1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 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{} 1988-2017 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) 1988-2017 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.
550 @chapter A Sample @value{GDBN} Session
552 You can use this manual at your leisure to read all about @value{GDBN}.
553 However, a handful of commands are enough to get started using the
554 debugger. This chapter illustrates those commands.
557 In this sample session, we emphasize user input like this: @b{input},
558 to make it easier to pick out from the surrounding output.
561 @c FIXME: this example may not be appropriate for some configs, where
562 @c FIXME...primary interest is in remote use.
564 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
565 processor) exhibits the following bug: sometimes, when we change its
566 quote strings from the default, the commands used to capture one macro
567 definition within another stop working. In the following short @code{m4}
568 session, we define a macro @code{foo} which expands to @code{0000}; we
569 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
570 same thing. However, when we change the open quote string to
571 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
572 procedure fails to define a new synonym @code{baz}:
581 @b{define(bar,defn(`foo'))}
585 @b{changequote(<QUOTE>,<UNQUOTE>)}
587 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
590 m4: End of input: 0: fatal error: EOF in string
594 Let us use @value{GDBN} to try to see what is going on.
597 $ @b{@value{GDBP} m4}
598 @c FIXME: this falsifies the exact text played out, to permit smallbook
599 @c FIXME... format to come out better.
600 @value{GDBN} is free software and you are welcome to distribute copies
601 of it under certain conditions; type "show copying" to see
603 There is absolutely no warranty for @value{GDBN}; type "show warranty"
606 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
611 @value{GDBN} reads only enough symbol data to know where to find the
612 rest when needed; as a result, the first prompt comes up very quickly.
613 We now tell @value{GDBN} to use a narrower display width than usual, so
614 that examples fit in this manual.
617 (@value{GDBP}) @b{set width 70}
621 We need to see how the @code{m4} built-in @code{changequote} works.
622 Having looked at the source, we know the relevant subroutine is
623 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
624 @code{break} command.
627 (@value{GDBP}) @b{break m4_changequote}
628 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
632 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
633 control; as long as control does not reach the @code{m4_changequote}
634 subroutine, the program runs as usual:
637 (@value{GDBP}) @b{run}
638 Starting program: /work/Editorial/gdb/gnu/m4/m4
646 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
647 suspends execution of @code{m4}, displaying information about the
648 context where it stops.
651 @b{changequote(<QUOTE>,<UNQUOTE>)}
653 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
655 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
659 Now we use the command @code{n} (@code{next}) to advance execution to
660 the next line of the current function.
664 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
669 @code{set_quotes} looks like a promising subroutine. We can go into it
670 by using the command @code{s} (@code{step}) instead of @code{next}.
671 @code{step} goes to the next line to be executed in @emph{any}
672 subroutine, so it steps into @code{set_quotes}.
676 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 530 if (lquote != def_lquote)
682 The display that shows the subroutine where @code{m4} is now
683 suspended (and its arguments) is called a stack frame display. It
684 shows a summary of the stack. We can use the @code{backtrace}
685 command (which can also be spelled @code{bt}), to see where we are
686 in the stack as a whole: the @code{backtrace} command displays a
687 stack frame for each active subroutine.
690 (@value{GDBP}) @b{bt}
691 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
695 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
696 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
698 #4 0x79dc in expand_input () at macro.c:40
699 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
703 We step through a few more lines to see what happens. The first two
704 times, we can use @samp{s}; the next two times we use @code{n} to avoid
705 falling into the @code{xstrdup} subroutine.
709 0x3b5c 532 if (rquote != def_rquote)
711 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
712 def_lquote : xstrdup(lq);
714 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
717 538 len_lquote = strlen(rquote);
721 The last line displayed looks a little odd; we can examine the variables
722 @code{lquote} and @code{rquote} to see if they are in fact the new left
723 and right quotes we specified. We use the command @code{p}
724 (@code{print}) to see their values.
727 (@value{GDBP}) @b{p lquote}
728 $1 = 0x35d40 "<QUOTE>"
729 (@value{GDBP}) @b{p rquote}
730 $2 = 0x35d50 "<UNQUOTE>"
734 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
735 To look at some context, we can display ten lines of source
736 surrounding the current line with the @code{l} (@code{list}) command.
742 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
744 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
747 538 len_lquote = strlen(rquote);
748 539 len_rquote = strlen(lquote);
755 Let us step past the two lines that set @code{len_lquote} and
756 @code{len_rquote}, and then examine the values of those variables.
760 539 len_rquote = strlen(lquote);
763 (@value{GDBP}) @b{p len_lquote}
765 (@value{GDBP}) @b{p len_rquote}
770 That certainly looks wrong, assuming @code{len_lquote} and
771 @code{len_rquote} are meant to be the lengths of @code{lquote} and
772 @code{rquote} respectively. We can set them to better values using
773 the @code{p} command, since it can print the value of
774 any expression---and that expression can include subroutine calls and
778 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
780 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
785 Is that enough to fix the problem of using the new quotes with the
786 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
787 executing with the @code{c} (@code{continue}) command, and then try the
788 example that caused trouble initially:
794 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
801 Success! The new quotes now work just as well as the default ones. The
802 problem seems to have been just the two typos defining the wrong
803 lengths. We allow @code{m4} exit by giving it an EOF as input:
807 Program exited normally.
811 The message @samp{Program exited normally.} is from @value{GDBN}; it
812 indicates @code{m4} has finished executing. We can end our @value{GDBN}
813 session with the @value{GDBN} @code{quit} command.
816 (@value{GDBP}) @b{quit}
820 @chapter Getting In and Out of @value{GDBN}
822 This chapter discusses how to start @value{GDBN}, and how to get out of it.
826 type @samp{@value{GDBP}} to start @value{GDBN}.
828 type @kbd{quit} or @kbd{Ctrl-d} to exit.
832 * Invoking GDB:: How to start @value{GDBN}
833 * Quitting GDB:: How to quit @value{GDBN}
834 * Shell Commands:: How to use shell commands inside @value{GDBN}
835 * Logging Output:: How to log @value{GDBN}'s output to a file
839 @section Invoking @value{GDBN}
841 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
842 @value{GDBN} reads commands from the terminal until you tell it to exit.
844 You can also run @code{@value{GDBP}} with a variety of arguments and options,
845 to specify more of your debugging environment at the outset.
847 The command-line options described here are designed
848 to cover a variety of situations; in some environments, some of these
849 options may effectively be unavailable.
851 The most usual way to start @value{GDBN} is with one argument,
852 specifying an executable program:
855 @value{GDBP} @var{program}
859 You can also start with both an executable program and a core file
863 @value{GDBP} @var{program} @var{core}
866 You can, instead, specify a process ID as a second argument, if you want
867 to debug a running process:
870 @value{GDBP} @var{program} 1234
874 would attach @value{GDBN} to process @code{1234} (unless you also have a file
875 named @file{1234}; @value{GDBN} does check for a core file first).
877 Taking advantage of the second command-line argument requires a fairly
878 complete operating system; when you use @value{GDBN} as a remote
879 debugger attached to a bare board, there may not be any notion of
880 ``process'', and there is often no way to get a core dump. @value{GDBN}
881 will warn you if it is unable to attach or to read core dumps.
883 You can optionally have @code{@value{GDBP}} pass any arguments after the
884 executable file to the inferior using @code{--args}. This option stops
887 @value{GDBP} --args gcc -O2 -c foo.c
889 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
890 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
892 You can run @code{@value{GDBP}} without printing the front material, which describes
893 @value{GDBN}'s non-warranty, by specifying @code{--silent}
894 (or @code{-q}/@code{--quiet}):
897 @value{GDBP} --silent
901 You can further control how @value{GDBN} starts up by using command-line
902 options. @value{GDBN} itself can remind you of the options available.
912 to display all available options and briefly describe their use
913 (@samp{@value{GDBP} -h} is a shorter equivalent).
915 All options and command line arguments you give are processed
916 in sequential order. The order makes a difference when the
917 @samp{-x} option is used.
921 * File Options:: Choosing files
922 * Mode Options:: Choosing modes
923 * Startup:: What @value{GDBN} does during startup
927 @subsection Choosing Files
929 When @value{GDBN} starts, it reads any arguments other than options as
930 specifying an executable file and core file (or process ID). This is
931 the same as if the arguments were specified by the @samp{-se} and
932 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
933 first argument that does not have an associated option flag as
934 equivalent to the @samp{-se} option followed by that argument; and the
935 second argument that does not have an associated option flag, if any, as
936 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
937 If the second argument begins with a decimal digit, @value{GDBN} will
938 first attempt to attach to it as a process, and if that fails, attempt
939 to open it as a corefile. If you have a corefile whose name begins with
940 a digit, you can prevent @value{GDBN} from treating it as a pid by
941 prefixing it with @file{./}, e.g.@: @file{./12345}.
943 If @value{GDBN} has not been configured to included core file support,
944 such as for most embedded targets, then it will complain about a second
945 argument and ignore it.
947 Many options have both long and short forms; both are shown in the
948 following list. @value{GDBN} also recognizes the long forms if you truncate
949 them, so long as enough of the option is present to be unambiguous.
950 (If you prefer, you can flag option arguments with @samp{--} rather
951 than @samp{-}, though we illustrate the more usual convention.)
953 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
954 @c way, both those who look for -foo and --foo in the index, will find
958 @item -symbols @var{file}
960 @cindex @code{--symbols}
962 Read symbol table from file @var{file}.
964 @item -exec @var{file}
966 @cindex @code{--exec}
968 Use file @var{file} as the executable file to execute when appropriate,
969 and for examining pure data in conjunction with a core dump.
973 Read symbol table from file @var{file} and use it as the executable
976 @item -core @var{file}
978 @cindex @code{--core}
980 Use file @var{file} as a core dump to examine.
982 @item -pid @var{number}
983 @itemx -p @var{number}
986 Connect to process ID @var{number}, as with the @code{attach} command.
988 @item -command @var{file}
990 @cindex @code{--command}
992 Execute commands from file @var{file}. The contents of this file is
993 evaluated exactly as the @code{source} command would.
994 @xref{Command Files,, Command files}.
996 @item -eval-command @var{command}
997 @itemx -ex @var{command}
998 @cindex @code{--eval-command}
1000 Execute a single @value{GDBN} command.
1002 This option may be used multiple times to call multiple commands. It may
1003 also be interleaved with @samp{-command} as required.
1006 @value{GDBP} -ex 'target sim' -ex 'load' \
1007 -x setbreakpoints -ex 'run' a.out
1010 @item -init-command @var{file}
1011 @itemx -ix @var{file}
1012 @cindex @code{--init-command}
1014 Execute commands from file @var{file} before loading the inferior (but
1015 after loading gdbinit files).
1018 @item -init-eval-command @var{command}
1019 @itemx -iex @var{command}
1020 @cindex @code{--init-eval-command}
1022 Execute a single @value{GDBN} command before loading the inferior (but
1023 after loading gdbinit files).
1026 @item -directory @var{directory}
1027 @itemx -d @var{directory}
1028 @cindex @code{--directory}
1030 Add @var{directory} to the path to search for source and script files.
1034 @cindex @code{--readnow}
1036 Read each symbol file's entire symbol table immediately, rather than
1037 the default, which is to read it incrementally as it is needed.
1038 This makes startup slower, but makes future operations faster.
1043 @subsection Choosing Modes
1045 You can run @value{GDBN} in various alternative modes---for example, in
1046 batch mode or quiet mode.
1054 Do not execute commands found in any initialization file.
1055 There are three init files, loaded in the following order:
1058 @item @file{system.gdbinit}
1059 This is the system-wide init file.
1060 Its location is specified with the @code{--with-system-gdbinit}
1061 configure option (@pxref{System-wide configuration}).
1062 It is loaded first when @value{GDBN} starts, before command line options
1063 have been processed.
1064 @item @file{~/.gdbinit}
1065 This is the init file in your home directory.
1066 It is loaded next, after @file{system.gdbinit}, and before
1067 command options have been processed.
1068 @item @file{./.gdbinit}
1069 This is the init file in the current directory.
1070 It is loaded last, after command line options other than @code{-x} and
1071 @code{-ex} have been processed. Command line options @code{-x} and
1072 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1075 For further documentation on startup processing, @xref{Startup}.
1076 For documentation on how to write command files,
1077 @xref{Command Files,,Command Files}.
1082 Do not execute commands found in @file{~/.gdbinit}, the init file
1083 in your home directory.
1089 @cindex @code{--quiet}
1090 @cindex @code{--silent}
1092 ``Quiet''. Do not print the introductory and copyright messages. These
1093 messages are also suppressed in batch mode.
1096 @cindex @code{--batch}
1097 Run in batch mode. Exit with status @code{0} after processing all the
1098 command files specified with @samp{-x} (and all commands from
1099 initialization files, if not inhibited with @samp{-n}). Exit with
1100 nonzero status if an error occurs in executing the @value{GDBN} commands
1101 in the command files. Batch mode also disables pagination, sets unlimited
1102 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1103 off} were in effect (@pxref{Messages/Warnings}).
1105 Batch mode may be useful for running @value{GDBN} as a filter, for
1106 example to download and run a program on another computer; in order to
1107 make this more useful, the message
1110 Program exited normally.
1114 (which is ordinarily issued whenever a program running under
1115 @value{GDBN} control terminates) is not issued when running in batch
1119 @cindex @code{--batch-silent}
1120 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1121 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1122 unaffected). This is much quieter than @samp{-silent} and would be useless
1123 for an interactive session.
1125 This is particularly useful when using targets that give @samp{Loading section}
1126 messages, for example.
1128 Note that targets that give their output via @value{GDBN}, as opposed to
1129 writing directly to @code{stdout}, will also be made silent.
1131 @item -return-child-result
1132 @cindex @code{--return-child-result}
1133 The return code from @value{GDBN} will be the return code from the child
1134 process (the process being debugged), with the following exceptions:
1138 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1139 internal error. In this case the exit code is the same as it would have been
1140 without @samp{-return-child-result}.
1142 The user quits with an explicit value. E.g., @samp{quit 1}.
1144 The child process never runs, or is not allowed to terminate, in which case
1145 the exit code will be -1.
1148 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1149 when @value{GDBN} is being used as a remote program loader or simulator
1154 @cindex @code{--nowindows}
1156 ``No windows''. If @value{GDBN} comes with a graphical user interface
1157 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1158 interface. If no GUI is available, this option has no effect.
1162 @cindex @code{--windows}
1164 If @value{GDBN} includes a GUI, then this option requires it to be
1167 @item -cd @var{directory}
1169 Run @value{GDBN} using @var{directory} as its working directory,
1170 instead of the current directory.
1172 @item -data-directory @var{directory}
1173 @itemx -D @var{directory}
1174 @cindex @code{--data-directory}
1176 Run @value{GDBN} using @var{directory} as its data directory.
1177 The data directory is where @value{GDBN} searches for its
1178 auxiliary files. @xref{Data Files}.
1182 @cindex @code{--fullname}
1184 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1185 subprocess. It tells @value{GDBN} to output the full file name and line
1186 number in a standard, recognizable fashion each time a stack frame is
1187 displayed (which includes each time your program stops). This
1188 recognizable format looks like two @samp{\032} characters, followed by
1189 the file name, line number and character position separated by colons,
1190 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1191 @samp{\032} characters as a signal to display the source code for the
1194 @item -annotate @var{level}
1195 @cindex @code{--annotate}
1196 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1197 effect is identical to using @samp{set annotate @var{level}}
1198 (@pxref{Annotations}). The annotation @var{level} controls how much
1199 information @value{GDBN} prints together with its prompt, values of
1200 expressions, source lines, and other types of output. Level 0 is the
1201 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1202 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1203 that control @value{GDBN}, and level 2 has been deprecated.
1205 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1209 @cindex @code{--args}
1210 Change interpretation of command line so that arguments following the
1211 executable file are passed as command line arguments to the inferior.
1212 This option stops option processing.
1214 @item -baud @var{bps}
1216 @cindex @code{--baud}
1218 Set the line speed (baud rate or bits per second) of any serial
1219 interface used by @value{GDBN} for remote debugging.
1221 @item -l @var{timeout}
1223 Set the timeout (in seconds) of any communication used by @value{GDBN}
1224 for remote debugging.
1226 @item -tty @var{device}
1227 @itemx -t @var{device}
1228 @cindex @code{--tty}
1230 Run using @var{device} for your program's standard input and output.
1231 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1233 @c resolve the situation of these eventually
1235 @cindex @code{--tui}
1236 Activate the @dfn{Text User Interface} when starting. The Text User
1237 Interface manages several text windows on the terminal, showing
1238 source, assembly, registers and @value{GDBN} command outputs
1239 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1240 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1241 Using @value{GDBN} under @sc{gnu} Emacs}).
1243 @item -interpreter @var{interp}
1244 @cindex @code{--interpreter}
1245 Use the interpreter @var{interp} for interface with the controlling
1246 program or device. This option is meant to be set by programs which
1247 communicate with @value{GDBN} using it as a back end.
1248 @xref{Interpreters, , Command Interpreters}.
1250 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1251 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1252 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1253 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1254 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1255 @sc{gdb/mi} interfaces are no longer supported.
1258 @cindex @code{--write}
1259 Open the executable and core files for both reading and writing. This
1260 is equivalent to the @samp{set write on} command inside @value{GDBN}
1264 @cindex @code{--statistics}
1265 This option causes @value{GDBN} to print statistics about time and
1266 memory usage after it completes each command and returns to the prompt.
1269 @cindex @code{--version}
1270 This option causes @value{GDBN} to print its version number and
1271 no-warranty blurb, and exit.
1273 @item -configuration
1274 @cindex @code{--configuration}
1275 This option causes @value{GDBN} to print details about its build-time
1276 configuration parameters, and then exit. These details can be
1277 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1282 @subsection What @value{GDBN} Does During Startup
1283 @cindex @value{GDBN} startup
1285 Here's the description of what @value{GDBN} does during session startup:
1289 Sets up the command interpreter as specified by the command line
1290 (@pxref{Mode Options, interpreter}).
1294 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1295 used when building @value{GDBN}; @pxref{System-wide configuration,
1296 ,System-wide configuration and settings}) and executes all the commands in
1299 @anchor{Home Directory Init File}
1301 Reads the init file (if any) in your home directory@footnote{On
1302 DOS/Windows systems, the home directory is the one pointed to by the
1303 @code{HOME} environment variable.} and executes all the commands in
1306 @anchor{Option -init-eval-command}
1308 Executes commands and command files specified by the @samp{-iex} and
1309 @samp{-ix} options in their specified order. Usually you should use the
1310 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1311 settings before @value{GDBN} init files get executed and before inferior
1315 Processes command line options and operands.
1317 @anchor{Init File in the Current Directory during Startup}
1319 Reads and executes the commands from init file (if any) in the current
1320 working directory as long as @samp{set auto-load local-gdbinit} is set to
1321 @samp{on} (@pxref{Init File in the Current Directory}).
1322 This is only done if the current directory is
1323 different from your home directory. Thus, you can have more than one
1324 init file, one generic in your home directory, and another, specific
1325 to the program you are debugging, in the directory where you invoke
1329 If the command line specified a program to debug, or a process to
1330 attach to, or a core file, @value{GDBN} loads any auto-loaded
1331 scripts provided for the program or for its loaded shared libraries.
1332 @xref{Auto-loading}.
1334 If you wish to disable the auto-loading during startup,
1335 you must do something like the following:
1338 $ gdb -iex "set auto-load python-scripts off" myprogram
1341 Option @samp{-ex} does not work because the auto-loading is then turned
1345 Executes commands and command files specified by the @samp{-ex} and
1346 @samp{-x} options in their specified order. @xref{Command Files}, for
1347 more details about @value{GDBN} command files.
1350 Reads the command history recorded in the @dfn{history file}.
1351 @xref{Command History}, for more details about the command history and the
1352 files where @value{GDBN} records it.
1355 Init files use the same syntax as @dfn{command files} (@pxref{Command
1356 Files}) and are processed by @value{GDBN} in the same way. The init
1357 file in your home directory can set options (such as @samp{set
1358 complaints}) that affect subsequent processing of command line options
1359 and operands. Init files are not executed if you use the @samp{-nx}
1360 option (@pxref{Mode Options, ,Choosing Modes}).
1362 To display the list of init files loaded by gdb at startup, you
1363 can use @kbd{gdb --help}.
1365 @cindex init file name
1366 @cindex @file{.gdbinit}
1367 @cindex @file{gdb.ini}
1368 The @value{GDBN} init files are normally called @file{.gdbinit}.
1369 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1370 the limitations of file names imposed by DOS filesystems. The Windows
1371 port of @value{GDBN} uses the standard name, but if it finds a
1372 @file{gdb.ini} file in your home directory, it warns you about that
1373 and suggests to rename the file to the standard name.
1377 @section Quitting @value{GDBN}
1378 @cindex exiting @value{GDBN}
1379 @cindex leaving @value{GDBN}
1382 @kindex quit @r{[}@var{expression}@r{]}
1383 @kindex q @r{(@code{quit})}
1384 @item quit @r{[}@var{expression}@r{]}
1386 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1387 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1388 do not supply @var{expression}, @value{GDBN} will terminate normally;
1389 otherwise it will terminate using the result of @var{expression} as the
1394 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1395 terminates the action of any @value{GDBN} command that is in progress and
1396 returns to @value{GDBN} command level. It is safe to type the interrupt
1397 character at any time because @value{GDBN} does not allow it to take effect
1398 until a time when it is safe.
1400 If you have been using @value{GDBN} to control an attached process or
1401 device, you can release it with the @code{detach} command
1402 (@pxref{Attach, ,Debugging an Already-running Process}).
1404 @node Shell Commands
1405 @section Shell Commands
1407 If you need to execute occasional shell commands during your
1408 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1409 just use the @code{shell} command.
1414 @cindex shell escape
1415 @item shell @var{command-string}
1416 @itemx !@var{command-string}
1417 Invoke a standard shell to execute @var{command-string}.
1418 Note that no space is needed between @code{!} and @var{command-string}.
1419 If it exists, the environment variable @code{SHELL} determines which
1420 shell to run. Otherwise @value{GDBN} uses the default shell
1421 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1424 The utility @code{make} is often needed in development environments.
1425 You do not have to use the @code{shell} command for this purpose in
1430 @cindex calling make
1431 @item make @var{make-args}
1432 Execute the @code{make} program with the specified
1433 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1436 @node Logging Output
1437 @section Logging Output
1438 @cindex logging @value{GDBN} output
1439 @cindex save @value{GDBN} output to a file
1441 You may want to save the output of @value{GDBN} commands to a file.
1442 There are several commands to control @value{GDBN}'s logging.
1446 @item set logging on
1448 @item set logging off
1450 @cindex logging file name
1451 @item set logging file @var{file}
1452 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1453 @item set logging overwrite [on|off]
1454 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1455 you want @code{set logging on} to overwrite the logfile instead.
1456 @item set logging redirect [on|off]
1457 By default, @value{GDBN} output will go to both the terminal and the logfile.
1458 Set @code{redirect} if you want output to go only to the log file.
1459 @kindex show logging
1461 Show the current values of the logging settings.
1465 @chapter @value{GDBN} Commands
1467 You can abbreviate a @value{GDBN} command to the first few letters of the command
1468 name, if that abbreviation is unambiguous; and you can repeat certain
1469 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1470 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1471 show you the alternatives available, if there is more than one possibility).
1474 * Command Syntax:: How to give commands to @value{GDBN}
1475 * Completion:: Command completion
1476 * Help:: How to ask @value{GDBN} for help
1479 @node Command Syntax
1480 @section Command Syntax
1482 A @value{GDBN} command is a single line of input. There is no limit on
1483 how long it can be. It starts with a command name, which is followed by
1484 arguments whose meaning depends on the command name. For example, the
1485 command @code{step} accepts an argument which is the number of times to
1486 step, as in @samp{step 5}. You can also use the @code{step} command
1487 with no arguments. Some commands do not allow any arguments.
1489 @cindex abbreviation
1490 @value{GDBN} command names may always be truncated if that abbreviation is
1491 unambiguous. Other possible command abbreviations are listed in the
1492 documentation for individual commands. In some cases, even ambiguous
1493 abbreviations are allowed; for example, @code{s} is specially defined as
1494 equivalent to @code{step} even though there are other commands whose
1495 names start with @code{s}. You can test abbreviations by using them as
1496 arguments to the @code{help} command.
1498 @cindex repeating commands
1499 @kindex RET @r{(repeat last command)}
1500 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1501 repeat the previous command. Certain commands (for example, @code{run})
1502 will not repeat this way; these are commands whose unintentional
1503 repetition might cause trouble and which you are unlikely to want to
1504 repeat. User-defined commands can disable this feature; see
1505 @ref{Define, dont-repeat}.
1507 The @code{list} and @code{x} commands, when you repeat them with
1508 @key{RET}, construct new arguments rather than repeating
1509 exactly as typed. This permits easy scanning of source or memory.
1511 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1512 output, in a way similar to the common utility @code{more}
1513 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1514 @key{RET} too many in this situation, @value{GDBN} disables command
1515 repetition after any command that generates this sort of display.
1517 @kindex # @r{(a comment)}
1519 Any text from a @kbd{#} to the end of the line is a comment; it does
1520 nothing. This is useful mainly in command files (@pxref{Command
1521 Files,,Command Files}).
1523 @cindex repeating command sequences
1524 @kindex Ctrl-o @r{(operate-and-get-next)}
1525 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1526 commands. This command accepts the current line, like @key{RET}, and
1527 then fetches the next line relative to the current line from the history
1531 @section Command Completion
1534 @cindex word completion
1535 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1536 only one possibility; it can also show you what the valid possibilities
1537 are for the next word in a command, at any time. This works for @value{GDBN}
1538 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1540 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1541 of a word. If there is only one possibility, @value{GDBN} fills in the
1542 word, and waits for you to finish the command (or press @key{RET} to
1543 enter it). For example, if you type
1545 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1546 @c complete accuracy in these examples; space introduced for clarity.
1547 @c If texinfo enhancements make it unnecessary, it would be nice to
1548 @c replace " @key" by "@key" in the following...
1550 (@value{GDBP}) info bre @key{TAB}
1554 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1555 the only @code{info} subcommand beginning with @samp{bre}:
1558 (@value{GDBP}) info breakpoints
1562 You can either press @key{RET} at this point, to run the @code{info
1563 breakpoints} command, or backspace and enter something else, if
1564 @samp{breakpoints} does not look like the command you expected. (If you
1565 were sure you wanted @code{info breakpoints} in the first place, you
1566 might as well just type @key{RET} immediately after @samp{info bre},
1567 to exploit command abbreviations rather than command completion).
1569 If there is more than one possibility for the next word when you press
1570 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1571 characters and try again, or just press @key{TAB} a second time;
1572 @value{GDBN} displays all the possible completions for that word. For
1573 example, you might want to set a breakpoint on a subroutine whose name
1574 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1575 just sounds the bell. Typing @key{TAB} again displays all the
1576 function names in your program that begin with those characters, for
1580 (@value{GDBP}) b make_ @key{TAB}
1581 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1582 make_a_section_from_file make_environ
1583 make_abs_section make_function_type
1584 make_blockvector make_pointer_type
1585 make_cleanup make_reference_type
1586 make_command make_symbol_completion_list
1587 (@value{GDBP}) b make_
1591 After displaying the available possibilities, @value{GDBN} copies your
1592 partial input (@samp{b make_} in the example) so you can finish the
1595 If you just want to see the list of alternatives in the first place, you
1596 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1597 means @kbd{@key{META} ?}. You can type this either by holding down a
1598 key designated as the @key{META} shift on your keyboard (if there is
1599 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1601 If the number of possible completions is large, @value{GDBN} will
1602 print as much of the list as it has collected, as well as a message
1603 indicating that the list may be truncated.
1606 (@value{GDBP}) b m@key{TAB}@key{TAB}
1608 <... the rest of the possible completions ...>
1609 *** List may be truncated, max-completions reached. ***
1614 This behavior can be controlled with the following commands:
1617 @kindex set max-completions
1618 @item set max-completions @var{limit}
1619 @itemx set max-completions unlimited
1620 Set the maximum number of completion candidates. @value{GDBN} will
1621 stop looking for more completions once it collects this many candidates.
1622 This is useful when completing on things like function names as collecting
1623 all the possible candidates can be time consuming.
1624 The default value is 200. A value of zero disables tab-completion.
1625 Note that setting either no limit or a very large limit can make
1627 @kindex show max-completions
1628 @item show max-completions
1629 Show the maximum number of candidates that @value{GDBN} will collect and show
1633 @cindex quotes in commands
1634 @cindex completion of quoted strings
1635 Sometimes the string you need, while logically a ``word'', may contain
1636 parentheses or other characters that @value{GDBN} normally excludes from
1637 its notion of a word. To permit word completion to work in this
1638 situation, you may enclose words in @code{'} (single quote marks) in
1639 @value{GDBN} commands.
1641 The most likely situation where you might need this is in typing the
1642 name of a C@t{++} function. This is because C@t{++} allows function
1643 overloading (multiple definitions of the same function, distinguished
1644 by argument type). For example, when you want to set a breakpoint you
1645 may need to distinguish whether you mean the version of @code{name}
1646 that takes an @code{int} parameter, @code{name(int)}, or the version
1647 that takes a @code{float} parameter, @code{name(float)}. To use the
1648 word-completion facilities in this situation, type a single quote
1649 @code{'} at the beginning of the function name. This alerts
1650 @value{GDBN} that it may need to consider more information than usual
1651 when you press @key{TAB} or @kbd{M-?} to request word completion:
1654 (@value{GDBP}) b 'bubble( @kbd{M-?}
1655 bubble(double,double) bubble(int,int)
1656 (@value{GDBP}) b 'bubble(
1659 In some cases, @value{GDBN} can tell that completing a name requires using
1660 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1661 completing as much as it can) if you do not type the quote in the first
1665 (@value{GDBP}) b bub @key{TAB}
1666 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1667 (@value{GDBP}) b 'bubble(
1671 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1672 you have not yet started typing the argument list when you ask for
1673 completion on an overloaded symbol.
1675 For more information about overloaded functions, see @ref{C Plus Plus
1676 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1677 overload-resolution off} to disable overload resolution;
1678 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1680 @cindex completion of structure field names
1681 @cindex structure field name completion
1682 @cindex completion of union field names
1683 @cindex union field name completion
1684 When completing in an expression which looks up a field in a
1685 structure, @value{GDBN} also tries@footnote{The completer can be
1686 confused by certain kinds of invalid expressions. Also, it only
1687 examines the static type of the expression, not the dynamic type.} to
1688 limit completions to the field names available in the type of the
1692 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1693 magic to_fputs to_rewind
1694 to_data to_isatty to_write
1695 to_delete to_put to_write_async_safe
1700 This is because the @code{gdb_stdout} is a variable of the type
1701 @code{struct ui_file} that is defined in @value{GDBN} sources as
1708 ui_file_flush_ftype *to_flush;
1709 ui_file_write_ftype *to_write;
1710 ui_file_write_async_safe_ftype *to_write_async_safe;
1711 ui_file_fputs_ftype *to_fputs;
1712 ui_file_read_ftype *to_read;
1713 ui_file_delete_ftype *to_delete;
1714 ui_file_isatty_ftype *to_isatty;
1715 ui_file_rewind_ftype *to_rewind;
1716 ui_file_put_ftype *to_put;
1723 @section Getting Help
1724 @cindex online documentation
1727 You can always ask @value{GDBN} itself for information on its commands,
1728 using the command @code{help}.
1731 @kindex h @r{(@code{help})}
1734 You can use @code{help} (abbreviated @code{h}) with no arguments to
1735 display a short list of named classes of commands:
1739 List of classes of commands:
1741 aliases -- Aliases of other commands
1742 breakpoints -- Making program stop at certain points
1743 data -- Examining data
1744 files -- Specifying and examining files
1745 internals -- Maintenance commands
1746 obscure -- Obscure features
1747 running -- Running the program
1748 stack -- Examining the stack
1749 status -- Status inquiries
1750 support -- Support facilities
1751 tracepoints -- Tracing of program execution without
1752 stopping the program
1753 user-defined -- User-defined commands
1755 Type "help" followed by a class name for a list of
1756 commands in that class.
1757 Type "help" followed by command name for full
1759 Command name abbreviations are allowed if unambiguous.
1762 @c the above line break eliminates huge line overfull...
1764 @item help @var{class}
1765 Using one of the general help classes as an argument, you can get a
1766 list of the individual commands in that class. For example, here is the
1767 help display for the class @code{status}:
1770 (@value{GDBP}) help status
1775 @c Line break in "show" line falsifies real output, but needed
1776 @c to fit in smallbook page size.
1777 info -- Generic command for showing things
1778 about the program being debugged
1779 show -- Generic command for showing things
1782 Type "help" followed by command name for full
1784 Command name abbreviations are allowed if unambiguous.
1788 @item help @var{command}
1789 With a command name as @code{help} argument, @value{GDBN} displays a
1790 short paragraph on how to use that command.
1793 @item apropos @var{args}
1794 The @code{apropos} command searches through all of the @value{GDBN}
1795 commands, and their documentation, for the regular expression specified in
1796 @var{args}. It prints out all matches found. For example:
1807 alias -- Define a new command that is an alias of an existing command
1808 aliases -- Aliases of other commands
1809 d -- Delete some breakpoints or auto-display expressions
1810 del -- Delete some breakpoints or auto-display expressions
1811 delete -- Delete some breakpoints or auto-display expressions
1816 @item complete @var{args}
1817 The @code{complete @var{args}} command lists all the possible completions
1818 for the beginning of a command. Use @var{args} to specify the beginning of the
1819 command you want completed. For example:
1825 @noindent results in:
1836 @noindent This is intended for use by @sc{gnu} Emacs.
1839 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1840 and @code{show} to inquire about the state of your program, or the state
1841 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1842 manual introduces each of them in the appropriate context. The listings
1843 under @code{info} and under @code{show} in the Command, Variable, and
1844 Function Index point to all the sub-commands. @xref{Command and Variable
1850 @kindex i @r{(@code{info})}
1852 This command (abbreviated @code{i}) is for describing the state of your
1853 program. For example, you can show the arguments passed to a function
1854 with @code{info args}, list the registers currently in use with @code{info
1855 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1856 You can get a complete list of the @code{info} sub-commands with
1857 @w{@code{help info}}.
1861 You can assign the result of an expression to an environment variable with
1862 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1863 @code{set prompt $}.
1867 In contrast to @code{info}, @code{show} is for describing the state of
1868 @value{GDBN} itself.
1869 You can change most of the things you can @code{show}, by using the
1870 related command @code{set}; for example, you can control what number
1871 system is used for displays with @code{set radix}, or simply inquire
1872 which is currently in use with @code{show radix}.
1875 To display all the settable parameters and their current
1876 values, you can use @code{show} with no arguments; you may also use
1877 @code{info set}. Both commands produce the same display.
1878 @c FIXME: "info set" violates the rule that "info" is for state of
1879 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1880 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1884 Here are several miscellaneous @code{show} subcommands, all of which are
1885 exceptional in lacking corresponding @code{set} commands:
1888 @kindex show version
1889 @cindex @value{GDBN} version number
1891 Show what version of @value{GDBN} is running. You should include this
1892 information in @value{GDBN} bug-reports. If multiple versions of
1893 @value{GDBN} are in use at your site, you may need to determine which
1894 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1895 commands are introduced, and old ones may wither away. Also, many
1896 system vendors ship variant versions of @value{GDBN}, and there are
1897 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1898 The version number is the same as the one announced when you start
1901 @kindex show copying
1902 @kindex info copying
1903 @cindex display @value{GDBN} copyright
1906 Display information about permission for copying @value{GDBN}.
1908 @kindex show warranty
1909 @kindex info warranty
1911 @itemx info warranty
1912 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1913 if your version of @value{GDBN} comes with one.
1915 @kindex show configuration
1916 @item show configuration
1917 Display detailed information about the way @value{GDBN} was configured
1918 when it was built. This displays the optional arguments passed to the
1919 @file{configure} script and also configuration parameters detected
1920 automatically by @command{configure}. When reporting a @value{GDBN}
1921 bug (@pxref{GDB Bugs}), it is important to include this information in
1927 @chapter Running Programs Under @value{GDBN}
1929 When you run a program under @value{GDBN}, you must first generate
1930 debugging information when you compile it.
1932 You may start @value{GDBN} with its arguments, if any, in an environment
1933 of your choice. If you are doing native debugging, you may redirect
1934 your program's input and output, debug an already running process, or
1935 kill a child process.
1938 * Compilation:: Compiling for debugging
1939 * Starting:: Starting your program
1940 * Arguments:: Your program's arguments
1941 * Environment:: Your program's environment
1943 * Working Directory:: Your program's working directory
1944 * Input/Output:: Your program's input and output
1945 * Attach:: Debugging an already-running process
1946 * Kill Process:: Killing the child process
1948 * Inferiors and Programs:: Debugging multiple inferiors and programs
1949 * Threads:: Debugging programs with multiple threads
1950 * Forks:: Debugging forks
1951 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1955 @section Compiling for Debugging
1957 In order to debug a program effectively, you need to generate
1958 debugging information when you compile it. This debugging information
1959 is stored in the object file; it describes the data type of each
1960 variable or function and the correspondence between source line numbers
1961 and addresses in the executable code.
1963 To request debugging information, specify the @samp{-g} option when you run
1966 Programs that are to be shipped to your customers are compiled with
1967 optimizations, using the @samp{-O} compiler option. However, some
1968 compilers are unable to handle the @samp{-g} and @samp{-O} options
1969 together. Using those compilers, you cannot generate optimized
1970 executables containing debugging information.
1972 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1973 without @samp{-O}, making it possible to debug optimized code. We
1974 recommend that you @emph{always} use @samp{-g} whenever you compile a
1975 program. You may think your program is correct, but there is no sense
1976 in pushing your luck. For more information, see @ref{Optimized Code}.
1978 Older versions of the @sc{gnu} C compiler permitted a variant option
1979 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1980 format; if your @sc{gnu} C compiler has this option, do not use it.
1982 @value{GDBN} knows about preprocessor macros and can show you their
1983 expansion (@pxref{Macros}). Most compilers do not include information
1984 about preprocessor macros in the debugging information if you specify
1985 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1986 the @sc{gnu} C compiler, provides macro information if you are using
1987 the DWARF debugging format, and specify the option @option{-g3}.
1989 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1990 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1991 information on @value{NGCC} options affecting debug information.
1993 You will have the best debugging experience if you use the latest
1994 version of the DWARF debugging format that your compiler supports.
1995 DWARF is currently the most expressive and best supported debugging
1996 format in @value{GDBN}.
2000 @section Starting your Program
2006 @kindex r @r{(@code{run})}
2009 Use the @code{run} command to start your program under @value{GDBN}.
2010 You must first specify the program name with an argument to
2011 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2012 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2013 command (@pxref{Files, ,Commands to Specify Files}).
2017 If you are running your program in an execution environment that
2018 supports processes, @code{run} creates an inferior process and makes
2019 that process run your program. In some environments without processes,
2020 @code{run} jumps to the start of your program. Other targets,
2021 like @samp{remote}, are always running. If you get an error
2022 message like this one:
2025 The "remote" target does not support "run".
2026 Try "help target" or "continue".
2030 then use @code{continue} to run your program. You may need @code{load}
2031 first (@pxref{load}).
2033 The execution of a program is affected by certain information it
2034 receives from its superior. @value{GDBN} provides ways to specify this
2035 information, which you must do @emph{before} starting your program. (You
2036 can change it after starting your program, but such changes only affect
2037 your program the next time you start it.) This information may be
2038 divided into four categories:
2041 @item The @emph{arguments.}
2042 Specify the arguments to give your program as the arguments of the
2043 @code{run} command. If a shell is available on your target, the shell
2044 is used to pass the arguments, so that you may use normal conventions
2045 (such as wildcard expansion or variable substitution) in describing
2047 In Unix systems, you can control which shell is used with the
2048 @code{SHELL} environment variable. If you do not define @code{SHELL},
2049 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2050 use of any shell with the @code{set startup-with-shell} command (see
2053 @item The @emph{environment.}
2054 Your program normally inherits its environment from @value{GDBN}, but you can
2055 use the @value{GDBN} commands @code{set environment} and @code{unset
2056 environment} to change parts of the environment that affect
2057 your program. @xref{Environment, ,Your Program's Environment}.
