalled
28032 The inferior exited because of a signal.
28034 The inferior exited.
28035 @item exited-normally
28036 The inferior exited normally.
28037 @item signal-received
28038 A signal was received by the inferior.
28040 The inferior has stopped due to a library being loaded or unloaded.
28041 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28042 set or when a @code{catch load} or @code{catch unload} catchpoint is
28043 in use (@pxref{Set Catchpoints}).
28045 The inferior has forked. This is reported when @code{catch fork}
28046 (@pxref{Set Catchpoints}) has been used.
28048 The inferior has vforked. This is reported in when @code{catch vfork}
28049 (@pxref{Set Catchpoints}) has been used.
28050 @item syscall-entry
28051 The inferior entered a system call. This is reported when @code{catch
28052 syscall} (@pxref{Set Catchpoints}) has been used.
28053 @item syscall-return
28054 The inferior returned from a system call. This is reported when
28055 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28057 The inferior called @code{exec}. This is reported when @code{catch exec}
28058 (@pxref{Set Catchpoints}) has been used.
28061 The @var{id} field identifies the global thread ID of the thread
28062 that directly caused the stop -- for example by hitting a breakpoint.
28063 Depending on whether all-stop
28064 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28065 stop all threads, or only the thread that directly triggered the stop.
28066 If all threads are stopped, the @var{stopped} field will have the
28067 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28068 field will be a list of thread identifiers. Presently, this list will
28069 always include a single thread, but frontend should be prepared to see
28070 several threads in the list. The @var{core} field reports the
28071 processor core on which the stop event has happened. This field may be absent
28072 if such information is not available.
28074 @item =thread-group-added,id="@var{id}"
28075 @itemx =thread-group-removed,id="@var{id}"
28076 A thread group was either added or removed. The @var{id} field
28077 contains the @value{GDBN} identifier of the thread group. When a thread
28078 group is added, it generally might not be associated with a running
28079 process. When a thread group is removed, its id becomes invalid and
28080 cannot be used in any way.
28082 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28083 A thread group became associated with a running program,
28084 either because the program was just started or the thread group
28085 was attached to a program. The @var{id} field contains the
28086 @value{GDBN} identifier of the thread group. The @var{pid} field
28087 contains process identifier, specific to the operating system.
28089 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28090 A thread group is no longer associated with a running program,
28091 either because the program has exited, or because it was detached
28092 from. The @var{id} field contains the @value{GDBN} identifier of the
28093 thread group. The @var{code} field is the exit code of the inferior; it exists
28094 only when the inferior exited with some code.
28096 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28097 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28098 A thread either was created, or has exited. The @var{id} field
28099 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28100 field identifies the thread group this thread belongs to.
28102 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28103 Informs that the selected thread or frame were changed. This notification
28104 is not emitted as result of the @code{-thread-select} or
28105 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28106 that is not documented to change the selected thread and frame actually
28107 changes them. In particular, invoking, directly or indirectly
28108 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28109 will generate this notification. Changing the thread or frame from another
28110 user interface (see @ref{Interpreters}) will also generate this notification.
28112 The @var{frame} field is only present if the newly selected thread is
28113 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28115 We suggest that in response to this notification, front ends
28116 highlight the selected thread and cause subsequent commands to apply to
28119 @item =library-loaded,...
28120 Reports that a new library file was loaded by the program. This
28121 notification has 5 fields---@var{id}, @var{target-name},
28122 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28123 opaque identifier of the library. For remote debugging case,
28124 @var{target-name} and @var{host-name} fields give the name of the
28125 library file on the target, and on the host respectively. For native
28126 debugging, both those fields have the same value. The
28127 @var{symbols-loaded} field is emitted only for backward compatibility
28128 and should not be relied on to convey any useful information. The
28129 @var{thread-group} field, if present, specifies the id of the thread
28130 group in whose context the library was loaded. If the field is
28131 absent, it means the library was loaded in the context of all present
28132 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28135 @item =library-unloaded,...
28136 Reports that a library was unloaded by the program. This notification
28137 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28138 the same meaning as for the @code{=library-loaded} notification.
28139 The @var{thread-group} field, if present, specifies the id of the
28140 thread group in whose context the library was unloaded. If the field is
28141 absent, it means the library was unloaded in the context of all present
28144 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28145 @itemx =traceframe-changed,end
28146 Reports that the trace frame was changed and its new number is
28147 @var{tfnum}. The number of the tracepoint associated with this trace
28148 frame is @var{tpnum}.
28150 @item =tsv-created,name=@var{name},initial=@var{initial}
28151 Reports that the new trace state variable @var{name} is created with
28152 initial value @var{initial}.
28154 @item =tsv-deleted,name=@var{name}
28155 @itemx =tsv-deleted
28156 Reports that the trace state variable @var{name} is deleted or all
28157 trace state variables are deleted.
28159 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28160 Reports that the trace state variable @var{name} is modified with
28161 the initial value @var{initial}. The current value @var{current} of
28162 trace state variable is optional and is reported if the current
28163 value of trace state variable is known.
28165 @item =breakpoint-created,bkpt=@{...@}
28166 @itemx =breakpoint-modified,bkpt=@{...@}
28167 @itemx =breakpoint-deleted,id=@var{number}
28168 Reports that a breakpoint was created, modified, or deleted,
28169 respectively. Only user-visible breakpoints are reported to the MI
28172 The @var{bkpt} argument is of the same form as returned by the various
28173 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28174 @var{number} is the ordinal number of the breakpoint.
28176 Note that if a breakpoint is emitted in the result record of a
28177 command, then it will not also be emitted in an async record.
28179 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28180 @itemx =record-stopped,thread-group="@var{id}"
28181 Execution log recording was either started or stopped on an
28182 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28183 group corresponding to the affected inferior.
28185 The @var{method} field indicates the method used to record execution. If the
28186 method in use supports multiple recording formats, @var{format} will be present
28187 and contain the currently used format. @xref{Process Record and Replay},
28188 for existing method and format values.
28190 @item =cmd-param-changed,param=@var{param},value=@var{value}
28191 Reports that a parameter of the command @code{set @var{param}} is
28192 changed to @var{value}. In the multi-word @code{set} command,
28193 the @var{param} is the whole parameter list to @code{set} command.
28194 For example, In command @code{set check type on}, @var{param}
28195 is @code{check type} and @var{value} is @code{on}.
28197 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28198 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28199 written in an inferior. The @var{id} is the identifier of the
28200 thread group corresponding to the affected inferior. The optional
28201 @code{type="code"} part is reported if the memory written to holds
28205 @node GDB/MI Breakpoint Information
28206 @subsection @sc{gdb/mi} Breakpoint Information
28208 When @value{GDBN} reports information about a breakpoint, a
28209 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28214 The breakpoint number.
28217 The type of the breakpoint. For ordinary breakpoints this will be
28218 @samp{breakpoint}, but many values are possible.
28221 If the type of the breakpoint is @samp{catchpoint}, then this
28222 indicates the exact type of catchpoint.
28225 This is the breakpoint disposition---either @samp{del}, meaning that
28226 the breakpoint will be deleted at the next stop, or @samp{keep},
28227 meaning that the breakpoint will not be deleted.
28230 This indicates whether the breakpoint is enabled, in which case the
28231 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28232 Note that this is not the same as the field @code{enable}.
28235 The address of the breakpoint. This may be a hexidecimal number,
28236 giving the address; or the string @samp{<PENDING>}, for a pending
28237 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28238 multiple locations. This field will not be present if no address can
28239 be determined. For example, a watchpoint does not have an address.
28242 If known, the function in which the breakpoint appears.
28243 If not known, this field is not present.
28246 The name of the source file which contains this function, if known.
28247 If not known, this field is not present.
28250 The full file name of the source file which contains this function, if
28251 known. If not known, this field is not present.
28254 The line number at which this breakpoint appears, if known.
28255 If not known, this field is not present.
28258 If the source file is not known, this field may be provided. If
28259 provided, this holds the address of the breakpoint, possibly followed
28263 If this breakpoint is pending, this field is present and holds the
28264 text used to set the breakpoint, as entered by the user.
28267 Where this breakpoint's condition is evaluated, either @samp{host} or
28271 If this is a thread-specific breakpoint, then this identifies the
28272 thread in which the breakpoint can trigger.
28275 If this breakpoint is restricted to a particular Ada task, then this
28276 field will hold the task identifier.
28279 If the breakpoint is conditional, this is the condition expression.
28282 The ignore count of the breakpoint.
28285 The enable count of the breakpoint.
28287 @item traceframe-usage
28290 @item static-tracepoint-marker-string-id
28291 For a static tracepoint, the name of the static tracepoint marker.
28294 For a masked watchpoint, this is the mask.
28297 A tracepoint's pass count.
28299 @item original-location
28300 The location of the breakpoint as originally specified by the user.
28301 This field is optional.
28304 The number of times the breakpoint has been hit.
28307 This field is only given for tracepoints. This is either @samp{y},
28308 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28312 Some extra data, the exact contents of which are type-dependent.
28315 This field is present if the breakpoint has multiple locations. It is also
28316 exceptionally present if the breakpoint is enabled and has a single, disabled
28319 The value is a list of locations. The format of a location is decribed below.
28323 A location in a multi-location breakpoint is represented as a tuple with the
28329 The location number as a dotted pair, like @samp{1.2}. The first digit is the
28330 number of the parent breakpoint. The second digit is the number of the
28331 location within that breakpoint.
28334 This indicates whether the location is enabled, in which case the
28335 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28336 Note that this is not the same as the field @code{enable}.
28339 The address of this location as an hexidecimal number.
28342 If known, the function in which the location appears.
28343 If not known, this field is not present.
28346 The name of the source file which contains this location, if known.
28347 If not known, this field is not present.
28350 The full file name of the source file which contains this location, if
28351 known. If not known, this field is not present.
28354 The line number at which this location appears, if known.
28355 If not known, this field is not present.
28357 @item thread-groups
28358 The thread groups this location is in.
28362 For example, here is what the output of @code{-break-insert}
28363 (@pxref{GDB/MI Breakpoint Commands}) might be:
28366 -> -break-insert main
28367 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28368 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28369 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28374 @node GDB/MI Frame Information
28375 @subsection @sc{gdb/mi} Frame Information
28377 Response from many MI commands includes an information about stack
28378 frame. This information is a tuple that may have the following
28383 The level of the stack frame. The innermost frame has the level of
28384 zero. This field is always present.
28387 The name of the function corresponding to the frame. This field may
28388 be absent if @value{GDBN} is unable to determine the function name.
28391 The code address for the frame. This field is always present.
28394 The name of the source files that correspond to the frame's code
28395 address. This field may be absent.
28398 The source line corresponding to the frames' code address. This field
28402 The name of the binary file (either executable or shared library) the
28403 corresponds to the frame's code address. This field may be absent.
28407 @node GDB/MI Thread Information
28408 @subsection @sc{gdb/mi} Thread Information
28410 Whenever @value{GDBN} has to report an information about a thread, it
28411 uses a tuple with the following fields. The fields are always present unless
28416 The global numeric id assigned to the thread by @value{GDBN}.
28419 The target-specific string identifying the thread.
28422 Additional information about the thread provided by the target.
28423 It is supposed to be human-readable and not interpreted by the
28424 frontend. This field is optional.
28427 The name of the thread. If the user specified a name using the
28428 @code{thread name} command, then this name is given. Otherwise, if
28429 @value{GDBN} can extract the thread name from the target, then that
28430 name is given. If @value{GDBN} cannot find the thread name, then this
28434 The execution state of the thread, either @samp{stopped} or @samp{running},
28435 depending on whether the thread is presently running.
28438 The stack frame currently executing in the thread. This field is only present
28439 if the thread is stopped. Its format is documented in
28440 @ref{GDB/MI Frame Information}.
28443 The value of this field is an integer number of the processor core the
28444 thread was last seen on. This field is optional.
28447 @node GDB/MI Ada Exception Information
28448 @subsection @sc{gdb/mi} Ada Exception Information
28450 Whenever a @code{*stopped} record is emitted because the program
28451 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28452 @value{GDBN} provides the name of the exception that was raised via
28453 the @code{exception-name} field. Also, for exceptions that were raised
28454 with an exception message, @value{GDBN} provides that message via
28455 the @code{exception-message} field.
28457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28458 @node GDB/MI Simple Examples
28459 @section Simple Examples of @sc{gdb/mi} Interaction
28460 @cindex @sc{gdb/mi}, simple examples
28462 This subsection presents several simple examples of interaction using
28463 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28464 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28465 the output received from @sc{gdb/mi}.
28467 Note the line breaks shown in the examples are here only for
28468 readability, they don't appear in the real output.
28470 @subheading Setting a Breakpoint
28472 Setting a breakpoint generates synchronous output which contains detailed
28473 information of the breakpoint.
28476 -> -break-insert main
28477 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28478 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28479 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28484 @subheading Program Execution
28486 Program execution generates asynchronous records and MI gives the
28487 reason that execution stopped.
28493 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28494 frame=@{addr="0x08048564",func="main",
28495 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28496 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28497 arch="i386:x86_64"@}
28502 <- *stopped,reason="exited-normally"
28506 @subheading Quitting @value{GDBN}
28508 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28516 Please note that @samp{^exit} is printed immediately, but it might
28517 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28518 performs necessary cleanups, including killing programs being debugged
28519 or disconnecting from debug hardware, so the frontend should wait till
28520 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28521 fails to exit in reasonable time.
28523 @subheading A Bad Command
28525 Here's what happens if you pass a non-existent command:
28529 <- ^error,msg="Undefined MI command: rubbish"
28534 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28535 @node GDB/MI Command Description Format
28536 @section @sc{gdb/mi} Command Description Format
28538 The remaining sections describe blocks of commands. Each block of
28539 commands is laid out in a fashion similar to this section.
28541 @subheading Motivation
28543 The motivation for this collection of commands.
28545 @subheading Introduction
28547 A brief introduction to this collection of commands as a whole.
28549 @subheading Commands
28551 For each command in the block, the following is described:
28553 @subsubheading Synopsis
28556 -command @var{args}@dots{}
28559 @subsubheading Result
28561 @subsubheading @value{GDBN} Command
28563 The corresponding @value{GDBN} CLI command(s), if any.
28565 @subsubheading Example
28567 Example(s) formatted for readability. Some of the described commands have
28568 not been implemented yet and these are labeled N.A.@: (not available).
28571 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28572 @node GDB/MI Breakpoint Commands
28573 @section @sc{gdb/mi} Breakpoint Commands
28575 @cindex breakpoint commands for @sc{gdb/mi}
28576 @cindex @sc{gdb/mi}, breakpoint commands
28577 This section documents @sc{gdb/mi} commands for manipulating
28580 @subheading The @code{-break-after} Command
28581 @findex -break-after
28583 @subsubheading Synopsis
28586 -break-after @var{number} @var{count}
28589 The breakpoint number @var{number} is not in effect until it has been
28590 hit @var{count} times. To see how this is reflected in the output of
28591 the @samp{-break-list} command, see the description of the
28592 @samp{-break-list} command below.
28594 @subsubheading @value{GDBN} Command
28596 The corresponding @value{GDBN} command is @samp{ignore}.
28598 @subsubheading Example
28603 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28604 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28605 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28613 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28614 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28615 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28616 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28617 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28618 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28619 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28620 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28621 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28622 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28627 @subheading The @code{-break-catch} Command
28628 @findex -break-catch
28631 @subheading The @code{-break-commands} Command
28632 @findex -break-commands
28634 @subsubheading Synopsis
28637 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28640 Specifies the CLI commands that should be executed when breakpoint
28641 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28642 are the commands. If no command is specified, any previously-set
28643 commands are cleared. @xref{Break Commands}. Typical use of this
28644 functionality is tracing a program, that is, printing of values of
28645 some variables whenever breakpoint is hit and then continuing.
28647 @subsubheading @value{GDBN} Command
28649 The corresponding @value{GDBN} command is @samp{commands}.
28651 @subsubheading Example
28656 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28657 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28658 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28661 -break-commands 1 "print v" "continue"
28666 @subheading The @code{-break-condition} Command
28667 @findex -break-condition
28669 @subsubheading Synopsis
28672 -break-condition @var{number} @var{expr}
28675 Breakpoint @var{number} will stop the program only if the condition in
28676 @var{expr} is true. The condition becomes part of the
28677 @samp{-break-list} output (see the description of the @samp{-break-list}
28680 @subsubheading @value{GDBN} Command
28682 The corresponding @value{GDBN} command is @samp{condition}.
28684 @subsubheading Example
28688 -break-condition 1 1
28692 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28693 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28694 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28695 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28696 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28697 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28698 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28699 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28700 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28701 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28705 @subheading The @code{-break-delete} Command
28706 @findex -break-delete
28708 @subsubheading Synopsis
28711 -break-delete ( @var{breakpoint} )+
28714 Delete the breakpoint(s) whose number(s) are specified in the argument
28715 list. This is obviously reflected in the breakpoint list.
28717 @subsubheading @value{GDBN} Command
28719 The corresponding @value{GDBN} command is @samp{delete}.
28721 @subsubheading Example
28729 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28730 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28731 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28732 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28733 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28734 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28735 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28740 @subheading The @code{-break-disable} Command
28741 @findex -break-disable
28743 @subsubheading Synopsis
28746 -break-disable ( @var{breakpoint} )+
28749 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28750 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28752 @subsubheading @value{GDBN} Command
28754 The corresponding @value{GDBN} command is @samp{disable}.
28756 @subsubheading Example
28764 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28765 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28766 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28767 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28768 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28769 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28770 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28771 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28772 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28773 line="5",thread-groups=["i1"],times="0"@}]@}
28777 @subheading The @code{-break-enable} Command
28778 @findex -break-enable
28780 @subsubheading Synopsis
28783 -break-enable ( @var{breakpoint} )+
28786 Enable (previously disabled) @var{breakpoint}(s).
28788 @subsubheading @value{GDBN} Command
28790 The corresponding @value{GDBN} command is @samp{enable}.
28792 @subsubheading Example
28800 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28801 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28802 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28803 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28804 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28805 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28806 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28807 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28808 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28809 line="5",thread-groups=["i1"],times="0"@}]@}
28813 @subheading The @code{-break-info} Command
28814 @findex -break-info
28816 @subsubheading Synopsis
28819 -break-info @var{breakpoint}
28823 Get information about a single breakpoint.
28825 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28826 Information}, for details on the format of each breakpoint in the
28829 @subsubheading @value{GDBN} Command
28831 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28833 @subsubheading Example
28836 @subheading The @code{-break-insert} Command
28837 @findex -break-insert
28838 @anchor{-break-insert}
28840 @subsubheading Synopsis
28843 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28844 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28845 [ -p @var{thread-id} ] [ @var{location} ]
28849 If specified, @var{location}, can be one of:
28852 @item linespec location
28853 A linespec location. @xref{Linespec Locations}.
28855 @item explicit location
28856 An explicit location. @sc{gdb/mi} explicit locations are
28857 analogous to the CLI's explicit locations using the option names
28858 listed below. @xref{Explicit Locations}.
28861 @item --source @var{filename}
28862 The source file name of the location. This option requires the use
28863 of either @samp{--function} or @samp{--line}.
28865 @item --function @var{function}
28866 The name of a function or method.
28868 @item --label @var{label}
28869 The name of a label.
28871 @item --line @var{lineoffset}
28872 An absolute or relative line offset from the start of the location.
28875 @item address location
28876 An address location, *@var{address}. @xref{Address Locations}.
28880 The possible optional parameters of this command are:
28884 Insert a temporary breakpoint.
28886 Insert a hardware breakpoint.
28888 If @var{location} cannot be parsed (for example if it
28889 refers to unknown files or functions), create a pending
28890 breakpoint. Without this flag, @value{GDBN} will report
28891 an error, and won't create a breakpoint, if @var{location}
28894 Create a disabled breakpoint.
28896 Create a tracepoint. @xref{Tracepoints}. When this parameter
28897 is used together with @samp{-h}, a fast tracepoint is created.
28898 @item -c @var{condition}
28899 Make the breakpoint conditional on @var{condition}.
28900 @item -i @var{ignore-count}
28901 Initialize the @var{ignore-count}.
28902 @item -p @var{thread-id}
28903 Restrict the breakpoint to the thread with the specified global
28907 @subsubheading Result
28909 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28910 resulting breakpoint.
28912 Note: this format is open to change.
28913 @c An out-of-band breakpoint instead of part of the result?
28915 @subsubheading @value{GDBN} Command
28917 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28918 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28920 @subsubheading Example
28925 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28926 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28929 -break-insert -t foo
28930 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28931 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28935 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28936 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28937 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28938 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28939 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28940 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28941 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28942 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28943 addr="0x0001072c", func="main",file="recursive2.c",
28944 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28946 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28947 addr="0x00010774",func="foo",file="recursive2.c",
28948 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28951 @c -break-insert -r foo.*
28952 @c ~int foo(int, int);
28953 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28954 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28959 @subheading The @code{-dprintf-insert} Command
28960 @findex -dprintf-insert
28962 @subsubheading Synopsis
28965 -dprintf-insert [ -t ] [ -f ] [ -d ]
28966 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28967 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28972 If supplied, @var{location} may be specified the same way as for
28973 the @code{-break-insert} command. @xref{-break-insert}.
28975 The possible optional parameters of this command are:
28979 Insert a temporary breakpoint.
28981 If @var{location} cannot be parsed (for example, if it
28982 refers to unknown files or functions), create a pending
28983 breakpoint. Without this flag, @value{GDBN} will report
28984 an error, and won't create a breakpoint, if @var{location}
28987 Create a disabled breakpoint.
28988 @item -c @var{condition}
28989 Make the breakpoint conditional on @var{condition}.
28990 @item -i @var{ignore-count}
28991 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28992 to @var{ignore-count}.
28993 @item -p @var{thread-id}
28994 Restrict the breakpoint to the thread with the specified global
28998 @subsubheading Result
29000 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29001 resulting breakpoint.
29003 @c An out-of-band breakpoint instead of part of the result?
29005 @subsubheading @value{GDBN} Command
29007 The corresponding @value{GDBN} command is @samp{dprintf}.
29009 @subsubheading Example
29013 4-dprintf-insert foo "At foo entry\n"
29014 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29015 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29016 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29017 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29018 original-location="foo"@}
29020 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29021 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29022 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29023 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29024 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29025 original-location="mi-dprintf.c:26"@}
29029 @subheading The @code{-break-list} Command
29030 @findex -break-list
29032 @subsubheading Synopsis
29038 Displays the list of inserted breakpoints, showing the following fields:
29042 number of the breakpoint
29044 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29046 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29049 is the breakpoint enabled or no: @samp{y} or @samp{n}
29051 memory location at which the breakpoint is set
29053 logical location of the breakpoint, expressed by function name, file
29055 @item Thread-groups
29056 list of thread groups to which this breakpoint applies
29058 number of times the breakpoint has been hit
29061 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29062 @code{body} field is an empty list.
29064 @subsubheading @value{GDBN} Command
29066 The corresponding @value{GDBN} command is @samp{info break}.
29068 @subsubheading Example
29073 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29074 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29075 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29076 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29077 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29078 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29079 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29080 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29081 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29083 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29084 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29085 line="13",thread-groups=["i1"],times="0"@}]@}
29089 Here's an example of the result when there are no breakpoints:
29094 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29095 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29096 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29097 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29098 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29099 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29100 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29105 @subheading The @code{-break-passcount} Command
29106 @findex -break-passcount
29108 @subsubheading Synopsis
29111 -break-passcount @var{tracepoint-number} @var{passcount}
29114 Set the passcount for tracepoint @var{tracepoint-number} to
29115 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29116 is not a tracepoint, error is emitted. This corresponds to CLI
29117 command @samp{passcount}.
29119 @subheading The @code{-break-watch} Command
29120 @findex -break-watch
29122 @subsubheading Synopsis
29125 -break-watch [ -a | -r ]
29128 Create a watchpoint. With the @samp{-a} option it will create an
29129 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29130 read from or on a write to the memory location. With the @samp{-r}
29131 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29132 trigger only when the memory location is accessed for reading. Without
29133 either of the options, the watchpoint created is a regular watchpoint,
29134 i.e., it will trigger when the memory location is accessed for writing.
29135 @xref{Set Watchpoints, , Setting Watchpoints}.
29137 Note that @samp{-break-list} will report a single list of watchpoints and
29138 breakpoints inserted.
29140 @subsubheading @value{GDBN} Command
29142 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29145 @subsubheading Example
29147 Setting a watchpoint on a variable in the @code{main} function:
29152 ^done,wpt=@{number="2",exp="x"@}
29157 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29158 value=@{old="-268439212",new="55"@},
29159 frame=@{func="main",args=[],file="recursive2.c",
29160 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29164 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29165 the program execution twice: first for the variable changing value, then
29166 for the watchpoint going out of scope.
29171 ^done,wpt=@{number="5",exp="C"@}
29176 *stopped,reason="watchpoint-trigger",
29177 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29178 frame=@{func="callee4",args=[],
29179 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29180 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29181 arch="i386:x86_64"@}
29186 *stopped,reason="watchpoint-scope",wpnum="5",
29187 frame=@{func="callee3",args=[@{name="strarg",
29188 value="0x11940 \"A string argument.\""@}],
29189 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29190 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29191 arch="i386:x86_64"@}
29195 Listing breakpoints and watchpoints, at different points in the program
29196 execution. Note that once the watchpoint goes out of scope, it is
29202 ^done,wpt=@{number="2",exp="C"@}
29205 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29206 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29207 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29208 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29209 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29210 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29211 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29212 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29213 addr="0x00010734",func="callee4",
29214 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29215 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29217 bkpt=@{number="2",type="watchpoint",disp="keep",
29218 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29223 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29224 value=@{old="-276895068",new="3"@},
29225 frame=@{func="callee4",args=[],
29226 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29227 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29228 arch="i386:x86_64"@}
29231 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29232 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29233 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29234 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29235 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29236 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29237 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29238 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29239 addr="0x00010734",func="callee4",
29240 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29241 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29243 bkpt=@{number="2",type="watchpoint",disp="keep",
29244 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29248 ^done,reason="watchpoint-scope",wpnum="2",
29249 frame=@{func="callee3",args=[@{name="strarg",
29250 value="0x11940 \"A string argument.\""@}],
29251 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29252 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29253 arch="i386:x86_64"@}
29256 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29257 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29258 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29259 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29260 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29261 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29262 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29263 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29264 addr="0x00010734",func="callee4",
29265 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29266 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29267 thread-groups=["i1"],times="1"@}]@}
29272 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29273 @node GDB/MI Catchpoint Commands
29274 @section @sc{gdb/mi} Catchpoint Commands
29276 This section documents @sc{gdb/mi} commands for manipulating
29280 * Shared Library GDB/MI Catchpoint Commands::
29281 * Ada Exception GDB/MI Catchpoint Commands::
29284 @node Shared Library GDB/MI Catchpoint Commands
29285 @subsection Shared Library @sc{gdb/mi} Catchpoints
29287 @subheading The @code{-catch-load} Command
29288 @findex -catch-load
29290 @subsubheading Synopsis
29293 -catch-load [ -t ] [ -d ] @var{regexp}
29296 Add a catchpoint for library load events. If the @samp{-t} option is used,
29297 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29298 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29299 in a disabled state. The @samp{regexp} argument is a regular
29300 expression used to match the name of the loaded library.
29303 @subsubheading @value{GDBN} Command
29305 The corresponding @value{GDBN} command is @samp{catch load}.
29307 @subsubheading Example
29310 -catch-load -t foo.so
29311 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29312 what="load of library matching foo.so",catch-type="load",times="0"@}
29317 @subheading The @code{-catch-unload} Command
29318 @findex -catch-unload
29320 @subsubheading Synopsis
29323 -catch-unload [ -t ] [ -d ] @var{regexp}
29326 Add a catchpoint for library unload events. If the @samp{-t} option is
29327 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29328 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29329 created in a disabled state. The @samp{regexp} argument is a regular
29330 expression used to match the name of the unloaded library.
29332 @subsubheading @value{GDBN} Command
29334 The corresponding @value{GDBN} command is @samp{catch unload}.
29336 @subsubheading Example
29339 -catch-unload -d bar.so
29340 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29341 what="load of library matching bar.so",catch-type="unload",times="0"@}
29345 @node Ada Exception GDB/MI Catchpoint Commands
29346 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29348 The following @sc{gdb/mi} commands can be used to create catchpoints
29349 that stop the execution when Ada exceptions are being raised.
29351 @subheading The @code{-catch-assert} Command
29352 @findex -catch-assert
29354 @subsubheading Synopsis
29357 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29360 Add a catchpoint for failed Ada assertions.
29362 The possible optional parameters for this command are:
29365 @item -c @var{condition}
29366 Make the catchpoint conditional on @var{condition}.
29368 Create a disabled catchpoint.
29370 Create a temporary catchpoint.
29373 @subsubheading @value{GDBN} Command
29375 The corresponding @value{GDBN} command is @samp{catch assert}.
29377 @subsubheading Example
29381 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29382 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29383 thread-groups=["i1"],times="0",
29384 original-location="__gnat_debug_raise_assert_failure"@}
29388 @subheading The @code{-catch-exception} Command
29389 @findex -catch-exception
29391 @subsubheading Synopsis
29394 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29398 Add a catchpoint stopping when Ada exceptions are raised.
29399 By default, the command stops the program when any Ada exception
29400 gets raised. But it is also possible, by using some of the
29401 optional parameters described below, to create more selective
29404 The possible optional parameters for this command are:
29407 @item -c @var{condition}
29408 Make the catchpoint conditional on @var{condition}.
29410 Create a disabled catchpoint.
29411 @item -e @var{exception-name}
29412 Only stop when @var{exception-name} is raised. This option cannot
29413 be used combined with @samp{-u}.
29415 Create a temporary catchpoint.
29417 Stop only when an unhandled exception gets raised. This option
29418 cannot be used combined with @samp{-e}.
29421 @subsubheading @value{GDBN} Command
29423 The corresponding @value{GDBN} commands are @samp{catch exception}
29424 and @samp{catch exception unhandled}.
29426 @subsubheading Example
29429 -catch-exception -e Program_Error
29430 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29431 enabled="y",addr="0x0000000000404874",
29432 what="`Program_Error' Ada exception", thread-groups=["i1"],
29433 times="0",original-location="__gnat_debug_raise_exception"@}
29437 @subheading The @code{-catch-handlers} Command
29438 @findex -catch-handlers
29440 @subsubheading Synopsis
29443 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29447 Add a catchpoint stopping when Ada exceptions are handled.
29448 By default, the command stops the program when any Ada exception
29449 gets handled. But it is also possible, by using some of the
29450 optional parameters described below, to create more selective
29453 The possible optional parameters for this command are:
29456 @item -c @var{condition}
29457 Make the catchpoint conditional on @var{condition}.
29459 Create a disabled catchpoint.
29460 @item -e @var{exception-name}
29461 Only stop when @var{exception-name} is handled.
29463 Create a temporary catchpoint.
29466 @subsubheading @value{GDBN} Command
29468 The corresponding @value{GDBN} command is @samp{catch handlers}.
29470 @subsubheading Example
29473 -catch-handlers -e Constraint_Error
29474 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29475 enabled="y",addr="0x0000000000402f68",
29476 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29477 times="0",original-location="__gnat_begin_handler"@}
29481 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29482 @node GDB/MI Program Context
29483 @section @sc{gdb/mi} Program Context
29485 @subheading The @code{-exec-arguments} Command
29486 @findex -exec-arguments
29489 @subsubheading Synopsis
29492 -exec-arguments @var{args}
29495 Set the inferior program arguments, to be used in the next
29498 @subsubheading @value{GDBN} Command
29500 The corresponding @value{GDBN} command is @samp{set args}.
29502 @subsubheading Example
29506 -exec-arguments -v word
29513 @subheading The @code{-exec-show-arguments} Command
29514 @findex -exec-show-arguments
29516 @subsubheading Synopsis
29519 -exec-show-arguments
29522 Print the arguments of the program.
29524 @subsubheading @value{GDBN} Command
29526 The corresponding @value{GDBN} command is @samp{show args}.
29528 @subsubheading Example
29533 @subheading The @code{-environment-cd} Command
29534 @findex -environment-cd
29536 @subsubheading Synopsis
29539 -environment-cd @var{pathdir}
29542 Set @value{GDBN}'s working directory.
29544 @subsubheading @value{GDBN} Command
29546 The corresponding @value{GDBN} command is @samp{cd}.
29548 @subsubheading Example
29552 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29558 @subheading The @code{-environment-directory} Command
29559 @findex -environment-directory
29561 @subsubheading Synopsis
29564 -environment-directory [ -r ] [ @var{pathdir} ]+
29567 Add directories @var{pathdir} to beginning of search path for source files.
29568 If the @samp{-r} option is used, the search path is reset to the default
29569 search path. If directories @var{pathdir} are supplied in addition to the
29570 @samp{-r} option, the search path is first reset and then addition
29572 Multiple directories may be specified, separated by blanks. Specifying
29573 multiple directories in a single command
29574 results in the directories added to the beginning of the
29575 search path in the same order they were presented in the command.
29576 If blanks are needed as
29577 part of a directory name, double-quotes should be used around
29578 the name. In the command output, the path will show up separated
29579 by the system directory-separator character. The directory-separator
29580 character must not be used
29581 in any directory name.
29582 If no directories are specified, the current search path is displayed.
29584 @subsubheading @value{GDBN} Command
29586 The corresponding @value{GDBN} command is @samp{dir}.
29588 @subsubheading Example
29592 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29593 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29595 -environment-directory ""
29596 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29598 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29599 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29601 -environment-directory -r
29602 ^done,source-path="$cdir:$cwd"
29607 @subheading The @code{-environment-path} Command
29608 @findex -environment-path
29610 @subsubheading Synopsis
29613 -environment-path [ -r ] [ @var{pathdir} ]+
29616 Add directories @var{pathdir} to beginning of search path for object files.
29617 If the @samp{-r} option is used, the search path is reset to the original
29618 search path that existed at gdb start-up. If directories @var{pathdir} are
29619 supplied in addition to the
29620 @samp{-r} option, the search path is first reset and then addition
29622 Multiple directories may be specified, separated by blanks. Specifying
29623 multiple directories in a single command
29624 results in the directories added to the beginning of the
29625 search path in the same order they were presented in the command.
29626 If blanks are needed as
29627 part of a directory name, double-quotes should be used around
29628 the name. In the command output, the path will show up separated
29629 by the system directory-separator character. The directory-separator
29630 character must not be used
29631 in any directory name.
29632 If no directories are specified, the current path is displayed.
29635 @subsubheading @value{GDBN} Command
29637 The corresponding @value{GDBN} command is @samp{path}.
29639 @subsubheading Example
29644 ^done,path="/usr/bin"
29646 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29647 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29649 -environment-path -r /usr/local/bin
29650 ^done,path="/usr/local/bin:/usr/bin"
29655 @subheading The @code{-environment-pwd} Command
29656 @findex -environment-pwd
29658 @subsubheading Synopsis
29664 Show the current working directory.
29666 @subsubheading @value{GDBN} Command
29668 The corresponding @value{GDBN} command is @samp{pwd}.
29670 @subsubheading Example
29675 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29679 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29680 @node GDB/MI Thread Commands
29681 @section @sc{gdb/mi} Thread Commands
29684 @subheading The @code{-thread-info} Command
29685 @findex -thread-info
29687 @subsubheading Synopsis
29690 -thread-info [ @var{thread-id} ]
29693 Reports information about either a specific thread, if the
29694 @var{thread-id} parameter is present, or about all threads.
29695 @var{thread-id} is the thread's global thread ID. When printing
29696 information about all threads, also reports the global ID of the
29699 @subsubheading @value{GDBN} Command
29701 The @samp{info thread} command prints the same information
29704 @subsubheading Result
29706 The result contains the following attributes:
29710 A list of threads. The format of the elements of the list is described in
29711 @ref{GDB/MI Thread Information}.
29713 @item current-thread-id
29714 The global id of the currently selected thread. This field is omitted if there
29715 is no selected thread (for example, when the selected inferior is not running,
29716 and therefore has no threads) or if a @var{thread-id} argument was passed to
29721 @subsubheading Example
29726 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29727 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29728 args=[]@},state="running"@},
29729 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29730 frame=@{level="0",addr="0x0804891f",func="foo",
29731 args=[@{name="i",value="10"@}],
29732 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29733 state="running"@}],
29734 current-thread-id="1"
29738 @subheading The @code{-thread-list-ids} Command
29739 @findex -thread-list-ids
29741 @subsubheading Synopsis
29747 Produces a list of the currently known global @value{GDBN} thread ids.
29748 At the end of the list it also prints the total number of such
29751 This command is retained for historical reasons, the
29752 @code{-thread-info} command should be used instead.
29754 @subsubheading @value{GDBN} Command
29756 Part of @samp{info threads} supplies the same information.
29758 @subsubheading Example
29763 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29764 current-thread-id="1",number-of-threads="3"
29769 @subheading The @code{-thread-select} Command
29770 @findex -thread-select
29772 @subsubheading Synopsis
29775 -thread-select @var{thread-id}
29778 Make thread with global thread number @var{thread-id} the current
29779 thread. It prints the number of the new current thread, and the
29780 topmost frame for that thread.
29782 This command is deprecated in favor of explicitly using the
29783 @samp{--thread} option to each command.
29785 @subsubheading @value{GDBN} Command
29787 The corresponding @value{GDBN} command is @samp{thread}.
29789 @subsubheading Example
29796 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29797 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29801 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29802 number-of-threads="3"
29805 ^done,new-thread-id="3",
29806 frame=@{level="0",func="vprintf",
29807 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29808 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29813 @node GDB/MI Ada Tasking Commands
29814 @section @sc{gdb/mi} Ada Tasking Commands
29816 @subheading The @code{-ada-task-info} Command
29817 @findex -ada-task-info
29819 @subsubheading Synopsis
29822 -ada-task-info [ @var{task-id} ]
29825 Reports information about either a specific Ada task, if the
29826 @var{task-id} parameter is present, or about all Ada tasks.
29828 @subsubheading @value{GDBN} Command
29830 The @samp{info tasks} command prints the same information
29831 about all Ada tasks (@pxref{Ada Tasks}).
29833 @subsubheading Result
29835 The result is a table of Ada tasks. The following columns are
29836 defined for each Ada task:
29840 This field exists only for the current thread. It has the value @samp{*}.
29843 The identifier that @value{GDBN} uses to refer to the Ada task.
29846 The identifier that the target uses to refer to the Ada task.
29849 The global thread identifier of the thread corresponding to the Ada
29852 This field should always exist, as Ada tasks are always implemented
29853 on top of a thread. But if @value{GDBN} cannot find this corresponding
29854 thread for any reason, the field is omitted.
29857 This field exists only when the task was created by another task.
29858 In this case, it provides the ID of the parent task.
29861 The base priority of the task.
29864 The current state of the task. For a detailed description of the
29865 possible states, see @ref{Ada Tasks}.
29868 The name of the task.
29872 @subsubheading Example
29876 ^done,tasks=@{nr_rows="3",nr_cols="8",
29877 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29878 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29879 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29880 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29881 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29882 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29883 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29884 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29885 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29886 state="Child Termination Wait",name="main_task"@}]@}
29890 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29891 @node GDB/MI Program Execution
29892 @section @sc{gdb/mi} Program Execution
29894 These are the asynchronous commands which generate the out-of-band
29895 record @samp{*stopped}. Currently @value{GDBN} only really executes
29896 asynchronously with remote targets and this interaction is mimicked in
29899 @subheading The @code{-exec-continue} Command
29900 @findex -exec-continue
29902 @subsubheading Synopsis
29905 -exec-continue [--reverse] [--all|--thread-group N]
29908 Resumes the execution of the inferior program, which will continue
29909 to execute until it reaches a debugger stop event. If the
29910 @samp{--reverse} option is specified, execution resumes in reverse until
29911 it reaches a stop event. Stop events may include
29914 breakpoints or watchpoints
29916 signals or exceptions
29918 the end of the process (or its beginning under @samp{--reverse})
29920 the end or beginning of a replay log if one is being used.
29922 In all-stop mode (@pxref{All-Stop
29923 Mode}), may resume only one thread, or all threads, depending on the
29924 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29925 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29926 ignored in all-stop mode. If the @samp{--thread-group} options is
29927 specified, then all threads in that thread group are resumed.
29929 @subsubheading @value{GDBN} Command
29931 The corresponding @value{GDBN} corresponding is @samp{continue}.
29933 @subsubheading Example
29940 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29941 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29942 line="13",arch="i386:x86_64"@}
29947 @subheading The @code{-exec-finish} Command
29948 @findex -exec-finish
29950 @subsubheading Synopsis
29953 -exec-finish [--reverse]
29956 Resumes the execution of the inferior program until the current
29957 function is exited. Displays the results returned by the function.
29958 If the @samp{--reverse} option is specified, resumes the reverse
29959 execution of the inferior program until the point where current
29960 function was called.
29962 @subsubheading @value{GDBN} Command
29964 The corresponding @value{GDBN} command is @samp{finish}.
29966 @subsubheading Example
29968 Function returning @code{void}.
29975 *stopped,reason="function-finished",frame=@{func="main",args=[],
29976 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
29980 Function returning other than @code{void}. The name of the internal
29981 @value{GDBN} variable storing the result is printed, together with the
29988 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29989 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29990 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
29991 arch="i386:x86_64"@},
29992 gdb-result-var="$1",return-value="0"
29997 @subheading The @code{-exec-interrupt} Command
29998 @findex -exec-interrupt
30000 @subsubheading Synopsis
30003 -exec-interrupt [--all|--thread-group N]
30006 Interrupts the background execution of the target. Note how the token
30007 associated with the stop message is the one for the execution command
30008 that has been interrupted. The token for the interrupt itself only
30009 appears in the @samp{^done} output. If the user is trying to
30010 interrupt a non-running program, an error message will be printed.
30012 Note that when asynchronous execution is enabled, this command is
30013 asynchronous just like other execution commands. That is, first the
30014 @samp{^done} response will be printed, and the target stop will be
30015 reported after that using the @samp{*stopped} notification.
30017 In non-stop mode, only the context thread is interrupted by default.
30018 All threads (in all inferiors) will be interrupted if the
30019 @samp{--all} option is specified. If the @samp{--thread-group}
30020 option is specified, all threads in that group will be interrupted.
30022 @subsubheading @value{GDBN} Command
30024 The corresponding @value{GDBN} command is @samp{interrupt}.
30026 @subsubheading Example
30037 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30038 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30039 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30044 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30048 @subheading The @code{-exec-jump} Command
30051 @subsubheading Synopsis
30054 -exec-jump @var{location}
30057 Resumes execution of the inferior program at the location specified by
30058 parameter. @xref{Specify Location}, for a description of the
30059 different forms of @var{location}.
30061 @subsubheading @value{GDBN} Command
30063 The corresponding @value{GDBN} command is @samp{jump}.
30065 @subsubheading Example
30068 -exec-jump foo.c:10
30069 *running,thread-id="all"
30074 @subheading The @code{-exec-next} Command
30077 @subsubheading Synopsis
30080 -exec-next [--reverse]
30083 Resumes execution of the inferior program, stopping when the beginning
30084 of the next source line is reached.
30086 If the @samp{--reverse} option is specified, resumes reverse execution
30087 of the inferior program, stopping at the beginning of the previous
30088 source line. If you issue this command on the first line of a
30089 function, it will take you back to the caller of that function, to the
30090 source line where the function was called.
30093 @subsubheading @value{GDBN} Command
30095 The corresponding @value{GDBN} command is @samp{next}.
30097 @subsubheading Example
30103 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30108 @subheading The @code{-exec-next-instruction} Command
30109 @findex -exec-next-instruction
30111 @subsubheading Synopsis
30114 -exec-next-instruction [--reverse]
30117 Executes one machine instruction. If the instruction is a function
30118 call, continues until the function returns. If the program stops at an
30119 instruction in the middle of a source line, the address will be
30122 If the @samp{--reverse} option is specified, resumes reverse execution
30123 of the inferior program, stopping at the previous instruction. If the
30124 previously executed instruction was a return from another function,
30125 it will continue to execute in reverse until the call to that function
30126 (from the current stack frame) is reached.
30128 @subsubheading @value{GDBN} Command
30130 The corresponding @value{GDBN} command is @samp{nexti}.
30132 @subsubheading Example
30136 -exec-next-instruction
30140 *stopped,reason="end-stepping-range",
30141 addr="0x000100d4",line="5",file="hello.c"
30146 @subheading The @code{-exec-return} Command
30147 @findex -exec-return
30149 @subsubheading Synopsis
30155 Makes current function return immediately. Doesn't execute the inferior.
30156 Displays the new current frame.
30158 @subsubheading @value{GDBN} Command
30160 The corresponding @value{GDBN} command is @samp{return}.
30162 @subsubheading Example
30166 200-break-insert callee4
30167 200^done,bkpt=@{number="1",addr="0x00010734",
30168 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30173 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30174 frame=@{func="callee4",args=[],
30175 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30176 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30177 arch="i386:x86_64"@}
30183 111^done,frame=@{level="0",func="callee3",
30184 args=[@{name="strarg",
30185 value="0x11940 \"A string argument.\""@}],
30186 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30187 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30188 arch="i386:x86_64"@}
30193 @subheading The @code{-exec-run} Command
30196 @subsubheading Synopsis
30199 -exec-run [ --all | --thread-group N ] [ --start ]
30202 Starts execution of the inferior from the beginning. The inferior
30203 executes until either a breakpoint is encountered or the program
30204 exits. In the latter case the output will include an exit code, if
30205 the program has exited exceptionally.
30207 When neither the @samp{--all} nor the @samp{--thread-group} option
30208 is specified, the current inferior is started. If the
30209 @samp{--thread-group} option is specified, it should refer to a thread
30210 group of type @samp{process}, and that thread group will be started.
30211 If the @samp{--all} option is specified, then all inferiors will be started.
30213 Using the @samp{--start} option instructs the debugger to stop
30214 the execution at the start of the inferior's main subprogram,
30215 following the same behavior as the @code{start} command
30216 (@pxref{Starting}).
30218 @subsubheading @value{GDBN} Command
30220 The corresponding @value{GDBN} command is @samp{run}.
30222 @subsubheading Examples
30227 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30232 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30233 frame=@{func="main",args=[],file="recursive2.c",
30234 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30239 Program exited normally:
30247 *stopped,reason="exited-normally"
30252 Program exited exceptionally:
30260 *stopped,reason="exited",exit-code="01"
30264 Another way the program can terminate is if it receives a signal such as
30265 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30269 *stopped,reason="exited-signalled",signal-name="SIGINT",
30270 signal-meaning="Interrupt"
30274 @c @subheading -exec-signal
30277 @subheading The @code{-exec-step} Command
30280 @subsubheading Synopsis
30283 -exec-step [--reverse]
30286 Resumes execution of the inferior program, stopping when the beginning
30287 of the next source line is reached, if the next source line is not a
30288 function call. If it is, stop at the first instruction of the called
30289 function. If the @samp{--reverse} option is specified, resumes reverse
30290 execution of the inferior program, stopping at the beginning of the
30291 previously executed source line.
30293 @subsubheading @value{GDBN} Command
30295 The corresponding @value{GDBN} command is @samp{step}.
30297 @subsubheading Example
30299 Stepping into a function:
30305 *stopped,reason="end-stepping-range",
30306 frame=@{func="foo",args=[@{name="a",value="10"@},
30307 @{name="b",value="0"@}],file="recursive2.c",
30308 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30318 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30323 @subheading The @code{-exec-step-instruction} Command
30324 @findex -exec-step-instruction
30326 @subsubheading Synopsis
30329 -exec-step-instruction [--reverse]
30332 Resumes the inferior which executes one machine instruction. If the
30333 @samp{--reverse} option is specified, resumes reverse execution of the
30334 inferior program, stopping at the previously executed instruction.
30335 The output, once @value{GDBN} has stopped, will vary depending on
30336 whether we have stopped in the middle of a source line or not. In the
30337 former case, the address at which the program stopped will be printed
30340 @subsubheading @value{GDBN} Command
30342 The corresponding @value{GDBN} command is @samp{stepi}.
30344 @subsubheading Example
30348 -exec-step-instruction
30352 *stopped,reason="end-stepping-range",
30353 frame=@{func="foo",args=[],file="try.c",
30354 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30356 -exec-step-instruction
30360 *stopped,reason="end-stepping-range",
30361 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30362 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30367 @subheading The @code{-exec-until} Command
30368 @findex -exec-until
30370 @subsubheading Synopsis
30373 -exec-until [ @var{location} ]
30376 Executes the inferior until the @var{location} specified in the
30377 argument is reached. If there is no argument, the inferior executes
30378 until a source line greater than the current one is reached. The
30379 reason for stopping in this case will be @samp{location-reached}.
30381 @subsubheading @value{GDBN} Command
30383 The corresponding @value{GDBN} command is @samp{until}.
30385 @subsubheading Example
30389 -exec-until recursive2.c:6
30393 *stopped,reason="location-reached",frame=@{func="main",args=[],
30394 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30395 arch="i386:x86_64"@}
30400 @subheading -file-clear
30401 Is this going away????
30404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30405 @node GDB/MI Stack Manipulation
30406 @section @sc{gdb/mi} Stack Manipulation Commands
30408 @subheading The @code{-enable-frame-filters} Command
30409 @findex -enable-frame-filters
30412 -enable-frame-filters
30415 @value{GDBN} allows Python-based frame filters to affect the output of
30416 the MI commands relating to stack traces. As there is no way to
30417 implement this in a fully backward-compatible way, a front end must
30418 request that this functionality be enabled.
30420 Once enabled, this feature cannot be disabled.
30422 Note that if Python support has not been compiled into @value{GDBN},
30423 this command will still succeed (and do nothing).
30425 @subheading The @code{-stack-info-frame} Command
30426 @findex -stack-info-frame
30428 @subsubheading Synopsis
30434 Get info on the selected frame.
30436 @subsubheading @value{GDBN} Command
30438 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30439 (without arguments).
30441 @subsubheading Example
30446 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30447 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30448 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30449 arch="i386:x86_64"@}
30453 @subheading The @code{-stack-info-depth} Command
30454 @findex -stack-info-depth
30456 @subsubheading Synopsis
30459 -stack-info-depth [ @var{max-depth} ]
30462 Return the depth of the stack. If the integer argument @var{max-depth}
30463 is specified, do not count beyond @var{max-depth} frames.
30465 @subsubheading @value{GDBN} Command
30467 There's no equivalent @value{GDBN} command.
30469 @subsubheading Example
30471 For a stack with frame levels 0 through 11:
30478 -stack-info-depth 4
30481 -stack-info-depth 12
30484 -stack-info-depth 11
30487 -stack-info-depth 13
30492 @anchor{-stack-list-arguments}
30493 @subheading The @code{-stack-list-arguments} Command
30494 @findex -stack-list-arguments
30496 @subsubheading Synopsis
30499 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30500 [ @var{low-frame} @var{high-frame} ]
30503 Display a list of the arguments for the frames between @var{low-frame}
30504 and @var{high-frame} (inclusive). If @var{low-frame} and
30505 @var{high-frame} are not provided, list the arguments for the whole
30506 call stack. If the two arguments are equal, show the single frame
30507 at the corresponding level. It is an error if @var{low-frame} is
30508 larger than the actual number of frames. On the other hand,
30509 @var{high-frame} may be larger than the actual number of frames, in
30510 which case only existing frames will be returned.
30512 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30513 the variables; if it is 1 or @code{--all-values}, print also their
30514 values; and if it is 2 or @code{--simple-values}, print the name,
30515 type and value for simple data types, and the name and type for arrays,
30516 structures and unions. If the option @code{--no-frame-filters} is
30517 supplied, then Python frame filters will not be executed.
30519 If the @code{--skip-unavailable} option is specified, arguments that
30520 are not available are not listed. Partially available arguments
30521 are still displayed, however.
30523 Use of this command to obtain arguments in a single frame is
30524 deprecated in favor of the @samp{-stack-list-variables} command.
30526 @subsubheading @value{GDBN} Command
30528 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30529 @samp{gdb_get_args} command which partially overlaps with the
30530 functionality of @samp{-stack-list-arguments}.