2059 @item The @emph{working directory.}
2060 Your program inherits its working directory from @value{GDBN}. You can set
2061 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2062 @xref{Working Directory, ,Your Program's Working Directory}.
2064 @item The @emph{standard input and output.}
2065 Your program normally uses the same device for standard input and
2066 standard output as @value{GDBN} is using. You can redirect input and output
2067 in the @code{run} command line, or you can use the @code{tty} command to
2068 set a different device for your program.
2069 @xref{Input/Output, ,Your Program's Input and Output}.
2072 @emph{Warning:} While input and output redirection work, you cannot use
2073 pipes to pass the output of the program you are debugging to another
2074 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2078 When you issue the @code{run} command, your program begins to execute
2079 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2080 of how to arrange for your program to stop. Once your program has
2081 stopped, you may call functions in your program, using the @code{print}
2082 or @code{call} commands. @xref{Data, ,Examining Data}.
2084 If the modification time of your symbol file has changed since the last
2085 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2086 table, and reads it again. When it does this, @value{GDBN} tries to retain
2087 your current breakpoints.
2092 @cindex run to main procedure
2093 The name of the main procedure can vary from language to language.
2094 With C or C@t{++}, the main procedure name is always @code{main}, but
2095 other languages such as Ada do not require a specific name for their
2096 main procedure. The debugger provides a convenient way to start the
2097 execution of the program and to stop at the beginning of the main
2098 procedure, depending on the language used.
2100 The @samp{start} command does the equivalent of setting a temporary
2101 breakpoint at the beginning of the main procedure and then invoking
2102 the @samp{run} command.
2104 @cindex elaboration phase
2105 Some programs contain an @dfn{elaboration} phase where some startup code is
2106 executed before the main procedure is called. This depends on the
2107 languages used to write your program. In C@t{++}, for instance,
2108 constructors for static and global objects are executed before
2109 @code{main} is called. It is therefore possible that the debugger stops
2110 before reaching the main procedure. However, the temporary breakpoint
2111 will remain to halt execution.
2113 Specify the arguments to give to your program as arguments to the
2114 @samp{start} command. These arguments will be given verbatim to the
2115 underlying @samp{run} command. Note that the same arguments will be
2116 reused if no argument is provided during subsequent calls to
2117 @samp{start} or @samp{run}.
2119 It is sometimes necessary to debug the program during elaboration. In
2120 these cases, using the @code{start} command would stop the execution of
2121 your program too late, as the program would have already completed the
2122 elaboration phase. Under these circumstances, insert breakpoints in your
2123 elaboration code before running your program.
2125 @anchor{set exec-wrapper}
2126 @kindex set exec-wrapper
2127 @item set exec-wrapper @var{wrapper}
2128 @itemx show exec-wrapper
2129 @itemx unset exec-wrapper
2130 When @samp{exec-wrapper} is set, the specified wrapper is used to
2131 launch programs for debugging. @value{GDBN} starts your program
2132 with a shell command of the form @kbd{exec @var{wrapper}
2133 @var{program}}. Quoting is added to @var{program} and its
2134 arguments, but not to @var{wrapper}, so you should add quotes if
2135 appropriate for your shell. The wrapper runs until it executes
2136 your program, and then @value{GDBN} takes control.
2138 You can use any program that eventually calls @code{execve} with
2139 its arguments as a wrapper. Several standard Unix utilities do
2140 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2141 with @code{exec "$@@"} will also work.
2143 For example, you can use @code{env} to pass an environment variable to
2144 the debugged program, without setting the variable in your shell's
2148 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2152 This command is available when debugging locally on most targets, excluding
2153 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2155 @kindex set startup-with-shell
2156 @item set startup-with-shell
2157 @itemx set startup-with-shell on
2158 @itemx set startup-with-shell off
2159 @itemx show set startup-with-shell
2160 On Unix systems, by default, if a shell is available on your target,
2161 @value{GDBN}) uses it to start your program. Arguments of the
2162 @code{run} command are passed to the shell, which does variable
2163 substitution, expands wildcard characters and performs redirection of
2164 I/O. In some circumstances, it may be useful to disable such use of a
2165 shell, for example, when debugging the shell itself or diagnosing
2166 startup failures such as:
2170 Starting program: ./a.out
2171 During startup program terminated with signal SIGSEGV, Segmentation fault.
2175 which indicates the shell or the wrapper specified with
2176 @samp{exec-wrapper} crashed, not your program. Most often, this is
2177 caused by something odd in your shell's non-interactive mode
2178 initialization file---such as @file{.cshrc} for C-shell,
2179 $@file{.zshenv} for the Z shell, or the file specified in the
2180 @samp{BASH_ENV} environment variable for BASH.
2182 @anchor{set auto-connect-native-target}
2183 @kindex set auto-connect-native-target
2184 @item set auto-connect-native-target
2185 @itemx set auto-connect-native-target on
2186 @itemx set auto-connect-native-target off
2187 @itemx show auto-connect-native-target
2189 By default, if not connected to any target yet (e.g., with
2190 @code{target remote}), the @code{run} command starts your program as a
2191 native process under @value{GDBN}, on your local machine. If you're
2192 sure you don't want to debug programs on your local machine, you can
2193 tell @value{GDBN} to not connect to the native target automatically
2194 with the @code{set auto-connect-native-target off} command.
2196 If @code{on}, which is the default, and if @value{GDBN} is not
2197 connected to a target already, the @code{run} command automaticaly
2198 connects to the native target, if one is available.
2200 If @code{off}, and if @value{GDBN} is not connected to a target
2201 already, the @code{run} command fails with an error:
2205 Don't know how to run. Try "help target".
2208 If @value{GDBN} is already connected to a target, @value{GDBN} always
2209 uses it with the @code{run} command.
2211 In any case, you can explicitly connect to the native target with the
2212 @code{target native} command. For example,
2215 (@value{GDBP}) set auto-connect-native-target off
2217 Don't know how to run. Try "help target".
2218 (@value{GDBP}) target native
2220 Starting program: ./a.out
2221 [Inferior 1 (process 10421) exited normally]
2224 In case you connected explicitly to the @code{native} target,
2225 @value{GDBN} remains connected even if all inferiors exit, ready for
2226 the next @code{run} command. Use the @code{disconnect} command to
2229 Examples of other commands that likewise respect the
2230 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2231 proc}, @code{info os}.
2233 @kindex set disable-randomization
2234 @item set disable-randomization
2235 @itemx set disable-randomization on
2236 This option (enabled by default in @value{GDBN}) will turn off the native
2237 randomization of the virtual address space of the started program. This option
2238 is useful for multiple debugging sessions to make the execution better
2239 reproducible and memory addresses reusable across debugging sessions.
2241 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2242 On @sc{gnu}/Linux you can get the same behavior using
2245 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2248 @item set disable-randomization off
2249 Leave the behavior of the started executable unchanged. Some bugs rear their
2250 ugly heads only when the program is loaded at certain addresses. If your bug
2251 disappears when you run the program under @value{GDBN}, that might be because
2252 @value{GDBN} by default disables the address randomization on platforms, such
2253 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2254 disable-randomization off} to try to reproduce such elusive bugs.
2256 On targets where it is available, virtual address space randomization
2257 protects the programs against certain kinds of security attacks. In these
2258 cases the attacker needs to know the exact location of a concrete executable
2259 code. Randomizing its location makes it impossible to inject jumps misusing
2260 a code at its expected addresses.
2262 Prelinking shared libraries provides a startup performance advantage but it
2263 makes addresses in these libraries predictable for privileged processes by
2264 having just unprivileged access at the target system. Reading the shared
2265 library binary gives enough information for assembling the malicious code
2266 misusing it. Still even a prelinked shared library can get loaded at a new
2267 random address just requiring the regular relocation process during the
2268 startup. Shared libraries not already prelinked are always loaded at
2269 a randomly chosen address.
2271 Position independent executables (PIE) contain position independent code
2272 similar to the shared libraries and therefore such executables get loaded at
2273 a randomly chosen address upon startup. PIE executables always load even
2274 already prelinked shared libraries at a random address. You can build such
2275 executable using @command{gcc -fPIE -pie}.
2277 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2278 (as long as the randomization is enabled).
2280 @item show disable-randomization
2281 Show the current setting of the explicit disable of the native randomization of
2282 the virtual address space of the started program.
2287 @section Your Program's Arguments
2289 @cindex arguments (to your program)
2290 The arguments to your program can be specified by the arguments of the
2292 They are passed to a shell, which expands wildcard characters and
2293 performs redirection of I/O, and thence to your program. Your
2294 @code{SHELL} environment variable (if it exists) specifies what shell
2295 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2296 the default shell (@file{/bin/sh} on Unix).
2298 On non-Unix systems, the program is usually invoked directly by
2299 @value{GDBN}, which emulates I/O redirection via the appropriate system
2300 calls, and the wildcard characters are expanded by the startup code of
2301 the program, not by the shell.
2303 @code{run} with no arguments uses the same arguments used by the previous
2304 @code{run}, or those set by the @code{set args} command.
2309 Specify the arguments to be used the next time your program is run. If
2310 @code{set args} has no arguments, @code{run} executes your program
2311 with no arguments. Once you have run your program with arguments,
2312 using @code{set args} before the next @code{run} is the only way to run
2313 it again without arguments.
2317 Show the arguments to give your program when it is started.
2321 @section Your Program's Environment
2323 @cindex environment (of your program)
2324 The @dfn{environment} consists of a set of environment variables and
2325 their values. Environment variables conventionally record such things as
2326 your user name, your home directory, your terminal type, and your search
2327 path for programs to run. Usually you set up environment variables with
2328 the shell and they are inherited by all the other programs you run. When
2329 debugging, it can be useful to try running your program with a modified
2330 environment without having to start @value{GDBN} over again.
2334 @item path @var{directory}
2335 Add @var{directory} to the front of the @code{PATH} environment variable
2336 (the search path for executables) that will be passed to your program.
2337 The value of @code{PATH} used by @value{GDBN} does not change.
2338 You may specify several directory names, separated by whitespace or by a
2339 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2340 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2341 is moved to the front, so it is searched sooner.
2343 You can use the string @samp{$cwd} to refer to whatever is the current
2344 working directory at the time @value{GDBN} searches the path. If you
2345 use @samp{.} instead, it refers to the directory where you executed the
2346 @code{path} command. @value{GDBN} replaces @samp{.} in the
2347 @var{directory} argument (with the current path) before adding
2348 @var{directory} to the search path.
2349 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2350 @c document that, since repeating it would be a no-op.
2354 Display the list of search paths for executables (the @code{PATH}
2355 environment variable).
2357 @kindex show environment
2358 @item show environment @r{[}@var{varname}@r{]}
2359 Print the value of environment variable @var{varname} to be given to
2360 your program when it starts. If you do not supply @var{varname},
2361 print the names and values of all environment variables to be given to
2362 your program. You can abbreviate @code{environment} as @code{env}.
2364 @kindex set environment
2365 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2366 Set environment variable @var{varname} to @var{value}. The value
2367 changes for your program (and the shell @value{GDBN} uses to launch
2368 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2369 values of environment variables are just strings, and any
2370 interpretation is supplied by your program itself. The @var{value}
2371 parameter is optional; if it is eliminated, the variable is set to a
2373 @c "any string" here does not include leading, trailing
2374 @c blanks. Gnu asks: does anyone care?
2376 For example, this command:
2383 tells the debugged program, when subsequently run, that its user is named
2384 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2385 are not actually required.)
2387 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2388 which also inherits the environment set with @code{set environment}.
2389 If necessary, you can avoid that by using the @samp{env} program as a
2390 wrapper instead of using @code{set environment}. @xref{set
2391 exec-wrapper}, for an example doing just that.
2393 @kindex unset environment
2394 @item unset environment @var{varname}
2395 Remove variable @var{varname} from the environment to be passed to your
2396 program. This is different from @samp{set env @var{varname} =};
2397 @code{unset environment} removes the variable from the environment,
2398 rather than assigning it an empty value.
2401 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2402 the shell indicated by your @code{SHELL} environment variable if it
2403 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2404 names a shell that runs an initialization file when started
2405 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2406 for the Z shell, or the file specified in the @samp{BASH_ENV}
2407 environment variable for BASH---any variables you set in that file
2408 affect your program. You may wish to move setting of environment
2409 variables to files that are only run when you sign on, such as
2410 @file{.login} or @file{.profile}.
2412 @node Working Directory
2413 @section Your Program's Working Directory
2415 @cindex working directory (of your program)
2416 Each time you start your program with @code{run}, it inherits its
2417 working directory from the current working directory of @value{GDBN}.
2418 The @value{GDBN} working directory is initially whatever it inherited
2419 from its parent process (typically the shell), but you can specify a new
2420 working directory in @value{GDBN} with the @code{cd} command.
2422 The @value{GDBN} working directory also serves as a default for the commands
2423 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2428 @cindex change working directory
2429 @item cd @r{[}@var{directory}@r{]}
2430 Set the @value{GDBN} working directory to @var{directory}. If not
2431 given, @var{directory} uses @file{'~'}.
2435 Print the @value{GDBN} working directory.
2438 It is generally impossible to find the current working directory of
2439 the process being debugged (since a program can change its directory
2440 during its run). If you work on a system where @value{GDBN} is
2441 configured with the @file{/proc} support, you can use the @code{info
2442 proc} command (@pxref{SVR4 Process Information}) to find out the
2443 current working directory of the debuggee.
2446 @section Your Program's Input and Output
2451 By default, the program you run under @value{GDBN} does input and output to
2452 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2453 to its own terminal modes to interact with you, but it records the terminal
2454 modes your program was using and switches back to them when you continue
2455 running your program.
2458 @kindex info terminal
2460 Displays information recorded by @value{GDBN} about the terminal modes your
2464 You can redirect your program's input and/or output using shell
2465 redirection with the @code{run} command. For example,
2472 starts your program, diverting its output to the file @file{outfile}.
2475 @cindex controlling terminal
2476 Another way to specify where your program should do input and output is
2477 with the @code{tty} command. This command accepts a file name as
2478 argument, and causes this file to be the default for future @code{run}
2479 commands. It also resets the controlling terminal for the child
2480 process, for future @code{run} commands. For example,
2487 directs that processes started with subsequent @code{run} commands
2488 default to do input and output on the terminal @file{/dev/ttyb} and have
2489 that as their controlling terminal.
2491 An explicit redirection in @code{run} overrides the @code{tty} command's
2492 effect on the input/output device, but not its effect on the controlling
2495 When you use the @code{tty} command or redirect input in the @code{run}
2496 command, only the input @emph{for your program} is affected. The input
2497 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2498 for @code{set inferior-tty}.
2500 @cindex inferior tty
2501 @cindex set inferior controlling terminal
2502 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2503 display the name of the terminal that will be used for future runs of your
2507 @item set inferior-tty [ @var{tty} ]
2508 @kindex set inferior-tty
2509 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2510 restores the default behavior, which is to use the same terminal as
2513 @item show inferior-tty
2514 @kindex show inferior-tty
2515 Show the current tty for the program being debugged.
2519 @section Debugging an Already-running Process
2524 @item attach @var{process-id}
2525 This command attaches to a running process---one that was started
2526 outside @value{GDBN}. (@code{info files} shows your active
2527 targets.) The command takes as argument a process ID. The usual way to
2528 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2529 or with the @samp{jobs -l} shell command.
2531 @code{attach} does not repeat if you press @key{RET} a second time after
2532 executing the command.
2535 To use @code{attach}, your program must be running in an environment
2536 which supports processes; for example, @code{attach} does not work for
2537 programs on bare-board targets that lack an operating system. You must
2538 also have permission to send the process a signal.
2540 When you use @code{attach}, the debugger finds the program running in
2541 the process first by looking in the current working directory, then (if
2542 the program is not found) by using the source file search path
2543 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2544 the @code{file} command to load the program. @xref{Files, ,Commands to
2547 The first thing @value{GDBN} does after arranging to debug the specified
2548 process is to stop it. You can examine and modify an attached process
2549 with all the @value{GDBN} commands that are ordinarily available when
2550 you start processes with @code{run}. You can insert breakpoints; you
2551 can step and continue; you can modify storage. If you would rather the
2552 process continue running, you may use the @code{continue} command after
2553 attaching @value{GDBN} to the process.
2558 When you have finished debugging the attached process, you can use the
2559 @code{detach} command to release it from @value{GDBN} control. Detaching
2560 the process continues its execution. After the @code{detach} command,
2561 that process and @value{GDBN} become completely independent once more, and you
2562 are ready to @code{attach} another process or start one with @code{run}.
2563 @code{detach} does not repeat if you press @key{RET} again after
2564 executing the command.
2567 If you exit @value{GDBN} while you have an attached process, you detach
2568 that process. If you use the @code{run} command, you kill that process.
2569 By default, @value{GDBN} asks for confirmation if you try to do either of these
2570 things; you can control whether or not you need to confirm by using the
2571 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2575 @section Killing the Child Process
2580 Kill the child process in which your program is running under @value{GDBN}.
2583 This command is useful if you wish to debug a core dump instead of a
2584 running process. @value{GDBN} ignores any core dump file while your program
2587 On some operating systems, a program cannot be executed outside @value{GDBN}
2588 while you have breakpoints set on it inside @value{GDBN}. You can use the
2589 @code{kill} command in this situation to permit running your program
2590 outside the debugger.
2592 The @code{kill} command is also useful if you wish to recompile and
2593 relink your program, since on many systems it is impossible to modify an
2594 executable file while it is running in a process. In this case, when you
2595 next type @code{run}, @value{GDBN} notices that the file has changed, and
2596 reads the symbol table again (while trying to preserve your current
2597 breakpoint settings).
2599 @node Inferiors and Programs
2600 @section Debugging Multiple Inferiors and Programs
2602 @value{GDBN} lets you run and debug multiple programs in a single
2603 session. In addition, @value{GDBN} on some systems may let you run
2604 several programs simultaneously (otherwise you have to exit from one
2605 before starting another). In the most general case, you can have
2606 multiple threads of execution in each of multiple processes, launched
2607 from multiple executables.
2610 @value{GDBN} represents the state of each program execution with an
2611 object called an @dfn{inferior}. An inferior typically corresponds to
2612 a process, but is more general and applies also to targets that do not
2613 have processes. Inferiors may be created before a process runs, and
2614 may be retained after a process exits. Inferiors have unique
2615 identifiers that are different from process ids. Usually each
2616 inferior will also have its own distinct address space, although some
2617 embedded targets may have several inferiors running in different parts
2618 of a single address space. Each inferior may in turn have multiple
2619 threads running in it.
2621 To find out what inferiors exist at any moment, use @w{@code{info
2625 @kindex info inferiors
2626 @item info inferiors
2627 Print a list of all inferiors currently being managed by @value{GDBN}.
2629 @value{GDBN} displays for each inferior (in this order):
2633 the inferior number assigned by @value{GDBN}
2636 the target system's inferior identifier
2639 the name of the executable the inferior is running.
2644 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2645 indicates the current inferior.
2649 @c end table here to get a little more width for example
2652 (@value{GDBP}) info inferiors
2653 Num Description Executable
2654 2 process 2307 hello
2655 * 1 process 3401 goodbye
2658 To switch focus between inferiors, use the @code{inferior} command:
2661 @kindex inferior @var{infno}
2662 @item inferior @var{infno}
2663 Make inferior number @var{infno} the current inferior. The argument
2664 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2665 in the first field of the @samp{info inferiors} display.
2668 @vindex $_inferior@r{, convenience variable}
2669 The debugger convenience variable @samp{$_inferior} contains the
2670 number of the current inferior. You may find this useful in writing
2671 breakpoint conditional expressions, command scripts, and so forth.
2672 @xref{Convenience Vars,, Convenience Variables}, for general
2673 information on convenience variables.
2675 You can get multiple executables into a debugging session via the
2676 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2677 systems @value{GDBN} can add inferiors to the debug session
2678 automatically by following calls to @code{fork} and @code{exec}. To
2679 remove inferiors from the debugging session use the
2680 @w{@code{remove-inferiors}} command.
2683 @kindex add-inferior
2684 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2685 Adds @var{n} inferiors to be run using @var{executable} as the
2686 executable; @var{n} defaults to 1. If no executable is specified,
2687 the inferiors begins empty, with no program. You can still assign or
2688 change the program assigned to the inferior at any time by using the
2689 @code{file} command with the executable name as its argument.
2691 @kindex clone-inferior
2692 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2693 Adds @var{n} inferiors ready to execute the same program as inferior
2694 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2695 number of the current inferior. This is a convenient command when you
2696 want to run another instance of the inferior you are debugging.
2699 (@value{GDBP}) info inferiors
2700 Num Description Executable
2701 * 1 process 29964 helloworld
2702 (@value{GDBP}) clone-inferior
2705 (@value{GDBP}) info inferiors
2706 Num Description Executable
2708 * 1 process 29964 helloworld
2711 You can now simply switch focus to inferior 2 and run it.
2713 @kindex remove-inferiors
2714 @item remove-inferiors @var{infno}@dots{}
2715 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2716 possible to remove an inferior that is running with this command. For
2717 those, use the @code{kill} or @code{detach} command first.
2721 To quit debugging one of the running inferiors that is not the current
2722 inferior, you can either detach from it by using the @w{@code{detach
2723 inferior}} command (allowing it to run independently), or kill it
2724 using the @w{@code{kill inferiors}} command:
2727 @kindex detach inferiors @var{infno}@dots{}
2728 @item detach inferior @var{infno}@dots{}
2729 Detach from the inferior or inferiors identified by @value{GDBN}
2730 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2731 still stays on the list of inferiors shown by @code{info inferiors},
2732 but its Description will show @samp{<null>}.
2734 @kindex kill inferiors @var{infno}@dots{}
2735 @item kill inferiors @var{infno}@dots{}
2736 Kill the inferior or inferiors identified by @value{GDBN} inferior
2737 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2738 stays on the list of inferiors shown by @code{info inferiors}, but its
2739 Description will show @samp{<null>}.
2742 After the successful completion of a command such as @code{detach},
2743 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2744 a normal process exit, the inferior is still valid and listed with
2745 @code{info inferiors}, ready to be restarted.
2748 To be notified when inferiors are started or exit under @value{GDBN}'s
2749 control use @w{@code{set print inferior-events}}:
2752 @kindex set print inferior-events
2753 @cindex print messages on inferior start and exit
2754 @item set print inferior-events
2755 @itemx set print inferior-events on
2756 @itemx set print inferior-events off
2757 The @code{set print inferior-events} command allows you to enable or
2758 disable printing of messages when @value{GDBN} notices that new
2759 inferiors have started or that inferiors have exited or have been
2760 detached. By default, these messages will not be printed.
2762 @kindex show print inferior-events
2763 @item show print inferior-events
2764 Show whether messages will be printed when @value{GDBN} detects that
2765 inferiors have started, exited or have been detached.
2768 Many commands will work the same with multiple programs as with a
2769 single program: e.g., @code{print myglobal} will simply display the
2770 value of @code{myglobal} in the current inferior.
2773 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2774 get more info about the relationship of inferiors, programs, address
2775 spaces in a debug session. You can do that with the @w{@code{maint
2776 info program-spaces}} command.
2779 @kindex maint info program-spaces
2780 @item maint info program-spaces
2781 Print a list of all program spaces currently being managed by
2784 @value{GDBN} displays for each program space (in this order):
2788 the program space number assigned by @value{GDBN}
2791 the name of the executable loaded into the program space, with e.g.,
2792 the @code{file} command.
2797 An asterisk @samp{*} preceding the @value{GDBN} program space number
2798 indicates the current program space.
2800 In addition, below each program space line, @value{GDBN} prints extra
2801 information that isn't suitable to display in tabular form. For
2802 example, the list of inferiors bound to the program space.
2805 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 1 (process 21561)
2812 Here we can see that no inferior is running the program @code{hello},
2813 while @code{process 21561} is running the program @code{goodbye}. On
2814 some targets, it is possible that multiple inferiors are bound to the
2815 same program space. The most common example is that of debugging both
2816 the parent and child processes of a @code{vfork} call. For example,
2819 (@value{GDBP}) maint info program-spaces
2822 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2825 Here, both inferior 2 and inferior 1 are running in the same program
2826 space as a result of inferior 1 having executed a @code{vfork} call.
2830 @section Debugging Programs with Multiple Threads
2832 @cindex threads of execution
2833 @cindex multiple threads
2834 @cindex switching threads
2835 In some operating systems, such as GNU/Linux and Solaris, a single program
2836 may have more than one @dfn{thread} of execution. The precise semantics
2837 of threads differ from one operating system to another, but in general
2838 the threads of a single program are akin to multiple processes---except
2839 that they share one address space (that is, they can all examine and
2840 modify the same variables). On the other hand, each thread has its own
2841 registers and execution stack, and perhaps private memory.
2843 @value{GDBN} provides these facilities for debugging multi-thread
2847 @item automatic notification of new threads
2848 @item @samp{thread @var{thread-id}}, a command to switch among threads
2849 @item @samp{info threads}, a command to inquire about existing threads
2850 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2851 a command to apply a command to a list of threads
2852 @item thread-specific breakpoints
2853 @item @samp{set print thread-events}, which controls printing of
2854 messages on thread start and exit.
2855 @item @samp{set libthread-db-search-path @var{path}}, which lets
2856 the user specify which @code{libthread_db} to use if the default choice
2857 isn't compatible with the program.
2860 @cindex focus of debugging
2861 @cindex current thread
2862 The @value{GDBN} thread debugging facility allows you to observe all
2863 threads while your program runs---but whenever @value{GDBN} takes
2864 control, one thread in particular is always the focus of debugging.
2865 This thread is called the @dfn{current thread}. Debugging commands show
2866 program information from the perspective of the current thread.
2868 @cindex @code{New} @var{systag} message
2869 @cindex thread identifier (system)
2870 @c FIXME-implementors!! It would be more helpful if the [New...] message
2871 @c included GDB's numeric thread handle, so you could just go to that
2872 @c thread without first checking `info threads'.
2873 Whenever @value{GDBN} detects a new thread in your program, it displays
2874 the target system's identification for the thread with a message in the
2875 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2876 whose form varies depending on the particular system. For example, on
2877 @sc{gnu}/Linux, you might see
2880 [New Thread 0x41e02940 (LWP 25582)]
2884 when @value{GDBN} notices a new thread. In contrast, on other systems,
2885 the @var{systag} is simply something like @samp{process 368}, with no
2888 @c FIXME!! (1) Does the [New...] message appear even for the very first
2889 @c thread of a program, or does it only appear for the
2890 @c second---i.e.@: when it becomes obvious we have a multithread
2892 @c (2) *Is* there necessarily a first thread always? Or do some
2893 @c multithread systems permit starting a program with multiple
2894 @c threads ab initio?
2896 @anchor{thread numbers}
2897 @cindex thread number, per inferior
2898 @cindex thread identifier (GDB)
2899 For debugging purposes, @value{GDBN} associates its own thread number
2900 ---always a single integer---with each thread of an inferior. This
2901 number is unique between all threads of an inferior, but not unique
2902 between threads of different inferiors.
2904 @cindex qualified thread ID
2905 You can refer to a given thread in an inferior using the qualified
2906 @var{inferior-num}.@var{thread-num} syntax, also known as
2907 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2908 number and @var{thread-num} being the thread number of the given
2909 inferior. For example, thread @code{2.3} refers to thread number 3 of
2910 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2911 then @value{GDBN} infers you're referring to a thread of the current
2914 Until you create a second inferior, @value{GDBN} does not show the
2915 @var{inferior-num} part of thread IDs, even though you can always use
2916 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2917 of inferior 1, the initial inferior.
2919 @anchor{thread ID lists}
2920 @cindex thread ID lists
2921 Some commands accept a space-separated @dfn{thread ID list} as
2922 argument. A list element can be:
2926 A thread ID as shown in the first field of the @samp{info threads}
2927 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2931 A range of thread numbers, again with or without an inferior
2932 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2933 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2936 All threads of an inferior, specified with a star wildcard, with or
2937 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2938 @samp{1.*}) or @code{*}. The former refers to all threads of the
2939 given inferior, and the latter form without an inferior qualifier
2940 refers to all threads of the current inferior.
2944 For example, if the current inferior is 1, and inferior 7 has one
2945 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2946 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2947 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2948 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2952 @anchor{global thread numbers}
2953 @cindex global thread number
2954 @cindex global thread identifier (GDB)
2955 In addition to a @emph{per-inferior} number, each thread is also
2956 assigned a unique @emph{global} number, also known as @dfn{global
2957 thread ID}, a single integer. Unlike the thread number component of
2958 the thread ID, no two threads have the same global ID, even when
2959 you're debugging multiple inferiors.
2961 From @value{GDBN}'s perspective, a process always has at least one
2962 thread. In other words, @value{GDBN} assigns a thread number to the
2963 program's ``main thread'' even if the program is not multi-threaded.
2965 @vindex $_thread@r{, convenience variable}
2966 @vindex $_gthread@r{, convenience variable}
2967 The debugger convenience variables @samp{$_thread} and
2968 @samp{$_gthread} contain, respectively, the per-inferior thread number
2969 and the global thread number of the current thread. You may find this
2970 useful in writing breakpoint conditional expressions, command scripts,
2971 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2972 general information on convenience variables.
2974 If @value{GDBN} detects the program is multi-threaded, it augments the
2975 usual message about stopping at a breakpoint with the ID and name of
2976 the thread that hit the breakpoint.
2979 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2982 Likewise when the program receives a signal:
2985 Thread 1 "main" received signal SIGINT, Interrupt.
2989 @kindex info threads
2990 @item info threads @r{[}@var{thread-id-list}@r{]}
2992 Display information about one or more threads. With no arguments
2993 displays information about all threads. You can specify the list of
2994 threads that you want to display using the thread ID list syntax
2995 (@pxref{thread ID lists}).
2997 @value{GDBN} displays for each thread (in this order):
3001 the per-inferior thread number assigned by @value{GDBN}
3004 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3005 option was specified
3008 the target system's thread identifier (@var{systag})
3011 the thread's name, if one is known. A thread can either be named by
3012 the user (see @code{thread name}, below), or, in some cases, by the
3016 the current stack frame summary for that thread
3020 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3021 indicates the current thread.
3025 @c end table here to get a little more width for example
3028 (@value{GDBP}) info threads
3030 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3031 2 process 35 thread 23 0x34e5 in sigpause ()
3032 3 process 35 thread 27 0x34e5 in sigpause ()
3036 If you're debugging multiple inferiors, @value{GDBN} displays thread
3037 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3038 Otherwise, only @var{thread-num} is shown.
3040 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3041 indicating each thread's global thread ID:
3044 (@value{GDBP}) info threads
3045 Id GId Target Id Frame
3046 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3047 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3048 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3049 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3052 On Solaris, you can display more information about user threads with a
3053 Solaris-specific command:
3056 @item maint info sol-threads
3057 @kindex maint info sol-threads
3058 @cindex thread info (Solaris)
3059 Display info on Solaris user threads.
3063 @kindex thread @var{thread-id}
3064 @item thread @var{thread-id}
3065 Make thread ID @var{thread-id} the current thread. The command
3066 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3067 the first field of the @samp{info threads} display, with or without an
3068 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3070 @value{GDBN} responds by displaying the system identifier of the
3071 thread you selected, and its current stack frame summary:
3074 (@value{GDBP}) thread 2
3075 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3076 #0 some_function (ignore=0x0) at example.c:8
3077 8 printf ("hello\n");
3081 As with the @samp{[New @dots{}]} message, the form of the text after
3082 @samp{Switching to} depends on your system's conventions for identifying
3085 @kindex thread apply
3086 @cindex apply command to several threads
3087 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3088 The @code{thread apply} command allows you to apply the named
3089 @var{command} to one or more threads. Specify the threads that you
3090 want affected using the thread ID list syntax (@pxref{thread ID
3091 lists}), or specify @code{all} to apply to all threads. To apply a
3092 command to all threads in descending order, type @kbd{thread apply all
3093 @var{command}}. To apply a command to all threads in ascending order,
3094 type @kbd{thread apply all -ascending @var{command}}.
3098 @cindex name a thread
3099 @item thread name [@var{name}]
3100 This command assigns a name to the current thread. If no argument is
3101 given, any existing user-specified name is removed. The thread name
3102 appears in the @samp{info threads} display.
3104 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3105 determine the name of the thread as given by the OS. On these
3106 systems, a name specified with @samp{thread name} will override the
3107 system-give name, and removing the user-specified name will cause
3108 @value{GDBN} to once again display the system-specified name.
3111 @cindex search for a thread
3112 @item thread find [@var{regexp}]
3113 Search for and display thread ids whose name or @var{systag}
3114 matches the supplied regular expression.
3116 As well as being the complement to the @samp{thread name} command,
3117 this command also allows you to identify a thread by its target
3118 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3122 (@value{GDBN}) thread find 26688
3123 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3124 (@value{GDBN}) info thread 4
3126 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3129 @kindex set print thread-events
3130 @cindex print messages on thread start and exit
3131 @item set print thread-events
3132 @itemx set print thread-events on
3133 @itemx set print thread-events off
3134 The @code{set print thread-events} command allows you to enable or
3135 disable printing of messages when @value{GDBN} notices that new threads have
3136 started or that threads have exited. By default, these messages will
3137 be printed if detection of these events is supported by the target.
3138 Note that these messages cannot be disabled on all targets.
3140 @kindex show print thread-events
3141 @item show print thread-events
3142 Show whether messages will be printed when @value{GDBN} detects that threads
3143 have started and exited.
3146 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3147 more information about how @value{GDBN} behaves when you stop and start
3148 programs with multiple threads.
3150 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3151 watchpoints in programs with multiple threads.
3153 @anchor{set libthread-db-search-path}
3155 @kindex set libthread-db-search-path
3156 @cindex search path for @code{libthread_db}
3157 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3158 If this variable is set, @var{path} is a colon-separated list of
3159 directories @value{GDBN} will use to search for @code{libthread_db}.
3160 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3161 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3162 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3165 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3166 @code{libthread_db} library to obtain information about threads in the
3167 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3168 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3169 specific thread debugging library loading is enabled
3170 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3172 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3173 refers to the default system directories that are
3174 normally searched for loading shared libraries. The @samp{$sdir} entry
3175 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3176 (@pxref{libthread_db.so.1 file}).
3178 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3179 refers to the directory from which @code{libpthread}
3180 was loaded in the inferior process.
3182 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3183 @value{GDBN} attempts to initialize it with the current inferior process.
3184 If this initialization fails (which could happen because of a version
3185 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3186 will unload @code{libthread_db}, and continue with the next directory.
3187 If none of @code{libthread_db} libraries initialize successfully,
3188 @value{GDBN} will issue a warning and thread debugging will be disabled.
3190 Setting @code{libthread-db-search-path} is currently implemented
3191 only on some platforms.
3193 @kindex show libthread-db-search-path
3194 @item show libthread-db-search-path
3195 Display current libthread_db search path.
3197 @kindex set debug libthread-db
3198 @kindex show debug libthread-db
3199 @cindex debugging @code{libthread_db}
3200 @item set debug libthread-db
3201 @itemx show debug libthread-db
3202 Turns on or off display of @code{libthread_db}-related events.
3203 Use @code{1} to enable, @code{0} to disable.
3207 @section Debugging Forks
3209 @cindex fork, debugging programs which call
3210 @cindex multiple processes
3211 @cindex processes, multiple
3212 On most systems, @value{GDBN} has no special support for debugging
3213 programs which create additional processes using the @code{fork}
3214 function. When a program forks, @value{GDBN} will continue to debug the
3215 parent process and the child process will run unimpeded. If you have
3216 set a breakpoint in any code which the child then executes, the child
3217 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3218 will cause it to terminate.
3220 However, if you want to debug the child process there is a workaround
3221 which isn't too painful. Put a call to @code{sleep} in the code which
3222 the child process executes after the fork. It may be useful to sleep
3223 only if a certain environment variable is set, or a certain file exists,
3224 so that the delay need not occur when you don't want to run @value{GDBN}
3225 on the child. While the child is sleeping, use the @code{ps} program to
3226 get its process ID. Then tell @value{GDBN} (a new invocation of
3227 @value{GDBN} if you are also debugging the parent process) to attach to
3228 the child process (@pxref{Attach}). From that point on you can debug
3229 the child process just like any other process which you attached to.
3231 On some systems, @value{GDBN} provides support for debugging programs
3232 that create additional processes using the @code{fork} or @code{vfork}
3233 functions. On @sc{gnu}/Linux platforms, this feature is supported
3234 with kernel version 2.5.46 and later.
3236 The fork debugging commands are supported in native mode and when
3237 connected to @code{gdbserver} in either @code{target remote} mode or
3238 @code{target extended-remote} mode.
3240 By default, when a program forks, @value{GDBN} will continue to debug
3241 the parent process and the child process will run unimpeded.
3243 If you want to follow the child process instead of the parent process,
3244 use the command @w{@code{set follow-fork-mode}}.
3247 @kindex set follow-fork-mode
3248 @item set follow-fork-mode @var{mode}
3249 Set the debugger response to a program call of @code{fork} or
3250 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3251 process. The @var{mode} argument can be:
3255 The original process is debugged after a fork. The child process runs
3256 unimpeded. This is the default.
3259 The new process is debugged after a fork. The parent process runs
3264 @kindex show follow-fork-mode
3265 @item show follow-fork-mode
3266 Display the current debugger response to a @code{fork} or @code{vfork} call.
3269 @cindex debugging multiple processes
3270 On Linux, if you want to debug both the parent and child processes, use the
3271 command @w{@code{set detach-on-fork}}.
3274 @kindex set detach-on-fork
3275 @item set detach-on-fork @var{mode}
3276 Tells gdb whether to detach one of the processes after a fork, or
3277 retain debugger control over them both.
3281 The child process (or parent process, depending on the value of
3282 @code{follow-fork-mode}) will be detached and allowed to run
3283 independently. This is the default.
3286 Both processes will be held under the control of @value{GDBN}.
3287 One process (child or parent, depending on the value of
3288 @code{follow-fork-mode}) is debugged as usual, while the other
3293 @kindex show detach-on-fork
3294 @item show detach-on-fork
3295 Show whether detach-on-fork mode is on/off.
3298 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3299 will retain control of all forked processes (including nested forks).
3300 You can list the forked processes under the control of @value{GDBN} by
3301 using the @w{@code{info inferiors}} command, and switch from one fork
3302 to another by using the @code{inferior} command (@pxref{Inferiors and
3303 Programs, ,Debugging Multiple Inferiors and Programs}).
3305 To quit debugging one of the forked processes, you can either detach
3306 from it by using the @w{@code{detach inferiors}} command (allowing it
3307 to run independently), or kill it using the @w{@code{kill inferiors}}
3308 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3311 If you ask to debug a child process and a @code{vfork} is followed by an
3312 @code{exec}, @value{GDBN} executes the new target up to the first
3313 breakpoint in the new target. If you have a breakpoint set on
3314 @code{main} in your original program, the breakpoint will also be set on
3315 the child process's @code{main}.
3317 On some systems, when a child process is spawned by @code{vfork}, you
3318 cannot debug the child or parent until an @code{exec} call completes.
3320 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3321 call executes, the new target restarts. To restart the parent
3322 process, use the @code{file} command with the parent executable name
3323 as its argument. By default, after an @code{exec} call executes,
3324 @value{GDBN} discards the symbols of the previous executable image.
3325 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3329 @kindex set follow-exec-mode
3330 @item set follow-exec-mode @var{mode}
3332 Set debugger response to a program call of @code{exec}. An
3333 @code{exec} call replaces the program image of a process.
3335 @code{follow-exec-mode} can be:
3339 @value{GDBN} creates a new inferior and rebinds the process to this
3340 new inferior. The program the process was running before the
3341 @code{exec} call can be restarted afterwards by restarting the
3347 (@value{GDBP}) info inferiors
3349 Id Description Executable
3352 process 12020 is executing new program: prog2
3353 Program exited normally.
3354 (@value{GDBP}) info inferiors
3355 Id Description Executable
3361 @value{GDBN} keeps the process bound to the same inferior. The new
3362 executable image replaces the previous executable loaded in the
3363 inferior. Restarting the inferior after the @code{exec} call, with
3364 e.g., the @code{run} command, restarts the executable the process was
3365 running after the @code{exec} call. This is the default mode.
3370 (@value{GDBP}) info inferiors
3371 Id Description Executable
3374 process 12020 is executing new program: prog2
3375 Program exited normally.
3376 (@value{GDBP}) info inferiors
3377 Id Description Executable
3384 @code{follow-exec-mode} is supported in native mode and
3385 @code{target extended-remote} mode.
3387 You can use the @code{catch} command to make @value{GDBN} stop whenever
3388 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3389 Catchpoints, ,Setting Catchpoints}.
3391 @node Checkpoint/Restart
3392 @section Setting a @emph{Bookmark} to Return to Later
3397 @cindex snapshot of a process
3398 @cindex rewind program state
3400 On certain operating systems@footnote{Currently, only
3401 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3402 program's state, called a @dfn{checkpoint}, and come back to it
3405 Returning to a checkpoint effectively undoes everything that has
3406 happened in the program since the @code{checkpoint} was saved. This
3407 includes changes in memory, registers, and even (within some limits)
3408 system state. Effectively, it is like going back in time to the
3409 moment when the checkpoint was saved.
3411 Thus, if you're stepping thru a program and you think you're
3412 getting close to the point where things go wrong, you can save
3413 a checkpoint. Then, if you accidentally go too far and miss
3414 the critical statement, instead of having to restart your program
3415 from the beginning, you can just go back to the checkpoint and
3416 start again from there.
3418 This can be especially useful if it takes a lot of time or
3419 steps to reach the point where you think the bug occurs.
3421 To use the @code{checkpoint}/@code{restart} method of debugging:
3426 Save a snapshot of the debugged program's current execution state.
3427 The @code{checkpoint} command takes no arguments, but each checkpoint
3428 is assigned a small integer id, similar to a breakpoint id.
3430 @kindex info checkpoints
3431 @item info checkpoints
3432 List the checkpoints that have been saved in the current debugging
3433 session. For each checkpoint, the following information will be
3440 @item Source line, or label
3443 @kindex restart @var{checkpoint-id}
3444 @item restart @var{checkpoint-id}
3445 Restore the program state that was saved as checkpoint number
3446 @var{checkpoint-id}. All program variables, registers, stack frames
3447 etc.@: will be returned to the values that they had when the checkpoint
3448 was saved. In essence, gdb will ``wind back the clock'' to the point
3449 in time when the checkpoint was saved.
3451 Note that breakpoints, @value{GDBN} variables, command history etc.
3452 are not affected by restoring a checkpoint. In general, a checkpoint
3453 only restores things that reside in the program being debugged, not in
3456 @kindex delete checkpoint @var{checkpoint-id}
3457 @item delete checkpoint @var{checkpoint-id}
3458 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3462 Returning to a previously saved checkpoint will restore the user state
3463 of the program being debugged, plus a significant subset of the system
3464 (OS) state, including file pointers. It won't ``un-write'' data from
3465 a file, but it will rewind the file pointer to the previous location,
3466 so that the previously written data can be overwritten. For files
3467 opened in read mode, the pointer will also be restored so that the
3468 previously read data can be read again.
3470 Of course, characters that have been sent to a printer (or other
3471 external device) cannot be ``snatched back'', and characters received
3472 from eg.@: a serial device can be removed from internal program buffers,
3473 but they cannot be ``pushed back'' into the serial pipeline, ready to
3474 be received again. Similarly, the actual contents of files that have
3475 been changed cannot be restored (at this time).
3477 However, within those constraints, you actually can ``rewind'' your
3478 program to a previously saved point in time, and begin debugging it
3479 again --- and you can change the course of events so as to debug a
3480 different execution path this time.
3482 @cindex checkpoints and process id
3483 Finally, there is one bit of internal program state that will be
3484 different when you return to a checkpoint --- the program's process
3485 id. Each checkpoint will have a unique process id (or @var{pid}),
3486 and each will be different from the program's original @var{pid}.
3487 If your program has saved a local copy of its process id, this could
3488 potentially pose a problem.
3490 @subsection A Non-obvious Benefit of Using Checkpoints
3492 On some systems such as @sc{gnu}/Linux, address space randomization
3493 is performed on new processes for security reasons. This makes it
3494 difficult or impossible to set a breakpoint, or watchpoint, on an
3495 absolute address if you have to restart the program, since the
3496 absolute location of a symbol will change from one execution to the
3499 A checkpoint, however, is an @emph{identical} copy of a process.
3500 Therefore if you create a checkpoint at (eg.@:) the start of main,
3501 and simply return to that checkpoint instead of restarting the
3502 process, you can avoid the effects of address randomization and
3503 your symbols will all stay in the same place.
3506 @chapter Stopping and Continuing
3508 The principal purposes of using a debugger are so that you can stop your
3509 program before it terminates; or so that, if your program runs into
3510 trouble, you can investigate and find out why.
3512 Inside @value{GDBN}, your program may stop for any of several reasons,
3513 such as a signal, a breakpoint, or reaching a new line after a
3514 @value{GDBN} command such as @code{step}. You may then examine and
3515 change variables, set new breakpoints or remove old ones, and then
3516 continue execution. Usually, the messages shown by @value{GDBN} provide
3517 ample explanation of the status of your program---but you can also
3518 explicitly request this information at any time.
3521 @kindex info program
3523 Display information about the status of your program: whether it is
3524 running or not, what process it is, and why it stopped.
3528 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3529 * Continuing and Stepping:: Resuming execution
3530 * Skipping Over Functions and Files::
3531 Skipping over functions and files
3533 * Thread Stops:: Stopping and starting multi-thread programs
3537 @section Breakpoints, Watchpoints, and Catchpoints
3540 A @dfn{breakpoint} makes your program stop whenever a certain point in
3541 the program is reached. For each breakpoint, you can add conditions to
3542 control in finer detail whether your program stops. You can set
3543 breakpoints with the @code{break} command and its variants (@pxref{Set
3544 Breaks, ,Setting Breakpoints}), to specify the place where your program
3545 should stop by line number, function name or exact address in the
3548 On some systems, you can set breakpoints in shared libraries before
3549 the executable is run.
3552 @cindex data breakpoints
3553 @cindex memory tracing
3554 @cindex breakpoint on memory address
3555 @cindex breakpoint on variable modification
3556 A @dfn{watchpoint} is a special breakpoint that stops your program
3557 when the value of an expression changes. The expression may be a value
3558 of a variable, or it could involve values of one or more variables
3559 combined by operators, such as @samp{a + b}. This is sometimes called
3560 @dfn{data breakpoints}. You must use a different command to set
3561 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3562 from that, you can manage a watchpoint like any other breakpoint: you
3563 enable, disable, and delete both breakpoints and watchpoints using the
3566 You can arrange to have values from your program displayed automatically
3567 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3571 @cindex breakpoint on events
3572 A @dfn{catchpoint} is another special breakpoint that stops your program
3573 when a certain kind of event occurs, such as the throwing of a C@t{++}
3574 exception or the loading of a library. As with watchpoints, you use a
3575 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3576 Catchpoints}), but aside from that, you can manage a catchpoint like any
3577 other breakpoint. (To stop when your program receives a signal, use the
3578 @code{handle} command; see @ref{Signals, ,Signals}.)
3580 @cindex breakpoint numbers
3581 @cindex numbers for breakpoints
3582 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3583 catchpoint when you create it; these numbers are successive integers
3584 starting with one. In many of the commands for controlling various
3585 features of breakpoints you use the breakpoint number to say which
3586 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3587 @dfn{disabled}; if disabled, it has no effect on your program until you
3590 @cindex breakpoint ranges
3591 @cindex ranges of breakpoints
3592 Some @value{GDBN} commands accept a range of breakpoints on which to
3593 operate. A breakpoint range is either a single breakpoint number, like
3594 @samp{5}, or two such numbers, in increasing order, separated by a
3595 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3596 all breakpoints in that range are operated on.
3599 * Set Breaks:: Setting breakpoints
3600 * Set Watchpoints:: Setting watchpoints
3601 * Set Catchpoints:: Setting catchpoints
3602 * Delete Breaks:: Deleting breakpoints
3603 * Disabling:: Disabling breakpoints
3604 * Conditions:: Break conditions
3605 * Break Commands:: Breakpoint command lists
3606 * Dynamic Printf:: Dynamic printf
3607 * Save Breakpoints:: How to save breakpoints in a file
3608 * Static Probe Points:: Listing static probe points
3609 * Error in Breakpoints:: ``Cannot insert breakpoints''
3610 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3614 @subsection Setting Breakpoints
3616 @c FIXME LMB what does GDB do if no code on line of breakpt?
3617 @c consider in particular declaration with/without initialization.
3619 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3622 @kindex b @r{(@code{break})}
3623 @vindex $bpnum@r{, convenience variable}
3624 @cindex latest breakpoint
3625 Breakpoints are set with the @code{break} command (abbreviated
3626 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3627 number of the breakpoint you've set most recently; see @ref{Convenience
3628 Vars,, Convenience Variables}, for a discussion of what you can do with
3629 convenience variables.
3632 @item break @var{location}
3633 Set a breakpoint at the given @var{location}, which can specify a
3634 function name, a line number, or an address of an instruction.
3635 (@xref{Specify Location}, for a list of all the possible ways to
3636 specify a @var{location}.) The breakpoint will stop your program just
3637 before it executes any of the code in the specified @var{location}.
3639 When using source languages that permit overloading of symbols, such as
3640 C@t{++}, a function name may refer to more than one possible place to break.
3641 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3644 It is also possible to insert a breakpoint that will stop the program
3645 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3646 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3649 When called without any arguments, @code{break} sets a breakpoint at
3650 the next instruction to be executed in the selected stack frame
3651 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3652 innermost, this makes your program stop as soon as control
3653 returns to that frame. This is similar to the effect of a
3654 @code{finish} command in the frame inside the selected frame---except
3655 that @code{finish} does not leave an active breakpoint. If you use
3656 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3657 the next time it reaches the current location; this may be useful
3660 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3661 least one instruction has been executed. If it did not do this, you
3662 would be unable to proceed past a breakpoint without first disabling the
3663 breakpoint. This rule applies whether or not the breakpoint already
3664 existed when your program stopped.
3666 @item break @dots{} if @var{cond}
3667 Set a breakpoint with condition @var{cond}; evaluate the expression
3668 @var{cond} each time the breakpoint is reached, and stop only if the
3669 value is nonzero---that is, if @var{cond} evaluates as true.
3670 @samp{@dots{}} stands for one of the possible arguments described
3671 above (or no argument) specifying where to break. @xref{Conditions,
3672 ,Break Conditions}, for more information on breakpoint conditions.
3675 @item tbreak @var{args}
3676 Set a breakpoint enabled only for one stop. The @var{args} are the
3677 same as for the @code{break} command, and the breakpoint is set in the same
3678 way, but the breakpoint is automatically deleted after the first time your
3679 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3682 @cindex hardware breakpoints
3683 @item hbreak @var{args}
3684 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3685 @code{break} command and the breakpoint is set in the same way, but the
3686 breakpoint requires hardware support and some target hardware may not
3687 have this support. The main purpose of this is EPROM/ROM code
3688 debugging, so you can set a breakpoint at an instruction without
3689 changing the instruction. This can be used with the new trap-generation
3690 provided by SPARClite DSU and most x86-based targets. These targets
3691 will generate traps when a program accesses some data or instruction
3692 address that is assigned to the debug registers. However the hardware
3693 breakpoint registers can take a limited number of breakpoints. For
3694 example, on the DSU, only two data breakpoints can be set at a time, and
3695 @value{GDBN} will reject this command if more than two are used. Delete
3696 or disable unused hardware breakpoints before setting new ones
3697 (@pxref{Disabling, ,Disabling Breakpoints}).
3698 @xref{Conditions, ,Break Conditions}.
3699 For remote targets, you can restrict the number of hardware
3700 breakpoints @value{GDBN} will use, see @ref{set remote
3701 hardware-breakpoint-limit}.
3704 @item thbreak @var{args}
3705 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3706 are the same as for the @code{hbreak} command and the breakpoint is set in
3707 the same way. However, like the @code{tbreak} command,
3708 the breakpoint is automatically deleted after the
3709 first time your program stops there. Also, like the @code{hbreak}
3710 command, the breakpoint requires hardware support and some target hardware
3711 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3712 See also @ref{Conditions, ,Break Conditions}.
3715 @cindex regular expression
3716 @cindex breakpoints at functions matching a regexp
3717 @cindex set breakpoints in many functions
3718 @item rbreak @var{regex}
3719 Set breakpoints on all functions matching the regular expression
3720 @var{regex}. This command sets an unconditional breakpoint on all
3721 matches, printing a list of all breakpoints it set. Once these
3722 breakpoints are set, they are treated just like the breakpoints set with
3723 the @code{break} command. You can delete them, disable them, or make
3724 them conditional the same way as any other breakpoint.
3726 The syntax of the regular expression is the standard one used with tools
3727 like @file{grep}. Note that this is different from the syntax used by
3728 shells, so for instance @code{foo*} matches all functions that include
3729 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3730 @code{.*} leading and trailing the regular expression you supply, so to
3731 match only functions that begin with @code{foo}, use @code{^foo}.
3733 @cindex non-member C@t{++} functions, set breakpoint in
3734 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3735 breakpoints on overloaded functions that are not members of any special
3738 @cindex set breakpoints on all functions
3739 The @code{rbreak} command can be used to set breakpoints in
3740 @strong{all} the functions in a program, like this:
3743 (@value{GDBP}) rbreak .
3746 @item rbreak @var{file}:@var{regex}
3747 If @code{rbreak} is called with a filename qualification, it limits
3748 the search for functions matching the given regular expression to the
3749 specified @var{file}. This can be used, for example, to set breakpoints on
3750 every function in a given file:
3753 (@value{GDBP}) rbreak file.c:.
3756 The colon separating the filename qualifier from the regex may
3757 optionally be surrounded by spaces.
3759 @kindex info breakpoints
3760 @cindex @code{$_} and @code{info breakpoints}
3761 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3762 @itemx info break @r{[}@var{n}@dots{}@r{]}
3763 Print a table of all breakpoints, watchpoints, and catchpoints set and
3764 not deleted. Optional argument @var{n} means print information only
3765 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3766 For each breakpoint, following columns are printed:
3769 @item Breakpoint Numbers
3771 Breakpoint, watchpoint, or catchpoint.
3773 Whether the breakpoint is marked to be disabled or deleted when hit.
3774 @item Enabled or Disabled
3775 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3776 that are not enabled.
3778 Where the breakpoint is in your program, as a memory address. For a
3779 pending breakpoint whose address is not yet known, this field will
3780 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3781 library that has the symbol or line referred by breakpoint is loaded.
3782 See below for details. A breakpoint with several locations will
3783 have @samp{<MULTIPLE>} in this field---see below for details.
3785 Where the breakpoint is in the source for your program, as a file and
3786 line number. For a pending breakpoint, the original string passed to
3787 the breakpoint command will be listed as it cannot be resolved until
3788 the appropriate shared library is loaded in the future.
3792 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3793 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3794 @value{GDBN} on the host's side. If it is ``target'', then the condition
3795 is evaluated by the target. The @code{info break} command shows
3796 the condition on the line following the affected breakpoint, together with
3797 its condition evaluation mode in between parentheses.
3799 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3800 allowed to have a condition specified for it. The condition is not parsed for
3801 validity until a shared library is loaded that allows the pending
3802 breakpoint to resolve to a valid location.
3805 @code{info break} with a breakpoint
3806 number @var{n} as argument lists only that breakpoint. The
3807 convenience variable @code{$_} and the default examining-address for
3808 the @code{x} command are set to the address of the last breakpoint
3809 listed (@pxref{Memory, ,Examining Memory}).
3812 @code{info break} displays a count of the number of times the breakpoint
3813 has been hit. This is especially useful in conjunction with the
3814 @code{ignore} command. You can ignore a large number of breakpoint
3815 hits, look at the breakpoint info to see how many times the breakpoint
3816 was hit, and then run again, ignoring one less than that number. This
3817 will get you quickly to the last hit of that breakpoint.
3820 For a breakpoints with an enable count (xref) greater than 1,
3821 @code{info break} also displays that count.
3825 @value{GDBN} allows you to set any number of breakpoints at the same place in
3826 your program. There is nothing silly or meaningless about this. When
3827 the breakpoints are conditional, this is even useful
3828 (@pxref{Conditions, ,Break Conditions}).
3830 @cindex multiple locations, breakpoints
3831 @cindex breakpoints, multiple locations
3832 It is possible that a breakpoint corresponds to several locations
3833 in your program. Examples of this situation are:
3837 Multiple functions in the program may have the same name.
3840 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3841 instances of the function body, used in different cases.
3844 For a C@t{++} template function, a given line in the function can
3845 correspond to any number of instantiations.
3848 For an inlined function, a given source line can correspond to
3849 several places where that function is inlined.
3852 In all those cases, @value{GDBN} will insert a breakpoint at all
3853 the relevant locations.
3855 A breakpoint with multiple locations is displayed in the breakpoint
3856 table using several rows---one header row, followed by one row for
3857 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3858 address column. The rows for individual locations contain the actual
3859 addresses for locations, and show the functions to which those
3860 locations belong. The number column for a location is of the form
3861 @var{breakpoint-number}.@var{location-number}.
3866 Num Type Disp Enb Address What
3867 1 breakpoint keep y <MULTIPLE>
3869 breakpoint already hit 1 time
3870 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3871 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3874 Each location can be individually enabled or disabled by passing
3875 @var{breakpoint-number}.@var{location-number} as argument to the
3876 @code{enable} and @code{disable} commands. Note that you cannot
3877 delete the individual locations from the list, you can only delete the
3878 entire list of locations that belong to their parent breakpoint (with
3879 the @kbd{delete @var{num}} command, where @var{num} is the number of
3880 the parent breakpoint, 1 in the above example). Disabling or enabling
3881 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3882 that belong to that breakpoint.
3884 @cindex pending breakpoints
3885 It's quite common to have a breakpoint inside a shared library.
3886 Shared libraries can be loaded and unloaded explicitly,
3887 and possibly repeatedly, as the program is executed. To support
3888 this use case, @value{GDBN} updates breakpoint locations whenever
3889 any shared library is loaded or unloaded. Typically, you would
3890 set a breakpoint in a shared library at the beginning of your
3891 debugging session, when the library is not loaded, and when the
3892 symbols from the library are not available. When you try to set
3893 breakpoint, @value{GDBN} will ask you if you want to set
3894 a so called @dfn{pending breakpoint}---breakpoint whose address
3895 is not yet resolved.
3897 After the program is run, whenever a new shared library is loaded,
3898 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3899 shared library contains the symbol or line referred to by some
3900 pending breakpoint, that breakpoint is resolved and becomes an
3901 ordinary breakpoint. When a library is unloaded, all breakpoints
3902 that refer to its symbols or source lines become pending again.
3904 This logic works for breakpoints with multiple locations, too. For
3905 example, if you have a breakpoint in a C@t{++} template function, and
3906 a newly loaded shared library has an instantiation of that template,
3907 a new location is added to the list of locations for the breakpoint.
3909 Except for having unresolved address, pending breakpoints do not
3910 differ from regular breakpoints. You can set conditions or commands,
3911 enable and disable them and perform other breakpoint operations.
3913 @value{GDBN} provides some additional commands for controlling what
3914 happens when the @samp{break} command cannot resolve breakpoint
3915 address specification to an address:
3917 @kindex set breakpoint pending
3918 @kindex show breakpoint pending
3920 @item set breakpoint pending auto
3921 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3922 location, it queries you whether a pending breakpoint should be created.
3924 @item set breakpoint pending on
3925 This indicates that an unrecognized breakpoint location should automatically
3926 result in a pending breakpoint being created.
3928 @item set breakpoint pending off
3929 This indicates that pending breakpoints are not to be created. Any
3930 unrecognized breakpoint location results in an error. This setting does
3931 not affect any pending breakpoints previously created.
3933 @item show breakpoint pending
3934 Show the current behavior setting for creating pending breakpoints.
3937 The settings above only affect the @code{break} command and its
3938 variants. Once breakpoint is set, it will be automatically updated
3939 as shared libraries are loaded and unloaded.
3941 @cindex automatic hardware breakpoints
3942 For some targets, @value{GDBN} can automatically decide if hardware or
3943 software breakpoints should be used, depending on whether the
3944 breakpoint address is read-only or read-write. This applies to
3945 breakpoints set with the @code{break} command as well as to internal
3946 breakpoints set by commands like @code{next} and @code{finish}. For
3947 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3950 You can control this automatic behaviour with the following commands::
3952 @kindex set breakpoint auto-hw
3953 @kindex show breakpoint auto-hw
3955 @item set breakpoint auto-hw on
3956 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3957 will try to use the target memory map to decide if software or hardware
3958 breakpoint must be used.
3960 @item set breakpoint auto-hw off
3961 This indicates @value{GDBN} should not automatically select breakpoint
3962 type. If the target provides a memory map, @value{GDBN} will warn when
3963 trying to set software breakpoint at a read-only address.
3966 @value{GDBN} normally implements breakpoints by replacing the program code
3967 at the breakpoint address with a special instruction, which, when
3968 executed, given control to the debugger. By default, the program
3969 code is so modified only when the program is resumed. As soon as
3970 the program stops, @value{GDBN} restores the original instructions. This
3971 behaviour guards against leaving breakpoints inserted in the
3972 target should gdb abrubptly disconnect. However, with slow remote
3973 targets, inserting and removing breakpoint can reduce the performance.
3974 This behavior can be controlled with the following commands::
3976 @kindex set breakpoint always-inserted
3977 @kindex show breakpoint always-inserted
3979 @item set breakpoint always-inserted off
3980 All breakpoints, including newly added by the user, are inserted in
3981 the target only when the target is resumed. All breakpoints are
3982 removed from the target when it stops. This is the default mode.
3984 @item set breakpoint always-inserted on
3985 Causes all breakpoints to be inserted in the target at all times. If
3986 the user adds a new breakpoint, or changes an existing breakpoint, the
3987 breakpoints in the target are updated immediately. A breakpoint is
3988 removed from the target only when breakpoint itself is deleted.
3991 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3992 when a breakpoint breaks. If the condition is true, then the process being
3993 debugged stops, otherwise the process is resumed.
3995 If the target supports evaluating conditions on its end, @value{GDBN} may
3996 download the breakpoint, together with its conditions, to it.
3998 This feature can be controlled via the following commands:
4000 @kindex set breakpoint condition-evaluation
4001 @kindex show breakpoint condition-evaluation
4003 @item set breakpoint condition-evaluation host
4004 This option commands @value{GDBN} to evaluate the breakpoint
4005 conditions on the host's side. Unconditional breakpoints are sent to
4006 the target which in turn receives the triggers and reports them back to GDB
4007 for condition evaluation. This is the standard evaluation mode.
4009 @item set breakpoint condition-evaluation target
4010 This option commands @value{GDBN} to download breakpoint conditions
4011 to the target at the moment of their insertion. The target
4012 is responsible for evaluating the conditional expression and reporting
4013 breakpoint stop events back to @value{GDBN} whenever the condition
4014 is true. Due to limitations of target-side evaluation, some conditions
4015 cannot be evaluated there, e.g., conditions that depend on local data
4016 that is only known to the host. Examples include
4017 conditional expressions involving convenience variables, complex types
4018 that cannot be handled by the agent expression parser and expressions
4019 that are too long to be sent over to the target, specially when the
4020 target is a remote system. In these cases, the conditions will be
4021 evaluated by @value{GDBN}.
4023 @item set breakpoint condition-evaluation auto
4024 This is the default mode. If the target supports evaluating breakpoint
4025 conditions on its end, @value{GDBN} will download breakpoint conditions to
4026 the target (limitations mentioned previously apply). If the target does
4027 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4028 to evaluating all these conditions on the host's side.
4032 @cindex negative breakpoint numbers
4033 @cindex internal @value{GDBN} breakpoints
4034 @value{GDBN} itself sometimes sets breakpoints in your program for
4035 special purposes, such as proper handling of @code{longjmp} (in C
4036 programs). These internal breakpoints are assigned negative numbers,
4037 starting with @code{-1}; @samp{info breakpoints} does not display them.
4038 You can see these breakpoints with the @value{GDBN} maintenance command
4039 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4042 @node Set Watchpoints
4043 @subsection Setting Watchpoints
4045 @cindex setting watchpoints
4046 You can use a watchpoint to stop execution whenever the value of an
4047 expression changes, without having to predict a particular place where
4048 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4049 The expression may be as simple as the value of a single variable, or
4050 as complex as many variables combined by operators. Examples include:
4054 A reference to the value of a single variable.
4057 An address cast to an appropriate data type. For example,
4058 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4059 address (assuming an @code{int} occupies 4 bytes).
4062 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4063 expression can use any operators valid in the program's native
4064 language (@pxref{Languages}).
4067 You can set a watchpoint on an expression even if the expression can
4068 not be evaluated yet. For instance, you can set a watchpoint on
4069 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4070 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4071 the expression produces a valid value. If the expression becomes
4072 valid in some other way than changing a variable (e.g.@: if the memory
4073 pointed to by @samp{*global_ptr} becomes readable as the result of a
4074 @code{malloc} call), @value{GDBN} may not stop until the next time
4075 the expression changes.
4077 @cindex software watchpoints
4078 @cindex hardware watchpoints
4079 Depending on your system, watchpoints may be implemented in software or
4080 hardware. @value{GDBN} does software watchpointing by single-stepping your
4081 program and testing the variable's value each time, which is hundreds of
4082 times slower than normal execution. (But this may still be worth it, to
4083 catch errors where you have no clue what part of your program is the
4086 On some systems, such as most PowerPC or x86-based targets,
4087 @value{GDBN} includes support for hardware watchpoints, which do not
4088 slow down the running of your program.
4092 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4093 Set a watchpoint for an expression. @value{GDBN} will break when the
4094 expression @var{expr} is written into by the program and its value
4095 changes. The simplest (and the most popular) use of this command is
4096 to watch the value of a single variable:
4099 (@value{GDBP}) watch foo
4102 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4103 argument, @value{GDBN} breaks only when the thread identified by
4104 @var{thread-id} changes the value of @var{expr}. If any other threads
4105 change the value of @var{expr}, @value{GDBN} will not break. Note
4106 that watchpoints restricted to a single thread in this way only work
4107 with Hardware Watchpoints.
4109 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4110 (see below). The @code{-location} argument tells @value{GDBN} to
4111 instead watch the memory referred to by @var{expr}. In this case,
4112 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4113 and watch the memory at that address. The type of the result is used
4114 to determine the size of the watched memory. If the expression's
4115 result does not have an address, then @value{GDBN} will print an
4118 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4119 of masked watchpoints, if the current architecture supports this
4120 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4121 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4122 to an address to watch. The mask specifies that some bits of an address
4123 (the bits which are reset in the mask) should be ignored when matching
4124 the address accessed by the inferior against the watchpoint address.
4125 Thus, a masked watchpoint watches many addresses simultaneously---those
4126 addresses whose unmasked bits are identical to the unmasked bits in the
4127 watchpoint address. The @code{mask} argument implies @code{-location}.
4131 (@value{GDBP}) watch foo mask 0xffff00ff
4132 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4136 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4137 Set a watchpoint that will break when the value of @var{expr} is read
4141 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4142 Set a watchpoint that will break when @var{expr} is either read from
4143 or written into by the program.
4145 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4146 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4147 This command prints a list of watchpoints, using the same format as
4148 @code{info break} (@pxref{Set Breaks}).
4151 If you watch for a change in a numerically entered address you need to
4152 dereference it, as the address itself is just a constant number which will
4153 never change. @value{GDBN} refuses to create a watchpoint that watches
4154 a never-changing value:
4157 (@value{GDBP}) watch 0x600850
4158 Cannot watch constant value 0x600850.
4159 (@value{GDBP}) watch *(int *) 0x600850
4160 Watchpoint 1: *(int *) 6293584
4163 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4164 watchpoints execute very quickly, and the debugger reports a change in
4165 value at the exact instruction where the change occurs. If @value{GDBN}
4166 cannot set a hardware watchpoint, it sets a software watchpoint, which
4167 executes more slowly and reports the change in value at the next
4168 @emph{statement}, not the instruction, after the change occurs.
4170 @cindex use only software watchpoints
4171 You can force @value{GDBN} to use only software watchpoints with the
4172 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4173 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4174 the underlying system supports them. (Note that hardware-assisted
4175 watchpoints that were set @emph{before} setting
4176 @code{can-use-hw-watchpoints} to zero will still use the hardware
4177 mechanism of watching expression values.)
4180 @item set can-use-hw-watchpoints
4181 @kindex set can-use-hw-watchpoints
4182 Set whether or not to use hardware watchpoints.
4184 @item show can-use-hw-watchpoints
4185 @kindex show can-use-hw-watchpoints
4186 Show the current mode of using hardware watchpoints.
4189 For remote targets, you can restrict the number of hardware
4190 watchpoints @value{GDBN} will use, see @ref{set remote
4191 hardware-breakpoint-limit}.
4193 When you issue the @code{watch} command, @value{GDBN} reports
4196 Hardware watchpoint @var{num}: @var{expr}
4200 if it was able to set a hardware watchpoint.
4202 Currently, the @code{awatch} and @code{rwatch} commands can only set
4203 hardware watchpoints, because accesses to data that don't change the
4204 value of the watched expression cannot be detected without examining
4205 every instruction as it is being executed, and @value{GDBN} does not do
4206 that currently. If @value{GDBN} finds that it is unable to set a
4207 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4208 will print a message like this:
4211 Expression cannot be implemented with read/access watchpoint.
4214 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4215 data type of the watched expression is wider than what a hardware
4216 watchpoint on the target machine can handle. For example, some systems
4217 can only watch regions that are up to 4 bytes wide; on such systems you
4218 cannot set hardware watchpoints for an expression that yields a
4219 double-precision floating-point number (which is typically 8 bytes
4220 wide). As a work-around, it might be possible to break the large region
4221 into a series of smaller ones and watch them with separate watchpoints.
4223 If you set too many hardware watchpoints, @value{GDBN} might be unable
4224 to insert all of them when you resume the execution of your program.
4225 Since the precise number of active watchpoints is unknown until such
4226 time as the program is about to be resumed, @value{GDBN} might not be
4227 able to warn you about this when you set the watchpoints, and the
4228 warning will be printed only when the program is resumed:
4231 Hardware watchpoint @var{num}: Could not insert watchpoint
4235 If this happens, delete or disable some of the watchpoints.
4237 Watching complex expressions that reference many variables can also
4238 exhaust the resources available for hardware-assisted watchpoints.
4239 That's because @value{GDBN} needs to watch every variable in the
4240 expression with separately allocated resources.
4242 If you call a function interactively using @code{print} or @code{call},
4243 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4244 kind of breakpoint or the call completes.
4246 @value{GDBN} automatically deletes watchpoints that watch local
4247 (automatic) variables, or expressions that involve such variables, when
4248 they go out of scope, that is, when the execution leaves the block in
4249 which these variables were defined. In particular, when the program
4250 being debugged terminates, @emph{all} local variables go out of scope,
4251 and so only watchpoints that watch global variables remain set. If you
4252 rerun the program, you will need to set all such watchpoints again. One
4253 way of doing that would be to set a code breakpoint at the entry to the
4254 @code{main} function and when it breaks, set all the watchpoints.
4256 @cindex watchpoints and threads
4257 @cindex threads and watchpoints
4258 In multi-threaded programs, watchpoints will detect changes to the
4259 watched expression from every thread.
4262 @emph{Warning:} In multi-threaded programs, software watchpoints
4263 have only limited usefulness. If @value{GDBN} creates a software
4264 watchpoint, it can only watch the value of an expression @emph{in a
4265 single thread}. If you are confident that the expression can only
4266 change due to the current thread's activity (and if you are also
4267 confident that no other thread can become current), then you can use
4268 software watchpoints as usual. However, @value{GDBN} may not notice
4269 when a non-current thread's activity changes the expression. (Hardware
4270 watchpoints, in contrast, watch an expression in all threads.)
4273 @xref{set remote hardware-watchpoint-limit}.
4275 @node Set Catchpoints
4276 @subsection Setting Catchpoints
4277 @cindex catchpoints, setting
4278 @cindex exception handlers
4279 @cindex event handling
4281 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4282 kinds of program events, such as C@t{++} exceptions or the loading of a
4283 shared library. Use the @code{catch} command to set a catchpoint.
4287 @item catch @var{event}
4288 Stop when @var{event} occurs. The @var{event} can be any of the following:
4291 @item throw @r{[}@var{regexp}@r{]}
4292 @itemx rethrow @r{[}@var{regexp}@r{]}
4293 @itemx catch @r{[}@var{regexp}@r{]}
4295 @kindex catch rethrow
4297 @cindex stop on C@t{++} exceptions
4298 The throwing, re-throwing, or catching of a C@t{++} exception.
4300 If @var{regexp} is given, then only exceptions whose type matches the
4301 regular expression will be caught.
4303 @vindex $_exception@r{, convenience variable}
4304 The convenience variable @code{$_exception} is available at an
4305 exception-related catchpoint, on some systems. This holds the
4306 exception being thrown.
4308 There are currently some limitations to C@t{++} exception handling in
4313 The support for these commands is system-dependent. Currently, only
4314 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4318 The regular expression feature and the @code{$_exception} convenience
4319 variable rely on the presence of some SDT probes in @code{libstdc++}.
4320 If these probes are not present, then these features cannot be used.
4321 These probes were first available in the GCC 4.8 release, but whether
4322 or not they are available in your GCC also depends on how it was
4326 The @code{$_exception} convenience variable is only valid at the
4327 instruction at which an exception-related catchpoint is set.
4330 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4331 location in the system library which implements runtime exception
4332 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4333 (@pxref{Selection}) to get to your code.
4336 If you call a function interactively, @value{GDBN} normally returns
4337 control to you when the function has finished executing. If the call
4338 raises an exception, however, the call may bypass the mechanism that
4339 returns control to you and cause your program either to abort or to
4340 simply continue running until it hits a breakpoint, catches a signal
4341 that @value{GDBN} is listening for, or exits. This is the case even if
4342 you set a catchpoint for the exception; catchpoints on exceptions are
4343 disabled within interactive calls. @xref{Calling}, for information on
4344 controlling this with @code{set unwind-on-terminating-exception}.
4347 You cannot raise an exception interactively.
4350 You cannot install an exception handler interactively.
4354 @kindex catch exception
4355 @cindex Ada exception catching
4356 @cindex catch Ada exceptions
4357 An Ada exception being raised. If an exception name is specified
4358 at the end of the command (eg @code{catch exception Program_Error}),
4359 the debugger will stop only when this specific exception is raised.
4360 Otherwise, the debugger stops execution when any Ada exception is raised.
4362 When inserting an exception catchpoint on a user-defined exception whose
4363 name is identical to one of the exceptions defined by the language, the
4364 fully qualified name must be used as the exception name. Otherwise,
4365 @value{GDBN} will assume that it should stop on the pre-defined exception
4366 rather than the user-defined one. For instance, assuming an exception
4367 called @code{Constraint_Error} is defined in package @code{Pck}, then
4368 the command to use to catch such exceptions is @kbd{catch exception
4369 Pck.Constraint_Error}.
4371 @item exception unhandled
4372 @kindex catch exception unhandled
4373 An exception that was raised but is not handled by the program.
4376 @kindex catch assert
4377 A failed Ada assertion.
4381 @cindex break on fork/exec
4382 A call to @code{exec}.
4385 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4386 @kindex catch syscall
4387 @cindex break on a system call.
4388 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4389 syscall is a mechanism for application programs to request a service
4390 from the operating system (OS) or one of the OS system services.
4391 @value{GDBN} can catch some or all of the syscalls issued by the
4392 debuggee, and show the related information for each syscall. If no
4393 argument is specified, calls to and returns from all system calls
4396 @var{name} can be any system call name that is valid for the
4397 underlying OS. Just what syscalls are valid depends on the OS. On
4398 GNU and Unix systems, you can find the full list of valid syscall
4399 names on @file{/usr/include/asm/unistd.h}.
4401 @c For MS-Windows, the syscall names and the corresponding numbers
4402 @c can be found, e.g., on this URL:
4403 @c http://www.metasploit.com/users/opcode/syscalls.html
4404 @c but we don't support Windows syscalls yet.
4406 Normally, @value{GDBN} knows in advance which syscalls are valid for
4407 each OS, so you can use the @value{GDBN} command-line completion
4408 facilities (@pxref{Completion,, command completion}) to list the
4411 You may also specify the system call numerically. A syscall's
4412 number is the value passed to the OS's syscall dispatcher to
4413 identify the requested service. When you specify the syscall by its
4414 name, @value{GDBN} uses its database of syscalls to convert the name
4415 into the corresponding numeric code, but using the number directly
4416 may be useful if @value{GDBN}'s database does not have the complete
4417 list of syscalls on your system (e.g., because @value{GDBN} lags
4418 behind the OS upgrades).
4420 You may specify a group of related syscalls to be caught at once using
4421 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4422 instance, on some platforms @value{GDBN} allows you to catch all
4423 network related syscalls, by passing the argument @code{group:network}
4424 to @code{catch syscall}. Note that not all syscall groups are
4425 available in every system. You can use the command completion
4426 facilities (@pxref{Completion,, command completion}) to list the
4427 syscall groups available on your environment.
4429 The example below illustrates how this command works if you don't provide
4433 (@value{GDBP}) catch syscall
4434 Catchpoint 1 (syscall)
4436 Starting program: /tmp/catch-syscall
4438 Catchpoint 1 (call to syscall 'close'), \
4439 0xffffe424 in __kernel_vsyscall ()
4443 Catchpoint 1 (returned from syscall 'close'), \
4444 0xffffe424 in __kernel_vsyscall ()
4448 Here is an example of catching a system call by name:
4451 (@value{GDBP}) catch syscall chroot
4452 Catchpoint 1 (syscall 'chroot' [61])
4454 Starting program: /tmp/catch-syscall
4456 Catchpoint 1 (call to syscall 'chroot'), \
4457 0xffffe424 in __kernel_vsyscall ()
4461 Catchpoint 1 (returned from syscall 'chroot'), \
4462 0xffffe424 in __kernel_vsyscall ()
4466 An example of specifying a system call numerically. In the case
4467 below, the syscall number has a corresponding entry in the XML
4468 file, so @value{GDBN} finds its name and prints it:
4471 (@value{GDBP}) catch syscall 252
4472 Catchpoint 1 (syscall(s) 'exit_group')
4474 Starting program: /tmp/catch-syscall
4476 Catchpoint 1 (call to syscall 'exit_group'), \
4477 0xffffe424 in __kernel_vsyscall ()
4481 Program exited normally.
4485 Here is an example of catching a syscall group:
4488 (@value{GDBP}) catch syscall group:process
4489 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4490 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4491 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4493 Starting program: /tmp/catch-syscall
4495 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4496 from /lib64/ld-linux-x86-64.so.2
4502 However, there can be situations when there is no corresponding name
4503 in XML file for that syscall number. In this case, @value{GDBN} prints
4504 a warning message saying that it was not able to find the syscall name,
4505 but the catchpoint will be set anyway. See the example below:
4508 (@value{GDBP}) catch syscall 764
4509 warning: The number '764' does not represent a known syscall.
4510 Catchpoint 2 (syscall 764)
4514 If you configure @value{GDBN} using the @samp{--without-expat} option,
4515 it will not be able to display syscall names. Also, if your
4516 architecture does not have an XML file describing its system calls,
4517 you will not be able to see the syscall names. It is important to
4518 notice that these two features are used for accessing the syscall
4519 name database. In either case, you will see a warning like this:
4522 (@value{GDBP}) catch syscall
4523 warning: Could not open "syscalls/i386-linux.xml"
4524 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4525 GDB will not be able to display syscall names.