30532 @subsubheading Example
30539 frame=@{level="0",addr="0x00010734",func="callee4",
30540 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30541 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30542 arch="i386:x86_64"@},
30543 frame=@{level="1",addr="0x0001076c",func="callee3",
30544 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30545 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30546 arch="i386:x86_64"@},
30547 frame=@{level="2",addr="0x0001078c",func="callee2",
30548 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30549 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30550 arch="i386:x86_64"@},
30551 frame=@{level="3",addr="0x000107b4",func="callee1",
30552 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30553 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30554 arch="i386:x86_64"@},
30555 frame=@{level="4",addr="0x000107e0",func="main",
30556 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30557 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30558 arch="i386:x86_64"@}]
30560 -stack-list-arguments 0
30563 frame=@{level="0",args=[]@},
30564 frame=@{level="1",args=[name="strarg"]@},
30565 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30566 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30567 frame=@{level="4",args=[]@}]
30569 -stack-list-arguments 1
30572 frame=@{level="0",args=[]@},
30574 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30575 frame=@{level="2",args=[
30576 @{name="intarg",value="2"@},
30577 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30578 @{frame=@{level="3",args=[
30579 @{name="intarg",value="2"@},
30580 @{name="strarg",value="0x11940 \"A string argument.\""@},
30581 @{name="fltarg",value="3.5"@}]@},
30582 frame=@{level="4",args=[]@}]
30584 -stack-list-arguments 0 2 2
30585 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30587 -stack-list-arguments 1 2 2
30588 ^done,stack-args=[frame=@{level="2",
30589 args=[@{name="intarg",value="2"@},
30590 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30594 @c @subheading -stack-list-exception-handlers
30597 @anchor{-stack-list-frames}
30598 @subheading The @code{-stack-list-frames} Command
30599 @findex -stack-list-frames
30601 @subsubheading Synopsis
30604 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30607 List the frames currently on the stack. For each frame it displays the
30612 The frame number, 0 being the topmost frame, i.e., the innermost function.
30614 The @code{$pc} value for that frame.
30618 File name of the source file where the function lives.
30619 @item @var{fullname}
30620 The full file name of the source file where the function lives.
30622 Line number corresponding to the @code{$pc}.
30624 The shared library where this function is defined. This is only given
30625 if the frame's function is not known.
30627 Frame's architecture.
30630 If invoked without arguments, this command prints a backtrace for the
30631 whole stack. If given two integer arguments, it shows the frames whose
30632 levels are between the two arguments (inclusive). If the two arguments
30633 are equal, it shows the single frame at the corresponding level. It is
30634 an error if @var{low-frame} is larger than the actual number of
30635 frames. On the other hand, @var{high-frame} may be larger than the
30636 actual number of frames, in which case only existing frames will be
30637 returned. If the option @code{--no-frame-filters} is supplied, then
30638 Python frame filters will not be executed.
30640 @subsubheading @value{GDBN} Command
30642 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30644 @subsubheading Example
30646 Full stack backtrace:
30652 [frame=@{level="0",addr="0x0001076c",func="foo",
30653 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30654 arch="i386:x86_64"@},
30655 frame=@{level="1",addr="0x000107a4",func="foo",
30656 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30657 arch="i386:x86_64"@},
30658 frame=@{level="2",addr="0x000107a4",func="foo",
30659 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30660 arch="i386:x86_64"@},
30661 frame=@{level="3",addr="0x000107a4",func="foo",
30662 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30663 arch="i386:x86_64"@},
30664 frame=@{level="4",addr="0x000107a4",func="foo",
30665 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30666 arch="i386:x86_64"@},
30667 frame=@{level="5",addr="0x000107a4",func="foo",
30668 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30669 arch="i386:x86_64"@},
30670 frame=@{level="6",addr="0x000107a4",func="foo",
30671 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30672 arch="i386:x86_64"@},
30673 frame=@{level="7",addr="0x000107a4",func="foo",
30674 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30675 arch="i386:x86_64"@},
30676 frame=@{level="8",addr="0x000107a4",func="foo",
30677 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30678 arch="i386:x86_64"@},
30679 frame=@{level="9",addr="0x000107a4",func="foo",
30680 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30681 arch="i386:x86_64"@},
30682 frame=@{level="10",addr="0x000107a4",func="foo",
30683 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30684 arch="i386:x86_64"@},
30685 frame=@{level="11",addr="0x00010738",func="main",
30686 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30687 arch="i386:x86_64"@}]
30691 Show frames between @var{low_frame} and @var{high_frame}:
30695 -stack-list-frames 3 5
30697 [frame=@{level="3",addr="0x000107a4",func="foo",
30698 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30699 arch="i386:x86_64"@},
30700 frame=@{level="4",addr="0x000107a4",func="foo",
30701 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30702 arch="i386:x86_64"@},
30703 frame=@{level="5",addr="0x000107a4",func="foo",
30704 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30705 arch="i386:x86_64"@}]
30709 Show a single frame:
30713 -stack-list-frames 3 3
30715 [frame=@{level="3",addr="0x000107a4",func="foo",
30716 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30717 arch="i386:x86_64"@}]
30722 @subheading The @code{-stack-list-locals} Command
30723 @findex -stack-list-locals
30724 @anchor{-stack-list-locals}
30726 @subsubheading Synopsis
30729 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30732 Display the local variable names for the selected frame. If
30733 @var{print-values} is 0 or @code{--no-values}, print only the names of
30734 the variables; if it is 1 or @code{--all-values}, print also their
30735 values; and if it is 2 or @code{--simple-values}, print the name,
30736 type and value for simple data types, and the name and type for arrays,
30737 structures and unions. In this last case, a frontend can immediately
30738 display the value of simple data types and create variable objects for
30739 other data types when the user wishes to explore their values in
30740 more detail. If the option @code{--no-frame-filters} is supplied, then
30741 Python frame filters will not be executed.
30743 If the @code{--skip-unavailable} option is specified, local variables
30744 that are not available are not listed. Partially available local
30745 variables are still displayed, however.
30747 This command is deprecated in favor of the
30748 @samp{-stack-list-variables} command.
30750 @subsubheading @value{GDBN} Command
30752 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30754 @subsubheading Example
30758 -stack-list-locals 0
30759 ^done,locals=[name="A",name="B",name="C"]
30761 -stack-list-locals --all-values
30762 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30763 @{name="C",value="@{1, 2, 3@}"@}]
30764 -stack-list-locals --simple-values
30765 ^done,locals=[@{name="A",type="int",value="1"@},
30766 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30770 @anchor{-stack-list-variables}
30771 @subheading The @code{-stack-list-variables} Command
30772 @findex -stack-list-variables
30774 @subsubheading Synopsis
30777 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30780 Display the names of local variables and function arguments for the selected frame. If
30781 @var{print-values} is 0 or @code{--no-values}, print only the names of
30782 the variables; if it is 1 or @code{--all-values}, print also their
30783 values; and if it is 2 or @code{--simple-values}, print the name,
30784 type and value for simple data types, and the name and type for arrays,
30785 structures and unions. If the option @code{--no-frame-filters} is
30786 supplied, then Python frame filters will not be executed.
30788 If the @code{--skip-unavailable} option is specified, local variables
30789 and arguments that are not available are not listed. Partially
30790 available arguments and local variables are still displayed, however.
30792 @subsubheading Example
30796 -stack-list-variables --thread 1 --frame 0 --all-values
30797 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30802 @subheading The @code{-stack-select-frame} Command
30803 @findex -stack-select-frame
30805 @subsubheading Synopsis
30808 -stack-select-frame @var{framenum}
30811 Change the selected frame. Select a different frame @var{framenum} on
30814 This command in deprecated in favor of passing the @samp{--frame}
30815 option to every command.
30817 @subsubheading @value{GDBN} Command
30819 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30820 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30822 @subsubheading Example
30826 -stack-select-frame 2
30831 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30832 @node GDB/MI Variable Objects
30833 @section @sc{gdb/mi} Variable Objects
30837 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30839 For the implementation of a variable debugger window (locals, watched
30840 expressions, etc.), we are proposing the adaptation of the existing code
30841 used by @code{Insight}.
30843 The two main reasons for that are:
30847 It has been proven in practice (it is already on its second generation).
30850 It will shorten development time (needless to say how important it is
30854 The original interface was designed to be used by Tcl code, so it was
30855 slightly changed so it could be used through @sc{gdb/mi}. This section
30856 describes the @sc{gdb/mi} operations that will be available and gives some
30857 hints about their use.
30859 @emph{Note}: In addition to the set of operations described here, we
30860 expect the @sc{gui} implementation of a variable window to require, at
30861 least, the following operations:
30864 @item @code{-gdb-show} @code{output-radix}
30865 @item @code{-stack-list-arguments}
30866 @item @code{-stack-list-locals}
30867 @item @code{-stack-select-frame}
30872 @subheading Introduction to Variable Objects
30874 @cindex variable objects in @sc{gdb/mi}
30876 Variable objects are "object-oriented" MI interface for examining and
30877 changing values of expressions. Unlike some other MI interfaces that
30878 work with expressions, variable objects are specifically designed for
30879 simple and efficient presentation in the frontend. A variable object
30880 is identified by string name. When a variable object is created, the
30881 frontend specifies the expression for that variable object. The
30882 expression can be a simple variable, or it can be an arbitrary complex
30883 expression, and can even involve CPU registers. After creating a
30884 variable object, the frontend can invoke other variable object
30885 operations---for example to obtain or change the value of a variable
30886 object, or to change display format.
30888 Variable objects have hierarchical tree structure. Any variable object
30889 that corresponds to a composite type, such as structure in C, has
30890 a number of child variable objects, for example corresponding to each
30891 element of a structure. A child variable object can itself have
30892 children, recursively. Recursion ends when we reach
30893 leaf variable objects, which always have built-in types. Child variable
30894 objects are created only by explicit request, so if a frontend
30895 is not interested in the children of a particular variable object, no
30896 child will be created.
30898 For a leaf variable object it is possible to obtain its value as a
30899 string, or set the value from a string. String value can be also
30900 obtained for a non-leaf variable object, but it's generally a string
30901 that only indicates the type of the object, and does not list its
30902 contents. Assignment to a non-leaf variable object is not allowed.
30904 A frontend does not need to read the values of all variable objects each time
30905 the program stops. Instead, MI provides an update command that lists all
30906 variable objects whose values has changed since the last update
30907 operation. This considerably reduces the amount of data that must
30908 be transferred to the frontend. As noted above, children variable
30909 objects are created on demand, and only leaf variable objects have a
30910 real value. As result, gdb will read target memory only for leaf
30911 variables that frontend has created.
30913 The automatic update is not always desirable. For example, a frontend
30914 might want to keep a value of some expression for future reference,
30915 and never update it. For another example, fetching memory is
30916 relatively slow for embedded targets, so a frontend might want
30917 to disable automatic update for the variables that are either not
30918 visible on the screen, or ``closed''. This is possible using so
30919 called ``frozen variable objects''. Such variable objects are never
30920 implicitly updated.
30922 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30923 fixed variable object, the expression is parsed when the variable
30924 object is created, including associating identifiers to specific
30925 variables. The meaning of expression never changes. For a floating
30926 variable object the values of variables whose names appear in the
30927 expressions are re-evaluated every time in the context of the current
30928 frame. Consider this example:
30933 struct work_state state;
30940 If a fixed variable object for the @code{state} variable is created in
30941 this function, and we enter the recursive call, the variable
30942 object will report the value of @code{state} in the top-level
30943 @code{do_work} invocation. On the other hand, a floating variable
30944 object will report the value of @code{state} in the current frame.
30946 If an expression specified when creating a fixed variable object
30947 refers to a local variable, the variable object becomes bound to the
30948 thread and frame in which the variable object is created. When such
30949 variable object is updated, @value{GDBN} makes sure that the
30950 thread/frame combination the variable object is bound to still exists,
30951 and re-evaluates the variable object in context of that thread/frame.
30953 The following is the complete set of @sc{gdb/mi} operations defined to
30954 access this functionality:
30956 @multitable @columnfractions .4 .6
30957 @item @strong{Operation}
30958 @tab @strong{Description}
30960 @item @code{-enable-pretty-printing}
30961 @tab enable Python-based pretty-printing
30962 @item @code{-var-create}
30963 @tab create a variable object
30964 @item @code{-var-delete}
30965 @tab delete the variable object and/or its children
30966 @item @code{-var-set-format}
30967 @tab set the display format of this variable
30968 @item @code{-var-show-format}
30969 @tab show the display format of this variable
30970 @item @code{-var-info-num-children}
30971 @tab tells how many children this object has
30972 @item @code{-var-list-children}
30973 @tab return a list of the object's children
30974 @item @code{-var-info-type}
30975 @tab show the type of this variable object
30976 @item @code{-var-info-expression}
30977 @tab print parent-relative expression that this variable object represents
30978 @item @code{-var-info-path-expression}
30979 @tab print full expression that this variable object represents
30980 @item @code{-var-show-attributes}
30981 @tab is this variable editable? does it exist here?
30982 @item @code{-var-evaluate-expression}
30983 @tab get the value of this variable
30984 @item @code{-var-assign}
30985 @tab set the value of this variable
30986 @item @code{-var-update}
30987 @tab update the variable and its children
30988 @item @code{-var-set-frozen}
30989 @tab set frozeness attribute
30990 @item @code{-var-set-update-range}
30991 @tab set range of children to display on update
30994 In the next subsection we describe each operation in detail and suggest
30995 how it can be used.
30997 @subheading Description And Use of Operations on Variable Objects
30999 @subheading The @code{-enable-pretty-printing} Command
31000 @findex -enable-pretty-printing
31003 -enable-pretty-printing
31006 @value{GDBN} allows Python-based visualizers to affect the output of the
31007 MI variable object commands. However, because there was no way to
31008 implement this in a fully backward-compatible way, a front end must
31009 request that this functionality be enabled.
31011 Once enabled, this feature cannot be disabled.
31013 Note that if Python support has not been compiled into @value{GDBN},
31014 this command will still succeed (and do nothing).
31016 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31017 may work differently in future versions of @value{GDBN}.
31019 @subheading The @code{-var-create} Command
31020 @findex -var-create
31022 @subsubheading Synopsis
31025 -var-create @{@var{name} | "-"@}
31026 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31029 This operation creates a variable object, which allows the monitoring of
31030 a variable, the result of an expression, a memory cell or a CPU
31033 The @var{name} parameter is the string by which the object can be
31034 referenced. It must be unique. If @samp{-} is specified, the varobj
31035 system will generate a string ``varNNNNNN'' automatically. It will be
31036 unique provided that one does not specify @var{name} of that format.
31037 The command fails if a duplicate name is found.
31039 The frame under which the expression should be evaluated can be
31040 specified by @var{frame-addr}. A @samp{*} indicates that the current
31041 frame should be used. A @samp{@@} indicates that a floating variable
31042 object must be created.
31044 @var{expression} is any expression valid on the current language set (must not
31045 begin with a @samp{*}), or one of the following:
31049 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31052 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31055 @samp{$@var{regname}} --- a CPU register name
31058 @cindex dynamic varobj
31059 A varobj's contents may be provided by a Python-based pretty-printer. In this
31060 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31061 have slightly different semantics in some cases. If the
31062 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31063 will never create a dynamic varobj. This ensures backward
31064 compatibility for existing clients.
31066 @subsubheading Result
31068 This operation returns attributes of the newly-created varobj. These
31073 The name of the varobj.
31076 The number of children of the varobj. This number is not necessarily
31077 reliable for a dynamic varobj. Instead, you must examine the
31078 @samp{has_more} attribute.
31081 The varobj's scalar value. For a varobj whose type is some sort of
31082 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31083 will not be interesting.
31086 The varobj's type. This is a string representation of the type, as
31087 would be printed by the @value{GDBN} CLI. If @samp{print object}
31088 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31089 @emph{actual} (derived) type of the object is shown rather than the
31090 @emph{declared} one.
31093 If a variable object is bound to a specific thread, then this is the
31094 thread's global identifier.
31097 For a dynamic varobj, this indicates whether there appear to be any
31098 children available. For a non-dynamic varobj, this will be 0.
31101 This attribute will be present and have the value @samp{1} if the
31102 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31103 then this attribute will not be present.
31106 A dynamic varobj can supply a display hint to the front end. The
31107 value comes directly from the Python pretty-printer object's
31108 @code{display_hint} method. @xref{Pretty Printing API}.
31111 Typical output will look like this:
31114 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31115 has_more="@var{has_more}"
31119 @subheading The @code{-var-delete} Command
31120 @findex -var-delete
31122 @subsubheading Synopsis
31125 -var-delete [ -c ] @var{name}
31128 Deletes a previously created variable object and all of its children.
31129 With the @samp{-c} option, just deletes the children.
31131 Returns an error if the object @var{name} is not found.
31134 @subheading The @code{-var-set-format} Command
31135 @findex -var-set-format
31137 @subsubheading Synopsis
31140 -var-set-format @var{name} @var{format-spec}
31143 Sets the output format for the value of the object @var{name} to be
31146 @anchor{-var-set-format}
31147 The syntax for the @var{format-spec} is as follows:
31150 @var{format-spec} @expansion{}
31151 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
31154 The natural format is the default format choosen automatically
31155 based on the variable type (like decimal for an @code{int}, hex
31156 for pointers, etc.).
31158 The zero-hexadecimal format has a representation similar to hexadecimal
31159 but with padding zeroes to the left of the value. For example, a 32-bit
31160 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
31161 zero-hexadecimal format.
31163 For a variable with children, the format is set only on the
31164 variable itself, and the children are not affected.
31166 @subheading The @code{-var-show-format} Command
31167 @findex -var-show-format
31169 @subsubheading Synopsis
31172 -var-show-format @var{name}
31175 Returns the format used to display the value of the object @var{name}.
31178 @var{format} @expansion{}
31183 @subheading The @code{-var-info-num-children} Command
31184 @findex -var-info-num-children
31186 @subsubheading Synopsis
31189 -var-info-num-children @var{name}
31192 Returns the number of children of a variable object @var{name}:
31198 Note that this number is not completely reliable for a dynamic varobj.
31199 It will return the current number of children, but more children may
31203 @subheading The @code{-var-list-children} Command
31204 @findex -var-list-children
31206 @subsubheading Synopsis
31209 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31211 @anchor{-var-list-children}
31213 Return a list of the children of the specified variable object and
31214 create variable objects for them, if they do not already exist. With
31215 a single argument or if @var{print-values} has a value of 0 or
31216 @code{--no-values}, print only the names of the variables; if
31217 @var{print-values} is 1 or @code{--all-values}, also print their
31218 values; and if it is 2 or @code{--simple-values} print the name and
31219 value for simple data types and just the name for arrays, structures
31222 @var{from} and @var{to}, if specified, indicate the range of children
31223 to report. If @var{from} or @var{to} is less than zero, the range is
31224 reset and all children will be reported. Otherwise, children starting
31225 at @var{from} (zero-based) and up to and excluding @var{to} will be
31228 If a child range is requested, it will only affect the current call to
31229 @code{-var-list-children}, but not future calls to @code{-var-update}.
31230 For this, you must instead use @code{-var-set-update-range}. The
31231 intent of this approach is to enable a front end to implement any
31232 update approach it likes; for example, scrolling a view may cause the
31233 front end to request more children with @code{-var-list-children}, and
31234 then the front end could call @code{-var-set-update-range} with a
31235 different range to ensure that future updates are restricted to just
31238 For each child the following results are returned:
31243 Name of the variable object created for this child.
31246 The expression to be shown to the user by the front end to designate this child.
31247 For example this may be the name of a structure member.
31249 For a dynamic varobj, this value cannot be used to form an
31250 expression. There is no way to do this at all with a dynamic varobj.
31252 For C/C@t{++} structures there are several pseudo children returned to
31253 designate access qualifiers. For these pseudo children @var{exp} is
31254 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31255 type and value are not present.
31257 A dynamic varobj will not report the access qualifying
31258 pseudo-children, regardless of the language. This information is not
31259 available at all with a dynamic varobj.
31262 Number of children this child has. For a dynamic varobj, this will be
31266 The type of the child. If @samp{print object}
31267 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31268 @emph{actual} (derived) type of the object is shown rather than the
31269 @emph{declared} one.
31272 If values were requested, this is the value.
31275 If this variable object is associated with a thread, this is the
31276 thread's global thread id. Otherwise this result is not present.
31279 If the variable object is frozen, this variable will be present with a value of 1.
31282 A dynamic varobj can supply a display hint to the front end. The
31283 value comes directly from the Python pretty-printer object's
31284 @code{display_hint} method. @xref{Pretty Printing API}.
31287 This attribute will be present and have the value @samp{1} if the
31288 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31289 then this attribute will not be present.
31293 The result may have its own attributes:
31297 A dynamic varobj can supply a display hint to the front end. The
31298 value comes directly from the Python pretty-printer object's
31299 @code{display_hint} method. @xref{Pretty Printing API}.
31302 This is an integer attribute which is nonzero if there are children
31303 remaining after the end of the selected range.
31306 @subsubheading Example
31310 -var-list-children n
31311 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31312 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31314 -var-list-children --all-values n
31315 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31316 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31320 @subheading The @code{-var-info-type} Command
31321 @findex -var-info-type
31323 @subsubheading Synopsis
31326 -var-info-type @var{name}
31329 Returns the type of the specified variable @var{name}. The type is
31330 returned as a string in the same format as it is output by the
31334 type=@var{typename}
31338 @subheading The @code{-var-info-expression} Command
31339 @findex -var-info-expression
31341 @subsubheading Synopsis
31344 -var-info-expression @var{name}
31347 Returns a string that is suitable for presenting this
31348 variable object in user interface. The string is generally
31349 not valid expression in the current language, and cannot be evaluated.
31351 For example, if @code{a} is an array, and variable object
31352 @code{A} was created for @code{a}, then we'll get this output:
31355 (gdb) -var-info-expression A.1
31356 ^done,lang="C",exp="1"
31360 Here, the value of @code{lang} is the language name, which can be
31361 found in @ref{Supported Languages}.
31363 Note that the output of the @code{-var-list-children} command also
31364 includes those expressions, so the @code{-var-info-expression} command
31367 @subheading The @code{-var-info-path-expression} Command
31368 @findex -var-info-path-expression
31370 @subsubheading Synopsis
31373 -var-info-path-expression @var{name}
31376 Returns an expression that can be evaluated in the current
31377 context and will yield the same value that a variable object has.
31378 Compare this with the @code{-var-info-expression} command, which
31379 result can be used only for UI presentation. Typical use of
31380 the @code{-var-info-path-expression} command is creating a
31381 watchpoint from a variable object.
31383 This command is currently not valid for children of a dynamic varobj,
31384 and will give an error when invoked on one.
31386 For example, suppose @code{C} is a C@t{++} class, derived from class
31387 @code{Base}, and that the @code{Base} class has a member called
31388 @code{m_size}. Assume a variable @code{c} is has the type of
31389 @code{C} and a variable object @code{C} was created for variable
31390 @code{c}. Then, we'll get this output:
31392 (gdb) -var-info-path-expression C.Base.public.m_size
31393 ^done,path_expr=((Base)c).m_size)
31396 @subheading The @code{-var-show-attributes} Command
31397 @findex -var-show-attributes
31399 @subsubheading Synopsis
31402 -var-show-attributes @var{name}
31405 List attributes of the specified variable object @var{name}:
31408 status=@var{attr} [ ( ,@var{attr} )* ]
31412 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31414 @subheading The @code{-var-evaluate-expression} Command
31415 @findex -var-evaluate-expression
31417 @subsubheading Synopsis
31420 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31423 Evaluates the expression that is represented by the specified variable
31424 object and returns its value as a string. The format of the string
31425 can be specified with the @samp{-f} option. The possible values of
31426 this option are the same as for @code{-var-set-format}
31427 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31428 the current display format will be used. The current display format
31429 can be changed using the @code{-var-set-format} command.
31435 Note that one must invoke @code{-var-list-children} for a variable
31436 before the value of a child variable can be evaluated.
31438 @subheading The @code{-var-assign} Command
31439 @findex -var-assign
31441 @subsubheading Synopsis
31444 -var-assign @var{name} @var{expression}
31447 Assigns the value of @var{expression} to the variable object specified
31448 by @var{name}. The object must be @samp{editable}. If the variable's
31449 value is altered by the assign, the variable will show up in any
31450 subsequent @code{-var-update} list.
31452 @subsubheading Example
31460 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31464 @subheading The @code{-var-update} Command
31465 @findex -var-update
31467 @subsubheading Synopsis
31470 -var-update [@var{print-values}] @{@var{name} | "*"@}
31473 Reevaluate the expressions corresponding to the variable object
31474 @var{name} and all its direct and indirect children, and return the
31475 list of variable objects whose values have changed; @var{name} must
31476 be a root variable object. Here, ``changed'' means that the result of
31477 @code{-var-evaluate-expression} before and after the
31478 @code{-var-update} is different. If @samp{*} is used as the variable
31479 object names, all existing variable objects are updated, except
31480 for frozen ones (@pxref{-var-set-frozen}). The option
31481 @var{print-values} determines whether both names and values, or just
31482 names are printed. The possible values of this option are the same
31483 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31484 recommended to use the @samp{--all-values} option, to reduce the
31485 number of MI commands needed on each program stop.
31487 With the @samp{*} parameter, if a variable object is bound to a
31488 currently running thread, it will not be updated, without any
31491 If @code{-var-set-update-range} was previously used on a varobj, then
31492 only the selected range of children will be reported.
31494 @code{-var-update} reports all the changed varobjs in a tuple named
31497 Each item in the change list is itself a tuple holding:
31501 The name of the varobj.
31504 If values were requested for this update, then this field will be
31505 present and will hold the value of the varobj.
31508 @anchor{-var-update}
31509 This field is a string which may take one of three values:
31513 The variable object's current value is valid.
31516 The variable object does not currently hold a valid value but it may
31517 hold one in the future if its associated expression comes back into
31521 The variable object no longer holds a valid value.
31522 This can occur when the executable file being debugged has changed,
31523 either through recompilation or by using the @value{GDBN} @code{file}
31524 command. The front end should normally choose to delete these variable
31528 In the future new values may be added to this list so the front should
31529 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31532 This is only present if the varobj is still valid. If the type
31533 changed, then this will be the string @samp{true}; otherwise it will
31536 When a varobj's type changes, its children are also likely to have
31537 become incorrect. Therefore, the varobj's children are automatically
31538 deleted when this attribute is @samp{true}. Also, the varobj's update
31539 range, when set using the @code{-var-set-update-range} command, is
31543 If the varobj's type changed, then this field will be present and will
31546 @item new_num_children
31547 For a dynamic varobj, if the number of children changed, or if the
31548 type changed, this will be the new number of children.
31550 The @samp{numchild} field in other varobj responses is generally not
31551 valid for a dynamic varobj -- it will show the number of children that
31552 @value{GDBN} knows about, but because dynamic varobjs lazily
31553 instantiate their children, this will not reflect the number of
31554 children which may be available.
31556 The @samp{new_num_children} attribute only reports changes to the
31557 number of children known by @value{GDBN}. This is the only way to
31558 detect whether an update has removed children (which necessarily can
31559 only happen at the end of the update range).
31562 The display hint, if any.
31565 This is an integer value, which will be 1 if there are more children
31566 available outside the varobj's update range.
31569 This attribute will be present and have the value @samp{1} if the
31570 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31571 then this attribute will not be present.
31574 If new children were added to a dynamic varobj within the selected
31575 update range (as set by @code{-var-set-update-range}), then they will
31576 be listed in this attribute.
31579 @subsubheading Example
31586 -var-update --all-values var1
31587 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31588 type_changed="false"@}]
31592 @subheading The @code{-var-set-frozen} Command
31593 @findex -var-set-frozen
31594 @anchor{-var-set-frozen}
31596 @subsubheading Synopsis
31599 -var-set-frozen @var{name} @var{flag}
31602 Set the frozenness flag on the variable object @var{name}. The
31603 @var{flag} parameter should be either @samp{1} to make the variable
31604 frozen or @samp{0} to make it unfrozen. If a variable object is
31605 frozen, then neither itself, nor any of its children, are
31606 implicitly updated by @code{-var-update} of
31607 a parent variable or by @code{-var-update *}. Only
31608 @code{-var-update} of the variable itself will update its value and
31609 values of its children. After a variable object is unfrozen, it is
31610 implicitly updated by all subsequent @code{-var-update} operations.
31611 Unfreezing a variable does not update it, only subsequent
31612 @code{-var-update} does.
31614 @subsubheading Example
31618 -var-set-frozen V 1
31623 @subheading The @code{-var-set-update-range} command
31624 @findex -var-set-update-range
31625 @anchor{-var-set-update-range}
31627 @subsubheading Synopsis
31630 -var-set-update-range @var{name} @var{from} @var{to}
31633 Set the range of children to be returned by future invocations of
31634 @code{-var-update}.
31636 @var{from} and @var{to} indicate the range of children to report. If
31637 @var{from} or @var{to} is less than zero, the range is reset and all
31638 children will be reported. Otherwise, children starting at @var{from}
31639 (zero-based) and up to and excluding @var{to} will be reported.
31641 @subsubheading Example
31645 -var-set-update-range V 1 2
31649 @subheading The @code{-var-set-visualizer} command
31650 @findex -var-set-visualizer
31651 @anchor{-var-set-visualizer}
31653 @subsubheading Synopsis
31656 -var-set-visualizer @var{name} @var{visualizer}
31659 Set a visualizer for the variable object @var{name}.
31661 @var{visualizer} is the visualizer to use. The special value
31662 @samp{None} means to disable any visualizer in use.
31664 If not @samp{None}, @var{visualizer} must be a Python expression.
31665 This expression must evaluate to a callable object which accepts a
31666 single argument. @value{GDBN} will call this object with the value of
31667 the varobj @var{name} as an argument (this is done so that the same
31668 Python pretty-printing code can be used for both the CLI and MI).
31669 When called, this object must return an object which conforms to the
31670 pretty-printing interface (@pxref{Pretty Printing API}).
31672 The pre-defined function @code{gdb.default_visualizer} may be used to
31673 select a visualizer by following the built-in process
31674 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31675 a varobj is created, and so ordinarily is not needed.
31677 This feature is only available if Python support is enabled. The MI
31678 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31679 can be used to check this.
31681 @subsubheading Example
31683 Resetting the visualizer:
31687 -var-set-visualizer V None
31691 Reselecting the default (type-based) visualizer:
31695 -var-set-visualizer V gdb.default_visualizer
31699 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31700 can be used to instantiate this class for a varobj:
31704 -var-set-visualizer V "lambda val: SomeClass()"
31708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31709 @node GDB/MI Data Manipulation
31710 @section @sc{gdb/mi} Data Manipulation
31712 @cindex data manipulation, in @sc{gdb/mi}
31713 @cindex @sc{gdb/mi}, data manipulation
31714 This section describes the @sc{gdb/mi} commands that manipulate data:
31715 examine memory and registers, evaluate expressions, etc.
31717 For details about what an addressable memory unit is,
31718 @pxref{addressable memory unit}.
31720 @c REMOVED FROM THE INTERFACE.
31721 @c @subheading -data-assign
31722 @c Change the value of a program variable. Plenty of side effects.
31723 @c @subsubheading GDB Command
31725 @c @subsubheading Example
31728 @subheading The @code{-data-disassemble} Command
31729 @findex -data-disassemble
31731 @subsubheading Synopsis
31735 [ -s @var{start-addr} -e @var{end-addr} ]
31736 | [ -a @var{addr} ]
31737 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31745 @item @var{start-addr}
31746 is the beginning address (or @code{$pc})
31747 @item @var{end-addr}
31750 is an address anywhere within (or the name of) the function to
31751 disassemble. If an address is specified, the whole function
31752 surrounding that address will be disassembled. If a name is
31753 specified, the whole function with that name will be disassembled.
31754 @item @var{filename}
31755 is the name of the file to disassemble
31756 @item @var{linenum}
31757 is the line number to disassemble around
31759 is the number of disassembly lines to be produced. If it is -1,
31760 the whole function will be disassembled, in case no @var{end-addr} is
31761 specified. If @var{end-addr} is specified as a non-zero value, and
31762 @var{lines} is lower than the number of disassembly lines between
31763 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31764 displayed; if @var{lines} is higher than the number of lines between
31765 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31770 @item 0 disassembly only
31771 @item 1 mixed source and disassembly (deprecated)
31772 @item 2 disassembly with raw opcodes
31773 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31774 @item 4 mixed source and disassembly
31775 @item 5 mixed source and disassembly with raw opcodes
31778 Modes 1 and 3 are deprecated. The output is ``source centric''
31779 which hasn't proved useful in practice.
31780 @xref{Machine Code}, for a discussion of the difference between
31781 @code{/m} and @code{/s} output of the @code{disassemble} command.
31784 @subsubheading Result
31786 The result of the @code{-data-disassemble} command will be a list named
31787 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31788 used with the @code{-data-disassemble} command.
31790 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31795 The address at which this instruction was disassembled.
31798 The name of the function this instruction is within.
31801 The decimal offset in bytes from the start of @samp{func-name}.
31804 The text disassembly for this @samp{address}.
31807 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31808 bytes for the @samp{inst} field.
31812 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31813 @samp{src_and_asm_line}, each of which has the following fields:
31817 The line number within @samp{file}.
31820 The file name from the compilation unit. This might be an absolute
31821 file name or a relative file name depending on the compile command
31825 Absolute file name of @samp{file}. It is converted to a canonical form
31826 using the source file search path
31827 (@pxref{Source Path, ,Specifying Source Directories})
31828 and after resolving all the symbolic links.
31830 If the source file is not found this field will contain the path as
31831 present in the debug information.
31833 @item line_asm_insn
31834 This is a list of tuples containing the disassembly for @samp{line} in
31835 @samp{file}. The fields of each tuple are the same as for
31836 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31837 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31842 Note that whatever included in the @samp{inst} field, is not
31843 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31846 @subsubheading @value{GDBN} Command
31848 The corresponding @value{GDBN} command is @samp{disassemble}.
31850 @subsubheading Example
31852 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31856 -data-disassemble -s $pc -e "$pc + 20" -- 0
31859 @{address="0x000107c0",func-name="main",offset="4",
31860 inst="mov 2, %o0"@},
31861 @{address="0x000107c4",func-name="main",offset="8",
31862 inst="sethi %hi(0x11800), %o2"@},
31863 @{address="0x000107c8",func-name="main",offset="12",
31864 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31865 @{address="0x000107cc",func-name="main",offset="16",
31866 inst="sethi %hi(0x11800), %o2"@},
31867 @{address="0x000107d0",func-name="main",offset="20",
31868 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31872 Disassemble the whole @code{main} function. Line 32 is part of
31876 -data-disassemble -f basics.c -l 32 -- 0
31878 @{address="0x000107bc",func-name="main",offset="0",
31879 inst="save %sp, -112, %sp"@},
31880 @{address="0x000107c0",func-name="main",offset="4",
31881 inst="mov 2, %o0"@},
31882 @{address="0x000107c4",func-name="main",offset="8",
31883 inst="sethi %hi(0x11800), %o2"@},
31885 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31886 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31890 Disassemble 3 instructions from the start of @code{main}:
31894 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31896 @{address="0x000107bc",func-name="main",offset="0",
31897 inst="save %sp, -112, %sp"@},
31898 @{address="0x000107c0",func-name="main",offset="4",
31899 inst="mov 2, %o0"@},
31900 @{address="0x000107c4",func-name="main",offset="8",
31901 inst="sethi %hi(0x11800), %o2"@}]
31905 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31909 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31911 src_and_asm_line=@{line="31",
31912 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31913 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31914 line_asm_insn=[@{address="0x000107bc",
31915 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31916 src_and_asm_line=@{line="32",
31917 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31918 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31919 line_asm_insn=[@{address="0x000107c0",
31920 func-name="main",offset="4",inst="mov 2, %o0"@},
31921 @{address="0x000107c4",func-name="main",offset="8",
31922 inst="sethi %hi(0x11800), %o2"@}]@}]
31927 @subheading The @code{-data-evaluate-expression} Command
31928 @findex -data-evaluate-expression
31930 @subsubheading Synopsis
31933 -data-evaluate-expression @var{expr}
31936 Evaluate @var{expr} as an expression. The expression could contain an
31937 inferior function call. The function call will execute synchronously.
31938 If the expression contains spaces, it must be enclosed in double quotes.
31940 @subsubheading @value{GDBN} Command
31942 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31943 @samp{call}. In @code{gdbtk} only, there's a corresponding
31944 @samp{gdb_eval} command.
31946 @subsubheading Example
31948 In the following example, the numbers that precede the commands are the
31949 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31950 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31954 211-data-evaluate-expression A
31957 311-data-evaluate-expression &A
31958 311^done,value="0xefffeb7c"
31960 411-data-evaluate-expression A+3
31963 511-data-evaluate-expression "A + 3"
31969 @subheading The @code{-data-list-changed-registers} Command
31970 @findex -data-list-changed-registers
31972 @subsubheading Synopsis
31975 -data-list-changed-registers
31978 Display a list of the registers that have changed.
31980 @subsubheading @value{GDBN} Command
31982 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31983 has the corresponding command @samp{gdb_changed_register_list}.
31985 @subsubheading Example
31987 On a PPC MBX board:
31995 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31996 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31997 line="5",arch="powerpc"@}
31999 -data-list-changed-registers
32000 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32001 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32002 "24","25","26","27","28","30","31","64","65","66","67","69"]
32007 @subheading The @code{-data-list-register-names} Command
32008 @findex -data-list-register-names
32010 @subsubheading Synopsis
32013 -data-list-register-names [ ( @var{regno} )+ ]
32016 Show a list of register names for the current target. If no arguments
32017 are given, it shows a list of the names of all the registers. If
32018 integer numbers are given as arguments, it will print a list of the
32019 names of the registers corresponding to the arguments. To ensure
32020 consistency between a register name and its number, the output list may
32021 include empty register names.
32023 @subsubheading @value{GDBN} Command
32025 @value{GDBN} does not have a command which corresponds to
32026 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32027 corresponding command @samp{gdb_regnames}.
32029 @subsubheading Example
32031 For the PPC MBX board:
32034 -data-list-register-names
32035 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32036 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32037 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32038 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32039 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32040 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32041 "", "pc","ps","cr","lr","ctr","xer"]
32043 -data-list-register-names 1 2 3
32044 ^done,register-names=["r1","r2","r3"]
32048 @subheading The @code{-data-list-register-values} Command
32049 @findex -data-list-register-values
32051 @subsubheading Synopsis
32054 -data-list-register-values
32055 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32058 Display the registers' contents. The format according to which the
32059 registers' contents are to be returned is given by @var{fmt}, followed
32060 by an optional list of numbers specifying the registers to display. A
32061 missing list of numbers indicates that the contents of all the
32062 registers must be returned. The @code{--skip-unavailable} option
32063 indicates that only the available registers are to be returned.
32065 Allowed formats for @var{fmt} are:
32082 @subsubheading @value{GDBN} Command
32084 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32085 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32087 @subsubheading Example
32089 For a PPC MBX board (note: line breaks are for readability only, they
32090 don't appear in the actual output):
32094 -data-list-register-values r 64 65
32095 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32096 @{number="65",value="0x00029002"@}]
32098 -data-list-register-values x
32099 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32100 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32101 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32102 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32103 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32104 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32105 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32106 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32107 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32108 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32109 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32110 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32111 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32112 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32113 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32114 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32115 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32116 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32117 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32118 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32119 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32120 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32121 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32122 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32123 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32124 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32125 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32126 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32127 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32128 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32129 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32130 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32131 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32132 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32133 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32134 @{number="69",value="0x20002b03"@}]
32139 @subheading The @code{-data-read-memory} Command
32140 @findex -data-read-memory
32142 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32144 @subsubheading Synopsis
32147 -data-read-memory [ -o @var{byte-offset} ]
32148 @var{address} @var{word-format} @var{word-size}
32149 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32156 @item @var{address}
32157 An expression specifying the address of the first memory word to be
32158 read. Complex expressions containing embedded white space should be
32159 quoted using the C convention.
32161 @item @var{word-format}
32162 The format to be used to print the memory words. The notation is the
32163 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32166 @item @var{word-size}
32167 The size of each memory word in bytes.
32169 @item @var{nr-rows}
32170 The number of rows in the output table.
32172 @item @var{nr-cols}
32173 The number of columns in the output table.
32176 If present, indicates that each row should include an @sc{ascii} dump. The
32177 value of @var{aschar} is used as a padding character when a byte is not a
32178 member of the printable @sc{ascii} character set (printable @sc{ascii}
32179 characters are those whose code is between 32 and 126, inclusively).
32181 @item @var{byte-offset}
32182 An offset to add to the @var{address} before fetching memory.
32185 This command displays memory contents as a table of @var{nr-rows} by
32186 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32187 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32188 (returned as @samp{total-bytes}). Should less than the requested number
32189 of bytes be returned by the target, the missing words are identified
32190 using @samp{N/A}. The number of bytes read from the target is returned
32191 in @samp{nr-bytes} and the starting address used to read memory in
32194 The address of the next/previous row or page is available in
32195 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32198 @subsubheading @value{GDBN} Command
32200 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32201 @samp{gdb_get_mem} memory read command.
32203 @subsubheading Example
32205 Read six bytes of memory starting at @code{bytes+6} but then offset by
32206 @code{-6} bytes. Format as three rows of two columns. One byte per
32207 word. Display each word in hex.
32211 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32212 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32213 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32214 prev-page="0x0000138a",memory=[
32215 @{addr="0x00001390",data=["0x00","0x01"]@},
32216 @{addr="0x00001392",data=["0x02","0x03"]@},
32217 @{addr="0x00001394",data=["0x04","0x05"]@}]
32221 Read two bytes of memory starting at address @code{shorts + 64} and
32222 display as a single word formatted in decimal.
32226 5-data-read-memory shorts+64 d 2 1 1
32227 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32228 next-row="0x00001512",prev-row="0x0000150e",
32229 next-page="0x00001512",prev-page="0x0000150e",memory=[
32230 @{addr="0x00001510",data=["128"]@}]
32234 Read thirty two bytes of memory starting at @code{bytes+16} and format
32235 as eight rows of four columns. Include a string encoding with @samp{x}
32236 used as the non-printable character.
32240 4-data-read-memory bytes+16 x 1 8 4 x
32241 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32242 next-row="0x000013c0",prev-row="0x0000139c",
32243 next-page="0x000013c0",prev-page="0x00001380",memory=[
32244 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32245 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32246 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32247 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32248 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32249 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32250 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32251 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32255 @subheading The @code{-data-read-memory-bytes} Command
32256 @findex -data-read-memory-bytes
32258 @subsubheading Synopsis
32261 -data-read-memory-bytes [ -o @var{offset} ]
32262 @var{address} @var{count}
32269 @item @var{address}
32270 An expression specifying the address of the first addressable memory unit
32271 to be read. Complex expressions containing embedded white space should be
32272 quoted using the C convention.
32275 The number of addressable memory units to read. This should be an integer
32279 The offset relative to @var{address} at which to start reading. This
32280 should be an integer literal. This option is provided so that a frontend
32281 is not required to first evaluate address and then perform address
32282 arithmetics itself.
32286 This command attempts to read all accessible memory regions in the
32287 specified range. First, all regions marked as unreadable in the memory
32288 map (if one is defined) will be skipped. @xref{Memory Region
32289 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32290 regions. For each one, if reading full region results in an errors,
32291 @value{GDBN} will try to read a subset of the region.
32293 In general, every single memory unit in the region may be readable or not,
32294 and the only way to read every readable unit is to try a read at
32295 every address, which is not practical. Therefore, @value{GDBN} will
32296 attempt to read all accessible memory units at either beginning or the end
32297 of the region, using a binary division scheme. This heuristic works
32298 well for reading accross a memory map boundary. Note that if a region
32299 has a readable range that is neither at the beginning or the end,
32300 @value{GDBN} will not read it.
32302 The result record (@pxref{GDB/MI Result Records}) that is output of
32303 the command includes a field named @samp{memory} whose content is a
32304 list of tuples. Each tuple represent a successfully read memory block
32305 and has the following fields:
32309 The start address of the memory block, as hexadecimal literal.
32312 The end address of the memory block, as hexadecimal literal.
32315 The offset of the memory block, as hexadecimal literal, relative to
32316 the start address passed to @code{-data-read-memory-bytes}.
32319 The contents of the memory block, in hex.
32325 @subsubheading @value{GDBN} Command
32327 The corresponding @value{GDBN} command is @samp{x}.
32329 @subsubheading Example
32333 -data-read-memory-bytes &a 10
32334 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32336 contents="01000000020000000300"@}]
32341 @subheading The @code{-data-write-memory-bytes} Command
32342 @findex -data-write-memory-bytes
32344 @subsubheading Synopsis
32347 -data-write-memory-bytes @var{address} @var{contents}
32348 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32355 @item @var{address}
32356 An expression specifying the address of the first addressable memory unit
32357 to be written. Complex expressions containing embedded white space should
32358 be quoted using the C convention.
32360 @item @var{contents}
32361 The hex-encoded data to write. It is an error if @var{contents} does
32362 not represent an integral number of addressable memory units.
32365 Optional argument indicating the number of addressable memory units to be
32366 written. If @var{count} is greater than @var{contents}' length,
32367 @value{GDBN} will repeatedly write @var{contents} until it fills
32368 @var{count} memory units.
32372 @subsubheading @value{GDBN} Command
32374 There's no corresponding @value{GDBN} command.
32376 @subsubheading Example
32380 -data-write-memory-bytes &a "aabbccdd"
32387 -data-write-memory-bytes &a "aabbccdd" 16e
32392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32393 @node GDB/MI Tracepoint Commands
32394 @section @sc{gdb/mi} Tracepoint Commands
32396 The commands defined in this section implement MI support for
32397 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32399 @subheading The @code{-trace-find} Command
32400 @findex -trace-find
32402 @subsubheading Synopsis
32405 -trace-find @var{mode} [@var{parameters}@dots{}]
32408 Find a trace frame using criteria defined by @var{mode} and
32409 @var{parameters}. The following table lists permissible
32410 modes and their parameters. For details of operation, see @ref{tfind}.
32415 No parameters are required. Stops examining trace frames.
32418 An integer is required as parameter. Selects tracepoint frame with
32421 @item tracepoint-number
32422 An integer is required as parameter. Finds next
32423 trace frame that corresponds to tracepoint with the specified number.
32426 An address is required as parameter. Finds
32427 next trace frame that corresponds to any tracepoint at the specified
32430 @item pc-inside-range
32431 Two addresses are required as parameters. Finds next trace
32432 frame that corresponds to a tracepoint at an address inside the
32433 specified range. Both bounds are considered to be inside the range.
32435 @item pc-outside-range
32436 Two addresses are required as parameters. Finds
32437 next trace frame that corresponds to a tracepoint at an address outside
32438 the specified range. Both bounds are considered to be inside the range.
32441 Line specification is required as parameter. @xref{Specify Location}.
32442 Finds next trace frame that corresponds to a tracepoint at
32443 the specified location.
32447 If @samp{none} was passed as @var{mode}, the response does not
32448 have fields. Otherwise, the response may have the following fields:
32452 This field has either @samp{0} or @samp{1} as the value, depending
32453 on whether a matching tracepoint was found.
32456 The index of the found traceframe. This field is present iff
32457 the @samp{found} field has value of @samp{1}.
32460 The index of the found tracepoint. This field is present iff
32461 the @samp{found} field has value of @samp{1}.
32464 The information about the frame corresponding to the found trace
32465 frame. This field is present only if a trace frame was found.
32466 @xref{GDB/MI Frame Information}, for description of this field.
32470 @subsubheading @value{GDBN} Command
32472 The corresponding @value{GDBN} command is @samp{tfind}.
32474 @subheading -trace-define-variable
32475 @findex -trace-define-variable
32477 @subsubheading Synopsis
32480 -trace-define-variable @var{name} [ @var{value} ]
32483 Create trace variable @var{name} if it does not exist. If
32484 @var{value} is specified, sets the initial value of the specified
32485 trace variable to that value. Note that the @var{name} should start
32486 with the @samp{$} character.
32488 @subsubheading @value{GDBN} Command
32490 The corresponding @value{GDBN} command is @samp{tvariable}.
32492 @subheading The @code{-trace-frame-collected} Command
32493 @findex -trace-frame-collected
32495 @subsubheading Synopsis
32498 -trace-frame-collected
32499 [--var-print-values @var{var_pval}]
32500 [--comp-print-values @var{comp_pval}]
32501 [--registers-format @var{regformat}]
32502 [--memory-contents]
32505 This command returns the set of collected objects, register names,
32506 trace state variable names, memory ranges and computed expressions
32507 that have been collected at a particular trace frame. The optional
32508 parameters to the command affect the output format in different ways.
32509 See the output description table below for more details.
32511 The reported names can be used in the normal manner to create
32512 varobjs and inspect the objects themselves. The items returned by
32513 this command are categorized so that it is clear which is a variable,
32514 which is a register, which is a trace state variable, which is a
32515 memory range and which is a computed expression.
32517 For instance, if the actions were
32519 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32520 collect *(int*)0xaf02bef0@@40
32524 the object collected in its entirety would be @code{myVar}. The
32525 object @code{myArray} would be partially collected, because only the
32526 element at index @code{myIndex} would be collected. The remaining
32527 objects would be computed expressions.
32529 An example output would be:
32533 -trace-frame-collected
32535 explicit-variables=[@{name="myVar",value="1"@}],
32536 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32537 @{name="myObj.field",value="0"@},
32538 @{name="myPtr->field",value="1"@},
32539 @{name="myCount + 2",value="3"@},
32540 @{name="$tvar1 + 1",value="43970027"@}],
32541 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32542 @{number="1",value="0x0"@},
32543 @{number="2",value="0x4"@},
32545 @{number="125",value="0x0"@}],
32546 tvars=[@{name="$tvar1",current="43970026"@}],
32547 memory=[@{address="0x0000000000602264",length="4"@},
32548 @{address="0x0000000000615bc0",length="4"@}]
32555 @item explicit-variables
32556 The set of objects that have been collected in their entirety (as
32557 opposed to collecting just a few elements of an array or a few struct
32558 members). For each object, its name and value are printed.
32559 The @code{--var-print-values} option affects how or whether the value
32560 field is output. If @var{var_pval} is 0, then print only the names;
32561 if it is 1, print also their values; and if it is 2, print the name,
32562 type and value for simple data types, and the name and type for
32563 arrays, structures and unions.
32565 @item computed-expressions
32566 The set of computed expressions that have been collected at the
32567 current trace frame. The @code{--comp-print-values} option affects
32568 this set like the @code{--var-print-values} option affects the
32569 @code{explicit-variables} set. See above.
32572 The registers that have been collected at the current trace frame.
32573 For each register collected, the name and current value are returned.
32574 The value is formatted according to the @code{--registers-format}
32575 option. See the @command{-data-list-register-values} command for a
32576 list of the allowed formats. The default is @samp{x}.
32579 The trace state variables that have been collected at the current
32580 trace frame. For each trace state variable collected, the name and
32581 current value are returned.
32584 The set of memory ranges that have been collected at the current trace
32585 frame. Its content is a list of tuples. Each tuple represents a
32586 collected memory range and has the following fields:
32590 The start address of the memory range, as hexadecimal literal.
32593 The length of the memory range, as decimal literal.
32596 The contents of the memory block, in hex. This field is only present
32597 if the @code{--memory-contents} option is specified.
32603 @subsubheading @value{GDBN} Command
32605 There is no corresponding @value{GDBN} command.
32607 @subsubheading Example
32609 @subheading -trace-list-variables
32610 @findex -trace-list-variables
32612 @subsubheading Synopsis
32615 -trace-list-variables
32618 Return a table of all defined trace variables. Each element of the
32619 table has the following fields:
32623 The name of the trace variable. This field is always present.
32626 The initial value. This is a 64-bit signed integer. This
32627 field is always present.
32630 The value the trace variable has at the moment. This is a 64-bit
32631 signed integer. This field is absent iff current value is
32632 not defined, for example if the trace was never run, or is
32637 @subsubheading @value{GDBN} Command
32639 The corresponding @value{GDBN} command is @samp{tvariables}.
32641 @subsubheading Example
32645 -trace-list-variables
32646 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32647 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32648 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32649 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32650 body=[variable=@{name="$trace_timestamp",initial="0"@}
32651 variable=@{name="$foo",initial="10",current="15"@}]@}
32655 @subheading -trace-save
32656 @findex -trace-save
32658 @subsubheading Synopsis
32661 -trace-save [ -r ] [ -ctf ] @var{filename}
32664 Saves the collected trace data to @var{filename}. Without the
32665 @samp{-r} option, the data is downloaded from the target and saved
32666 in a local file. With the @samp{-r} option the target is asked
32667 to perform the save.
32669 By default, this command will save the trace in the tfile format. You can
32670 supply the optional @samp{-ctf} argument to save it the CTF format. See
32671 @ref{Trace Files} for more information about CTF.
32673 @subsubheading @value{GDBN} Command
32675 The corresponding @value{GDBN} command is @samp{tsave}.
32678 @subheading -trace-start
32679 @findex -trace-start
32681 @subsubheading Synopsis
32687 Starts a tracing experiment. The result of this command does not
32690 @subsubheading @value{GDBN} Command
32692 The corresponding @value{GDBN} command is @samp{tstart}.
32694 @subheading -trace-status
32695 @findex -trace-status
32697 @subsubheading Synopsis
32703 Obtains the status of a tracing experiment. The result may include
32704 the following fields:
32709 May have a value of either @samp{0}, when no tracing operations are
32710 supported, @samp{1}, when all tracing operations are supported, or
32711 @samp{file} when examining trace file. In the latter case, examining
32712 of trace frame is possible but new tracing experiement cannot be
32713 started. This field is always present.
32716 May have a value of either @samp{0} or @samp{1} depending on whether
32717 tracing experiement is in progress on target. This field is present
32718 if @samp{supported} field is not @samp{0}.
32721 Report the reason why the tracing was stopped last time. This field
32722 may be absent iff tracing was never stopped on target yet. The
32723 value of @samp{request} means the tracing was stopped as result of
32724 the @code{-trace-stop} command. The value of @samp{overflow} means
32725 the tracing buffer is full. The value of @samp{disconnection} means
32726 tracing was automatically stopped when @value{GDBN} has disconnected.
32727 The value of @samp{passcount} means tracing was stopped when a
32728 tracepoint was passed a maximal number of times for that tracepoint.
32729 This field is present if @samp{supported} field is not @samp{0}.
32731 @item stopping-tracepoint
32732 The number of tracepoint whose passcount as exceeded. This field is
32733 present iff the @samp{stop-reason} field has the value of
32737 @itemx frames-created
32738 The @samp{frames} field is a count of the total number of trace frames
32739 in the trace buffer, while @samp{frames-created} is the total created
32740 during the run, including ones that were discarded, such as when a
32741 circular trace buffer filled up. Both fields are optional.
32745 These fields tell the current size of the tracing buffer and the
32746 remaining space. These fields are optional.
32749 The value of the circular trace buffer flag. @code{1} means that the
32750 trace buffer is circular and old trace frames will be discarded if
32751 necessary to make room, @code{0} means that the trace buffer is linear
32755 The value of the disconnected tracing flag. @code{1} means that
32756 tracing will continue after @value{GDBN} disconnects, @code{0} means
32757 that the trace run will stop.
32760 The filename of the trace file being examined. This field is
32761 optional, and only present when examining a trace file.
32765 @subsubheading @value{GDBN} Command
32767 The corresponding @value{GDBN} command is @samp{tstatus}.
32769 @subheading -trace-stop
32770 @findex -trace-stop
32772 @subsubheading Synopsis
32778 Stops a tracing experiment. The result of this command has the same
32779 fields as @code{-trace-status}, except that the @samp{supported} and
32780 @samp{running} fields are not output.
32782 @subsubheading @value{GDBN} Command
32784 The corresponding @value{GDBN} command is @samp{tstop}.
32787 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32788 @node GDB/MI Symbol Query
32789 @section @sc{gdb/mi} Symbol Query Commands
32793 @subheading The @code{-symbol-info-address} Command
32794 @findex -symbol-info-address
32796 @subsubheading Synopsis
32799 -symbol-info-address @var{symbol}
32802 Describe where @var{symbol} is stored.
32804 @subsubheading @value{GDBN} Command
32806 The corresponding @value{GDBN} command is @samp{info address}.
32808 @subsubheading Example
32812 @subheading The @code{-symbol-info-file} Command
32813 @findex -symbol-info-file
32815 @subsubheading Synopsis
32821 Show the file for the symbol.
32823 @subsubheading @value{GDBN} Command
32825 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32826 @samp{gdb_find_file}.
32828 @subsubheading Example
32832 @subheading The @code{-symbol-info-function} Command
32833 @findex -symbol-info-function
32835 @subsubheading Synopsis
32838 -symbol-info-function
32841 Show which function the symbol lives in.
32843 @subsubheading @value{GDBN} Command
32845 @samp{gdb_get_function} in @code{gdbtk}.
32847 @subsubheading Example
32851 @subheading The @code{-symbol-info-line} Command
32852 @findex -symbol-info-line
32854 @subsubheading Synopsis
32860 Show the core addresses of the code for a source line.
32862 @subsubheading @value{GDBN} Command
32864 The corresponding @value{GDBN} command is @samp{info line}.
32865 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32867 @subsubheading Example
32871 @subheading The @code{-symbol-info-symbol} Command
32872 @findex -symbol-info-symbol
32874 @subsubheading Synopsis
32877 -symbol-info-symbol @var{addr}
32880 Describe what symbol is at location @var{addr}.
32882 @subsubheading @value{GDBN} Command
32884 The corresponding @value{GDBN} command is @samp{info symbol}.
32886 @subsubheading Example
32890 @subheading The @code{-symbol-list-functions} Command
32891 @findex -symbol-list-functions
32893 @subsubheading Synopsis
32896 -symbol-list-functions
32899 List the functions in the executable.
32901 @subsubheading @value{GDBN} Command
32903 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32904 @samp{gdb_search} in @code{gdbtk}.
32906 @subsubheading Example
32911 @subheading The @code{-symbol-list-lines} Command
32912 @findex -symbol-list-lines
32914 @subsubheading Synopsis
32917 -symbol-list-lines @var{filename}
32920 Print the list of lines that contain code and their associated program
32921 addresses for the given source filename. The entries are sorted in
32922 ascending PC order.
32924 @subsubheading @value{GDBN} Command
32926 There is no corresponding @value{GDBN} command.
32928 @subsubheading Example
32931 -symbol-list-lines basics.c
32932 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32938 @subheading The @code{-symbol-list-types} Command
32939 @findex -symbol-list-types
32941 @subsubheading Synopsis
32947 List all the type names.
32949 @subsubheading @value{GDBN} Command
32951 The corresponding commands are @samp{info types} in @value{GDBN},
32952 @samp{gdb_search} in @code{gdbtk}.
32954 @subsubheading Example
32958 @subheading The @code{-symbol-list-variables} Command
32959 @findex -symbol-list-variables
32961 @subsubheading Synopsis
32964 -symbol-list-variables
32967 List all the global and static variable names.
32969 @subsubheading @value{GDBN} Command
32971 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32973 @subsubheading Example
32977 @subheading The @code{-symbol-locate} Command
32978 @findex -symbol-locate
32980 @subsubheading Synopsis
32986 @subsubheading @value{GDBN} Command
32988 @samp{gdb_loc} in @code{gdbtk}.
32990 @subsubheading Example
32994 @subheading The @code{-symbol-type} Command
32995 @findex -symbol-type
32997 @subsubheading Synopsis
33000 -symbol-type @var{variable}
33003 Show type of @var{variable}.
33005 @subsubheading @value{GDBN} Command
33007 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33008 @samp{gdb_obj_variable}.
33010 @subsubheading Example
33015 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33016 @node GDB/MI File Commands
33017 @section @sc{gdb/mi} File Commands
33019 This section describes the GDB/MI commands to specify executable file names
33020 and to read in and obtain symbol table information.
33022 @subheading The @code{-file-exec-and-symbols} Command
33023 @findex -file-exec-and-symbols
33025 @subsubheading Synopsis
33028 -file-exec-and-symbols @var{file}
33031 Specify the executable file to be debugged. This file is the one from
33032 which the symbol table is also read. If no file is specified, the
33033 command clears the executable and symbol information. If breakpoints
33034 are set when using this command with no arguments, @value{GDBN} will produce
33035 error messages. Otherwise, no output is produced, except a completion
33038 @subsubheading @value{GDBN} Command
33040 The corresponding @value{GDBN} command is @samp{file}.
33042 @subsubheading Example
33046 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33052 @subheading The @code{-file-exec-file} Command
33053 @findex -file-exec-file
33055 @subsubheading Synopsis
33058 -file-exec-file @var{file}
33061 Specify the executable file to be debugged. Unlike
33062 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33063 from this file. If used without argument, @value{GDBN} clears the information
33064 about the executable file. No output is produced, except a completion
33067 @subsubheading @value{GDBN} Command
33069 The corresponding @value{GDBN} command is @samp{exec-file}.
33071 @subsubheading Example
33075 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33082 @subheading The @code{-file-list-exec-sections} Command
33083 @findex -file-list-exec-sections
33085 @subsubheading Synopsis
33088 -file-list-exec-sections
33091 List the sections of the current executable file.
33093 @subsubheading @value{GDBN} Command
33095 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33096 information as this command. @code{gdbtk} has a corresponding command
33097 @samp{gdb_load_info}.
33099 @subsubheading Example
33104 @subheading The @code{-file-list-exec-source-file} Command
33105 @findex -file-list-exec-source-file
33107 @subsubheading Synopsis
33110 -file-list-exec-source-file
33113 List the line number, the current source file, and the absolute path
33114 to the current source file for the current executable. The macro
33115 information field has a value of @samp{1} or @samp{0} depending on
33116 whether or not the file includes preprocessor macro information.
33118 @subsubheading @value{GDBN} Command
33120 The @value{GDBN} equivalent is @samp{info source}
33122 @subsubheading Example
33126 123-file-list-exec-source-file
33127 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33132 @subheading The @code{-file-list-exec-source-files} Command
33133 @findex -file-list-exec-source-files
33135 @subsubheading Synopsis
33138 -file-list-exec-source-files
33141 List the source files for the current executable.
33143 It will always output both the filename and fullname (absolute file
33144 name) of a source file.
33146 @subsubheading @value{GDBN} Command
33148 The @value{GDBN} equivalent is @samp{info sources}.
33149 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33151 @subsubheading Example
33154 -file-list-exec-source-files
33156 @{file=foo.c,fullname=/home/foo.c@},
33157 @{file=/home/bar.c,fullname=/home/bar.c@},
33158 @{file=gdb_could_not_find_fullpath.c@}]
33162 @subheading The @code{-file-list-shared-libraries} Command
33163 @findex -file-list-shared-libraries
33165 @subsubheading Synopsis
33168 -file-list-shared-libraries [ @var{regexp} ]
33171 List the shared libraries in the program.
33172 With a regular expression @var{regexp}, only those libraries whose
33173 names match @var{regexp} are listed.
33175 @subsubheading @value{GDBN} Command
33177 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33178 have a similar meaning to the @code{=library-loaded} notification.
33179 The @code{ranges} field specifies the multiple segments belonging to this
33180 library. Each range has the following fields:
33184 The address defining the inclusive lower bound of the segment.
33186 The address defining the exclusive upper bound of the segment.
33189 @subsubheading Example
33192 -file-list-exec-source-files
33193 ^done,shared-libraries=[
33194 @{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"@}]@},
33195 @{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"@}]@}]
33201 @subheading The @code{-file-list-symbol-files} Command
33202 @findex -file-list-symbol-files
33204 @subsubheading Synopsis
33207 -file-list-symbol-files
33212 @subsubheading @value{GDBN} Command
33214 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33216 @subsubheading Example
33221 @subheading The @code{-file-symbol-file} Command
33222 @findex -file-symbol-file
33224 @subsubheading Synopsis
33227 -file-symbol-file @var{file}
33230 Read symbol table info from the specified @var{file} argument. When
33231 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33232 produced, except for a completion notification.
33234 @subsubheading @value{GDBN} Command
33236 The corresponding @value{GDBN} command is @samp{symbol-file}.
33238 @subsubheading Example
33242 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33248 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33249 @node GDB/MI Memory Overlay Commands
33250 @section @sc{gdb/mi} Memory Overlay Commands
33252 The memory overlay commands are not implemented.
33254 @c @subheading -overlay-auto
33256 @c @subheading -overlay-list-mapping-state
33258 @c @subheading -overlay-list-overlays
33260 @c @subheading -overlay-map
33262 @c @subheading -overlay-off
33264 @c @subheading -overlay-on
33266 @c @subheading -overlay-unmap
33268 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33269 @node GDB/MI Signal Handling Commands
33270 @section @sc{gdb/mi} Signal Handling Commands
33272 Signal handling commands are not implemented.
33274 @c @subheading -signal-handle
33276 @c @subheading -signal-list-handle-actions
33278 @c @subheading -signal-list-signal-types
33282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33283 @node GDB/MI Target Manipulation
33284 @section @sc{gdb/mi} Target Manipulation Commands
33287 @subheading The @code{-target-attach} Command
33288 @findex -target-attach
33290 @subsubheading Synopsis
33293 -target-attach @var{pid} | @var{gid} | @var{file}
33296 Attach to a process @var{pid} or a file @var{file} outside of
33297 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33298 group, the id previously returned by
33299 @samp{-list-thread-groups --available} must be used.
33301 @subsubheading @value{GDBN} Command
33303 The corresponding @value{GDBN} command is @samp{attach}.
33305 @subsubheading Example
33309 =thread-created,id="1"
33310 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33316 @subheading The @code{-target-compare-sections} Command
33317 @findex -target-compare-sections
33319 @subsubheading Synopsis
33322 -target-compare-sections [ @var{section} ]
33325 Compare data of section @var{section} on target to the exec file.
33326 Without the argument, all sections are compared.
33328 @subsubheading @value{GDBN} Command
33330 The @value{GDBN} equivalent is @samp{compare-sections}.
33332 @subsubheading Example
33337 @subheading The @code{-target-detach} Command
33338 @findex -target-detach
33340 @subsubheading Synopsis
33343 -target-detach [ @var{pid} | @var{gid} ]
33346 Detach from the remote target which normally resumes its execution.
33347 If either @var{pid} or @var{gid} is specified, detaches from either
33348 the specified process, or specified thread group. There's no output.
33350 @subsubheading @value{GDBN} Command
33352 The corresponding @value{GDBN} command is @samp{detach}.
33354 @subsubheading Example
33364 @subheading The @code{-target-disconnect} Command
33365 @findex -target-disconnect
33367 @subsubheading Synopsis
33373 Disconnect from the remote target. There's no output and the target is
33374 generally not resumed.
33376 @subsubheading @value{GDBN} Command
33378 The corresponding @value{GDBN} command is @samp{disconnect}.
33380 @subsubheading Example
33390 @subheading The @code{-target-download} Command
33391 @findex -target-download
33393 @subsubheading Synopsis
33399 Loads the executable onto the remote target.
33400 It prints out an update message every half second, which includes the fields:
33404 The name of the section.
33406 The size of what has been sent so far for that section.
33408 The size of the section.
33410 The total size of what was sent so far (the current and the previous sections).
33412 The size of the overall executable to download.
33416 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33417 @sc{gdb/mi} Output Syntax}).
33419 In addition, it prints the name and size of the sections, as they are
33420 downloaded. These messages include the following fields:
33424 The name of the section.
33426 The size of the section.
33428 The size of the overall executable to download.
33432 At the end, a summary is printed.
33434 @subsubheading @value{GDBN} Command
33436 The corresponding @value{GDBN} command is @samp{load}.
33438 @subsubheading Example
33440 Note: each status message appears on a single line. Here the messages
33441 have been broken down so that they can fit onto a page.
33446 +download,@{section=".text",section-size="6668",total-size="9880"@}
33447 +download,@{section=".text",section-sent="512",section-size="6668",
33448 total-sent="512",total-size="9880"@}
33449 +download,@{section=".text",section-sent="1024",section-size="6668",
33450 total-sent="1024",total-size="9880"@}
33451 +download,@{section=".text",section-sent="1536",section-size="6668",
33452 total-sent="1536",total-size="9880"@}
33453 +download,@{section=".text",section-sent="2048",section-size="6668",
33454 total-sent="2048",total-size="9880"@}
33455 +download,@{section=".text",section-sent="2560",section-size="6668",
33456 total-sent="2560",total-size="9880"@}
33457 +download,@{section=".text",section-sent="3072",section-size="6668",
33458 total-sent="3072",total-size="9880"@}
33459 +download,@{section=".text",section-sent="3584",section-size="6668",
33460 total-sent="3584",total-size="9880"@}
33461 +download,@{section=".text",section-sent="4096",section-size="6668",
33462 total-sent="4096",total-size="9880"@}
33463 +download,@{section=".text",section-sent="4608",section-size="6668",
33464 total-sent="4608",total-size="9880"@}
33465 +download,@{section=".text",section-sent="5120",section-size="6668",
33466 total-sent="5120",total-size="9880"@}
33467 +download,@{section=".text",section-sent="5632",section-size="6668",
33468 total-sent="5632",total-size="9880"@}
33469 +download,@{section=".text",section-sent="6144",section-size="6668",
33470 total-sent="6144",total-size="9880"@}
33471 +download,@{section=".text",section-sent="6656",section-size="6668",
33472 total-sent="6656",total-size="9880"@}
33473 +download,@{section=".init",section-size="28",total-size="9880"@}
33474 +download,@{section=".fini",section-size="28",total-size="9880"@}
33475 +download,@{section=".data",section-size="3156",total-size="9880"@}
33476 +download,@{section=".data",section-sent="512",section-size="3156",
33477 total-sent="7236",total-size="9880"@}
33478 +download,@{section=".data",section-sent="1024",section-size="3156",
33479 total-sent="7748",total-size="9880"@}
33480 +download,@{section=".data",section-sent="1536",section-size="3156",
33481 total-sent="8260",total-size="9880"@}
33482 +download,@{section=".data",section-sent="2048",section-size="3156",
33483 total-sent="8772",total-size="9880"@}
33484 +download,@{section=".data",section-sent="2560",section-size="3156",
33485 total-sent="9284",total-size="9880"@}
33486 +download,@{section=".data",section-sent="3072",section-size="3156",
33487 total-sent="9796",total-size="9880"@}
33488 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33495 @subheading The @code{-target-exec-status} Command
33496 @findex -target-exec-status
33498 @subsubheading Synopsis
33501 -target-exec-status
33504 Provide information on the state of the target (whether it is running or
33505 not, for instance).
33507 @subsubheading @value{GDBN} Command
33509 There's no equivalent @value{GDBN} command.
33511 @subsubheading Example
33515 @subheading The @code{-target-list-available-targets} Command
33516 @findex -target-list-available-targets
33518 @subsubheading Synopsis
33521 -target-list-available-targets
33524 List the possible targets to connect to.
33526 @subsubheading @value{GDBN} Command
33528 The corresponding @value{GDBN} command is @samp{help target}.
33530 @subsubheading Example
33534 @subheading The @code{-target-list-current-targets} Command
33535 @findex -target-list-current-targets
33537 @subsubheading Synopsis
33540 -target-list-current-targets
33543 Describe the current target.
33545 @subsubheading @value{GDBN} Command
33547 The corresponding information is printed by @samp{info file} (among
33550 @subsubheading Example
33554 @subheading The @code{-target-list-parameters} Command
33555 @findex -target-list-parameters
33557 @subsubheading Synopsis
33560 -target-list-parameters
33566 @subsubheading @value{GDBN} Command
33570 @subsubheading Example
33573 @subheading The @code{-target-flash-erase} Command
33574 @findex -target-flash-erase
33576 @subsubheading Synopsis
33579 -target-flash-erase
33582 Erases all known flash memory regions on the target.
33584 The corresponding @value{GDBN} command is @samp{flash-erase}.
33586 The output is a list of flash regions that have been erased, with starting
33587 addresses and memory region sizes.
33591 -target-flash-erase
33592 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33596 @subheading The @code{-target-select} Command
33597 @findex -target-select
33599 @subsubheading Synopsis
33602 -target-select @var{type} @var{parameters @dots{}}
33605 Connect @value{GDBN} to the remote target. This command takes two args:
33609 The type of target, for instance @samp{remote}, etc.
33610 @item @var{parameters}
33611 Device names, host names and the like. @xref{Target Commands, ,
33612 Commands for Managing Targets}, for more details.
33615 The output is a connection notification, followed by the address at
33616 which the target program is, in the following form:
33619 ^connected,addr="@var{address}",func="@var{function name}",
33620 args=[@var{arg list}]
33623 @subsubheading @value{GDBN} Command
33625 The corresponding @value{GDBN} command is @samp{target}.
33627 @subsubheading Example
33631 -target-select remote /dev/ttya
33632 ^connected,addr="0xfe00a300",func="??",args=[]
33636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33637 @node GDB/MI File Transfer Commands
33638 @section @sc{gdb/mi} File Transfer Commands
33641 @subheading The @code{-target-file-put} Command
33642 @findex -target-file-put
33644 @subsubheading Synopsis
33647 -target-file-put @var{hostfile} @var{targetfile}
33650 Copy file @var{hostfile} from the host system (the machine running
33651 @value{GDBN}) to @var{targetfile} on the target system.
33653 @subsubheading @value{GDBN} Command
33655 The corresponding @value{GDBN} command is @samp{remote put}.
33657 @subsubheading Example
33661 -target-file-put localfile remotefile
33667 @subheading The @code{-target-file-get} Command
33668 @findex -target-file-get
33670 @subsubheading Synopsis
33673 -target-file-get @var{targetfile} @var{hostfile}
33676 Copy file @var{targetfile} from the target system to @var{hostfile}
33677 on the host system.
33679 @subsubheading @value{GDBN} Command
33681 The corresponding @value{GDBN} command is @samp{remote get}.
33683 @subsubheading Example
33687 -target-file-get remotefile localfile
33693 @subheading The @code{-target-file-delete} Command
33694 @findex -target-file-delete
33696 @subsubheading Synopsis
33699 -target-file-delete @var{targetfile}
33702 Delete @var{targetfile} from the target system.
33704 @subsubheading @value{GDBN} Command
33706 The corresponding @value{GDBN} command is @samp{remote delete}.
33708 @subsubheading Example
33712 -target-file-delete remotefile
33718 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33719 @node GDB/MI Ada Exceptions Commands
33720 @section Ada Exceptions @sc{gdb/mi} Commands
33722 @subheading The @code{-info-ada-exceptions} Command
33723 @findex -info-ada-exceptions
33725 @subsubheading Synopsis
33728 -info-ada-exceptions [ @var{regexp}]
33731 List all Ada exceptions defined within the program being debugged.
33732 With a regular expression @var{regexp}, only those exceptions whose
33733 names match @var{regexp} are listed.
33735 @subsubheading @value{GDBN} Command
33737 The corresponding @value{GDBN} command is @samp{info exceptions}.
33739 @subsubheading Result
33741 The result is a table of Ada exceptions. The following columns are
33742 defined for each exception:
33746 The name of the exception.
33749 The address of the exception.
33753 @subsubheading Example
33756 -info-ada-exceptions aint
33757 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33758 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33759 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33760 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33761 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33764 @subheading Catching Ada Exceptions
33766 The commands describing how to ask @value{GDBN} to stop when a program
33767 raises an exception are described at @ref{Ada Exception GDB/MI
33768 Catchpoint Commands}.
33771 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33772 @node GDB/MI Support Commands
33773 @section @sc{gdb/mi} Support Commands
33775 Since new commands and features get regularly added to @sc{gdb/mi},
33776 some commands are available to help front-ends query the debugger
33777 about support for these capabilities. Similarly, it is also possible
33778 to query @value{GDBN} about target support of certain features.
33780 @subheading The @code{-info-gdb-mi-command} Command
33781 @cindex @code{-info-gdb-mi-command}
33782 @findex -info-gdb-mi-command
33784 @subsubheading Synopsis
33787 -info-gdb-mi-command @var{cmd_name}
33790 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33792 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33793 is technically not part of the command name (@pxref{GDB/MI Input
33794 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33795 for ease of use, this command also accepts the form with the leading
33798 @subsubheading @value{GDBN} Command
33800 There is no corresponding @value{GDBN} command.
33802 @subsubheading Result
33804 The result is a tuple. There is currently only one field:
33808 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33809 @code{"false"} otherwise.
33813 @subsubheading Example
33815 Here is an example where the @sc{gdb/mi} command does not exist:
33818 -info-gdb-mi-command unsupported-command
33819 ^done,command=@{exists="false"@}
33823 And here is an example where the @sc{gdb/mi} command is known
33827 -info-gdb-mi-command symbol-list-lines
33828 ^done,command=@{exists="true"@}
33831 @subheading The @code{-list-features} Command
33832 @findex -list-features
33833 @cindex supported @sc{gdb/mi} features, list
33835 Returns a list of particular features of the MI protocol that
33836 this version of gdb implements. A feature can be a command,
33837 or a new field in an output of some command, or even an
33838 important bugfix. While a frontend can sometimes detect presence
33839 of a feature at runtime, it is easier to perform detection at debugger
33842 The command returns a list of strings, with each string naming an
33843 available feature. Each returned string is just a name, it does not
33844 have any internal structure. The list of possible feature names
33850 (gdb) -list-features
33851 ^done,result=["feature1","feature2"]
33854 The current list of features is:
33857 @item frozen-varobjs
33858 Indicates support for the @code{-var-set-frozen} command, as well
33859 as possible presense of the @code{frozen} field in the output
33860 of @code{-varobj-create}.
33861 @item pending-breakpoints
33862 Indicates support for the @option{-f} option to the @code{-break-insert}
33865 Indicates Python scripting support, Python-based
33866 pretty-printing commands, and possible presence of the
33867 @samp{display_hint} field in the output of @code{-var-list-children}
33869 Indicates support for the @code{-thread-info} command.
33870 @item data-read-memory-bytes
33871 Indicates support for the @code{-data-read-memory-bytes} and the
33872 @code{-data-write-memory-bytes} commands.
33873 @item breakpoint-notifications
33874 Indicates that changes to breakpoints and breakpoints created via the
33875 CLI will be announced via async records.
33876 @item ada-task-info
33877 Indicates support for the @code{-ada-task-info} command.
33878 @item language-option
33879 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33880 option (@pxref{Context management}).
33881 @item info-gdb-mi-command
33882 Indicates support for the @code{-info-gdb-mi-command} command.
33883 @item undefined-command-error-code
33884 Indicates support for the "undefined-command" error code in error result
33885 records, produced when trying to execute an undefined @sc{gdb/mi} command
33886 (@pxref{GDB/MI Result Records}).
33887 @item exec-run-start-option
33888 Indicates that the @code{-exec-run} command supports the @option{--start}
33889 option (@pxref{GDB/MI Program Execution}).
33890 @item data-disassemble-a-option
33891 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33892 option (@pxref{GDB/MI Data Manipulation}).
33895 @subheading The @code{-list-target-features} Command
33896 @findex -list-target-features
33898 Returns a list of particular features that are supported by the
33899 target. Those features affect the permitted MI commands, but
33900 unlike the features reported by the @code{-list-features} command, the
33901 features depend on which target GDB is using at the moment. Whenever
33902 a target can change, due to commands such as @code{-target-select},
33903 @code{-target-attach} or @code{-exec-run}, the list of target features
33904 may change, and the frontend should obtain it again.
33908 (gdb) -list-target-features
33909 ^done,result=["async"]
33912 The current list of features is:
33916 Indicates that the target is capable of asynchronous command
33917 execution, which means that @value{GDBN} will accept further commands
33918 while the target is running.
33921 Indicates that the target is capable of reverse execution.
33922 @xref{Reverse Execution}, for more information.
33926 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33927 @node GDB/MI Miscellaneous Commands
33928 @section Miscellaneous @sc{gdb/mi} Commands
33930 @c @subheading -gdb-complete
33932 @subheading The @code{-gdb-exit} Command
33935 @subsubheading Synopsis
33941 Exit @value{GDBN} immediately.
33943 @subsubheading @value{GDBN} Command
33945 Approximately corresponds to @samp{quit}.
33947 @subsubheading Example
33957 @subheading The @code{-exec-abort} Command
33958 @findex -exec-abort
33960 @subsubheading Synopsis
33966 Kill the inferior running program.
33968 @subsubheading @value{GDBN} Command
33970 The corresponding @value{GDBN} command is @samp{kill}.
33972 @subsubheading Example
33977 @subheading The @code{-gdb-set} Command
33980 @subsubheading Synopsis
33986 Set an internal @value{GDBN} variable.
33987 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33989 @subsubheading @value{GDBN} Command
33991 The corresponding @value{GDBN} command is @samp{set}.
33993 @subsubheading Example
34003 @subheading The @code{-gdb-show} Command
34006 @subsubheading Synopsis
34012 Show the current value of a @value{GDBN} variable.
34014 @subsubheading @value{GDBN} Command
34016 The corresponding @value{GDBN} command is @samp{show}.
34018 @subsubheading Example
34027 @c @subheading -gdb-source
34030 @subheading The @code{-gdb-version} Command
34031 @findex -gdb-version
34033 @subsubheading Synopsis
34039 Show version information for @value{GDBN}. Used mostly in testing.
34041 @subsubheading @value{GDBN} Command
34043 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34044 default shows this information when you start an interactive session.
34046 @subsubheading Example
34048 @c This example modifies the actual output from GDB to avoid overfull
34054 ~Copyright 2000 Free Software Foundation, Inc.
34055 ~GDB is free software, covered by the GNU General Public License, and
34056 ~you are welcome to change it and/or distribute copies of it under
34057 ~ certain conditions.
34058 ~Type "show copying" to see the conditions.
34059 ~There is absolutely no warranty for GDB. Type "show warranty" for
34061 ~This GDB was configured as
34062 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34067 @subheading The @code{-list-thread-groups} Command
34068 @findex -list-thread-groups
34070 @subheading Synopsis
34073 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34076 Lists thread groups (@pxref{Thread groups}). When a single thread
34077 group is passed as the argument, lists the children of that group.
34078 When several thread group are passed, lists information about those
34079 thread groups. Without any parameters, lists information about all
34080 top-level thread groups.
34082 Normally, thread groups that are being debugged are reported.
34083 With the @samp{--available} option, @value{GDBN} reports thread groups
34084 available on the target.
34086 The output of this command may have either a @samp{threads} result or
34087 a @samp{groups} result. The @samp{thread} result has a list of tuples
34088 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34089 Information}). The @samp{groups} result has a list of tuples as value,
34090 each tuple describing a thread group. If top-level groups are
34091 requested (that is, no parameter is passed), or when several groups
34092 are passed, the output always has a @samp{groups} result. The format
34093 of the @samp{group} result is described below.
34095 To reduce the number of roundtrips it's possible to list thread groups
34096 together with their children, by passing the @samp{--recurse} option
34097 and the recursion depth. Presently, only recursion depth of 1 is
34098 permitted. If this option is present, then every reported thread group
34099 will also include its children, either as @samp{group} or
34100 @samp{threads} field.
34102 In general, any combination of option and parameters is permitted, with
34103 the following caveats:
34107 When a single thread group is passed, the output will typically
34108 be the @samp{threads} result. Because threads may not contain
34109 anything, the @samp{recurse} option will be ignored.
34112 When the @samp{--available} option is passed, limited information may
34113 be available. In particular, the list of threads of a process might
34114 be inaccessible. Further, specifying specific thread groups might
34115 not give any performance advantage over listing all thread groups.
34116 The frontend should assume that @samp{-list-thread-groups --available}
34117 is always an expensive operation and cache the results.
34121 The @samp{groups} result is a list of tuples, where each tuple may
34122 have the following fields:
34126 Identifier of the thread group. This field is always present.
34127 The identifier is an opaque string; frontends should not try to
34128 convert it to an integer, even though it might look like one.
34131 The type of the thread group. At present, only @samp{process} is a
34135 The target-specific process identifier. This field is only present
34136 for thread groups of type @samp{process} and only if the process exists.
34139 The exit code of this group's last exited thread, formatted in octal.
34140 This field is only present for thread groups of type @samp{process} and
34141 only if the process is not running.
34144 The number of children this thread group has. This field may be
34145 absent for an available thread group.
34148 This field has a list of tuples as value, each tuple describing a
34149 thread. It may be present if the @samp{--recurse} option is
34150 specified, and it's actually possible to obtain the threads.
34153 This field is a list of integers, each identifying a core that one
34154 thread of the group is running on. This field may be absent if
34155 such information is not available.
34158 The name of the executable file that corresponds to this thread group.
34159 The field is only present for thread groups of type @samp{process},
34160 and only if there is a corresponding executable file.
34164 @subheading Example
34168 -list-thread-groups
34169 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34170 -list-thread-groups 17
34171 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34172 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34173 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34174 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34175 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34176 -list-thread-groups --available
34177 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34178 -list-thread-groups --available --recurse 1
34179 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34180 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34181 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34182 -list-thread-groups --available --recurse 1 17 18
34183 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34184 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34185 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34188 @subheading The @code{-info-os} Command
34191 @subsubheading Synopsis
34194 -info-os [ @var{type} ]
34197 If no argument is supplied, the command returns a table of available
34198 operating-system-specific information types. If one of these types is
34199 supplied as an argument @var{type}, then the command returns a table
34200 of data of that type.
34202 The types of information available depend on the target operating
34205 @subsubheading @value{GDBN} Command
34207 The corresponding @value{GDBN} command is @samp{info os}.
34209 @subsubheading Example
34211 When run on a @sc{gnu}/Linux system, the output will look something
34217 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34218 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34219 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34220 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34221 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34223 item=@{col0="files",col1="Listing of all file descriptors",
34224 col2="File descriptors"@},
34225 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34226 col2="Kernel modules"@},
34227 item=@{col0="msg",col1="Listing of all message queues",
34228 col2="Message queues"@},
34229 item=@{col0="processes",col1="Listing of all processes",
34230 col2="Processes"@},
34231 item=@{col0="procgroups",col1="Listing of all process groups",
34232 col2="Process groups"@},
34233 item=@{col0="semaphores",col1="Listing of all semaphores",
34234 col2="Semaphores"@},
34235 item=@{col0="shm",col1="Listing of all shared-memory regions",
34236 col2="Shared-memory regions"@},
34237 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34239 item=@{col0="threads",col1="Listing of all threads",
34243 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34244 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34245 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34246 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34247 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34248 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34249 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34250 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34252 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34253 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34257 (Note that the MI output here includes a @code{"Title"} column that
34258 does not appear in command-line @code{info os}; this column is useful
34259 for MI clients that want to enumerate the types of data, such as in a
34260 popup menu, but is needless clutter on the command line, and
34261 @code{info os} omits it.)
34263 @subheading The @code{-add-inferior} Command
34264 @findex -add-inferior
34266 @subheading Synopsis
34272 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34273 inferior is not associated with any executable. Such association may
34274 be established with the @samp{-file-exec-and-symbols} command
34275 (@pxref{GDB/MI File Commands}). The command response has a single
34276 field, @samp{inferior}, whose value is the identifier of the
34277 thread group corresponding to the new inferior.
34279 @subheading Example
34284 ^done,inferior="i3"
34287 @subheading The @code{-interpreter-exec} Command
34288 @findex -interpreter-exec
34290 @subheading Synopsis
34293 -interpreter-exec @var{interpreter} @var{command}
34295 @anchor{-interpreter-exec}
34297 Execute the specified @var{command} in the given @var{interpreter}.
34299 @subheading @value{GDBN} Command
34301 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34303 @subheading Example
34307 -interpreter-exec console "break main"
34308 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34309 &"During symbol reading, bad structure-type format.\n"
34310 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34315 @subheading The @code{-inferior-tty-set} Command
34316 @findex -inferior-tty-set
34318 @subheading Synopsis
34321 -inferior-tty-set /dev/pts/1
34324 Set terminal for future runs of the program being debugged.
34326 @subheading @value{GDBN} Command
34328 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34330 @subheading Example
34334 -inferior-tty-set /dev/pts/1
34339 @subheading The @code{-inferior-tty-show} Command
34340 @findex -inferior-tty-show
34342 @subheading Synopsis
34348 Show terminal for future runs of program being debugged.
34350 @subheading @value{GDBN} Command
34352 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34354 @subheading Example
34358 -inferior-tty-set /dev/pts/1
34362 ^done,inferior_tty_terminal="/dev/pts/1"
34366 @subheading The @code{-enable-timings} Command
34367 @findex -enable-timings
34369 @subheading Synopsis
34372 -enable-timings [yes | no]
34375 Toggle the printing of the wallclock, user and system times for an MI
34376 command as a field in its output. This command is to help frontend
34377 developers optimize the performance of their code. No argument is
34378 equivalent to @samp{yes}.
34380 @subheading @value{GDBN} Command
34384 @subheading Example
34392 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34393 addr="0x080484ed",func="main",file="myprog.c",
34394 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34396 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34404 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34405 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34406 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34407 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34412 @chapter @value{GDBN} Annotations
34414 This chapter describes annotations in @value{GDBN}. Annotations were
34415 designed to interface @value{GDBN} to graphical user interfaces or other
34416 similar programs which want to interact with @value{GDBN} at a
34417 relatively high level.
34419 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34423 This is Edition @value{EDITION}, @value{DATE}.
34427 * Annotations Overview:: What annotations are; the general syntax.
34428 * Server Prefix:: Issuing a command without affecting user state.
34429 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34430 * Errors:: Annotations for error messages.
34431 * Invalidation:: Some annotations describe things now invalid.
34432 * Annotations for Running::
34433 Whether the program is running, how it stopped, etc.
34434 * Source Annotations:: Annotations describing source code.
34437 @node Annotations Overview
34438 @section What is an Annotation?
34439 @cindex annotations
34441 Annotations start with a newline character, two @samp{control-z}
34442 characters, and the name of the annotation. If there is no additional
34443 information associated with this annotation, the name of the annotation
34444 is followed immediately by a newline. If there is additional
34445 information, the name of the annotation is followed by a space, the
34446 additional information, and a newline. The additional information
34447 cannot contain newline characters.
34449 Any output not beginning with a newline and two @samp{control-z}
34450 characters denotes literal output from @value{GDBN}. Currently there is
34451 no need for @value{GDBN} to output a newline followed by two
34452 @samp{control-z} characters, but if there was such a need, the
34453 annotations could be extended with an @samp{escape} annotation which
34454 means those three characters as output.
34456 The annotation @var{level}, which is specified using the
34457 @option{--annotate} command line option (@pxref{Mode Options}), controls
34458 how much information @value{GDBN} prints together with its prompt,
34459 values of expressions, source lines, and other types of output. Level 0
34460 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34461 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34462 for programs that control @value{GDBN}, and level 2 annotations have
34463 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34464 Interface, annotate, GDB's Obsolete Annotations}).
34467 @kindex set annotate
34468 @item set annotate @var{level}
34469 The @value{GDBN} command @code{set annotate} sets the level of
34470 annotations to the specified @var{level}.
34472 @item show annotate
34473 @kindex show annotate
34474 Show the current annotation level.
34477 This chapter describes level 3 annotations.
34479 A simple example of starting up @value{GDBN} with annotations is:
34482 $ @kbd{gdb --annotate=3}
34484 Copyright 2003 Free Software Foundation, Inc.
34485 GDB is free software, covered by the GNU General Public License,
34486 and you are welcome to change it and/or distribute copies of it
34487 under certain conditions.
34488 Type "show copying" to see the conditions.
34489 There is absolutely no warranty for GDB. Type "show warranty"
34491 This GDB was configured as "i386-pc-linux-gnu"
34502 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34503 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34504 denotes a @samp{control-z} character) are annotations; the rest is
34505 output from @value{GDBN}.
34507 @node Server Prefix
34508 @section The Server Prefix
34509 @cindex server prefix
34511 If you prefix a command with @samp{server } then it will not affect
34512 the command history, nor will it affect @value{GDBN}'s notion of which
34513 command to repeat if @key{RET} is pressed on a line by itself. This
34514 means that commands can be run behind a user's back by a front-end in
34515 a transparent manner.
34517 The @code{server } prefix does not affect the recording of values into
34518 the value history; to print a value without recording it into the
34519 value history, use the @code{output} command instead of the
34520 @code{print} command.
34522 Using this prefix also disables confirmation requests
34523 (@pxref{confirmation requests}).
34526 @section Annotation for @value{GDBN} Input
34528 @cindex annotations for prompts
34529 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34530 to know when to send output, when the output from a given command is
34533 Different kinds of input each have a different @dfn{input type}. Each
34534 input type has three annotations: a @code{pre-} annotation, which
34535 denotes the beginning of any prompt which is being output, a plain
34536 annotation, which denotes the end of the prompt, and then a @code{post-}
34537 annotation which denotes the end of any echo which may (or may not) be
34538 associated with the input. For example, the @code{prompt} input type
34539 features the following annotations:
34547 The input types are
34550 @findex pre-prompt annotation
34551 @findex prompt annotation
34552 @findex post-prompt annotation
34554 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34556 @findex pre-commands annotation
34557 @findex commands annotation
34558 @findex post-commands annotation
34560 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34561 command. The annotations are repeated for each command which is input.
34563 @findex pre-overload-choice annotation
34564 @findex overload-choice annotation
34565 @findex post-overload-choice annotation
34566 @item overload-choice
34567 When @value{GDBN} wants the user to select between various overloaded functions.
34569 @findex pre-query annotation
34570 @findex query annotation
34571 @findex post-query annotation
34573 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34575 @findex pre-prompt-for-continue annotation
34576 @findex prompt-for-continue annotation
34577 @findex post-prompt-for-continue annotation
34578 @item prompt-for-continue
34579 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34580 expect this to work well; instead use @code{set height 0} to disable
34581 prompting. This is because the counting of lines is buggy in the
34582 presence of annotations.
34587 @cindex annotations for errors, warnings and interrupts
34589 @findex quit annotation
34594 This annotation occurs right before @value{GDBN} responds to an interrupt.
34596 @findex error annotation
34601 This annotation occurs right before @value{GDBN} responds to an error.
34603 Quit and error annotations indicate that any annotations which @value{GDBN} was
34604 in the middle of may end abruptly. For example, if a
34605 @code{value-history-begin} annotation is followed by a @code{error}, one
34606 cannot expect to receive the matching @code{value-history-end}. One
34607 cannot expect not to receive it either, however; an error annotation
34608 does not necessarily mean that @value{GDBN} is immediately returning all the way
34611 @findex error-begin annotation
34612 A quit or error annotation may be preceded by
34618 Any output between that and the quit or error annotation is the error
34621 Warning messages are not yet annotated.
34622 @c If we want to change that, need to fix warning(), type_error(),
34623 @c range_error(), and possibly other places.
34626 @section Invalidation Notices
34628 @cindex annotations for invalidation messages
34629 The following annotations say that certain pieces of state may have
34633 @findex frames-invalid annotation
34634 @item ^Z^Zframes-invalid
34636 The frames (for example, output from the @code{backtrace} command) may
34639 @findex breakpoints-invalid annotation
34640 @item ^Z^Zbreakpoints-invalid
34642 The breakpoints may have changed. For example, the user just added or
34643 deleted a breakpoint.
34646 @node Annotations for Running
34647 @section Running the Program
34648 @cindex annotations for running programs
34650 @findex starting annotation
34651 @findex stopping annotation
34652 When the program starts executing due to a @value{GDBN} command such as
34653 @code{step} or @code{continue},
34659 is output. When the program stops,
34665 is output. Before the @code{stopped} annotation, a variety of
34666 annotations describe how the program stopped.
34669 @findex exited annotation
34670 @item ^Z^Zexited @var{exit-status}
34671 The program exited, and @var{exit-status} is the exit status (zero for
34672 successful exit, otherwise nonzero).
34674 @findex signalled annotation
34675 @findex signal-name annotation
34676 @findex signal-name-end annotation
34677 @findex signal-string annotation
34678 @findex signal-string-end annotation
34679 @item ^Z^Zsignalled
34680 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34681 annotation continues:
34687 ^Z^Zsignal-name-end
34691 ^Z^Zsignal-string-end
34696 where @var{name} is the name of the signal, such as @code{SIGILL} or
34697 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34698 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34699 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34700 user's benefit and have no particular format.
34702 @findex signal annotation
34704 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34705 just saying that the program received the signal, not that it was
34706 terminated with it.
34708 @findex breakpoint annotation
34709 @item ^Z^Zbreakpoint @var{number}
34710 The program hit breakpoint number @var{number}.
34712 @findex watchpoint annotation
34713 @item ^Z^Zwatchpoint @var{number}
34714 The program hit watchpoint number @var{number}.
34717 @node Source Annotations
34718 @section Displaying Source
34719 @cindex annotations for source display
34721 @findex source annotation
34722 The following annotation is used instead of displaying source code:
34725 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34728 where @var{filename} is an absolute file name indicating which source
34729 file, @var{line} is the line number within that file (where 1 is the
34730 first line in the file), @var{character} is the character position
34731 within the file (where 0 is the first character in the file) (for most
34732 debug formats this will necessarily point to the beginning of a line),
34733 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34734 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34735 @var{addr} is the address in the target program associated with the
34736 source which is being displayed. The @var{addr} is in the form @samp{0x}
34737 followed by one or more lowercase hex digits (note that this does not
34738 depend on the language).
34740 @node JIT Interface
34741 @chapter JIT Compilation Interface
34742 @cindex just-in-time compilation
34743 @cindex JIT compilation interface
34745 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34746 interface. A JIT compiler is a program or library that generates native
34747 executable code at runtime and executes it, usually in order to achieve good
34748 performance while maintaining platform independence.
34750 Programs that use JIT compilation are normally difficult to debug because
34751 portions of their code are generated at runtime, instead of being loaded from
34752 object files, which is where @value{GDBN} normally finds the program's symbols
34753 and debug information. In order to debug programs that use JIT compilation,
34754 @value{GDBN} has an interface that allows the program to register in-memory
34755 symbol files with @value{GDBN} at runtime.
34757 If you are using @value{GDBN} to debug a program that uses this interface, then
34758 it should work transparently so long as you have not stripped the binary. If
34759 you are developing a JIT compiler, then the interface is documented in the rest
34760 of this chapter. At this time, the only known client of this interface is the
34763 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34764 JIT compiler communicates with @value{GDBN} by writing data into a global
34765 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34766 attaches, it reads a linked list of symbol files from the global variable to
34767 find existing code, and puts a breakpoint in the function so that it can find
34768 out about additional code.
34771 * Declarations:: Relevant C struct declarations
34772 * Registering Code:: Steps to register code
34773 * Unregistering Code:: Steps to unregister code
34774 * Custom Debug Info:: Emit debug information in a custom format
34778 @section JIT Declarations
34780 These are the relevant struct declarations that a C program should include to
34781 implement the interface:
34791 struct jit_code_entry
34793 struct jit_code_entry *next_entry;
34794 struct jit_code_entry *prev_entry;
34795 const char *symfile_addr;
34796 uint64_t symfile_size;
34799 struct jit_descriptor
34802 /* This type should be jit_actions_t, but we use uint32_t
34803 to be explicit about the bitwidth. */
34804 uint32_t action_flag;
34805 struct jit_code_entry *relevant_entry;
34806 struct jit_code_entry *first_entry;
34809 /* GDB puts a breakpoint in this function. */
34810 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34812 /* Make sure to specify the version statically, because the
34813 debugger may check the version before we can set it. */
34814 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34817 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34818 modifications to this global data properly, which can easily be done by putting
34819 a global mutex around modifications to these structures.
34821 @node Registering Code
34822 @section Registering Code
34824 To register code with @value{GDBN}, the JIT should follow this protocol:
34828 Generate an object file in memory with symbols and other desired debug
34829 information. The file must include the virtual addresses of the sections.
34832 Create a code entry for the file, which gives the start and size of the symbol
34836 Add it to the linked list in the JIT descriptor.
34839 Point the relevant_entry field of the descriptor at the entry.
34842 Set @code{action_flag} to @code{JIT_REGISTER} and call
34843 @code{__jit_debug_register_code}.
34846 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34847 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34848 new code. However, the linked list must still be maintained in order to allow
34849 @value{GDBN} to attach to a running process and still find the symbol files.
34851 @node Unregistering Code
34852 @section Unregistering Code
34854 If code is freed, then the JIT should use the following protocol:
34858 Remove the code entry corresponding to the code from the linked list.
34861 Point the @code{relevant_entry} field of the descriptor at the code entry.
34864 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34865 @code{__jit_debug_register_code}.
34868 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34869 and the JIT will leak the memory used for the associated symbol files.
34871 @node Custom Debug Info
34872 @section Custom Debug Info
34873 @cindex custom JIT debug info
34874 @cindex JIT debug info reader
34876 Generating debug information in platform-native file formats (like ELF
34877 or COFF) may be an overkill for JIT compilers; especially if all the
34878 debug info is used for is displaying a meaningful backtrace. The
34879 issue can be resolved by having the JIT writers decide on a debug info
34880 format and also provide a reader that parses the debug info generated
34881 by the JIT compiler. This section gives a brief overview on writing
34882 such a parser. More specific details can be found in the source file
34883 @file{gdb/jit-reader.in}, which is also installed as a header at
34884 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34886 The reader is implemented as a shared object (so this functionality is
34887 not available on platforms which don't allow loading shared objects at
34888 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34889 @code{jit-reader-unload} are provided, to be used to load and unload
34890 the readers from a preconfigured directory. Once loaded, the shared
34891 object is used the parse the debug information emitted by the JIT
34895 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34896 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34899 @node Using JIT Debug Info Readers
34900 @subsection Using JIT Debug Info Readers
34901 @kindex jit-reader-load
34902 @kindex jit-reader-unload
34904 Readers can be loaded and unloaded using the @code{jit-reader-load}
34905 and @code{jit-reader-unload} commands.
34908 @item jit-reader-load @var{reader}
34909 Load the JIT reader named @var{reader}, which is a shared
34910 object specified as either an absolute or a relative file name. In
34911 the latter case, @value{GDBN} will try to load the reader from a
34912 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34913 system (here @var{libdir} is the system library directory, often
34914 @file{/usr/local/lib}).
34916 Only one reader can be active at a time; trying to load a second
34917 reader when one is already loaded will result in @value{GDBN}
34918 reporting an error. A new JIT reader can be loaded by first unloading
34919 the current one using @code{jit-reader-unload} and then invoking
34920 @code{jit-reader-load}.
34922 @item jit-reader-unload
34923 Unload the currently loaded JIT reader.
34927 @node Writing JIT Debug Info Readers
34928 @subsection Writing JIT Debug Info Readers
34929 @cindex writing JIT debug info readers
34931 As mentioned, a reader is essentially a shared object conforming to a
34932 certain ABI. This ABI is described in @file{jit-reader.h}.
34934 @file{jit-reader.h} defines the structures, macros and functions
34935 required to write a reader. It is installed (along with
34936 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34937 the system include directory.
34939 Readers need to be released under a GPL compatible license. A reader
34940 can be declared as released under such a license by placing the macro
34941 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34943 The entry point for readers is the symbol @code{gdb_init_reader},
34944 which is expected to be a function with the prototype
34946 @findex gdb_init_reader
34948 extern struct gdb_reader_funcs *gdb_init_reader (void);
34951 @cindex @code{struct gdb_reader_funcs}
34953 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34954 functions. These functions are executed to read the debug info
34955 generated by the JIT compiler (@code{read}), to unwind stack frames
34956 (@code{unwind}) and to create canonical frame IDs
34957 (@code{get_Frame_id}). It also has a callback that is called when the
34958 reader is being unloaded (@code{destroy}). The struct looks like this
34961 struct gdb_reader_funcs
34963 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34964 int reader_version;
34966 /* For use by the reader. */
34969 gdb_read_debug_info *read;
34970 gdb_unwind_frame *unwind;
34971 gdb_get_frame_id *get_frame_id;
34972 gdb_destroy_reader *destroy;
34976 @cindex @code{struct gdb_symbol_callbacks}
34977 @cindex @code{struct gdb_unwind_callbacks}
34979 The callbacks are provided with another set of callbacks by
34980 @value{GDBN} to do their job. For @code{read}, these callbacks are
34981 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34982 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34983 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34984 files and new symbol tables inside those object files. @code{struct
34985 gdb_unwind_callbacks} has callbacks to read registers off the current
34986 frame and to write out the values of the registers in the previous
34987 frame. Both have a callback (@code{target_read}) to read bytes off the
34988 target's address space.
34990 @node In-Process Agent
34991 @chapter In-Process Agent
34992 @cindex debugging agent
34993 The traditional debugging model is conceptually low-speed, but works fine,
34994 because most bugs can be reproduced in debugging-mode execution. However,
34995 as multi-core or many-core processors are becoming mainstream, and
34996 multi-threaded programs become more and more popular, there should be more
34997 and more bugs that only manifest themselves at normal-mode execution, for
34998 example, thread races, because debugger's interference with the program's
34999 timing may conceal the bugs. On the other hand, in some applications,
35000 it is not feasible for the debugger to interrupt the program's execution
35001 long enough for the developer to learn anything helpful about its behavior.
35002 If the program's correctness depends on its real-time behavior, delays
35003 introduced by a debugger might cause the program to fail, even when the
35004 code itself is correct. It is useful to be able to observe the program's
35005 behavior without interrupting it.
35007 Therefore, traditional debugging model is too intrusive to reproduce
35008 some bugs. In order to reduce the interference with the program, we can
35009 reduce the number of operations performed by debugger. The
35010 @dfn{In-Process Agent}, a shared library, is running within the same
35011 process with inferior, and is able to perform some debugging operations
35012 itself. As a result, debugger is only involved when necessary, and
35013 performance of debugging can be improved accordingly. Note that
35014 interference with program can be reduced but can't be removed completely,
35015 because the in-process agent will still stop or slow down the program.
35017 The in-process agent can interpret and execute Agent Expressions
35018 (@pxref{Agent Expressions}) during performing debugging operations. The
35019 agent expressions can be used for different purposes, such as collecting
35020 data in tracepoints, and condition evaluation in breakpoints.
35022 @anchor{Control Agent}
35023 You can control whether the in-process agent is used as an aid for
35024 debugging with the following commands:
35027 @kindex set agent on
35029 Causes the in-process agent to perform some operations on behalf of the
35030 debugger. Just which operations requested by the user will be done
35031 by the in-process agent depends on the its capabilities. For example,
35032 if you request to evaluate breakpoint conditions in the in-process agent,
35033 and the in-process agent has such capability as well, then breakpoint
35034 conditions will be evaluated in the in-process agent.
35036 @kindex set agent off
35037 @item set agent off
35038 Disables execution of debugging operations by the in-process agent. All
35039 of the operations will be performed by @value{GDBN}.