4526 Catchpoint 1 (syscall)
4530 Of course, the file name will change depending on your architecture and system.
4532 Still using the example above, you can also try to catch a syscall by its
4533 number. In this case, you would see something like:
4536 (@value{GDBP}) catch syscall 252
4537 Catchpoint 1 (syscall(s) 252)
4540 Again, in this case @value{GDBN} would not be able to display syscall's names.
4544 A call to @code{fork}.
4548 A call to @code{vfork}.
4550 @item load @r{[}regexp@r{]}
4551 @itemx unload @r{[}regexp@r{]}
4553 @kindex catch unload
4554 The loading or unloading of a shared library. If @var{regexp} is
4555 given, then the catchpoint will stop only if the regular expression
4556 matches one of the affected libraries.
4558 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4559 @kindex catch signal
4560 The delivery of a signal.
4562 With no arguments, this catchpoint will catch any signal that is not
4563 used internally by @value{GDBN}, specifically, all signals except
4564 @samp{SIGTRAP} and @samp{SIGINT}.
4566 With the argument @samp{all}, all signals, including those used by
4567 @value{GDBN}, will be caught. This argument cannot be used with other
4570 Otherwise, the arguments are a list of signal names as given to
4571 @code{handle} (@pxref{Signals}). Only signals specified in this list
4574 One reason that @code{catch signal} can be more useful than
4575 @code{handle} is that you can attach commands and conditions to the
4578 When a signal is caught by a catchpoint, the signal's @code{stop} and
4579 @code{print} settings, as specified by @code{handle}, are ignored.
4580 However, whether the signal is still delivered to the inferior depends
4581 on the @code{pass} setting; this can be changed in the catchpoint's
4586 @item tcatch @var{event}
4588 Set a catchpoint that is enabled only for one stop. The catchpoint is
4589 automatically deleted after the first time the event is caught.
4593 Use the @code{info break} command to list the current catchpoints.
4597 @subsection Deleting Breakpoints
4599 @cindex clearing breakpoints, watchpoints, catchpoints
4600 @cindex deleting breakpoints, watchpoints, catchpoints
4601 It is often necessary to eliminate a breakpoint, watchpoint, or
4602 catchpoint once it has done its job and you no longer want your program
4603 to stop there. This is called @dfn{deleting} the breakpoint. A
4604 breakpoint that has been deleted no longer exists; it is forgotten.
4606 With the @code{clear} command you can delete breakpoints according to
4607 where they are in your program. With the @code{delete} command you can
4608 delete individual breakpoints, watchpoints, or catchpoints by specifying
4609 their breakpoint numbers.
4611 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4612 automatically ignores breakpoints on the first instruction to be executed
4613 when you continue execution without changing the execution address.
4618 Delete any breakpoints at the next instruction to be executed in the
4619 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4620 the innermost frame is selected, this is a good way to delete a
4621 breakpoint where your program just stopped.
4623 @item clear @var{location}
4624 Delete any breakpoints set at the specified @var{location}.
4625 @xref{Specify Location}, for the various forms of @var{location}; the
4626 most useful ones are listed below:
4629 @item clear @var{function}
4630 @itemx clear @var{filename}:@var{function}
4631 Delete any breakpoints set at entry to the named @var{function}.
4633 @item clear @var{linenum}
4634 @itemx clear @var{filename}:@var{linenum}
4635 Delete any breakpoints set at or within the code of the specified
4636 @var{linenum} of the specified @var{filename}.
4639 @cindex delete breakpoints
4641 @kindex d @r{(@code{delete})}
4642 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4643 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4644 ranges specified as arguments. If no argument is specified, delete all
4645 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4646 confirm off}). You can abbreviate this command as @code{d}.
4650 @subsection Disabling Breakpoints
4652 @cindex enable/disable a breakpoint
4653 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4654 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4655 it had been deleted, but remembers the information on the breakpoint so
4656 that you can @dfn{enable} it again later.
4658 You disable and enable breakpoints, watchpoints, and catchpoints with
4659 the @code{enable} and @code{disable} commands, optionally specifying
4660 one or more breakpoint numbers as arguments. Use @code{info break} to
4661 print a list of all breakpoints, watchpoints, and catchpoints if you
4662 do not know which numbers to use.
4664 Disabling and enabling a breakpoint that has multiple locations
4665 affects all of its locations.
4667 A breakpoint, watchpoint, or catchpoint can have any of several
4668 different states of enablement:
4672 Enabled. The breakpoint stops your program. A breakpoint set
4673 with the @code{break} command starts out in this state.
4675 Disabled. The breakpoint has no effect on your program.
4677 Enabled once. The breakpoint stops your program, but then becomes
4680 Enabled for a count. The breakpoint stops your program for the next
4681 N times, then becomes disabled.
4683 Enabled for deletion. The breakpoint stops your program, but
4684 immediately after it does so it is deleted permanently. A breakpoint
4685 set with the @code{tbreak} command starts out in this state.
4688 You can use the following commands to enable or disable breakpoints,
4689 watchpoints, and catchpoints:
4693 @kindex dis @r{(@code{disable})}
4694 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4695 Disable the specified breakpoints---or all breakpoints, if none are
4696 listed. A disabled breakpoint has no effect but is not forgotten. All
4697 options such as ignore-counts, conditions and commands are remembered in
4698 case the breakpoint is enabled again later. You may abbreviate
4699 @code{disable} as @code{dis}.
4702 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4703 Enable the specified breakpoints (or all defined breakpoints). They
4704 become effective once again in stopping your program.
4706 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4707 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4708 of these breakpoints immediately after stopping your program.
4710 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4711 Enable the specified breakpoints temporarily. @value{GDBN} records
4712 @var{count} with each of the specified breakpoints, and decrements a
4713 breakpoint's count when it is hit. When any count reaches 0,
4714 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4715 count (@pxref{Conditions, ,Break Conditions}), that will be
4716 decremented to 0 before @var{count} is affected.
4718 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4719 Enable the specified breakpoints to work once, then die. @value{GDBN}
4720 deletes any of these breakpoints as soon as your program stops there.
4721 Breakpoints set by the @code{tbreak} command start out in this state.
4724 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4725 @c confusing: tbreak is also initially enabled.
4726 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4727 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4728 subsequently, they become disabled or enabled only when you use one of
4729 the commands above. (The command @code{until} can set and delete a
4730 breakpoint of its own, but it does not change the state of your other
4731 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4735 @subsection Break Conditions
4736 @cindex conditional breakpoints
4737 @cindex breakpoint conditions
4739 @c FIXME what is scope of break condition expr? Context where wanted?
4740 @c in particular for a watchpoint?
4741 The simplest sort of breakpoint breaks every time your program reaches a
4742 specified place. You can also specify a @dfn{condition} for a
4743 breakpoint. A condition is just a Boolean expression in your
4744 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4745 a condition evaluates the expression each time your program reaches it,
4746 and your program stops only if the condition is @emph{true}.
4748 This is the converse of using assertions for program validation; in that
4749 situation, you want to stop when the assertion is violated---that is,
4750 when the condition is false. In C, if you want to test an assertion expressed
4751 by the condition @var{assert}, you should set the condition
4752 @samp{! @var{assert}} on the appropriate breakpoint.
4754 Conditions are also accepted for watchpoints; you may not need them,
4755 since a watchpoint is inspecting the value of an expression anyhow---but
4756 it might be simpler, say, to just set a watchpoint on a variable name,
4757 and specify a condition that tests whether the new value is an interesting
4760 Break conditions can have side effects, and may even call functions in
4761 your program. This can be useful, for example, to activate functions
4762 that log program progress, or to use your own print functions to
4763 format special data structures. The effects are completely predictable
4764 unless there is another enabled breakpoint at the same address. (In
4765 that case, @value{GDBN} might see the other breakpoint first and stop your
4766 program without checking the condition of this one.) Note that
4767 breakpoint commands are usually more convenient and flexible than break
4769 purpose of performing side effects when a breakpoint is reached
4770 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4772 Breakpoint conditions can also be evaluated on the target's side if
4773 the target supports it. Instead of evaluating the conditions locally,
4774 @value{GDBN} encodes the expression into an agent expression
4775 (@pxref{Agent Expressions}) suitable for execution on the target,
4776 independently of @value{GDBN}. Global variables become raw memory
4777 locations, locals become stack accesses, and so forth.
4779 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4780 when its condition evaluates to true. This mechanism may provide faster
4781 response times depending on the performance characteristics of the target
4782 since it does not need to keep @value{GDBN} informed about
4783 every breakpoint trigger, even those with false conditions.
4785 Break conditions can be specified when a breakpoint is set, by using
4786 @samp{if} in the arguments to the @code{break} command. @xref{Set
4787 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4788 with the @code{condition} command.
4790 You can also use the @code{if} keyword with the @code{watch} command.
4791 The @code{catch} command does not recognize the @code{if} keyword;
4792 @code{condition} is the only way to impose a further condition on a
4797 @item condition @var{bnum} @var{expression}
4798 Specify @var{expression} as the break condition for breakpoint,
4799 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4800 breakpoint @var{bnum} stops your program only if the value of
4801 @var{expression} is true (nonzero, in C). When you use
4802 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4803 syntactic correctness, and to determine whether symbols in it have
4804 referents in the context of your breakpoint. If @var{expression} uses
4805 symbols not referenced in the context of the breakpoint, @value{GDBN}
4806 prints an error message:
4809 No symbol "foo" in current context.
4814 not actually evaluate @var{expression} at the time the @code{condition}
4815 command (or a command that sets a breakpoint with a condition, like
4816 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4818 @item condition @var{bnum}
4819 Remove the condition from breakpoint number @var{bnum}. It becomes
4820 an ordinary unconditional breakpoint.
4823 @cindex ignore count (of breakpoint)
4824 A special case of a breakpoint condition is to stop only when the
4825 breakpoint has been reached a certain number of times. This is so
4826 useful that there is a special way to do it, using the @dfn{ignore
4827 count} of the breakpoint. Every breakpoint has an ignore count, which
4828 is an integer. Most of the time, the ignore count is zero, and
4829 therefore has no effect. But if your program reaches a breakpoint whose
4830 ignore count is positive, then instead of stopping, it just decrements
4831 the ignore count by one and continues. As a result, if the ignore count
4832 value is @var{n}, the breakpoint does not stop the next @var{n} times
4833 your program reaches it.
4837 @item ignore @var{bnum} @var{count}
4838 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4839 The next @var{count} times the breakpoint is reached, your program's
4840 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4843 To make the breakpoint stop the next time it is reached, specify
4846 When you use @code{continue} to resume execution of your program from a
4847 breakpoint, you can specify an ignore count directly as an argument to
4848 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4849 Stepping,,Continuing and Stepping}.
4851 If a breakpoint has a positive ignore count and a condition, the
4852 condition is not checked. Once the ignore count reaches zero,
4853 @value{GDBN} resumes checking the condition.
4855 You could achieve the effect of the ignore count with a condition such
4856 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4857 is decremented each time. @xref{Convenience Vars, ,Convenience
4861 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4864 @node Break Commands
4865 @subsection Breakpoint Command Lists
4867 @cindex breakpoint commands
4868 You can give any breakpoint (or watchpoint or catchpoint) a series of
4869 commands to execute when your program stops due to that breakpoint. For
4870 example, you might want to print the values of certain expressions, or
4871 enable other breakpoints.
4875 @kindex end@r{ (breakpoint commands)}
4876 @item commands @r{[}@var{range}@dots{}@r{]}
4877 @itemx @dots{} @var{command-list} @dots{}
4879 Specify a list of commands for the given breakpoints. The commands
4880 themselves appear on the following lines. Type a line containing just
4881 @code{end} to terminate the commands.
4883 To remove all commands from a breakpoint, type @code{commands} and
4884 follow it immediately with @code{end}; that is, give no commands.
4886 With no argument, @code{commands} refers to the last breakpoint,
4887 watchpoint, or catchpoint set (not to the breakpoint most recently
4888 encountered). If the most recent breakpoints were set with a single
4889 command, then the @code{commands} will apply to all the breakpoints
4890 set by that command. This applies to breakpoints set by
4891 @code{rbreak}, and also applies when a single @code{break} command
4892 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4896 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4897 disabled within a @var{command-list}.
4899 You can use breakpoint commands to start your program up again. Simply
4900 use the @code{continue} command, or @code{step}, or any other command
4901 that resumes execution.
4903 Any other commands in the command list, after a command that resumes
4904 execution, are ignored. This is because any time you resume execution
4905 (even with a simple @code{next} or @code{step}), you may encounter
4906 another breakpoint---which could have its own command list, leading to
4907 ambiguities about which list to execute.
4910 If the first command you specify in a command list is @code{silent}, the
4911 usual message about stopping at a breakpoint is not printed. This may
4912 be desirable for breakpoints that are to print a specific message and
4913 then continue. If none of the remaining commands print anything, you
4914 see no sign that the breakpoint was reached. @code{silent} is
4915 meaningful only at the beginning of a breakpoint command list.
4917 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4918 print precisely controlled output, and are often useful in silent
4919 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4921 For example, here is how you could use breakpoint commands to print the
4922 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4928 printf "x is %d\n",x
4933 One application for breakpoint commands is to compensate for one bug so
4934 you can test for another. Put a breakpoint just after the erroneous line
4935 of code, give it a condition to detect the case in which something
4936 erroneous has been done, and give it commands to assign correct values
4937 to any variables that need them. End with the @code{continue} command
4938 so that your program does not stop, and start with the @code{silent}
4939 command so that no output is produced. Here is an example:
4950 @node Dynamic Printf
4951 @subsection Dynamic Printf
4953 @cindex dynamic printf
4955 The dynamic printf command @code{dprintf} combines a breakpoint with
4956 formatted printing of your program's data to give you the effect of
4957 inserting @code{printf} calls into your program on-the-fly, without
4958 having to recompile it.
4960 In its most basic form, the output goes to the GDB console. However,
4961 you can set the variable @code{dprintf-style} for alternate handling.
4962 For instance, you can ask to format the output by calling your
4963 program's @code{printf} function. This has the advantage that the
4964 characters go to the program's output device, so they can recorded in
4965 redirects to files and so forth.
4967 If you are doing remote debugging with a stub or agent, you can also
4968 ask to have the printf handled by the remote agent. In addition to
4969 ensuring that the output goes to the remote program's device along
4970 with any other output the program might produce, you can also ask that
4971 the dprintf remain active even after disconnecting from the remote
4972 target. Using the stub/agent is also more efficient, as it can do
4973 everything without needing to communicate with @value{GDBN}.
4977 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4978 Whenever execution reaches @var{location}, print the values of one or
4979 more @var{expressions} under the control of the string @var{template}.
4980 To print several values, separate them with commas.
4982 @item set dprintf-style @var{style}
4983 Set the dprintf output to be handled in one of several different
4984 styles enumerated below. A change of style affects all existing
4985 dynamic printfs immediately. (If you need individual control over the
4986 print commands, simply define normal breakpoints with
4987 explicitly-supplied command lists.)
4990 @kindex dprintf-style gdb
4991 Handle the output using the @value{GDBN} @code{printf} command.
4994 @kindex dprintf-style call
4995 Handle the output by calling a function in your program (normally
4999 @kindex dprintf-style agent
5000 Have the remote debugging agent (such as @code{gdbserver}) handle
5001 the output itself. This style is only available for agents that
5002 support running commands on the target.
5004 @item set dprintf-function @var{function}
5005 Set the function to call if the dprintf style is @code{call}. By
5006 default its value is @code{printf}. You may set it to any expression.
5007 that @value{GDBN} can evaluate to a function, as per the @code{call}
5010 @item set dprintf-channel @var{channel}
5011 Set a ``channel'' for dprintf. If set to a non-empty value,
5012 @value{GDBN} will evaluate it as an expression and pass the result as
5013 a first argument to the @code{dprintf-function}, in the manner of
5014 @code{fprintf} and similar functions. Otherwise, the dprintf format
5015 string will be the first argument, in the manner of @code{printf}.
5017 As an example, if you wanted @code{dprintf} output to go to a logfile
5018 that is a standard I/O stream assigned to the variable @code{mylog},
5019 you could do the following:
5022 (gdb) set dprintf-style call
5023 (gdb) set dprintf-function fprintf
5024 (gdb) set dprintf-channel mylog
5025 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5026 Dprintf 1 at 0x123456: file main.c, line 25.
5028 1 dprintf keep y 0x00123456 in main at main.c:25
5029 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5034 Note that the @code{info break} displays the dynamic printf commands
5035 as normal breakpoint commands; you can thus easily see the effect of
5036 the variable settings.
5038 @item set disconnected-dprintf on
5039 @itemx set disconnected-dprintf off
5040 @kindex set disconnected-dprintf
5041 Choose whether @code{dprintf} commands should continue to run if
5042 @value{GDBN} has disconnected from the target. This only applies
5043 if the @code{dprintf-style} is @code{agent}.
5045 @item show disconnected-dprintf off
5046 @kindex show disconnected-dprintf
5047 Show the current choice for disconnected @code{dprintf}.
5051 @value{GDBN} does not check the validity of function and channel,
5052 relying on you to supply values that are meaningful for the contexts
5053 in which they are being used. For instance, the function and channel
5054 may be the values of local variables, but if that is the case, then
5055 all enabled dynamic prints must be at locations within the scope of
5056 those locals. If evaluation fails, @value{GDBN} will report an error.
5058 @node Save Breakpoints
5059 @subsection How to save breakpoints to a file
5061 To save breakpoint definitions to a file use the @w{@code{save
5062 breakpoints}} command.
5065 @kindex save breakpoints
5066 @cindex save breakpoints to a file for future sessions
5067 @item save breakpoints [@var{filename}]
5068 This command saves all current breakpoint definitions together with
5069 their commands and ignore counts, into a file @file{@var{filename}}
5070 suitable for use in a later debugging session. This includes all
5071 types of breakpoints (breakpoints, watchpoints, catchpoints,
5072 tracepoints). To read the saved breakpoint definitions, use the
5073 @code{source} command (@pxref{Command Files}). Note that watchpoints
5074 with expressions involving local variables may fail to be recreated
5075 because it may not be possible to access the context where the
5076 watchpoint is valid anymore. Because the saved breakpoint definitions
5077 are simply a sequence of @value{GDBN} commands that recreate the
5078 breakpoints, you can edit the file in your favorite editing program,
5079 and remove the breakpoint definitions you're not interested in, or
5080 that can no longer be recreated.
5083 @node Static Probe Points
5084 @subsection Static Probe Points
5086 @cindex static probe point, SystemTap
5087 @cindex static probe point, DTrace
5088 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5089 for Statically Defined Tracing, and the probes are designed to have a tiny
5090 runtime code and data footprint, and no dynamic relocations.
5092 Currently, the following types of probes are supported on
5093 ELF-compatible systems:
5097 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5098 @acronym{SDT} probes@footnote{See
5099 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5100 for more information on how to add @code{SystemTap} @acronym{SDT}
5101 probes in your applications.}. @code{SystemTap} probes are usable
5102 from assembly, C and C@t{++} languages@footnote{See
5103 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5104 for a good reference on how the @acronym{SDT} probes are implemented.}.
5106 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5107 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5111 @cindex semaphores on static probe points
5112 Some @code{SystemTap} probes have an associated semaphore variable;
5113 for instance, this happens automatically if you defined your probe
5114 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5115 @value{GDBN} will automatically enable it when you specify a
5116 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5117 breakpoint at a probe's location by some other method (e.g.,
5118 @code{break file:line}), then @value{GDBN} will not automatically set
5119 the semaphore. @code{DTrace} probes do not support semaphores.
5121 You can examine the available static static probes using @code{info
5122 probes}, with optional arguments:
5126 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5127 If given, @var{type} is either @code{stap} for listing
5128 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5129 probes. If omitted all probes are listed regardless of their types.
5131 If given, @var{provider} is a regular expression used to match against provider
5132 names when selecting which probes to list. If omitted, probes by all
5133 probes from all providers are listed.
5135 If given, @var{name} is a regular expression to match against probe names
5136 when selecting which probes to list. If omitted, probe names are not
5137 considered when deciding whether to display them.
5139 If given, @var{objfile} is a regular expression used to select which
5140 object files (executable or shared libraries) to examine. If not
5141 given, all object files are considered.
5143 @item info probes all
5144 List the available static probes, from all types.
5147 @cindex enabling and disabling probes
5148 Some probe points can be enabled and/or disabled. The effect of
5149 enabling or disabling a probe depends on the type of probe being
5150 handled. Some @code{DTrace} probes can be enabled or
5151 disabled, but @code{SystemTap} probes cannot be disabled.
5153 You can enable (or disable) one or more probes using the following
5154 commands, with optional arguments:
5157 @kindex enable probes
5158 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5159 If given, @var{provider} is a regular expression used to match against
5160 provider names when selecting which probes to enable. If omitted,
5161 all probes from all providers are enabled.
5163 If given, @var{name} is a regular expression to match against probe
5164 names when selecting which probes to enable. If omitted, probe names
5165 are not considered when deciding whether to enable them.
5167 If given, @var{objfile} is a regular expression used to select which
5168 object files (executable or shared libraries) to examine. If not
5169 given, all object files are considered.
5171 @kindex disable probes
5172 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5173 See the @code{enable probes} command above for a description of the
5174 optional arguments accepted by this command.
5177 @vindex $_probe_arg@r{, convenience variable}
5178 A probe may specify up to twelve arguments. These are available at the
5179 point at which the probe is defined---that is, when the current PC is
5180 at the probe's location. The arguments are available using the
5181 convenience variables (@pxref{Convenience Vars})
5182 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5183 probes each probe argument is an integer of the appropriate size;
5184 types are not preserved. In @code{DTrace} probes types are preserved
5185 provided that they are recognized as such by @value{GDBN}; otherwise
5186 the value of the probe argument will be a long integer. The
5187 convenience variable @code{$_probe_argc} holds the number of arguments
5188 at the current probe point.
5190 These variables are always available, but attempts to access them at
5191 any location other than a probe point will cause @value{GDBN} to give
5195 @c @ifclear BARETARGET
5196 @node Error in Breakpoints
5197 @subsection ``Cannot insert breakpoints''
5199 If you request too many active hardware-assisted breakpoints and
5200 watchpoints, you will see this error message:
5202 @c FIXME: the precise wording of this message may change; the relevant
5203 @c source change is not committed yet (Sep 3, 1999).
5205 Stopped; cannot insert breakpoints.
5206 You may have requested too many hardware breakpoints and watchpoints.
5210 This message is printed when you attempt to resume the program, since
5211 only then @value{GDBN} knows exactly how many hardware breakpoints and
5212 watchpoints it needs to insert.
5214 When this message is printed, you need to disable or remove some of the
5215 hardware-assisted breakpoints and watchpoints, and then continue.
5217 @node Breakpoint-related Warnings
5218 @subsection ``Breakpoint address adjusted...''
5219 @cindex breakpoint address adjusted
5221 Some processor architectures place constraints on the addresses at
5222 which breakpoints may be placed. For architectures thus constrained,
5223 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5224 with the constraints dictated by the architecture.
5226 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5227 a VLIW architecture in which a number of RISC-like instructions may be
5228 bundled together for parallel execution. The FR-V architecture
5229 constrains the location of a breakpoint instruction within such a
5230 bundle to the instruction with the lowest address. @value{GDBN}
5231 honors this constraint by adjusting a breakpoint's address to the
5232 first in the bundle.
5234 It is not uncommon for optimized code to have bundles which contain
5235 instructions from different source statements, thus it may happen that
5236 a breakpoint's address will be adjusted from one source statement to
5237 another. Since this adjustment may significantly alter @value{GDBN}'s
5238 breakpoint related behavior from what the user expects, a warning is
5239 printed when the breakpoint is first set and also when the breakpoint
5242 A warning like the one below is printed when setting a breakpoint
5243 that's been subject to address adjustment:
5246 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5249 Such warnings are printed both for user settable and @value{GDBN}'s
5250 internal breakpoints. If you see one of these warnings, you should
5251 verify that a breakpoint set at the adjusted address will have the
5252 desired affect. If not, the breakpoint in question may be removed and
5253 other breakpoints may be set which will have the desired behavior.
5254 E.g., it may be sufficient to place the breakpoint at a later
5255 instruction. A conditional breakpoint may also be useful in some
5256 cases to prevent the breakpoint from triggering too often.
5258 @value{GDBN} will also issue a warning when stopping at one of these
5259 adjusted breakpoints:
5262 warning: Breakpoint 1 address previously adjusted from 0x00010414
5266 When this warning is encountered, it may be too late to take remedial
5267 action except in cases where the breakpoint is hit earlier or more
5268 frequently than expected.
5270 @node Continuing and Stepping
5271 @section Continuing and Stepping
5275 @cindex resuming execution
5276 @dfn{Continuing} means resuming program execution until your program
5277 completes normally. In contrast, @dfn{stepping} means executing just
5278 one more ``step'' of your program, where ``step'' may mean either one
5279 line of source code, or one machine instruction (depending on what
5280 particular command you use). Either when continuing or when stepping,
5281 your program may stop even sooner, due to a breakpoint or a signal. (If
5282 it stops due to a signal, you may want to use @code{handle}, or use
5283 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5284 or you may step into the signal's handler (@pxref{stepping and signal
5289 @kindex c @r{(@code{continue})}
5290 @kindex fg @r{(resume foreground execution)}
5291 @item continue @r{[}@var{ignore-count}@r{]}
5292 @itemx c @r{[}@var{ignore-count}@r{]}
5293 @itemx fg @r{[}@var{ignore-count}@r{]}
5294 Resume program execution, at the address where your program last stopped;
5295 any breakpoints set at that address are bypassed. The optional argument
5296 @var{ignore-count} allows you to specify a further number of times to
5297 ignore a breakpoint at this location; its effect is like that of
5298 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5300 The argument @var{ignore-count} is meaningful only when your program
5301 stopped due to a breakpoint. At other times, the argument to
5302 @code{continue} is ignored.
5304 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5305 debugged program is deemed to be the foreground program) are provided
5306 purely for convenience, and have exactly the same behavior as
5310 To resume execution at a different place, you can use @code{return}
5311 (@pxref{Returning, ,Returning from a Function}) to go back to the
5312 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5313 Different Address}) to go to an arbitrary location in your program.
5315 A typical technique for using stepping is to set a breakpoint
5316 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5317 beginning of the function or the section of your program where a problem
5318 is believed to lie, run your program until it stops at that breakpoint,
5319 and then step through the suspect area, examining the variables that are
5320 interesting, until you see the problem happen.
5324 @kindex s @r{(@code{step})}
5326 Continue running your program until control reaches a different source
5327 line, then stop it and return control to @value{GDBN}. This command is
5328 abbreviated @code{s}.
5331 @c "without debugging information" is imprecise; actually "without line
5332 @c numbers in the debugging information". (gcc -g1 has debugging info but
5333 @c not line numbers). But it seems complex to try to make that
5334 @c distinction here.
5335 @emph{Warning:} If you use the @code{step} command while control is
5336 within a function that was compiled without debugging information,
5337 execution proceeds until control reaches a function that does have
5338 debugging information. Likewise, it will not step into a function which
5339 is compiled without debugging information. To step through functions
5340 without debugging information, use the @code{stepi} command, described
5344 The @code{step} command only stops at the first instruction of a source
5345 line. This prevents the multiple stops that could otherwise occur in
5346 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5347 to stop if a function that has debugging information is called within
5348 the line. In other words, @code{step} @emph{steps inside} any functions
5349 called within the line.
5351 Also, the @code{step} command only enters a function if there is line
5352 number information for the function. Otherwise it acts like the
5353 @code{next} command. This avoids problems when using @code{cc -gl}
5354 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5355 was any debugging information about the routine.
5357 @item step @var{count}
5358 Continue running as in @code{step}, but do so @var{count} times. If a
5359 breakpoint is reached, or a signal not related to stepping occurs before
5360 @var{count} steps, stepping stops right away.
5363 @kindex n @r{(@code{next})}
5364 @item next @r{[}@var{count}@r{]}
5365 Continue to the next source line in the current (innermost) stack frame.
5366 This is similar to @code{step}, but function calls that appear within
5367 the line of code are executed without stopping. Execution stops when
5368 control reaches a different line of code at the original stack level
5369 that was executing when you gave the @code{next} command. This command
5370 is abbreviated @code{n}.
5372 An argument @var{count} is a repeat count, as for @code{step}.
5375 @c FIX ME!! Do we delete this, or is there a way it fits in with
5376 @c the following paragraph? --- Vctoria
5378 @c @code{next} within a function that lacks debugging information acts like
5379 @c @code{step}, but any function calls appearing within the code of the
5380 @c function are executed without stopping.
5382 The @code{next} command only stops at the first instruction of a
5383 source line. This prevents multiple stops that could otherwise occur in
5384 @code{switch} statements, @code{for} loops, etc.
5386 @kindex set step-mode
5388 @cindex functions without line info, and stepping
5389 @cindex stepping into functions with no line info
5390 @itemx set step-mode on
5391 The @code{set step-mode on} command causes the @code{step} command to
5392 stop at the first instruction of a function which contains no debug line
5393 information rather than stepping over it.
5395 This is useful in cases where you may be interested in inspecting the
5396 machine instructions of a function which has no symbolic info and do not
5397 want @value{GDBN} to automatically skip over this function.
5399 @item set step-mode off
5400 Causes the @code{step} command to step over any functions which contains no
5401 debug information. This is the default.
5403 @item show step-mode
5404 Show whether @value{GDBN} will stop in or step over functions without
5405 source line debug information.
5408 @kindex fin @r{(@code{finish})}
5410 Continue running until just after function in the selected stack frame
5411 returns. Print the returned value (if any). This command can be
5412 abbreviated as @code{fin}.
5414 Contrast this with the @code{return} command (@pxref{Returning,
5415 ,Returning from a Function}).
5418 @kindex u @r{(@code{until})}
5419 @cindex run until specified location
5422 Continue running until a source line past the current line, in the
5423 current stack frame, is reached. This command is used to avoid single
5424 stepping through a loop more than once. It is like the @code{next}
5425 command, except that when @code{until} encounters a jump, it
5426 automatically continues execution until the program counter is greater
5427 than the address of the jump.
5429 This means that when you reach the end of a loop after single stepping
5430 though it, @code{until} makes your program continue execution until it
5431 exits the loop. In contrast, a @code{next} command at the end of a loop
5432 simply steps back to the beginning of the loop, which forces you to step
5433 through the next iteration.
5435 @code{until} always stops your program if it attempts to exit the current
5438 @code{until} may produce somewhat counterintuitive results if the order
5439 of machine code does not match the order of the source lines. For
5440 example, in the following excerpt from a debugging session, the @code{f}
5441 (@code{frame}) command shows that execution is stopped at line
5442 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5446 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5448 (@value{GDBP}) until
5449 195 for ( ; argc > 0; NEXTARG) @{
5452 This happened because, for execution efficiency, the compiler had
5453 generated code for the loop closure test at the end, rather than the
5454 start, of the loop---even though the test in a C @code{for}-loop is
5455 written before the body of the loop. The @code{until} command appeared
5456 to step back to the beginning of the loop when it advanced to this
5457 expression; however, it has not really gone to an earlier
5458 statement---not in terms of the actual machine code.
5460 @code{until} with no argument works by means of single
5461 instruction stepping, and hence is slower than @code{until} with an
5464 @item until @var{location}
5465 @itemx u @var{location}
5466 Continue running your program until either the specified @var{location} is
5467 reached, or the current stack frame returns. The location is any of
5468 the forms described in @ref{Specify Location}.
5469 This form of the command uses temporary breakpoints, and
5470 hence is quicker than @code{until} without an argument. The specified
5471 location is actually reached only if it is in the current frame. This
5472 implies that @code{until} can be used to skip over recursive function
5473 invocations. For instance in the code below, if the current location is
5474 line @code{96}, issuing @code{until 99} will execute the program up to
5475 line @code{99} in the same invocation of factorial, i.e., after the inner
5476 invocations have returned.
5479 94 int factorial (int value)
5481 96 if (value > 1) @{
5482 97 value *= factorial (value - 1);
5489 @kindex advance @var{location}
5490 @item advance @var{location}
5491 Continue running the program up to the given @var{location}. An argument is
5492 required, which should be of one of the forms described in
5493 @ref{Specify Location}.
5494 Execution will also stop upon exit from the current stack
5495 frame. This command is similar to @code{until}, but @code{advance} will
5496 not skip over recursive function calls, and the target location doesn't
5497 have to be in the same frame as the current one.
5501 @kindex si @r{(@code{stepi})}
5503 @itemx stepi @var{arg}
5505 Execute one machine instruction, then stop and return to the debugger.
5507 It is often useful to do @samp{display/i $pc} when stepping by machine
5508 instructions. This makes @value{GDBN} automatically display the next
5509 instruction to be executed, each time your program stops. @xref{Auto
5510 Display,, Automatic Display}.
5512 An argument is a repeat count, as in @code{step}.
5516 @kindex ni @r{(@code{nexti})}
5518 @itemx nexti @var{arg}
5520 Execute one machine instruction, but if it is a function call,
5521 proceed until the function returns.
5523 An argument is a repeat count, as in @code{next}.
5527 @anchor{range stepping}
5528 @cindex range stepping
5529 @cindex target-assisted range stepping
5530 By default, and if available, @value{GDBN} makes use of
5531 target-assisted @dfn{range stepping}. In other words, whenever you
5532 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5533 tells the target to step the corresponding range of instruction
5534 addresses instead of issuing multiple single-steps. This speeds up
5535 line stepping, particularly for remote targets. Ideally, there should
5536 be no reason you would want to turn range stepping off. However, it's
5537 possible that a bug in the debug info, a bug in the remote stub (for
5538 remote targets), or even a bug in @value{GDBN} could make line
5539 stepping behave incorrectly when target-assisted range stepping is
5540 enabled. You can use the following command to turn off range stepping
5544 @kindex set range-stepping
5545 @kindex show range-stepping
5546 @item set range-stepping
5547 @itemx show range-stepping
5548 Control whether range stepping is enabled.
5550 If @code{on}, and the target supports it, @value{GDBN} tells the
5551 target to step a range of addresses itself, instead of issuing
5552 multiple single-steps. If @code{off}, @value{GDBN} always issues
5553 single-steps, even if range stepping is supported by the target. The
5554 default is @code{on}.
5558 @node Skipping Over Functions and Files
5559 @section Skipping Over Functions and Files
5560 @cindex skipping over functions and files
5562 The program you are debugging may contain some functions which are
5563 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5564 skip a function, all functions in a file or a particular function in
5565 a particular file when stepping.
5567 For example, consider the following C function:
5578 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5579 are not interested in stepping through @code{boring}. If you run @code{step}
5580 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5581 step over both @code{foo} and @code{boring}!
5583 One solution is to @code{step} into @code{boring} and use the @code{finish}
5584 command to immediately exit it. But this can become tedious if @code{boring}
5585 is called from many places.
5587 A more flexible solution is to execute @kbd{skip boring}. This instructs
5588 @value{GDBN} never to step into @code{boring}. Now when you execute
5589 @code{step} at line 103, you'll step over @code{boring} and directly into
5592 Functions may be skipped by providing either a function name, linespec
5593 (@pxref{Specify Location}), regular expression that matches the function's
5594 name, file name or a @code{glob}-style pattern that matches the file name.
5596 On Posix systems the form of the regular expression is
5597 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5598 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5599 expression is whatever is provided by the @code{regcomp} function of
5600 the underlying system.
5601 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5602 description of @code{glob}-style patterns.
5606 @item skip @r{[}@var{options}@r{]}
5607 The basic form of the @code{skip} command takes zero or more options
5608 that specify what to skip.
5609 The @var{options} argument is any useful combination of the following:
5612 @item -file @var{file}
5613 @itemx -fi @var{file}
5614 Functions in @var{file} will be skipped over when stepping.
5616 @item -gfile @var{file-glob-pattern}
5617 @itemx -gfi @var{file-glob-pattern}
5618 @cindex skipping over files via glob-style patterns
5619 Functions in files matching @var{file-glob-pattern} will be skipped
5623 (gdb) skip -gfi utils/*.c
5626 @item -function @var{linespec}
5627 @itemx -fu @var{linespec}
5628 Functions named by @var{linespec} or the function containing the line
5629 named by @var{linespec} will be skipped over when stepping.
5630 @xref{Specify Location}.
5632 @item -rfunction @var{regexp}
5633 @itemx -rfu @var{regexp}
5634 @cindex skipping over functions via regular expressions
5635 Functions whose name matches @var{regexp} will be skipped over when stepping.
5637 This form is useful for complex function names.
5638 For example, there is generally no need to step into C@t{++} @code{std::string}
5639 constructors or destructors. Plus with C@t{++} templates it can be hard to
5640 write out the full name of the function, and often it doesn't matter what
5641 the template arguments are. Specifying the function to be skipped as a
5642 regular expression makes this easier.
5645 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5648 If you want to skip every templated C@t{++} constructor and destructor
5649 in the @code{std} namespace you can do:
5652 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5656 If no options are specified, the function you're currently debugging
5659 @kindex skip function
5660 @item skip function @r{[}@var{linespec}@r{]}
5661 After running this command, the function named by @var{linespec} or the
5662 function containing the line named by @var{linespec} will be skipped over when
5663 stepping. @xref{Specify Location}.
5665 If you do not specify @var{linespec}, the function you're currently debugging
5668 (If you have a function called @code{file} that you want to skip, use
5669 @kbd{skip function file}.)
5672 @item skip file @r{[}@var{filename}@r{]}
5673 After running this command, any function whose source lives in @var{filename}
5674 will be skipped over when stepping.
5677 (gdb) skip file boring.c
5678 File boring.c will be skipped when stepping.
5681 If you do not specify @var{filename}, functions whose source lives in the file
5682 you're currently debugging will be skipped.
5685 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5686 These are the commands for managing your list of skips:
5690 @item info skip @r{[}@var{range}@r{]}
5691 Print details about the specified skip(s). If @var{range} is not specified,
5692 print a table with details about all functions and files marked for skipping.
5693 @code{info skip} prints the following information about each skip:
5697 A number identifying this skip.
5698 @item Enabled or Disabled
5699 Enabled skips are marked with @samp{y}.
5700 Disabled skips are marked with @samp{n}.
5702 If the file name is a @samp{glob} pattern this is @samp{y}.
5703 Otherwise it is @samp{n}.
5705 The name or @samp{glob} pattern of the file to be skipped.
5706 If no file is specified this is @samp{<none>}.
5708 If the function name is a @samp{regular expression} this is @samp{y}.
5709 Otherwise it is @samp{n}.
5711 The name or regular expression of the function to skip.
5712 If no function is specified this is @samp{<none>}.
5716 @item skip delete @r{[}@var{range}@r{]}
5717 Delete the specified skip(s). If @var{range} is not specified, delete all
5721 @item skip enable @r{[}@var{range}@r{]}
5722 Enable the specified skip(s). If @var{range} is not specified, enable all
5725 @kindex skip disable
5726 @item skip disable @r{[}@var{range}@r{]}
5727 Disable the specified skip(s). If @var{range} is not specified, disable all
5736 A signal is an asynchronous event that can happen in a program. The
5737 operating system defines the possible kinds of signals, and gives each
5738 kind a name and a number. For example, in Unix @code{SIGINT} is the
5739 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5740 @code{SIGSEGV} is the signal a program gets from referencing a place in
5741 memory far away from all the areas in use; @code{SIGALRM} occurs when
5742 the alarm clock timer goes off (which happens only if your program has
5743 requested an alarm).
5745 @cindex fatal signals
5746 Some signals, including @code{SIGALRM}, are a normal part of the
5747 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5748 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5749 program has not specified in advance some other way to handle the signal.
5750 @code{SIGINT} does not indicate an error in your program, but it is normally
5751 fatal so it can carry out the purpose of the interrupt: to kill the program.
5753 @value{GDBN} has the ability to detect any occurrence of a signal in your
5754 program. You can tell @value{GDBN} in advance what to do for each kind of
5757 @cindex handling signals
5758 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5759 @code{SIGALRM} be silently passed to your program
5760 (so as not to interfere with their role in the program's functioning)
5761 but to stop your program immediately whenever an error signal happens.
5762 You can change these settings with the @code{handle} command.
5765 @kindex info signals
5769 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5770 handle each one. You can use this to see the signal numbers of all
5771 the defined types of signals.
5773 @item info signals @var{sig}
5774 Similar, but print information only about the specified signal number.
5776 @code{info handle} is an alias for @code{info signals}.
5778 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5779 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5780 for details about this command.