35043 Display the current setting of execution of debugging operations by
35044 the in-process agent.
35048 * In-Process Agent Protocol::
35051 @node In-Process Agent Protocol
35052 @section In-Process Agent Protocol
35053 @cindex in-process agent protocol
35055 The in-process agent is able to communicate with both @value{GDBN} and
35056 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35057 used for communications between @value{GDBN} or GDBserver and the IPA.
35058 In general, @value{GDBN} or GDBserver sends commands
35059 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35060 in-process agent replies back with the return result of the command, or
35061 some other information. The data sent to in-process agent is composed
35062 of primitive data types, such as 4-byte or 8-byte type, and composite
35063 types, which are called objects (@pxref{IPA Protocol Objects}).
35066 * IPA Protocol Objects::
35067 * IPA Protocol Commands::
35070 @node IPA Protocol Objects
35071 @subsection IPA Protocol Objects
35072 @cindex ipa protocol objects
35074 The commands sent to and results received from agent may contain some
35075 complex data types called @dfn{objects}.
35077 The in-process agent is running on the same machine with @value{GDBN}
35078 or GDBserver, so it doesn't have to handle as much differences between
35079 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35080 However, there are still some differences of two ends in two processes:
35084 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35085 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35087 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35088 GDBserver is compiled with one, and in-process agent is compiled with
35092 Here are the IPA Protocol Objects:
35096 agent expression object. It represents an agent expression
35097 (@pxref{Agent Expressions}).
35098 @anchor{agent expression object}
35100 tracepoint action object. It represents a tracepoint action
35101 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35102 memory, static trace data and to evaluate expression.
35103 @anchor{tracepoint action object}
35105 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35106 @anchor{tracepoint object}
35110 The following table describes important attributes of each IPA protocol
35113 @multitable @columnfractions .30 .20 .50
35114 @headitem Name @tab Size @tab Description
35115 @item @emph{agent expression object} @tab @tab
35116 @item length @tab 4 @tab length of bytes code
35117 @item byte code @tab @var{length} @tab contents of byte code
35118 @item @emph{tracepoint action for collecting memory} @tab @tab
35119 @item 'M' @tab 1 @tab type of tracepoint action
35120 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35121 address of the lowest byte to collect, otherwise @var{addr} is the offset
35122 of @var{basereg} for memory collecting.
35123 @item len @tab 8 @tab length of memory for collecting
35124 @item basereg @tab 4 @tab the register number containing the starting
35125 memory address for collecting.
35126 @item @emph{tracepoint action for collecting registers} @tab @tab
35127 @item 'R' @tab 1 @tab type of tracepoint action
35128 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35129 @item 'L' @tab 1 @tab type of tracepoint action
35130 @item @emph{tracepoint action for expression evaluation} @tab @tab
35131 @item 'X' @tab 1 @tab type of tracepoint action
35132 @item agent expression @tab length of @tab @ref{agent expression object}
35133 @item @emph{tracepoint object} @tab @tab
35134 @item number @tab 4 @tab number of tracepoint
35135 @item address @tab 8 @tab address of tracepoint inserted on
35136 @item type @tab 4 @tab type of tracepoint
35137 @item enabled @tab 1 @tab enable or disable of tracepoint
35138 @item step_count @tab 8 @tab step
35139 @item pass_count @tab 8 @tab pass
35140 @item numactions @tab 4 @tab number of tracepoint actions
35141 @item hit count @tab 8 @tab hit count
35142 @item trace frame usage @tab 8 @tab trace frame usage
35143 @item compiled_cond @tab 8 @tab compiled condition
35144 @item orig_size @tab 8 @tab orig size
35145 @item condition @tab 4 if condition is NULL otherwise length of
35146 @ref{agent expression object}
35147 @tab zero if condition is NULL, otherwise is
35148 @ref{agent expression object}
35149 @item actions @tab variable
35150 @tab numactions number of @ref{tracepoint action object}
35153 @node IPA Protocol Commands
35154 @subsection IPA Protocol Commands
35155 @cindex ipa protocol commands
35157 The spaces in each command are delimiters to ease reading this commands
35158 specification. They don't exist in real commands.
35162 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35163 Installs a new fast tracepoint described by @var{tracepoint_object}
35164 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
35165 head of @dfn{jumppad}, which is used to jump to data collection routine
35170 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35171 @var{target_address} is address of tracepoint in the inferior.
35172 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35173 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35174 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35175 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35182 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35183 is about to kill inferiors.
35191 @item probe_marker_at:@var{address}
35192 Asks in-process agent to probe the marker at @var{address}.
35199 @item unprobe_marker_at:@var{address}
35200 Asks in-process agent to unprobe the marker at @var{address}.
35204 @chapter Reporting Bugs in @value{GDBN}
35205 @cindex bugs in @value{GDBN}
35206 @cindex reporting bugs in @value{GDBN}
35208 Your bug reports play an essential role in making @value{GDBN} reliable.
35210 Reporting a bug may help you by bringing a solution to your problem, or it
35211 may not. But in any case the principal function of a bug report is to help
35212 the entire community by making the next version of @value{GDBN} work better. Bug
35213 reports are your contribution to the maintenance of @value{GDBN}.
35215 In order for a bug report to serve its purpose, you must include the
35216 information that enables us to fix the bug.
35219 * Bug Criteria:: Have you found a bug?
35220 * Bug Reporting:: How to report bugs
35224 @section Have You Found a Bug?
35225 @cindex bug criteria
35227 If you are not sure whether you have found a bug, here are some guidelines:
35230 @cindex fatal signal
35231 @cindex debugger crash
35232 @cindex crash of debugger
35234 If the debugger gets a fatal signal, for any input whatever, that is a
35235 @value{GDBN} bug. Reliable debuggers never crash.
35237 @cindex error on valid input
35239 If @value{GDBN} produces an error message for valid input, that is a
35240 bug. (Note that if you're cross debugging, the problem may also be
35241 somewhere in the connection to the target.)
35243 @cindex invalid input
35245 If @value{GDBN} does not produce an error message for invalid input,
35246 that is a bug. However, you should note that your idea of
35247 ``invalid input'' might be our idea of ``an extension'' or ``support
35248 for traditional practice''.
35251 If you are an experienced user of debugging tools, your suggestions
35252 for improvement of @value{GDBN} are welcome in any case.
35255 @node Bug Reporting
35256 @section How to Report Bugs
35257 @cindex bug reports
35258 @cindex @value{GDBN} bugs, reporting
35260 A number of companies and individuals offer support for @sc{gnu} products.
35261 If you obtained @value{GDBN} from a support organization, we recommend you
35262 contact that organization first.
35264 You can find contact information for many support companies and
35265 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35267 @c should add a web page ref...
35270 @ifset BUGURL_DEFAULT
35271 In any event, we also recommend that you submit bug reports for
35272 @value{GDBN}. The preferred method is to submit them directly using
35273 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35274 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35277 @strong{Do not send bug reports to @samp{info-gdb}, or to
35278 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35279 not want to receive bug reports. Those that do have arranged to receive
35282 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35283 serves as a repeater. The mailing list and the newsgroup carry exactly
35284 the same messages. Often people think of posting bug reports to the
35285 newsgroup instead of mailing them. This appears to work, but it has one
35286 problem which can be crucial: a newsgroup posting often lacks a mail
35287 path back to the sender. Thus, if we need to ask for more information,
35288 we may be unable to reach you. For this reason, it is better to send
35289 bug reports to the mailing list.
35291 @ifclear BUGURL_DEFAULT
35292 In any event, we also recommend that you submit bug reports for
35293 @value{GDBN} to @value{BUGURL}.
35297 The fundamental principle of reporting bugs usefully is this:
35298 @strong{report all the facts}. If you are not sure whether to state a
35299 fact or leave it out, state it!
35301 Often people omit facts because they think they know what causes the
35302 problem and assume that some details do not matter. Thus, you might
35303 assume that the name of the variable you use in an example does not matter.
35304 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35305 stray memory reference which happens to fetch from the location where that
35306 name is stored in memory; perhaps, if the name were different, the contents
35307 of that location would fool the debugger into doing the right thing despite
35308 the bug. Play it safe and give a specific, complete example. That is the
35309 easiest thing for you to do, and the most helpful.
35311 Keep in mind that the purpose of a bug report is to enable us to fix the
35312 bug. It may be that the bug has been reported previously, but neither
35313 you nor we can know that unless your bug report is complete and
35316 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35317 bell?'' Those bug reports are useless, and we urge everyone to
35318 @emph{refuse to respond to them} except to chide the sender to report
35321 To enable us to fix the bug, you should include all these things:
35325 The version of @value{GDBN}. @value{GDBN} announces it if you start
35326 with no arguments; you can also print it at any time using @code{show
35329 Without this, we will not know whether there is any point in looking for
35330 the bug in the current version of @value{GDBN}.
35333 The type of machine you are using, and the operating system name and
35337 The details of the @value{GDBN} build-time configuration.
35338 @value{GDBN} shows these details if you invoke it with the
35339 @option{--configuration} command-line option, or if you type
35340 @code{show configuration} at @value{GDBN}'s prompt.
35343 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35344 ``@value{GCC}--2.8.1''.
35347 What compiler (and its version) was used to compile the program you are
35348 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35349 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35350 to get this information; for other compilers, see the documentation for
35354 The command arguments you gave the compiler to compile your example and
35355 observe the bug. For example, did you use @samp{-O}? To guarantee
35356 you will not omit something important, list them all. A copy of the
35357 Makefile (or the output from make) is sufficient.
35359 If we were to try to guess the arguments, we would probably guess wrong
35360 and then we might not encounter the bug.
35363 A complete input script, and all necessary source files, that will
35367 A description of what behavior you observe that you believe is
35368 incorrect. For example, ``It gets a fatal signal.''
35370 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35371 will certainly notice it. But if the bug is incorrect output, we might
35372 not notice unless it is glaringly wrong. You might as well not give us
35373 a chance to make a mistake.
35375 Even if the problem you experience is a fatal signal, you should still
35376 say so explicitly. Suppose something strange is going on, such as, your
35377 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35378 the C library on your system. (This has happened!) Your copy might
35379 crash and ours would not. If you told us to expect a crash, then when
35380 ours fails to crash, we would know that the bug was not happening for
35381 us. If you had not told us to expect a crash, then we would not be able
35382 to draw any conclusion from our observations.
35385 @cindex recording a session script
35386 To collect all this information, you can use a session recording program
35387 such as @command{script}, which is available on many Unix systems.
35388 Just run your @value{GDBN} session inside @command{script} and then
35389 include the @file{typescript} file with your bug report.
35391 Another way to record a @value{GDBN} session is to run @value{GDBN}
35392 inside Emacs and then save the entire buffer to a file.
35395 If you wish to suggest changes to the @value{GDBN} source, send us context
35396 diffs. If you even discuss something in the @value{GDBN} source, refer to
35397 it by context, not by line number.
35399 The line numbers in our development sources will not match those in your
35400 sources. Your line numbers would convey no useful information to us.
35404 Here are some things that are not necessary:
35408 A description of the envelope of the bug.
35410 Often people who encounter a bug spend a lot of time investigating
35411 which changes to the input file will make the bug go away and which
35412 changes will not affect it.
35414 This is often time consuming and not very useful, because the way we
35415 will find the bug is by running a single example under the debugger
35416 with breakpoints, not by pure deduction from a series of examples.
35417 We recommend that you save your time for something else.
35419 Of course, if you can find a simpler example to report @emph{instead}
35420 of the original one, that is a convenience for us. Errors in the
35421 output will be easier to spot, running under the debugger will take
35422 less time, and so on.
35424 However, simplification is not vital; if you do not want to do this,
35425 report the bug anyway and send us the entire test case you used.
35428 A patch for the bug.
35430 A patch for the bug does help us if it is a good one. But do not omit
35431 the necessary information, such as the test case, on the assumption that
35432 a patch is all we need. We might see problems with your patch and decide
35433 to fix the problem another way, or we might not understand it at all.
35435 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35436 construct an example that will make the program follow a certain path
35437 through the code. If you do not send us the example, we will not be able
35438 to construct one, so we will not be able to verify that the bug is fixed.
35440 And if we cannot understand what bug you are trying to fix, or why your
35441 patch should be an improvement, we will not install it. A test case will
35442 help us to understand.
35445 A guess about what the bug is or what it depends on.
35447 Such guesses are usually wrong. Even we cannot guess right about such
35448 things without first using the debugger to find the facts.
35451 @c The readline documentation is distributed with the readline code
35452 @c and consists of the two following files:
35455 @c Use -I with makeinfo to point to the appropriate directory,
35456 @c environment var TEXINPUTS with TeX.
35457 @ifclear SYSTEM_READLINE
35458 @include rluser.texi
35459 @include hsuser.texi
35463 @appendix In Memoriam
35465 The @value{GDBN} project mourns the loss of the following long-time
35470 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35471 to Free Software in general. Outside of @value{GDBN}, he was known in
35472 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35474 @item Michael Snyder
35475 Michael was one of the Global Maintainers of the @value{GDBN} project,
35476 with contributions recorded as early as 1996, until 2011. In addition
35477 to his day to day participation, he was a large driving force behind
35478 adding Reverse Debugging to @value{GDBN}.
35481 Beyond their technical contributions to the project, they were also
35482 enjoyable members of the Free Software Community. We will miss them.
35484 @node Formatting Documentation
35485 @appendix Formatting Documentation
35487 @cindex @value{GDBN} reference card
35488 @cindex reference card
35489 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35490 for printing with PostScript or Ghostscript, in the @file{gdb}
35491 subdirectory of the main source directory@footnote{In
35492 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35493 release.}. If you can use PostScript or Ghostscript with your printer,
35494 you can print the reference card immediately with @file{refcard.ps}.
35496 The release also includes the source for the reference card. You
35497 can format it, using @TeX{}, by typing:
35503 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35504 mode on US ``letter'' size paper;
35505 that is, on a sheet 11 inches wide by 8.5 inches
35506 high. You will need to specify this form of printing as an option to
35507 your @sc{dvi} output program.
35509 @cindex documentation
35511 All the documentation for @value{GDBN} comes as part of the machine-readable
35512 distribution. The documentation is written in Texinfo format, which is
35513 a documentation system that uses a single source file to produce both
35514 on-line information and a printed manual. You can use one of the Info
35515 formatting commands to create the on-line version of the documentation
35516 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35518 @value{GDBN} includes an already formatted copy of the on-line Info
35519 version of this manual in the @file{gdb} subdirectory. The main Info
35520 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35521 subordinate files matching @samp{gdb.info*} in the same directory. If
35522 necessary, you can print out these files, or read them with any editor;
35523 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35524 Emacs or the standalone @code{info} program, available as part of the
35525 @sc{gnu} Texinfo distribution.
35527 If you want to format these Info files yourself, you need one of the
35528 Info formatting programs, such as @code{texinfo-format-buffer} or
35531 If you have @code{makeinfo} installed, and are in the top level
35532 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35533 version @value{GDBVN}), you can make the Info file by typing:
35540 If you want to typeset and print copies of this manual, you need @TeX{},
35541 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35542 Texinfo definitions file.
35544 @TeX{} is a typesetting program; it does not print files directly, but
35545 produces output files called @sc{dvi} files. To print a typeset
35546 document, you need a program to print @sc{dvi} files. If your system
35547 has @TeX{} installed, chances are it has such a program. The precise
35548 command to use depends on your system; @kbd{lpr -d} is common; another
35549 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35550 require a file name without any extension or a @samp{.dvi} extension.
35552 @TeX{} also requires a macro definitions file called
35553 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35554 written in Texinfo format. On its own, @TeX{} cannot either read or
35555 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35556 and is located in the @file{gdb-@var{version-number}/texinfo}
35559 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35560 typeset and print this manual. First switch to the @file{gdb}
35561 subdirectory of the main source directory (for example, to
35562 @file{gdb-@value{GDBVN}/gdb}) and type:
35568 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35570 @node Installing GDB
35571 @appendix Installing @value{GDBN}
35572 @cindex installation
35575 * Requirements:: Requirements for building @value{GDBN}
35576 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35577 * Separate Objdir:: Compiling @value{GDBN} in another directory
35578 * Config Names:: Specifying names for hosts and targets
35579 * Configure Options:: Summary of options for configure
35580 * System-wide configuration:: Having a system-wide init file
35584 @section Requirements for Building @value{GDBN}
35585 @cindex building @value{GDBN}, requirements for
35587 Building @value{GDBN} requires various tools and packages to be available.
35588 Other packages will be used only if they are found.
35590 @heading Tools/Packages Necessary for Building @value{GDBN}
35592 @item C@t{++}11 compiler
35593 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35594 recent C@t{++}11 compiler, e.g.@: GCC.
35597 @value{GDBN}'s build system relies on features only found in the GNU
35598 make program. Other variants of @code{make} will not work.
35601 @heading Tools/Packages Optional for Building @value{GDBN}
35605 @value{GDBN} can use the Expat XML parsing library. This library may be
35606 included with your operating system distribution; if it is not, you
35607 can get the latest version from @url{http://expat.sourceforge.net}.
35608 The @file{configure} script will search for this library in several
35609 standard locations; if it is installed in an unusual path, you can
35610 use the @option{--with-libexpat-prefix} option to specify its location.
35616 Remote protocol memory maps (@pxref{Memory Map Format})
35618 Target descriptions (@pxref{Target Descriptions})
35620 Remote shared library lists (@xref{Library List Format},
35621 or alternatively @pxref{Library List Format for SVR4 Targets})
35623 MS-Windows shared libraries (@pxref{Shared Libraries})
35625 Traceframe info (@pxref{Traceframe Info Format})
35627 Branch trace (@pxref{Branch Trace Format},
35628 @pxref{Branch Trace Configuration Format})
35632 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35633 default, @value{GDBN} will be compiled if the Guile libraries are
35634 installed and are found by @file{configure}. You can use the
35635 @code{--with-guile} option to request Guile, and pass either the Guile
35636 version number or the file name of the relevant @code{pkg-config}
35637 program to choose a particular version of Guile.
35640 @value{GDBN}'s features related to character sets (@pxref{Character
35641 Sets}) require a functioning @code{iconv} implementation. If you are
35642 on a GNU system, then this is provided by the GNU C Library. Some
35643 other systems also provide a working @code{iconv}.
35645 If @value{GDBN} is using the @code{iconv} program which is installed
35646 in a non-standard place, you will need to tell @value{GDBN} where to
35647 find it. This is done with @option{--with-iconv-bin} which specifies
35648 the directory that contains the @code{iconv} program. This program is
35649 run in order to make a list of the available character sets.
35651 On systems without @code{iconv}, you can install GNU Libiconv. If
35652 Libiconv is installed in a standard place, @value{GDBN} will
35653 automatically use it if it is needed. If you have previously
35654 installed Libiconv in a non-standard place, you can use the
35655 @option{--with-libiconv-prefix} option to @file{configure}.
35657 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35658 arrange to build Libiconv if a directory named @file{libiconv} appears
35659 in the top-most source directory. If Libiconv is built this way, and
35660 if the operating system does not provide a suitable @code{iconv}
35661 implementation, then the just-built library will automatically be used
35662 by @value{GDBN}. One easy way to set this up is to download GNU
35663 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35664 source tree, and then rename the directory holding the Libiconv source
35665 code to @samp{libiconv}.
35668 @value{GDBN} can support debugging sections that are compressed with
35669 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35670 included with your operating system, you can find it in the xz package
35671 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35672 the usual place, then the @file{configure} script will use it
35673 automatically. If it is installed in an unusual path, you can use the
35674 @option{--with-lzma-prefix} option to specify its location.
35678 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35679 library. This library may be included with your operating system
35680 distribution; if it is not, you can get the latest version from
35681 @url{http://www.mpfr.org}. The @file{configure} script will search
35682 for this library in several standard locations; if it is installed
35683 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35684 option to specify its location.
35686 GNU MPFR is used to emulate target floating-point arithmetic during
35687 expression evaluation when the target uses different floating-point
35688 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35689 will fall back to using host floating-point arithmetic.
35692 @value{GDBN} can be scripted using Python language. @xref{Python}.
35693 By default, @value{GDBN} will be compiled if the Python libraries are
35694 installed and are found by @file{configure}. You can use the
35695 @code{--with-python} option to request Python, and pass either the
35696 file name of the relevant @code{python} executable, or the name of the
35697 directory in which Python is installed, to choose a particular
35698 installation of Python.
35701 @cindex compressed debug sections
35702 @value{GDBN} will use the @samp{zlib} library, if available, to read
35703 compressed debug sections. Some linkers, such as GNU gold, are capable
35704 of producing binaries with compressed debug sections. If @value{GDBN}
35705 is compiled with @samp{zlib}, it will be able to read the debug
35706 information in such binaries.
35708 The @samp{zlib} library is likely included with your operating system
35709 distribution; if it is not, you can get the latest version from
35710 @url{http://zlib.net}.
35713 @node Running Configure
35714 @section Invoking the @value{GDBN} @file{configure} Script
35715 @cindex configuring @value{GDBN}
35716 @value{GDBN} comes with a @file{configure} script that automates the process
35717 of preparing @value{GDBN} for installation; you can then use @code{make} to
35718 build the @code{gdb} program.
35720 @c irrelevant in info file; it's as current as the code it lives with.
35721 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35722 look at the @file{README} file in the sources; we may have improved the
35723 installation procedures since publishing this manual.}
35726 The @value{GDBN} distribution includes all the source code you need for
35727 @value{GDBN} in a single directory, whose name is usually composed by
35728 appending the version number to @samp{gdb}.
35730 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35731 @file{gdb-@value{GDBVN}} directory. That directory contains:
35734 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35735 script for configuring @value{GDBN} and all its supporting libraries
35737 @item gdb-@value{GDBVN}/gdb
35738 the source specific to @value{GDBN} itself
35740 @item gdb-@value{GDBVN}/bfd
35741 source for the Binary File Descriptor library
35743 @item gdb-@value{GDBVN}/include
35744 @sc{gnu} include files
35746 @item gdb-@value{GDBVN}/libiberty
35747 source for the @samp{-liberty} free software library
35749 @item gdb-@value{GDBVN}/opcodes
35750 source for the library of opcode tables and disassemblers
35752 @item gdb-@value{GDBVN}/readline
35753 source for the @sc{gnu} command-line interface
35756 There may be other subdirectories as well.
35758 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35759 from the @file{gdb-@var{version-number}} source directory, which in
35760 this example is the @file{gdb-@value{GDBVN}} directory.
35762 First switch to the @file{gdb-@var{version-number}} source directory
35763 if you are not already in it; then run @file{configure}. Pass the
35764 identifier for the platform on which @value{GDBN} will run as an
35770 cd gdb-@value{GDBVN}
35775 Running @samp{configure} and then running @code{make} builds the
35776 included supporting libraries, then @code{gdb} itself. The configured
35777 source files, and the binaries, are left in the corresponding source
35781 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35782 system does not recognize this automatically when you run a different
35783 shell, you may need to run @code{sh} on it explicitly:
35789 You should run the @file{configure} script from the top directory in the
35790 source tree, the @file{gdb-@var{version-number}} directory. If you run
35791 @file{configure} from one of the subdirectories, you will configure only
35792 that subdirectory. That is usually not what you want. In particular,
35793 if you run the first @file{configure} from the @file{gdb} subdirectory
35794 of the @file{gdb-@var{version-number}} directory, you will omit the
35795 configuration of @file{bfd}, @file{readline}, and other sibling
35796 directories of the @file{gdb} subdirectory. This leads to build errors
35797 about missing include files such as @file{bfd/bfd.h}.
35799 You can install @code{@value{GDBN}} anywhere. The best way to do this
35800 is to pass the @code{--prefix} option to @code{configure}, and then
35801 install it with @code{make install}.
35803 @node Separate Objdir
35804 @section Compiling @value{GDBN} in Another Directory
35806 If you want to run @value{GDBN} versions for several host or target machines,
35807 you need a different @code{gdb} compiled for each combination of
35808 host and target. @file{configure} is designed to make this easy by
35809 allowing you to generate each configuration in a separate subdirectory,
35810 rather than in the source directory. If your @code{make} program
35811 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35812 @code{make} in each of these directories builds the @code{gdb}
35813 program specified there.
35815 To build @code{gdb} in a separate directory, run @file{configure}
35816 with the @samp{--srcdir} option to specify where to find the source.
35817 (You also need to specify a path to find @file{configure}
35818 itself from your working directory. If the path to @file{configure}
35819 would be the same as the argument to @samp{--srcdir}, you can leave out
35820 the @samp{--srcdir} option; it is assumed.)
35822 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35823 separate directory for a Sun 4 like this:
35827 cd gdb-@value{GDBVN}
35830 ../gdb-@value{GDBVN}/configure
35835 When @file{configure} builds a configuration using a remote source
35836 directory, it creates a tree for the binaries with the same structure
35837 (and using the same names) as the tree under the source directory. In
35838 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35839 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35840 @file{gdb-sun4/gdb}.
35842 Make sure that your path to the @file{configure} script has just one
35843 instance of @file{gdb} in it. If your path to @file{configure} looks
35844 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35845 one subdirectory of @value{GDBN}, not the whole package. This leads to
35846 build errors about missing include files such as @file{bfd/bfd.h}.
35848 One popular reason to build several @value{GDBN} configurations in separate
35849 directories is to configure @value{GDBN} for cross-compiling (where
35850 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35851 programs that run on another machine---the @dfn{target}).
35852 You specify a cross-debugging target by
35853 giving the @samp{--target=@var{target}} option to @file{configure}.
35855 When you run @code{make} to build a program or library, you must run
35856 it in a configured directory---whatever directory you were in when you
35857 called @file{configure} (or one of its subdirectories).
35859 The @code{Makefile} that @file{configure} generates in each source
35860 directory also runs recursively. If you type @code{make} in a source
35861 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35862 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35863 will build all the required libraries, and then build GDB.
35865 When you have multiple hosts or targets configured in separate
35866 directories, you can run @code{make} on them in parallel (for example,
35867 if they are NFS-mounted on each of the hosts); they will not interfere
35871 @section Specifying Names for Hosts and Targets
35873 The specifications used for hosts and targets in the @file{configure}
35874 script are based on a three-part naming scheme, but some short predefined
35875 aliases are also supported. The full naming scheme encodes three pieces
35876 of information in the following pattern:
35879 @var{architecture}-@var{vendor}-@var{os}
35882 For example, you can use the alias @code{sun4} as a @var{host} argument,
35883 or as the value for @var{target} in a @code{--target=@var{target}}
35884 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35886 The @file{configure} script accompanying @value{GDBN} does not provide
35887 any query facility to list all supported host and target names or
35888 aliases. @file{configure} calls the Bourne shell script
35889 @code{config.sub} to map abbreviations to full names; you can read the
35890 script, if you wish, or you can use it to test your guesses on
35891 abbreviations---for example:
35894 % sh config.sub i386-linux
35896 % sh config.sub alpha-linux
35897 alpha-unknown-linux-gnu
35898 % sh config.sub hp9k700
35900 % sh config.sub sun4
35901 sparc-sun-sunos4.1.1
35902 % sh config.sub sun3
35903 m68k-sun-sunos4.1.1
35904 % sh config.sub i986v
35905 Invalid configuration `i986v': machine `i986v' not recognized
35909 @code{config.sub} is also distributed in the @value{GDBN} source
35910 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35912 @node Configure Options
35913 @section @file{configure} Options
35915 Here is a summary of the @file{configure} options and arguments that
35916 are most often useful for building @value{GDBN}. @file{configure}
35917 also has several other options not listed here. @inforef{Running
35918 configure scripts,,autoconf.info}, for a full
35919 explanation of @file{configure}.
35922 configure @r{[}--help@r{]}
35923 @r{[}--prefix=@var{dir}@r{]}
35924 @r{[}--exec-prefix=@var{dir}@r{]}
35925 @r{[}--srcdir=@var{dirname}@r{]}
35926 @r{[}--target=@var{target}@r{]}
35930 You may introduce options with a single @samp{-} rather than
35931 @samp{--} if you prefer; but you may abbreviate option names if you use
35936 Display a quick summary of how to invoke @file{configure}.
35938 @item --prefix=@var{dir}
35939 Configure the source to install programs and files under directory
35942 @item --exec-prefix=@var{dir}
35943 Configure the source to install programs under directory
35946 @c avoid splitting the warning from the explanation:
35948 @item --srcdir=@var{dirname}
35949 Use this option to make configurations in directories separate from the
35950 @value{GDBN} source directories. Among other things, you can use this to
35951 build (or maintain) several configurations simultaneously, in separate
35952 directories. @file{configure} writes configuration-specific files in
35953 the current directory, but arranges for them to use the source in the
35954 directory @var{dirname}. @file{configure} creates directories under
35955 the working directory in parallel to the source directories below
35958 @item --target=@var{target}
35959 Configure @value{GDBN} for cross-debugging programs running on the specified
35960 @var{target}. Without this option, @value{GDBN} is configured to debug
35961 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35963 There is no convenient way to generate a list of all available
35964 targets. Also see the @code{--enable-targets} option, below.
35967 There are many other options that are specific to @value{GDBN}. This
35968 lists just the most common ones; there are some very specialized
35969 options not described here.
35972 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
35973 @itemx --enable-targets=all
35974 Configure @value{GDBN} for cross-debugging programs running on the
35975 specified list of targets. The special value @samp{all} configures
35976 @value{GDBN} for debugging programs running on any target it supports.
35978 @item --with-gdb-datadir=@var{path}
35979 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
35980 here for certain supporting files or scripts. This defaults to the
35981 @file{gdb} subdirectory of @samp{datadi} (which can be set using
35984 @item --with-relocated-sources=@var{dir}
35985 Sets up the default source path substitution rule so that directory
35986 names recorded in debug information will be automatically adjusted for
35987 any directory under @var{dir}. @var{dir} should be a subdirectory of
35988 @value{GDBN}'s configured prefix, the one mentioned in the
35989 @code{--prefix} or @code{--exec-prefix} options to configure. This
35990 option is useful if GDB is supposed to be moved to a different place
35993 @item --enable-64-bit-bfd
35994 Enable 64-bit support in BFD on 32-bit hosts.
35996 @item --disable-gdbmi
35997 Build @value{GDBN} without the GDB/MI machine interface
36001 Build @value{GDBN} with the text-mode full-screen user interface
36002 (TUI). Requires a curses library (ncurses and cursesX are also
36005 @item --with-curses
36006 Use the curses library instead of the termcap library, for text-mode
36007 terminal operations.
36009 @item --with-libunwind-ia64
36010 Use the libunwind library for unwinding function call stack on ia64
36011 target platforms. See http://www.nongnu.org/libunwind/index.html for
36014 @item --with-system-readline
36015 Use the readline library installed on the host, rather than the
36016 library supplied as part of @value{GDBN}.
36018 @item --with-system-zlib
36019 Use the zlib library installed on the host, rather than the library
36020 supplied as part of @value{GDBN}.
36023 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36024 default if libexpat is installed and found at configure time.) This
36025 library is used to read XML files supplied with @value{GDBN}. If it
36026 is unavailable, some features, such as remote protocol memory maps,
36027 target descriptions, and shared library lists, that are based on XML
36028 files, will not be available in @value{GDBN}. If your host does not
36029 have libexpat installed, you can get the latest version from
36030 `http://expat.sourceforge.net'.
36032 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36034 Build @value{GDBN} with GNU libiconv, a character set encoding
36035 conversion library. This is not done by default, as on GNU systems
36036 the @code{iconv} that is built in to the C library is sufficient. If
36037 your host does not have a working @code{iconv}, you can get the latest
36038 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36040 @value{GDBN}'s build system also supports building GNU libiconv as
36041 part of the overall build. @xref{Requirements}.
36044 Build @value{GDBN} with LZMA, a compression library. (Done by default
36045 if liblzma is installed and found at configure time.) LZMA is used by
36046 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36047 platforms using the ELF object file format. If your host does not
36048 have liblzma installed, you can get the latest version from
36049 `https://tukaani.org/xz/'.
36052 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
36053 floating-point computation with correct rounding. (Done by default if
36054 GNU MPFR is installed and found at configure time.) This library is
36055 used to emulate target floating-point arithmetic during expression
36056 evaluation when the target uses different floating-point formats than
36057 the host. If GNU MPFR is not available, @value{GDBN} will fall back
36058 to using host floating-point arithmetic. If your host does not have
36059 GNU MPFR installed, you can get the latest version from
36060 `http://www.mpfr.org'.
36062 @item --with-python@r{[}=@var{python}@r{]}
36063 Build @value{GDBN} with Python scripting support. (Done by default if
36064 libpython is present and found at configure time.) Python makes
36065 @value{GDBN} scripting much more powerful than the restricted CLI
36066 scripting language. If your host does not have Python installed, you
36067 can find it on `http://www.python.org/download/'. The oldest version
36068 of Python supported by GDB is 2.6. The optional argument @var{python}
36069 is used to find the Python headers and libraries. It can be either
36070 the name of a Python executable, or the name of the directory in which
36071 Python is installed.
36073 @item --with-guile[=GUILE]'
36074 Build @value{GDBN} with GNU Guile scripting support. (Done by default
36075 if libguile is present and found at configure time.) If your host
36076 does not have Guile installed, you can find it at
36077 `https://www.gnu.org/software/guile/'. The optional argument GUILE
36078 can be a version number, which will cause @code{configure} to try to
36079 use that version of Guile; or the file name of a @code{pkg-config}
36080 executable, which will be queried to find the information needed to
36081 compile and link against Guile.
36083 @item --without-included-regex
36084 Don't use the regex library included with @value{GDBN} (as part of the
36085 libiberty library). This is the default on hosts with version 2 of
36088 @item --with-sysroot=@var{dir}
36089 Use @var{dir} as the default system root directory for libraries whose
36090 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
36091 @var{dir} can be modified at run time by using the @command{set
36092 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
36093 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
36094 default system root will be automatically adjusted if and when
36095 @value{GDBN} is moved to a different location.
36097 @item --with-system-gdbinit=@var{file}
36098 Configure @value{GDBN} to automatically load a system-wide init file.
36099 @var{file} should be an absolute file name. If @var{file} is in a
36100 directory under the configured prefix, and @value{GDBN} is moved to
36101 another location after being built, the location of the system-wide
36102 init file will be adjusted accordingly.
36104 @item --enable-build-warnings
36105 When building the @value{GDBN} sources, ask the compiler to warn about
36106 any code which looks even vaguely suspicious. It passes many
36107 different warning flags, depending on the exact version of the
36108 compiler you are using.
36110 @item --enable-werror
36111 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
36112 to the compiler, which will fail the compilation if the compiler
36113 outputs any warning messages.
36115 @item --enable-ubsan
36116 Enable the GCC undefined behavior sanitizer. This is disabled by
36117 default, but passing @code{--enable-ubsan=yes} or
36118 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
36119 undefined behavior sanitizer checks for C@t{++} undefined behavior.
36120 It has a performance cost, so if you are looking at @value{GDBN}'s
36121 performance, you should disable it. The undefined behavior sanitizer
36122 was first introduced in GCC 4.9.
36125 @node System-wide configuration
36126 @section System-wide configuration and settings
36127 @cindex system-wide init file
36129 @value{GDBN} can be configured to have a system-wide init file;
36130 this file will be read and executed at startup (@pxref{Startup, , What
36131 @value{GDBN} does during startup}).
36133 Here is the corresponding configure option:
36136 @item --with-system-gdbinit=@var{file}
36137 Specify that the default location of the system-wide init file is
36141 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36142 it may be subject to relocation. Two possible cases:
36146 If the default location of this init file contains @file{$prefix},
36147 it will be subject to relocation. Suppose that the configure options
36148 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36149 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36150 init file is looked for as @file{$install/etc/gdbinit} instead of
36151 @file{$prefix/etc/gdbinit}.
36154 By contrast, if the default location does not contain the prefix,
36155 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36156 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36157 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36158 wherever @value{GDBN} is installed.
36161 If the configured location of the system-wide init file (as given by the
36162 @option{--with-system-gdbinit} option at configure time) is in the
36163 data-directory (as specified by @option{--with-gdb-datadir} at configure
36164 time) or in one of its subdirectories, then @value{GDBN} will look for the
36165 system-wide init file in the directory specified by the
36166 @option{--data-directory} command-line option.
36167 Note that the system-wide init file is only read once, during @value{GDBN}
36168 initialization. If the data-directory is changed after @value{GDBN} has
36169 started with the @code{set data-directory} command, the file will not be
36173 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36176 @node System-wide Configuration Scripts
36177 @subsection Installed System-wide Configuration Scripts
36178 @cindex system-wide configuration scripts
36180 The @file{system-gdbinit} directory, located inside the data-directory
36181 (as specified by @option{--with-gdb-datadir} at configure time) contains
36182 a number of scripts which can be used as system-wide init files. To
36183 automatically source those scripts at startup, @value{GDBN} should be
36184 configured with @option{--with-system-gdbinit}. Otherwise, any user
36185 should be able to source them by hand as needed.
36187 The following scripts are currently available:
36190 @item @file{elinos.py}
36192 @cindex ELinOS system-wide configuration script
36193 This script is useful when debugging a program on an ELinOS target.
36194 It takes advantage of the environment variables defined in a standard
36195 ELinOS environment in order to determine the location of the system
36196 shared libraries, and then sets the @samp{solib-absolute-prefix}
36197 and @samp{solib-search-path} variables appropriately.
36199 @item @file{wrs-linux.py}
36200 @pindex wrs-linux.py
36201 @cindex Wind River Linux system-wide configuration script
36202 This script is useful when debugging a program on a target running
36203 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36204 the host-side sysroot used by the target system.
36208 @node Maintenance Commands
36209 @appendix Maintenance Commands
36210 @cindex maintenance commands
36211 @cindex internal commands
36213 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36214 includes a number of commands intended for @value{GDBN} developers,
36215 that are not documented elsewhere in this manual. These commands are
36216 provided here for reference. (For commands that turn on debugging
36217 messages, see @ref{Debugging Output}.)
36220 @kindex maint agent
36221 @kindex maint agent-eval
36222 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36223 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36224 Translate the given @var{expression} into remote agent bytecodes.
36225 This command is useful for debugging the Agent Expression mechanism
36226 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36227 expression useful for data collection, such as by tracepoints, while
36228 @samp{maint agent-eval} produces an expression that evaluates directly
36229 to a result. For instance, a collection expression for @code{globa +
36230 globb} will include bytecodes to record four bytes of memory at each
36231 of the addresses of @code{globa} and @code{globb}, while discarding
36232 the result of the addition, while an evaluation expression will do the
36233 addition and return the sum.
36234 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36235 If not, generate remote agent bytecode for current frame PC address.
36237 @kindex maint agent-printf
36238 @item maint agent-printf @var{format},@var{expr},...
36239 Translate the given format string and list of argument expressions
36240 into remote agent bytecodes and display them as a disassembled list.
36241 This command is useful for debugging the agent version of dynamic
36242 printf (@pxref{Dynamic Printf}).
36244 @kindex maint info breakpoints
36245 @item @anchor{maint info breakpoints}maint info breakpoints
36246 Using the same format as @samp{info breakpoints}, display both the
36247 breakpoints you've set explicitly, and those @value{GDBN} is using for
36248 internal purposes. Internal breakpoints are shown with negative
36249 breakpoint numbers. The type column identifies what kind of breakpoint
36254 Normal, explicitly set breakpoint.
36257 Normal, explicitly set watchpoint.
36260 Internal breakpoint, used to handle correctly stepping through
36261 @code{longjmp} calls.
36263 @item longjmp resume
36264 Internal breakpoint at the target of a @code{longjmp}.
36267 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36270 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36273 Shared library events.
36277 @kindex maint info btrace
36278 @item maint info btrace
36279 Pint information about raw branch tracing data.
36281 @kindex maint btrace packet-history
36282 @item maint btrace packet-history
36283 Print the raw branch trace packets that are used to compute the
36284 execution history for the @samp{record btrace} command. Both the
36285 information and the format in which it is printed depend on the btrace
36290 For the BTS recording format, print a list of blocks of sequential
36291 code. For each block, the following information is printed:
36295 Newer blocks have higher numbers. The oldest block has number zero.
36296 @item Lowest @samp{PC}
36297 @item Highest @samp{PC}
36301 For the Intel Processor Trace recording format, print a list of
36302 Intel Processor Trace packets. For each packet, the following
36303 information is printed:
36306 @item Packet number
36307 Newer packets have higher numbers. The oldest packet has number zero.
36309 The packet's offset in the trace stream.
36310 @item Packet opcode and payload
36314 @kindex maint btrace clear-packet-history
36315 @item maint btrace clear-packet-history
36316 Discards the cached packet history printed by the @samp{maint btrace
36317 packet-history} command. The history will be computed again when
36320 @kindex maint btrace clear
36321 @item maint btrace clear
36322 Discard the branch trace data. The data will be fetched anew and the
36323 branch trace will be recomputed when needed.
36325 This implicitly truncates the branch trace to a single branch trace
36326 buffer. When updating branch trace incrementally, the branch trace
36327 available to @value{GDBN} may be bigger than a single branch trace
36330 @kindex maint set btrace pt skip-pad
36331 @item maint set btrace pt skip-pad
36332 @kindex maint show btrace pt skip-pad
36333 @item maint show btrace pt skip-pad
36334 Control whether @value{GDBN} will skip PAD packets when computing the
36337 @kindex set displaced-stepping
36338 @kindex show displaced-stepping
36339 @cindex displaced stepping support
36340 @cindex out-of-line single-stepping
36341 @item set displaced-stepping
36342 @itemx show displaced-stepping
36343 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36344 if the target supports it. Displaced stepping is a way to single-step
36345 over breakpoints without removing them from the inferior, by executing
36346 an out-of-line copy of the instruction that was originally at the
36347 breakpoint location. It is also known as out-of-line single-stepping.
36350 @item set displaced-stepping on
36351 If the target architecture supports it, @value{GDBN} will use
36352 displaced stepping to step over breakpoints.
36354 @item set displaced-stepping off
36355 @value{GDBN} will not use displaced stepping to step over breakpoints,
36356 even if such is supported by the target architecture.
36358 @cindex non-stop mode, and @samp{set displaced-stepping}
36359 @item set displaced-stepping auto
36360 This is the default mode. @value{GDBN} will use displaced stepping
36361 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36362 architecture supports displaced stepping.
36365 @kindex maint check-psymtabs
36366 @item maint check-psymtabs
36367 Check the consistency of currently expanded psymtabs versus symtabs.
36368 Use this to check, for example, whether a symbol is in one but not the other.
36370 @kindex maint check-symtabs
36371 @item maint check-symtabs
36372 Check the consistency of currently expanded symtabs.
36374 @kindex maint expand-symtabs
36375 @item maint expand-symtabs [@var{regexp}]
36376 Expand symbol tables.
36377 If @var{regexp} is specified, only expand symbol tables for file
36378 names matching @var{regexp}.
36380 @kindex maint set catch-demangler-crashes
36381 @kindex maint show catch-demangler-crashes
36382 @cindex demangler crashes
36383 @item maint set catch-demangler-crashes [on|off]
36384 @itemx maint show catch-demangler-crashes
36385 Control whether @value{GDBN} should attempt to catch crashes in the
36386 symbol name demangler. The default is to attempt to catch crashes.
36387 If enabled, the first time a crash is caught, a core file is created,
36388 the offending symbol is displayed and the user is presented with the
36389 option to terminate the current session.
36391 @kindex maint cplus first_component
36392 @item maint cplus first_component @var{name}
36393 Print the first C@t{++} class/namespace component of @var{name}.
36395 @kindex maint cplus namespace
36396 @item maint cplus namespace
36397 Print the list of possible C@t{++} namespaces.
36399 @kindex maint deprecate
36400 @kindex maint undeprecate
36401 @cindex deprecated commands
36402 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36403 @itemx maint undeprecate @var{command}
36404 Deprecate or undeprecate the named @var{command}. Deprecated commands
36405 cause @value{GDBN} to issue a warning when you use them. The optional
36406 argument @var{replacement} says which newer command should be used in
36407 favor of the deprecated one; if it is given, @value{GDBN} will mention
36408 the replacement as part of the warning.
36410 @kindex maint dump-me
36411 @item maint dump-me
36412 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36413 Cause a fatal signal in the debugger and force it to dump its core.
36414 This is supported only on systems which support aborting a program
36415 with the @code{SIGQUIT} signal.
36417 @kindex maint internal-error
36418 @kindex maint internal-warning
36419 @kindex maint demangler-warning
36420 @cindex demangler crashes
36421 @item maint internal-error @r{[}@var{message-text}@r{]}
36422 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36423 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36425 Cause @value{GDBN} to call the internal function @code{internal_error},
36426 @code{internal_warning} or @code{demangler_warning} and hence behave
36427 as though an internal problem has been detected. In addition to
36428 reporting the internal problem, these functions give the user the
36429 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36430 and @code{internal_warning}) create a core file of the current
36431 @value{GDBN} session.
36433 These commands take an optional parameter @var{message-text} that is
36434 used as the text of the error or warning message.
36436 Here's an example of using @code{internal-error}:
36439 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36440 @dots{}/maint.c:121: internal-error: testing, 1, 2
36441 A problem internal to GDB has been detected. Further
36442 debugging may prove unreliable.
36443 Quit this debugging session? (y or n) @kbd{n}
36444 Create a core file? (y or n) @kbd{n}
36448 @cindex @value{GDBN} internal error
36449 @cindex internal errors, control of @value{GDBN} behavior
36450 @cindex demangler crashes
36452 @kindex maint set internal-error
36453 @kindex maint show internal-error
36454 @kindex maint set internal-warning
36455 @kindex maint show internal-warning
36456 @kindex maint set demangler-warning
36457 @kindex maint show demangler-warning
36458 @item maint set internal-error @var{action} [ask|yes|no]
36459 @itemx maint show internal-error @var{action}
36460 @itemx maint set internal-warning @var{action} [ask|yes|no]
36461 @itemx maint show internal-warning @var{action}
36462 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36463 @itemx maint show demangler-warning @var{action}
36464 When @value{GDBN} reports an internal problem (error or warning) it
36465 gives the user the opportunity to both quit @value{GDBN} and create a
36466 core file of the current @value{GDBN} session. These commands let you
36467 override the default behaviour for each particular @var{action},
36468 described in the table below.
36472 You can specify that @value{GDBN} should always (yes) or never (no)
36473 quit. The default is to ask the user what to do.
36476 You can specify that @value{GDBN} should always (yes) or never (no)
36477 create a core file. The default is to ask the user what to do. Note
36478 that there is no @code{corefile} option for @code{demangler-warning}:
36479 demangler warnings always create a core file and this cannot be
36483 @kindex maint packet
36484 @item maint packet @var{text}
36485 If @value{GDBN} is talking to an inferior via the serial protocol,
36486 then this command sends the string @var{text} to the inferior, and
36487 displays the response packet. @value{GDBN} supplies the initial
36488 @samp{$} character, the terminating @samp{#} character, and the
36491 @kindex maint print architecture
36492 @item maint print architecture @r{[}@var{file}@r{]}
36493 Print the entire architecture configuration. The optional argument
36494 @var{file} names the file where the output goes.
36496 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36497 @item maint print c-tdesc
36498 Print the target description (@pxref{Target Descriptions}) as
36499 a C source file. By default, the target description is for the current
36500 target, but if the optional argument @var{file} is provided, that file
36501 is used to produce the description. The @var{file} should be an XML
36502 document, of the form described in @ref{Target Description Format}.
36503 The created source file is built into @value{GDBN} when @value{GDBN} is
36504 built again. This command is used by developers after they add or
36505 modify XML target descriptions.
36507 @kindex maint check xml-descriptions
36508 @item maint check xml-descriptions @var{dir}
36509 Check that the target descriptions dynamically created by @value{GDBN}
36510 equal the descriptions created from XML files found in @var{dir}.
36512 @anchor{maint check libthread-db}
36513 @kindex maint check libthread-db
36514 @item maint check libthread-db
36515 Run integrity checks on the current inferior's thread debugging
36516 library. This exercises all @code{libthread_db} functionality used by
36517 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36518 @code{proc_service} functions provided by @value{GDBN} that
36519 @code{libthread_db} uses. Note that parts of the test may be skipped
36520 on some platforms when debugging core files.
36522 @kindex maint print dummy-frames
36523 @item maint print dummy-frames
36524 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36527 (@value{GDBP}) @kbd{b add}
36529 (@value{GDBP}) @kbd{print add(2,3)}
36530 Breakpoint 2, add (a=2, b=3) at @dots{}
36532 The program being debugged stopped while in a function called from GDB.
36534 (@value{GDBP}) @kbd{maint print dummy-frames}
36535 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36539 Takes an optional file parameter.
36541 @kindex maint print registers
36542 @kindex maint print raw-registers
36543 @kindex maint print cooked-registers
36544 @kindex maint print register-groups
36545 @kindex maint print remote-registers
36546 @item maint print registers @r{[}@var{file}@r{]}
36547 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36548 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36549 @itemx maint print register-groups @r{[}@var{file}@r{]}
36550 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36551 Print @value{GDBN}'s internal register data structures.
36553 The command @code{maint print raw-registers} includes the contents of
36554 the raw register cache; the command @code{maint print
36555 cooked-registers} includes the (cooked) value of all registers,
36556 including registers which aren't available on the target nor visible
36557 to user; the command @code{maint print register-groups} includes the
36558 groups that each register is a member of; and the command @code{maint
36559 print remote-registers} includes the remote target's register numbers
36560 and offsets in the `G' packets.
36562 These commands take an optional parameter, a file name to which to
36563 write the information.
36565 @kindex maint print reggroups
36566 @item maint print reggroups @r{[}@var{file}@r{]}
36567 Print @value{GDBN}'s internal register group data structures. The
36568 optional argument @var{file} tells to what file to write the
36571 The register groups info looks like this:
36574 (@value{GDBP}) @kbd{maint print reggroups}
36587 This command forces @value{GDBN} to flush its internal register cache.
36589 @kindex maint print objfiles
36590 @cindex info for known object files
36591 @item maint print objfiles @r{[}@var{regexp}@r{]}
36592 Print a dump of all known object files.
36593 If @var{regexp} is specified, only print object files whose names
36594 match @var{regexp}. For each object file, this command prints its name,
36595 address in memory, and all of its psymtabs and symtabs.
36597 @kindex maint print user-registers
36598 @cindex user registers
36599 @item maint print user-registers
36600 List all currently available @dfn{user registers}. User registers
36601 typically provide alternate names for actual hardware registers. They
36602 include the four ``standard'' registers @code{$fp}, @code{$pc},
36603 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36604 registers can be used in expressions in the same way as the canonical
36605 register names, but only the latter are listed by the @code{info
36606 registers} and @code{maint print registers} commands.
36608 @kindex maint print section-scripts
36609 @cindex info for known .debug_gdb_scripts-loaded scripts
36610 @item maint print section-scripts [@var{regexp}]
36611 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36612 If @var{regexp} is specified, only print scripts loaded by object files
36613 matching @var{regexp}.
36614 For each script, this command prints its name as specified in the objfile,
36615 and the full path if known.
36616 @xref{dotdebug_gdb_scripts section}.
36618 @kindex maint print statistics
36619 @cindex bcache statistics
36620 @item maint print statistics
36621 This command prints, for each object file in the program, various data
36622 about that object file followed by the byte cache (@dfn{bcache})
36623 statistics for the object file. The objfile data includes the number
36624 of minimal, partial, full, and stabs symbols, the number of types
36625 defined by the objfile, the number of as yet unexpanded psym tables,
36626 the number of line tables and string tables, and the amount of memory
36627 used by the various tables. The bcache statistics include the counts,
36628 sizes, and counts of duplicates of all and unique objects, max,
36629 average, and median entry size, total memory used and its overhead and
36630 savings, and various measures of the hash table size and chain
36633 @kindex maint print target-stack
36634 @cindex target stack description
36635 @item maint print target-stack
36636 A @dfn{target} is an interface between the debugger and a particular
36637 kind of file or process. Targets can be stacked in @dfn{strata},
36638 so that more than one target can potentially respond to a request.
36639 In particular, memory accesses will walk down the stack of targets
36640 until they find a target that is interested in handling that particular
36643 This command prints a short description of each layer that was pushed on
36644 the @dfn{target stack}, starting from the top layer down to the bottom one.
36646 @kindex maint print type
36647 @cindex type chain of a data type
36648 @item maint print type @var{expr}
36649 Print the type chain for a type specified by @var{expr}. The argument
36650 can be either a type name or a symbol. If it is a symbol, the type of
36651 that symbol is described. The type chain produced by this command is
36652 a recursive definition of the data type as stored in @value{GDBN}'s
36653 data structures, including its flags and contained types.
36655 @kindex maint selftest
36657 @item maint selftest @r{[}@var{filter}@r{]}
36658 Run any self tests that were compiled in to @value{GDBN}. This will
36659 print a message showing how many tests were run, and how many failed.