5783 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5784 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5785 can be the number of a signal or its name (with or without the
5786 @samp{SIG} at the beginning); a list of signal numbers of the form
5787 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5788 known signals. Optional arguments @var{keywords}, described below,
5789 say what change to make.
5793 The keywords allowed by the @code{handle} command can be abbreviated.
5794 Their full names are:
5798 @value{GDBN} should not stop your program when this signal happens. It may
5799 still print a message telling you that the signal has come in.
5802 @value{GDBN} should stop your program when this signal happens. This implies
5803 the @code{print} keyword as well.
5806 @value{GDBN} should print a message when this signal happens.
5809 @value{GDBN} should not mention the occurrence of the signal at all. This
5810 implies the @code{nostop} keyword as well.
5814 @value{GDBN} should allow your program to see this signal; your program
5815 can handle the signal, or else it may terminate if the signal is fatal
5816 and not handled. @code{pass} and @code{noignore} are synonyms.
5820 @value{GDBN} should not allow your program to see this signal.
5821 @code{nopass} and @code{ignore} are synonyms.
5825 When a signal stops your program, the signal is not visible to the
5827 continue. Your program sees the signal then, if @code{pass} is in
5828 effect for the signal in question @emph{at that time}. In other words,
5829 after @value{GDBN} reports a signal, you can use the @code{handle}
5830 command with @code{pass} or @code{nopass} to control whether your
5831 program sees that signal when you continue.
5833 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5834 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5835 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5838 You can also use the @code{signal} command to prevent your program from
5839 seeing a signal, or cause it to see a signal it normally would not see,
5840 or to give it any signal at any time. For example, if your program stopped
5841 due to some sort of memory reference error, you might store correct
5842 values into the erroneous variables and continue, hoping to see more
5843 execution; but your program would probably terminate immediately as
5844 a result of the fatal signal once it saw the signal. To prevent this,
5845 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5848 @cindex stepping and signal handlers
5849 @anchor{stepping and signal handlers}
5851 @value{GDBN} optimizes for stepping the mainline code. If a signal
5852 that has @code{handle nostop} and @code{handle pass} set arrives while
5853 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5854 in progress, @value{GDBN} lets the signal handler run and then resumes
5855 stepping the mainline code once the signal handler returns. In other
5856 words, @value{GDBN} steps over the signal handler. This prevents
5857 signals that you've specified as not interesting (with @code{handle
5858 nostop}) from changing the focus of debugging unexpectedly. Note that
5859 the signal handler itself may still hit a breakpoint, stop for another
5860 signal that has @code{handle stop} in effect, or for any other event
5861 that normally results in stopping the stepping command sooner. Also
5862 note that @value{GDBN} still informs you that the program received a
5863 signal if @code{handle print} is set.
5865 @anchor{stepping into signal handlers}
5867 If you set @code{handle pass} for a signal, and your program sets up a
5868 handler for it, then issuing a stepping command, such as @code{step}
5869 or @code{stepi}, when your program is stopped due to the signal will
5870 step @emph{into} the signal handler (if the target supports that).
5872 Likewise, if you use the @code{queue-signal} command to queue a signal
5873 to be delivered to the current thread when execution of the thread
5874 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5875 stepping command will step into the signal handler.
5877 Here's an example, using @code{stepi} to step to the first instruction
5878 of @code{SIGUSR1}'s handler:
5881 (@value{GDBP}) handle SIGUSR1
5882 Signal Stop Print Pass to program Description
5883 SIGUSR1 Yes Yes Yes User defined signal 1
5887 Program received signal SIGUSR1, User defined signal 1.
5888 main () sigusr1.c:28
5891 sigusr1_handler () at sigusr1.c:9
5895 The same, but using @code{queue-signal} instead of waiting for the
5896 program to receive the signal first:
5901 (@value{GDBP}) queue-signal SIGUSR1
5903 sigusr1_handler () at sigusr1.c:9
5908 @cindex extra signal information
5909 @anchor{extra signal information}
5911 On some targets, @value{GDBN} can inspect extra signal information
5912 associated with the intercepted signal, before it is actually
5913 delivered to the program being debugged. This information is exported
5914 by the convenience variable @code{$_siginfo}, and consists of data
5915 that is passed by the kernel to the signal handler at the time of the
5916 receipt of a signal. The data type of the information itself is
5917 target dependent. You can see the data type using the @code{ptype
5918 $_siginfo} command. On Unix systems, it typically corresponds to the
5919 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5922 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5923 referenced address that raised a segmentation fault.
5927 (@value{GDBP}) continue
5928 Program received signal SIGSEGV, Segmentation fault.
5929 0x0000000000400766 in main ()
5931 (@value{GDBP}) ptype $_siginfo
5938 struct @{...@} _kill;
5939 struct @{...@} _timer;
5941 struct @{...@} _sigchld;
5942 struct @{...@} _sigfault;
5943 struct @{...@} _sigpoll;
5946 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5950 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5951 $1 = (void *) 0x7ffff7ff7000
5955 Depending on target support, @code{$_siginfo} may also be writable.
5957 @cindex Intel MPX boundary violations
5958 @cindex boundary violations, Intel MPX
5959 On some targets, a @code{SIGSEGV} can be caused by a boundary
5960 violation, i.e., accessing an address outside of the allowed range.
5961 In those cases @value{GDBN} may displays additional information,
5962 depending on how @value{GDBN} has been told to handle the signal.
5963 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5964 kind: "Upper" or "Lower", the memory address accessed and the
5965 bounds, while with @code{handle nostop SIGSEGV} no additional
5966 information is displayed.
5968 The usual output of a segfault is:
5970 Program received signal SIGSEGV, Segmentation fault
5971 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5972 68 value = *(p + len);
5975 While a bound violation is presented as:
5977 Program received signal SIGSEGV, Segmentation fault
5978 Upper bound violation while accessing address 0x7fffffffc3b3
5979 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5980 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5981 68 value = *(p + len);
5985 @section Stopping and Starting Multi-thread Programs
5987 @cindex stopped threads
5988 @cindex threads, stopped
5990 @cindex continuing threads
5991 @cindex threads, continuing
5993 @value{GDBN} supports debugging programs with multiple threads
5994 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5995 are two modes of controlling execution of your program within the
5996 debugger. In the default mode, referred to as @dfn{all-stop mode},
5997 when any thread in your program stops (for example, at a breakpoint
5998 or while being stepped), all other threads in the program are also stopped by
5999 @value{GDBN}. On some targets, @value{GDBN} also supports
6000 @dfn{non-stop mode}, in which other threads can continue to run freely while
6001 you examine the stopped thread in the debugger.
6004 * All-Stop Mode:: All threads stop when GDB takes control
6005 * Non-Stop Mode:: Other threads continue to execute
6006 * Background Execution:: Running your program asynchronously
6007 * Thread-Specific Breakpoints:: Controlling breakpoints
6008 * Interrupted System Calls:: GDB may interfere with system calls
6009 * Observer Mode:: GDB does not alter program behavior
6013 @subsection All-Stop Mode
6015 @cindex all-stop mode
6017 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6018 @emph{all} threads of execution stop, not just the current thread. This
6019 allows you to examine the overall state of the program, including
6020 switching between threads, without worrying that things may change
6023 Conversely, whenever you restart the program, @emph{all} threads start
6024 executing. @emph{This is true even when single-stepping} with commands
6025 like @code{step} or @code{next}.
6027 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6028 Since thread scheduling is up to your debugging target's operating
6029 system (not controlled by @value{GDBN}), other threads may
6030 execute more than one statement while the current thread completes a
6031 single step. Moreover, in general other threads stop in the middle of a
6032 statement, rather than at a clean statement boundary, when the program
6035 You might even find your program stopped in another thread after
6036 continuing or even single-stepping. This happens whenever some other
6037 thread runs into a breakpoint, a signal, or an exception before the
6038 first thread completes whatever you requested.
6040 @cindex automatic thread selection
6041 @cindex switching threads automatically
6042 @cindex threads, automatic switching
6043 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6044 signal, it automatically selects the thread where that breakpoint or
6045 signal happened. @value{GDBN} alerts you to the context switch with a
6046 message such as @samp{[Switching to Thread @var{n}]} to identify the
6049 On some OSes, you can modify @value{GDBN}'s default behavior by
6050 locking the OS scheduler to allow only a single thread to run.
6053 @item set scheduler-locking @var{mode}
6054 @cindex scheduler locking mode
6055 @cindex lock scheduler
6056 Set the scheduler locking mode. It applies to normal execution,
6057 record mode, and replay mode. If it is @code{off}, then there is no
6058 locking and any thread may run at any time. If @code{on}, then only
6059 the current thread may run when the inferior is resumed. The
6060 @code{step} mode optimizes for single-stepping; it prevents other
6061 threads from preempting the current thread while you are stepping, so
6062 that the focus of debugging does not change unexpectedly. Other
6063 threads never get a chance to run when you step, and they are
6064 completely free to run when you use commands like @samp{continue},
6065 @samp{until}, or @samp{finish}. However, unless another thread hits a
6066 breakpoint during its timeslice, @value{GDBN} does not change the
6067 current thread away from the thread that you are debugging. The
6068 @code{replay} mode behaves like @code{off} in record mode and like
6069 @code{on} in replay mode.
6071 @item show scheduler-locking
6072 Display the current scheduler locking mode.
6075 @cindex resume threads of multiple processes simultaneously
6076 By default, when you issue one of the execution commands such as
6077 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6078 threads of the current inferior to run. For example, if @value{GDBN}
6079 is attached to two inferiors, each with two threads, the
6080 @code{continue} command resumes only the two threads of the current
6081 inferior. This is useful, for example, when you debug a program that
6082 forks and you want to hold the parent stopped (so that, for instance,
6083 it doesn't run to exit), while you debug the child. In other
6084 situations, you may not be interested in inspecting the current state
6085 of any of the processes @value{GDBN} is attached to, and you may want
6086 to resume them all until some breakpoint is hit. In the latter case,
6087 you can instruct @value{GDBN} to allow all threads of all the
6088 inferiors to run with the @w{@code{set schedule-multiple}} command.
6091 @kindex set schedule-multiple
6092 @item set schedule-multiple
6093 Set the mode for allowing threads of multiple processes to be resumed
6094 when an execution command is issued. When @code{on}, all threads of
6095 all processes are allowed to run. When @code{off}, only the threads
6096 of the current process are resumed. The default is @code{off}. The
6097 @code{scheduler-locking} mode takes precedence when set to @code{on},
6098 or while you are stepping and set to @code{step}.
6100 @item show schedule-multiple
6101 Display the current mode for resuming the execution of threads of
6106 @subsection Non-Stop Mode
6108 @cindex non-stop mode
6110 @c This section is really only a place-holder, and needs to be expanded
6111 @c with more details.
6113 For some multi-threaded targets, @value{GDBN} supports an optional
6114 mode of operation in which you can examine stopped program threads in
6115 the debugger while other threads continue to execute freely. This
6116 minimizes intrusion when debugging live systems, such as programs
6117 where some threads have real-time constraints or must continue to
6118 respond to external events. This is referred to as @dfn{non-stop} mode.
6120 In non-stop mode, when a thread stops to report a debugging event,
6121 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6122 threads as well, in contrast to the all-stop mode behavior. Additionally,
6123 execution commands such as @code{continue} and @code{step} apply by default
6124 only to the current thread in non-stop mode, rather than all threads as
6125 in all-stop mode. This allows you to control threads explicitly in
6126 ways that are not possible in all-stop mode --- for example, stepping
6127 one thread while allowing others to run freely, stepping
6128 one thread while holding all others stopped, or stepping several threads
6129 independently and simultaneously.
6131 To enter non-stop mode, use this sequence of commands before you run
6132 or attach to your program:
6135 # If using the CLI, pagination breaks non-stop.
6138 # Finally, turn it on!
6142 You can use these commands to manipulate the non-stop mode setting:
6145 @kindex set non-stop
6146 @item set non-stop on
6147 Enable selection of non-stop mode.
6148 @item set non-stop off
6149 Disable selection of non-stop mode.
6150 @kindex show non-stop
6152 Show the current non-stop enablement setting.
6155 Note these commands only reflect whether non-stop mode is enabled,
6156 not whether the currently-executing program is being run in non-stop mode.
6157 In particular, the @code{set non-stop} preference is only consulted when
6158 @value{GDBN} starts or connects to the target program, and it is generally
6159 not possible to switch modes once debugging has started. Furthermore,
6160 since not all targets support non-stop mode, even when you have enabled
6161 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6164 In non-stop mode, all execution commands apply only to the current thread
6165 by default. That is, @code{continue} only continues one thread.
6166 To continue all threads, issue @code{continue -a} or @code{c -a}.
6168 You can use @value{GDBN}'s background execution commands
6169 (@pxref{Background Execution}) to run some threads in the background
6170 while you continue to examine or step others from @value{GDBN}.
6171 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6172 always executed asynchronously in non-stop mode.
6174 Suspending execution is done with the @code{interrupt} command when
6175 running in the background, or @kbd{Ctrl-c} during foreground execution.
6176 In all-stop mode, this stops the whole process;
6177 but in non-stop mode the interrupt applies only to the current thread.
6178 To stop the whole program, use @code{interrupt -a}.
6180 Other execution commands do not currently support the @code{-a} option.
6182 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6183 that thread current, as it does in all-stop mode. This is because the
6184 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6185 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6186 changed to a different thread just as you entered a command to operate on the
6187 previously current thread.
6189 @node Background Execution
6190 @subsection Background Execution
6192 @cindex foreground execution
6193 @cindex background execution
6194 @cindex asynchronous execution
6195 @cindex execution, foreground, background and asynchronous
6197 @value{GDBN}'s execution commands have two variants: the normal
6198 foreground (synchronous) behavior, and a background
6199 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6200 the program to report that some thread has stopped before prompting for
6201 another command. In background execution, @value{GDBN} immediately gives
6202 a command prompt so that you can issue other commands while your program runs.
6204 If the target doesn't support async mode, @value{GDBN} issues an error
6205 message if you attempt to use the background execution commands.
6207 To specify background execution, add a @code{&} to the command. For example,
6208 the background form of the @code{continue} command is @code{continue&}, or
6209 just @code{c&}. The execution commands that accept background execution
6215 @xref{Starting, , Starting your Program}.
6219 @xref{Attach, , Debugging an Already-running Process}.
6223 @xref{Continuing and Stepping, step}.
6227 @xref{Continuing and Stepping, stepi}.
6231 @xref{Continuing and Stepping, next}.
6235 @xref{Continuing and Stepping, nexti}.
6239 @xref{Continuing and Stepping, continue}.
6243 @xref{Continuing and Stepping, finish}.
6247 @xref{Continuing and Stepping, until}.
6251 Background execution is especially useful in conjunction with non-stop
6252 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6253 However, you can also use these commands in the normal all-stop mode with
6254 the restriction that you cannot issue another execution command until the
6255 previous one finishes. Examples of commands that are valid in all-stop
6256 mode while the program is running include @code{help} and @code{info break}.
6258 You can interrupt your program while it is running in the background by
6259 using the @code{interrupt} command.
6266 Suspend execution of the running program. In all-stop mode,
6267 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6268 only the current thread. To stop the whole program in non-stop mode,
6269 use @code{interrupt -a}.
6272 @node Thread-Specific Breakpoints
6273 @subsection Thread-Specific Breakpoints
6275 When your program has multiple threads (@pxref{Threads,, Debugging
6276 Programs with Multiple Threads}), you can choose whether to set
6277 breakpoints on all threads, or on a particular thread.
6280 @cindex breakpoints and threads
6281 @cindex thread breakpoints
6282 @kindex break @dots{} thread @var{thread-id}
6283 @item break @var{location} thread @var{thread-id}
6284 @itemx break @var{location} thread @var{thread-id} if @dots{}
6285 @var{location} specifies source lines; there are several ways of
6286 writing them (@pxref{Specify Location}), but the effect is always to
6287 specify some source line.
6289 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6290 to specify that you only want @value{GDBN} to stop the program when a
6291 particular thread reaches this breakpoint. The @var{thread-id} specifier
6292 is one of the thread identifiers assigned by @value{GDBN}, shown
6293 in the first column of the @samp{info threads} display.
6295 If you do not specify @samp{thread @var{thread-id}} when you set a
6296 breakpoint, the breakpoint applies to @emph{all} threads of your
6299 You can use the @code{thread} qualifier on conditional breakpoints as
6300 well; in this case, place @samp{thread @var{thread-id}} before or
6301 after the breakpoint condition, like this:
6304 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6309 Thread-specific breakpoints are automatically deleted when
6310 @value{GDBN} detects the corresponding thread is no longer in the
6311 thread list. For example:
6315 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6318 There are several ways for a thread to disappear, such as a regular
6319 thread exit, but also when you detach from the process with the
6320 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6321 Process}), or if @value{GDBN} loses the remote connection
6322 (@pxref{Remote Debugging}), etc. Note that with some targets,
6323 @value{GDBN} is only able to detect a thread has exited when the user
6324 explictly asks for the thread list with the @code{info threads}
6327 @node Interrupted System Calls
6328 @subsection Interrupted System Calls
6330 @cindex thread breakpoints and system calls
6331 @cindex system calls and thread breakpoints
6332 @cindex premature return from system calls
6333 There is an unfortunate side effect when using @value{GDBN} to debug
6334 multi-threaded programs. If one thread stops for a
6335 breakpoint, or for some other reason, and another thread is blocked in a
6336 system call, then the system call may return prematurely. This is a
6337 consequence of the interaction between multiple threads and the signals
6338 that @value{GDBN} uses to implement breakpoints and other events that
6341 To handle this problem, your program should check the return value of
6342 each system call and react appropriately. This is good programming
6345 For example, do not write code like this:
6351 The call to @code{sleep} will return early if a different thread stops
6352 at a breakpoint or for some other reason.
6354 Instead, write this:
6359 unslept = sleep (unslept);
6362 A system call is allowed to return early, so the system is still
6363 conforming to its specification. But @value{GDBN} does cause your
6364 multi-threaded program to behave differently than it would without
6367 Also, @value{GDBN} uses internal breakpoints in the thread library to
6368 monitor certain events such as thread creation and thread destruction.
6369 When such an event happens, a system call in another thread may return
6370 prematurely, even though your program does not appear to stop.
6373 @subsection Observer Mode
6375 If you want to build on non-stop mode and observe program behavior
6376 without any chance of disruption by @value{GDBN}, you can set
6377 variables to disable all of the debugger's attempts to modify state,
6378 whether by writing memory, inserting breakpoints, etc. These operate
6379 at a low level, intercepting operations from all commands.
6381 When all of these are set to @code{off}, then @value{GDBN} is said to
6382 be @dfn{observer mode}. As a convenience, the variable
6383 @code{observer} can be set to disable these, plus enable non-stop
6386 Note that @value{GDBN} will not prevent you from making nonsensical
6387 combinations of these settings. For instance, if you have enabled
6388 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6389 then breakpoints that work by writing trap instructions into the code
6390 stream will still not be able to be placed.
6395 @item set observer on
6396 @itemx set observer off
6397 When set to @code{on}, this disables all the permission variables
6398 below (except for @code{insert-fast-tracepoints}), plus enables
6399 non-stop debugging. Setting this to @code{off} switches back to
6400 normal debugging, though remaining in non-stop mode.
6403 Show whether observer mode is on or off.
6405 @kindex may-write-registers
6406 @item set may-write-registers on
6407 @itemx set may-write-registers off
6408 This controls whether @value{GDBN} will attempt to alter the values of
6409 registers, such as with assignment expressions in @code{print}, or the
6410 @code{jump} command. It defaults to @code{on}.
6412 @item show may-write-registers
6413 Show the current permission to write registers.
6415 @kindex may-write-memory
6416 @item set may-write-memory on
6417 @itemx set may-write-memory off
6418 This controls whether @value{GDBN} will attempt to alter the contents
6419 of memory, such as with assignment expressions in @code{print}. It
6420 defaults to @code{on}.
6422 @item show may-write-memory
6423 Show the current permission to write memory.
6425 @kindex may-insert-breakpoints
6426 @item set may-insert-breakpoints on
6427 @itemx set may-insert-breakpoints off
6428 This controls whether @value{GDBN} will attempt to insert breakpoints.
6429 This affects all breakpoints, including internal breakpoints defined
6430 by @value{GDBN}. It defaults to @code{on}.
6432 @item show may-insert-breakpoints
6433 Show the current permission to insert breakpoints.
6435 @kindex may-insert-tracepoints
6436 @item set may-insert-tracepoints on
6437 @itemx set may-insert-tracepoints off
6438 This controls whether @value{GDBN} will attempt to insert (regular)
6439 tracepoints at the beginning of a tracing experiment. It affects only
6440 non-fast tracepoints, fast tracepoints being under the control of
6441 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6443 @item show may-insert-tracepoints
6444 Show the current permission to insert tracepoints.
6446 @kindex may-insert-fast-tracepoints
6447 @item set may-insert-fast-tracepoints on
6448 @itemx set may-insert-fast-tracepoints off
6449 This controls whether @value{GDBN} will attempt to insert fast
6450 tracepoints at the beginning of a tracing experiment. It affects only
6451 fast tracepoints, regular (non-fast) tracepoints being under the
6452 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6454 @item show may-insert-fast-tracepoints
6455 Show the current permission to insert fast tracepoints.
6457 @kindex may-interrupt
6458 @item set may-interrupt on
6459 @itemx set may-interrupt off
6460 This controls whether @value{GDBN} will attempt to interrupt or stop
6461 program execution. When this variable is @code{off}, the
6462 @code{interrupt} command will have no effect, nor will
6463 @kbd{Ctrl-c}. It defaults to @code{on}.
6465 @item show may-interrupt
6466 Show the current permission to interrupt or stop the program.
6470 @node Reverse Execution
6471 @chapter Running programs backward
6472 @cindex reverse execution
6473 @cindex running programs backward
6475 When you are debugging a program, it is not unusual to realize that
6476 you have gone too far, and some event of interest has already happened.
6477 If the target environment supports it, @value{GDBN} can allow you to
6478 ``rewind'' the program by running it backward.
6480 A target environment that supports reverse execution should be able
6481 to ``undo'' the changes in machine state that have taken place as the
6482 program was executing normally. Variables, registers etc.@: should
6483 revert to their previous values. Obviously this requires a great
6484 deal of sophistication on the part of the target environment; not
6485 all target environments can support reverse execution.
6487 When a program is executed in reverse, the instructions that
6488 have most recently been executed are ``un-executed'', in reverse
6489 order. The program counter runs backward, following the previous
6490 thread of execution in reverse. As each instruction is ``un-executed'',
6491 the values of memory and/or registers that were changed by that
6492 instruction are reverted to their previous states. After executing
6493 a piece of source code in reverse, all side effects of that code
6494 should be ``undone'', and all variables should be returned to their
6495 prior values@footnote{
6496 Note that some side effects are easier to undo than others. For instance,
6497 memory and registers are relatively easy, but device I/O is hard. Some
6498 targets may be able undo things like device I/O, and some may not.
6500 The contract between @value{GDBN} and the reverse executing target
6501 requires only that the target do something reasonable when
6502 @value{GDBN} tells it to execute backwards, and then report the
6503 results back to @value{GDBN}. Whatever the target reports back to
6504 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6505 assumes that the memory and registers that the target reports are in a
6506 consistant state, but @value{GDBN} accepts whatever it is given.
6509 If you are debugging in a target environment that supports
6510 reverse execution, @value{GDBN} provides the following commands.
6513 @kindex reverse-continue
6514 @kindex rc @r{(@code{reverse-continue})}
6515 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6516 @itemx rc @r{[}@var{ignore-count}@r{]}
6517 Beginning at the point where your program last stopped, start executing
6518 in reverse. Reverse execution will stop for breakpoints and synchronous
6519 exceptions (signals), just like normal execution. Behavior of
6520 asynchronous signals depends on the target environment.
6522 @kindex reverse-step
6523 @kindex rs @r{(@code{step})}
6524 @item reverse-step @r{[}@var{count}@r{]}
6525 Run the program backward until control reaches the start of a
6526 different source line; then stop it, and return control to @value{GDBN}.
6528 Like the @code{step} command, @code{reverse-step} will only stop
6529 at the beginning of a source line. It ``un-executes'' the previously
6530 executed source line. If the previous source line included calls to
6531 debuggable functions, @code{reverse-step} will step (backward) into
6532 the called function, stopping at the beginning of the @emph{last}
6533 statement in the called function (typically a return statement).
6535 Also, as with the @code{step} command, if non-debuggable functions are
6536 called, @code{reverse-step} will run thru them backward without stopping.
6538 @kindex reverse-stepi
6539 @kindex rsi @r{(@code{reverse-stepi})}
6540 @item reverse-stepi @r{[}@var{count}@r{]}
6541 Reverse-execute one machine instruction. Note that the instruction
6542 to be reverse-executed is @emph{not} the one pointed to by the program
6543 counter, but the instruction executed prior to that one. For instance,
6544 if the last instruction was a jump, @code{reverse-stepi} will take you
6545 back from the destination of the jump to the jump instruction itself.
6547 @kindex reverse-next
6548 @kindex rn @r{(@code{reverse-next})}
6549 @item reverse-next @r{[}@var{count}@r{]}
6550 Run backward to the beginning of the previous line executed in
6551 the current (innermost) stack frame. If the line contains function
6552 calls, they will be ``un-executed'' without stopping. Starting from
6553 the first line of a function, @code{reverse-next} will take you back
6554 to the caller of that function, @emph{before} the function was called,
6555 just as the normal @code{next} command would take you from the last
6556 line of a function back to its return to its caller
6557 @footnote{Unless the code is too heavily optimized.}.
6559 @kindex reverse-nexti
6560 @kindex rni @r{(@code{reverse-nexti})}
6561 @item reverse-nexti @r{[}@var{count}@r{]}
6562 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6563 in reverse, except that called functions are ``un-executed'' atomically.
6564 That is, if the previously executed instruction was a return from
6565 another function, @code{reverse-nexti} will continue to execute
6566 in reverse until the call to that function (from the current stack
6569 @kindex reverse-finish
6570 @item reverse-finish
6571 Just as the @code{finish} command takes you to the point where the
6572 current function returns, @code{reverse-finish} takes you to the point
6573 where it was called. Instead of ending up at the end of the current
6574 function invocation, you end up at the beginning.
6576 @kindex set exec-direction
6577 @item set exec-direction
6578 Set the direction of target execution.
6579 @item set exec-direction reverse
6580 @cindex execute forward or backward in time
6581 @value{GDBN} will perform all execution commands in reverse, until the
6582 exec-direction mode is changed to ``forward''. Affected commands include
6583 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6584 command cannot be used in reverse mode.
6585 @item set exec-direction forward
6586 @value{GDBN} will perform all execution commands in the normal fashion.
6587 This is the default.
6591 @node Process Record and Replay
6592 @chapter Recording Inferior's Execution and Replaying It
6593 @cindex process record and replay
6594 @cindex recording inferior's execution and replaying it
6596 On some platforms, @value{GDBN} provides a special @dfn{process record
6597 and replay} target that can record a log of the process execution, and
6598 replay it later with both forward and reverse execution commands.
6601 When this target is in use, if the execution log includes the record
6602 for the next instruction, @value{GDBN} will debug in @dfn{replay
6603 mode}. In the replay mode, the inferior does not really execute code
6604 instructions. Instead, all the events that normally happen during
6605 code execution are taken from the execution log. While code is not
6606 really executed in replay mode, the values of registers (including the
6607 program counter register) and the memory of the inferior are still
6608 changed as they normally would. Their contents are taken from the
6612 If the record for the next instruction is not in the execution log,
6613 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6614 inferior executes normally, and @value{GDBN} records the execution log
6617 The process record and replay target supports reverse execution
6618 (@pxref{Reverse Execution}), even if the platform on which the
6619 inferior runs does not. However, the reverse execution is limited in
6620 this case by the range of the instructions recorded in the execution
6621 log. In other words, reverse execution on platforms that don't
6622 support it directly can only be done in the replay mode.
6624 When debugging in the reverse direction, @value{GDBN} will work in
6625 replay mode as long as the execution log includes the record for the
6626 previous instruction; otherwise, it will work in record mode, if the
6627 platform supports reverse execution, or stop if not.
6629 For architecture environments that support process record and replay,
6630 @value{GDBN} provides the following commands:
6633 @kindex target record
6634 @kindex target record-full
6635 @kindex target record-btrace
6638 @kindex record btrace
6639 @kindex record btrace bts
6640 @kindex record btrace pt
6646 @kindex rec btrace bts
6647 @kindex rec btrace pt
6650 @item record @var{method}
6651 This command starts the process record and replay target. The
6652 recording method can be specified as parameter. Without a parameter
6653 the command uses the @code{full} recording method. The following
6654 recording methods are available:
6658 Full record/replay recording using @value{GDBN}'s software record and
6659 replay implementation. This method allows replaying and reverse
6662 @item btrace @var{format}
6663 Hardware-supported instruction recording. This method does not record
6664 data. Further, the data is collected in a ring buffer so old data will
6665 be overwritten when the buffer is full. It allows limited reverse
6666 execution. Variables and registers are not available during reverse
6667 execution. In remote debugging, recording continues on disconnect.
6668 Recorded data can be inspected after reconnecting. The recording may
6669 be stopped using @code{record stop}.
6671 The recording format can be specified as parameter. Without a parameter
6672 the command chooses the recording format. The following recording
6673 formats are available:
6677 @cindex branch trace store
6678 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6679 this format, the processor stores a from/to record for each executed
6680 branch in the btrace ring buffer.
6683 @cindex Intel Processor Trace
6684 Use the @dfn{Intel Processor Trace} recording format. In this
6685 format, the processor stores the execution trace in a compressed form
6686 that is afterwards decoded by @value{GDBN}.
6688 The trace can be recorded with very low overhead. The compressed
6689 trace format also allows small trace buffers to already contain a big
6690 number of instructions compared to @acronym{BTS}.
6692 Decoding the recorded execution trace, on the other hand, is more
6693 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6694 increased number of instructions to process. You should increase the
6695 buffer-size with care.
6698 Not all recording formats may be available on all processors.
6701 The process record and replay target can only debug a process that is
6702 already running. Therefore, you need first to start the process with
6703 the @kbd{run} or @kbd{start} commands, and then start the recording
6704 with the @kbd{record @var{method}} command.
6706 @cindex displaced stepping, and process record and replay
6707 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6708 will be automatically disabled when process record and replay target
6709 is started. That's because the process record and replay target
6710 doesn't support displaced stepping.
6712 @cindex non-stop mode, and process record and replay
6713 @cindex asynchronous execution, and process record and replay
6714 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6715 the asynchronous execution mode (@pxref{Background Execution}), not
6716 all recording methods are available. The @code{full} recording method
6717 does not support these two modes.
6722 Stop the process record and replay target. When process record and
6723 replay target stops, the entire execution log will be deleted and the
6724 inferior will either be terminated, or will remain in its final state.
6726 When you stop the process record and replay target in record mode (at
6727 the end of the execution log), the inferior will be stopped at the
6728 next instruction that would have been recorded. In other words, if
6729 you record for a while and then stop recording, the inferior process
6730 will be left in the same state as if the recording never happened.
6732 On the other hand, if the process record and replay target is stopped
6733 while in replay mode (that is, not at the end of the execution log,
6734 but at some earlier point), the inferior process will become ``live''
6735 at that earlier state, and it will then be possible to continue the
6736 usual ``live'' debugging of the process from that state.
6738 When the inferior process exits, or @value{GDBN} detaches from it,
6739 process record and replay target will automatically stop itself.
6743 Go to a specific location in the execution log. There are several
6744 ways to specify the location to go to:
6747 @item record goto begin
6748 @itemx record goto start
6749 Go to the beginning of the execution log.
6751 @item record goto end
6752 Go to the end of the execution log.
6754 @item record goto @var{n}
6755 Go to instruction number @var{n} in the execution log.
6759 @item record save @var{filename}
6760 Save the execution log to a file @file{@var{filename}}.
6761 Default filename is @file{gdb_record.@var{process_id}}, where
6762 @var{process_id} is the process ID of the inferior.
6764 This command may not be available for all recording methods.
6766 @kindex record restore
6767 @item record restore @var{filename}
6768 Restore the execution log from a file @file{@var{filename}}.
6769 File must have been created with @code{record save}.
6771 @kindex set record full
6772 @item set record full insn-number-max @var{limit}
6773 @itemx set record full insn-number-max unlimited
6774 Set the limit of instructions to be recorded for the @code{full}
6775 recording method. Default value is 200000.
6777 If @var{limit} is a positive number, then @value{GDBN} will start
6778 deleting instructions from the log once the number of the record
6779 instructions becomes greater than @var{limit}. For every new recorded
6780 instruction, @value{GDBN} will delete the earliest recorded
6781 instruction to keep the number of recorded instructions at the limit.
6782 (Since deleting recorded instructions loses information, @value{GDBN}
6783 lets you control what happens when the limit is reached, by means of
6784 the @code{stop-at-limit} option, described below.)
6786 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6787 delete recorded instructions from the execution log. The number of
6788 recorded instructions is limited only by the available memory.
6790 @kindex show record full
6791 @item show record full insn-number-max
6792 Show the limit of instructions to be recorded with the @code{full}
6795 @item set record full stop-at-limit
6796 Control the behavior of the @code{full} recording method when the
6797 number of recorded instructions reaches the limit. If ON (the
6798 default), @value{GDBN} will stop when the limit is reached for the
6799 first time and ask you whether you want to stop the inferior or
6800 continue running it and recording the execution log. If you decide
6801 to continue recording, each new recorded instruction will cause the
6802 oldest one to be deleted.
6804 If this option is OFF, @value{GDBN} will automatically delete the
6805 oldest record to make room for each new one, without asking.
6807 @item show record full stop-at-limit
6808 Show the current setting of @code{stop-at-limit}.
6810 @item set record full memory-query
6811 Control the behavior when @value{GDBN} is unable to record memory
6812 changes caused by an instruction for the @code{full} recording method.
6813 If ON, @value{GDBN} will query whether to stop the inferior in that
6816 If this option is OFF (the default), @value{GDBN} will automatically
6817 ignore the effect of such instructions on memory. Later, when
6818 @value{GDBN} replays this execution log, it will mark the log of this
6819 instruction as not accessible, and it will not affect the replay
6822 @item show record full memory-query
6823 Show the current setting of @code{memory-query}.
6825 @kindex set record btrace
6826 The @code{btrace} record target does not trace data. As a
6827 convenience, when replaying, @value{GDBN} reads read-only memory off
6828 the live program directly, assuming that the addresses of the
6829 read-only areas don't change. This for example makes it possible to
6830 disassemble code while replaying, but not to print variables.
6831 In some cases, being able to inspect variables might be useful.
6832 You can use the following command for that:
6834 @item set record btrace replay-memory-access
6835 Control the behavior of the @code{btrace} recording method when
6836 accessing memory during replay. If @code{read-only} (the default),
6837 @value{GDBN} will only allow accesses to read-only memory.
6838 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6839 and to read-write memory. Beware that the accessed memory corresponds
6840 to the live target and not necessarily to the current replay
6843 @kindex show record btrace
6844 @item show record btrace replay-memory-access
6845 Show the current setting of @code{replay-memory-access}.
6847 @kindex set record btrace bts
6848 @item set record btrace bts buffer-size @var{size}
6849 @itemx set record btrace bts buffer-size unlimited
6850 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6851 format. Default is 64KB.
6853 If @var{size} is a positive number, then @value{GDBN} will try to
6854 allocate a buffer of at least @var{size} bytes for each new thread
6855 that uses the btrace recording method and the @acronym{BTS} format.
6856 The actually obtained buffer size may differ from the requested
6857 @var{size}. Use the @code{info record} command to see the actual
6858 buffer size for each thread that uses the btrace recording method and
6859 the @acronym{BTS} format.
6861 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6862 allocate a buffer of 4MB.
6864 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6865 also need longer to process the branch trace data before it can be used.
6867 @item show record btrace bts buffer-size @var{size}
6868 Show the current setting of the requested ring buffer size for branch
6869 tracing in @acronym{BTS} format.
6871 @kindex set record btrace pt
6872 @item set record btrace pt buffer-size @var{size}
6873 @itemx set record btrace pt buffer-size unlimited
6874 Set the requested ring buffer size for branch tracing in Intel
6875 Processor Trace format. Default is 16KB.
6877 If @var{size} is a positive number, then @value{GDBN} will try to
6878 allocate a buffer of at least @var{size} bytes for each new thread
6879 that uses the btrace recording method and the Intel Processor Trace
6880 format. The actually obtained buffer size may differ from the
6881 requested @var{size}. Use the @code{info record} command to see the
6882 actual buffer size for each thread.
6884 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6885 allocate a buffer of 4MB.
6887 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6888 also need longer to process the branch trace data before it can be used.
6890 @item show record btrace pt buffer-size @var{size}
6891 Show the current setting of the requested ring buffer size for branch
6892 tracing in Intel Processor Trace format.
6896 Show various statistics about the recording depending on the recording
6901 For the @code{full} recording method, it shows the state of process
6902 record and its in-memory execution log buffer, including:
6906 Whether in record mode or replay mode.
6908 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6910 Highest recorded instruction number.
6912 Current instruction about to be replayed (if in replay mode).
6914 Number of instructions contained in the execution log.
6916 Maximum number of instructions that may be contained in the execution log.
6920 For the @code{btrace} recording method, it shows:
6926 Number of instructions that have been recorded.
6928 Number of blocks of sequential control-flow formed by the recorded
6931 Whether in record mode or replay mode.
6934 For the @code{bts} recording format, it also shows:
6937 Size of the perf ring buffer.
6940 For the @code{pt} recording format, it also shows:
6943 Size of the perf ring buffer.
6947 @kindex record delete
6950 When record target runs in replay mode (``in the past''), delete the
6951 subsequent execution log and begin to record a new execution log starting
6952 from the current address. This means you will abandon the previously
6953 recorded ``future'' and begin recording a new ``future''.
6955 @kindex record instruction-history
6956 @kindex rec instruction-history
6957 @item record instruction-history
6958 Disassembles instructions from the recorded execution log. By
6959 default, ten instructions are disassembled. This can be changed using
6960 the @code{set record instruction-history-size} command. Instructions
6961 are printed in execution order.
6963 It can also print mixed source+disassembly if you specify the the
6964 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6965 as well as in symbolic form by specifying the @code{/r} modifier.
6967 The current position marker is printed for the instruction at the
6968 current program counter value. This instruction can appear multiple
6969 times in the trace and the current position marker will be printed
6970 every time. To omit the current position marker, specify the
6973 To better align the printed instructions when the trace contains
6974 instructions from more than one function, the function name may be
6975 omitted by specifying the @code{/f} modifier.
6977 Speculatively executed instructions are prefixed with @samp{?}. This
6978 feature is not available for all recording formats.
6980 There are several ways to specify what part of the execution log to
6984 @item record instruction-history @var{insn}
6985 Disassembles ten instructions starting from instruction number
6988 @item record instruction-history @var{insn}, +/-@var{n}
6989 Disassembles @var{n} instructions around instruction number
6990 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6991 @var{n} instructions after instruction number @var{insn}. If
6992 @var{n} is preceded with @code{-}, disassembles @var{n}
6993 instructions before instruction number @var{insn}.
6995 @item record instruction-history
6996 Disassembles ten more instructions after the last disassembly.
6998 @item record instruction-history -
6999 Disassembles ten more instructions before the last disassembly.
7001 @item record instruction-history @var{begin}, @var{end}
7002 Disassembles instructions beginning with instruction number
7003 @var{begin} until instruction number @var{end}. The instruction
7004 number @var{end} is included.
7007 This command may not be available for all recording methods.
7010 @item set record instruction-history-size @var{size}
7011 @itemx set record instruction-history-size unlimited
7012 Define how many instructions to disassemble in the @code{record
7013 instruction-history} command. The default value is 10.
7014 A @var{size} of @code{unlimited} means unlimited instructions.
7017 @item show record instruction-history-size
7018 Show how many instructions to disassemble in the @code{record
7019 instruction-history} command.