36660 If a @var{filter} is passed, only the tests with @var{filter} in their
36663 @kindex "maint info selftests"
36665 @item maint info selftests
36666 List the selftests compiled in to @value{GDBN}.
36668 @kindex maint set dwarf always-disassemble
36669 @kindex maint show dwarf always-disassemble
36670 @item maint set dwarf always-disassemble
36671 @item maint show dwarf always-disassemble
36672 Control the behavior of @code{info address} when using DWARF debugging
36675 The default is @code{off}, which means that @value{GDBN} should try to
36676 describe a variable's location in an easily readable format. When
36677 @code{on}, @value{GDBN} will instead display the DWARF location
36678 expression in an assembly-like format. Note that some locations are
36679 too complex for @value{GDBN} to describe simply; in this case you will
36680 always see the disassembly form.
36682 Here is an example of the resulting disassembly:
36685 (gdb) info addr argc
36686 Symbol "argc" is a complex DWARF expression:
36690 For more information on these expressions, see
36691 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36693 @kindex maint set dwarf max-cache-age
36694 @kindex maint show dwarf max-cache-age
36695 @item maint set dwarf max-cache-age
36696 @itemx maint show dwarf max-cache-age
36697 Control the DWARF compilation unit cache.
36699 @cindex DWARF compilation units cache
36700 In object files with inter-compilation-unit references, such as those
36701 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36702 reader needs to frequently refer to previously read compilation units.
36703 This setting controls how long a compilation unit will remain in the
36704 cache if it is not referenced. A higher limit means that cached
36705 compilation units will be stored in memory longer, and more total
36706 memory will be used. Setting it to zero disables caching, which will
36707 slow down @value{GDBN} startup, but reduce memory consumption.
36709 @kindex maint set dwarf unwinders
36710 @kindex maint show dwarf unwinders
36711 @item maint set dwarf unwinders
36712 @itemx maint show dwarf unwinders
36713 Control use of the DWARF frame unwinders.
36715 @cindex DWARF frame unwinders
36716 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36717 frame unwinders to build the backtrace. Many of these targets will
36718 also have a second mechanism for building the backtrace for use in
36719 cases where DWARF information is not available, this second mechanism
36720 is often an analysis of a function's prologue.
36722 In order to extend testing coverage of the second level stack
36723 unwinding mechanisms it is helpful to be able to disable the DWARF
36724 stack unwinders, this can be done with this switch.
36726 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36727 advisable, there are cases that are better handled through DWARF than
36728 prologue analysis, and the debug experience is likely to be better
36729 with the DWARF frame unwinders enabled.
36731 If DWARF frame unwinders are not supported for a particular target
36732 architecture, then enabling this flag does not cause them to be used.
36733 @kindex maint set profile
36734 @kindex maint show profile
36735 @cindex profiling GDB
36736 @item maint set profile
36737 @itemx maint show profile
36738 Control profiling of @value{GDBN}.
36740 Profiling will be disabled until you use the @samp{maint set profile}
36741 command to enable it. When you enable profiling, the system will begin
36742 collecting timing and execution count data; when you disable profiling or
36743 exit @value{GDBN}, the results will be written to a log file. Remember that
36744 if you use profiling, @value{GDBN} will overwrite the profiling log file
36745 (often called @file{gmon.out}). If you have a record of important profiling
36746 data in a @file{gmon.out} file, be sure to move it to a safe location.
36748 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36749 compiled with the @samp{-pg} compiler option.
36751 @kindex maint set show-debug-regs
36752 @kindex maint show show-debug-regs
36753 @cindex hardware debug registers
36754 @item maint set show-debug-regs
36755 @itemx maint show show-debug-regs
36756 Control whether to show variables that mirror the hardware debug
36757 registers. Use @code{on} to enable, @code{off} to disable. If
36758 enabled, the debug registers values are shown when @value{GDBN} inserts or
36759 removes a hardware breakpoint or watchpoint, and when the inferior
36760 triggers a hardware-assisted breakpoint or watchpoint.
36762 @kindex maint set show-all-tib
36763 @kindex maint show show-all-tib
36764 @item maint set show-all-tib
36765 @itemx maint show show-all-tib
36766 Control whether to show all non zero areas within a 1k block starting
36767 at thread local base, when using the @samp{info w32 thread-information-block}
36770 @kindex maint set target-async
36771 @kindex maint show target-async
36772 @item maint set target-async
36773 @itemx maint show target-async
36774 This controls whether @value{GDBN} targets operate in synchronous or
36775 asynchronous mode (@pxref{Background Execution}). Normally the
36776 default is asynchronous, if it is available; but this can be changed
36777 to more easily debug problems occurring only in synchronous mode.
36779 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36780 @kindex maint show target-non-stop
36781 @item maint set target-non-stop
36782 @itemx maint show target-non-stop
36784 This controls whether @value{GDBN} targets always operate in non-stop
36785 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36786 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36787 if supported by the target.
36790 @item maint set target-non-stop auto
36791 This is the default mode. @value{GDBN} controls the target in
36792 non-stop mode if the target supports it.
36794 @item maint set target-non-stop on
36795 @value{GDBN} controls the target in non-stop mode even if the target
36796 does not indicate support.
36798 @item maint set target-non-stop off
36799 @value{GDBN} does not control the target in non-stop mode even if the
36800 target supports it.
36803 @kindex maint set per-command
36804 @kindex maint show per-command
36805 @item maint set per-command
36806 @itemx maint show per-command
36807 @cindex resources used by commands
36809 @value{GDBN} can display the resources used by each command.
36810 This is useful in debugging performance problems.
36813 @item maint set per-command space [on|off]
36814 @itemx maint show per-command space
36815 Enable or disable the printing of the memory used by GDB for each command.
36816 If enabled, @value{GDBN} will display how much memory each command
36817 took, following the command's own output.
36818 This can also be requested by invoking @value{GDBN} with the
36819 @option{--statistics} command-line switch (@pxref{Mode Options}).
36821 @item maint set per-command time [on|off]
36822 @itemx maint show per-command time
36823 Enable or disable the printing of the execution time of @value{GDBN}
36825 If enabled, @value{GDBN} will display how much time it
36826 took to execute each command, following the command's own output.
36827 Both CPU time and wallclock time are printed.
36828 Printing both is useful when trying to determine whether the cost is
36829 CPU or, e.g., disk/network latency.
36830 Note that the CPU time printed is for @value{GDBN} only, it does not include
36831 the execution time of the inferior because there's no mechanism currently
36832 to compute how much time was spent by @value{GDBN} and how much time was
36833 spent by the program been debugged.
36834 This can also be requested by invoking @value{GDBN} with the
36835 @option{--statistics} command-line switch (@pxref{Mode Options}).
36837 @item maint set per-command symtab [on|off]
36838 @itemx maint show per-command symtab
36839 Enable or disable the printing of basic symbol table statistics
36841 If enabled, @value{GDBN} will display the following information:
36845 number of symbol tables
36847 number of primary symbol tables
36849 number of blocks in the blockvector
36853 @kindex maint set check-libthread-db
36854 @kindex maint show check-libthread-db
36855 @item maint set check-libthread-db [on|off]
36856 @itemx maint show check-libthread-db
36857 Control whether @value{GDBN} should run integrity checks on inferior
36858 specific thread debugging libraries as they are loaded. The default
36859 is not to perform such checks. If any check fails @value{GDBN} will
36860 unload the library and continue searching for a suitable candidate as
36861 described in @ref{set libthread-db-search-path}. For more information
36862 about the tests, see @ref{maint check libthread-db}.
36864 @kindex maint space
36865 @cindex memory used by commands
36866 @item maint space @var{value}
36867 An alias for @code{maint set per-command space}.
36868 A non-zero value enables it, zero disables it.
36871 @cindex time of command execution
36872 @item maint time @var{value}
36873 An alias for @code{maint set per-command time}.
36874 A non-zero value enables it, zero disables it.
36876 @kindex maint translate-address
36877 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36878 Find the symbol stored at the location specified by the address
36879 @var{addr} and an optional section name @var{section}. If found,
36880 @value{GDBN} prints the name of the closest symbol and an offset from
36881 the symbol's location to the specified address. This is similar to
36882 the @code{info address} command (@pxref{Symbols}), except that this
36883 command also allows to find symbols in other sections.
36885 If section was not specified, the section in which the symbol was found
36886 is also printed. For dynamically linked executables, the name of
36887 executable or shared library containing the symbol is printed as well.
36891 The following command is useful for non-interactive invocations of
36892 @value{GDBN}, such as in the test suite.
36895 @item set watchdog @var{nsec}
36896 @kindex set watchdog
36897 @cindex watchdog timer
36898 @cindex timeout for commands
36899 Set the maximum number of seconds @value{GDBN} will wait for the
36900 target operation to finish. If this time expires, @value{GDBN}
36901 reports and error and the command is aborted.
36903 @item show watchdog
36904 Show the current setting of the target wait timeout.
36907 @node Remote Protocol
36908 @appendix @value{GDBN} Remote Serial Protocol
36913 * Stop Reply Packets::
36914 * General Query Packets::
36915 * Architecture-Specific Protocol Details::
36916 * Tracepoint Packets::
36917 * Host I/O Packets::
36919 * Notification Packets::
36920 * Remote Non-Stop::
36921 * Packet Acknowledgment::
36923 * File-I/O Remote Protocol Extension::
36924 * Library List Format::
36925 * Library List Format for SVR4 Targets::
36926 * Memory Map Format::
36927 * Thread List Format::
36928 * Traceframe Info Format::
36929 * Branch Trace Format::
36930 * Branch Trace Configuration Format::
36936 There may be occasions when you need to know something about the
36937 protocol---for example, if there is only one serial port to your target
36938 machine, you might want your program to do something special if it
36939 recognizes a packet meant for @value{GDBN}.
36941 In the examples below, @samp{->} and @samp{<-} are used to indicate
36942 transmitted and received data, respectively.
36944 @cindex protocol, @value{GDBN} remote serial
36945 @cindex serial protocol, @value{GDBN} remote
36946 @cindex remote serial protocol
36947 All @value{GDBN} commands and responses (other than acknowledgments
36948 and notifications, see @ref{Notification Packets}) are sent as a
36949 @var{packet}. A @var{packet} is introduced with the character
36950 @samp{$}, the actual @var{packet-data}, and the terminating character
36951 @samp{#} followed by a two-digit @var{checksum}:
36954 @code{$}@var{packet-data}@code{#}@var{checksum}
36958 @cindex checksum, for @value{GDBN} remote
36960 The two-digit @var{checksum} is computed as the modulo 256 sum of all
36961 characters between the leading @samp{$} and the trailing @samp{#} (an
36962 eight bit unsigned checksum).
36964 Implementors should note that prior to @value{GDBN} 5.0 the protocol
36965 specification also included an optional two-digit @var{sequence-id}:
36968 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
36971 @cindex sequence-id, for @value{GDBN} remote
36973 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
36974 has never output @var{sequence-id}s. Stubs that handle packets added
36975 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
36977 When either the host or the target machine receives a packet, the first
36978 response expected is an acknowledgment: either @samp{+} (to indicate
36979 the package was received correctly) or @samp{-} (to request
36983 -> @code{$}@var{packet-data}@code{#}@var{checksum}
36988 The @samp{+}/@samp{-} acknowledgments can be disabled
36989 once a connection is established.
36990 @xref{Packet Acknowledgment}, for details.
36992 The host (@value{GDBN}) sends @var{command}s, and the target (the
36993 debugging stub incorporated in your program) sends a @var{response}. In
36994 the case of step and continue @var{command}s, the response is only sent
36995 when the operation has completed, and the target has again stopped all
36996 threads in all attached processes. This is the default all-stop mode
36997 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
36998 execution mode; see @ref{Remote Non-Stop}, for details.
37000 @var{packet-data} consists of a sequence of characters with the
37001 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37004 @cindex remote protocol, field separator
37005 Fields within the packet should be separated using @samp{,} @samp{;} or
37006 @samp{:}. Except where otherwise noted all numbers are represented in
37007 @sc{hex} with leading zeros suppressed.
37009 Implementors should note that prior to @value{GDBN} 5.0, the character
37010 @samp{:} could not appear as the third character in a packet (as it
37011 would potentially conflict with the @var{sequence-id}).
37013 @cindex remote protocol, binary data
37014 @anchor{Binary Data}
37015 Binary data in most packets is encoded either as two hexadecimal
37016 digits per byte of binary data. This allowed the traditional remote
37017 protocol to work over connections which were only seven-bit clean.
37018 Some packets designed more recently assume an eight-bit clean
37019 connection, and use a more efficient encoding to send and receive
37022 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37023 as an escape character. Any escaped byte is transmitted as the escape
37024 character followed by the original character XORed with @code{0x20}.
37025 For example, the byte @code{0x7d} would be transmitted as the two
37026 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37027 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37028 @samp{@}}) must always be escaped. Responses sent by the stub
37029 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37030 is not interpreted as the start of a run-length encoded sequence
37033 Response @var{data} can be run-length encoded to save space.
37034 Run-length encoding replaces runs of identical characters with one
37035 instance of the repeated character, followed by a @samp{*} and a
37036 repeat count. The repeat count is itself sent encoded, to avoid
37037 binary characters in @var{data}: a value of @var{n} is sent as
37038 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37039 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37040 code 32) for a repeat count of 3. (This is because run-length
37041 encoding starts to win for counts 3 or more.) Thus, for example,
37042 @samp{0* } is a run-length encoding of ``0000'': the space character
37043 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37046 The printable characters @samp{#} and @samp{$} or with a numeric value
37047 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37048 seven repeats (@samp{$}) can be expanded using a repeat count of only
37049 five (@samp{"}). For example, @samp{00000000} can be encoded as
37052 The error response returned for some packets includes a two character
37053 error number. That number is not well defined.
37055 @cindex empty response, for unsupported packets
37056 For any @var{command} not supported by the stub, an empty response
37057 (@samp{$#00}) should be returned. That way it is possible to extend the
37058 protocol. A newer @value{GDBN} can tell if a packet is supported based
37061 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37062 commands for register access, and the @samp{m} and @samp{M} commands
37063 for memory access. Stubs that only control single-threaded targets
37064 can implement run control with the @samp{c} (continue), and @samp{s}
37065 (step) commands. Stubs that support multi-threading targets should
37066 support the @samp{vCont} command. All other commands are optional.
37071 The following table provides a complete list of all currently defined
37072 @var{command}s and their corresponding response @var{data}.
37073 @xref{File-I/O Remote Protocol Extension}, for details about the File
37074 I/O extension of the remote protocol.
37076 Each packet's description has a template showing the packet's overall
37077 syntax, followed by an explanation of the packet's meaning. We
37078 include spaces in some of the templates for clarity; these are not
37079 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37080 separate its components. For example, a template like @samp{foo
37081 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37082 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37083 @var{baz}. @value{GDBN} does not transmit a space character between the
37084 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37087 @cindex @var{thread-id}, in remote protocol
37088 @anchor{thread-id syntax}
37089 Several packets and replies include a @var{thread-id} field to identify
37090 a thread. Normally these are positive numbers with a target-specific
37091 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37092 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37095 In addition, the remote protocol supports a multiprocess feature in
37096 which the @var{thread-id} syntax is extended to optionally include both
37097 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37098 The @var{pid} (process) and @var{tid} (thread) components each have the
37099 format described above: a positive number with target-specific
37100 interpretation formatted as a big-endian hex string, literal @samp{-1}
37101 to indicate all processes or threads (respectively), or @samp{0} to
37102 indicate an arbitrary process or thread. Specifying just a process, as
37103 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37104 error to specify all processes but a specific thread, such as
37105 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37106 for those packets and replies explicitly documented to include a process
37107 ID, rather than a @var{thread-id}.
37109 The multiprocess @var{thread-id} syntax extensions are only used if both
37110 @value{GDBN} and the stub report support for the @samp{multiprocess}
37111 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37114 Note that all packet forms beginning with an upper- or lower-case
37115 letter, other than those described here, are reserved for future use.
37117 Here are the packet descriptions.
37122 @cindex @samp{!} packet
37123 @anchor{extended mode}
37124 Enable extended mode. In extended mode, the remote server is made
37125 persistent. The @samp{R} packet is used to restart the program being
37131 The remote target both supports and has enabled extended mode.
37135 @cindex @samp{?} packet
37137 Indicate the reason the target halted. The reply is the same as for
37138 step and continue. This packet has a special interpretation when the
37139 target is in non-stop mode; see @ref{Remote Non-Stop}.
37142 @xref{Stop Reply Packets}, for the reply specifications.
37144 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37145 @cindex @samp{A} packet
37146 Initialized @code{argv[]} array passed into program. @var{arglen}
37147 specifies the number of bytes in the hex encoded byte stream
37148 @var{arg}. See @code{gdbserver} for more details.
37153 The arguments were set.
37159 @cindex @samp{b} packet
37160 (Don't use this packet; its behavior is not well-defined.)
37161 Change the serial line speed to @var{baud}.
37163 JTC: @emph{When does the transport layer state change? When it's
37164 received, or after the ACK is transmitted. In either case, there are
37165 problems if the command or the acknowledgment packet is dropped.}
37167 Stan: @emph{If people really wanted to add something like this, and get
37168 it working for the first time, they ought to modify ser-unix.c to send
37169 some kind of out-of-band message to a specially-setup stub and have the
37170 switch happen "in between" packets, so that from remote protocol's point
37171 of view, nothing actually happened.}
37173 @item B @var{addr},@var{mode}
37174 @cindex @samp{B} packet
37175 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37176 breakpoint at @var{addr}.
37178 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37179 (@pxref{insert breakpoint or watchpoint packet}).
37181 @cindex @samp{bc} packet
37184 Backward continue. Execute the target system in reverse. No parameter.
37185 @xref{Reverse Execution}, for more information.
37188 @xref{Stop Reply Packets}, for the reply specifications.
37190 @cindex @samp{bs} packet
37193 Backward single step. Execute one instruction in reverse. No parameter.
37194 @xref{Reverse Execution}, for more information.
37197 @xref{Stop Reply Packets}, for the reply specifications.
37199 @item c @r{[}@var{addr}@r{]}
37200 @cindex @samp{c} packet
37201 Continue at @var{addr}, which is the address to resume. If @var{addr}
37202 is omitted, resume at current address.
37204 This packet is deprecated for multi-threading support. @xref{vCont
37208 @xref{Stop Reply Packets}, for the reply specifications.
37210 @item C @var{sig}@r{[};@var{addr}@r{]}
37211 @cindex @samp{C} packet
37212 Continue with signal @var{sig} (hex signal number). If
37213 @samp{;@var{addr}} is omitted, resume at same address.
37215 This packet is deprecated for multi-threading support. @xref{vCont
37219 @xref{Stop Reply Packets}, for the reply specifications.
37222 @cindex @samp{d} packet
37225 Don't use this packet; instead, define a general set packet
37226 (@pxref{General Query Packets}).
37230 @cindex @samp{D} packet
37231 The first form of the packet is used to detach @value{GDBN} from the
37232 remote system. It is sent to the remote target
37233 before @value{GDBN} disconnects via the @code{detach} command.
37235 The second form, including a process ID, is used when multiprocess
37236 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37237 detach only a specific process. The @var{pid} is specified as a
37238 big-endian hex string.
37248 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37249 @cindex @samp{F} packet
37250 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37251 This is part of the File-I/O protocol extension. @xref{File-I/O
37252 Remote Protocol Extension}, for the specification.
37255 @anchor{read registers packet}
37256 @cindex @samp{g} packet
37257 Read general registers.
37261 @item @var{XX@dots{}}
37262 Each byte of register data is described by two hex digits. The bytes
37263 with the register are transmitted in target byte order. The size of
37264 each register and their position within the @samp{g} packet are
37265 determined by the @value{GDBN} internal gdbarch functions
37266 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37268 When reading registers from a trace frame (@pxref{Analyze Collected
37269 Data,,Using the Collected Data}), the stub may also return a string of
37270 literal @samp{x}'s in place of the register data digits, to indicate
37271 that the corresponding register has not been collected, thus its value
37272 is unavailable. For example, for an architecture with 4 registers of
37273 4 bytes each, the following reply indicates to @value{GDBN} that
37274 registers 0 and 2 have not been collected, while registers 1 and 3
37275 have been collected, and both have zero value:
37279 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37286 @item G @var{XX@dots{}}
37287 @cindex @samp{G} packet
37288 Write general registers. @xref{read registers packet}, for a
37289 description of the @var{XX@dots{}} data.
37299 @item H @var{op} @var{thread-id}
37300 @cindex @samp{H} packet
37301 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37302 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37303 should be @samp{c} for step and continue operations (note that this
37304 is deprecated, supporting the @samp{vCont} command is a better
37305 option), and @samp{g} for other operations. The thread designator
37306 @var{thread-id} has the format and interpretation described in
37307 @ref{thread-id syntax}.
37318 @c 'H': How restrictive (or permissive) is the thread model. If a
37319 @c thread is selected and stopped, are other threads allowed
37320 @c to continue to execute? As I mentioned above, I think the
37321 @c semantics of each command when a thread is selected must be
37322 @c described. For example:
37324 @c 'g': If the stub supports threads and a specific thread is
37325 @c selected, returns the register block from that thread;
37326 @c otherwise returns current registers.
37328 @c 'G' If the stub supports threads and a specific thread is
37329 @c selected, sets the registers of the register block of
37330 @c that thread; otherwise sets current registers.
37332 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37333 @anchor{cycle step packet}
37334 @cindex @samp{i} packet
37335 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37336 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37337 step starting at that address.
37340 @cindex @samp{I} packet
37341 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37345 @cindex @samp{k} packet
37348 The exact effect of this packet is not specified.
37350 For a bare-metal target, it may power cycle or reset the target
37351 system. For that reason, the @samp{k} packet has no reply.
37353 For a single-process target, it may kill that process if possible.
37355 A multiple-process target may choose to kill just one process, or all
37356 that are under @value{GDBN}'s control. For more precise control, use
37357 the vKill packet (@pxref{vKill packet}).
37359 If the target system immediately closes the connection in response to
37360 @samp{k}, @value{GDBN} does not consider the lack of packet
37361 acknowledgment to be an error, and assumes the kill was successful.
37363 If connected using @kbd{target extended-remote}, and the target does
37364 not close the connection in response to a kill request, @value{GDBN}
37365 probes the target state as if a new connection was opened
37366 (@pxref{? packet}).
37368 @item m @var{addr},@var{length}
37369 @cindex @samp{m} packet
37370 Read @var{length} addressable memory units starting at address @var{addr}
37371 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37372 any particular boundary.
37374 The stub need not use any particular size or alignment when gathering
37375 data from memory for the response; even if @var{addr} is word-aligned
37376 and @var{length} is a multiple of the word size, the stub is free to
37377 use byte accesses, or not. For this reason, this packet may not be
37378 suitable for accessing memory-mapped I/O devices.
37379 @cindex alignment of remote memory accesses
37380 @cindex size of remote memory accesses
37381 @cindex memory, alignment and size of remote accesses
37385 @item @var{XX@dots{}}
37386 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37387 The reply may contain fewer addressable memory units than requested if the
37388 server was able to read only part of the region of memory.
37393 @item M @var{addr},@var{length}:@var{XX@dots{}}
37394 @cindex @samp{M} packet
37395 Write @var{length} addressable memory units starting at address @var{addr}
37396 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37397 byte is transmitted as a two-digit hexadecimal number.
37404 for an error (this includes the case where only part of the data was
37409 @cindex @samp{p} packet
37410 Read the value of register @var{n}; @var{n} is in hex.
37411 @xref{read registers packet}, for a description of how the returned
37412 register value is encoded.
37416 @item @var{XX@dots{}}
37417 the register's value
37421 Indicating an unrecognized @var{query}.
37424 @item P @var{n@dots{}}=@var{r@dots{}}
37425 @anchor{write register packet}
37426 @cindex @samp{P} packet
37427 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37428 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37429 digits for each byte in the register (target byte order).
37439 @item q @var{name} @var{params}@dots{}
37440 @itemx Q @var{name} @var{params}@dots{}
37441 @cindex @samp{q} packet
37442 @cindex @samp{Q} packet
37443 General query (@samp{q}) and set (@samp{Q}). These packets are
37444 described fully in @ref{General Query Packets}.
37447 @cindex @samp{r} packet
37448 Reset the entire system.
37450 Don't use this packet; use the @samp{R} packet instead.
37453 @cindex @samp{R} packet
37454 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37455 This packet is only available in extended mode (@pxref{extended mode}).
37457 The @samp{R} packet has no reply.
37459 @item s @r{[}@var{addr}@r{]}
37460 @cindex @samp{s} packet
37461 Single step, resuming at @var{addr}. If
37462 @var{addr} is omitted, resume at same address.
37464 This packet is deprecated for multi-threading support. @xref{vCont
37468 @xref{Stop Reply Packets}, for the reply specifications.
37470 @item S @var{sig}@r{[};@var{addr}@r{]}
37471 @anchor{step with signal packet}
37472 @cindex @samp{S} packet
37473 Step with signal. This is analogous to the @samp{C} packet, but
37474 requests a single-step, rather than a normal resumption of execution.
37476 This packet is deprecated for multi-threading support. @xref{vCont
37480 @xref{Stop Reply Packets}, for the reply specifications.
37482 @item t @var{addr}:@var{PP},@var{MM}
37483 @cindex @samp{t} packet
37484 Search backwards starting at address @var{addr} for a match with pattern
37485 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37486 There must be at least 3 digits in @var{addr}.
37488 @item T @var{thread-id}
37489 @cindex @samp{T} packet
37490 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37495 thread is still alive
37501 Packets starting with @samp{v} are identified by a multi-letter name,
37502 up to the first @samp{;} or @samp{?} (or the end of the packet).
37504 @item vAttach;@var{pid}
37505 @cindex @samp{vAttach} packet
37506 Attach to a new process with the specified process ID @var{pid}.
37507 The process ID is a
37508 hexadecimal integer identifying the process. In all-stop mode, all
37509 threads in the attached process are stopped; in non-stop mode, it may be
37510 attached without being stopped if that is supported by the target.
37512 @c In non-stop mode, on a successful vAttach, the stub should set the
37513 @c current thread to a thread of the newly-attached process. After
37514 @c attaching, GDB queries for the attached process's thread ID with qC.
37515 @c Also note that, from a user perspective, whether or not the
37516 @c target is stopped on attach in non-stop mode depends on whether you
37517 @c use the foreground or background version of the attach command, not
37518 @c on what vAttach does; GDB does the right thing with respect to either
37519 @c stopping or restarting threads.
37521 This packet is only available in extended mode (@pxref{extended mode}).
37527 @item @r{Any stop packet}
37528 for success in all-stop mode (@pxref{Stop Reply Packets})
37530 for success in non-stop mode (@pxref{Remote Non-Stop})
37533 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37534 @cindex @samp{vCont} packet
37535 @anchor{vCont packet}
37536 Resume the inferior, specifying different actions for each thread.
37538 For each inferior thread, the leftmost action with a matching
37539 @var{thread-id} is applied. Threads that don't match any action
37540 remain in their current state. Thread IDs are specified using the
37541 syntax described in @ref{thread-id syntax}. If multiprocess
37542 extensions (@pxref{multiprocess extensions}) are supported, actions
37543 can be specified to match all threads in a process by using the
37544 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37545 @var{thread-id} matches all threads. Specifying no actions is an
37548 Currently supported actions are:
37554 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37558 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37561 @item r @var{start},@var{end}
37562 Step once, and then keep stepping as long as the thread stops at
37563 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37564 The remote stub reports a stop reply when either the thread goes out
37565 of the range or is stopped due to an unrelated reason, such as hitting
37566 a breakpoint. @xref{range stepping}.
37568 If the range is empty (@var{start} == @var{end}), then the action
37569 becomes equivalent to the @samp{s} action. In other words,
37570 single-step once, and report the stop (even if the stepped instruction
37571 jumps to @var{start}).
37573 (A stop reply may be sent at any point even if the PC is still within
37574 the stepping range; for example, it is valid to implement this packet
37575 in a degenerate way as a single instruction step operation.)
37579 The optional argument @var{addr} normally associated with the
37580 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37581 not supported in @samp{vCont}.
37583 The @samp{t} action is only relevant in non-stop mode
37584 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37585 A stop reply should be generated for any affected thread not already stopped.
37586 When a thread is stopped by means of a @samp{t} action,
37587 the corresponding stop reply should indicate that the thread has stopped with
37588 signal @samp{0}, regardless of whether the target uses some other signal
37589 as an implementation detail.
37591 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37592 @samp{r} actions for threads that are already running. Conversely,
37593 the server must ignore @samp{t} actions for threads that are already
37596 @emph{Note:} In non-stop mode, a thread is considered running until
37597 @value{GDBN} acknowleges an asynchronous stop notification for it with
37598 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37600 The stub must support @samp{vCont} if it reports support for
37601 multiprocess extensions (@pxref{multiprocess extensions}).
37604 @xref{Stop Reply Packets}, for the reply specifications.
37607 @cindex @samp{vCont?} packet
37608 Request a list of actions supported by the @samp{vCont} packet.
37612 @item vCont@r{[};@var{action}@dots{}@r{]}
37613 The @samp{vCont} packet is supported. Each @var{action} is a supported
37614 command in the @samp{vCont} packet.
37616 The @samp{vCont} packet is not supported.
37619 @anchor{vCtrlC packet}
37621 @cindex @samp{vCtrlC} packet
37622 Interrupt remote target as if a control-C was pressed on the remote
37623 terminal. This is the equivalent to reacting to the @code{^C}
37624 (@samp{\003}, the control-C character) character in all-stop mode
37625 while the target is running, except this works in non-stop mode.
37626 @xref{interrupting remote targets}, for more info on the all-stop
37637 @item vFile:@var{operation}:@var{parameter}@dots{}
37638 @cindex @samp{vFile} packet
37639 Perform a file operation on the target system. For details,
37640 see @ref{Host I/O Packets}.
37642 @item vFlashErase:@var{addr},@var{length}
37643 @cindex @samp{vFlashErase} packet
37644 Direct the stub to erase @var{length} bytes of flash starting at
37645 @var{addr}. The region may enclose any number of flash blocks, but
37646 its start and end must fall on block boundaries, as indicated by the
37647 flash block size appearing in the memory map (@pxref{Memory Map
37648 Format}). @value{GDBN} groups flash memory programming operations
37649 together, and sends a @samp{vFlashDone} request after each group; the
37650 stub is allowed to delay erase operation until the @samp{vFlashDone}
37651 packet is received.
37661 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37662 @cindex @samp{vFlashWrite} packet
37663 Direct the stub to write data to flash address @var{addr}. The data
37664 is passed in binary form using the same encoding as for the @samp{X}
37665 packet (@pxref{Binary Data}). The memory ranges specified by
37666 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37667 not overlap, and must appear in order of increasing addresses
37668 (although @samp{vFlashErase} packets for higher addresses may already
37669 have been received; the ordering is guaranteed only between
37670 @samp{vFlashWrite} packets). If a packet writes to an address that was
37671 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37672 target-specific method, the results are unpredictable.
37680 for vFlashWrite addressing non-flash memory
37686 @cindex @samp{vFlashDone} packet
37687 Indicate to the stub that flash programming operation is finished.
37688 The stub is permitted to delay or batch the effects of a group of
37689 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37690 @samp{vFlashDone} packet is received. The contents of the affected
37691 regions of flash memory are unpredictable until the @samp{vFlashDone}
37692 request is completed.
37694 @item vKill;@var{pid}
37695 @cindex @samp{vKill} packet
37696 @anchor{vKill packet}
37697 Kill the process with the specified process ID @var{pid}, which is a
37698 hexadecimal integer identifying the process. This packet is used in
37699 preference to @samp{k} when multiprocess protocol extensions are
37700 supported; see @ref{multiprocess extensions}.
37710 @item vMustReplyEmpty
37711 @cindex @samp{vMustReplyEmpty} packet
37712 The correct reply to an unknown @samp{v} packet is to return the empty
37713 string, however, some older versions of @command{gdbserver} would
37714 incorrectly return @samp{OK} for unknown @samp{v} packets.
37716 The @samp{vMustReplyEmpty} is used as a feature test to check how
37717 @command{gdbserver} handles unknown packets, it is important that this
37718 packet be handled in the same way as other unknown @samp{v} packets.
37719 If this packet is handled differently to other unknown @samp{v}
37720 packets then it is possile that @value{GDBN} may run into problems in
37721 other areas, specifically around use of @samp{vFile:setfs:}.
37723 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37724 @cindex @samp{vRun} packet
37725 Run the program @var{filename}, passing it each @var{argument} on its
37726 command line. The file and arguments are hex-encoded strings. If
37727 @var{filename} is an empty string, the stub may use a default program
37728 (e.g.@: the last program run). The program is created in the stopped
37731 @c FIXME: What about non-stop mode?
37733 This packet is only available in extended mode (@pxref{extended mode}).
37739 @item @r{Any stop packet}
37740 for success (@pxref{Stop Reply Packets})
37744 @cindex @samp{vStopped} packet
37745 @xref{Notification Packets}.
37747 @item X @var{addr},@var{length}:@var{XX@dots{}}
37749 @cindex @samp{X} packet
37750 Write data to memory, where the data is transmitted in binary.
37751 Memory is specified by its address @var{addr} and number of addressable memory
37752 units @var{length} (@pxref{addressable memory unit});
37753 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37763 @item z @var{type},@var{addr},@var{kind}
37764 @itemx Z @var{type},@var{addr},@var{kind}
37765 @anchor{insert breakpoint or watchpoint packet}
37766 @cindex @samp{z} packet
37767 @cindex @samp{Z} packets
37768 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37769 watchpoint starting at address @var{address} of kind @var{kind}.
37771 Each breakpoint and watchpoint packet @var{type} is documented
37774 @emph{Implementation notes: A remote target shall return an empty string
37775 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37776 remote target shall support either both or neither of a given
37777 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37778 avoid potential problems with duplicate packets, the operations should
37779 be implemented in an idempotent way.}
37781 @item z0,@var{addr},@var{kind}
37782 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37783 @cindex @samp{z0} packet
37784 @cindex @samp{Z0} packet
37785 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37786 @var{addr} of type @var{kind}.
37788 A software breakpoint is implemented by replacing the instruction at
37789 @var{addr} with a software breakpoint or trap instruction. The
37790 @var{kind} is target-specific and typically indicates the size of the
37791 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37792 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37793 architectures have additional meanings for @var{kind}
37794 (@pxref{Architecture-Specific Protocol Details}); if no
37795 architecture-specific value is being used, it should be @samp{0}.
37796 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37797 conditional expressions in bytecode form that should be evaluated on
37798 the target's side. These are the conditions that should be taken into
37799 consideration when deciding if the breakpoint trigger should be
37800 reported back to @value{GDBN}.
37802 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37803 for how to best report a software breakpoint event to @value{GDBN}.
37805 The @var{cond_list} parameter is comprised of a series of expressions,
37806 concatenated without separators. Each expression has the following form:
37810 @item X @var{len},@var{expr}
37811 @var{len} is the length of the bytecode expression and @var{expr} is the
37812 actual conditional expression in bytecode form.
37816 The optional @var{cmd_list} parameter introduces commands that may be
37817 run on the target, rather than being reported back to @value{GDBN}.
37818 The parameter starts with a numeric flag @var{persist}; if the flag is
37819 nonzero, then the breakpoint may remain active and the commands
37820 continue to be run even when @value{GDBN} disconnects from the target.
37821 Following this flag is a series of expressions concatenated with no
37822 separators. Each expression has the following form:
37826 @item X @var{len},@var{expr}
37827 @var{len} is the length of the bytecode expression and @var{expr} is the
37828 actual commands expression in bytecode form.
37832 @emph{Implementation note: It is possible for a target to copy or move
37833 code that contains software breakpoints (e.g., when implementing
37834 overlays). The behavior of this packet, in the presence of such a
37835 target, is not defined.}
37847 @item z1,@var{addr},@var{kind}
37848 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37849 @cindex @samp{z1} packet
37850 @cindex @samp{Z1} packet
37851 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37852 address @var{addr}.
37854 A hardware breakpoint is implemented using a mechanism that is not
37855 dependent on being able to modify the target's memory. The
37856 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37857 same meaning as in @samp{Z0} packets.
37859 @emph{Implementation note: A hardware breakpoint is not affected by code
37872 @item z2,@var{addr},@var{kind}
37873 @itemx Z2,@var{addr},@var{kind}
37874 @cindex @samp{z2} packet
37875 @cindex @samp{Z2} packet
37876 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37877 The number of bytes to watch is specified by @var{kind}.
37889 @item z3,@var{addr},@var{kind}
37890 @itemx Z3,@var{addr},@var{kind}
37891 @cindex @samp{z3} packet
37892 @cindex @samp{Z3} packet
37893 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37894 The number of bytes to watch is specified by @var{kind}.
37906 @item z4,@var{addr},@var{kind}
37907 @itemx Z4,@var{addr},@var{kind}
37908 @cindex @samp{z4} packet
37909 @cindex @samp{Z4} packet
37910 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37911 The number of bytes to watch is specified by @var{kind}.
37925 @node Stop Reply Packets
37926 @section Stop Reply Packets
37927 @cindex stop reply packets
37929 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37930 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37931 receive any of the below as a reply. Except for @samp{?}
37932 and @samp{vStopped}, that reply is only returned
37933 when the target halts. In the below the exact meaning of @dfn{signal
37934 number} is defined by the header @file{include/gdb/signals.h} in the
37935 @value{GDBN} source code.
37937 In non-stop mode, the server will simply reply @samp{OK} to commands
37938 such as @samp{vCont}; any stop will be the subject of a future
37939 notification. @xref{Remote Non-Stop}.
37941 As in the description of request packets, we include spaces in the
37942 reply templates for clarity; these are not part of the reply packet's
37943 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
37949 The program received signal number @var{AA} (a two-digit hexadecimal
37950 number). This is equivalent to a @samp{T} response with no
37951 @var{n}:@var{r} pairs.
37953 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
37954 @cindex @samp{T} packet reply
37955 The program received signal number @var{AA} (a two-digit hexadecimal
37956 number). This is equivalent to an @samp{S} response, except that the
37957 @samp{@var{n}:@var{r}} pairs can carry values of important registers
37958 and other information directly in the stop reply packet, reducing
37959 round-trip latency. Single-step and breakpoint traps are reported
37960 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
37964 If @var{n} is a hexadecimal number, it is a register number, and the
37965 corresponding @var{r} gives that register's value. The data @var{r} is a
37966 series of bytes in target byte order, with each byte given by a
37967 two-digit hex number.
37970 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
37971 the stopped thread, as specified in @ref{thread-id syntax}.
37974 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
37975 the core on which the stop event was detected.
37978 If @var{n} is a recognized @dfn{stop reason}, it describes a more
37979 specific event that stopped the target. The currently defined stop
37980 reasons are listed below. The @var{aa} should be @samp{05}, the trap
37981 signal. At most one stop reason should be present.
37984 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
37985 and go on to the next; this allows us to extend the protocol in the
37989 The currently defined stop reasons are:
37995 The packet indicates a watchpoint hit, and @var{r} is the data address, in
37998 @item syscall_entry
37999 @itemx syscall_return
38000 The packet indicates a syscall entry or return, and @var{r} is the
38001 syscall number, in hex.
38003 @cindex shared library events, remote reply
38005 The packet indicates that the loaded libraries have changed.
38006 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38007 list of loaded libraries. The @var{r} part is ignored.
38009 @cindex replay log events, remote reply
38011 The packet indicates that the target cannot continue replaying
38012 logged execution events, because it has reached the end (or the
38013 beginning when executing backward) of the log. The value of @var{r}
38014 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38015 for more information.
38018 @anchor{swbreak stop reason}
38019 The packet indicates a software breakpoint instruction was executed,
38020 irrespective of whether it was @value{GDBN} that planted the
38021 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
38022 part must be left empty.
38024 On some architectures, such as x86, at the architecture level, when a
38025 breakpoint instruction executes the program counter points at the
38026 breakpoint address plus an offset. On such targets, the stub is
38027 responsible for adjusting the PC to point back at the breakpoint
38030 This packet should not be sent by default; older @value{GDBN} versions
38031 did not support it. @value{GDBN} requests it, by supplying an
38032 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38033 remote stub must also supply the appropriate @samp{qSupported} feature
38034 indicating support.
38036 This packet is required for correct non-stop mode operation.
38039 The packet indicates the target stopped for a hardware breakpoint.
38040 The @var{r} part must be left empty.
38042 The same remarks about @samp{qSupported} and non-stop mode above
38045 @cindex fork events, remote reply
38047 The packet indicates that @code{fork} was called, and @var{r}
38048 is the thread ID of the new child process. Refer to
38049 @ref{thread-id syntax} for the format of the @var{thread-id}
38050 field. This packet is only applicable to targets that support
38053 This packet should not be sent by default; older @value{GDBN} versions
38054 did not support it. @value{GDBN} requests it, by supplying an
38055 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38056 remote stub must also supply the appropriate @samp{qSupported} feature
38057 indicating support.
38059 @cindex vfork events, remote reply
38061 The packet indicates that @code{vfork} was called, and @var{r}
38062 is the thread ID of the new child process. Refer to
38063 @ref{thread-id syntax} for the format of the @var{thread-id}
38064 field. This packet is only applicable to targets that support
38067 This packet should not be sent by default; older @value{GDBN} versions
38068 did not support it. @value{GDBN} requests it, by supplying an
38069 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38070 remote stub must also supply the appropriate @samp{qSupported} feature
38071 indicating support.
38073 @cindex vforkdone events, remote reply
38075 The packet indicates that a child process created by a vfork
38076 has either called @code{exec} or terminated, so that the
38077 address spaces of the parent and child process are no longer
38078 shared. The @var{r} part is ignored. This packet is only
38079 applicable to targets that support vforkdone events.
38081 This packet should not be sent by default; older @value{GDBN} versions
38082 did not support it. @value{GDBN} requests it, by supplying an
38083 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38084 remote stub must also supply the appropriate @samp{qSupported} feature
38085 indicating support.
38087 @cindex exec events, remote reply
38089 The packet indicates that @code{execve} was called, and @var{r}
38090 is the absolute pathname of the file that was executed, in hex.
38091 This packet is only applicable to targets that support exec events.
38093 This packet should not be sent by default; older @value{GDBN} versions
38094 did not support it. @value{GDBN} requests it, by supplying an
38095 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38096 remote stub must also supply the appropriate @samp{qSupported} feature
38097 indicating support.
38099 @cindex thread create event, remote reply
38100 @anchor{thread create event}
38102 The packet indicates that the thread was just created. The new thread
38103 is stopped until @value{GDBN} sets it running with a resumption packet
38104 (@pxref{vCont packet}). This packet should not be sent by default;
38105 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
38106 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
38107 @var{r} part is ignored.
38112 @itemx W @var{AA} ; process:@var{pid}
38113 The process exited, and @var{AA} is the exit status. This is only
38114 applicable to certain targets.
38116 The second form of the response, including the process ID of the
38117 exited process, can be used only when @value{GDBN} has reported
38118 support for multiprocess protocol extensions; see @ref{multiprocess
38119 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38123 @itemx X @var{AA} ; process:@var{pid}
38124 The process terminated with signal @var{AA}.
38126 The second form of the response, including the process ID of the
38127 terminated process, can be used only when @value{GDBN} has reported
38128 support for multiprocess protocol extensions; see @ref{multiprocess
38129 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38132 @anchor{thread exit event}
38133 @cindex thread exit event, remote reply
38134 @item w @var{AA} ; @var{tid}
38136 The thread exited, and @var{AA} is the exit status. This response
38137 should not be sent by default; @value{GDBN} requests it with the
38138 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
38139 @var{AA} is formatted as a big-endian hex string.
38142 There are no resumed threads left in the target. In other words, even
38143 though the process is alive, the last resumed thread has exited. For
38144 example, say the target process has two threads: thread 1 and thread
38145 2. The client leaves thread 1 stopped, and resumes thread 2, which
38146 subsequently exits. At this point, even though the process is still
38147 alive, and thus no @samp{W} stop reply is sent, no thread is actually
38148 executing either. The @samp{N} stop reply thus informs the client
38149 that it can stop waiting for stop replies. This packet should not be
38150 sent by default; older @value{GDBN} versions did not support it.
38151 @value{GDBN} requests it, by supplying an appropriate
38152 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
38153 also supply the appropriate @samp{qSupported} feature indicating
38156 @item O @var{XX}@dots{}
38157 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38158 written as the program's console output. This can happen at any time
38159 while the program is running and the debugger should continue to wait
38160 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38162 @item F @var{call-id},@var{parameter}@dots{}
38163 @var{call-id} is the identifier which says which host system call should
38164 be called. This is just the name of the function. Translation into the
38165 correct system call is only applicable as it's defined in @value{GDBN}.
38166 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38169 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38170 this very system call.
38172 The target replies with this packet when it expects @value{GDBN} to
38173 call a host system call on behalf of the target. @value{GDBN} replies
38174 with an appropriate @samp{F} packet and keeps up waiting for the next
38175 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38176 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38177 Protocol Extension}, for more details.
38181 @node General Query Packets
38182 @section General Query Packets
38183 @cindex remote query requests
38185 Packets starting with @samp{q} are @dfn{general query packets};
38186 packets starting with @samp{Q} are @dfn{general set packets}. General
38187 query and set packets are a semi-unified form for retrieving and
38188 sending information to and from the stub.
38190 The initial letter of a query or set packet is followed by a name
38191 indicating what sort of thing the packet applies to. For example,
38192 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38193 definitions with the stub. These packet names follow some
38198 The name must not contain commas, colons or semicolons.
38200 Most @value{GDBN} query and set packets have a leading upper case
38203 The names of custom vendor packets should use a company prefix, in
38204 lower case, followed by a period. For example, packets designed at
38205 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38206 foos) or @samp{Qacme.bar} (for setting bars).
38209 The name of a query or set packet should be separated from any
38210 parameters by a @samp{:}; the parameters themselves should be
38211 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38212 full packet name, and check for a separator or the end of the packet,
38213 in case two packet names share a common prefix. New packets should not begin
38214 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38215 packets predate these conventions, and have arguments without any terminator
38216 for the packet name; we suspect they are in widespread use in places that
38217 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38218 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38221 Like the descriptions of the other packets, each description here
38222 has a template showing the packet's overall syntax, followed by an
38223 explanation of the packet's meaning. We include spaces in some of the
38224 templates for clarity; these are not part of the packet's syntax. No
38225 @value{GDBN} packet uses spaces to separate its components.
38227 Here are the currently defined query and set packets:
38233 Turn on or off the agent as a helper to perform some debugging operations
38234 delegated from @value{GDBN} (@pxref{Control Agent}).
38236 @item QAllow:@var{op}:@var{val}@dots{}
38237 @cindex @samp{QAllow} packet
38238 Specify which operations @value{GDBN} expects to request of the
38239 target, as a semicolon-separated list of operation name and value
38240 pairs. Possible values for @var{op} include @samp{WriteReg},
38241 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38242 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38243 indicating that @value{GDBN} will not request the operation, or 1,
38244 indicating that it may. (The target can then use this to set up its
38245 own internals optimally, for instance if the debugger never expects to
38246 insert breakpoints, it may not need to install its own trap handler.)
38249 @cindex current thread, remote request
38250 @cindex @samp{qC} packet
38251 Return the current thread ID.
38255 @item QC @var{thread-id}
38256 Where @var{thread-id} is a thread ID as documented in
38257 @ref{thread-id syntax}.
38258 @item @r{(anything else)}
38259 Any other reply implies the old thread ID.
38262 @item qCRC:@var{addr},@var{length}
38263 @cindex CRC of memory block, remote request
38264 @cindex @samp{qCRC} packet
38265 @anchor{qCRC packet}
38266 Compute the CRC checksum of a block of memory using CRC-32 defined in
38267 IEEE 802.3. The CRC is computed byte at a time, taking the most
38268 significant bit of each byte first. The initial pattern code
38269 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38271 @emph{Note:} This is the same CRC used in validating separate debug
38272 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38273 Files}). However the algorithm is slightly different. When validating
38274 separate debug files, the CRC is computed taking the @emph{least}
38275 significant bit of each byte first, and the final result is inverted to
38276 detect trailing zeros.
38281 An error (such as memory fault)
38282 @item C @var{crc32}
38283 The specified memory region's checksum is @var{crc32}.
38286 @item QDisableRandomization:@var{value}
38287 @cindex disable address space randomization, remote request
38288 @cindex @samp{QDisableRandomization} packet
38289 Some target operating systems will randomize the virtual address space
38290 of the inferior process as a security feature, but provide a feature
38291 to disable such randomization, e.g.@: to allow for a more deterministic
38292 debugging experience. On such systems, this packet with a @var{value}
38293 of 1 directs the target to disable address space randomization for
38294 processes subsequently started via @samp{vRun} packets, while a packet
38295 with a @var{value} of 0 tells the target to enable address space
38298 This packet is only available in extended mode (@pxref{extended mode}).
38303 The request succeeded.
38306 An error occurred. The error number @var{nn} is given as hex digits.
38309 An empty reply indicates that @samp{QDisableRandomization} is not supported
38313 This packet is not probed by default; the remote stub must request it,
38314 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38315 This should only be done on targets that actually support disabling
38316 address space randomization.
38318 @item QStartupWithShell:@var{value}
38319 @cindex startup with shell, remote request
38320 @cindex @samp{QStartupWithShell} packet
38321 On UNIX-like targets, it is possible to start the inferior using a
38322 shell program. This is the default behavior on both @value{GDBN} and
38323 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38324 used to inform @command{gdbserver} whether it should start the
38325 inferior using a shell or not.
38327 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38328 to start the inferior. If @var{value} is @samp{1},
38329 @command{gdbserver} will use a shell to start the inferior. All other
38330 values are considered an error.
38332 This packet is only available in extended mode (@pxref{extended
38338 The request succeeded.
38341 An error occurred. The error number @var{nn} is given as hex digits.
38344 This packet is not probed by default; the remote stub must request it,
38345 by supplying an appropriate @samp{qSupported} response
38346 (@pxref{qSupported}). This should only be done on targets that
38347 actually support starting the inferior using a shell.
38349 Use of this packet is controlled by the @code{set startup-with-shell}
38350 command; @pxref{set startup-with-shell}.
38352 @item QEnvironmentHexEncoded:@var{hex-value}
38353 @anchor{QEnvironmentHexEncoded}
38354 @cindex set environment variable, remote request
38355 @cindex @samp{QEnvironmentHexEncoded} packet
38356 On UNIX-like targets, it is possible to set environment variables that
38357 will be passed to the inferior during the startup process. This
38358 packet is used to inform @command{gdbserver} of an environment
38359 variable that has been defined by the user on @value{GDBN} (@pxref{set
38362 The packet is composed by @var{hex-value}, an hex encoded
38363 representation of the @var{name=value} format representing an
38364 environment variable. The name of the environment variable is
38365 represented by @var{name}, and the value to be assigned to the
38366 environment variable is represented by @var{value}. If the variable
38367 has no value (i.e., the value is @code{null}), then @var{value} will
38370 This packet is only available in extended mode (@pxref{extended
38376 The request succeeded.
38379 This packet is not probed by default; the remote stub must request it,
38380 by supplying an appropriate @samp{qSupported} response
38381 (@pxref{qSupported}). This should only be done on targets that
38382 actually support passing environment variables to the starting
38385 This packet is related to the @code{set environment} command;
38386 @pxref{set environment}.
38388 @item QEnvironmentUnset:@var{hex-value}
38389 @anchor{QEnvironmentUnset}
38390 @cindex unset environment variable, remote request
38391 @cindex @samp{QEnvironmentUnset} packet
38392 On UNIX-like targets, it is possible to unset environment variables
38393 before starting the inferior in the remote target. This packet is
38394 used to inform @command{gdbserver} of an environment variable that has
38395 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38397 The packet is composed by @var{hex-value}, an hex encoded
38398 representation of the name of the environment variable to be unset.
38400 This packet is only available in extended mode (@pxref{extended
38406 The request succeeded.
38409 This packet is not probed by default; the remote stub must request it,
38410 by supplying an appropriate @samp{qSupported} response
38411 (@pxref{qSupported}). This should only be done on targets that
38412 actually support passing environment variables to the starting
38415 This packet is related to the @code{unset environment} command;
38416 @pxref{unset environment}.
38418 @item QEnvironmentReset
38419 @anchor{QEnvironmentReset}
38420 @cindex reset environment, remote request
38421 @cindex @samp{QEnvironmentReset} packet
38422 On UNIX-like targets, this packet is used to reset the state of
38423 environment variables in the remote target before starting the
38424 inferior. In this context, reset means unsetting all environment
38425 variables that were previously set by the user (i.e., were not
38426 initially present in the environment). It is sent to
38427 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38428 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38429 (@pxref{QEnvironmentUnset}) packets.
38431 This packet is only available in extended mode (@pxref{extended
38437 The request succeeded.
38440 This packet is not probed by default; the remote stub must request it,
38441 by supplying an appropriate @samp{qSupported} response
38442 (@pxref{qSupported}). This should only be done on targets that
38443 actually support passing environment variables to the starting
38446 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38447 @anchor{QSetWorkingDir packet}
38448 @cindex set working directory, remote request
38449 @cindex @samp{QSetWorkingDir} packet
38450 This packet is used to inform the remote server of the intended
38451 current working directory for programs that are going to be executed.
38453 The packet is composed by @var{directory}, an hex encoded
38454 representation of the directory that the remote inferior will use as
38455 its current working directory. If @var{directory} is an empty string,
38456 the remote server should reset the inferior's current working
38457 directory to its original, empty value.
38459 This packet is only available in extended mode (@pxref{extended
38465 The request succeeded.
38469 @itemx qsThreadInfo
38470 @cindex list active threads, remote request
38471 @cindex @samp{qfThreadInfo} packet
38472 @cindex @samp{qsThreadInfo} packet
38473 Obtain a list of all active thread IDs from the target (OS). Since there
38474 may be too many active threads to fit into one reply packet, this query
38475 works iteratively: it may require more than one query/reply sequence to
38476 obtain the entire list of threads. The first query of the sequence will
38477 be the @samp{qfThreadInfo} query; subsequent queries in the
38478 sequence will be the @samp{qsThreadInfo} query.
38480 NOTE: This packet replaces the @samp{qL} query (see below).
38484 @item m @var{thread-id}
38486 @item m @var{thread-id},@var{thread-id}@dots{}
38487 a comma-separated list of thread IDs
38489 (lower case letter @samp{L}) denotes end of list.
38492 In response to each query, the target will reply with a list of one or
38493 more thread IDs, separated by commas.
38494 @value{GDBN} will respond to each reply with a request for more thread
38495 ids (using the @samp{qs} form of the query), until the target responds
38496 with @samp{l} (lower-case ell, for @dfn{last}).
38497 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38500 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38501 initial connection with the remote target, and the very first thread ID
38502 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38503 message. Therefore, the stub should ensure that the first thread ID in
38504 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38506 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38507 @cindex get thread-local storage address, remote request
38508 @cindex @samp{qGetTLSAddr} packet
38509 Fetch the address associated with thread local storage specified
38510 by @var{thread-id}, @var{offset}, and @var{lm}.
38512 @var{thread-id} is the thread ID associated with the
38513 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38515 @var{offset} is the (big endian, hex encoded) offset associated with the
38516 thread local variable. (This offset is obtained from the debug
38517 information associated with the variable.)
38519 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38520 load module associated with the thread local storage. For example,
38521 a @sc{gnu}/Linux system will pass the link map address of the shared
38522 object associated with the thread local storage under consideration.
38523 Other operating environments may choose to represent the load module
38524 differently, so the precise meaning of this parameter will vary.
38528 @item @var{XX}@dots{}
38529 Hex encoded (big endian) bytes representing the address of the thread
38530 local storage requested.
38533 An error occurred. The error number @var{nn} is given as hex digits.
38536 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38539 @item qGetTIBAddr:@var{thread-id}
38540 @cindex get thread information block address
38541 @cindex @samp{qGetTIBAddr} packet
38542 Fetch address of the Windows OS specific Thread Information Block.
38544 @var{thread-id} is the thread ID associated with the thread.
38548 @item @var{XX}@dots{}
38549 Hex encoded (big endian) bytes representing the linear address of the
38550 thread information block.
38553 An error occured. This means that either the thread was not found, or the
38554 address could not be retrieved.
38557 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38560 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38561 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38562 digit) is one to indicate the first query and zero to indicate a
38563 subsequent query; @var{threadcount} (two hex digits) is the maximum
38564 number of threads the response packet can contain; and @var{nextthread}
38565 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38566 returned in the response as @var{argthread}.
38568 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38572 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38573 Where: @var{count} (two hex digits) is the number of threads being
38574 returned; @var{done} (one hex digit) is zero to indicate more threads
38575 and one indicates no further threads; @var{argthreadid} (eight hex
38576 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38577 is a sequence of thread IDs, @var{threadid} (eight hex
38578 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38582 @cindex section offsets, remote request
38583 @cindex @samp{qOffsets} packet
38584 Get section offsets that the target used when relocating the downloaded
38589 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38590 Relocate the @code{Text} section by @var{xxx} from its original address.
38591 Relocate the @code{Data} section by @var{yyy} from its original address.
38592 If the object file format provides segment information (e.g.@: @sc{elf}
38593 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38594 segments by the supplied offsets.
38596 @emph{Note: while a @code{Bss} offset may be included in the response,
38597 @value{GDBN} ignores this and instead applies the @code{Data} offset
38598 to the @code{Bss} section.}
38600 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38601 Relocate the first segment of the object file, which conventionally
38602 contains program code, to a starting address of @var{xxx}. If
38603 @samp{DataSeg} is specified, relocate the second segment, which
38604 conventionally contains modifiable data, to a starting address of
38605 @var{yyy}. @value{GDBN} will report an error if the object file
38606 does not contain segment information, or does not contain at least
38607 as many segments as mentioned in the reply. Extra segments are
38608 kept at fixed offsets relative to the last relocated segment.
38611 @item qP @var{mode} @var{thread-id}
38612 @cindex thread information, remote request
38613 @cindex @samp{qP} packet
38614 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38615 encoded 32 bit mode; @var{thread-id} is a thread ID
38616 (@pxref{thread-id syntax}).
38618 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38621 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38625 @cindex non-stop mode, remote request
38626 @cindex @samp{QNonStop} packet
38628 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38629 @xref{Remote Non-Stop}, for more information.
38634 The request succeeded.
38637 An error occurred. The error number @var{nn} is given as hex digits.
38640 An empty reply indicates that @samp{QNonStop} is not supported by
38644 This packet is not probed by default; the remote stub must request it,
38645 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38646 Use of this packet is controlled by the @code{set non-stop} command;
38647 @pxref{Non-Stop Mode}.
38649 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38650 @itemx QCatchSyscalls:0
38651 @cindex catch syscalls from inferior, remote request
38652 @cindex @samp{QCatchSyscalls} packet
38653 @anchor{QCatchSyscalls}
38654 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38655 catching syscalls from the inferior process.
38657 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38658 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38659 is listed, every system call should be reported.
38661 Note that if a syscall not in the list is reported, @value{GDBN} will
38662 still filter the event according to its own list from all corresponding
38663 @code{catch syscall} commands. However, it is more efficient to only
38664 report the requested syscalls.
38666 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38667 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38669 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38670 kept for the new process too. On targets where exec may affect syscall
38671 numbers, for example with exec between 32 and 64-bit processes, the
38672 client should send a new packet with the new syscall list.
38677 The request succeeded.
38680 An error occurred. @var{nn} are hex digits.
38683 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38687 Use of this packet is controlled by the @code{set remote catch-syscalls}
38688 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38689 This packet is not probed by default; the remote stub must request it,
38690 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38692 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38693 @cindex pass signals to inferior, remote request
38694 @cindex @samp{QPassSignals} packet
38695 @anchor{QPassSignals}
38696 Each listed @var{signal} should be passed directly to the inferior process.
38697 Signals are numbered identically to continue packets and stop replies
38698 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38699 strictly greater than the previous item. These signals do not need to stop
38700 the inferior, or be reported to @value{GDBN}. All other signals should be
38701 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38702 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38703 new list. This packet improves performance when using @samp{handle
38704 @var{signal} nostop noprint pass}.
38709 The request succeeded.
38712 An error occurred. The error number @var{nn} is given as hex digits.
38715 An empty reply indicates that @samp{QPassSignals} is not supported by
38719 Use of this packet is controlled by the @code{set remote pass-signals}
38720 command (@pxref{Remote Configuration, set remote pass-signals}).
38721 This packet is not probed by default; the remote stub must request it,
38722 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38724 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38725 @cindex signals the inferior may see, remote request
38726 @cindex @samp{QProgramSignals} packet
38727 @anchor{QProgramSignals}
38728 Each listed @var{signal} may be delivered to the inferior process.
38729 Others should be silently discarded.
38731 In some cases, the remote stub may need to decide whether to deliver a
38732 signal to the program or not without @value{GDBN} involvement. One
38733 example of that is while detaching --- the program's threads may have
38734 stopped for signals that haven't yet had a chance of being reported to
38735 @value{GDBN}, and so the remote stub can use the signal list specified
38736 by this packet to know whether to deliver or ignore those pending
38739 This does not influence whether to deliver a signal as requested by a
38740 resumption packet (@pxref{vCont packet}).
38742 Signals are numbered identically to continue packets and stop replies
38743 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38744 strictly greater than the previous item. Multiple
38745 @samp{QProgramSignals} packets do not combine; any earlier
38746 @samp{QProgramSignals} list is completely replaced by the new list.
38751 The request succeeded.
38754 An error occurred. The error number @var{nn} is given as hex digits.
38757 An empty reply indicates that @samp{QProgramSignals} is not supported
38761 Use of this packet is controlled by the @code{set remote program-signals}
38762 command (@pxref{Remote Configuration, set remote program-signals}).
38763 This packet is not probed by default; the remote stub must request it,
38764 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38766 @anchor{QThreadEvents}
38767 @item QThreadEvents:1
38768 @itemx QThreadEvents:0
38769 @cindex thread create/exit events, remote request
38770 @cindex @samp{QThreadEvents} packet
38772 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38773 reporting of thread create and exit events. @xref{thread create
38774 event}, for the reply specifications. For example, this is used in
38775 non-stop mode when @value{GDBN} stops a set of threads and
38776 synchronously waits for the their corresponding stop replies. Without
38777 exit events, if one of the threads exits, @value{GDBN} would hang
38778 forever not knowing that it should no longer expect a stop for that
38779 same thread. @value{GDBN} does not enable this feature unless the
38780 stub reports that it supports it by including @samp{QThreadEvents+} in
38781 its @samp{qSupported} reply.
38786 The request succeeded.
38789 An error occurred. The error number @var{nn} is given as hex digits.
38792 An empty reply indicates that @samp{QThreadEvents} is not supported by
38796 Use of this packet is controlled by the @code{set remote thread-events}
38797 command (@pxref{Remote Configuration, set remote thread-events}).
38799 @item qRcmd,@var{command}
38800 @cindex execute remote command, remote request
38801 @cindex @samp{qRcmd} packet
38802 @var{command} (hex encoded) is passed to the local interpreter for
38803 execution. Invalid commands should be reported using the output
38804 string. Before the final result packet, the target may also respond
38805 with a number of intermediate @samp{O@var{output}} console output
38806 packets. @emph{Implementors should note that providing access to a
38807 stubs's interpreter may have security implications}.
38812 A command response with no output.
38814 A command response with the hex encoded output string @var{OUTPUT}.
38816 Indicate a badly formed request.
38818 An empty reply indicates that @samp{qRcmd} is not recognized.
38821 (Note that the @code{qRcmd} packet's name is separated from the
38822 command by a @samp{,}, not a @samp{:}, contrary to the naming
38823 conventions above. Please don't use this packet as a model for new
38826 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38827 @cindex searching memory, in remote debugging
38829 @cindex @samp{qSearch:memory} packet
38831 @cindex @samp{qSearch memory} packet
38832 @anchor{qSearch memory}
38833 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38834 Both @var{address} and @var{length} are encoded in hex;
38835 @var{search-pattern} is a sequence of bytes, also hex encoded.
38840 The pattern was not found.
38842 The pattern was found at @var{address}.
38844 A badly formed request or an error was encountered while searching memory.
38846 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38849 @item QStartNoAckMode
38850 @cindex @samp{QStartNoAckMode} packet
38851 @anchor{QStartNoAckMode}
38852 Request that the remote stub disable the normal @samp{+}/@samp{-}
38853 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38858 The stub has switched to no-acknowledgment mode.
38859 @value{GDBN} acknowledges this reponse,
38860 but neither the stub nor @value{GDBN} shall send or expect further
38861 @samp{+}/@samp{-} acknowledgments in the current connection.
38863 An empty reply indicates that the stub does not support no-acknowledgment mode.
38866 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38867 @cindex supported packets, remote query
38868 @cindex features of the remote protocol
38869 @cindex @samp{qSupported} packet
38870 @anchor{qSupported}
38871 Tell the remote stub about features supported by @value{GDBN}, and
38872 query the stub for features it supports. This packet allows
38873 @value{GDBN} and the remote stub to take advantage of each others'
38874 features. @samp{qSupported} also consolidates multiple feature probes
38875 at startup, to improve @value{GDBN} performance---a single larger
38876 packet performs better than multiple smaller probe packets on
38877 high-latency links. Some features may enable behavior which must not
38878 be on by default, e.g.@: because it would confuse older clients or
38879 stubs. Other features may describe packets which could be
38880 automatically probed for, but are not. These features must be
38881 reported before @value{GDBN} will use them. This ``default
38882 unsupported'' behavior is not appropriate for all packets, but it
38883 helps to keep the initial connection time under control with new
38884 versions of @value{GDBN} which support increasing numbers of packets.
38888 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38889 The stub supports or does not support each returned @var{stubfeature},
38890 depending on the form of each @var{stubfeature} (see below for the
38893 An empty reply indicates that @samp{qSupported} is not recognized,
38894 or that no features needed to be reported to @value{GDBN}.
38897 The allowed forms for each feature (either a @var{gdbfeature} in the
38898 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38902 @item @var{name}=@var{value}
38903 The remote protocol feature @var{name} is supported, and associated
38904 with the specified @var{value}. The format of @var{value} depends
38905 on the feature, but it must not include a semicolon.
38907 The remote protocol feature @var{name} is supported, and does not
38908 need an associated value.
38910 The remote protocol feature @var{name} is not supported.
38912 The remote protocol feature @var{name} may be supported, and
38913 @value{GDBN} should auto-detect support in some other way when it is
38914 needed. This form will not be used for @var{gdbfeature} notifications,
38915 but may be used for @var{stubfeature} responses.
38918 Whenever the stub receives a @samp{qSupported} request, the
38919 supplied set of @value{GDBN} features should override any previous
38920 request. This allows @value{GDBN} to put the stub in a known
38921 state, even if the stub had previously been communicating with
38922 a different version of @value{GDBN}.
38924 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38929 This feature indicates whether @value{GDBN} supports multiprocess
38930 extensions to the remote protocol. @value{GDBN} does not use such
38931 extensions unless the stub also reports that it supports them by
38932 including @samp{multiprocess+} in its @samp{qSupported} reply.
38933 @xref{multiprocess extensions}, for details.
38936 This feature indicates that @value{GDBN} supports the XML target
38937 description. If the stub sees @samp{xmlRegisters=} with target
38938 specific strings separated by a comma, it will report register
38942 This feature indicates whether @value{GDBN} supports the
38943 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38944 instruction reply packet}).
38947 This feature indicates whether @value{GDBN} supports the swbreak stop
38948 reason in stop replies. @xref{swbreak stop reason}, for details.
38951 This feature indicates whether @value{GDBN} supports the hwbreak stop
38952 reason in stop replies. @xref{swbreak stop reason}, for details.
38955 This feature indicates whether @value{GDBN} supports fork event
38956 extensions to the remote protocol. @value{GDBN} does not use such
38957 extensions unless the stub also reports that it supports them by
38958 including @samp{fork-events+} in its @samp{qSupported} reply.
38961 This feature indicates whether @value{GDBN} supports vfork event
38962 extensions to the remote protocol. @value{GDBN} does not use such
38963 extensions unless the stub also reports that it supports them by
38964 including @samp{vfork-events+} in its @samp{qSupported} reply.
38967 This feature indicates whether @value{GDBN} supports exec event
38968 extensions to the remote protocol. @value{GDBN} does not use such
38969 extensions unless the stub also reports that it supports them by
38970 including @samp{exec-events+} in its @samp{qSupported} reply.
38972 @item vContSupported
38973 This feature indicates whether @value{GDBN} wants to know the
38974 supported actions in the reply to @samp{vCont?} packet.
38977 Stubs should ignore any unknown values for
38978 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38979 packet supports receiving packets of unlimited length (earlier
38980 versions of @value{GDBN} may reject overly long responses). Additional values
38981 for @var{gdbfeature} may be defined in the future to let the stub take
38982 advantage of new features in @value{GDBN}, e.g.@: incompatible
38983 improvements in the remote protocol---the @samp{multiprocess} feature is
38984 an example of such a feature. The stub's reply should be independent
38985 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38986 describes all the features it supports, and then the stub replies with
38987 all the features it supports.
38989 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38990 responses, as long as each response uses one of the standard forms.
38992 Some features are flags. A stub which supports a flag feature
38993 should respond with a @samp{+} form response. Other features
38994 require values, and the stub should respond with an @samp{=}
38997 Each feature has a default value, which @value{GDBN} will use if
38998 @samp{qSupported} is not available or if the feature is not mentioned
38999 in the @samp{qSupported} response. The default values are fixed; a
39000 stub is free to omit any feature responses that match the defaults.
39002 Not all features can be probed, but for those which can, the probing
39003 mechanism is useful: in some cases, a stub's internal
39004 architecture may not allow the protocol layer to know some information
39005 about the underlying target in advance. This is especially common in
39006 stubs which may be configured for multiple targets.
39008 These are the currently defined stub features and their properties:
39010 @multitable @columnfractions 0.35 0.2 0.12 0.2
39011 @c NOTE: The first row should be @headitem, but we do not yet require
39012 @c a new enough version of Texinfo (4.7) to use @headitem.
39014 @tab Value Required
39018 @item @samp{PacketSize}
39023 @item @samp{qXfer:auxv:read}
39028 @item @samp{qXfer:btrace:read}
39033 @item @samp{qXfer:btrace-conf:read}
39038 @item @samp{qXfer:exec-file:read}
39043 @item @samp{qXfer:features:read}
39048 @item @samp{qXfer:libraries:read}
39053 @item @samp{qXfer:libraries-svr4:read}
39058 @item @samp{augmented-libraries-svr4-read}
39063 @item @samp{qXfer:memory-map:read}
39068 @item @samp{qXfer:sdata:read}
39073 @item @samp{qXfer:spu:read}
39078 @item @samp{qXfer:spu:write}
39083 @item @samp{qXfer:siginfo:read}
39088 @item @samp{qXfer:siginfo:write}
39093 @item @samp{qXfer:threads:read}
39098 @item @samp{qXfer:traceframe-info:read}
39103 @item @samp{qXfer:uib:read}
39108 @item @samp{qXfer:fdpic:read}
39113 @item @samp{Qbtrace:off}
39118 @item @samp{Qbtrace:bts}
39123 @item @samp{Qbtrace:pt}
39128 @item @samp{Qbtrace-conf:bts:size}
39133 @item @samp{Qbtrace-conf:pt:size}
39138 @item @samp{QNonStop}
39143 @item @samp{QCatchSyscalls}
39148 @item @samp{QPassSignals}
39153 @item @samp{QStartNoAckMode}
39158 @item @samp{multiprocess}
39163 @item @samp{ConditionalBreakpoints}
39168 @item @samp{ConditionalTracepoints}
39173 @item @samp{ReverseContinue}
39178 @item @samp{ReverseStep}
39183 @item @samp{TracepointSource}
39188 @item @samp{QAgent}
39193 @item @samp{QAllow}
39198 @item @samp{QDisableRandomization}
39203 @item @samp{EnableDisableTracepoints}
39208 @item @samp{QTBuffer:size}
39213 @item @samp{tracenz}
39218 @item @samp{BreakpointCommands}
39223 @item @samp{swbreak}
39228 @item @samp{hwbreak}
39233 @item @samp{fork-events}
39238 @item @samp{vfork-events}
39243 @item @samp{exec-events}
39248 @item @samp{QThreadEvents}
39253 @item @samp{no-resumed}
39260 These are the currently defined stub features, in more detail:
39263 @cindex packet size, remote protocol
39264 @item PacketSize=@var{bytes}
39265 The remote stub can accept packets up to at least @var{bytes} in
39266 length. @value{GDBN} will send packets up to this size for bulk
39267 transfers, and will never send larger packets. This is a limit on the
39268 data characters in the packet, including the frame and checksum.
39269 There is no trailing NUL byte in a remote protocol packet; if the stub
39270 stores packets in a NUL-terminated format, it should allow an extra
39271 byte in its buffer for the NUL. If this stub feature is not supported,
39272 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39274 @item qXfer:auxv:read
39275 The remote stub understands the @samp{qXfer:auxv:read} packet
39276 (@pxref{qXfer auxiliary vector read}).
39278 @item qXfer:btrace:read
39279 The remote stub understands the @samp{qXfer:btrace:read}
39280 packet (@pxref{qXfer btrace read}).
39282 @item qXfer:btrace-conf:read
39283 The remote stub understands the @samp{qXfer:btrace-conf:read}
39284 packet (@pxref{qXfer btrace-conf read}).
39286 @item qXfer:exec-file:read
39287 The remote stub understands the @samp{qXfer:exec-file:read} packet
39288 (@pxref{qXfer executable filename read}).
39290 @item qXfer:features:read
39291 The remote stub understands the @samp{qXfer:features:read} packet
39292 (@pxref{qXfer target description read}).
39294 @item qXfer:libraries:read
39295 The remote stub understands the @samp{qXfer:libraries:read} packet
39296 (@pxref{qXfer library list read}).
39298 @item qXfer:libraries-svr4:read
39299 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39300 (@pxref{qXfer svr4 library list read}).
39302 @item augmented-libraries-svr4-read
39303 The remote stub understands the augmented form of the
39304 @samp{qXfer:libraries-svr4:read} packet
39305 (@pxref{qXfer svr4 library list read}).
39307 @item qXfer:memory-map:read
39308 The remote stub understands the @samp{qXfer:memory-map:read} packet
39309 (@pxref{qXfer memory map read}).
39311 @item qXfer:sdata:read
39312 The remote stub understands the @samp{qXfer:sdata:read} packet
39313 (@pxref{qXfer sdata read}).
39315 @item qXfer:spu:read
39316 The remote stub understands the @samp{qXfer:spu:read} packet
39317 (@pxref{qXfer spu read}).
39319 @item qXfer:spu:write
39320 The remote stub understands the @samp{qXfer:spu:write} packet
39321 (@pxref{qXfer spu write}).
39323 @item qXfer:siginfo:read
39324 The remote stub understands the @samp{qXfer:siginfo:read} packet
39325 (@pxref{qXfer siginfo read}).
39327 @item qXfer:siginfo:write
39328 The remote stub understands the @samp{qXfer:siginfo:write} packet
39329 (@pxref{qXfer siginfo write}).
39331 @item qXfer:threads:read
39332 The remote stub understands the @samp{qXfer:threads:read} packet
39333 (@pxref{qXfer threads read}).
39335 @item qXfer:traceframe-info:read
39336 The remote stub understands the @samp{qXfer:traceframe-info:read}
39337 packet (@pxref{qXfer traceframe info read}).
39339 @item qXfer:uib:read
39340 The remote stub understands the @samp{qXfer:uib:read}
39341 packet (@pxref{qXfer unwind info block}).
39343 @item qXfer:fdpic:read
39344 The remote stub understands the @samp{qXfer:fdpic:read}
39345 packet (@pxref{qXfer fdpic loadmap read}).
39348 The remote stub understands the @samp{QNonStop} packet
39349 (@pxref{QNonStop}).
39351 @item QCatchSyscalls
39352 The remote stub understands the @samp{QCatchSyscalls} packet
39353 (@pxref{QCatchSyscalls}).
39356 The remote stub understands the @samp{QPassSignals} packet
39357 (@pxref{QPassSignals}).
39359 @item QStartNoAckMode
39360 The remote stub understands the @samp{QStartNoAckMode} packet and
39361 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39364 @anchor{multiprocess extensions}
39365 @cindex multiprocess extensions, in remote protocol
39366 The remote stub understands the multiprocess extensions to the remote
39367 protocol syntax. The multiprocess extensions affect the syntax of
39368 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39369 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39370 replies. Note that reporting this feature indicates support for the
39371 syntactic extensions only, not that the stub necessarily supports
39372 debugging of more than one process at a time. The stub must not use
39373 multiprocess extensions in packet replies unless @value{GDBN} has also
39374 indicated it supports them in its @samp{qSupported} request.
39376 @item qXfer:osdata:read
39377 The remote stub understands the @samp{qXfer:osdata:read} packet
39378 ((@pxref{qXfer osdata read}).
39380 @item ConditionalBreakpoints
39381 The target accepts and implements evaluation of conditional expressions
39382 defined for breakpoints. The target will only report breakpoint triggers
39383 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39385 @item ConditionalTracepoints
39386 The remote stub accepts and implements conditional expressions defined
39387 for tracepoints (@pxref{Tracepoint Conditions}).
39389 @item ReverseContinue
39390 The remote stub accepts and implements the reverse continue packet
39394 The remote stub accepts and implements the reverse step packet
39397 @item TracepointSource
39398 The remote stub understands the @samp{QTDPsrc} packet that supplies
39399 the source form of tracepoint definitions.
39402 The remote stub understands the @samp{QAgent} packet.
39405 The remote stub understands the @samp{QAllow} packet.
39407 @item QDisableRandomization
39408 The remote stub understands the @samp{QDisableRandomization} packet.
39410 @item StaticTracepoint
39411 @cindex static tracepoints, in remote protocol
39412 The remote stub supports static tracepoints.
39414 @item InstallInTrace
39415 @anchor{install tracepoint in tracing}
39416 The remote stub supports installing tracepoint in tracing.
39418 @item EnableDisableTracepoints
39419 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39420 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39421 to be enabled and disabled while a trace experiment is running.
39423 @item QTBuffer:size
39424 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39425 packet that allows to change the size of the trace buffer.
39428 @cindex string tracing, in remote protocol
39429 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39430 See @ref{Bytecode Descriptions} for details about the bytecode.
39432 @item BreakpointCommands
39433 @cindex breakpoint commands, in remote protocol
39434 The remote stub supports running a breakpoint's command list itself,
39435 rather than reporting the hit to @value{GDBN}.
39438 The remote stub understands the @samp{Qbtrace:off} packet.
39441 The remote stub understands the @samp{Qbtrace:bts} packet.
39444 The remote stub understands the @samp{Qbtrace:pt} packet.
39446 @item Qbtrace-conf:bts:size
39447 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39449 @item Qbtrace-conf:pt:size
39450 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39453 The remote stub reports the @samp{swbreak} stop reason for memory
39457 The remote stub reports the @samp{hwbreak} stop reason for hardware
39461 The remote stub reports the @samp{fork} stop reason for fork events.
39464 The remote stub reports the @samp{vfork} stop reason for vfork events
39465 and vforkdone events.
39468 The remote stub reports the @samp{exec} stop reason for exec events.
39470 @item vContSupported
39471 The remote stub reports the supported actions in the reply to
39472 @samp{vCont?} packet.
39474 @item QThreadEvents
39475 The remote stub understands the @samp{QThreadEvents} packet.
39478 The remote stub reports the @samp{N} stop reply.
39483 @cindex symbol lookup, remote request
39484 @cindex @samp{qSymbol} packet
39485 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39486 requests. Accept requests from the target for the values of symbols.
39491 The target does not need to look up any (more) symbols.
39492 @item qSymbol:@var{sym_name}
39493 The target requests the value of symbol @var{sym_name} (hex encoded).
39494 @value{GDBN} may provide the value by using the
39495 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39499 @item qSymbol:@var{sym_value}:@var{sym_name}
39500 Set the value of @var{sym_name} to @var{sym_value}.
39502 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39503 target has previously requested.
39505 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39506 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39512 The target does not need to look up any (more) symbols.
39513 @item qSymbol:@var{sym_name}
39514 The target requests the value of a new symbol @var{sym_name} (hex
39515 encoded). @value{GDBN} will continue to supply the values of symbols
39516 (if available), until the target ceases to request them.
39521 @itemx QTDisconnected
39528 @itemx qTMinFTPILen
39530 @xref{Tracepoint Packets}.
39532 @item qThreadExtraInfo,@var{thread-id}
39533 @cindex thread attributes info, remote request
39534 @cindex @samp{qThreadExtraInfo} packet
39535 Obtain from the target OS a printable string description of thread
39536 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39537 for the forms of @var{thread-id}. This
39538 string may contain anything that the target OS thinks is interesting
39539 for @value{GDBN} to tell the user about the thread. The string is
39540 displayed in @value{GDBN}'s @code{info threads} display. Some
39541 examples of possible thread extra info strings are @samp{Runnable}, or
39542 @samp{Blocked on Mutex}.
39546 @item @var{XX}@dots{}
39547 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39548 comprising the printable string containing the extra information about
39549 the thread's attributes.
39552 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39553 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39554 conventions above. Please don't use this packet as a model for new
39573 @xref{Tracepoint Packets}.
39575 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39576 @cindex read special object, remote request
39577 @cindex @samp{qXfer} packet
39578 @anchor{qXfer read}
39579 Read uninterpreted bytes from the target's special data area
39580 identified by the keyword @var{object}. Request @var{length} bytes
39581 starting at @var{offset} bytes into the data. The content and
39582 encoding of @var{annex} is specific to @var{object}; it can supply
39583 additional details about what data to access.
39588 Data @var{data} (@pxref{Binary Data}) has been read from the
39589 target. There may be more data at a higher address (although
39590 it is permitted to return @samp{m} even for the last valid
39591 block of data, as long as at least one byte of data was read).
39592 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39596 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39597 There is no more data to be read. It is possible for @var{data} to
39598 have fewer bytes than the @var{length} in the request.
39601 The @var{offset} in the request is at the end of the data.
39602 There is no more data to be read.
39605 The request was malformed, or @var{annex} was invalid.
39608 The offset was invalid, or there was an error encountered reading the data.
39609 The @var{nn} part is a hex-encoded @code{errno} value.
39612 An empty reply indicates the @var{object} string was not recognized by
39613 the stub, or that the object does not support reading.
39616 Here are the specific requests of this form defined so far. All the
39617 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39618 formats, listed above.
39621 @item qXfer:auxv:read::@var{offset},@var{length}
39622 @anchor{qXfer auxiliary vector read}
39623 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39624 auxiliary vector}. Note @var{annex} must be empty.
39626 This packet is not probed by default; the remote stub must request it,
39627 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39629 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39630 @anchor{qXfer btrace read}
39632 Return a description of the current branch trace.
39633 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39634 packet may have one of the following values:
39638 Returns all available branch trace.
39641 Returns all available branch trace if the branch trace changed since
39642 the last read request.
39645 Returns the new branch trace since the last read request. Adds a new
39646 block to the end of the trace that begins at zero and ends at the source
39647 location of the first branch in the trace buffer. This extra block is
39648 used to stitch traces together.
39650 If the trace buffer overflowed, returns an error indicating the overflow.
39653 This packet is not probed by default; the remote stub must request it
39654 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39656 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39657 @anchor{qXfer btrace-conf read}
39659 Return a description of the current branch trace configuration.
39660 @xref{Branch Trace Configuration Format}.
39662 This packet is not probed by default; the remote stub must request it
39663 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39665 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39666 @anchor{qXfer executable filename read}
39667 Return the full absolute name of the file that was executed to create
39668 a process running on the remote system. The annex specifies the
39669 numeric process ID of the process to query, encoded as a hexadecimal
39670 number. If the annex part is empty the remote stub should return the
39671 filename corresponding to the currently executing process.
39673 This packet is not probed by default; the remote stub must request it,
39674 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39676 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39677 @anchor{qXfer target description read}
39678 Access the @dfn{target description}. @xref{Target Descriptions}. The
39679 annex specifies which XML document to access. The main description is
39680 always loaded from the @samp{target.xml} annex.
39682 This packet is not probed by default; the remote stub must request it,
39683 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39685 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39686 @anchor{qXfer library list read}
39687 Access the target's list of loaded libraries. @xref{Library List Format}.
39688 The annex part of the generic @samp{qXfer} packet must be empty
39689 (@pxref{qXfer read}).
39691 Targets which maintain a list of libraries in the program's memory do
39692 not need to implement this packet; it is designed for platforms where
39693 the operating system manages the list of loaded libraries.
39695 This packet is not probed by default; the remote stub must request it,
39696 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39698 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39699 @anchor{qXfer svr4 library list read}
39700 Access the target's list of loaded libraries when the target is an SVR4
39701 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39702 of the generic @samp{qXfer} packet must be empty unless the remote
39703 stub indicated it supports the augmented form of this packet
39704 by supplying an appropriate @samp{qSupported} response
39705 (@pxref{qXfer read}, @ref{qSupported}).
39707 This packet is optional for better performance on SVR4 targets.
39708 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39710 This packet is not probed by default; the remote stub must request it,
39711 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39713 If the remote stub indicates it supports the augmented form of this
39714 packet then the annex part of the generic @samp{qXfer} packet may
39715 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39716 arguments. The currently supported arguments are:
39719 @item start=@var{address}
39720 A hexadecimal number specifying the address of the @samp{struct
39721 link_map} to start reading the library list from. If unset or zero
39722 then the first @samp{struct link_map} in the library list will be
39723 chosen as the starting point.
39725 @item prev=@var{address}
39726 A hexadecimal number specifying the address of the @samp{struct
39727 link_map} immediately preceding the @samp{struct link_map}
39728 specified by the @samp{start} argument. If unset or zero then
39729 the remote stub will expect that no @samp{struct link_map}
39730 exists prior to the starting point.
39734 Arguments that are not understood by the remote stub will be silently
39737 @item qXfer:memory-map:read::@var{offset},@var{length}
39738 @anchor{qXfer memory map read}
39739 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39740 annex part of the generic @samp{qXfer} packet must be empty
39741 (@pxref{qXfer read}).
39743 This packet is not probed by default; the remote stub must request it,
39744 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39746 @item qXfer:sdata:read::@var{offset},@var{length}
39747 @anchor{qXfer sdata read}
39749 Read contents of the extra collected static tracepoint marker
39750 information. The annex part of the generic @samp{qXfer} packet must
39751 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39754 This packet is not probed by default; the remote stub must request it,
39755 by supplying an appropriate @samp{qSupported} response
39756 (@pxref{qSupported}).
39758 @item qXfer:siginfo:read::@var{offset},@var{length}
39759 @anchor{qXfer siginfo read}
39760 Read contents of the extra signal information on the target
39761 system. The annex part of the generic @samp{qXfer} packet must be
39762 empty (@pxref{qXfer read}).
39764 This packet is not probed by default; the remote stub must request it,
39765 by supplying an appropriate @samp{qSupported} response
39766 (@pxref{qSupported}).
39768 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39769 @anchor{qXfer spu read}
39770 Read contents of an @code{spufs} file on the target system. The
39771 annex specifies which file to read; it must be of the form
39772 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39773 in the target process, and @var{name} identifes the @code{spufs} file
39774 in that context to be accessed.
39776 This packet is not probed by default; the remote stub must request it,
39777 by supplying an appropriate @samp{qSupported} response
39778 (@pxref{qSupported}).
39780 @item qXfer:threads:read::@var{offset},@var{length}
39781 @anchor{qXfer threads read}
39782 Access the list of threads on target. @xref{Thread List Format}. The
39783 annex part of the generic @samp{qXfer} packet must be empty
39784 (@pxref{qXfer read}).
39786 This packet is not probed by default; the remote stub must request it,
39787 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39789 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39790 @anchor{qXfer traceframe info read}
39792 Return a description of the current traceframe's contents.
39793 @xref{Traceframe Info Format}. The annex part of the generic
39794 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39796 This packet is not probed by default; the remote stub must request it,
39797 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39799 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39800 @anchor{qXfer unwind info block}
39802 Return the unwind information block for @var{pc}. This packet is used
39803 on OpenVMS/ia64 to ask the kernel unwind information.
39805 This packet is not probed by default.
39807 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39808 @anchor{qXfer fdpic loadmap read}
39809 Read contents of @code{loadmap}s on the target system. The
39810 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39811 executable @code{loadmap} or interpreter @code{loadmap} to read.
39813 This packet is not probed by default; the remote stub must request it,
39814 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39816 @item qXfer:osdata:read::@var{offset},@var{length}
39817 @anchor{qXfer osdata read}
39818 Access the target's @dfn{operating system information}.
39819 @xref{Operating System Information}.
39823 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39824 @cindex write data into object, remote request
39825 @anchor{qXfer write}
39826 Write uninterpreted bytes into the target's special data area
39827 identified by the keyword @var{object}, starting at @var{offset} bytes
39828 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39829 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39830 is specific to @var{object}; it can supply additional details about what data
39836 @var{nn} (hex encoded) is the number of bytes written.
39837 This may be fewer bytes than supplied in the request.
39840 The request was malformed, or @var{annex} was invalid.
39843 The offset was invalid, or there was an error encountered writing the data.
39844 The @var{nn} part is a hex-encoded @code{errno} value.
39847 An empty reply indicates the @var{object} string was not
39848 recognized by the stub, or that the object does not support writing.
39851 Here are the specific requests of this form defined so far. All the
39852 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39853 formats, listed above.
39856 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39857 @anchor{qXfer siginfo write}
39858 Write @var{data} to the extra signal information on the target system.
39859 The annex part of the generic @samp{qXfer} packet must be
39860 empty (@pxref{qXfer write}).
39862 This packet is not probed by default; the remote stub must request it,
39863 by supplying an appropriate @samp{qSupported} response
39864 (@pxref{qSupported}).
39866 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39867 @anchor{qXfer spu write}
39868 Write @var{data} to an @code{spufs} file on the target system. The
39869 annex specifies which file to write; it must be of the form
39870 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39871 in the target process, and @var{name} identifes the @code{spufs} file
39872 in that context to be accessed.
39874 This packet is not probed by default; the remote stub must request it,
39875 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39878 @item qXfer:@var{object}:@var{operation}:@dots{}
39879 Requests of this form may be added in the future. When a stub does
39880 not recognize the @var{object} keyword, or its support for
39881 @var{object} does not recognize the @var{operation} keyword, the stub
39882 must respond with an empty packet.
39884 @item qAttached:@var{pid}
39885 @cindex query attached, remote request
39886 @cindex @samp{qAttached} packet
39887 Return an indication of whether the remote server attached to an
39888 existing process or created a new process. When the multiprocess
39889 protocol extensions are supported (@pxref{multiprocess extensions}),
39890 @var{pid} is an integer in hexadecimal format identifying the target
39891 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39892 the query packet will be simplified as @samp{qAttached}.
39894 This query is used, for example, to know whether the remote process
39895 should be detached or killed when a @value{GDBN} session is ended with
39896 the @code{quit} command.
39901 The remote server attached to an existing process.
39903 The remote server created a new process.
39905 A badly formed request or an error was encountered.
39909 Enable branch tracing for the current thread using Branch Trace Store.
39914 Branch tracing has been enabled.
39916 A badly formed request or an error was encountered.
39920 Enable branch tracing for the current thread using Intel Processor Trace.
39925 Branch tracing has been enabled.
39927 A badly formed request or an error was encountered.
39931 Disable branch tracing for the current thread.
39936 Branch tracing has been disabled.
39938 A badly formed request or an error was encountered.
39941 @item Qbtrace-conf:bts:size=@var{value}
39942 Set the requested ring buffer size for new threads that use the
39943 btrace recording method in bts format.
39948 The ring buffer size has been set.
39950 A badly formed request or an error was encountered.
39953 @item Qbtrace-conf:pt:size=@var{value}
39954 Set the requested ring buffer size for new threads that use the
39955 btrace recording method in pt format.
39960 The ring buffer size has been set.
39962 A badly formed request or an error was encountered.
39967 @node Architecture-Specific Protocol Details
39968 @section Architecture-Specific Protocol Details
39970 This section describes how the remote protocol is applied to specific
39971 target architectures. Also see @ref{Standard Target Features}, for
39972 details of XML target descriptions for each architecture.
39975 * ARM-Specific Protocol Details::
39976 * MIPS-Specific Protocol Details::
39979 @node ARM-Specific Protocol Details
39980 @subsection @acronym{ARM}-specific Protocol Details
39983 * ARM Breakpoint Kinds::
39986 @node ARM Breakpoint Kinds
39987 @subsubsection @acronym{ARM} Breakpoint Kinds
39988 @cindex breakpoint kinds, @acronym{ARM}
39990 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39995 16-bit Thumb mode breakpoint.
39998 32-bit Thumb mode (Thumb-2) breakpoint.
40001 32-bit @acronym{ARM} mode breakpoint.
40005 @node MIPS-Specific Protocol Details
40006 @subsection @acronym{MIPS}-specific Protocol Details
40009 * MIPS Register packet Format::
40010 * MIPS Breakpoint Kinds::
40013 @node MIPS Register packet Format
40014 @subsubsection @acronym{MIPS} Register Packet Format
40015 @cindex register packet format, @acronym{MIPS}
40017 The following @code{g}/@code{G} packets have previously been defined.
40018 In the below, some thirty-two bit registers are transferred as
40019 sixty-four bits. Those registers should be zero/sign extended (which?)
40020 to fill the space allocated. Register bytes are transferred in target
40021 byte order. The two nibbles within a register byte are transferred
40022 most-significant -- least-significant.
40027 All registers are transferred as thirty-two bit quantities in the order:
40028 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40029 registers; fsr; fir; fp.
40032 All registers are transferred as sixty-four bit quantities (including
40033 thirty-two bit registers such as @code{sr}). The ordering is the same
40038 @node MIPS Breakpoint Kinds
40039 @subsubsection @acronym{MIPS} Breakpoint Kinds
40040 @cindex breakpoint kinds, @acronym{MIPS}
40042 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40047 16-bit @acronym{MIPS16} mode breakpoint.
40050 16-bit @acronym{microMIPS} mode breakpoint.
40053 32-bit standard @acronym{MIPS} mode breakpoint.
40056 32-bit @acronym{microMIPS} mode breakpoint.
40060 @node Tracepoint Packets
40061 @section Tracepoint Packets
40062 @cindex tracepoint packets
40063 @cindex packets, tracepoint
40065 Here we describe the packets @value{GDBN} uses to implement
40066 tracepoints (@pxref{Tracepoints}).
40070 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40071 @cindex @samp{QTDP} packet
40072 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40073 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40074 the tracepoint is disabled. The @var{step} gives the tracepoint's step
40075 count, and @var{pass} gives its pass count. If an @samp{F} is present,
40076 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40077 the number of bytes that the target should copy elsewhere to make room
40078 for the tracepoint. If an @samp{X} is present, it introduces a
40079 tracepoint condition, which consists of a hexadecimal length, followed
40080 by a comma and hex-encoded bytes, in a manner similar to action
40081 encodings as described below. If the trailing @samp{-} is present,
40082 further @samp{QTDP} packets will follow to specify this tracepoint's
40088 The packet was understood and carried out.
40090 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40092 The packet was not recognized.
40095 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40096 Define actions to be taken when a tracepoint is hit. The @var{n} and
40097 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40098 this tracepoint. This packet may only be sent immediately after
40099 another @samp{QTDP} packet that ended with a @samp{-}. If the
40100 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40101 specifying more actions for this tracepoint.
40103 In the series of action packets for a given tracepoint, at most one
40104 can have an @samp{S} before its first @var{action}. If such a packet
40105 is sent, it and the following packets define ``while-stepping''
40106 actions. Any prior packets define ordinary actions --- that is, those
40107 taken when the tracepoint is first hit. If no action packet has an
40108 @samp{S}, then all the packets in the series specify ordinary
40109 tracepoint actions.
40111 The @samp{@var{action}@dots{}} portion of the packet is a series of
40112 actions, concatenated without separators. Each action has one of the
40118 Collect the registers whose bits are set in @var{mask},
40119 a hexadecimal number whose @var{i}'th bit is set if register number
40120 @var{i} should be collected. (The least significant bit is numbered
40121 zero.) Note that @var{mask} may be any number of digits long; it may
40122 not fit in a 32-bit word.
40124 @item M @var{basereg},@var{offset},@var{len}
40125 Collect @var{len} bytes of memory starting at the address in register
40126 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40127 @samp{-1}, then the range has a fixed address: @var{offset} is the
40128 address of the lowest byte to collect. The @var{basereg},
40129 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40130 values (the @samp{-1} value for @var{basereg} is a special case).
40132 @item X @var{len},@var{expr}
40133 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40134 it directs. The agent expression @var{expr} is as described in
40135 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40136 two-digit hex number in the packet; @var{len} is the number of bytes
40137 in the expression (and thus one-half the number of hex digits in the
40142 Any number of actions may be packed together in a single @samp{QTDP}
40143 packet, as long as the packet does not exceed the maximum packet
40144 length (400 bytes, for many stubs). There may be only one @samp{R}
40145 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40146 actions. Any registers referred to by @samp{M} and @samp{X} actions
40147 must be collected by a preceding @samp{R} action. (The
40148 ``while-stepping'' actions are treated as if they were attached to a
40149 separate tracepoint, as far as these restrictions are concerned.)
40154 The packet was understood and carried out.
40156 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40158 The packet was not recognized.
40161 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40162 @cindex @samp{QTDPsrc} packet
40163 Specify a source string of tracepoint @var{n} at address @var{addr}.
40164 This is useful to get accurate reproduction of the tracepoints
40165 originally downloaded at the beginning of the trace run. The @var{type}
40166 is the name of the tracepoint part, such as @samp{cond} for the
40167 tracepoint's conditional expression (see below for a list of types), while
40168 @var{bytes} is the string, encoded in hexadecimal.
40170 @var{start} is the offset of the @var{bytes} within the overall source
40171 string, while @var{slen} is the total length of the source string.
40172 This is intended for handling source strings that are longer than will
40173 fit in a single packet.
40174 @c Add detailed example when this info is moved into a dedicated
40175 @c tracepoint descriptions section.
40177 The available string types are @samp{at} for the location,
40178 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40179 @value{GDBN} sends a separate packet for each command in the action
40180 list, in the same order in which the commands are stored in the list.
40182 The target does not need to do anything with source strings except
40183 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40186 Although this packet is optional, and @value{GDBN} will only send it
40187 if the target replies with @samp{TracepointSource} @xref{General
40188 Query Packets}, it makes both disconnected tracing and trace files
40189 much easier to use. Otherwise the user must be careful that the
40190 tracepoints in effect while looking at trace frames are identical to
40191 the ones in effect during the trace run; even a small discrepancy
40192 could cause @samp{tdump} not to work, or a particular trace frame not
40195 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40196 @cindex define trace state variable, remote request
40197 @cindex @samp{QTDV} packet
40198 Create a new trace state variable, number @var{n}, with an initial
40199 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40200 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40201 the option of not using this packet for initial values of zero; the
40202 target should simply create the trace state variables as they are
40203 mentioned in expressions. The value @var{builtin} should be 1 (one)
40204 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40205 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40206 @samp{qTsV} packet had it set. The contents of @var{name} is the
40207 hex-encoded name (without the leading @samp{$}) of the trace state
40210 @item QTFrame:@var{n}
40211 @cindex @samp{QTFrame} packet
40212 Select the @var{n}'th tracepoint frame from the buffer, and use the
40213 register and memory contents recorded there to answer subsequent
40214 request packets from @value{GDBN}.
40216 A successful reply from the stub indicates that the stub has found the
40217 requested frame. The response is a series of parts, concatenated
40218 without separators, describing the frame we selected. Each part has
40219 one of the following forms:
40223 The selected frame is number @var{n} in the trace frame buffer;
40224 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40225 was no frame matching the criteria in the request packet.
40228 The selected trace frame records a hit of tracepoint number @var{t};
40229 @var{t} is a hexadecimal number.
40233 @item QTFrame:pc:@var{addr}
40234 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40235 currently selected frame whose PC is @var{addr};
40236 @var{addr} is a hexadecimal number.
40238 @item QTFrame:tdp:@var{t}
40239 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40240 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40241 is a hexadecimal number.
40243 @item QTFrame:range:@var{start}:@var{end}
40244 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40245 currently selected frame whose PC is between @var{start} (inclusive)
40246 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40249 @item QTFrame:outside:@var{start}:@var{end}
40250 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40251 frame @emph{outside} the given range of addresses (exclusive).
40254 @cindex @samp{qTMinFTPILen} packet
40255 This packet requests the minimum length of instruction at which a fast
40256 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40257 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40258 it depends on the target system being able to create trampolines in
40259 the first 64K of memory, which might or might not be possible for that
40260 system. So the reply to this packet will be 4 if it is able to
40267 The minimum instruction length is currently unknown.
40269 The minimum instruction length is @var{length}, where @var{length}
40270 is a hexadecimal number greater or equal to 1. A reply
40271 of 1 means that a fast tracepoint may be placed on any instruction
40272 regardless of size.
40274 An error has occurred.
40276 An empty reply indicates that the request is not supported by the stub.
40280 @cindex @samp{QTStart} packet
40281 Begin the tracepoint experiment. Begin collecting data from
40282 tracepoint hits in the trace frame buffer. This packet supports the
40283 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40284 instruction reply packet}).
40287 @cindex @samp{QTStop} packet
40288 End the tracepoint experiment. Stop collecting trace frames.
40290 @item QTEnable:@var{n}:@var{addr}
40292 @cindex @samp{QTEnable} packet
40293 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40294 experiment. If the tracepoint was previously disabled, then collection
40295 of data from it will resume.
40297 @item QTDisable:@var{n}:@var{addr}
40299 @cindex @samp{QTDisable} packet
40300 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40301 experiment. No more data will be collected from the tracepoint unless
40302 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40305 @cindex @samp{QTinit} packet
40306 Clear the table of tracepoints, and empty the trace frame buffer.
40308 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40309 @cindex @samp{QTro} packet
40310 Establish the given ranges of memory as ``transparent''. The stub
40311 will answer requests for these ranges from memory's current contents,
40312 if they were not collected as part of the tracepoint hit.
40314 @value{GDBN} uses this to mark read-only regions of memory, like those
40315 containing program code. Since these areas never change, they should
40316 still have the same contents they did when the tracepoint was hit, so
40317 there's no reason for the stub to refuse to provide their contents.
40319 @item QTDisconnected:@var{value}
40320 @cindex @samp{QTDisconnected} packet
40321 Set the choice to what to do with the tracing run when @value{GDBN}
40322 disconnects from the target. A @var{value} of 1 directs the target to
40323 continue the tracing run, while 0 tells the target to stop tracing if
40324 @value{GDBN} is no longer in the picture.
40327 @cindex @samp{qTStatus} packet
40328 Ask the stub if there is a trace experiment running right now.
40330 The reply has the form:
40334 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40335 @var{running} is a single digit @code{1} if the trace is presently
40336 running, or @code{0} if not. It is followed by semicolon-separated
40337 optional fields that an agent may use to report additional status.
40341 If the trace is not running, the agent may report any of several
40342 explanations as one of the optional fields:
40347 No trace has been run yet.
40349 @item tstop[:@var{text}]:0
40350 The trace was stopped by a user-originated stop command. The optional
40351 @var{text} field is a user-supplied string supplied as part of the
40352 stop command (for instance, an explanation of why the trace was
40353 stopped manually). It is hex-encoded.
40356 The trace stopped because the trace buffer filled up.
40358 @item tdisconnected:0
40359 The trace stopped because @value{GDBN} disconnected from the target.
40361 @item tpasscount:@var{tpnum}
40362 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40364 @item terror:@var{text}:@var{tpnum}
40365 The trace stopped because tracepoint @var{tpnum} had an error. The
40366 string @var{text} is available to describe the nature of the error
40367 (for instance, a divide by zero in the condition expression); it
40371 The trace stopped for some other reason.
40375 Additional optional fields supply statistical and other information.
40376 Although not required, they are extremely useful for users monitoring
40377 the progress of a trace run. If a trace has stopped, and these
40378 numbers are reported, they must reflect the state of the just-stopped
40383 @item tframes:@var{n}
40384 The number of trace frames in the buffer.
40386 @item tcreated:@var{n}
40387 The total number of trace frames created during the run. This may
40388 be larger than the trace frame count, if the buffer is circular.
40390 @item tsize:@var{n}
40391 The total size of the trace buffer, in bytes.
40393 @item tfree:@var{n}
40394 The number of bytes still unused in the buffer.
40396 @item circular:@var{n}
40397 The value of the circular trace buffer flag. @code{1} means that the
40398 trace buffer is circular and old trace frames will be discarded if
40399 necessary to make room, @code{0} means that the trace buffer is linear
40402 @item disconn:@var{n}
40403 The value of the disconnected tracing flag. @code{1} means that
40404 tracing will continue after @value{GDBN} disconnects, @code{0} means
40405 that the trace run will stop.
40409 @item qTP:@var{tp}:@var{addr}
40410 @cindex tracepoint status, remote request
40411 @cindex @samp{qTP} packet
40412 Ask the stub for the current state of tracepoint number @var{tp} at
40413 address @var{addr}.
40417 @item V@var{hits}:@var{usage}
40418 The tracepoint has been hit @var{hits} times so far during the trace
40419 run, and accounts for @var{usage} in the trace buffer. Note that
40420 @code{while-stepping} steps are not counted as separate hits, but the
40421 steps' space consumption is added into the usage number.
40425 @item qTV:@var{var}
40426 @cindex trace state variable value, remote request
40427 @cindex @samp{qTV} packet
40428 Ask the stub for the value of the trace state variable number @var{var}.
40433 The value of the variable is @var{value}. This will be the current
40434 value of the variable if the user is examining a running target, or a
40435 saved value if the variable was collected in the trace frame that the
40436 user is looking at. Note that multiple requests may result in
40437 different reply values, such as when requesting values while the
40438 program is running.