7021 @kindex record function-call-history
7022 @kindex rec function-call-history
7023 @item record function-call-history
7024 Prints the execution history at function granularity. It prints one
7025 line for each sequence of instructions that belong to the same
7026 function giving the name of that function, the source lines
7027 for this instruction sequence (if the @code{/l} modifier is
7028 specified), and the instructions numbers that form the sequence (if
7029 the @code{/i} modifier is specified). The function names are indented
7030 to reflect the call stack depth if the @code{/c} modifier is
7031 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7035 (@value{GDBP}) @b{list 1, 10}
7046 (@value{GDBP}) @b{record function-call-history /ilc}
7047 1 bar inst 1,4 at foo.c:6,8
7048 2 foo inst 5,10 at foo.c:2,3
7049 3 bar inst 11,13 at foo.c:9,10
7052 By default, ten lines are printed. This can be changed using the
7053 @code{set record function-call-history-size} command. Functions are
7054 printed in execution order. There are several ways to specify what
7058 @item record function-call-history @var{func}
7059 Prints ten functions starting from function number @var{func}.
7061 @item record function-call-history @var{func}, +/-@var{n}
7062 Prints @var{n} functions around function number @var{func}. If
7063 @var{n} is preceded with @code{+}, prints @var{n} functions after
7064 function number @var{func}. If @var{n} is preceded with @code{-},
7065 prints @var{n} functions before function number @var{func}.
7067 @item record function-call-history
7068 Prints ten more functions after the last ten-line print.
7070 @item record function-call-history -
7071 Prints ten more functions before the last ten-line print.
7073 @item record function-call-history @var{begin}, @var{end}
7074 Prints functions beginning with function number @var{begin} until
7075 function number @var{end}. The function number @var{end} is included.
7078 This command may not be available for all recording methods.
7080 @item set record function-call-history-size @var{size}
7081 @itemx set record function-call-history-size unlimited
7082 Define how many lines to print in the
7083 @code{record function-call-history} command. The default value is 10.
7084 A size of @code{unlimited} means unlimited lines.
7086 @item show record function-call-history-size
7087 Show how many lines to print in the
7088 @code{record function-call-history} command.
7093 @chapter Examining the Stack
7095 When your program has stopped, the first thing you need to know is where it
7096 stopped and how it got there.
7099 Each time your program performs a function call, information about the call
7101 That information includes the location of the call in your program,
7102 the arguments of the call,
7103 and the local variables of the function being called.
7104 The information is saved in a block of data called a @dfn{stack frame}.
7105 The stack frames are allocated in a region of memory called the @dfn{call
7108 When your program stops, the @value{GDBN} commands for examining the
7109 stack allow you to see all of this information.
7111 @cindex selected frame
7112 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7113 @value{GDBN} commands refer implicitly to the selected frame. In
7114 particular, whenever you ask @value{GDBN} for the value of a variable in
7115 your program, the value is found in the selected frame. There are
7116 special @value{GDBN} commands to select whichever frame you are
7117 interested in. @xref{Selection, ,Selecting a Frame}.
7119 When your program stops, @value{GDBN} automatically selects the
7120 currently executing frame and describes it briefly, similar to the
7121 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7124 * Frames:: Stack frames
7125 * Backtrace:: Backtraces
7126 * Selection:: Selecting a frame
7127 * Frame Info:: Information on a frame
7128 * Frame Filter Management:: Managing frame filters
7133 @section Stack Frames
7135 @cindex frame, definition
7137 The call stack is divided up into contiguous pieces called @dfn{stack
7138 frames}, or @dfn{frames} for short; each frame is the data associated
7139 with one call to one function. The frame contains the arguments given
7140 to the function, the function's local variables, and the address at
7141 which the function is executing.
7143 @cindex initial frame
7144 @cindex outermost frame
7145 @cindex innermost frame
7146 When your program is started, the stack has only one frame, that of the
7147 function @code{main}. This is called the @dfn{initial} frame or the
7148 @dfn{outermost} frame. Each time a function is called, a new frame is
7149 made. Each time a function returns, the frame for that function invocation
7150 is eliminated. If a function is recursive, there can be many frames for
7151 the same function. The frame for the function in which execution is
7152 actually occurring is called the @dfn{innermost} frame. This is the most
7153 recently created of all the stack frames that still exist.
7155 @cindex frame pointer
7156 Inside your program, stack frames are identified by their addresses. A
7157 stack frame consists of many bytes, each of which has its own address; each
7158 kind of computer has a convention for choosing one byte whose
7159 address serves as the address of the frame. Usually this address is kept
7160 in a register called the @dfn{frame pointer register}
7161 (@pxref{Registers, $fp}) while execution is going on in that frame.
7163 @cindex frame number
7164 @value{GDBN} assigns numbers to all existing stack frames, starting with
7165 zero for the innermost frame, one for the frame that called it,
7166 and so on upward. These numbers do not really exist in your program;
7167 they are assigned by @value{GDBN} to give you a way of designating stack
7168 frames in @value{GDBN} commands.
7170 @c The -fomit-frame-pointer below perennially causes hbox overflow
7171 @c underflow problems.
7172 @cindex frameless execution
7173 Some compilers provide a way to compile functions so that they operate
7174 without stack frames. (For example, the @value{NGCC} option
7176 @samp{-fomit-frame-pointer}
7178 generates functions without a frame.)
7179 This is occasionally done with heavily used library functions to save
7180 the frame setup time. @value{GDBN} has limited facilities for dealing
7181 with these function invocations. If the innermost function invocation
7182 has no stack frame, @value{GDBN} nevertheless regards it as though
7183 it had a separate frame, which is numbered zero as usual, allowing
7184 correct tracing of the function call chain. However, @value{GDBN} has
7185 no provision for frameless functions elsewhere in the stack.
7191 @cindex call stack traces
7192 A backtrace is a summary of how your program got where it is. It shows one
7193 line per frame, for many frames, starting with the currently executing
7194 frame (frame zero), followed by its caller (frame one), and on up the
7197 @anchor{backtrace-command}
7200 @kindex bt @r{(@code{backtrace})}
7203 Print a backtrace of the entire stack: one line per frame for all
7204 frames in the stack.
7206 You can stop the backtrace at any time by typing the system interrupt
7207 character, normally @kbd{Ctrl-c}.
7209 @item backtrace @var{n}
7211 Similar, but print only the innermost @var{n} frames.
7213 @item backtrace -@var{n}
7215 Similar, but print only the outermost @var{n} frames.
7217 @item backtrace full
7219 @itemx bt full @var{n}
7220 @itemx bt full -@var{n}
7221 Print the values of the local variables also. As described above,
7222 @var{n} specifies the number of frames to print.
7224 @item backtrace no-filters
7225 @itemx bt no-filters
7226 @itemx bt no-filters @var{n}
7227 @itemx bt no-filters -@var{n}
7228 @itemx bt no-filters full
7229 @itemx bt no-filters full @var{n}
7230 @itemx bt no-filters full -@var{n}
7231 Do not run Python frame filters on this backtrace. @xref{Frame
7232 Filter API}, for more information. Additionally use @ref{disable
7233 frame-filter all} to turn off all frame filters. This is only
7234 relevant when @value{GDBN} has been configured with @code{Python}
7240 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7241 are additional aliases for @code{backtrace}.
7243 @cindex multiple threads, backtrace
7244 In a multi-threaded program, @value{GDBN} by default shows the
7245 backtrace only for the current thread. To display the backtrace for
7246 several or all of the threads, use the command @code{thread apply}
7247 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7248 apply all backtrace}, @value{GDBN} will display the backtrace for all
7249 the threads; this is handy when you debug a core dump of a
7250 multi-threaded program.
7252 Each line in the backtrace shows the frame number and the function name.
7253 The program counter value is also shown---unless you use @code{set
7254 print address off}. The backtrace also shows the source file name and
7255 line number, as well as the arguments to the function. The program
7256 counter value is omitted if it is at the beginning of the code for that
7259 Here is an example of a backtrace. It was made with the command
7260 @samp{bt 3}, so it shows the innermost three frames.
7264 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7266 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7267 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7269 (More stack frames follow...)
7274 The display for frame zero does not begin with a program counter
7275 value, indicating that your program has stopped at the beginning of the
7276 code for line @code{993} of @code{builtin.c}.
7279 The value of parameter @code{data} in frame 1 has been replaced by
7280 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7281 only if it is a scalar (integer, pointer, enumeration, etc). See command
7282 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7283 on how to configure the way function parameter values are printed.
7285 @cindex optimized out, in backtrace
7286 @cindex function call arguments, optimized out
7287 If your program was compiled with optimizations, some compilers will
7288 optimize away arguments passed to functions if those arguments are
7289 never used after the call. Such optimizations generate code that
7290 passes arguments through registers, but doesn't store those arguments
7291 in the stack frame. @value{GDBN} has no way of displaying such
7292 arguments in stack frames other than the innermost one. Here's what
7293 such a backtrace might look like:
7297 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7299 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7300 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7302 (More stack frames follow...)
7307 The values of arguments that were not saved in their stack frames are
7308 shown as @samp{<optimized out>}.
7310 If you need to display the values of such optimized-out arguments,
7311 either deduce that from other variables whose values depend on the one
7312 you are interested in, or recompile without optimizations.
7314 @cindex backtrace beyond @code{main} function
7315 @cindex program entry point
7316 @cindex startup code, and backtrace
7317 Most programs have a standard user entry point---a place where system
7318 libraries and startup code transition into user code. For C this is
7319 @code{main}@footnote{
7320 Note that embedded programs (the so-called ``free-standing''
7321 environment) are not required to have a @code{main} function as the
7322 entry point. They could even have multiple entry points.}.
7323 When @value{GDBN} finds the entry function in a backtrace
7324 it will terminate the backtrace, to avoid tracing into highly
7325 system-specific (and generally uninteresting) code.
7327 If you need to examine the startup code, or limit the number of levels
7328 in a backtrace, you can change this behavior:
7331 @item set backtrace past-main
7332 @itemx set backtrace past-main on
7333 @kindex set backtrace
7334 Backtraces will continue past the user entry point.
7336 @item set backtrace past-main off
7337 Backtraces will stop when they encounter the user entry point. This is the
7340 @item show backtrace past-main
7341 @kindex show backtrace
7342 Display the current user entry point backtrace policy.
7344 @item set backtrace past-entry
7345 @itemx set backtrace past-entry on
7346 Backtraces will continue past the internal entry point of an application.
7347 This entry point is encoded by the linker when the application is built,
7348 and is likely before the user entry point @code{main} (or equivalent) is called.
7350 @item set backtrace past-entry off
7351 Backtraces will stop when they encounter the internal entry point of an
7352 application. This is the default.
7354 @item show backtrace past-entry
7355 Display the current internal entry point backtrace policy.
7357 @item set backtrace limit @var{n}
7358 @itemx set backtrace limit 0
7359 @itemx set backtrace limit unlimited
7360 @cindex backtrace limit
7361 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7362 or zero means unlimited levels.
7364 @item show backtrace limit
7365 Display the current limit on backtrace levels.
7368 You can control how file names are displayed.
7371 @item set filename-display
7372 @itemx set filename-display relative
7373 @cindex filename-display
7374 Display file names relative to the compilation directory. This is the default.
7376 @item set filename-display basename
7377 Display only basename of a filename.
7379 @item set filename-display absolute
7380 Display an absolute filename.
7382 @item show filename-display
7383 Show the current way to display filenames.
7387 @section Selecting a Frame
7389 Most commands for examining the stack and other data in your program work on
7390 whichever stack frame is selected at the moment. Here are the commands for
7391 selecting a stack frame; all of them finish by printing a brief description
7392 of the stack frame just selected.
7395 @kindex frame@r{, selecting}
7396 @kindex f @r{(@code{frame})}
7399 Select frame number @var{n}. Recall that frame zero is the innermost
7400 (currently executing) frame, frame one is the frame that called the
7401 innermost one, and so on. The highest-numbered frame is the one for
7404 @item frame @var{stack-addr} [ @var{pc-addr} ]
7405 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7406 Select the frame at address @var{stack-addr}. This is useful mainly if the
7407 chaining of stack frames has been damaged by a bug, making it
7408 impossible for @value{GDBN} to assign numbers properly to all frames. In
7409 addition, this can be useful when your program has multiple stacks and
7410 switches between them. The optional @var{pc-addr} can also be given to
7411 specify the value of PC for the stack frame.
7415 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7416 numbers @var{n}, this advances toward the outermost frame, to higher
7417 frame numbers, to frames that have existed longer.
7420 @kindex do @r{(@code{down})}
7422 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7423 positive numbers @var{n}, this advances toward the innermost frame, to
7424 lower frame numbers, to frames that were created more recently.
7425 You may abbreviate @code{down} as @code{do}.
7428 All of these commands end by printing two lines of output describing the
7429 frame. The first line shows the frame number, the function name, the
7430 arguments, and the source file and line number of execution in that
7431 frame. The second line shows the text of that source line.
7439 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7441 10 read_input_file (argv[i]);
7445 After such a printout, the @code{list} command with no arguments
7446 prints ten lines centered on the point of execution in the frame.
7447 You can also edit the program at the point of execution with your favorite
7448 editing program by typing @code{edit}.
7449 @xref{List, ,Printing Source Lines},
7453 @kindex select-frame
7455 The @code{select-frame} command is a variant of @code{frame} that does
7456 not display the new frame after selecting it. This command is
7457 intended primarily for use in @value{GDBN} command scripts, where the
7458 output might be unnecessary and distracting.
7460 @kindex down-silently
7462 @item up-silently @var{n}
7463 @itemx down-silently @var{n}
7464 These two commands are variants of @code{up} and @code{down},
7465 respectively; they differ in that they do their work silently, without
7466 causing display of the new frame. They are intended primarily for use
7467 in @value{GDBN} command scripts, where the output might be unnecessary and
7472 @section Information About a Frame
7474 There are several other commands to print information about the selected
7480 When used without any argument, this command does not change which
7481 frame is selected, but prints a brief description of the currently
7482 selected stack frame. It can be abbreviated @code{f}. With an
7483 argument, this command is used to select a stack frame.
7484 @xref{Selection, ,Selecting a Frame}.
7487 @kindex info f @r{(@code{info frame})}
7490 This command prints a verbose description of the selected stack frame,
7495 the address of the frame
7497 the address of the next frame down (called by this frame)
7499 the address of the next frame up (caller of this frame)
7501 the language in which the source code corresponding to this frame is written
7503 the address of the frame's arguments
7505 the address of the frame's local variables
7507 the program counter saved in it (the address of execution in the caller frame)
7509 which registers were saved in the frame
7512 @noindent The verbose description is useful when
7513 something has gone wrong that has made the stack format fail to fit
7514 the usual conventions.
7516 @item info frame @var{addr}
7517 @itemx info f @var{addr}
7518 Print a verbose description of the frame at address @var{addr}, without
7519 selecting that frame. The selected frame remains unchanged by this
7520 command. This requires the same kind of address (more than one for some
7521 architectures) that you specify in the @code{frame} command.
7522 @xref{Selection, ,Selecting a Frame}.
7526 Print the arguments of the selected frame, each on a separate line.
7530 Print the local variables of the selected frame, each on a separate
7531 line. These are all variables (declared either static or automatic)
7532 accessible at the point of execution of the selected frame.
7536 @node Frame Filter Management
7537 @section Management of Frame Filters.
7538 @cindex managing frame filters
7540 Frame filters are Python based utilities to manage and decorate the
7541 output of frames. @xref{Frame Filter API}, for further information.
7543 Managing frame filters is performed by several commands available
7544 within @value{GDBN}, detailed here.
7547 @kindex info frame-filter
7548 @item info frame-filter
7549 Print a list of installed frame filters from all dictionaries, showing
7550 their name, priority and enabled status.
7552 @kindex disable frame-filter
7553 @anchor{disable frame-filter all}
7554 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7555 Disable a frame filter in the dictionary matching
7556 @var{filter-dictionary} and @var{filter-name}. The
7557 @var{filter-dictionary} may be @code{all}, @code{global},
7558 @code{progspace}, or the name of the object file where the frame filter
7559 dictionary resides. When @code{all} is specified, all frame filters
7560 across all dictionaries are disabled. The @var{filter-name} is the name
7561 of the frame filter and is used when @code{all} is not the option for
7562 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7563 may be enabled again later.
7565 @kindex enable frame-filter
7566 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7567 Enable a frame filter in the dictionary matching
7568 @var{filter-dictionary} and @var{filter-name}. The
7569 @var{filter-dictionary} may be @code{all}, @code{global},
7570 @code{progspace} or the name of the object file where the frame filter
7571 dictionary resides. When @code{all} is specified, all frame filters across
7572 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7573 filter and is used when @code{all} is not the option for
7574 @var{filter-dictionary}.
7579 (gdb) info frame-filter
7581 global frame-filters:
7582 Priority Enabled Name
7583 1000 No PrimaryFunctionFilter
7586 progspace /build/test frame-filters:
7587 Priority Enabled Name
7588 100 Yes ProgspaceFilter
7590 objfile /build/test frame-filters:
7591 Priority Enabled Name
7592 999 Yes BuildProgra Filter
7594 (gdb) disable frame-filter /build/test BuildProgramFilter
7595 (gdb) info frame-filter
7597 global frame-filters:
7598 Priority Enabled Name
7599 1000 No PrimaryFunctionFilter
7602 progspace /build/test frame-filters:
7603 Priority Enabled Name
7604 100 Yes ProgspaceFilter
7606 objfile /build/test frame-filters:
7607 Priority Enabled Name
7608 999 No BuildProgramFilter
7610 (gdb) enable frame-filter global PrimaryFunctionFilter
7611 (gdb) info frame-filter
7613 global frame-filters:
7614 Priority Enabled Name
7615 1000 Yes PrimaryFunctionFilter
7618 progspace /build/test frame-filters:
7619 Priority Enabled Name
7620 100 Yes ProgspaceFilter
7622 objfile /build/test frame-filters:
7623 Priority Enabled Name
7624 999 No BuildProgramFilter
7627 @kindex set frame-filter priority
7628 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7629 Set the @var{priority} of a frame filter in the dictionary matching
7630 @var{filter-dictionary}, and the frame filter name matching
7631 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7632 @code{progspace} or the name of the object file where the frame filter
7633 dictionary resides. The @var{priority} is an integer.
7635 @kindex show frame-filter priority
7636 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7637 Show the @var{priority} of a frame filter in the dictionary matching
7638 @var{filter-dictionary}, and the frame filter name matching
7639 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7640 @code{progspace} or the name of the object file where the frame filter
7646 (gdb) info frame-filter
7648 global frame-filters:
7649 Priority Enabled Name
7650 1000 Yes PrimaryFunctionFilter
7653 progspace /build/test frame-filters:
7654 Priority Enabled Name
7655 100 Yes ProgspaceFilter
7657 objfile /build/test frame-filters:
7658 Priority Enabled Name
7659 999 No BuildProgramFilter
7661 (gdb) set frame-filter priority global Reverse 50
7662 (gdb) info frame-filter
7664 global frame-filters:
7665 Priority Enabled Name
7666 1000 Yes PrimaryFunctionFilter
7669 progspace /build/test frame-filters:
7670 Priority Enabled Name
7671 100 Yes ProgspaceFilter
7673 objfile /build/test frame-filters:
7674 Priority Enabled Name
7675 999 No BuildProgramFilter
7680 @chapter Examining Source Files
7682 @value{GDBN} can print parts of your program's source, since the debugging
7683 information recorded in the program tells @value{GDBN} what source files were
7684 used to build it. When your program stops, @value{GDBN} spontaneously prints
7685 the line where it stopped. Likewise, when you select a stack frame
7686 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7687 execution in that frame has stopped. You can print other portions of
7688 source files by explicit command.
7690 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7691 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7692 @value{GDBN} under @sc{gnu} Emacs}.
7695 * List:: Printing source lines
7696 * Specify Location:: How to specify code locations
7697 * Edit:: Editing source files
7698 * Search:: Searching source files
7699 * Source Path:: Specifying source directories
7700 * Machine Code:: Source and machine code
7704 @section Printing Source Lines
7707 @kindex l @r{(@code{list})}
7708 To print lines from a source file, use the @code{list} command
7709 (abbreviated @code{l}). By default, ten lines are printed.
7710 There are several ways to specify what part of the file you want to
7711 print; see @ref{Specify Location}, for the full list.
7713 Here are the forms of the @code{list} command most commonly used:
7716 @item list @var{linenum}
7717 Print lines centered around line number @var{linenum} in the
7718 current source file.
7720 @item list @var{function}
7721 Print lines centered around the beginning of function
7725 Print more lines. If the last lines printed were printed with a
7726 @code{list} command, this prints lines following the last lines
7727 printed; however, if the last line printed was a solitary line printed
7728 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7729 Stack}), this prints lines centered around that line.
7732 Print lines just before the lines last printed.
7735 @cindex @code{list}, how many lines to display
7736 By default, @value{GDBN} prints ten source lines with any of these forms of
7737 the @code{list} command. You can change this using @code{set listsize}:
7740 @kindex set listsize
7741 @item set listsize @var{count}
7742 @itemx set listsize unlimited
7743 Make the @code{list} command display @var{count} source lines (unless
7744 the @code{list} argument explicitly specifies some other number).
7745 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7747 @kindex show listsize
7749 Display the number of lines that @code{list} prints.
7752 Repeating a @code{list} command with @key{RET} discards the argument,
7753 so it is equivalent to typing just @code{list}. This is more useful
7754 than listing the same lines again. An exception is made for an
7755 argument of @samp{-}; that argument is preserved in repetition so that
7756 each repetition moves up in the source file.
7758 In general, the @code{list} command expects you to supply zero, one or two
7759 @dfn{locations}. Locations specify source lines; there are several ways
7760 of writing them (@pxref{Specify Location}), but the effect is always
7761 to specify some source line.
7763 Here is a complete description of the possible arguments for @code{list}:
7766 @item list @var{location}
7767 Print lines centered around the line specified by @var{location}.
7769 @item list @var{first},@var{last}
7770 Print lines from @var{first} to @var{last}. Both arguments are
7771 locations. When a @code{list} command has two locations, and the
7772 source file of the second location is omitted, this refers to
7773 the same source file as the first location.
7775 @item list ,@var{last}
7776 Print lines ending with @var{last}.
7778 @item list @var{first},
7779 Print lines starting with @var{first}.
7782 Print lines just after the lines last printed.
7785 Print lines just before the lines last printed.
7788 As described in the preceding table.
7791 @node Specify Location
7792 @section Specifying a Location
7793 @cindex specifying location
7795 @cindex source location
7798 * Linespec Locations:: Linespec locations
7799 * Explicit Locations:: Explicit locations
7800 * Address Locations:: Address locations
7803 Several @value{GDBN} commands accept arguments that specify a location
7804 of your program's code. Since @value{GDBN} is a source-level
7805 debugger, a location usually specifies some line in the source code.
7806 Locations may be specified using three different formats:
7807 linespec locations, explicit locations, or address locations.
7809 @node Linespec Locations
7810 @subsection Linespec Locations
7811 @cindex linespec locations
7813 A @dfn{linespec} is a colon-separated list of source location parameters such
7814 as file name, function name, etc. Here are all the different ways of
7815 specifying a linespec:
7819 Specifies the line number @var{linenum} of the current source file.
7822 @itemx +@var{offset}
7823 Specifies the line @var{offset} lines before or after the @dfn{current
7824 line}. For the @code{list} command, the current line is the last one
7825 printed; for the breakpoint commands, this is the line at which
7826 execution stopped in the currently selected @dfn{stack frame}
7827 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7828 used as the second of the two linespecs in a @code{list} command,
7829 this specifies the line @var{offset} lines up or down from the first
7832 @item @var{filename}:@var{linenum}
7833 Specifies the line @var{linenum} in the source file @var{filename}.
7834 If @var{filename} is a relative file name, then it will match any
7835 source file name with the same trailing components. For example, if
7836 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7837 name of @file{/build/trunk/gcc/expr.c}, but not
7838 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7840 @item @var{function}
7841 Specifies the line that begins the body of the function @var{function}.
7842 For example, in C, this is the line with the open brace.
7844 @item @var{function}:@var{label}
7845 Specifies the line where @var{label} appears in @var{function}.
7847 @item @var{filename}:@var{function}
7848 Specifies the line that begins the body of the function @var{function}
7849 in the file @var{filename}. You only need the file name with a
7850 function name to avoid ambiguity when there are identically named
7851 functions in different source files.
7854 Specifies the line at which the label named @var{label} appears
7855 in the function corresponding to the currently selected stack frame.
7856 If there is no current selected stack frame (for instance, if the inferior
7857 is not running), then @value{GDBN} will not search for a label.
7859 @cindex breakpoint at static probe point
7860 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7861 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7862 applications to embed static probes. @xref{Static Probe Points}, for more
7863 information on finding and using static probes. This form of linespec
7864 specifies the location of such a static probe.
7866 If @var{objfile} is given, only probes coming from that shared library
7867 or executable matching @var{objfile} as a regular expression are considered.
7868 If @var{provider} is given, then only probes from that provider are considered.
7869 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7870 each one of those probes.
7873 @node Explicit Locations
7874 @subsection Explicit Locations
7875 @cindex explicit locations
7877 @dfn{Explicit locations} allow the user to directly specify the source
7878 location's parameters using option-value pairs.
7880 Explicit locations are useful when several functions, labels, or
7881 file names have the same name (base name for files) in the program's
7882 sources. In these cases, explicit locations point to the source
7883 line you meant more accurately and unambiguously. Also, using
7884 explicit locations might be faster in large programs.
7886 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7887 defined in the file named @file{foo} or the label @code{bar} in a function
7888 named @code{foo}. @value{GDBN} must search either the file system or
7889 the symbol table to know.
7891 The list of valid explicit location options is summarized in the
7895 @item -source @var{filename}
7896 The value specifies the source file name. To differentiate between
7897 files with the same base name, prepend as many directories as is necessary
7898 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7899 @value{GDBN} will use the first file it finds with the given base
7900 name. This option requires the use of either @code{-function} or @code{-line}.
7902 @item -function @var{function}
7903 The value specifies the name of a function. Operations
7904 on function locations unmodified by other options (such as @code{-label}
7905 or @code{-line}) refer to the line that begins the body of the function.
7906 In C, for example, this is the line with the open brace.
7908 @item -label @var{label}
7909 The value specifies the name of a label. When the function
7910 name is not specified, the label is searched in the function of the currently
7911 selected stack frame.
7913 @item -line @var{number}
7914 The value specifies a line offset for the location. The offset may either
7915 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7916 the command. When specified without any other options, the line offset is
7917 relative to the current line.
7920 Explicit location options may be abbreviated by omitting any non-unique
7921 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7923 @node Address Locations
7924 @subsection Address Locations
7925 @cindex address locations
7927 @dfn{Address locations} indicate a specific program address. They have
7928 the generalized form *@var{address}.
7930 For line-oriented commands, such as @code{list} and @code{edit}, this
7931 specifies a source line that contains @var{address}. For @code{break} and
7932 other breakpoint-oriented commands, this can be used to set breakpoints in
7933 parts of your program which do not have debugging information or
7936 Here @var{address} may be any expression valid in the current working
7937 language (@pxref{Languages, working language}) that specifies a code
7938 address. In addition, as a convenience, @value{GDBN} extends the
7939 semantics of expressions used in locations to cover several situations
7940 that frequently occur during debugging. Here are the various forms
7944 @item @var{expression}
7945 Any expression valid in the current working language.
7947 @item @var{funcaddr}
7948 An address of a function or procedure derived from its name. In C,
7949 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
7950 simply the function's name @var{function} (and actually a special case
7951 of a valid expression). In Pascal and Modula-2, this is
7952 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7953 (although the Pascal form also works).
7955 This form specifies the address of the function's first instruction,
7956 before the stack frame and arguments have been set up.
7958 @item '@var{filename}':@var{funcaddr}
7959 Like @var{funcaddr} above, but also specifies the name of the source
7960 file explicitly. This is useful if the name of the function does not
7961 specify the function unambiguously, e.g., if there are several
7962 functions with identical names in different source files.
7966 @section Editing Source Files
7967 @cindex editing source files
7970 @kindex e @r{(@code{edit})}
7971 To edit the lines in a source file, use the @code{edit} command.
7972 The editing program of your choice
7973 is invoked with the current line set to
7974 the active line in the program.
7975 Alternatively, there are several ways to specify what part of the file you
7976 want to print if you want to see other parts of the program:
7979 @item edit @var{location}
7980 Edit the source file specified by @code{location}. Editing starts at
7981 that @var{location}, e.g., at the specified source line of the
7982 specified file. @xref{Specify Location}, for all the possible forms
7983 of the @var{location} argument; here are the forms of the @code{edit}
7984 command most commonly used:
7987 @item edit @var{number}
7988 Edit the current source file with @var{number} as the active line number.
7990 @item edit @var{function}
7991 Edit the file containing @var{function} at the beginning of its definition.
7996 @subsection Choosing your Editor
7997 You can customize @value{GDBN} to use any editor you want
7999 The only restriction is that your editor (say @code{ex}), recognizes the
8000 following command-line syntax:
8002 ex +@var{number} file
8004 The optional numeric value +@var{number} specifies the number of the line in
8005 the file where to start editing.}.
8006 By default, it is @file{@value{EDITOR}}, but you can change this
8007 by setting the environment variable @code{EDITOR} before using
8008 @value{GDBN}. For example, to configure @value{GDBN} to use the
8009 @code{vi} editor, you could use these commands with the @code{sh} shell:
8015 or in the @code{csh} shell,
8017 setenv EDITOR /usr/bin/vi
8022 @section Searching Source Files
8023 @cindex searching source files
8025 There are two commands for searching through the current source file for a
8030 @kindex forward-search
8031 @kindex fo @r{(@code{forward-search})}
8032 @item forward-search @var{regexp}
8033 @itemx search @var{regexp}
8034 The command @samp{forward-search @var{regexp}} checks each line,
8035 starting with the one following the last line listed, for a match for
8036 @var{regexp}. It lists the line that is found. You can use the
8037 synonym @samp{search @var{regexp}} or abbreviate the command name as
8040 @kindex reverse-search
8041 @item reverse-search @var{regexp}
8042 The command @samp{reverse-search @var{regexp}} checks each line, starting
8043 with the one before the last line listed and going backward, for a match
8044 for @var{regexp}. It lists the line that is found. You can abbreviate
8045 this command as @code{rev}.
8049 @section Specifying Source Directories
8052 @cindex directories for source files
8053 Executable programs sometimes do not record the directories of the source
8054 files from which they were compiled, just the names. Even when they do,
8055 the directories could be moved between the compilation and your debugging
8056 session. @value{GDBN} has a list of directories to search for source files;
8057 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8058 it tries all the directories in the list, in the order they are present
8059 in the list, until it finds a file with the desired name.
8061 For example, suppose an executable references the file
8062 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8063 @file{/mnt/cross}. The file is first looked up literally; if this
8064 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8065 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8066 message is printed. @value{GDBN} does not look up the parts of the
8067 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8068 Likewise, the subdirectories of the source path are not searched: if
8069 the source path is @file{/mnt/cross}, and the binary refers to
8070 @file{foo.c}, @value{GDBN} would not find it under
8071 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8073 Plain file names, relative file names with leading directories, file
8074 names containing dots, etc.@: are all treated as described above; for
8075 instance, if the source path is @file{/mnt/cross}, and the source file
8076 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8077 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8078 that---@file{/mnt/cross/foo.c}.
8080 Note that the executable search path is @emph{not} used to locate the
8083 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8084 any information it has cached about where source files are found and where
8085 each line is in the file.
8089 When you start @value{GDBN}, its source path includes only @samp{cdir}
8090 and @samp{cwd}, in that order.
8091 To add other directories, use the @code{directory} command.
8093 The search path is used to find both program source files and @value{GDBN}
8094 script files (read using the @samp{-command} option and @samp{source} command).
8096 In addition to the source path, @value{GDBN} provides a set of commands
8097 that manage a list of source path substitution rules. A @dfn{substitution
8098 rule} specifies how to rewrite source directories stored in the program's
8099 debug information in case the sources were moved to a different
8100 directory between compilation and debugging. A rule is made of
8101 two strings, the first specifying what needs to be rewritten in
8102 the path, and the second specifying how it should be rewritten.
8103 In @ref{set substitute-path}, we name these two parts @var{from} and
8104 @var{to} respectively. @value{GDBN} does a simple string replacement
8105 of @var{from} with @var{to} at the start of the directory part of the
8106 source file name, and uses that result instead of the original file
8107 name to look up the sources.
8109 Using the previous example, suppose the @file{foo-1.0} tree has been
8110 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8111 @value{GDBN} to replace @file{/usr/src} in all source path names with
8112 @file{/mnt/cross}. The first lookup will then be
8113 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8114 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8115 substitution rule, use the @code{set substitute-path} command
8116 (@pxref{set substitute-path}).
8118 To avoid unexpected substitution results, a rule is applied only if the
8119 @var{from} part of the directory name ends at a directory separator.
8120 For instance, a rule substituting @file{/usr/source} into
8121 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8122 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8123 is applied only at the beginning of the directory name, this rule will
8124 not be applied to @file{/root/usr/source/baz.c} either.
8126 In many cases, you can achieve the same result using the @code{directory}
8127 command. However, @code{set substitute-path} can be more efficient in
8128 the case where the sources are organized in a complex tree with multiple
8129 subdirectories. With the @code{directory} command, you need to add each
8130 subdirectory of your project. If you moved the entire tree while
8131 preserving its internal organization, then @code{set substitute-path}
8132 allows you to direct the debugger to all the sources with one single
8135 @code{set substitute-path} is also more than just a shortcut command.
8136 The source path is only used if the file at the original location no
8137 longer exists. On the other hand, @code{set substitute-path} modifies
8138 the debugger behavior to look at the rewritten location instead. So, if
8139 for any reason a source file that is not relevant to your executable is
8140 located at the original location, a substitution rule is the only
8141 method available to point @value{GDBN} at the new location.
8143 @cindex @samp{--with-relocated-sources}
8144 @cindex default source path substitution
8145 You can configure a default source path substitution rule by
8146 configuring @value{GDBN} with the
8147 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8148 should be the name of a directory under @value{GDBN}'s configured
8149 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8150 directory names in debug information under @var{dir} will be adjusted
8151 automatically if the installed @value{GDBN} is moved to a new
8152 location. This is useful if @value{GDBN}, libraries or executables
8153 with debug information and corresponding source code are being moved
8157 @item directory @var{dirname} @dots{}
8158 @item dir @var{dirname} @dots{}
8159 Add directory @var{dirname} to the front of the source path. Several
8160 directory names may be given to this command, separated by @samp{:}
8161 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8162 part of absolute file names) or
8163 whitespace. You may specify a directory that is already in the source
8164 path; this moves it forward, so @value{GDBN} searches it sooner.
8168 @vindex $cdir@r{, convenience variable}
8169 @vindex $cwd@r{, convenience variable}
8170 @cindex compilation directory
8171 @cindex current directory
8172 @cindex working directory
8173 @cindex directory, current
8174 @cindex directory, compilation
8175 You can use the string @samp{$cdir} to refer to the compilation
8176 directory (if one is recorded), and @samp{$cwd} to refer to the current
8177 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8178 tracks the current working directory as it changes during your @value{GDBN}
8179 session, while the latter is immediately expanded to the current
8180 directory at the time you add an entry to the source path.
8183 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8185 @c RET-repeat for @code{directory} is explicitly disabled, but since
8186 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8188 @item set directories @var{path-list}
8189 @kindex set directories
8190 Set the source path to @var{path-list}.
8191 @samp{$cdir:$cwd} are added if missing.
8193 @item show directories
8194 @kindex show directories
8195 Print the source path: show which directories it contains.
8197 @anchor{set substitute-path}
8198 @item set substitute-path @var{from} @var{to}
8199 @kindex set substitute-path
8200 Define a source path substitution rule, and add it at the end of the
8201 current list of existing substitution rules. If a rule with the same
8202 @var{from} was already defined, then the old rule is also deleted.
8204 For example, if the file @file{/foo/bar/baz.c} was moved to
8205 @file{/mnt/cross/baz.c}, then the command
8208 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8212 will tell @value{GDBN} to replace @samp{/foo/bar} with
8213 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8214 @file{baz.c} even though it was moved.
8216 In the case when more than one substitution rule have been defined,
8217 the rules are evaluated one by one in the order where they have been
8218 defined. The first one matching, if any, is selected to perform
8221 For instance, if we had entered the following commands:
8224 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8225 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8229 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8230 @file{/mnt/include/defs.h} by using the first rule. However, it would
8231 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8232 @file{/mnt/src/lib/foo.c}.
8235 @item unset substitute-path [path]
8236 @kindex unset substitute-path
8237 If a path is specified, search the current list of substitution rules
8238 for a rule that would rewrite that path. Delete that rule if found.
8239 A warning is emitted by the debugger if no rule could be found.
8241 If no path is specified, then all substitution rules are deleted.
8243 @item show substitute-path [path]
8244 @kindex show substitute-path
8245 If a path is specified, then print the source path substitution rule
8246 which would rewrite that path, if any.
8248 If no path is specified, then print all existing source path substitution
8253 If your source path is cluttered with directories that are no longer of
8254 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8255 versions of source. You can correct the situation as follows:
8259 Use @code{directory} with no argument to reset the source path to its default value.
8262 Use @code{directory} with suitable arguments to reinstall the
8263 directories you want in the source path. You can add all the
8264 directories in one command.
8268 @section Source and Machine Code
8269 @cindex source line and its code address
8271 You can use the command @code{info line} to map source lines to program
8272 addresses (and vice versa), and the command @code{disassemble} to display
8273 a range of addresses as machine instructions. You can use the command
8274 @code{set disassemble-next-line} to set whether to disassemble next
8275 source line when execution stops. When run under @sc{gnu} Emacs
8276 mode, the @code{info line} command causes the arrow to point to the
8277 line specified. Also, @code{info line} prints addresses in symbolic form as
8282 @item info line @var{location}
8283 Print the starting and ending addresses of the compiled code for
8284 source line @var{location}. You can specify source lines in any of
8285 the ways documented in @ref{Specify Location}.
8288 For example, we can use @code{info line} to discover the location of
8289 the object code for the first line of function
8290 @code{m4_changequote}:
8292 @c FIXME: I think this example should also show the addresses in
8293 @c symbolic form, as they usually would be displayed.
8295 (@value{GDBP}) info line m4_changequote
8296 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8300 @cindex code address and its source line
8301 We can also inquire (using @code{*@var{addr}} as the form for
8302 @var{location}) what source line covers a particular address:
8304 (@value{GDBP}) info line *0x63ff
8305 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8308 @cindex @code{$_} and @code{info line}
8309 @cindex @code{x} command, default address
8310 @kindex x@r{(examine), and} info line
8311 After @code{info line}, the default address for the @code{x} command
8312 is changed to the starting address of the line, so that @samp{x/i} is
8313 sufficient to begin examining the machine code (@pxref{Memory,
8314 ,Examining Memory}). Also, this address is saved as the value of the
8315 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8320 @cindex assembly instructions
8321 @cindex instructions, assembly
8322 @cindex machine instructions
8323 @cindex listing machine instructions
8325 @itemx disassemble /m
8326 @itemx disassemble /s
8327 @itemx disassemble /r
8328 This specialized command dumps a range of memory as machine
8329 instructions. It can also print mixed source+disassembly by specifying
8330 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8331 as well as in symbolic form by specifying the @code{/r} modifier.
8332 The default memory range is the function surrounding the
8333 program counter of the selected frame. A single argument to this
8334 command is a program counter value; @value{GDBN} dumps the function
8335 surrounding this value. When two arguments are given, they should
8336 be separated by a comma, possibly surrounded by whitespace. The
8337 arguments specify a range of addresses to dump, in one of two forms:
8340 @item @var{start},@var{end}
8341 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8342 @item @var{start},+@var{length}
8343 the addresses from @var{start} (inclusive) to
8344 @code{@var{start}+@var{length}} (exclusive).
8348 When 2 arguments are specified, the name of the function is also
8349 printed (since there could be several functions in the given range).
8351 The argument(s) can be any expression yielding a numeric value, such as
8352 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8354 If the range of memory being disassembled contains current program counter,
8355 the instruction at that location is shown with a @code{=>} marker.