40441 The value of the variable is unknown. This would occur, for example,
40442 if the user is examining a trace frame in which the requested variable
40447 @cindex @samp{qTfP} packet
40449 @cindex @samp{qTsP} packet
40450 These packets request data about tracepoints that are being used by
40451 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40452 of data, and multiple @code{qTsP} to get additional pieces. Replies
40453 to these packets generally take the form of the @code{QTDP} packets
40454 that define tracepoints. (FIXME add detailed syntax)
40457 @cindex @samp{qTfV} packet
40459 @cindex @samp{qTsV} packet
40460 These packets request data about trace state variables that are on the
40461 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40462 and multiple @code{qTsV} to get additional variables. Replies to
40463 these packets follow the syntax of the @code{QTDV} packets that define
40464 trace state variables.
40470 @cindex @samp{qTfSTM} packet
40471 @cindex @samp{qTsSTM} packet
40472 These packets request data about static tracepoint markers that exist
40473 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40474 first piece of data, and multiple @code{qTsSTM} to get additional
40475 pieces. Replies to these packets take the following form:
40479 @item m @var{address}:@var{id}:@var{extra}
40481 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40482 a comma-separated list of markers
40484 (lower case letter @samp{L}) denotes end of list.
40486 An error occurred. The error number @var{nn} is given as hex digits.
40488 An empty reply indicates that the request is not supported by the
40492 The @var{address} is encoded in hex;
40493 @var{id} and @var{extra} are strings encoded in hex.
40495 In response to each query, the target will reply with a list of one or
40496 more markers, separated by commas. @value{GDBN} will respond to each
40497 reply with a request for more markers (using the @samp{qs} form of the
40498 query), until the target responds with @samp{l} (lower-case ell, for
40501 @item qTSTMat:@var{address}
40503 @cindex @samp{qTSTMat} packet
40504 This packets requests data about static tracepoint markers in the
40505 target program at @var{address}. Replies to this packet follow the
40506 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40507 tracepoint markers.
40509 @item QTSave:@var{filename}
40510 @cindex @samp{QTSave} packet
40511 This packet directs the target to save trace data to the file name
40512 @var{filename} in the target's filesystem. The @var{filename} is encoded
40513 as a hex string; the interpretation of the file name (relative vs
40514 absolute, wild cards, etc) is up to the target.
40516 @item qTBuffer:@var{offset},@var{len}
40517 @cindex @samp{qTBuffer} packet
40518 Return up to @var{len} bytes of the current contents of trace buffer,
40519 starting at @var{offset}. The trace buffer is treated as if it were
40520 a contiguous collection of traceframes, as per the trace file format.
40521 The reply consists as many hex-encoded bytes as the target can deliver
40522 in a packet; it is not an error to return fewer than were asked for.
40523 A reply consisting of just @code{l} indicates that no bytes are
40526 @item QTBuffer:circular:@var{value}
40527 This packet directs the target to use a circular trace buffer if
40528 @var{value} is 1, or a linear buffer if the value is 0.
40530 @item QTBuffer:size:@var{size}
40531 @anchor{QTBuffer-size}
40532 @cindex @samp{QTBuffer size} packet
40533 This packet directs the target to make the trace buffer be of size
40534 @var{size} if possible. A value of @code{-1} tells the target to
40535 use whatever size it prefers.
40537 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40538 @cindex @samp{QTNotes} packet
40539 This packet adds optional textual notes to the trace run. Allowable
40540 types include @code{user}, @code{notes}, and @code{tstop}, the
40541 @var{text} fields are arbitrary strings, hex-encoded.
40545 @subsection Relocate instruction reply packet
40546 When installing fast tracepoints in memory, the target may need to
40547 relocate the instruction currently at the tracepoint address to a
40548 different address in memory. For most instructions, a simple copy is
40549 enough, but, for example, call instructions that implicitly push the
40550 return address on the stack, and relative branches or other
40551 PC-relative instructions require offset adjustment, so that the effect
40552 of executing the instruction at a different address is the same as if
40553 it had executed in the original location.
40555 In response to several of the tracepoint packets, the target may also
40556 respond with a number of intermediate @samp{qRelocInsn} request
40557 packets before the final result packet, to have @value{GDBN} handle
40558 this relocation operation. If a packet supports this mechanism, its
40559 documentation will explicitly say so. See for example the above
40560 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40561 format of the request is:
40564 @item qRelocInsn:@var{from};@var{to}
40566 This requests @value{GDBN} to copy instruction at address @var{from}
40567 to address @var{to}, possibly adjusted so that executing the
40568 instruction at @var{to} has the same effect as executing it at
40569 @var{from}. @value{GDBN} writes the adjusted instruction to target
40570 memory starting at @var{to}.
40575 @item qRelocInsn:@var{adjusted_size}
40576 Informs the stub the relocation is complete. The @var{adjusted_size} is
40577 the length in bytes of resulting relocated instruction sequence.
40579 A badly formed request was detected, or an error was encountered while
40580 relocating the instruction.
40583 @node Host I/O Packets
40584 @section Host I/O Packets
40585 @cindex Host I/O, remote protocol
40586 @cindex file transfer, remote protocol
40588 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40589 operations on the far side of a remote link. For example, Host I/O is
40590 used to upload and download files to a remote target with its own
40591 filesystem. Host I/O uses the same constant values and data structure
40592 layout as the target-initiated File-I/O protocol. However, the
40593 Host I/O packets are structured differently. The target-initiated
40594 protocol relies on target memory to store parameters and buffers.
40595 Host I/O requests are initiated by @value{GDBN}, and the
40596 target's memory is not involved. @xref{File-I/O Remote Protocol
40597 Extension}, for more details on the target-initiated protocol.
40599 The Host I/O request packets all encode a single operation along with
40600 its arguments. They have this format:
40604 @item vFile:@var{operation}: @var{parameter}@dots{}
40605 @var{operation} is the name of the particular request; the target
40606 should compare the entire packet name up to the second colon when checking
40607 for a supported operation. The format of @var{parameter} depends on
40608 the operation. Numbers are always passed in hexadecimal. Negative
40609 numbers have an explicit minus sign (i.e.@: two's complement is not
40610 used). Strings (e.g.@: filenames) are encoded as a series of
40611 hexadecimal bytes. The last argument to a system call may be a
40612 buffer of escaped binary data (@pxref{Binary Data}).
40616 The valid responses to Host I/O packets are:
40620 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40621 @var{result} is the integer value returned by this operation, usually
40622 non-negative for success and -1 for errors. If an error has occured,
40623 @var{errno} will be included in the result specifying a
40624 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40625 operations which return data, @var{attachment} supplies the data as a
40626 binary buffer. Binary buffers in response packets are escaped in the
40627 normal way (@pxref{Binary Data}). See the individual packet
40628 documentation for the interpretation of @var{result} and
40632 An empty response indicates that this operation is not recognized.
40636 These are the supported Host I/O operations:
40639 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40640 Open a file at @var{filename} and return a file descriptor for it, or
40641 return -1 if an error occurs. The @var{filename} is a string,
40642 @var{flags} is an integer indicating a mask of open flags
40643 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40644 of mode bits to use if the file is created (@pxref{mode_t Values}).
40645 @xref{open}, for details of the open flags and mode values.
40647 @item vFile:close: @var{fd}
40648 Close the open file corresponding to @var{fd} and return 0, or
40649 -1 if an error occurs.
40651 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40652 Read data from the open file corresponding to @var{fd}. Up to
40653 @var{count} bytes will be read from the file, starting at @var{offset}
40654 relative to the start of the file. The target may read fewer bytes;
40655 common reasons include packet size limits and an end-of-file
40656 condition. The number of bytes read is returned. Zero should only be
40657 returned for a successful read at the end of the file, or if
40658 @var{count} was zero.
40660 The data read should be returned as a binary attachment on success.
40661 If zero bytes were read, the response should include an empty binary
40662 attachment (i.e.@: a trailing semicolon). The return value is the
40663 number of target bytes read; the binary attachment may be longer if
40664 some characters were escaped.
40666 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40667 Write @var{data} (a binary buffer) to the open file corresponding
40668 to @var{fd}. Start the write at @var{offset} from the start of the
40669 file. Unlike many @code{write} system calls, there is no
40670 separate @var{count} argument; the length of @var{data} in the
40671 packet is used. @samp{vFile:write} returns the number of bytes written,
40672 which may be shorter than the length of @var{data}, or -1 if an
40675 @item vFile:fstat: @var{fd}
40676 Get information about the open file corresponding to @var{fd}.
40677 On success the information is returned as a binary attachment
40678 and the return value is the size of this attachment in bytes.
40679 If an error occurs the return value is -1. The format of the
40680 returned binary attachment is as described in @ref{struct stat}.
40682 @item vFile:unlink: @var{filename}
40683 Delete the file at @var{filename} on the target. Return 0,
40684 or -1 if an error occurs. The @var{filename} is a string.
40686 @item vFile:readlink: @var{filename}
40687 Read value of symbolic link @var{filename} on the target. Return
40688 the number of bytes read, or -1 if an error occurs.
40690 The data read should be returned as a binary attachment on success.
40691 If zero bytes were read, the response should include an empty binary
40692 attachment (i.e.@: a trailing semicolon). The return value is the
40693 number of target bytes read; the binary attachment may be longer if
40694 some characters were escaped.
40696 @item vFile:setfs: @var{pid}
40697 Select the filesystem on which @code{vFile} operations with
40698 @var{filename} arguments will operate. This is required for
40699 @value{GDBN} to be able to access files on remote targets where
40700 the remote stub does not share a common filesystem with the
40703 If @var{pid} is nonzero, select the filesystem as seen by process
40704 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40705 the remote stub. Return 0 on success, or -1 if an error occurs.
40706 If @code{vFile:setfs:} indicates success, the selected filesystem
40707 remains selected until the next successful @code{vFile:setfs:}
40713 @section Interrupts
40714 @cindex interrupts (remote protocol)
40715 @anchor{interrupting remote targets}
40717 In all-stop mode, when a program on the remote target is running,
40718 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40719 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40720 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40722 The precise meaning of @code{BREAK} is defined by the transport
40723 mechanism and may, in fact, be undefined. @value{GDBN} does not
40724 currently define a @code{BREAK} mechanism for any of the network
40725 interfaces except for TCP, in which case @value{GDBN} sends the
40726 @code{telnet} BREAK sequence.
40728 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40729 transport mechanisms. It is represented by sending the single byte
40730 @code{0x03} without any of the usual packet overhead described in
40731 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40732 transmitted as part of a packet, it is considered to be packet data
40733 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40734 (@pxref{X packet}), used for binary downloads, may include an unescaped
40735 @code{0x03} as part of its packet.
40737 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40738 When Linux kernel receives this sequence from serial port,
40739 it stops execution and connects to gdb.
40741 In non-stop mode, because packet resumptions are asynchronous
40742 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40743 command to the remote stub, even when the target is running. For that
40744 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40745 packet}) with the usual packet framing instead of the single byte
40748 Stubs are not required to recognize these interrupt mechanisms and the
40749 precise meaning associated with receipt of the interrupt is
40750 implementation defined. If the target supports debugging of multiple
40751 threads and/or processes, it should attempt to interrupt all
40752 currently-executing threads and processes.
40753 If the stub is successful at interrupting the
40754 running program, it should send one of the stop
40755 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40756 of successfully stopping the program in all-stop mode, and a stop reply
40757 for each stopped thread in non-stop mode.
40758 Interrupts received while the
40759 program is stopped are queued and the program will be interrupted when
40760 it is resumed next time.
40762 @node Notification Packets
40763 @section Notification Packets
40764 @cindex notification packets
40765 @cindex packets, notification
40767 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40768 packets that require no acknowledgment. Both the GDB and the stub
40769 may send notifications (although the only notifications defined at
40770 present are sent by the stub). Notifications carry information
40771 without incurring the round-trip latency of an acknowledgment, and so
40772 are useful for low-impact communications where occasional packet loss
40775 A notification packet has the form @samp{% @var{data} #
40776 @var{checksum}}, where @var{data} is the content of the notification,
40777 and @var{checksum} is a checksum of @var{data}, computed and formatted
40778 as for ordinary @value{GDBN} packets. A notification's @var{data}
40779 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40780 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40781 to acknowledge the notification's receipt or to report its corruption.
40783 Every notification's @var{data} begins with a name, which contains no
40784 colon characters, followed by a colon character.
40786 Recipients should silently ignore corrupted notifications and
40787 notifications they do not understand. Recipients should restart
40788 timeout periods on receipt of a well-formed notification, whether or
40789 not they understand it.
40791 Senders should only send the notifications described here when this
40792 protocol description specifies that they are permitted. In the
40793 future, we may extend the protocol to permit existing notifications in
40794 new contexts; this rule helps older senders avoid confusing newer
40797 (Older versions of @value{GDBN} ignore bytes received until they see
40798 the @samp{$} byte that begins an ordinary packet, so new stubs may
40799 transmit notifications without fear of confusing older clients. There
40800 are no notifications defined for @value{GDBN} to send at the moment, but we
40801 assume that most older stubs would ignore them, as well.)
40803 Each notification is comprised of three parts:
40805 @item @var{name}:@var{event}
40806 The notification packet is sent by the side that initiates the
40807 exchange (currently, only the stub does that), with @var{event}
40808 carrying the specific information about the notification, and
40809 @var{name} specifying the name of the notification.
40811 The acknowledge sent by the other side, usually @value{GDBN}, to
40812 acknowledge the exchange and request the event.
40815 The purpose of an asynchronous notification mechanism is to report to
40816 @value{GDBN} that something interesting happened in the remote stub.
40818 The remote stub may send notification @var{name}:@var{event}
40819 at any time, but @value{GDBN} acknowledges the notification when
40820 appropriate. The notification event is pending before @value{GDBN}
40821 acknowledges. Only one notification at a time may be pending; if
40822 additional events occur before @value{GDBN} has acknowledged the
40823 previous notification, they must be queued by the stub for later
40824 synchronous transmission in response to @var{ack} packets from
40825 @value{GDBN}. Because the notification mechanism is unreliable,
40826 the stub is permitted to resend a notification if it believes
40827 @value{GDBN} may not have received it.
40829 Specifically, notifications may appear when @value{GDBN} is not
40830 otherwise reading input from the stub, or when @value{GDBN} is
40831 expecting to read a normal synchronous response or a
40832 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40833 Notification packets are distinct from any other communication from
40834 the stub so there is no ambiguity.
40836 After receiving a notification, @value{GDBN} shall acknowledge it by
40837 sending a @var{ack} packet as a regular, synchronous request to the
40838 stub. Such acknowledgment is not required to happen immediately, as
40839 @value{GDBN} is permitted to send other, unrelated packets to the
40840 stub first, which the stub should process normally.
40842 Upon receiving a @var{ack} packet, if the stub has other queued
40843 events to report to @value{GDBN}, it shall respond by sending a
40844 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40845 packet to solicit further responses; again, it is permitted to send
40846 other, unrelated packets as well which the stub should process
40849 If the stub receives a @var{ack} packet and there are no additional
40850 @var{event} to report, the stub shall return an @samp{OK} response.
40851 At this point, @value{GDBN} has finished processing a notification
40852 and the stub has completed sending any queued events. @value{GDBN}
40853 won't accept any new notifications until the final @samp{OK} is
40854 received . If further notification events occur, the stub shall send
40855 a new notification, @value{GDBN} shall accept the notification, and
40856 the process shall be repeated.
40858 The process of asynchronous notification can be illustrated by the
40861 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40864 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40866 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40871 The following notifications are defined:
40872 @multitable @columnfractions 0.12 0.12 0.38 0.38
40881 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40882 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40883 for information on how these notifications are acknowledged by
40885 @tab Report an asynchronous stop event in non-stop mode.
40889 @node Remote Non-Stop
40890 @section Remote Protocol Support for Non-Stop Mode
40892 @value{GDBN}'s remote protocol supports non-stop debugging of
40893 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40894 supports non-stop mode, it should report that to @value{GDBN} by including
40895 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40897 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40898 establishing a new connection with the stub. Entering non-stop mode
40899 does not alter the state of any currently-running threads, but targets
40900 must stop all threads in any already-attached processes when entering
40901 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40902 probe the target state after a mode change.
40904 In non-stop mode, when an attached process encounters an event that
40905 would otherwise be reported with a stop reply, it uses the
40906 asynchronous notification mechanism (@pxref{Notification Packets}) to
40907 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40908 in all processes are stopped when a stop reply is sent, in non-stop
40909 mode only the thread reporting the stop event is stopped. That is,
40910 when reporting a @samp{S} or @samp{T} response to indicate completion
40911 of a step operation, hitting a breakpoint, or a fault, only the
40912 affected thread is stopped; any other still-running threads continue
40913 to run. When reporting a @samp{W} or @samp{X} response, all running
40914 threads belonging to other attached processes continue to run.
40916 In non-stop mode, the target shall respond to the @samp{?} packet as
40917 follows. First, any incomplete stop reply notification/@samp{vStopped}
40918 sequence in progress is abandoned. The target must begin a new
40919 sequence reporting stop events for all stopped threads, whether or not
40920 it has previously reported those events to @value{GDBN}. The first
40921 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40922 subsequent stop replies are sent as responses to @samp{vStopped} packets
40923 using the mechanism described above. The target must not send
40924 asynchronous stop reply notifications until the sequence is complete.
40925 If all threads are running when the target receives the @samp{?} packet,
40926 or if the target is not attached to any process, it shall respond
40929 If the stub supports non-stop mode, it should also support the
40930 @samp{swbreak} stop reason if software breakpoints are supported, and
40931 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40932 (@pxref{swbreak stop reason}). This is because given the asynchronous
40933 nature of non-stop mode, between the time a thread hits a breakpoint
40934 and the time the event is finally processed by @value{GDBN}, the
40935 breakpoint may have already been removed from the target. Due to
40936 this, @value{GDBN} needs to be able to tell whether a trap stop was
40937 caused by a delayed breakpoint event, which should be ignored, as
40938 opposed to a random trap signal, which should be reported to the user.
40939 Note the @samp{swbreak} feature implies that the target is responsible
40940 for adjusting the PC when a software breakpoint triggers, if
40941 necessary, such as on the x86 architecture.
40943 @node Packet Acknowledgment
40944 @section Packet Acknowledgment
40946 @cindex acknowledgment, for @value{GDBN} remote
40947 @cindex packet acknowledgment, for @value{GDBN} remote
40948 By default, when either the host or the target machine receives a packet,
40949 the first response expected is an acknowledgment: either @samp{+} (to indicate
40950 the package was received correctly) or @samp{-} (to request retransmission).
40951 This mechanism allows the @value{GDBN} remote protocol to operate over
40952 unreliable transport mechanisms, such as a serial line.
40954 In cases where the transport mechanism is itself reliable (such as a pipe or
40955 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40956 It may be desirable to disable them in that case to reduce communication
40957 overhead, or for other reasons. This can be accomplished by means of the
40958 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40960 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40961 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40962 and response format still includes the normal checksum, as described in
40963 @ref{Overview}, but the checksum may be ignored by the receiver.
40965 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40966 no-acknowledgment mode, it should report that to @value{GDBN}
40967 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40968 @pxref{qSupported}.
40969 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40970 disabled via the @code{set remote noack-packet off} command
40971 (@pxref{Remote Configuration}),
40972 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40973 Only then may the stub actually turn off packet acknowledgments.
40974 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40975 response, which can be safely ignored by the stub.
40977 Note that @code{set remote noack-packet} command only affects negotiation
40978 between @value{GDBN} and the stub when subsequent connections are made;
40979 it does not affect the protocol acknowledgment state for any current
40981 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40982 new connection is established,
40983 there is also no protocol request to re-enable the acknowledgments
40984 for the current connection, once disabled.
40989 Example sequence of a target being re-started. Notice how the restart
40990 does not get any direct output:
40995 @emph{target restarts}
40998 <- @code{T001:1234123412341234}
41002 Example sequence of a target being stepped by a single instruction:
41005 -> @code{G1445@dots{}}
41010 <- @code{T001:1234123412341234}
41014 <- @code{1455@dots{}}
41018 @node File-I/O Remote Protocol Extension
41019 @section File-I/O Remote Protocol Extension
41020 @cindex File-I/O remote protocol extension
41023 * File-I/O Overview::
41024 * Protocol Basics::
41025 * The F Request Packet::
41026 * The F Reply Packet::
41027 * The Ctrl-C Message::
41029 * List of Supported Calls::
41030 * Protocol-specific Representation of Datatypes::
41032 * File-I/O Examples::
41035 @node File-I/O Overview
41036 @subsection File-I/O Overview
41037 @cindex file-i/o overview
41039 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41040 target to use the host's file system and console I/O to perform various
41041 system calls. System calls on the target system are translated into a
41042 remote protocol packet to the host system, which then performs the needed
41043 actions and returns a response packet to the target system.
41044 This simulates file system operations even on targets that lack file systems.
41046 The protocol is defined to be independent of both the host and target systems.
41047 It uses its own internal representation of datatypes and values. Both
41048 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41049 translating the system-dependent value representations into the internal
41050 protocol representations when data is transmitted.
41052 The communication is synchronous. A system call is possible only when
41053 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41054 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41055 the target is stopped to allow deterministic access to the target's
41056 memory. Therefore File-I/O is not interruptible by target signals. On
41057 the other hand, it is possible to interrupt File-I/O by a user interrupt
41058 (@samp{Ctrl-C}) within @value{GDBN}.
41060 The target's request to perform a host system call does not finish
41061 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41062 after finishing the system call, the target returns to continuing the
41063 previous activity (continue, step). No additional continue or step
41064 request from @value{GDBN} is required.
41067 (@value{GDBP}) continue
41068 <- target requests 'system call X'
41069 target is stopped, @value{GDBN} executes system call
41070 -> @value{GDBN} returns result
41071 ... target continues, @value{GDBN} returns to wait for the target
41072 <- target hits breakpoint and sends a Txx packet
41075 The protocol only supports I/O on the console and to regular files on
41076 the host file system. Character or block special devices, pipes,
41077 named pipes, sockets or any other communication method on the host
41078 system are not supported by this protocol.
41080 File I/O is not supported in non-stop mode.
41082 @node Protocol Basics
41083 @subsection Protocol Basics
41084 @cindex protocol basics, file-i/o
41086 The File-I/O protocol uses the @code{F} packet as the request as well
41087 as reply packet. Since a File-I/O system call can only occur when
41088 @value{GDBN} is waiting for a response from the continuing or stepping target,
41089 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41090 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41091 This @code{F} packet contains all information needed to allow @value{GDBN}
41092 to call the appropriate host system call:
41096 A unique identifier for the requested system call.
41099 All parameters to the system call. Pointers are given as addresses
41100 in the target memory address space. Pointers to strings are given as
41101 pointer/length pair. Numerical values are given as they are.
41102 Numerical control flags are given in a protocol-specific representation.
41106 At this point, @value{GDBN} has to perform the following actions.
41110 If the parameters include pointer values to data needed as input to a
41111 system call, @value{GDBN} requests this data from the target with a
41112 standard @code{m} packet request. This additional communication has to be
41113 expected by the target implementation and is handled as any other @code{m}
41117 @value{GDBN} translates all value from protocol representation to host
41118 representation as needed. Datatypes are coerced into the host types.
41121 @value{GDBN} calls the system call.
41124 It then coerces datatypes back to protocol representation.
41127 If the system call is expected to return data in buffer space specified
41128 by pointer parameters to the call, the data is transmitted to the
41129 target using a @code{M} or @code{X} packet. This packet has to be expected
41130 by the target implementation and is handled as any other @code{M} or @code{X}
41135 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41136 necessary information for the target to continue. This at least contains
41143 @code{errno}, if has been changed by the system call.
41150 After having done the needed type and value coercion, the target continues
41151 the latest continue or step action.
41153 @node The F Request Packet
41154 @subsection The @code{F} Request Packet
41155 @cindex file-i/o request packet
41156 @cindex @code{F} request packet
41158 The @code{F} request packet has the following format:
41161 @item F@var{call-id},@var{parameter@dots{}}
41163 @var{call-id} is the identifier to indicate the host system call to be called.
41164 This is just the name of the function.
41166 @var{parameter@dots{}} are the parameters to the system call.
41167 Parameters are hexadecimal integer values, either the actual values in case
41168 of scalar datatypes, pointers to target buffer space in case of compound
41169 datatypes and unspecified memory areas, or pointer/length pairs in case
41170 of string parameters. These are appended to the @var{call-id} as a
41171 comma-delimited list. All values are transmitted in ASCII
41172 string representation, pointer/length pairs separated by a slash.
41178 @node The F Reply Packet
41179 @subsection The @code{F} Reply Packet
41180 @cindex file-i/o reply packet
41181 @cindex @code{F} reply packet
41183 The @code{F} reply packet has the following format:
41187 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41189 @var{retcode} is the return code of the system call as hexadecimal value.
41191 @var{errno} is the @code{errno} set by the call, in protocol-specific
41193 This parameter can be omitted if the call was successful.
41195 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41196 case, @var{errno} must be sent as well, even if the call was successful.
41197 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41204 or, if the call was interrupted before the host call has been performed:
41211 assuming 4 is the protocol-specific representation of @code{EINTR}.
41216 @node The Ctrl-C Message
41217 @subsection The @samp{Ctrl-C} Message
41218 @cindex ctrl-c message, in file-i/o protocol
41220 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41221 reply packet (@pxref{The F Reply Packet}),
41222 the target should behave as if it had
41223 gotten a break message. The meaning for the target is ``system call
41224 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41225 (as with a break message) and return to @value{GDBN} with a @code{T02}
41228 It's important for the target to know in which
41229 state the system call was interrupted. There are two possible cases:
41233 The system call hasn't been performed on the host yet.
41236 The system call on the host has been finished.
41240 These two states can be distinguished by the target by the value of the
41241 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41242 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41243 on POSIX systems. In any other case, the target may presume that the
41244 system call has been finished --- successfully or not --- and should behave
41245 as if the break message arrived right after the system call.
41247 @value{GDBN} must behave reliably. If the system call has not been called
41248 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41249 @code{errno} in the packet. If the system call on the host has been finished
41250 before the user requests a break, the full action must be finished by
41251 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41252 The @code{F} packet may only be sent when either nothing has happened
41253 or the full action has been completed.
41256 @subsection Console I/O
41257 @cindex console i/o as part of file-i/o
41259 By default and if not explicitly closed by the target system, the file
41260 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41261 on the @value{GDBN} console is handled as any other file output operation
41262 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41263 by @value{GDBN} so that after the target read request from file descriptor
41264 0 all following typing is buffered until either one of the following
41269 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41271 system call is treated as finished.
41274 The user presses @key{RET}. This is treated as end of input with a trailing
41278 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41279 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41283 If the user has typed more characters than fit in the buffer given to
41284 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41285 either another @code{read(0, @dots{})} is requested by the target, or debugging
41286 is stopped at the user's request.
41289 @node List of Supported Calls
41290 @subsection List of Supported Calls
41291 @cindex list of supported file-i/o calls
41308 @unnumberedsubsubsec open
41309 @cindex open, file-i/o system call
41314 int open(const char *pathname, int flags);
41315 int open(const char *pathname, int flags, mode_t mode);
41319 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41322 @var{flags} is the bitwise @code{OR} of the following values:
41326 If the file does not exist it will be created. The host
41327 rules apply as far as file ownership and time stamps
41331 When used with @code{O_CREAT}, if the file already exists it is
41332 an error and open() fails.
41335 If the file already exists and the open mode allows
41336 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41337 truncated to zero length.
41340 The file is opened in append mode.
41343 The file is opened for reading only.
41346 The file is opened for writing only.
41349 The file is opened for reading and writing.
41353 Other bits are silently ignored.
41357 @var{mode} is the bitwise @code{OR} of the following values:
41361 User has read permission.
41364 User has write permission.
41367 Group has read permission.
41370 Group has write permission.
41373 Others have read permission.
41376 Others have write permission.
41380 Other bits are silently ignored.
41383 @item Return value:
41384 @code{open} returns the new file descriptor or -1 if an error
41391 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41394 @var{pathname} refers to a directory.
41397 The requested access is not allowed.
41400 @var{pathname} was too long.
41403 A directory component in @var{pathname} does not exist.
41406 @var{pathname} refers to a device, pipe, named pipe or socket.
41409 @var{pathname} refers to a file on a read-only filesystem and
41410 write access was requested.
41413 @var{pathname} is an invalid pointer value.
41416 No space on device to create the file.
41419 The process already has the maximum number of files open.
41422 The limit on the total number of files open on the system
41426 The call was interrupted by the user.
41432 @unnumberedsubsubsec close
41433 @cindex close, file-i/o system call
41442 @samp{Fclose,@var{fd}}
41444 @item Return value:
41445 @code{close} returns zero on success, or -1 if an error occurred.
41451 @var{fd} isn't a valid open file descriptor.
41454 The call was interrupted by the user.
41460 @unnumberedsubsubsec read
41461 @cindex read, file-i/o system call
41466 int read(int fd, void *buf, unsigned int count);
41470 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41472 @item Return value:
41473 On success, the number of bytes read is returned.
41474 Zero indicates end of file. If count is zero, read
41475 returns zero as well. On error, -1 is returned.
41481 @var{fd} is not a valid file descriptor or is not open for
41485 @var{bufptr} is an invalid pointer value.
41488 The call was interrupted by the user.
41494 @unnumberedsubsubsec write
41495 @cindex write, file-i/o system call
41500 int write(int fd, const void *buf, unsigned int count);
41504 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41506 @item Return value:
41507 On success, the number of bytes written are returned.
41508 Zero indicates nothing was written. On error, -1
41515 @var{fd} is not a valid file descriptor or is not open for
41519 @var{bufptr} is an invalid pointer value.
41522 An attempt was made to write a file that exceeds the
41523 host-specific maximum file size allowed.
41526 No space on device to write the data.
41529 The call was interrupted by the user.
41535 @unnumberedsubsubsec lseek
41536 @cindex lseek, file-i/o system call
41541 long lseek (int fd, long offset, int flag);
41545 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41547 @var{flag} is one of:
41551 The offset is set to @var{offset} bytes.
41554 The offset is set to its current location plus @var{offset}
41558 The offset is set to the size of the file plus @var{offset}
41562 @item Return value:
41563 On success, the resulting unsigned offset in bytes from
41564 the beginning of the file is returned. Otherwise, a
41565 value of -1 is returned.
41571 @var{fd} is not a valid open file descriptor.
41574 @var{fd} is associated with the @value{GDBN} console.
41577 @var{flag} is not a proper value.
41580 The call was interrupted by the user.
41586 @unnumberedsubsubsec rename
41587 @cindex rename, file-i/o system call
41592 int rename(const char *oldpath, const char *newpath);
41596 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41598 @item Return value:
41599 On success, zero is returned. On error, -1 is returned.
41605 @var{newpath} is an existing directory, but @var{oldpath} is not a
41609 @var{newpath} is a non-empty directory.
41612 @var{oldpath} or @var{newpath} is a directory that is in use by some
41616 An attempt was made to make a directory a subdirectory
41620 A component used as a directory in @var{oldpath} or new
41621 path is not a directory. Or @var{oldpath} is a directory
41622 and @var{newpath} exists but is not a directory.
41625 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41628 No access to the file or the path of the file.
41632 @var{oldpath} or @var{newpath} was too long.
41635 A directory component in @var{oldpath} or @var{newpath} does not exist.
41638 The file is on a read-only filesystem.
41641 The device containing the file has no room for the new
41645 The call was interrupted by the user.
41651 @unnumberedsubsubsec unlink
41652 @cindex unlink, file-i/o system call
41657 int unlink(const char *pathname);
41661 @samp{Funlink,@var{pathnameptr}/@var{len}}
41663 @item Return value:
41664 On success, zero is returned. On error, -1 is returned.
41670 No access to the file or the path of the file.
41673 The system does not allow unlinking of directories.
41676 The file @var{pathname} cannot be unlinked because it's
41677 being used by another process.
41680 @var{pathnameptr} is an invalid pointer value.
41683 @var{pathname} was too long.
41686 A directory component in @var{pathname} does not exist.
41689 A component of the path is not a directory.
41692 The file is on a read-only filesystem.
41695 The call was interrupted by the user.
41701 @unnumberedsubsubsec stat/fstat
41702 @cindex fstat, file-i/o system call
41703 @cindex stat, file-i/o system call
41708 int stat(const char *pathname, struct stat *buf);
41709 int fstat(int fd, struct stat *buf);
41713 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41714 @samp{Ffstat,@var{fd},@var{bufptr}}
41716 @item Return value:
41717 On success, zero is returned. On error, -1 is returned.
41723 @var{fd} is not a valid open file.
41726 A directory component in @var{pathname} does not exist or the
41727 path is an empty string.
41730 A component of the path is not a directory.
41733 @var{pathnameptr} is an invalid pointer value.
41736 No access to the file or the path of the file.
41739 @var{pathname} was too long.
41742 The call was interrupted by the user.
41748 @unnumberedsubsubsec gettimeofday
41749 @cindex gettimeofday, file-i/o system call
41754 int gettimeofday(struct timeval *tv, void *tz);
41758 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41760 @item Return value:
41761 On success, 0 is returned, -1 otherwise.
41767 @var{tz} is a non-NULL pointer.
41770 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41776 @unnumberedsubsubsec isatty
41777 @cindex isatty, file-i/o system call
41782 int isatty(int fd);
41786 @samp{Fisatty,@var{fd}}
41788 @item Return value:
41789 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41795 The call was interrupted by the user.
41800 Note that the @code{isatty} call is treated as a special case: it returns
41801 1 to the target if the file descriptor is attached
41802 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41803 would require implementing @code{ioctl} and would be more complex than
41808 @unnumberedsubsubsec system
41809 @cindex system, file-i/o system call
41814 int system(const char *command);
41818 @samp{Fsystem,@var{commandptr}/@var{len}}
41820 @item Return value:
41821 If @var{len} is zero, the return value indicates whether a shell is
41822 available. A zero return value indicates a shell is not available.
41823 For non-zero @var{len}, the value returned is -1 on error and the
41824 return status of the command otherwise. Only the exit status of the
41825 command is returned, which is extracted from the host's @code{system}
41826 return value by calling @code{WEXITSTATUS(retval)}. In case
41827 @file{/bin/sh} could not be executed, 127 is returned.
41833 The call was interrupted by the user.
41838 @value{GDBN} takes over the full task of calling the necessary host calls
41839 to perform the @code{system} call. The return value of @code{system} on
41840 the host is simplified before it's returned
41841 to the target. Any termination signal information from the child process
41842 is discarded, and the return value consists
41843 entirely of the exit status of the called command.
41845 Due to security concerns, the @code{system} call is by default refused
41846 by @value{GDBN}. The user has to allow this call explicitly with the
41847 @code{set remote system-call-allowed 1} command.
41850 @item set remote system-call-allowed
41851 @kindex set remote system-call-allowed
41852 Control whether to allow the @code{system} calls in the File I/O
41853 protocol for the remote target. The default is zero (disabled).
41855 @item show remote system-call-allowed
41856 @kindex show remote system-call-allowed
41857 Show whether the @code{system} calls are allowed in the File I/O
41861 @node Protocol-specific Representation of Datatypes
41862 @subsection Protocol-specific Representation of Datatypes
41863 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41866 * Integral Datatypes::
41868 * Memory Transfer::
41873 @node Integral Datatypes
41874 @unnumberedsubsubsec Integral Datatypes
41875 @cindex integral datatypes, in file-i/o protocol
41877 The integral datatypes used in the system calls are @code{int},
41878 @code{unsigned int}, @code{long}, @code{unsigned long},
41879 @code{mode_t}, and @code{time_t}.
41881 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41882 implemented as 32 bit values in this protocol.
41884 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41886 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41887 in @file{limits.h}) to allow range checking on host and target.
41889 @code{time_t} datatypes are defined as seconds since the Epoch.
41891 All integral datatypes transferred as part of a memory read or write of a
41892 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41895 @node Pointer Values
41896 @unnumberedsubsubsec Pointer Values
41897 @cindex pointer values, in file-i/o protocol
41899 Pointers to target data are transmitted as they are. An exception
41900 is made for pointers to buffers for which the length isn't
41901 transmitted as part of the function call, namely strings. Strings
41902 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41909 which is a pointer to data of length 18 bytes at position 0x1aaf.
41910 The length is defined as the full string length in bytes, including
41911 the trailing null byte. For example, the string @code{"hello world"}
41912 at address 0x123456 is transmitted as
41918 @node Memory Transfer
41919 @unnumberedsubsubsec Memory Transfer
41920 @cindex memory transfer, in file-i/o protocol
41922 Structured data which is transferred using a memory read or write (for
41923 example, a @code{struct stat}) is expected to be in a protocol-specific format
41924 with all scalar multibyte datatypes being big endian. Translation to
41925 this representation needs to be done both by the target before the @code{F}
41926 packet is sent, and by @value{GDBN} before
41927 it transfers memory to the target. Transferred pointers to structured
41928 data should point to the already-coerced data at any time.
41932 @unnumberedsubsubsec struct stat
41933 @cindex struct stat, in file-i/o protocol
41935 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41936 is defined as follows:
41940 unsigned int st_dev; /* device */
41941 unsigned int st_ino; /* inode */
41942 mode_t st_mode; /* protection */
41943 unsigned int st_nlink; /* number of hard links */
41944 unsigned int st_uid; /* user ID of owner */
41945 unsigned int st_gid; /* group ID of owner */
41946 unsigned int st_rdev; /* device type (if inode device) */
41947 unsigned long st_size; /* total size, in bytes */
41948 unsigned long st_blksize; /* blocksize for filesystem I/O */
41949 unsigned long st_blocks; /* number of blocks allocated */
41950 time_t st_atime; /* time of last access */
41951 time_t st_mtime; /* time of last modification */
41952 time_t st_ctime; /* time of last change */
41956 The integral datatypes conform to the definitions given in the
41957 appropriate section (see @ref{Integral Datatypes}, for details) so this
41958 structure is of size 64 bytes.
41960 The values of several fields have a restricted meaning and/or
41966 A value of 0 represents a file, 1 the console.
41969 No valid meaning for the target. Transmitted unchanged.
41972 Valid mode bits are described in @ref{Constants}. Any other
41973 bits have currently no meaning for the target.
41978 No valid meaning for the target. Transmitted unchanged.
41983 These values have a host and file system dependent
41984 accuracy. Especially on Windows hosts, the file system may not
41985 support exact timing values.
41988 The target gets a @code{struct stat} of the above representation and is
41989 responsible for coercing it to the target representation before
41992 Note that due to size differences between the host, target, and protocol
41993 representations of @code{struct stat} members, these members could eventually
41994 get truncated on the target.
41996 @node struct timeval
41997 @unnumberedsubsubsec struct timeval
41998 @cindex struct timeval, in file-i/o protocol
42000 The buffer of type @code{struct timeval} used by the File-I/O protocol
42001 is defined as follows:
42005 time_t tv_sec; /* second */
42006 long tv_usec; /* microsecond */
42010 The integral datatypes conform to the definitions given in the
42011 appropriate section (see @ref{Integral Datatypes}, for details) so this
42012 structure is of size 8 bytes.
42015 @subsection Constants
42016 @cindex constants, in file-i/o protocol
42018 The following values are used for the constants inside of the
42019 protocol. @value{GDBN} and target are responsible for translating these
42020 values before and after the call as needed.
42031 @unnumberedsubsubsec Open Flags
42032 @cindex open flags, in file-i/o protocol
42034 All values are given in hexadecimal representation.
42046 @node mode_t Values
42047 @unnumberedsubsubsec mode_t Values
42048 @cindex mode_t values, in file-i/o protocol
42050 All values are given in octal representation.
42067 @unnumberedsubsubsec Errno Values
42068 @cindex errno values, in file-i/o protocol
42070 All values are given in decimal representation.
42095 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42096 any error value not in the list of supported error numbers.
42099 @unnumberedsubsubsec Lseek Flags
42100 @cindex lseek flags, in file-i/o protocol
42109 @unnumberedsubsubsec Limits
42110 @cindex limits, in file-i/o protocol
42112 All values are given in decimal representation.
42115 INT_MIN -2147483648
42117 UINT_MAX 4294967295
42118 LONG_MIN -9223372036854775808
42119 LONG_MAX 9223372036854775807
42120 ULONG_MAX 18446744073709551615
42123 @node File-I/O Examples
42124 @subsection File-I/O Examples
42125 @cindex file-i/o examples
42127 Example sequence of a write call, file descriptor 3, buffer is at target
42128 address 0x1234, 6 bytes should be written:
42131 <- @code{Fwrite,3,1234,6}
42132 @emph{request memory read from target}
42135 @emph{return "6 bytes written"}
42139 Example sequence of a read call, file descriptor 3, buffer is at target
42140 address 0x1234, 6 bytes should be read:
42143 <- @code{Fread,3,1234,6}
42144 @emph{request memory write to target}
42145 -> @code{X1234,6:XXXXXX}
42146 @emph{return "6 bytes read"}
42150 Example sequence of a read call, call fails on the host due to invalid
42151 file descriptor (@code{EBADF}):
42154 <- @code{Fread,3,1234,6}
42158 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42162 <- @code{Fread,3,1234,6}
42167 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42171 <- @code{Fread,3,1234,6}
42172 -> @code{X1234,6:XXXXXX}
42176 @node Library List Format
42177 @section Library List Format
42178 @cindex library list format, remote protocol
42180 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42181 same process as your application to manage libraries. In this case,
42182 @value{GDBN} can use the loader's symbol table and normal memory
42183 operations to maintain a list of shared libraries. On other
42184 platforms, the operating system manages loaded libraries.
42185 @value{GDBN} can not retrieve the list of currently loaded libraries
42186 through memory operations, so it uses the @samp{qXfer:libraries:read}
42187 packet (@pxref{qXfer library list read}) instead. The remote stub
42188 queries the target's operating system and reports which libraries
42191 The @samp{qXfer:libraries:read} packet returns an XML document which
42192 lists loaded libraries and their offsets. Each library has an
42193 associated name and one or more segment or section base addresses,
42194 which report where the library was loaded in memory.
42196 For the common case of libraries that are fully linked binaries, the
42197 library should have a list of segments. If the target supports
42198 dynamic linking of a relocatable object file, its library XML element
42199 should instead include a list of allocated sections. The segment or
42200 section bases are start addresses, not relocation offsets; they do not
42201 depend on the library's link-time base addresses.
42203 @value{GDBN} must be linked with the Expat library to support XML
42204 library lists. @xref{Expat}.
42206 A simple memory map, with one loaded library relocated by a single
42207 offset, looks like this:
42211 <library name="/lib/libc.so.6">
42212 <segment address="0x10000000"/>
42217 Another simple memory map, with one loaded library with three
42218 allocated sections (.text, .data, .bss), looks like this:
42222 <library name="sharedlib.o">
42223 <section address="0x10000000"/>
42224 <section address="0x20000000"/>
42225 <section address="0x30000000"/>
42230 The format of a library list is described by this DTD:
42233 <!-- library-list: Root element with versioning -->
42234 <!ELEMENT library-list (library)*>
42235 <!ATTLIST library-list version CDATA #FIXED "1.0">
42236 <!ELEMENT library (segment*, section*)>
42237 <!ATTLIST library name CDATA #REQUIRED>
42238 <!ELEMENT segment EMPTY>
42239 <!ATTLIST segment address CDATA #REQUIRED>
42240 <!ELEMENT section EMPTY>
42241 <!ATTLIST section address CDATA #REQUIRED>
42244 In addition, segments and section descriptors cannot be mixed within a
42245 single library element, and you must supply at least one segment or
42246 section for each library.
42248 @node Library List Format for SVR4 Targets
42249 @section Library List Format for SVR4 Targets
42250 @cindex library list format, remote protocol
42252 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42253 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42254 shared libraries. Still a special library list provided by this packet is
42255 more efficient for the @value{GDBN} remote protocol.
42257 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42258 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42259 target, the following parameters are reported:
42263 @code{name}, the absolute file name from the @code{l_name} field of
42264 @code{struct link_map}.
42266 @code{lm} with address of @code{struct link_map} used for TLS
42267 (Thread Local Storage) access.
42269 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42270 @code{struct link_map}. For prelinked libraries this is not an absolute
42271 memory address. It is a displacement of absolute memory address against
42272 address the file was prelinked to during the library load.
42274 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42277 Additionally the single @code{main-lm} attribute specifies address of
42278 @code{struct link_map} used for the main executable. This parameter is used
42279 for TLS access and its presence is optional.
42281 @value{GDBN} must be linked with the Expat library to support XML
42282 SVR4 library lists. @xref{Expat}.
42284 A simple memory map, with two loaded libraries (which do not use prelink),
42288 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42289 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42291 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42293 </library-list-svr>
42296 The format of an SVR4 library list is described by this DTD:
42299 <!-- library-list-svr4: Root element with versioning -->
42300 <!ELEMENT library-list-svr4 (library)*>
42301 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42302 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42303 <!ELEMENT library EMPTY>
42304 <!ATTLIST library name CDATA #REQUIRED>
42305 <!ATTLIST library lm CDATA #REQUIRED>
42306 <!ATTLIST library l_addr CDATA #REQUIRED>
42307 <!ATTLIST library l_ld CDATA #REQUIRED>
42310 @node Memory Map Format
42311 @section Memory Map Format
42312 @cindex memory map format
42314 To be able to write into flash memory, @value{GDBN} needs to obtain a
42315 memory map from the target. This section describes the format of the
42318 The memory map is obtained using the @samp{qXfer:memory-map:read}
42319 (@pxref{qXfer memory map read}) packet and is an XML document that
42320 lists memory regions.
42322 @value{GDBN} must be linked with the Expat library to support XML
42323 memory maps. @xref{Expat}.
42325 The top-level structure of the document is shown below:
42328 <?xml version="1.0"?>
42329 <!DOCTYPE memory-map
42330 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42331 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42337 Each region can be either:
42342 A region of RAM starting at @var{addr} and extending for @var{length}
42346 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42351 A region of read-only memory:
42354 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42359 A region of flash memory, with erasure blocks @var{blocksize}
42363 <memory type="flash" start="@var{addr}" length="@var{length}">
42364 <property name="blocksize">@var{blocksize}</property>
42370 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42371 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42372 packets to write to addresses in such ranges.
42374 The formal DTD for memory map format is given below:
42377 <!-- ................................................... -->
42378 <!-- Memory Map XML DTD ................................ -->
42379 <!-- File: memory-map.dtd .............................. -->
42380 <!-- .................................... .............. -->
42381 <!-- memory-map.dtd -->
42382 <!-- memory-map: Root element with versioning -->
42383 <!ELEMENT memory-map (memory)*>
42384 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42385 <!ELEMENT memory (property)*>
42386 <!-- memory: Specifies a memory region,
42387 and its type, or device. -->
42388 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42389 start CDATA #REQUIRED
42390 length CDATA #REQUIRED>
42391 <!-- property: Generic attribute tag -->
42392 <!ELEMENT property (#PCDATA | property)*>
42393 <!ATTLIST property name (blocksize) #REQUIRED>
42396 @node Thread List Format
42397 @section Thread List Format
42398 @cindex thread list format
42400 To efficiently update the list of threads and their attributes,
42401 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42402 (@pxref{qXfer threads read}) and obtains the XML document with
42403 the following structure:
42406 <?xml version="1.0"?>
42408 <thread id="id" core="0" name="name">
42409 ... description ...
42414 Each @samp{thread} element must have the @samp{id} attribute that
42415 identifies the thread (@pxref{thread-id syntax}). The
42416 @samp{core} attribute, if present, specifies which processor core
42417 the thread was last executing on. The @samp{name} attribute, if
42418 present, specifies the human-readable name of the thread. The content
42419 of the of @samp{thread} element is interpreted as human-readable
42420 auxiliary information. The @samp{handle} attribute, if present,
42421 is a hex encoded representation of the thread handle.
42424 @node Traceframe Info Format
42425 @section Traceframe Info Format
42426 @cindex traceframe info format
42428 To be able to know which objects in the inferior can be examined when
42429 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42430 memory ranges, registers and trace state variables that have been
42431 collected in a traceframe.
42433 This list is obtained using the @samp{qXfer:traceframe-info:read}
42434 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42436 @value{GDBN} must be linked with the Expat library to support XML
42437 traceframe info discovery. @xref{Expat}.
42439 The top-level structure of the document is shown below:
42442 <?xml version="1.0"?>
42443 <!DOCTYPE traceframe-info
42444 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42445 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42451 Each traceframe block can be either:
42456 A region of collected memory starting at @var{addr} and extending for
42457 @var{length} bytes from there:
42460 <memory start="@var{addr}" length="@var{length}"/>
42464 A block indicating trace state variable numbered @var{number} has been
42468 <tvar id="@var{number}"/>
42473 The formal DTD for the traceframe info format is given below:
42476 <!ELEMENT traceframe-info (memory | tvar)* >
42477 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42479 <!ELEMENT memory EMPTY>
42480 <!ATTLIST memory start CDATA #REQUIRED
42481 length CDATA #REQUIRED>
42483 <!ATTLIST tvar id CDATA #REQUIRED>
42486 @node Branch Trace Format
42487 @section Branch Trace Format
42488 @cindex branch trace format
42490 In order to display the branch trace of an inferior thread,
42491 @value{GDBN} needs to obtain the list of branches. This list is
42492 represented as list of sequential code blocks that are connected via
42493 branches. The code in each block has been executed sequentially.
42495 This list is obtained using the @samp{qXfer:btrace:read}
42496 (@pxref{qXfer btrace read}) packet and is an XML document.
42498 @value{GDBN} must be linked with the Expat library to support XML
42499 traceframe info discovery. @xref{Expat}.
42501 The top-level structure of the document is shown below:
42504 <?xml version="1.0"?>
42506 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42507 "http://sourceware.org/gdb/gdb-btrace.dtd">
42516 A block of sequentially executed instructions starting at @var{begin}
42517 and ending at @var{end}:
42520 <block begin="@var{begin}" end="@var{end}"/>
42525 The formal DTD for the branch trace format is given below:
42528 <!ELEMENT btrace (block* | pt) >
42529 <!ATTLIST btrace version CDATA #FIXED "1.0">
42531 <!ELEMENT block EMPTY>
42532 <!ATTLIST block begin CDATA #REQUIRED
42533 end CDATA #REQUIRED>
42535 <!ELEMENT pt (pt-config?, raw?)>
42537 <!ELEMENT pt-config (cpu?)>
42539 <!ELEMENT cpu EMPTY>
42540 <!ATTLIST cpu vendor CDATA #REQUIRED
42541 family CDATA #REQUIRED
42542 model CDATA #REQUIRED
42543 stepping CDATA #REQUIRED>
42545 <!ELEMENT raw (#PCDATA)>
42548 @node Branch Trace Configuration Format
42549 @section Branch Trace Configuration Format
42550 @cindex branch trace configuration format
42552 For each inferior thread, @value{GDBN} can obtain the branch trace
42553 configuration using the @samp{qXfer:btrace-conf:read}
42554 (@pxref{qXfer btrace-conf read}) packet.
42556 The configuration describes the branch trace format and configuration
42557 settings for that format. The following information is described:
42561 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42564 The size of the @acronym{BTS} ring buffer in bytes.
42567 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42571 The size of the @acronym{Intel PT} ring buffer in bytes.
42575 @value{GDBN} must be linked with the Expat library to support XML
42576 branch trace configuration discovery. @xref{Expat}.
42578 The formal DTD for the branch trace configuration format is given below:
42581 <!ELEMENT btrace-conf (bts?, pt?)>
42582 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42584 <!ELEMENT bts EMPTY>
42585 <!ATTLIST bts size CDATA #IMPLIED>
42587 <!ELEMENT pt EMPTY>
42588 <!ATTLIST pt size CDATA #IMPLIED>
42591 @include agentexpr.texi
42593 @node Target Descriptions
42594 @appendix Target Descriptions
42595 @cindex target descriptions
42597 One of the challenges of using @value{GDBN} to debug embedded systems
42598 is that there are so many minor variants of each processor
42599 architecture in use. It is common practice for vendors to start with
42600 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42601 and then make changes to adapt it to a particular market niche. Some
42602 architectures have hundreds of variants, available from dozens of
42603 vendors. This leads to a number of problems:
42607 With so many different customized processors, it is difficult for
42608 the @value{GDBN} maintainers to keep up with the changes.
42610 Since individual variants may have short lifetimes or limited
42611 audiences, it may not be worthwhile to carry information about every
42612 variant in the @value{GDBN} source tree.
42614 When @value{GDBN} does support the architecture of the embedded system
42615 at hand, the task of finding the correct architecture name to give the
42616 @command{set architecture} command can be error-prone.
42619 To address these problems, the @value{GDBN} remote protocol allows a
42620 target system to not only identify itself to @value{GDBN}, but to
42621 actually describe its own features. This lets @value{GDBN} support
42622 processor variants it has never seen before --- to the extent that the
42623 descriptions are accurate, and that @value{GDBN} understands them.
42625 @value{GDBN} must be linked with the Expat library to support XML
42626 target descriptions. @xref{Expat}.
42629 * Retrieving Descriptions:: How descriptions are fetched from a target.