8358 The following example shows the disassembly of a range of addresses of
8359 HP PA-RISC 2.0 code:
8362 (@value{GDBP}) disas 0x32c4, 0x32e4
8363 Dump of assembler code from 0x32c4 to 0x32e4:
8364 0x32c4 <main+204>: addil 0,dp
8365 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8366 0x32cc <main+212>: ldil 0x3000,r31
8367 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8368 0x32d4 <main+220>: ldo 0(r31),rp
8369 0x32d8 <main+224>: addil -0x800,dp
8370 0x32dc <main+228>: ldo 0x588(r1),r26
8371 0x32e0 <main+232>: ldil 0x3000,r31
8372 End of assembler dump.
8375 Here is an example showing mixed source+assembly for Intel x86
8376 with @code{/m} or @code{/s}, when the program is stopped just after
8377 function prologue in a non-optimized function with no inline code.
8380 (@value{GDBP}) disas /m main
8381 Dump of assembler code for function main:
8383 0x08048330 <+0>: push %ebp
8384 0x08048331 <+1>: mov %esp,%ebp
8385 0x08048333 <+3>: sub $0x8,%esp
8386 0x08048336 <+6>: and $0xfffffff0,%esp
8387 0x08048339 <+9>: sub $0x10,%esp
8389 6 printf ("Hello.\n");
8390 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8391 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8395 0x08048348 <+24>: mov $0x0,%eax
8396 0x0804834d <+29>: leave
8397 0x0804834e <+30>: ret
8399 End of assembler dump.
8402 The @code{/m} option is deprecated as its output is not useful when
8403 there is either inlined code or re-ordered code.
8404 The @code{/s} option is the preferred choice.
8405 Here is an example for AMD x86-64 showing the difference between
8406 @code{/m} output and @code{/s} output.
8407 This example has one inline function defined in a header file,
8408 and the code is compiled with @samp{-O2} optimization.
8409 Note how the @code{/m} output is missing the disassembly of
8410 several instructions that are present in the @code{/s} output.
8440 (@value{GDBP}) disas /m main
8441 Dump of assembler code for function main:
8445 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8446 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8450 0x000000000040041d <+29>: xor %eax,%eax
8451 0x000000000040041f <+31>: retq
8452 0x0000000000400420 <+32>: add %eax,%eax
8453 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8455 End of assembler dump.
8456 (@value{GDBP}) disas /s main
8457 Dump of assembler code for function main:
8461 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8465 0x0000000000400406 <+6>: test %eax,%eax
8466 0x0000000000400408 <+8>: js 0x400420 <main+32>
8471 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8472 0x000000000040040d <+13>: test %eax,%eax
8473 0x000000000040040f <+15>: mov $0x1,%eax
8474 0x0000000000400414 <+20>: cmovne %edx,%eax
8478 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8482 0x000000000040041d <+29>: xor %eax,%eax
8483 0x000000000040041f <+31>: retq
8487 0x0000000000400420 <+32>: add %eax,%eax
8488 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8489 End of assembler dump.
8492 Here is another example showing raw instructions in hex for AMD x86-64,
8495 (gdb) disas /r 0x400281,+10
8496 Dump of assembler code from 0x400281 to 0x40028b:
8497 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8498 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8499 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8500 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8501 End of assembler dump.
8504 Addresses cannot be specified as a location (@pxref{Specify Location}).
8505 So, for example, if you want to disassemble function @code{bar}
8506 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8507 and not @samp{disassemble foo.c:bar}.
8509 Some architectures have more than one commonly-used set of instruction
8510 mnemonics or other syntax.
8512 For programs that were dynamically linked and use shared libraries,
8513 instructions that call functions or branch to locations in the shared
8514 libraries might show a seemingly bogus location---it's actually a
8515 location of the relocation table. On some architectures, @value{GDBN}
8516 might be able to resolve these to actual function names.
8519 @kindex set disassembly-flavor
8520 @cindex Intel disassembly flavor
8521 @cindex AT&T disassembly flavor
8522 @item set disassembly-flavor @var{instruction-set}
8523 Select the instruction set to use when disassembling the
8524 program via the @code{disassemble} or @code{x/i} commands.
8526 Currently this command is only defined for the Intel x86 family. You
8527 can set @var{instruction-set} to either @code{intel} or @code{att}.
8528 The default is @code{att}, the AT&T flavor used by default by Unix
8529 assemblers for x86-based targets.
8531 @kindex show disassembly-flavor
8532 @item show disassembly-flavor
8533 Show the current setting of the disassembly flavor.
8537 @kindex set disassemble-next-line
8538 @kindex show disassemble-next-line
8539 @item set disassemble-next-line
8540 @itemx show disassemble-next-line
8541 Control whether or not @value{GDBN} will disassemble the next source
8542 line or instruction when execution stops. If ON, @value{GDBN} will
8543 display disassembly of the next source line when execution of the
8544 program being debugged stops. This is @emph{in addition} to
8545 displaying the source line itself, which @value{GDBN} always does if
8546 possible. If the next source line cannot be displayed for some reason
8547 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8548 info in the debug info), @value{GDBN} will display disassembly of the
8549 next @emph{instruction} instead of showing the next source line. If
8550 AUTO, @value{GDBN} will display disassembly of next instruction only
8551 if the source line cannot be displayed. This setting causes
8552 @value{GDBN} to display some feedback when you step through a function
8553 with no line info or whose source file is unavailable. The default is
8554 OFF, which means never display the disassembly of the next line or
8560 @chapter Examining Data
8562 @cindex printing data
8563 @cindex examining data
8566 The usual way to examine data in your program is with the @code{print}
8567 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8568 evaluates and prints the value of an expression of the language your
8569 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8570 Different Languages}). It may also print the expression using a
8571 Python-based pretty-printer (@pxref{Pretty Printing}).
8574 @item print @var{expr}
8575 @itemx print /@var{f} @var{expr}
8576 @var{expr} is an expression (in the source language). By default the
8577 value of @var{expr} is printed in a format appropriate to its data type;
8578 you can choose a different format by specifying @samp{/@var{f}}, where
8579 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8583 @itemx print /@var{f}
8584 @cindex reprint the last value
8585 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8586 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8587 conveniently inspect the same value in an alternative format.
8590 A more low-level way of examining data is with the @code{x} command.
8591 It examines data in memory at a specified address and prints it in a
8592 specified format. @xref{Memory, ,Examining Memory}.
8594 If you are interested in information about types, or about how the
8595 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8596 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8599 @cindex exploring hierarchical data structures
8601 Another way of examining values of expressions and type information is
8602 through the Python extension command @code{explore} (available only if
8603 the @value{GDBN} build is configured with @code{--with-python}). It
8604 offers an interactive way to start at the highest level (or, the most
8605 abstract level) of the data type of an expression (or, the data type
8606 itself) and explore all the way down to leaf scalar values/fields
8607 embedded in the higher level data types.
8610 @item explore @var{arg}
8611 @var{arg} is either an expression (in the source language), or a type
8612 visible in the current context of the program being debugged.
8615 The working of the @code{explore} command can be illustrated with an
8616 example. If a data type @code{struct ComplexStruct} is defined in your
8626 struct ComplexStruct
8628 struct SimpleStruct *ss_p;
8634 followed by variable declarations as
8637 struct SimpleStruct ss = @{ 10, 1.11 @};
8638 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8642 then, the value of the variable @code{cs} can be explored using the
8643 @code{explore} command as follows.
8647 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8648 the following fields:
8650 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8651 arr = <Enter 1 to explore this field of type `int [10]'>
8653 Enter the field number of choice:
8657 Since the fields of @code{cs} are not scalar values, you are being
8658 prompted to chose the field you want to explore. Let's say you choose
8659 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8660 pointer, you will be asked if it is pointing to a single value. From
8661 the declaration of @code{cs} above, it is indeed pointing to a single
8662 value, hence you enter @code{y}. If you enter @code{n}, then you will
8663 be asked if it were pointing to an array of values, in which case this
8664 field will be explored as if it were an array.
8667 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8668 Continue exploring it as a pointer to a single value [y/n]: y
8669 The value of `*(cs.ss_p)' is a struct/class of type `struct
8670 SimpleStruct' with the following fields:
8672 i = 10 .. (Value of type `int')
8673 d = 1.1100000000000001 .. (Value of type `double')
8675 Press enter to return to parent value:
8679 If the field @code{arr} of @code{cs} was chosen for exploration by
8680 entering @code{1} earlier, then since it is as array, you will be
8681 prompted to enter the index of the element in the array that you want
8685 `cs.arr' is an array of `int'.
8686 Enter the index of the element you want to explore in `cs.arr': 5
8688 `(cs.arr)[5]' is a scalar value of type `int'.
8692 Press enter to return to parent value:
8695 In general, at any stage of exploration, you can go deeper towards the
8696 leaf values by responding to the prompts appropriately, or hit the
8697 return key to return to the enclosing data structure (the @i{higher}
8698 level data structure).
8700 Similar to exploring values, you can use the @code{explore} command to
8701 explore types. Instead of specifying a value (which is typically a
8702 variable name or an expression valid in the current context of the
8703 program being debugged), you specify a type name. If you consider the
8704 same example as above, your can explore the type
8705 @code{struct ComplexStruct} by passing the argument
8706 @code{struct ComplexStruct} to the @code{explore} command.
8709 (gdb) explore struct ComplexStruct
8713 By responding to the prompts appropriately in the subsequent interactive
8714 session, you can explore the type @code{struct ComplexStruct} in a
8715 manner similar to how the value @code{cs} was explored in the above
8718 The @code{explore} command also has two sub-commands,
8719 @code{explore value} and @code{explore type}. The former sub-command is
8720 a way to explicitly specify that value exploration of the argument is
8721 being invoked, while the latter is a way to explicitly specify that type
8722 exploration of the argument is being invoked.
8725 @item explore value @var{expr}
8726 @cindex explore value
8727 This sub-command of @code{explore} explores the value of the
8728 expression @var{expr} (if @var{expr} is an expression valid in the
8729 current context of the program being debugged). The behavior of this
8730 command is identical to that of the behavior of the @code{explore}
8731 command being passed the argument @var{expr}.
8733 @item explore type @var{arg}
8734 @cindex explore type
8735 This sub-command of @code{explore} explores the type of @var{arg} (if
8736 @var{arg} is a type visible in the current context of program being
8737 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8738 is an expression valid in the current context of the program being
8739 debugged). If @var{arg} is a type, then the behavior of this command is
8740 identical to that of the @code{explore} command being passed the
8741 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8742 this command will be identical to that of the @code{explore} command
8743 being passed the type of @var{arg} as the argument.
8747 * Expressions:: Expressions
8748 * Ambiguous Expressions:: Ambiguous Expressions
8749 * Variables:: Program variables
8750 * Arrays:: Artificial arrays
8751 * Output Formats:: Output formats
8752 * Memory:: Examining memory
8753 * Auto Display:: Automatic display
8754 * Print Settings:: Print settings
8755 * Pretty Printing:: Python pretty printing
8756 * Value History:: Value history
8757 * Convenience Vars:: Convenience variables
8758 * Convenience Funs:: Convenience functions
8759 * Registers:: Registers
8760 * Floating Point Hardware:: Floating point hardware
8761 * Vector Unit:: Vector Unit
8762 * OS Information:: Auxiliary data provided by operating system
8763 * Memory Region Attributes:: Memory region attributes
8764 * Dump/Restore Files:: Copy between memory and a file
8765 * Core File Generation:: Cause a program dump its core
8766 * Character Sets:: Debugging programs that use a different
8767 character set than GDB does
8768 * Caching Target Data:: Data caching for targets
8769 * Searching Memory:: Searching memory for a sequence of bytes
8770 * Value Sizes:: Managing memory allocated for values
8774 @section Expressions
8777 @code{print} and many other @value{GDBN} commands accept an expression and
8778 compute its value. Any kind of constant, variable or operator defined
8779 by the programming language you are using is valid in an expression in
8780 @value{GDBN}. This includes conditional expressions, function calls,
8781 casts, and string constants. It also includes preprocessor macros, if
8782 you compiled your program to include this information; see
8785 @cindex arrays in expressions
8786 @value{GDBN} supports array constants in expressions input by
8787 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8788 you can use the command @code{print @{1, 2, 3@}} to create an array
8789 of three integers. If you pass an array to a function or assign it
8790 to a program variable, @value{GDBN} copies the array to memory that
8791 is @code{malloc}ed in the target program.
8793 Because C is so widespread, most of the expressions shown in examples in
8794 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8795 Languages}, for information on how to use expressions in other
8798 In this section, we discuss operators that you can use in @value{GDBN}
8799 expressions regardless of your programming language.
8801 @cindex casts, in expressions
8802 Casts are supported in all languages, not just in C, because it is so
8803 useful to cast a number into a pointer in order to examine a structure
8804 at that address in memory.
8805 @c FIXME: casts supported---Mod2 true?
8807 @value{GDBN} supports these operators, in addition to those common
8808 to programming languages:
8812 @samp{@@} is a binary operator for treating parts of memory as arrays.
8813 @xref{Arrays, ,Artificial Arrays}, for more information.
8816 @samp{::} allows you to specify a variable in terms of the file or
8817 function where it is defined. @xref{Variables, ,Program Variables}.
8819 @cindex @{@var{type}@}
8820 @cindex type casting memory
8821 @cindex memory, viewing as typed object
8822 @cindex casts, to view memory
8823 @item @{@var{type}@} @var{addr}
8824 Refers to an object of type @var{type} stored at address @var{addr} in
8825 memory. The address @var{addr} may be any expression whose value is
8826 an integer or pointer (but parentheses are required around binary
8827 operators, just as in a cast). This construct is allowed regardless
8828 of what kind of data is normally supposed to reside at @var{addr}.
8831 @node Ambiguous Expressions
8832 @section Ambiguous Expressions
8833 @cindex ambiguous expressions
8835 Expressions can sometimes contain some ambiguous elements. For instance,
8836 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8837 a single function name to be defined several times, for application in
8838 different contexts. This is called @dfn{overloading}. Another example
8839 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8840 templates and is typically instantiated several times, resulting in
8841 the same function name being defined in different contexts.
8843 In some cases and depending on the language, it is possible to adjust
8844 the expression to remove the ambiguity. For instance in C@t{++}, you
8845 can specify the signature of the function you want to break on, as in
8846 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8847 qualified name of your function often makes the expression unambiguous
8850 When an ambiguity that needs to be resolved is detected, the debugger
8851 has the capability to display a menu of numbered choices for each
8852 possibility, and then waits for the selection with the prompt @samp{>}.
8853 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8854 aborts the current command. If the command in which the expression was
8855 used allows more than one choice to be selected, the next option in the
8856 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8859 For example, the following session excerpt shows an attempt to set a
8860 breakpoint at the overloaded symbol @code{String::after}.
8861 We choose three particular definitions of that function name:
8863 @c FIXME! This is likely to change to show arg type lists, at least
8866 (@value{GDBP}) b String::after
8869 [2] file:String.cc; line number:867
8870 [3] file:String.cc; line number:860
8871 [4] file:String.cc; line number:875
8872 [5] file:String.cc; line number:853
8873 [6] file:String.cc; line number:846
8874 [7] file:String.cc; line number:735
8876 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8877 Breakpoint 2 at 0xb344: file String.cc, line 875.
8878 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8879 Multiple breakpoints were set.
8880 Use the "delete" command to delete unwanted
8887 @kindex set multiple-symbols
8888 @item set multiple-symbols @var{mode}
8889 @cindex multiple-symbols menu
8891 This option allows you to adjust the debugger behavior when an expression
8894 By default, @var{mode} is set to @code{all}. If the command with which
8895 the expression is used allows more than one choice, then @value{GDBN}
8896 automatically selects all possible choices. For instance, inserting
8897 a breakpoint on a function using an ambiguous name results in a breakpoint
8898 inserted on each possible match. However, if a unique choice must be made,
8899 then @value{GDBN} uses the menu to help you disambiguate the expression.
8900 For instance, printing the address of an overloaded function will result
8901 in the use of the menu.
8903 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8904 when an ambiguity is detected.
8906 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8907 an error due to the ambiguity and the command is aborted.
8909 @kindex show multiple-symbols
8910 @item show multiple-symbols
8911 Show the current value of the @code{multiple-symbols} setting.
8915 @section Program Variables
8917 The most common kind of expression to use is the name of a variable
8920 Variables in expressions are understood in the selected stack frame
8921 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8925 global (or file-static)
8932 visible according to the scope rules of the
8933 programming language from the point of execution in that frame
8936 @noindent This means that in the function
8951 you can examine and use the variable @code{a} whenever your program is
8952 executing within the function @code{foo}, but you can only use or
8953 examine the variable @code{b} while your program is executing inside
8954 the block where @code{b} is declared.
8956 @cindex variable name conflict
8957 There is an exception: you can refer to a variable or function whose
8958 scope is a single source file even if the current execution point is not
8959 in this file. But it is possible to have more than one such variable or
8960 function with the same name (in different source files). If that
8961 happens, referring to that name has unpredictable effects. If you wish,
8962 you can specify a static variable in a particular function or file by
8963 using the colon-colon (@code{::}) notation:
8965 @cindex colon-colon, context for variables/functions
8967 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8968 @cindex @code{::}, context for variables/functions
8971 @var{file}::@var{variable}
8972 @var{function}::@var{variable}
8976 Here @var{file} or @var{function} is the name of the context for the
8977 static @var{variable}. In the case of file names, you can use quotes to
8978 make sure @value{GDBN} parses the file name as a single word---for example,
8979 to print a global value of @code{x} defined in @file{f2.c}:
8982 (@value{GDBP}) p 'f2.c'::x
8985 The @code{::} notation is normally used for referring to
8986 static variables, since you typically disambiguate uses of local variables
8987 in functions by selecting the appropriate frame and using the
8988 simple name of the variable. However, you may also use this notation
8989 to refer to local variables in frames enclosing the selected frame:
8998 process (a); /* Stop here */
9009 For example, if there is a breakpoint at the commented line,
9010 here is what you might see
9011 when the program stops after executing the call @code{bar(0)}:
9016 (@value{GDBP}) p bar::a
9019 #2 0x080483d0 in foo (a=5) at foobar.c:12
9022 (@value{GDBP}) p bar::a
9026 @cindex C@t{++} scope resolution
9027 These uses of @samp{::} are very rarely in conflict with the very
9028 similar use of the same notation in C@t{++}. When they are in
9029 conflict, the C@t{++} meaning takes precedence; however, this can be
9030 overridden by quoting the file or function name with single quotes.
9032 For example, suppose the program is stopped in a method of a class
9033 that has a field named @code{includefile}, and there is also an
9034 include file named @file{includefile} that defines a variable,
9038 (@value{GDBP}) p includefile
9040 (@value{GDBP}) p includefile::some_global
9041 A syntax error in expression, near `'.
9042 (@value{GDBP}) p 'includefile'::some_global
9046 @cindex wrong values
9047 @cindex variable values, wrong
9048 @cindex function entry/exit, wrong values of variables
9049 @cindex optimized code, wrong values of variables
9051 @emph{Warning:} Occasionally, a local variable may appear to have the
9052 wrong value at certain points in a function---just after entry to a new
9053 scope, and just before exit.
9055 You may see this problem when you are stepping by machine instructions.
9056 This is because, on most machines, it takes more than one instruction to
9057 set up a stack frame (including local variable definitions); if you are
9058 stepping by machine instructions, variables may appear to have the wrong
9059 values until the stack frame is completely built. On exit, it usually
9060 also takes more than one machine instruction to destroy a stack frame;
9061 after you begin stepping through that group of instructions, local
9062 variable definitions may be gone.
9064 This may also happen when the compiler does significant optimizations.
9065 To be sure of always seeing accurate values, turn off all optimization
9068 @cindex ``No symbol "foo" in current context''
9069 Another possible effect of compiler optimizations is to optimize
9070 unused variables out of existence, or assign variables to registers (as
9071 opposed to memory addresses). Depending on the support for such cases
9072 offered by the debug info format used by the compiler, @value{GDBN}
9073 might not be able to display values for such local variables. If that
9074 happens, @value{GDBN} will print a message like this:
9077 No symbol "foo" in current context.
9080 To solve such problems, either recompile without optimizations, or use a
9081 different debug info format, if the compiler supports several such
9082 formats. @xref{Compilation}, for more information on choosing compiler
9083 options. @xref{C, ,C and C@t{++}}, for more information about debug
9084 info formats that are best suited to C@t{++} programs.
9086 If you ask to print an object whose contents are unknown to
9087 @value{GDBN}, e.g., because its data type is not completely specified
9088 by the debug information, @value{GDBN} will say @samp{<incomplete
9089 type>}. @xref{Symbols, incomplete type}, for more about this.
9091 If you append @kbd{@@entry} string to a function parameter name you get its
9092 value at the time the function got called. If the value is not available an
9093 error message is printed. Entry values are available only with some compilers.
9094 Entry values are normally also printed at the function parameter list according
9095 to @ref{set print entry-values}.
9098 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9104 (gdb) print i@@entry
9108 Strings are identified as arrays of @code{char} values without specified
9109 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9110 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9111 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9112 defines literal string type @code{"char"} as @code{char} without a sign.
9117 signed char var1[] = "A";
9120 You get during debugging
9125 $2 = @{65 'A', 0 '\0'@}
9129 @section Artificial Arrays
9131 @cindex artificial array
9133 @kindex @@@r{, referencing memory as an array}
9134 It is often useful to print out several successive objects of the
9135 same type in memory; a section of an array, or an array of
9136 dynamically determined size for which only a pointer exists in the
9139 You can do this by referring to a contiguous span of memory as an
9140 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9141 operand of @samp{@@} should be the first element of the desired array
9142 and be an individual object. The right operand should be the desired length
9143 of the array. The result is an array value whose elements are all of
9144 the type of the left argument. The first element is actually the left
9145 argument; the second element comes from bytes of memory immediately
9146 following those that hold the first element, and so on. Here is an
9147 example. If a program says
9150 int *array = (int *) malloc (len * sizeof (int));
9154 you can print the contents of @code{array} with
9160 The left operand of @samp{@@} must reside in memory. Array values made
9161 with @samp{@@} in this way behave just like other arrays in terms of
9162 subscripting, and are coerced to pointers when used in expressions.
9163 Artificial arrays most often appear in expressions via the value history
9164 (@pxref{Value History, ,Value History}), after printing one out.
9166 Another way to create an artificial array is to use a cast.
9167 This re-interprets a value as if it were an array.
9168 The value need not be in memory:
9170 (@value{GDBP}) p/x (short[2])0x12345678
9171 $1 = @{0x1234, 0x5678@}
9174 As a convenience, if you leave the array length out (as in
9175 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9176 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9178 (@value{GDBP}) p/x (short[])0x12345678
9179 $2 = @{0x1234, 0x5678@}
9182 Sometimes the artificial array mechanism is not quite enough; in
9183 moderately complex data structures, the elements of interest may not
9184 actually be adjacent---for example, if you are interested in the values
9185 of pointers in an array. One useful work-around in this situation is
9186 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9187 Variables}) as a counter in an expression that prints the first
9188 interesting value, and then repeat that expression via @key{RET}. For
9189 instance, suppose you have an array @code{dtab} of pointers to
9190 structures, and you are interested in the values of a field @code{fv}
9191 in each structure. Here is an example of what you might type:
9201 @node Output Formats
9202 @section Output Formats
9204 @cindex formatted output
9205 @cindex output formats
9206 By default, @value{GDBN} prints a value according to its data type. Sometimes
9207 this is not what you want. For example, you might want to print a number
9208 in hex, or a pointer in decimal. Or you might want to view data in memory
9209 at a certain address as a character string or as an instruction. To do
9210 these things, specify an @dfn{output format} when you print a value.
9212 The simplest use of output formats is to say how to print a value
9213 already computed. This is done by starting the arguments of the
9214 @code{print} command with a slash and a format letter. The format
9215 letters supported are:
9219 Regard the bits of the value as an integer, and print the integer in
9223 Print as integer in signed decimal.
9226 Print as integer in unsigned decimal.
9229 Print as integer in octal.
9232 Print as integer in binary. The letter @samp{t} stands for ``two''.
9233 @footnote{@samp{b} cannot be used because these format letters are also
9234 used with the @code{x} command, where @samp{b} stands for ``byte'';
9235 see @ref{Memory,,Examining Memory}.}
9238 @cindex unknown address, locating
9239 @cindex locate address
9240 Print as an address, both absolute in hexadecimal and as an offset from
9241 the nearest preceding symbol. You can use this format used to discover
9242 where (in what function) an unknown address is located:
9245 (@value{GDBP}) p/a 0x54320
9246 $3 = 0x54320 <_initialize_vx+396>
9250 The command @code{info symbol 0x54320} yields similar results.
9251 @xref{Symbols, info symbol}.
9254 Regard as an integer and print it as a character constant. This
9255 prints both the numerical value and its character representation. The
9256 character representation is replaced with the octal escape @samp{\nnn}
9257 for characters outside the 7-bit @sc{ascii} range.
9259 Without this format, @value{GDBN} displays @code{char},
9260 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9261 constants. Single-byte members of vectors are displayed as integer
9265 Regard the bits of the value as a floating point number and print
9266 using typical floating point syntax.
9269 @cindex printing strings
9270 @cindex printing byte arrays
9271 Regard as a string, if possible. With this format, pointers to single-byte
9272 data are displayed as null-terminated strings and arrays of single-byte data
9273 are displayed as fixed-length strings. Other values are displayed in their
9276 Without this format, @value{GDBN} displays pointers to and arrays of
9277 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9278 strings. Single-byte members of a vector are displayed as an integer
9282 Like @samp{x} formatting, the value is treated as an integer and
9283 printed as hexadecimal, but leading zeros are printed to pad the value
9284 to the size of the integer type.
9287 @cindex raw printing
9288 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9289 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9290 Printing}). This typically results in a higher-level display of the
9291 value's contents. The @samp{r} format bypasses any Python
9292 pretty-printer which might exist.
9295 For example, to print the program counter in hex (@pxref{Registers}), type
9302 Note that no space is required before the slash; this is because command
9303 names in @value{GDBN} cannot contain a slash.
9305 To reprint the last value in the value history with a different format,
9306 you can use the @code{print} command with just a format and no
9307 expression. For example, @samp{p/x} reprints the last value in hex.
9310 @section Examining Memory
9312 You can use the command @code{x} (for ``examine'') to examine memory in
9313 any of several formats, independently of your program's data types.
9315 @cindex examining memory
9317 @kindex x @r{(examine memory)}
9318 @item x/@var{nfu} @var{addr}
9321 Use the @code{x} command to examine memory.
9324 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9325 much memory to display and how to format it; @var{addr} is an
9326 expression giving the address where you want to start displaying memory.
9327 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9328 Several commands set convenient defaults for @var{addr}.
9331 @item @var{n}, the repeat count
9332 The repeat count is a decimal integer; the default is 1. It specifies
9333 how much memory (counting by units @var{u}) to display. If a negative
9334 number is specified, memory is examined backward from @var{addr}.
9335 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9338 @item @var{f}, the display format
9339 The display format is one of the formats used by @code{print}
9340 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9341 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9342 The default is @samp{x} (hexadecimal) initially. The default changes
9343 each time you use either @code{x} or @code{print}.
9345 @item @var{u}, the unit size
9346 The unit size is any of
9352 Halfwords (two bytes).
9354 Words (four bytes). This is the initial default.
9356 Giant words (eight bytes).
9359 Each time you specify a unit size with @code{x}, that size becomes the
9360 default unit the next time you use @code{x}. For the @samp{i} format,
9361 the unit size is ignored and is normally not written. For the @samp{s} format,
9362 the unit size defaults to @samp{b}, unless it is explicitly given.
9363 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9364 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9365 Note that the results depend on the programming language of the
9366 current compilation unit. If the language is C, the @samp{s}
9367 modifier will use the UTF-16 encoding while @samp{w} will use
9368 UTF-32. The encoding is set by the programming language and cannot
9371 @item @var{addr}, starting display address
9372 @var{addr} is the address where you want @value{GDBN} to begin displaying
9373 memory. The expression need not have a pointer value (though it may);
9374 it is always interpreted as an integer address of a byte of memory.
9375 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9376 @var{addr} is usually just after the last address examined---but several
9377 other commands also set the default address: @code{info breakpoints} (to
9378 the address of the last breakpoint listed), @code{info line} (to the
9379 starting address of a line), and @code{print} (if you use it to display
9380 a value from memory).
9383 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9384 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9385 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9386 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9387 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9389 You can also specify a negative repeat count to examine memory backward
9390 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9391 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9393 Since the letters indicating unit sizes are all distinct from the
9394 letters specifying output formats, you do not have to remember whether
9395 unit size or format comes first; either order works. The output
9396 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9397 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9399 Even though the unit size @var{u} is ignored for the formats @samp{s}
9400 and @samp{i}, you might still want to use a count @var{n}; for example,
9401 @samp{3i} specifies that you want to see three machine instructions,
9402 including any operands. For convenience, especially when used with
9403 the @code{display} command, the @samp{i} format also prints branch delay
9404 slot instructions, if any, beyond the count specified, which immediately
9405 follow the last instruction that is within the count. The command
9406 @code{disassemble} gives an alternative way of inspecting machine
9407 instructions; see @ref{Machine Code,,Source and Machine Code}.
9409 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9410 the command displays null-terminated strings or instructions before the given
9411 address as many as the absolute value of the given number. For the @samp{i}
9412 format, we use line number information in the debug info to accurately locate
9413 instruction boundaries while disassembling backward. If line info is not
9414 available, the command stops examining memory with an error message.
9416 All the defaults for the arguments to @code{x} are designed to make it
9417 easy to continue scanning memory with minimal specifications each time
9418 you use @code{x}. For example, after you have inspected three machine
9419 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9420 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9421 the repeat count @var{n} is used again; the other arguments default as
9422 for successive uses of @code{x}.
9424 When examining machine instructions, the instruction at current program
9425 counter is shown with a @code{=>} marker. For example:
9428 (@value{GDBP}) x/5i $pc-6
9429 0x804837f <main+11>: mov %esp,%ebp
9430 0x8048381 <main+13>: push %ecx
9431 0x8048382 <main+14>: sub $0x4,%esp
9432 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9433 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9436 @cindex @code{$_}, @code{$__}, and value history
9437 The addresses and contents printed by the @code{x} command are not saved
9438 in the value history because there is often too much of them and they
9439 would get in the way. Instead, @value{GDBN} makes these values available for
9440 subsequent use in expressions as values of the convenience variables
9441 @code{$_} and @code{$__}. After an @code{x} command, the last address
9442 examined is available for use in expressions in the convenience variable
9443 @code{$_}. The contents of that address, as examined, are available in
9444 the convenience variable @code{$__}.
9446 If the @code{x} command has a repeat count, the address and contents saved
9447 are from the last memory unit printed; this is not the same as the last
9448 address printed if several units were printed on the last line of output.
9450 @anchor{addressable memory unit}
9451 @cindex addressable memory unit
9452 Most targets have an addressable memory unit size of 8 bits. This means
9453 that to each memory address are associated 8 bits of data. Some
9454 targets, however, have other addressable memory unit sizes.
9455 Within @value{GDBN} and this document, the term
9456 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9457 when explicitly referring to a chunk of data of that size. The word
9458 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9459 the addressable memory unit size of the target. For most systems,
9460 addressable memory unit is a synonym of byte.
9462 @cindex remote memory comparison
9463 @cindex target memory comparison
9464 @cindex verify remote memory image
9465 @cindex verify target memory image
9466 When you are debugging a program running on a remote target machine
9467 (@pxref{Remote Debugging}), you may wish to verify the program's image
9468 in the remote machine's memory against the executable file you
9469 downloaded to the target. Or, on any target, you may want to check
9470 whether the program has corrupted its own read-only sections. The
9471 @code{compare-sections} command is provided for such situations.
9474 @kindex compare-sections
9475 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9476 Compare the data of a loadable section @var{section-name} in the
9477 executable file of the program being debugged with the same section in
9478 the target machine's memory, and report any mismatches. With no
9479 arguments, compares all loadable sections. With an argument of
9480 @code{-r}, compares all loadable read-only sections.
9482 Note: for remote targets, this command can be accelerated if the
9483 target supports computing the CRC checksum of a block of memory
9484 (@pxref{qCRC packet}).
9488 @section Automatic Display
9489 @cindex automatic display
9490 @cindex display of expressions
9492 If you find that you want to print the value of an expression frequently
9493 (to see how it changes), you might want to add it to the @dfn{automatic
9494 display list} so that @value{GDBN} prints its value each time your program stops.
9495 Each expression added to the list is given a number to identify it;
9496 to remove an expression from the list, you specify that number.
9497 The automatic display looks like this:
9501 3: bar[5] = (struct hack *) 0x3804
9505 This display shows item numbers, expressions and their current values. As with
9506 displays you request manually using @code{x} or @code{print}, you can
9507 specify the output format you prefer; in fact, @code{display} decides
9508 whether to use @code{print} or @code{x} depending your format
9509 specification---it uses @code{x} if you specify either the @samp{i}
9510 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9514 @item display @var{expr}
9515 Add the expression @var{expr} to the list of expressions to display
9516 each time your program stops. @xref{Expressions, ,Expressions}.
9518 @code{display} does not repeat if you press @key{RET} again after using it.
9520 @item display/@var{fmt} @var{expr}
9521 For @var{fmt} specifying only a display format and not a size or
9522 count, add the expression @var{expr} to the auto-display list but
9523 arrange to display it each time in the specified format @var{fmt}.
9524 @xref{Output Formats,,Output Formats}.
9526 @item display/@var{fmt} @var{addr}
9527 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9528 number of units, add the expression @var{addr} as a memory address to
9529 be examined each time your program stops. Examining means in effect
9530 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9533 For example, @samp{display/i $pc} can be helpful, to see the machine
9534 instruction about to be executed each time execution stops (@samp{$pc}
9535 is a common name for the program counter; @pxref{Registers, ,Registers}).
9538 @kindex delete display
9540 @item undisplay @var{dnums}@dots{}
9541 @itemx delete display @var{dnums}@dots{}
9542 Remove items from the list of expressions to display. Specify the
9543 numbers of the displays that you want affected with the command
9544 argument @var{dnums}. It can be a single display number, one of the
9545 numbers shown in the first field of the @samp{info display} display;
9546 or it could be a range of display numbers, as in @code{2-4}.
9548 @code{undisplay} does not repeat if you press @key{RET} after using it.
9549 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9551 @kindex disable display
9552 @item disable display @var{dnums}@dots{}
9553 Disable the display of item numbers @var{dnums}. A disabled display
9554 item is not printed automatically, but is not forgotten. It may be
9555 enabled again later. Specify the numbers of the displays that you
9556 want affected with the command argument @var{dnums}. It can be a
9557 single display number, one of the numbers shown in the first field of
9558 the @samp{info display} display; or it could be a range of display
9559 numbers, as in @code{2-4}.
9561 @kindex enable display
9562 @item enable display @var{dnums}@dots{}
9563 Enable display of item numbers @var{dnums}. It becomes effective once
9564 again in auto display of its expression, until you specify otherwise.
9565 Specify the numbers of the displays that you want affected with the
9566 command argument @var{dnums}. It can be a single display number, one
9567 of the numbers shown in the first field of the @samp{info display}
9568 display; or it could be a range of display numbers, as in @code{2-4}.
9571 Display the current values of the expressions on the list, just as is
9572 done when your program stops.
9574 @kindex info display
9576 Print the list of expressions previously set up to display
9577 automatically, each one with its item number, but without showing the
9578 values. This includes disabled expressions, which are marked as such.
9579 It also includes expressions which would not be displayed right now
9580 because they refer to automatic variables not currently available.
9583 @cindex display disabled out of scope
9584 If a display expression refers to local variables, then it does not make
9585 sense outside the lexical context for which it was set up. Such an
9586 expression is disabled when execution enters a context where one of its
9587 variables is not defined. For example, if you give the command
9588 @code{display last_char} while inside a function with an argument
9589 @code{last_char}, @value{GDBN} displays this argument while your program
9590 continues to stop inside that function. When it stops elsewhere---where
9591 there is no variable @code{last_char}---the display is disabled
9592 automatically. The next time your program stops where @code{last_char}
9593 is meaningful, you can enable the display expression once again.
9595 @node Print Settings
9596 @section Print Settings
9598 @cindex format options
9599 @cindex print settings
9600 @value{GDBN} provides the following ways to control how arrays, structures,
9601 and symbols are printed.
9604 These settings are useful for debugging programs in any language:
9608 @item set print address
9609 @itemx set print address on
9610 @cindex print/don't print memory addresses
9611 @value{GDBN} prints memory addresses showing the location of stack
9612 traces, structure values, pointer values, breakpoints, and so forth,
9613 even when it also displays the contents of those addresses. The default
9614 is @code{on}. For example, this is what a stack frame display looks like with
9615 @code{set print address on}:
9620 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9622 530 if (lquote != def_lquote)
9626 @item set print address off
9627 Do not print addresses when displaying their contents. For example,
9628 this is the same stack frame displayed with @code{set print address off}:
9632 (@value{GDBP}) set print addr off
9634 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9635 530 if (lquote != def_lquote)
9639 You can use @samp{set print address off} to eliminate all machine
9640 dependent displays from the @value{GDBN} interface. For example, with
9641 @code{print address off}, you should get the same text for backtraces on
9642 all machines---whether or not they involve pointer arguments.
9645 @item show print address
9646 Show whether or not addresses are to be printed.
9649 When @value{GDBN} prints a symbolic address, it normally prints the
9650 closest earlier symbol plus an offset. If that symbol does not uniquely
9651 identify the address (for example, it is a name whose scope is a single
9652 source file), you may need to clarify. One way to do this is with
9653 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9654 you can set @value{GDBN} to print the source file and line number when
9655 it prints a symbolic address:
9658 @item set print symbol-filename on
9659 @cindex source file and line of a symbol
9660 @cindex symbol, source file and line
9661 Tell @value{GDBN} to print the source file name and line number of a
9662 symbol in the symbolic form of an address.
9664 @item set print symbol-filename off
9665 Do not print source file name and line number of a symbol. This is the
9668 @item show print symbol-filename
9669 Show whether or not @value{GDBN} will print the source file name and
9670 line number of a symbol in the symbolic form of an address.
9673 Another situation where it is helpful to show symbol filenames and line
9674 numbers is when disassembling code; @value{GDBN} shows you the line
9675 number and source file that corresponds to each instruction.
9677 Also, you may wish to see the symbolic form only if the address being
9678 printed is reasonably close to the closest earlier symbol:
9681 @item set print max-symbolic-offset @var{max-offset}
9682 @itemx set print max-symbolic-offset unlimited
9683 @cindex maximum value for offset of closest symbol
9684 Tell @value{GDBN} to only display the symbolic form of an address if the
9685 offset between the closest earlier symbol and the address is less than
9686 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9687 to always print the symbolic form of an address if any symbol precedes
9688 it. Zero is equivalent to @code{unlimited}.
9690 @item show print max-symbolic-offset
9691 Ask how large the maximum offset is that @value{GDBN} prints in a
9695 @cindex wild pointer, interpreting
9696 @cindex pointer, finding referent
9697 If you have a pointer and you are not sure where it points, try
9698 @samp{set print symbol-filename on}. Then you can determine the name
9699 and source file location of the variable where it points, using
9700 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9701 For example, here @value{GDBN} shows that a variable @code{ptt} points
9702 at another variable @code{t}, defined in @file{hi2.c}:
9705 (@value{GDBP}) set print symbol-filename on
9706 (@value{GDBP}) p/a ptt
9707 $4 = 0xe008 <t in hi2.c>
9711 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9712 does not show the symbol name and filename of the referent, even with
9713 the appropriate @code{set print} options turned on.
9716 You can also enable @samp{/a}-like formatting all the time using
9717 @samp{set print symbol on}:
9720 @item set print symbol on
9721 Tell @value{GDBN} to print the symbol corresponding to an address, if
9724 @item set print symbol off
9725 Tell @value{GDBN} not to print the symbol corresponding to an
9726 address. In this mode, @value{GDBN} will still print the symbol
9727 corresponding to pointers to functions. This is the default.
9729 @item show print symbol
9730 Show whether @value{GDBN} will display the symbol corresponding to an
9734 Other settings control how different kinds of objects are printed:
9737 @item set print array
9738 @itemx set print array on
9739 @cindex pretty print arrays
9740 Pretty print arrays. This format is more convenient to read,
9741 but uses more space. The default is off.