42630 * Target Description Format:: The contents of a target description.
42631 * Predefined Target Types:: Standard types available for target
42633 * Enum Target Types:: How to define enum target types.
42634 * Standard Target Features:: Features @value{GDBN} knows about.
42637 @node Retrieving Descriptions
42638 @section Retrieving Descriptions
42640 Target descriptions can be read from the target automatically, or
42641 specified by the user manually. The default behavior is to read the
42642 description from the target. @value{GDBN} retrieves it via the remote
42643 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42644 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42645 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42646 XML document, of the form described in @ref{Target Description
42649 Alternatively, you can specify a file to read for the target description.
42650 If a file is set, the target will not be queried. The commands to
42651 specify a file are:
42654 @cindex set tdesc filename
42655 @item set tdesc filename @var{path}
42656 Read the target description from @var{path}.
42658 @cindex unset tdesc filename
42659 @item unset tdesc filename
42660 Do not read the XML target description from a file. @value{GDBN}
42661 will use the description supplied by the current target.
42663 @cindex show tdesc filename
42664 @item show tdesc filename
42665 Show the filename to read for a target description, if any.
42669 @node Target Description Format
42670 @section Target Description Format
42671 @cindex target descriptions, XML format
42673 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42674 document which complies with the Document Type Definition provided in
42675 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42676 means you can use generally available tools like @command{xmllint} to
42677 check that your feature descriptions are well-formed and valid.
42678 However, to help people unfamiliar with XML write descriptions for
42679 their targets, we also describe the grammar here.
42681 Target descriptions can identify the architecture of the remote target
42682 and (for some architectures) provide information about custom register
42683 sets. They can also identify the OS ABI of the remote target.
42684 @value{GDBN} can use this information to autoconfigure for your
42685 target, or to warn you if you connect to an unsupported target.
42687 Here is a simple target description:
42690 <target version="1.0">
42691 <architecture>i386:x86-64</architecture>
42696 This minimal description only says that the target uses
42697 the x86-64 architecture.
42699 A target description has the following overall form, with [ ] marking
42700 optional elements and @dots{} marking repeatable elements. The elements
42701 are explained further below.
42704 <?xml version="1.0"?>
42705 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42706 <target version="1.0">
42707 @r{[}@var{architecture}@r{]}
42708 @r{[}@var{osabi}@r{]}
42709 @r{[}@var{compatible}@r{]}
42710 @r{[}@var{feature}@dots{}@r{]}
42715 The description is generally insensitive to whitespace and line
42716 breaks, under the usual common-sense rules. The XML version
42717 declaration and document type declaration can generally be omitted
42718 (@value{GDBN} does not require them), but specifying them may be
42719 useful for XML validation tools. The @samp{version} attribute for
42720 @samp{<target>} may also be omitted, but we recommend
42721 including it; if future versions of @value{GDBN} use an incompatible
42722 revision of @file{gdb-target.dtd}, they will detect and report
42723 the version mismatch.
42725 @subsection Inclusion
42726 @cindex target descriptions, inclusion
42729 @cindex <xi:include>
42732 It can sometimes be valuable to split a target description up into
42733 several different annexes, either for organizational purposes, or to
42734 share files between different possible target descriptions. You can
42735 divide a description into multiple files by replacing any element of
42736 the target description with an inclusion directive of the form:
42739 <xi:include href="@var{document}"/>
42743 When @value{GDBN} encounters an element of this form, it will retrieve
42744 the named XML @var{document}, and replace the inclusion directive with
42745 the contents of that document. If the current description was read
42746 using @samp{qXfer}, then so will be the included document;
42747 @var{document} will be interpreted as the name of an annex. If the
42748 current description was read from a file, @value{GDBN} will look for
42749 @var{document} as a file in the same directory where it found the
42750 original description.
42752 @subsection Architecture
42753 @cindex <architecture>
42755 An @samp{<architecture>} element has this form:
42758 <architecture>@var{arch}</architecture>
42761 @var{arch} is one of the architectures from the set accepted by
42762 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42765 @cindex @code{<osabi>}
42767 This optional field was introduced in @value{GDBN} version 7.0.
42768 Previous versions of @value{GDBN} ignore it.
42770 An @samp{<osabi>} element has this form:
42773 <osabi>@var{abi-name}</osabi>
42776 @var{abi-name} is an OS ABI name from the same selection accepted by
42777 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42779 @subsection Compatible Architecture
42780 @cindex @code{<compatible>}
42782 This optional field was introduced in @value{GDBN} version 7.0.
42783 Previous versions of @value{GDBN} ignore it.
42785 A @samp{<compatible>} element has this form:
42788 <compatible>@var{arch}</compatible>
42791 @var{arch} is one of the architectures from the set accepted by
42792 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42794 A @samp{<compatible>} element is used to specify that the target
42795 is able to run binaries in some other than the main target architecture
42796 given by the @samp{<architecture>} element. For example, on the
42797 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42798 or @code{powerpc:common64}, but the system is able to run binaries
42799 in the @code{spu} architecture as well. The way to describe this
42800 capability with @samp{<compatible>} is as follows:
42803 <architecture>powerpc:common</architecture>
42804 <compatible>spu</compatible>
42807 @subsection Features
42810 Each @samp{<feature>} describes some logical portion of the target
42811 system. Features are currently used to describe available CPU
42812 registers and the types of their contents. A @samp{<feature>} element
42816 <feature name="@var{name}">
42817 @r{[}@var{type}@dots{}@r{]}
42823 Each feature's name should be unique within the description. The name
42824 of a feature does not matter unless @value{GDBN} has some special
42825 knowledge of the contents of that feature; if it does, the feature
42826 should have its standard name. @xref{Standard Target Features}.
42830 Any register's value is a collection of bits which @value{GDBN} must
42831 interpret. The default interpretation is a two's complement integer,
42832 but other types can be requested by name in the register description.
42833 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42834 Target Types}), and the description can define additional composite
42837 Each type element must have an @samp{id} attribute, which gives
42838 a unique (within the containing @samp{<feature>}) name to the type.
42839 Types must be defined before they are used.
42842 Some targets offer vector registers, which can be treated as arrays
42843 of scalar elements. These types are written as @samp{<vector>} elements,
42844 specifying the array element type, @var{type}, and the number of elements,
42848 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42852 If a register's value is usefully viewed in multiple ways, define it
42853 with a union type containing the useful representations. The
42854 @samp{<union>} element contains one or more @samp{<field>} elements,
42855 each of which has a @var{name} and a @var{type}:
42858 <union id="@var{id}">
42859 <field name="@var{name}" type="@var{type}"/>
42866 If a register's value is composed from several separate values, define
42867 it with either a structure type or a flags type.
42868 A flags type may only contain bitfields.
42869 A structure type may either contain only bitfields or contain no bitfields.
42870 If the value contains only bitfields, its total size in bytes must be
42873 Non-bitfield values have a @var{name} and @var{type}.
42876 <struct id="@var{id}">
42877 <field name="@var{name}" type="@var{type}"/>
42882 Both @var{name} and @var{type} values are required.
42883 No implicit padding is added.
42885 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42888 <struct id="@var{id}" size="@var{size}">
42889 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42895 <flags id="@var{id}" size="@var{size}">
42896 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42901 The @var{name} value is required.
42902 Bitfield values may be named with the empty string, @samp{""},
42903 in which case the field is ``filler'' and its value is not printed.
42904 Not all bits need to be specified, so ``filler'' fields are optional.
42906 The @var{start} and @var{end} values are required, and @var{type}
42908 The field's @var{start} must be less than or equal to its @var{end},
42909 and zero represents the least significant bit.
42911 The default value of @var{type} is @code{bool} for single bit fields,
42912 and an unsigned integer otherwise.
42914 Which to choose? Structures or flags?
42916 Registers defined with @samp{flags} have these advantages over
42917 defining them with @samp{struct}:
42921 Arithmetic may be performed on them as if they were integers.
42923 They are printed in a more readable fashion.
42926 Registers defined with @samp{struct} have one advantage over
42927 defining them with @samp{flags}:
42931 One can fetch individual fields like in @samp{C}.
42934 (gdb) print $my_struct_reg.field3
42940 @subsection Registers
42943 Each register is represented as an element with this form:
42946 <reg name="@var{name}"
42947 bitsize="@var{size}"
42948 @r{[}regnum="@var{num}"@r{]}
42949 @r{[}save-restore="@var{save-restore}"@r{]}
42950 @r{[}type="@var{type}"@r{]}
42951 @r{[}group="@var{group}"@r{]}/>
42955 The components are as follows:
42960 The register's name; it must be unique within the target description.
42963 The register's size, in bits.
42966 The register's number. If omitted, a register's number is one greater
42967 than that of the previous register (either in the current feature or in
42968 a preceding feature); the first register in the target description
42969 defaults to zero. This register number is used to read or write
42970 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42971 packets, and registers appear in the @code{g} and @code{G} packets
42972 in order of increasing register number.
42975 Whether the register should be preserved across inferior function
42976 calls; this must be either @code{yes} or @code{no}. The default is
42977 @code{yes}, which is appropriate for most registers except for
42978 some system control registers; this is not related to the target's
42982 The type of the register. It may be a predefined type, a type
42983 defined in the current feature, or one of the special types @code{int}
42984 and @code{float}. @code{int} is an integer type of the correct size
42985 for @var{bitsize}, and @code{float} is a floating point type (in the
42986 architecture's normal floating point format) of the correct size for
42987 @var{bitsize}. The default is @code{int}.
42990 The register group to which this register belongs. It can be one of the
42991 standard register groups @code{general}, @code{float}, @code{vector} or an
42992 arbitrary string. Group names should be limited to alphanumeric characters.
42993 If a group name is made up of multiple words the words may be separated by
42994 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
42995 @var{group} is specified, @value{GDBN} will not display the register in
42996 @code{info registers}.
43000 @node Predefined Target Types
43001 @section Predefined Target Types
43002 @cindex target descriptions, predefined types
43004 Type definitions in the self-description can build up composite types
43005 from basic building blocks, but can not define fundamental types. Instead,
43006 standard identifiers are provided by @value{GDBN} for the fundamental
43007 types. The currently supported types are:
43012 Boolean type, occupying a single bit.
43020 Signed integer types holding the specified number of bits.
43028 Unsigned integer types holding the specified number of bits.
43032 Pointers to unspecified code and data. The program counter and
43033 any dedicated return address register may be marked as code
43034 pointers; printing a code pointer converts it into a symbolic
43035 address. The stack pointer and any dedicated address registers
43036 may be marked as data pointers.
43039 Single precision IEEE floating point.
43042 Double precision IEEE floating point.
43045 The 12-byte extended precision format used by ARM FPA registers.
43048 The 10-byte extended precision format used by x87 registers.
43051 32bit @sc{eflags} register used by x86.
43054 32bit @sc{mxcsr} register used by x86.
43058 @node Enum Target Types
43059 @section Enum Target Types
43060 @cindex target descriptions, enum types
43062 Enum target types are useful in @samp{struct} and @samp{flags}
43063 register descriptions. @xref{Target Description Format}.
43065 Enum types have a name, size and a list of name/value pairs.
43068 <enum id="@var{id}" size="@var{size}">
43069 <evalue name="@var{name}" value="@var{value}"/>
43074 Enums must be defined before they are used.
43077 <enum id="levels_type" size="4">
43078 <evalue name="low" value="0"/>
43079 <evalue name="high" value="1"/>
43081 <flags id="flags_type" size="4">
43082 <field name="X" start="0"/>
43083 <field name="LEVEL" start="1" end="1" type="levels_type"/>
43085 <reg name="flags" bitsize="32" type="flags_type"/>
43088 Given that description, a value of 3 for the @samp{flags} register
43089 would be printed as:
43092 (gdb) info register flags
43093 flags 0x3 [ X LEVEL=high ]
43096 @node Standard Target Features
43097 @section Standard Target Features
43098 @cindex target descriptions, standard features
43100 A target description must contain either no registers or all the
43101 target's registers. If the description contains no registers, then
43102 @value{GDBN} will assume a default register layout, selected based on
43103 the architecture. If the description contains any registers, the
43104 default layout will not be used; the standard registers must be
43105 described in the target description, in such a way that @value{GDBN}
43106 can recognize them.
43108 This is accomplished by giving specific names to feature elements
43109 which contain standard registers. @value{GDBN} will look for features
43110 with those names and verify that they contain the expected registers;
43111 if any known feature is missing required registers, or if any required
43112 feature is missing, @value{GDBN} will reject the target
43113 description. You can add additional registers to any of the
43114 standard features --- @value{GDBN} will display them just as if
43115 they were added to an unrecognized feature.
43117 This section lists the known features and their expected contents.
43118 Sample XML documents for these features are included in the
43119 @value{GDBN} source tree, in the directory @file{gdb/features}.
43121 Names recognized by @value{GDBN} should include the name of the
43122 company or organization which selected the name, and the overall
43123 architecture to which the feature applies; so e.g.@: the feature
43124 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43126 The names of registers are not case sensitive for the purpose
43127 of recognizing standard features, but @value{GDBN} will only display
43128 registers using the capitalization used in the description.
43131 * AArch64 Features::
43135 * MicroBlaze Features::
43139 * Nios II Features::
43140 * OpenRISC 1000 Features::
43141 * PowerPC Features::
43142 * RISC-V Features::
43143 * S/390 and System z Features::
43149 @node AArch64 Features
43150 @subsection AArch64 Features
43151 @cindex target descriptions, AArch64 features
43153 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43154 targets. It should contain registers @samp{x0} through @samp{x30},
43155 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43157 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43158 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43161 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
43162 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
43163 through @samp{p15}, @samp{ffr} and @samp{vg}.
43165 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
43166 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
43169 @subsection ARC Features
43170 @cindex target descriptions, ARC Features
43172 ARC processors are highly configurable, so even core registers and their number
43173 are not completely predetermined. In addition flags and PC registers which are
43174 important to @value{GDBN} are not ``core'' registers in ARC. It is required
43175 that one of the core registers features is present.
43176 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
43178 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
43179 targets with a normal register file. It should contain registers @samp{r0}
43180 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43181 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
43182 and any of extension core registers @samp{r32} through @samp{r59/acch}.
43183 @samp{ilink} and extension core registers are not available to read/write, when
43184 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
43186 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
43187 ARC HS targets with a reduced register file. It should contain registers
43188 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
43189 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
43190 This feature may contain register @samp{ilink} and any of extension core
43191 registers @samp{r32} through @samp{r59/acch}.
43193 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
43194 targets with a normal register file. It should contain registers @samp{r0}
43195 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43196 @samp{lp_count} and @samp{pcl}. This feature may contain registers
43197 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43198 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43199 registers are not available when debugging GNU/Linux applications. The only
43200 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43201 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43202 ARC v2, but @samp{ilink2} is optional on ARCompact.
43204 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43205 targets. It should contain registers @samp{pc} and @samp{status32}.
43208 @subsection ARM Features
43209 @cindex target descriptions, ARM features
43211 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43213 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43214 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43216 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43217 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43218 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43221 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43222 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43224 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43225 it should contain at least registers @samp{wR0} through @samp{wR15} and
43226 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43227 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43229 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43230 should contain at least registers @samp{d0} through @samp{d15}. If
43231 they are present, @samp{d16} through @samp{d31} should also be included.
43232 @value{GDBN} will synthesize the single-precision registers from
43233 halves of the double-precision registers.
43235 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43236 need to contain registers; it instructs @value{GDBN} to display the
43237 VFP double-precision registers as vectors and to synthesize the
43238 quad-precision registers from pairs of double-precision registers.
43239 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43240 be present and include 32 double-precision registers.
43242 @node i386 Features
43243 @subsection i386 Features
43244 @cindex target descriptions, i386 features
43246 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43247 targets. It should describe the following registers:
43251 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43253 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43255 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43256 @samp{fs}, @samp{gs}
43258 @samp{st0} through @samp{st7}
43260 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43261 @samp{foseg}, @samp{fooff} and @samp{fop}
43264 The register sets may be different, depending on the target.
43266 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43267 describe registers:
43271 @samp{xmm0} through @samp{xmm7} for i386
43273 @samp{xmm0} through @samp{xmm15} for amd64
43278 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43279 @samp{org.gnu.gdb.i386.sse} feature. It should
43280 describe the upper 128 bits of @sc{ymm} registers:
43284 @samp{ymm0h} through @samp{ymm7h} for i386
43286 @samp{ymm0h} through @samp{ymm15h} for amd64
43289 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43290 Memory Protection Extension (MPX). It should describe the following registers:
43294 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43296 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43299 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43300 describe a single register, @samp{orig_eax}.
43302 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43303 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43305 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43306 @samp{org.gnu.gdb.i386.avx} feature. It should
43307 describe additional @sc{xmm} registers:
43311 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43314 It should describe the upper 128 bits of additional @sc{ymm} registers:
43318 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43322 describe the upper 256 bits of @sc{zmm} registers:
43326 @samp{zmm0h} through @samp{zmm7h} for i386.
43328 @samp{zmm0h} through @samp{zmm15h} for amd64.
43332 describe the additional @sc{zmm} registers:
43336 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43339 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43340 describe a single register, @samp{pkru}. It is a 32-bit register
43341 valid for i386 and amd64.
43343 @node MicroBlaze Features
43344 @subsection MicroBlaze Features
43345 @cindex target descriptions, MicroBlaze features
43347 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43348 targets. It should contain registers @samp{r0} through @samp{r31},
43349 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43350 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43351 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43353 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43354 If present, it should contain registers @samp{rshr} and @samp{rslr}
43356 @node MIPS Features
43357 @subsection @acronym{MIPS} Features
43358 @cindex target descriptions, @acronym{MIPS} features
43360 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43361 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43362 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43365 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43366 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43367 registers. They may be 32-bit or 64-bit depending on the target.
43369 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43370 it may be optional in a future version of @value{GDBN}. It should
43371 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43372 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43374 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43375 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43376 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43377 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43379 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43380 contain a single register, @samp{restart}, which is used by the
43381 Linux kernel to control restartable syscalls.
43383 @node M68K Features
43384 @subsection M68K Features
43385 @cindex target descriptions, M68K features
43388 @item @samp{org.gnu.gdb.m68k.core}
43389 @itemx @samp{org.gnu.gdb.coldfire.core}
43390 @itemx @samp{org.gnu.gdb.fido.core}
43391 One of those features must be always present.
43392 The feature that is present determines which flavor of m68k is
43393 used. The feature that is present should contain registers
43394 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43395 @samp{sp}, @samp{ps} and @samp{pc}.
43397 @item @samp{org.gnu.gdb.coldfire.fp}
43398 This feature is optional. If present, it should contain registers
43399 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43403 @node NDS32 Features
43404 @subsection NDS32 Features
43405 @cindex target descriptions, NDS32 features
43407 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43408 targets. It should contain at least registers @samp{r0} through
43409 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43412 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43413 it should contain 64-bit double-precision floating-point registers
43414 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43415 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43417 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43418 registers are overlapped with the thirty-two 32-bit single-precision
43419 floating-point registers. The 32-bit single-precision registers, if
43420 not being listed explicitly, will be synthesized from halves of the
43421 overlapping 64-bit double-precision registers. Listing 32-bit
43422 single-precision registers explicitly is deprecated, and the
43423 support to it could be totally removed some day.
43425 @node Nios II Features
43426 @subsection Nios II Features
43427 @cindex target descriptions, Nios II features
43429 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43430 targets. It should contain the 32 core registers (@samp{zero},
43431 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43432 @samp{pc}, and the 16 control registers (@samp{status} through
43435 @node OpenRISC 1000 Features
43436 @subsection Openrisc 1000 Features
43437 @cindex target descriptions, OpenRISC 1000 features
43439 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43440 targets. It should contain the 32 general purpose registers (@samp{r0}
43441 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43443 @node PowerPC Features
43444 @subsection PowerPC Features
43445 @cindex target descriptions, PowerPC features
43447 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43448 targets. It should contain registers @samp{r0} through @samp{r31},
43449 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43450 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43452 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43453 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43455 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43456 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
43457 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
43458 through @samp{v31} as aliases for the corresponding @samp{vrX}
43461 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43462 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
43463 combine these registers with the floating point registers (@samp{f0}
43464 through @samp{f31}) and the altivec registers (@samp{vr0} through
43465 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
43466 @samp{vs63}, the set of vector-scalar registers for POWER7.
43467 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
43468 @samp{org.gnu.gdb.power.altivec}.
43470 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43471 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43472 @samp{spefscr}. SPE targets should provide 32-bit registers in
43473 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43474 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43475 these to present registers @samp{ev0} through @samp{ev31} to the
43478 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43479 contain the 64-bit register @samp{ppr}.
43481 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43482 contain the 64-bit register @samp{dscr}.
43484 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43485 contain the 64-bit register @samp{tar}.
43487 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43488 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43491 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43492 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43493 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43494 server PMU registers provided by @sc{gnu}/Linux.
43496 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43497 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43500 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43501 contain the checkpointed general-purpose registers @samp{cr0} through
43502 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43503 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43504 depending on the target. It should also contain the checkpointed
43505 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43508 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43509 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43510 through @samp{cf31}, as well as the checkpointed 64-bit register
43513 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43514 should contain the checkpointed altivec registers @samp{cvr0} through
43515 @samp{cvr31}, all 128-bit wide. It should also contain the
43516 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43519 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43520 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43521 will combine these registers with the checkpointed floating point
43522 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43523 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43524 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43525 @samp{cvs63}. Therefore, this feature requires both
43526 @samp{org.gnu.gdb.power.htm.altivec} and
43527 @samp{org.gnu.gdb.power.htm.fpu}.
43529 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43530 contain the 64-bit checkpointed register @samp{cppr}.
43532 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43533 contain the 64-bit checkpointed register @samp{cdscr}.
43535 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43536 contain the 64-bit checkpointed register @samp{ctar}.
43539 @node RISC-V Features
43540 @subsection RISC-V Features
43541 @cindex target descriptions, RISC-V Features
43543 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
43544 targets. It should contain the registers @samp{x0} through
43545 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
43546 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
43549 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
43550 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
43551 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
43552 architectural register names, or the ABI names can be used.
43554 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
43555 it should contain registers that are not backed by real registers on
43556 the target, but are instead virtual, where the register value is
43557 derived from other target state. In many ways these are like
43558 @value{GDBN}s pseudo-registers, except implemented by the target.
43559 Currently the only register expected in this set is the one byte
43560 @samp{priv} register that contains the target's privilege level in the
43561 least significant two bits.
43563 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
43564 should contain all of the target's standard CSRs. Standard CSRs are
43565 those defined in the RISC-V specification documents. There is some
43566 overlap between this feature and the fpu feature; the @samp{fflags},
43567 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
43568 expectation is that these registers will be in the fpu feature if the
43569 target has floating point hardware, but can be moved into the csr
43570 feature if the target has the floating point control registers, but no
43571 other floating point hardware.
43573 @node S/390 and System z Features
43574 @subsection S/390 and System z Features
43575 @cindex target descriptions, S/390 features
43576 @cindex target descriptions, System z features
43578 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43579 System z targets. It should contain the PSW and the 16 general
43580 registers. In particular, System z targets should provide the 64-bit
43581 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43582 S/390 targets should provide the 32-bit versions of these registers.
43583 A System z target that runs in 31-bit addressing mode should provide
43584 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43585 register's upper halves @samp{r0h} through @samp{r15h}, and their
43586 lower halves @samp{r0l} through @samp{r15l}.
43588 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43589 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43592 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43593 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43595 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43596 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43597 targets and 32-bit otherwise. In addition, the feature may contain
43598 the @samp{last_break} register, whose width depends on the addressing
43599 mode, as well as the @samp{system_call} register, which is always
43602 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43603 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43604 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43606 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43607 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43608 combined by @value{GDBN} with the floating point registers @samp{f0}
43609 through @samp{f15} to present the 128-bit wide vector registers
43610 @samp{v0} through @samp{v15}. In addition, this feature should
43611 contain the 128-bit wide vector registers @samp{v16} through
43614 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43615 the 64-bit wide guarded-storage-control registers @samp{gsd},
43616 @samp{gssm}, and @samp{gsepla}.
43618 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43619 the 64-bit wide guarded-storage broadcast control registers
43620 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43622 @node Sparc Features
43623 @subsection Sparc Features
43624 @cindex target descriptions, sparc32 features
43625 @cindex target descriptions, sparc64 features
43626 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43627 targets. It should describe the following registers:
43631 @samp{g0} through @samp{g7}
43633 @samp{o0} through @samp{o7}
43635 @samp{l0} through @samp{l7}
43637 @samp{i0} through @samp{i7}
43640 They may be 32-bit or 64-bit depending on the target.
43642 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43643 targets. It should describe the following registers:
43647 @samp{f0} through @samp{f31}
43649 @samp{f32} through @samp{f62} for sparc64
43652 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43653 targets. It should describe the following registers:
43657 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43658 @samp{fsr}, and @samp{csr} for sparc32
43660 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43664 @node TIC6x Features
43665 @subsection TMS320C6x Features
43666 @cindex target descriptions, TIC6x features
43667 @cindex target descriptions, TMS320C6x features
43668 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43669 targets. It should contain registers @samp{A0} through @samp{A15},
43670 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43672 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43673 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43674 through @samp{B31}.
43676 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43677 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43679 @node Operating System Information
43680 @appendix Operating System Information
43681 @cindex operating system information
43687 Users of @value{GDBN} often wish to obtain information about the state of
43688 the operating system running on the target---for example the list of
43689 processes, or the list of open files. This section describes the
43690 mechanism that makes it possible. This mechanism is similar to the
43691 target features mechanism (@pxref{Target Descriptions}), but focuses
43692 on a different aspect of target.
43694 Operating system information is retrived from the target via the
43695 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43696 read}). The object name in the request should be @samp{osdata}, and
43697 the @var{annex} identifies the data to be fetched.
43700 @appendixsection Process list
43701 @cindex operating system information, process list
43703 When requesting the process list, the @var{annex} field in the
43704 @samp{qXfer} request should be @samp{processes}. The returned data is
43705 an XML document. The formal syntax of this document is defined in
43706 @file{gdb/features/osdata.dtd}.
43708 An example document is:
43711 <?xml version="1.0"?>
43712 <!DOCTYPE target SYSTEM "osdata.dtd">
43713 <osdata type="processes">
43715 <column name="pid">1</column>
43716 <column name="user">root</column>
43717 <column name="command">/sbin/init</column>
43718 <column name="cores">1,2,3</column>
43723 Each item should include a column whose name is @samp{pid}. The value
43724 of that column should identify the process on the target. The
43725 @samp{user} and @samp{command} columns are optional, and will be
43726 displayed by @value{GDBN}. The @samp{cores} column, if present,
43727 should contain a comma-separated list of cores that this process
43728 is running on. Target may provide additional columns,
43729 which @value{GDBN} currently ignores.
43731 @node Trace File Format
43732 @appendix Trace File Format
43733 @cindex trace file format
43735 The trace file comes in three parts: a header, a textual description
43736 section, and a trace frame section with binary data.
43738 The header has the form @code{\x7fTRACE0\n}. The first byte is
43739 @code{0x7f} so as to indicate that the file contains binary data,
43740 while the @code{0} is a version number that may have different values
43743 The description section consists of multiple lines of @sc{ascii} text
43744 separated by newline characters (@code{0xa}). The lines may include a
43745 variety of optional descriptive or context-setting information, such
43746 as tracepoint definitions or register set size. @value{GDBN} will
43747 ignore any line that it does not recognize. An empty line marks the end
43752 Specifies the size of a register block in bytes. This is equal to the
43753 size of a @code{g} packet payload in the remote protocol. @var{size}
43754 is an ascii decimal number. There should be only one such line in
43755 a single trace file.
43757 @item status @var{status}
43758 Trace status. @var{status} has the same format as a @code{qTStatus}
43759 remote packet reply. There should be only one such line in a single trace
43762 @item tp @var{payload}
43763 Tracepoint definition. The @var{payload} has the same format as
43764 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43765 may take multiple lines of definition, corresponding to the multiple
43768 @item tsv @var{payload}
43769 Trace state variable definition. The @var{payload} has the same format as
43770 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43771 may take multiple lines of definition, corresponding to the multiple
43774 @item tdesc @var{payload}
43775 Target description in XML format. The @var{payload} is a single line of
43776 the XML file. All such lines should be concatenated together to get
43777 the original XML file. This file is in the same format as @code{qXfer}
43778 @code{features} payload, and corresponds to the main @code{target.xml}
43779 file. Includes are not allowed.
43783 The trace frame section consists of a number of consecutive frames.
43784 Each frame begins with a two-byte tracepoint number, followed by a
43785 four-byte size giving the amount of data in the frame. The data in
43786 the frame consists of a number of blocks, each introduced by a
43787 character indicating its type (at least register, memory, and trace
43788 state variable). The data in this section is raw binary, not a
43789 hexadecimal or other encoding; its endianness matches the target's
43792 @c FIXME bi-arch may require endianness/arch info in description section
43795 @item R @var{bytes}
43796 Register block. The number and ordering of bytes matches that of a
43797 @code{g} packet in the remote protocol. Note that these are the
43798 actual bytes, in target order, not a hexadecimal encoding.
43800 @item M @var{address} @var{length} @var{bytes}...
43801 Memory block. This is a contiguous block of memory, at the 8-byte
43802 address @var{address}, with a 2-byte length @var{length}, followed by
43803 @var{length} bytes.
43805 @item V @var{number} @var{value}
43806 Trace state variable block. This records the 8-byte signed value
43807 @var{value} of trace state variable numbered @var{number}.
43811 Future enhancements of the trace file format may include additional types
43814 @node Index Section Format
43815 @appendix @code{.gdb_index} section format
43816 @cindex .gdb_index section format
43817 @cindex index section format
43819 This section documents the index section that is created by @code{save
43820 gdb-index} (@pxref{Index Files}). The index section is
43821 DWARF-specific; some knowledge of DWARF is assumed in this
43824 The mapped index file format is designed to be directly
43825 @code{mmap}able on any architecture. In most cases, a datum is
43826 represented using a little-endian 32-bit integer value, called an
43827 @code{offset_type}. Big endian machines must byte-swap the values
43828 before using them. Exceptions to this rule are noted. The data is
43829 laid out such that alignment is always respected.
43831 A mapped index consists of several areas, laid out in order.
43835 The file header. This is a sequence of values, of @code{offset_type}
43836 unless otherwise noted:
43840 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43841 Version 4 uses a different hashing function from versions 5 and 6.
43842 Version 6 includes symbols for inlined functions, whereas versions 4
43843 and 5 do not. Version 7 adds attributes to the CU indices in the
43844 symbol table. Version 8 specifies that symbols from DWARF type units
43845 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43846 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43848 @value{GDBN} will only read version 4, 5, or 6 indices
43849 by specifying @code{set use-deprecated-index-sections on}.
43850 GDB has a workaround for potentially broken version 7 indices so it is
43851 currently not flagged as deprecated.
43854 The offset, from the start of the file, of the CU list.
43857 The offset, from the start of the file, of the types CU list. Note
43858 that this area can be empty, in which case this offset will be equal
43859 to the next offset.
43862 The offset, from the start of the file, of the address area.
43865 The offset, from the start of the file, of the symbol table.
43868 The offset, from the start of the file, of the constant pool.
43872 The CU list. This is a sequence of pairs of 64-bit little-endian
43873 values, sorted by the CU offset. The first element in each pair is
43874 the offset of a CU in the @code{.debug_info} section. The second
43875 element in each pair is the length of that CU. References to a CU
43876 elsewhere in the map are done using a CU index, which is just the
43877 0-based index into this table. Note that if there are type CUs, then
43878 conceptually CUs and type CUs form a single list for the purposes of
43882 The types CU list. This is a sequence of triplets of 64-bit
43883 little-endian values. In a triplet, the first value is the CU offset,
43884 the second value is the type offset in the CU, and the third value is
43885 the type signature. The types CU list is not sorted.
43888 The address area. The address area consists of a sequence of address
43889 entries. Each address entry has three elements:
43893 The low address. This is a 64-bit little-endian value.
43896 The high address. This is a 64-bit little-endian value. Like
43897 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43900 The CU index. This is an @code{offset_type} value.
43904 The symbol table. This is an open-addressed hash table. The size of
43905 the hash table is always a power of 2.
43907 Each slot in the hash table consists of a pair of @code{offset_type}
43908 values. The first value is the offset of the symbol's name in the
43909 constant pool. The second value is the offset of the CU vector in the
43912 If both values are 0, then this slot in the hash table is empty. This
43913 is ok because while 0 is a valid constant pool index, it cannot be a
43914 valid index for both a string and a CU vector.
43916 The hash value for a table entry is computed by applying an
43917 iterative hash function to the symbol's name. Starting with an
43918 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43919 the string is incorporated into the hash using the formula depending on the
43924 The formula is @code{r = r * 67 + c - 113}.
43926 @item Versions 5 to 7
43927 The formula is @code{r = r * 67 + tolower (c) - 113}.
43930 The terminating @samp{\0} is not incorporated into the hash.
43932 The step size used in the hash table is computed via
43933 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43934 value, and @samp{size} is the size of the hash table. The step size
43935 is used to find the next candidate slot when handling a hash
43938 The names of C@t{++} symbols in the hash table are canonicalized. We
43939 don't currently have a simple description of the canonicalization
43940 algorithm; if you intend to create new index sections, you must read
43944 The constant pool. This is simply a bunch of bytes. It is organized
43945 so that alignment is correct: CU vectors are stored first, followed by
43948 A CU vector in the constant pool is a sequence of @code{offset_type}
43949 values. The first value is the number of CU indices in the vector.
43950 Each subsequent value is the index and symbol attributes of a CU in
43951 the CU list. This element in the hash table is used to indicate which
43952 CUs define the symbol and how the symbol is used.
43953 See below for the format of each CU index+attributes entry.
43955 A string in the constant pool is zero-terminated.
43958 Attributes were added to CU index values in @code{.gdb_index} version 7.
43959 If a symbol has multiple uses within a CU then there is one
43960 CU index+attributes value for each use.
43962 The format of each CU index+attributes entry is as follows
43968 This is the index of the CU in the CU list.
43970 These bits are reserved for future purposes and must be zero.
43972 The kind of the symbol in the CU.
43976 This value is reserved and should not be used.
43977 By reserving zero the full @code{offset_type} value is backwards compatible
43978 with previous versions of the index.
43980 The symbol is a type.
43982 The symbol is a variable or an enum value.
43984 The symbol is a function.
43986 Any other kind of symbol.
43988 These values are reserved.
43992 This bit is zero if the value is global and one if it is static.
43994 The determination of whether a symbol is global or static is complicated.
43995 The authorative reference is the file @file{dwarf2read.c} in
43996 @value{GDBN} sources.
44000 This pseudo-code describes the computation of a symbol's kind and
44001 global/static attributes in the index.
44004 is_external = get_attribute (die, DW_AT_external);
44005 language = get_attribute (cu_die, DW_AT_language);
44008 case DW_TAG_typedef:
44009 case DW_TAG_base_type:
44010 case DW_TAG_subrange_type:
44014 case DW_TAG_enumerator:
44016 is_static = language != CPLUS;
44018 case DW_TAG_subprogram:
44020 is_static = ! (is_external || language == ADA);
44022 case DW_TAG_constant:
44024 is_static = ! is_external;
44026 case DW_TAG_variable:
44028 is_static = ! is_external;
44030 case DW_TAG_namespace:
44034 case DW_TAG_class_type:
44035 case DW_TAG_interface_type:
44036 case DW_TAG_structure_type:
44037 case DW_TAG_union_type:
44038 case DW_TAG_enumeration_type:
44040 is_static = language != CPLUS;
44048 @appendix Manual pages
44052 * gdb man:: The GNU Debugger man page
44053 * gdbserver man:: Remote Server for the GNU Debugger man page
44054 * gcore man:: Generate a core file of a running program
44055 * gdbinit man:: gdbinit scripts
44056 * gdb-add-index man:: Add index files to speed up GDB
44062 @c man title gdb The GNU Debugger
44064 @c man begin SYNOPSIS gdb
44065 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
44066 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
44067 [@option{-b}@w{ }@var{bps}]
44068 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
44069 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
44070 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
44071 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
44072 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
44075 @c man begin DESCRIPTION gdb
44076 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
44077 going on ``inside'' another program while it executes -- or what another
44078 program was doing at the moment it crashed.
44080 @value{GDBN} can do four main kinds of things (plus other things in support of
44081 these) to help you catch bugs in the act:
44085 Start your program, specifying anything that might affect its behavior.
44088 Make your program stop on specified conditions.
44091 Examine what has happened, when your program has stopped.
44094 Change things in your program, so you can experiment with correcting the
44095 effects of one bug and go on to learn about another.
44098 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
44101 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
44102 commands from the terminal until you tell it to exit with the @value{GDBN}
44103 command @code{quit}. You can get online help from @value{GDBN} itself
44104 by using the command @code{help}.
44106 You can run @code{gdb} with no arguments or options; but the most
44107 usual way to start @value{GDBN} is with one argument or two, specifying an
44108 executable program as the argument:
44114 You can also start with both an executable program and a core file specified:
44120 You can, instead, specify a process ID as a second argument, if you want
44121 to debug a running process:
44129 would attach @value{GDBN} to process @code{1234} (unless you also have a file
44130 named @file{1234}; @value{GDBN} does check for a core file first).
44131 With option @option{-p} you can omit the @var{program} filename.
44133 Here are some of the most frequently needed @value{GDBN} commands:
44135 @c pod2man highlights the right hand side of the @item lines.
44137 @item break [@var{file}:]@var{function}
44138 Set a breakpoint at @var{function} (in @var{file}).
44140 @item run [@var{arglist}]
44141 Start your program (with @var{arglist}, if specified).
44144 Backtrace: display the program stack.
44146 @item print @var{expr}
44147 Display the value of an expression.
44150 Continue running your program (after stopping, e.g. at a breakpoint).
44153 Execute next program line (after stopping); step @emph{over} any
44154 function calls in the line.
44156 @item edit [@var{file}:]@var{function}
44157 look at the program line where it is presently stopped.
44159 @item list [@var{file}:]@var{function}
44160 type the text of the program in the vicinity of where it is presently stopped.
44163 Execute next program line (after stopping); step @emph{into} any
44164 function calls in the line.
44166 @item help [@var{name}]
44167 Show information about @value{GDBN} command @var{name}, or general information
44168 about using @value{GDBN}.
44171 Exit from @value{GDBN}.
44175 For full details on @value{GDBN},
44176 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44177 by Richard M. Stallman and Roland H. Pesch. The same text is available online
44178 as the @code{gdb} entry in the @code{info} program.
44182 @c man begin OPTIONS gdb
44183 Any arguments other than options specify an executable
44184 file and core file (or process ID); that is, the first argument
44185 encountered with no
44186 associated option flag is equivalent to a @option{-se} option, and the second,
44187 if any, is equivalent to a @option{-c} option if it's the name of a file.
44189 both long and short forms; both are shown here. The long forms are also
44190 recognized if you truncate them, so long as enough of the option is
44191 present to be unambiguous. (If you prefer, you can flag option
44192 arguments with @option{+} rather than @option{-}, though we illustrate the
44193 more usual convention.)
44195 All the options and command line arguments you give are processed
44196 in sequential order. The order makes a difference when the @option{-x}
44202 List all options, with brief explanations.
44204 @item -symbols=@var{file}
44205 @itemx -s @var{file}
44206 Read symbol table from file @var{file}.
44209 Enable writing into executable and core files.
44211 @item -exec=@var{file}
44212 @itemx -e @var{file}
44213 Use file @var{file} as the executable file to execute when
44214 appropriate, and for examining pure data in conjunction with a core
44217 @item -se=@var{file}
44218 Read symbol table from file @var{file} and use it as the executable
44221 @item -core=@var{file}
44222 @itemx -c @var{file}
44223 Use file @var{file} as a core dump to examine.
44225 @item -command=@var{file}
44226 @itemx -x @var{file}
44227 Execute @value{GDBN} commands from file @var{file}.
44229 @item -ex @var{command}
44230 Execute given @value{GDBN} @var{command}.
44232 @item -directory=@var{directory}
44233 @itemx -d @var{directory}
44234 Add @var{directory} to the path to search for source files.
44237 Do not execute commands from @file{~/.gdbinit}.
44241 Do not execute commands from any @file{.gdbinit} initialization files.
44245 ``Quiet''. Do not print the introductory and copyright messages. These
44246 messages are also suppressed in batch mode.
44249 Run in batch mode. Exit with status @code{0} after processing all the command
44250 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44251 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44252 commands in the command files.
44254 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44255 download and run a program on another computer; in order to make this
44256 more useful, the message
44259 Program exited normally.
44263 (which is ordinarily issued whenever a program running under @value{GDBN} control
44264 terminates) is not issued when running in batch mode.
44266 @item -cd=@var{directory}
44267 Run @value{GDBN} using @var{directory} as its working directory,
44268 instead of the current directory.
44272 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44273 @value{GDBN} to output the full file name and line number in a standard,
44274 recognizable fashion each time a stack frame is displayed (which
44275 includes each time the program stops). This recognizable format looks
44276 like two @samp{\032} characters, followed by the file name, line number
44277 and character position separated by colons, and a newline. The
44278 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44279 characters as a signal to display the source code for the frame.
44282 Set the line speed (baud rate or bits per second) of any serial
44283 interface used by @value{GDBN} for remote debugging.
44285 @item -tty=@var{device}
44286 Run using @var{device} for your program's standard input and output.
44290 @c man begin SEEALSO gdb
44292 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44293 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44294 documentation are properly installed at your site, the command
44301 should give you access to the complete manual.
44303 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44304 Richard M. Stallman and Roland H. Pesch, July 1991.
44308 @node gdbserver man
44309 @heading gdbserver man
44311 @c man title gdbserver Remote Server for the GNU Debugger
44313 @c man begin SYNOPSIS gdbserver
44314 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44316 gdbserver --attach @var{comm} @var{pid}
44318 gdbserver --multi @var{comm}
44322 @c man begin DESCRIPTION gdbserver
44323 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44324 than the one which is running the program being debugged.
44327 @subheading Usage (server (target) side)
44330 Usage (server (target) side):
44333 First, you need to have a copy of the program you want to debug put onto
44334 the target system. The program can be stripped to save space if needed, as
44335 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44336 the @value{GDBN} running on the host system.
44338 To use the server, you log on to the target system, and run the @command{gdbserver}
44339 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44340 your program, and (c) its arguments. The general syntax is:
44343 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44346 For example, using a serial port, you might say:
44350 @c @file would wrap it as F</dev/com1>.
44351 target> gdbserver /dev/com1 emacs foo.txt
44354 target> gdbserver @file{/dev/com1} emacs foo.txt
44358 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44359 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44360 waits patiently for the host @value{GDBN} to communicate with it.
44362 To use a TCP connection, you could say:
44365 target> gdbserver host:2345 emacs foo.txt
44368 This says pretty much the same thing as the last example, except that we are
44369 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44370 that we are expecting to see a TCP connection from @code{host} to local TCP port
44371 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44372 want for the port number as long as it does not conflict with any existing TCP
44373 ports on the target system. This same port number must be used in the host
44374 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44375 you chose a port number that conflicts with another service, @command{gdbserver} will
44376 print an error message and exit.
44378 @command{gdbserver} can also attach to running programs.
44379 This is accomplished via the @option{--attach} argument. The syntax is:
44382 target> gdbserver --attach @var{comm} @var{pid}
44385 @var{pid} is the process ID of a currently running process. It isn't
44386 necessary to point @command{gdbserver} at a binary for the running process.
44388 To start @code{gdbserver} without supplying an initial command to run
44389 or process ID to attach, use the @option{--multi} command line option.
44390 In such case you should connect using @kbd{target extended-remote} to start
44391 the program you want to debug.
44394 target> gdbserver --multi @var{comm}
44398 @subheading Usage (host side)
44404 You need an unstripped copy of the target program on your host system, since
44405 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44406 would, with the target program as the first argument. (You may need to use the
44407 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44408 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44409 new command you need to know about is @code{target remote}
44410 (or @code{target extended-remote}). Its argument is either
44411 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44412 descriptor. For example:
44416 @c @file would wrap it as F</dev/ttyb>.
44417 (gdb) target remote /dev/ttyb
44420 (gdb) target remote @file{/dev/ttyb}
44425 communicates with the server via serial line @file{/dev/ttyb}, and:
44428 (gdb) target remote the-target:2345
44432 communicates via a TCP connection to port 2345 on host `the-target', where
44433 you previously started up @command{gdbserver} with the same port number. Note that for
44434 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44435 command, otherwise you may get an error that looks something like
44436 `Connection refused'.
44438 @command{gdbserver} can also debug multiple inferiors at once,
44441 the @value{GDBN} manual in node @code{Inferiors and Programs}
44442 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44445 @ref{Inferiors and Programs}.
44447 In such case use the @code{extended-remote} @value{GDBN} command variant:
44450 (gdb) target extended-remote the-target:2345
44453 The @command{gdbserver} option @option{--multi} may or may not be used in such
44457 @c man begin OPTIONS gdbserver
44458 There are three different modes for invoking @command{gdbserver}:
44463 Debug a specific program specified by its program name:
44466 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44469 The @var{comm} parameter specifies how should the server communicate
44470 with @value{GDBN}; it is either a device name (to use a serial line),
44471 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44472 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44473 debug in @var{prog}. Any remaining arguments will be passed to the
44474 program verbatim. When the program exits, @value{GDBN} will close the
44475 connection, and @code{gdbserver} will exit.
44478 Debug a specific program by specifying the process ID of a running
44482 gdbserver --attach @var{comm} @var{pid}
44485 The @var{comm} parameter is as described above. Supply the process ID
44486 of a running program in @var{pid}; @value{GDBN} will do everything
44487 else. Like with the previous mode, when the process @var{pid} exits,
44488 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44491 Multi-process mode -- debug more than one program/process:
44494 gdbserver --multi @var{comm}
44497 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44498 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44499 close the connection when a process being debugged exits, so you can
44500 debug several processes in the same session.
44503 In each of the modes you may specify these options:
44508 List all options, with brief explanations.
44511 This option causes @command{gdbserver} to print its version number and exit.
44514 @command{gdbserver} will attach to a running program. The syntax is:
44517 target> gdbserver --attach @var{comm} @var{pid}
44520 @var{pid} is the process ID of a currently running process. It isn't
44521 necessary to point @command{gdbserver} at a binary for the running process.
44524 To start @code{gdbserver} without supplying an initial command to run
44525 or process ID to attach, use this command line option.
44526 Then you can connect using @kbd{target extended-remote} and start
44527 the program you want to debug. The syntax is:
44530 target> gdbserver --multi @var{comm}
44534 Instruct @code{gdbserver} to display extra status information about the debugging
44536 This option is intended for @code{gdbserver} development and for bug reports to
44539 @item --remote-debug
44540 Instruct @code{gdbserver} to display remote protocol debug output.
44541 This option is intended for @code{gdbserver} development and for bug reports to
44544 @item --debug-format=option1@r{[},option2,...@r{]}
44545 Instruct @code{gdbserver} to include extra information in each line
44546 of debugging output.
44547 @xref{Other Command-Line Arguments for gdbserver}.
44550 Specify a wrapper to launch programs
44551 for debugging. The option should be followed by the name of the
44552 wrapper, then any command-line arguments to pass to the wrapper, then
44553 @kbd{--} indicating the end of the wrapper arguments.
44556 By default, @command{gdbserver} keeps the listening TCP port open, so that
44557 additional connections are possible. However, if you start @code{gdbserver}
44558 with the @option{--once} option, it will stop listening for any further
44559 connection attempts after connecting to the first @value{GDBN} session.
44561 @c --disable-packet is not documented for users.
44563 @c --disable-randomization and --no-disable-randomization are superseded by
44564 @c QDisableRandomization.
44569 @c man begin SEEALSO gdbserver
44571 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44572 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44573 documentation are properly installed at your site, the command
44579 should give you access to the complete manual.
44581 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44582 Richard M. Stallman and Roland H. Pesch, July 1991.
44589 @c man title gcore Generate a core file of a running program
44592 @c man begin SYNOPSIS gcore
44593 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44597 @c man begin DESCRIPTION gcore
44598 Generate core dumps of one or more running programs with process IDs
44599 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44600 is equivalent to one produced by the kernel when the process crashes
44601 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44602 limit). However, unlike after a crash, after @command{gcore} finishes
44603 its job the program remains running without any change.
44606 @c man begin OPTIONS gcore
44609 Dump all memory mappings. The actual effect of this option depends on
44610 the Operating System. On @sc{gnu}/Linux, it will disable
44611 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44612 enable @code{dump-excluded-mappings} (@pxref{set
44613 dump-excluded-mappings}).
44615 @item -o @var{prefix}
44616 The optional argument @var{prefix} specifies the prefix to be used
44617 when composing the file names of the core dumps. The file name is
44618 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44619 process ID of the running program being analyzed by @command{gcore}.
44620 If not specified, @var{prefix} defaults to @var{gcore}.
44624 @c man begin SEEALSO gcore
44626 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44627 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44628 documentation are properly installed at your site, the command
44635 should give you access to the complete manual.
44637 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44638 Richard M. Stallman and Roland H. Pesch, July 1991.
44645 @c man title gdbinit GDB initialization scripts
44648 @c man begin SYNOPSIS gdbinit
44649 @ifset SYSTEM_GDBINIT
44650 @value{SYSTEM_GDBINIT}
44659 @c man begin DESCRIPTION gdbinit
44660 These files contain @value{GDBN} commands to automatically execute during
44661 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44664 the @value{GDBN} manual in node @code{Sequences}
44665 -- shell command @code{info -f gdb -n Sequences}.
44671 Please read more in
44673 the @value{GDBN} manual in node @code{Startup}
44674 -- shell command @code{info -f gdb -n Startup}.
44681 @ifset SYSTEM_GDBINIT
44682 @item @value{SYSTEM_GDBINIT}
44684 @ifclear SYSTEM_GDBINIT
44685 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44687 System-wide initialization file. It is executed unless user specified
44688 @value{GDBN} option @code{-nx} or @code{-n}.
44691 the @value{GDBN} manual in node @code{System-wide configuration}
44692 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44695 @ref{System-wide configuration}.
44699 User initialization file. It is executed unless user specified
44700 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44703 Initialization file for current directory. It may need to be enabled with
44704 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44707 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44708 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44711 @ref{Init File in the Current Directory}.
44716 @c man begin SEEALSO gdbinit
44718 gdb(1), @code{info -f gdb -n Startup}
44720 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44721 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44722 documentation are properly installed at your site, the command
44728 should give you access to the complete manual.
44730 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44731 Richard M. Stallman and Roland H. Pesch, July 1991.
44735 @node gdb-add-index man
44736 @heading gdb-add-index
44737 @pindex gdb-add-index
44738 @anchor{gdb-add-index}
44740 @c man title gdb-add-index Add index files to speed up GDB
44742 @c man begin SYNOPSIS gdb-add-index
44743 gdb-add-index @var{filename}
44746 @c man begin DESCRIPTION gdb-add-index
44747 When @value{GDBN} finds a symbol file, it scans the symbols in the
44748 file in order to construct an internal symbol table. This lets most
44749 @value{GDBN} operations work quickly--at the cost of a delay early on.
44750 For large programs, this delay can be quite lengthy, so @value{GDBN}
44751 provides a way to build an index, which speeds up startup.
44753 To determine whether a file contains such an index, use the command
44754 @kbd{readelf -S filename}: the index is stored in a section named
44755 @code{.gdb_index}. The index file can only be produced on systems
44756 which use ELF binaries and DWARF debug information (i.e., sections
44757 named @code{.debug_*}).
44759 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44760 in the @env{PATH} environment variable. If you want to use different
44761 versions of these programs, you can specify them through the
44762 @env{GDB} and @env{OBJDUMP} environment variables.
44766 the @value{GDBN} manual in node @code{Index Files}
44767 -- shell command @kbd{info -f gdb -n "Index Files"}.
44774 @c man begin SEEALSO gdb-add-index
44776 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44777 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44778 documentation are properly installed at your site, the command
44784 should give you access to the complete manual.
44786 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44787 Richard M. Stallman and Roland H. Pesch, July 1991.
44793 @node GNU Free Documentation License
44794 @appendix GNU Free Documentation License
44797 @node Concept Index
44798 @unnumbered Concept Index
44802 @node Command and Variable Index
44803 @unnumbered Command, Variable, and Function Index
44808 % I think something like @@colophon should be in texinfo. In the
44810 \long\def\colophon{\hbox to0pt{}\vfill
44811 \centerline{The body of this manual is set in}
44812 \centerline{\fontname\tenrm,}
44813 \centerline{with headings in {\bf\fontname\tenbf}}
44814 \centerline{and examples in {\tt\fontname\tentt}.}
44815 \centerline{{\it\fontname\tenit\/},}
44816 \centerline{{\bf\fontname\tenbf}, and}
44817 \centerline{{\sl\fontname\tensl\/}}
44818 \centerline{are used for emphasis.}\vfill}
44820 % Blame: doc@@cygnus.com, 1991.