9743 @item set print array off
9744 Return to compressed format for arrays.
9746 @item show print array
9747 Show whether compressed or pretty format is selected for displaying
9750 @cindex print array indexes
9751 @item set print array-indexes
9752 @itemx set print array-indexes on
9753 Print the index of each element when displaying arrays. May be more
9754 convenient to locate a given element in the array or quickly find the
9755 index of a given element in that printed array. The default is off.
9757 @item set print array-indexes off
9758 Stop printing element indexes when displaying arrays.
9760 @item show print array-indexes
9761 Show whether the index of each element is printed when displaying
9764 @item set print elements @var{number-of-elements}
9765 @itemx set print elements unlimited
9766 @cindex number of array elements to print
9767 @cindex limit on number of printed array elements
9768 Set a limit on how many elements of an array @value{GDBN} will print.
9769 If @value{GDBN} is printing a large array, it stops printing after it has
9770 printed the number of elements set by the @code{set print elements} command.
9771 This limit also applies to the display of strings.
9772 When @value{GDBN} starts, this limit is set to 200.
9773 Setting @var{number-of-elements} to @code{unlimited} or zero means
9774 that the number of elements to print is unlimited.
9776 @item show print elements
9777 Display the number of elements of a large array that @value{GDBN} will print.
9778 If the number is 0, then the printing is unlimited.
9780 @item set print frame-arguments @var{value}
9781 @kindex set print frame-arguments
9782 @cindex printing frame argument values
9783 @cindex print all frame argument values
9784 @cindex print frame argument values for scalars only
9785 @cindex do not print frame argument values
9786 This command allows to control how the values of arguments are printed
9787 when the debugger prints a frame (@pxref{Frames}). The possible
9792 The values of all arguments are printed.
9795 Print the value of an argument only if it is a scalar. The value of more
9796 complex arguments such as arrays, structures, unions, etc, is replaced
9797 by @code{@dots{}}. This is the default. Here is an example where
9798 only scalar arguments are shown:
9801 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9806 None of the argument values are printed. Instead, the value of each argument
9807 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9810 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9815 By default, only scalar arguments are printed. This command can be used
9816 to configure the debugger to print the value of all arguments, regardless
9817 of their type. However, it is often advantageous to not print the value
9818 of more complex parameters. For instance, it reduces the amount of
9819 information printed in each frame, making the backtrace more readable.
9820 Also, it improves performance when displaying Ada frames, because
9821 the computation of large arguments can sometimes be CPU-intensive,
9822 especially in large applications. Setting @code{print frame-arguments}
9823 to @code{scalars} (the default) or @code{none} avoids this computation,
9824 thus speeding up the display of each Ada frame.
9826 @item show print frame-arguments
9827 Show how the value of arguments should be displayed when printing a frame.
9829 @item set print raw frame-arguments on
9830 Print frame arguments in raw, non pretty-printed, form.
9832 @item set print raw frame-arguments off
9833 Print frame arguments in pretty-printed form, if there is a pretty-printer
9834 for the value (@pxref{Pretty Printing}),
9835 otherwise print the value in raw form.
9836 This is the default.
9838 @item show print raw frame-arguments
9839 Show whether to print frame arguments in raw form.
9841 @anchor{set print entry-values}
9842 @item set print entry-values @var{value}
9843 @kindex set print entry-values
9844 Set printing of frame argument values at function entry. In some cases
9845 @value{GDBN} can determine the value of function argument which was passed by
9846 the function caller, even if the value was modified inside the called function
9847 and therefore is different. With optimized code, the current value could be
9848 unavailable, but the entry value may still be known.
9850 The default value is @code{default} (see below for its description). Older
9851 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9852 this feature will behave in the @code{default} setting the same way as with the
9855 This functionality is currently supported only by DWARF 2 debugging format and
9856 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9857 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9860 The @var{value} parameter can be one of the following:
9864 Print only actual parameter values, never print values from function entry
9868 #0 different (val=6)
9869 #0 lost (val=<optimized out>)
9871 #0 invalid (val=<optimized out>)
9875 Print only parameter values from function entry point. The actual parameter
9876 values are never printed.
9878 #0 equal (val@@entry=5)
9879 #0 different (val@@entry=5)
9880 #0 lost (val@@entry=5)
9881 #0 born (val@@entry=<optimized out>)
9882 #0 invalid (val@@entry=<optimized out>)
9886 Print only parameter values from function entry point. If value from function
9887 entry point is not known while the actual value is known, print the actual
9888 value for such parameter.
9890 #0 equal (val@@entry=5)
9891 #0 different (val@@entry=5)
9892 #0 lost (val@@entry=5)
9894 #0 invalid (val@@entry=<optimized out>)
9898 Print actual parameter values. If actual parameter value is not known while
9899 value from function entry point is known, print the entry point value for such
9903 #0 different (val=6)
9904 #0 lost (val@@entry=5)
9906 #0 invalid (val=<optimized out>)
9910 Always print both the actual parameter value and its value from function entry
9911 point, even if values of one or both are not available due to compiler
9914 #0 equal (val=5, val@@entry=5)
9915 #0 different (val=6, val@@entry=5)
9916 #0 lost (val=<optimized out>, val@@entry=5)
9917 #0 born (val=10, val@@entry=<optimized out>)
9918 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9922 Print the actual parameter value if it is known and also its value from
9923 function entry point if it is known. If neither is known, print for the actual
9924 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9925 values are known and identical, print the shortened
9926 @code{param=param@@entry=VALUE} notation.
9928 #0 equal (val=val@@entry=5)
9929 #0 different (val=6, val@@entry=5)
9930 #0 lost (val@@entry=5)
9932 #0 invalid (val=<optimized out>)
9936 Always print the actual parameter value. Print also its value from function
9937 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9938 if both values are known and identical, print the shortened
9939 @code{param=param@@entry=VALUE} notation.
9941 #0 equal (val=val@@entry=5)
9942 #0 different (val=6, val@@entry=5)
9943 #0 lost (val=<optimized out>, val@@entry=5)
9945 #0 invalid (val=<optimized out>)
9949 For analysis messages on possible failures of frame argument values at function
9950 entry resolution see @ref{set debug entry-values}.
9952 @item show print entry-values
9953 Show the method being used for printing of frame argument values at function
9956 @item set print repeats @var{number-of-repeats}
9957 @itemx set print repeats unlimited
9958 @cindex repeated array elements
9959 Set the threshold for suppressing display of repeated array
9960 elements. When the number of consecutive identical elements of an
9961 array exceeds the threshold, @value{GDBN} prints the string
9962 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9963 identical repetitions, instead of displaying the identical elements
9964 themselves. Setting the threshold to @code{unlimited} or zero will
9965 cause all elements to be individually printed. The default threshold
9968 @item show print repeats
9969 Display the current threshold for printing repeated identical
9972 @item set print null-stop
9973 @cindex @sc{null} elements in arrays
9974 Cause @value{GDBN} to stop printing the characters of an array when the first
9975 @sc{null} is encountered. This is useful when large arrays actually
9976 contain only short strings.
9979 @item show print null-stop
9980 Show whether @value{GDBN} stops printing an array on the first
9981 @sc{null} character.
9983 @item set print pretty on
9984 @cindex print structures in indented form
9985 @cindex indentation in structure display
9986 Cause @value{GDBN} to print structures in an indented format with one member
9987 per line, like this:
10002 @item set print pretty off
10003 Cause @value{GDBN} to print structures in a compact format, like this:
10007 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10008 meat = 0x54 "Pork"@}
10013 This is the default format.
10015 @item show print pretty
10016 Show which format @value{GDBN} is using to print structures.
10018 @item set print sevenbit-strings on
10019 @cindex eight-bit characters in strings
10020 @cindex octal escapes in strings
10021 Print using only seven-bit characters; if this option is set,
10022 @value{GDBN} displays any eight-bit characters (in strings or
10023 character values) using the notation @code{\}@var{nnn}. This setting is
10024 best if you are working in English (@sc{ascii}) and you use the
10025 high-order bit of characters as a marker or ``meta'' bit.
10027 @item set print sevenbit-strings off
10028 Print full eight-bit characters. This allows the use of more
10029 international character sets, and is the default.
10031 @item show print sevenbit-strings
10032 Show whether or not @value{GDBN} is printing only seven-bit characters.
10034 @item set print union on
10035 @cindex unions in structures, printing
10036 Tell @value{GDBN} to print unions which are contained in structures
10037 and other unions. This is the default setting.
10039 @item set print union off
10040 Tell @value{GDBN} not to print unions which are contained in
10041 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10044 @item show print union
10045 Ask @value{GDBN} whether or not it will print unions which are contained in
10046 structures and other unions.
10048 For example, given the declarations
10051 typedef enum @{Tree, Bug@} Species;
10052 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10053 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10064 struct thing foo = @{Tree, @{Acorn@}@};
10068 with @code{set print union on} in effect @samp{p foo} would print
10071 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10075 and with @code{set print union off} in effect it would print
10078 $1 = @{it = Tree, form = @{...@}@}
10082 @code{set print union} affects programs written in C-like languages
10088 These settings are of interest when debugging C@t{++} programs:
10091 @cindex demangling C@t{++} names
10092 @item set print demangle
10093 @itemx set print demangle on
10094 Print C@t{++} names in their source form rather than in the encoded
10095 (``mangled'') form passed to the assembler and linker for type-safe
10096 linkage. The default is on.
10098 @item show print demangle
10099 Show whether C@t{++} names are printed in mangled or demangled form.
10101 @item set print asm-demangle
10102 @itemx set print asm-demangle on
10103 Print C@t{++} names in their source form rather than their mangled form, even
10104 in assembler code printouts such as instruction disassemblies.
10105 The default is off.
10107 @item show print asm-demangle
10108 Show whether C@t{++} names in assembly listings are printed in mangled
10111 @cindex C@t{++} symbol decoding style
10112 @cindex symbol decoding style, C@t{++}
10113 @kindex set demangle-style
10114 @item set demangle-style @var{style}
10115 Choose among several encoding schemes used by different compilers to
10116 represent C@t{++} names. The choices for @var{style} are currently:
10120 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10121 This is the default.
10124 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10127 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10130 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10133 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10134 @strong{Warning:} this setting alone is not sufficient to allow
10135 debugging @code{cfront}-generated executables. @value{GDBN} would
10136 require further enhancement to permit that.
10139 If you omit @var{style}, you will see a list of possible formats.
10141 @item show demangle-style
10142 Display the encoding style currently in use for decoding C@t{++} symbols.
10144 @item set print object
10145 @itemx set print object on
10146 @cindex derived type of an object, printing
10147 @cindex display derived types
10148 When displaying a pointer to an object, identify the @emph{actual}
10149 (derived) type of the object rather than the @emph{declared} type, using
10150 the virtual function table. Note that the virtual function table is
10151 required---this feature can only work for objects that have run-time
10152 type identification; a single virtual method in the object's declared
10153 type is sufficient. Note that this setting is also taken into account when
10154 working with variable objects via MI (@pxref{GDB/MI}).
10156 @item set print object off
10157 Display only the declared type of objects, without reference to the
10158 virtual function table. This is the default setting.
10160 @item show print object
10161 Show whether actual, or declared, object types are displayed.
10163 @item set print static-members
10164 @itemx set print static-members on
10165 @cindex static members of C@t{++} objects
10166 Print static members when displaying a C@t{++} object. The default is on.
10168 @item set print static-members off
10169 Do not print static members when displaying a C@t{++} object.
10171 @item show print static-members
10172 Show whether C@t{++} static members are printed or not.
10174 @item set print pascal_static-members
10175 @itemx set print pascal_static-members on
10176 @cindex static members of Pascal objects
10177 @cindex Pascal objects, static members display
10178 Print static members when displaying a Pascal object. The default is on.
10180 @item set print pascal_static-members off
10181 Do not print static members when displaying a Pascal object.
10183 @item show print pascal_static-members
10184 Show whether Pascal static members are printed or not.
10186 @c These don't work with HP ANSI C++ yet.
10187 @item set print vtbl
10188 @itemx set print vtbl on
10189 @cindex pretty print C@t{++} virtual function tables
10190 @cindex virtual functions (C@t{++}) display
10191 @cindex VTBL display
10192 Pretty print C@t{++} virtual function tables. The default is off.
10193 (The @code{vtbl} commands do not work on programs compiled with the HP
10194 ANSI C@t{++} compiler (@code{aCC}).)
10196 @item set print vtbl off
10197 Do not pretty print C@t{++} virtual function tables.
10199 @item show print vtbl
10200 Show whether C@t{++} virtual function tables are pretty printed, or not.
10203 @node Pretty Printing
10204 @section Pretty Printing
10206 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10207 Python code. It greatly simplifies the display of complex objects. This
10208 mechanism works for both MI and the CLI.
10211 * Pretty-Printer Introduction:: Introduction to pretty-printers
10212 * Pretty-Printer Example:: An example pretty-printer
10213 * Pretty-Printer Commands:: Pretty-printer commands
10216 @node Pretty-Printer Introduction
10217 @subsection Pretty-Printer Introduction
10219 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10220 registered for the value. If there is then @value{GDBN} invokes the
10221 pretty-printer to print the value. Otherwise the value is printed normally.
10223 Pretty-printers are normally named. This makes them easy to manage.
10224 The @samp{info pretty-printer} command will list all the installed
10225 pretty-printers with their names.
10226 If a pretty-printer can handle multiple data types, then its
10227 @dfn{subprinters} are the printers for the individual data types.
10228 Each such subprinter has its own name.
10229 The format of the name is @var{printer-name};@var{subprinter-name}.
10231 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10232 Typically they are automatically loaded and registered when the corresponding
10233 debug information is loaded, thus making them available without having to
10234 do anything special.
10236 There are three places where a pretty-printer can be registered.
10240 Pretty-printers registered globally are available when debugging
10244 Pretty-printers registered with a program space are available only
10245 when debugging that program.
10246 @xref{Progspaces In Python}, for more details on program spaces in Python.
10249 Pretty-printers registered with an objfile are loaded and unloaded
10250 with the corresponding objfile (e.g., shared library).
10251 @xref{Objfiles In Python}, for more details on objfiles in Python.
10254 @xref{Selecting Pretty-Printers}, for further information on how
10255 pretty-printers are selected,
10257 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10260 @node Pretty-Printer Example
10261 @subsection Pretty-Printer Example
10263 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10266 (@value{GDBP}) print s
10268 static npos = 4294967295,
10270 <std::allocator<char>> = @{
10271 <__gnu_cxx::new_allocator<char>> = @{
10272 <No data fields>@}, <No data fields>
10274 members of std::basic_string<char, std::char_traits<char>,
10275 std::allocator<char> >::_Alloc_hider:
10276 _M_p = 0x804a014 "abcd"
10281 With a pretty-printer for @code{std::string} only the contents are printed:
10284 (@value{GDBP}) print s
10288 @node Pretty-Printer Commands
10289 @subsection Pretty-Printer Commands
10290 @cindex pretty-printer commands
10293 @kindex info pretty-printer
10294 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10295 Print the list of installed pretty-printers.
10296 This includes disabled pretty-printers, which are marked as such.
10298 @var{object-regexp} is a regular expression matching the objects
10299 whose pretty-printers to list.
10300 Objects can be @code{global}, the program space's file
10301 (@pxref{Progspaces In Python}),
10302 and the object files within that program space (@pxref{Objfiles In Python}).
10303 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10304 looks up a printer from these three objects.
10306 @var{name-regexp} is a regular expression matching the name of the printers
10309 @kindex disable pretty-printer
10310 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10311 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10312 A disabled pretty-printer is not forgotten, it may be enabled again later.
10314 @kindex enable pretty-printer
10315 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10316 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10321 Suppose we have three pretty-printers installed: one from library1.so
10322 named @code{foo} that prints objects of type @code{foo}, and
10323 another from library2.so named @code{bar} that prints two types of objects,
10324 @code{bar1} and @code{bar2}.
10327 (gdb) info pretty-printer
10334 (gdb) info pretty-printer library2
10339 (gdb) disable pretty-printer library1
10341 2 of 3 printers enabled
10342 (gdb) info pretty-printer
10349 (gdb) disable pretty-printer library2 bar:bar1
10351 1 of 3 printers enabled
10352 (gdb) info pretty-printer library2
10359 (gdb) disable pretty-printer library2 bar
10361 0 of 3 printers enabled
10362 (gdb) info pretty-printer library2
10371 Note that for @code{bar} the entire printer can be disabled,
10372 as can each individual subprinter.
10374 @node Value History
10375 @section Value History
10377 @cindex value history
10378 @cindex history of values printed by @value{GDBN}
10379 Values printed by the @code{print} command are saved in the @value{GDBN}
10380 @dfn{value history}. This allows you to refer to them in other expressions.
10381 Values are kept until the symbol table is re-read or discarded
10382 (for example with the @code{file} or @code{symbol-file} commands).
10383 When the symbol table changes, the value history is discarded,
10384 since the values may contain pointers back to the types defined in the
10389 @cindex history number
10390 The values printed are given @dfn{history numbers} by which you can
10391 refer to them. These are successive integers starting with one.
10392 @code{print} shows you the history number assigned to a value by
10393 printing @samp{$@var{num} = } before the value; here @var{num} is the
10396 To refer to any previous value, use @samp{$} followed by the value's
10397 history number. The way @code{print} labels its output is designed to
10398 remind you of this. Just @code{$} refers to the most recent value in
10399 the history, and @code{$$} refers to the value before that.
10400 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10401 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10402 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10404 For example, suppose you have just printed a pointer to a structure and
10405 want to see the contents of the structure. It suffices to type
10411 If you have a chain of structures where the component @code{next} points
10412 to the next one, you can print the contents of the next one with this:
10419 You can print successive links in the chain by repeating this
10420 command---which you can do by just typing @key{RET}.
10422 Note that the history records values, not expressions. If the value of
10423 @code{x} is 4 and you type these commands:
10431 then the value recorded in the value history by the @code{print} command
10432 remains 4 even though the value of @code{x} has changed.
10435 @kindex show values
10437 Print the last ten values in the value history, with their item numbers.
10438 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10439 values} does not change the history.
10441 @item show values @var{n}
10442 Print ten history values centered on history item number @var{n}.
10444 @item show values +
10445 Print ten history values just after the values last printed. If no more
10446 values are available, @code{show values +} produces no display.
10449 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10450 same effect as @samp{show values +}.
10452 @node Convenience Vars
10453 @section Convenience Variables
10455 @cindex convenience variables
10456 @cindex user-defined variables
10457 @value{GDBN} provides @dfn{convenience variables} that you can use within
10458 @value{GDBN} to hold on to a value and refer to it later. These variables
10459 exist entirely within @value{GDBN}; they are not part of your program, and
10460 setting a convenience variable has no direct effect on further execution
10461 of your program. That is why you can use them freely.
10463 Convenience variables are prefixed with @samp{$}. Any name preceded by
10464 @samp{$} can be used for a convenience variable, unless it is one of
10465 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10466 (Value history references, in contrast, are @emph{numbers} preceded
10467 by @samp{$}. @xref{Value History, ,Value History}.)
10469 You can save a value in a convenience variable with an assignment
10470 expression, just as you would set a variable in your program.
10474 set $foo = *object_ptr
10478 would save in @code{$foo} the value contained in the object pointed to by
10481 Using a convenience variable for the first time creates it, but its
10482 value is @code{void} until you assign a new value. You can alter the
10483 value with another assignment at any time.
10485 Convenience variables have no fixed types. You can assign a convenience
10486 variable any type of value, including structures and arrays, even if
10487 that variable already has a value of a different type. The convenience
10488 variable, when used as an expression, has the type of its current value.
10491 @kindex show convenience
10492 @cindex show all user variables and functions
10493 @item show convenience
10494 Print a list of convenience variables used so far, and their values,
10495 as well as a list of the convenience functions.
10496 Abbreviated @code{show conv}.
10498 @kindex init-if-undefined
10499 @cindex convenience variables, initializing
10500 @item init-if-undefined $@var{variable} = @var{expression}
10501 Set a convenience variable if it has not already been set. This is useful
10502 for user-defined commands that keep some state. It is similar, in concept,
10503 to using local static variables with initializers in C (except that
10504 convenience variables are global). It can also be used to allow users to
10505 override default values used in a command script.
10507 If the variable is already defined then the expression is not evaluated so
10508 any side-effects do not occur.
10511 One of the ways to use a convenience variable is as a counter to be
10512 incremented or a pointer to be advanced. For example, to print
10513 a field from successive elements of an array of structures:
10517 print bar[$i++]->contents
10521 Repeat that command by typing @key{RET}.
10523 Some convenience variables are created automatically by @value{GDBN} and given
10524 values likely to be useful.
10527 @vindex $_@r{, convenience variable}
10529 The variable @code{$_} is automatically set by the @code{x} command to
10530 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10531 commands which provide a default address for @code{x} to examine also
10532 set @code{$_} to that address; these commands include @code{info line}
10533 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10534 except when set by the @code{x} command, in which case it is a pointer
10535 to the type of @code{$__}.
10537 @vindex $__@r{, convenience variable}
10539 The variable @code{$__} is automatically set by the @code{x} command
10540 to the value found in the last address examined. Its type is chosen
10541 to match the format in which the data was printed.
10544 @vindex $_exitcode@r{, convenience variable}
10545 When the program being debugged terminates normally, @value{GDBN}
10546 automatically sets this variable to the exit code of the program, and
10547 resets @code{$_exitsignal} to @code{void}.
10550 @vindex $_exitsignal@r{, convenience variable}
10551 When the program being debugged dies due to an uncaught signal,
10552 @value{GDBN} automatically sets this variable to that signal's number,
10553 and resets @code{$_exitcode} to @code{void}.
10555 To distinguish between whether the program being debugged has exited
10556 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10557 @code{$_exitsignal} is not @code{void}), the convenience function
10558 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10559 Functions}). For example, considering the following source code:
10562 #include <signal.h>
10565 main (int argc, char *argv[])
10572 A valid way of telling whether the program being debugged has exited
10573 or signalled would be:
10576 (@value{GDBP}) define has_exited_or_signalled
10577 Type commands for definition of ``has_exited_or_signalled''.
10578 End with a line saying just ``end''.
10579 >if $_isvoid ($_exitsignal)
10580 >echo The program has exited\n
10582 >echo The program has signalled\n
10588 Program terminated with signal SIGALRM, Alarm clock.
10589 The program no longer exists.
10590 (@value{GDBP}) has_exited_or_signalled
10591 The program has signalled
10594 As can be seen, @value{GDBN} correctly informs that the program being
10595 debugged has signalled, since it calls @code{raise} and raises a
10596 @code{SIGALRM} signal. If the program being debugged had not called
10597 @code{raise}, then @value{GDBN} would report a normal exit:
10600 (@value{GDBP}) has_exited_or_signalled
10601 The program has exited
10605 The variable @code{$_exception} is set to the exception object being
10606 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10609 @itemx $_probe_arg0@dots{}$_probe_arg11
10610 Arguments to a static probe. @xref{Static Probe Points}.
10613 @vindex $_sdata@r{, inspect, convenience variable}
10614 The variable @code{$_sdata} contains extra collected static tracepoint
10615 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10616 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10617 if extra static tracepoint data has not been collected.
10620 @vindex $_siginfo@r{, convenience variable}
10621 The variable @code{$_siginfo} contains extra signal information
10622 (@pxref{extra signal information}). Note that @code{$_siginfo}
10623 could be empty, if the application has not yet received any signals.
10624 For example, it will be empty before you execute the @code{run} command.
10627 @vindex $_tlb@r{, convenience variable}
10628 The variable @code{$_tlb} is automatically set when debugging
10629 applications running on MS-Windows in native mode or connected to
10630 gdbserver that supports the @code{qGetTIBAddr} request.
10631 @xref{General Query Packets}.
10632 This variable contains the address of the thread information block.
10635 The number of the current inferior. @xref{Inferiors and
10636 Programs, ,Debugging Multiple Inferiors and Programs}.
10639 The thread number of the current thread. @xref{thread numbers}.
10642 The global number of the current thread. @xref{global thread numbers}.
10646 @node Convenience Funs
10647 @section Convenience Functions
10649 @cindex convenience functions
10650 @value{GDBN} also supplies some @dfn{convenience functions}. These
10651 have a syntax similar to convenience variables. A convenience
10652 function can be used in an expression just like an ordinary function;
10653 however, a convenience function is implemented internally to
10656 These functions do not require @value{GDBN} to be configured with
10657 @code{Python} support, which means that they are always available.
10661 @item $_isvoid (@var{expr})
10662 @findex $_isvoid@r{, convenience function}
10663 Return one if the expression @var{expr} is @code{void}. Otherwise it
10666 A @code{void} expression is an expression where the type of the result
10667 is @code{void}. For example, you can examine a convenience variable
10668 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10672 (@value{GDBP}) print $_exitcode
10674 (@value{GDBP}) print $_isvoid ($_exitcode)
10677 Starting program: ./a.out
10678 [Inferior 1 (process 29572) exited normally]
10679 (@value{GDBP}) print $_exitcode
10681 (@value{GDBP}) print $_isvoid ($_exitcode)
10685 In the example above, we used @code{$_isvoid} to check whether
10686 @code{$_exitcode} is @code{void} before and after the execution of the
10687 program being debugged. Before the execution there is no exit code to
10688 be examined, therefore @code{$_exitcode} is @code{void}. After the
10689 execution the program being debugged returned zero, therefore
10690 @code{$_exitcode} is zero, which means that it is not @code{void}
10693 The @code{void} expression can also be a call of a function from the
10694 program being debugged. For example, given the following function:
10703 The result of calling it inside @value{GDBN} is @code{void}:
10706 (@value{GDBP}) print foo ()
10708 (@value{GDBP}) print $_isvoid (foo ())
10710 (@value{GDBP}) set $v = foo ()
10711 (@value{GDBP}) print $v
10713 (@value{GDBP}) print $_isvoid ($v)
10719 These functions require @value{GDBN} to be configured with
10720 @code{Python} support.
10724 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10725 @findex $_memeq@r{, convenience function}
10726 Returns one if the @var{length} bytes at the addresses given by
10727 @var{buf1} and @var{buf2} are equal.
10728 Otherwise it returns zero.
10730 @item $_regex(@var{str}, @var{regex})
10731 @findex $_regex@r{, convenience function}
10732 Returns one if the string @var{str} matches the regular expression
10733 @var{regex}. Otherwise it returns zero.
10734 The syntax of the regular expression is that specified by @code{Python}'s
10735 regular expression support.
10737 @item $_streq(@var{str1}, @var{str2})
10738 @findex $_streq@r{, convenience function}
10739 Returns one if the strings @var{str1} and @var{str2} are equal.
10740 Otherwise it returns zero.
10742 @item $_strlen(@var{str})
10743 @findex $_strlen@r{, convenience function}
10744 Returns the length of string @var{str}.
10746 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10747 @findex $_caller_is@r{, convenience function}
10748 Returns one if the calling function's name is equal to @var{name}.
10749 Otherwise it returns zero.
10751 If the optional argument @var{number_of_frames} is provided,
10752 it is the number of frames up in the stack to look.
10760 at testsuite/gdb.python/py-caller-is.c:21
10761 #1 0x00000000004005a0 in middle_func ()
10762 at testsuite/gdb.python/py-caller-is.c:27
10763 #2 0x00000000004005ab in top_func ()
10764 at testsuite/gdb.python/py-caller-is.c:33
10765 #3 0x00000000004005b6 in main ()
10766 at testsuite/gdb.python/py-caller-is.c:39
10767 (gdb) print $_caller_is ("middle_func")
10769 (gdb) print $_caller_is ("top_func", 2)
10773 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10774 @findex $_caller_matches@r{, convenience function}
10775 Returns one if the calling function's name matches the regular expression
10776 @var{regexp}. Otherwise it returns zero.
10778 If the optional argument @var{number_of_frames} is provided,
10779 it is the number of frames up in the stack to look.
10782 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10783 @findex $_any_caller_is@r{, convenience function}
10784 Returns one if any calling function's name is equal to @var{name}.
10785 Otherwise it returns zero.
10787 If the optional argument @var{number_of_frames} is provided,
10788 it is the number of frames up in the stack to look.
10791 This function differs from @code{$_caller_is} in that this function
10792 checks all stack frames from the immediate caller to the frame specified
10793 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10794 frame specified by @var{number_of_frames}.
10796 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10797 @findex $_any_caller_matches@r{, convenience function}
10798 Returns one if any calling function's name matches the regular expression
10799 @var{regexp}. Otherwise it returns zero.
10801 If the optional argument @var{number_of_frames} is provided,
10802 it is the number of frames up in the stack to look.
10805 This function differs from @code{$_caller_matches} in that this function
10806 checks all stack frames from the immediate caller to the frame specified
10807 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10808 frame specified by @var{number_of_frames}.
10810 @item $_as_string(@var{value})
10811 @findex $_as_string@r{, convenience function}
10812 Return the string representation of @var{value}.
10814 This function is useful to obtain the textual label (enumerator) of an
10815 enumeration value. For example, assuming the variable @var{node} is of
10816 an enumerated type:
10819 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10820 Visiting node of type NODE_INTEGER
10825 @value{GDBN} provides the ability to list and get help on
10826 convenience functions.
10829 @item help function
10830 @kindex help function
10831 @cindex show all convenience functions
10832 Print a list of all convenience functions.
10839 You can refer to machine register contents, in expressions, as variables
10840 with names starting with @samp{$}. The names of registers are different
10841 for each machine; use @code{info registers} to see the names used on
10845 @kindex info registers
10846 @item info registers
10847 Print the names and values of all registers except floating-point
10848 and vector registers (in the selected stack frame).
10850 @kindex info all-registers
10851 @cindex floating point registers
10852 @item info all-registers
10853 Print the names and values of all registers, including floating-point
10854 and vector registers (in the selected stack frame).
10856 @item info registers @var{regname} @dots{}
10857 Print the @dfn{relativized} value of each specified register @var{regname}.
10858 As discussed in detail below, register values are normally relative to
10859 the selected stack frame. The @var{regname} may be any register name valid on
10860 the machine you are using, with or without the initial @samp{$}.
10863 @anchor{standard registers}
10864 @cindex stack pointer register
10865 @cindex program counter register
10866 @cindex process status register
10867 @cindex frame pointer register
10868 @cindex standard registers
10869 @value{GDBN} has four ``standard'' register names that are available (in
10870 expressions) on most machines---whenever they do not conflict with an
10871 architecture's canonical mnemonics for registers. The register names
10872 @code{$pc} and @code{$sp} are used for the program counter register and
10873 the stack pointer. @code{$fp} is used for a register that contains a
10874 pointer to the current stack frame, and @code{$ps} is used for a
10875 register that contains the processor status. For example,
10876 you could print the program counter in hex with
10883 or print the instruction to be executed next with
10890 or add four to the stack pointer@footnote{This is a way of removing
10891 one word from the stack, on machines where stacks grow downward in
10892 memory (most machines, nowadays). This assumes that the innermost
10893 stack frame is selected; setting @code{$sp} is not allowed when other
10894 stack frames are selected. To pop entire frames off the stack,
10895 regardless of machine architecture, use @code{return};
10896 see @ref{Returning, ,Returning from a Function}.} with
10902 Whenever possible, these four standard register names are available on
10903 your machine even though the machine has different canonical mnemonics,
10904 so long as there is no conflict. The @code{info registers} command
10905 shows the canonical names. For example, on the SPARC, @code{info
10906 registers} displays the processor status register as @code{$psr} but you
10907 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10908 is an alias for the @sc{eflags} register.
10910 @value{GDBN} always considers the contents of an ordinary register as an
10911 integer when the register is examined in this way. Some machines have
10912 special registers which can hold nothing but floating point; these
10913 registers are considered to have floating point values. There is no way
10914 to refer to the contents of an ordinary register as floating point value
10915 (although you can @emph{print} it as a floating point value with
10916 @samp{print/f $@var{regname}}).
10918 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10919 means that the data format in which the register contents are saved by
10920 the operating system is not the same one that your program normally
10921 sees. For example, the registers of the 68881 floating point
10922 coprocessor are always saved in ``extended'' (raw) format, but all C
10923 programs expect to work with ``double'' (virtual) format. In such
10924 cases, @value{GDBN} normally works with the virtual format only (the format
10925 that makes sense for your program), but the @code{info registers} command
10926 prints the data in both formats.
10928 @cindex SSE registers (x86)
10929 @cindex MMX registers (x86)
10930 Some machines have special registers whose contents can be interpreted
10931 in several different ways. For example, modern x86-based machines
10932 have SSE and MMX registers that can hold several values packed
10933 together in several different formats. @value{GDBN} refers to such
10934 registers in @code{struct} notation:
10937 (@value{GDBP}) print $xmm1
10939 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10940 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10941 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10942 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10943 v4_int32 = @{0, 20657912, 11, 13@},
10944 v2_int64 = @{88725056443645952, 55834574859@},
10945 uint128 = 0x0000000d0000000b013b36f800000000
10950 To set values of such registers, you need to tell @value{GDBN} which
10951 view of the register you wish to change, as if you were assigning
10952 value to a @code{struct} member:
10955 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10958 Normally, register values are relative to the selected stack frame
10959 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10960 value that the register would contain if all stack frames farther in
10961 were exited and their saved registers restored. In order to see the
10962 true contents of hardware registers, you must select the innermost
10963 frame (with @samp{frame 0}).
10965 @cindex caller-saved registers
10966 @cindex call-clobbered registers
10967 @cindex volatile registers
10968 @cindex <not saved> values
10969 Usually ABIs reserve some registers as not needed to be saved by the
10970 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10971 registers). It may therefore not be possible for @value{GDBN} to know
10972 the value a register had before the call (in other words, in the outer
10973 frame), if the register value has since been changed by the callee.
10974 @value{GDBN} tries to deduce where the inner frame saved
10975 (``callee-saved'') registers, from the debug info, unwind info, or the
10976 machine code generated by your compiler. If some register is not
10977 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10978 its own knowledge of the ABI, or because the debug/unwind info
10979 explicitly says the register's value is undefined), @value{GDBN}
10980 displays @w{@samp{<not saved>}} as the register's value. With targets
10981 that @value{GDBN} has no knowledge of the register saving convention,
10982 if a register was not saved by the callee, then its value and location
10983 in the outer frame are assumed to be the same of the inner frame.
10984 This is usually harmless, because if the register is call-clobbered,
10985 the caller either does not care what is in the register after the
10986 call, or has code to restore the value that it does care about. Note,
10987 however, that if you change such a register in the outer frame, you
10988 may also be affecting the inner frame. Also, the more ``outer'' the
10989 frame is you're looking at, the more likely a call-clobbered
10990 register's value is to be wrong, in the sense that it doesn't actually
10991 represent the value the register had just before the call.
10993 @node Floating Point Hardware
10994 @section Floating Point Hardware
10995 @cindex floating point
10997 Depending on the configuration, @value{GDBN} may be able to give
10998 you more information about the status of the floating point hardware.
11003 Display hardware-dependent information about the floating
11004 point unit. The exact contents and layout vary depending on the
11005 floating point chip. Currently, @samp{info float} is supported on
11006 the ARM and x86 machines.
11010 @section Vector Unit
11011 @cindex vector unit
11013 Depending on the configuration, @value{GDBN} may be able to give you
11014 more information about the status of the vector unit.
11017 @kindex info vector
11019 Display information about the vector unit. The exact contents and
11020 layout vary depending on the hardware.
11023 @node OS Information
11024 @section Operating System Auxiliary Information
11025 @cindex OS information
11027 @value{GDBN} provides interfaces to useful OS facilities that can help
11028 you debug your program.
11030 @cindex auxiliary vector
11031 @cindex vector, auxiliary
11032 Some operating systems supply an @dfn{auxiliary vector} to programs at
11033 startup. This is akin to the arguments and environment that you
11034 specify for a program, but contains a system-dependent variety of
11035 binary values that tell system libraries important details about the
11036 hardware, operating system, and process. Each value's purpose is
11037 identified by an integer tag; the meanings are well-known but system-specific.
11038 Depending on the configuration and operating system facilities,
11039 @value{GDBN} may be able to show you this information. For remote
11040 targets, this functionality may further depend on the remote stub's
11041 support of the @samp{qXfer:auxv:read} packet, see
11042 @ref{qXfer auxiliary vector read}.
11047 Display the auxiliary vector of the inferior, which can be either a
11048 live process or a core dump file. @value{GDBN} prints each tag value
11049 numerically, and also shows names and text descriptions for recognized
11050 tags. Some values in the vector are numbers, some bit masks, and some
11051 pointers to strings or other data. @value{GDBN} displays each value in the
11052 most appropriate form for a recognized tag, and in hexadecimal for
11053 an unrecognized tag.
11056 On some targets, @value{GDBN} can access operating system-specific
11057 information and show it to you. The types of information available
11058 will differ depending on the type of operating system running on the
11059 target. The mechanism used to fetch the data is described in
11060 @ref{Operating System Information}. For remote targets, this
11061 functionality depends on the remote stub's support of the
11062 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11066 @item info os @var{infotype}
11068 Display OS information of the requested type.
11070 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11072 @anchor{linux info os infotypes}
11074 @kindex info os cpus
11076 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11077 the available fields from /proc/cpuinfo. For each supported architecture
11078 different fields are available. Two common entries are processor which gives
11079 CPU number and bogomips; a system constant that is calculated during
11080 kernel initialization.
11082 @kindex info os files
11084 Display the list of open file descriptors on the target. For each
11085 file descriptor, @value{GDBN} prints the identifier of the process
11086 owning the descriptor, the command of the owning process, the value
11087 of the descriptor, and the target of the descriptor.
11089 @kindex info os modules
11091 Display the list of all loaded kernel modules on the target. For each
11092 module, @value{GDBN} prints the module name, the size of the module in
11093 bytes, the number of times the module is used, the dependencies of the
11094 module, the status of the module, and the address of the loaded module
11097 @kindex info os msg
11099 Display the list of all System V message queues on the target. For each
11100 message queue, @value{GDBN} prints the message queue key, the message
11101 queue identifier, the access permissions, the current number of bytes
11102 on the queue, the current number of messages on the queue, the processes
11103 that last sent and received a message on the queue, the user and group
11104 of the owner and creator of the message queue, the times at which a
11105 message was last sent and received on the queue, and the time at which
11106 the message queue was last changed.
11108 @kindex info os processes
11110 Display the list of processes on the target. For each process,
11111 @value{GDBN} prints the process identifier, the name of the user, the
11112 command corresponding to the process, and the list of processor cores
11113 that the process is currently running on. (To understand what these
11114 properties mean, for this and the following info types, please consult
11115 the general @sc{gnu}/Linux documentation.)
11117 @kindex info os procgroups
11119 Display the list of process groups on the target. For each process,
11120 @value{GDBN} prints the identifier of the process group that it belongs
11121 to, the command corresponding to the process group leader, the process
11122 identifier, and the command line of the process. The list is sorted
11123 first by the process group identifier, then by the process identifier,
11124 so that processes belonging to the same process group are grouped together
11125 and the process group leader is listed first.
11127 @kindex info os semaphores
11129 Display the list of all System V semaphore sets on the target. For each
11130 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11131 set identifier, the access permissions, the number of semaphores in the
11132 set, the user and group of the owner and creator of the semaphore set,
11133 and the times at which the semaphore set was operated upon and changed.
11135 @kindex info os shm
11137 Display the list of all System V shared-memory regions on the target.
11138 For each shared-memory region, @value{GDBN} prints the region key,
11139 the shared-memory identifier, the access permissions, the size of the
11140 region, the process that created the region, the process that last
11141 attached to or detached from the region, the current number of live
11142 attaches to the region, and the times at which the region was last
11143 attached to, detach from, and changed.
11145 @kindex info os sockets
11147 Display the list of Internet-domain sockets on the target. For each
11148 socket, @value{GDBN} prints the address and port of the local and
11149 remote endpoints, the current state of the connection, the creator of
11150 the socket, the IP address family of the socket, and the type of the
11153 @kindex info os threads
11155 Display the list of threads running on the target. For each thread,
11156 @value{GDBN} prints the identifier of the process that the thread
11157 belongs to, the command of the process, the thread identifier, and the
11158 processor core that it is currently running on. The main thread of a
11159 process is not listed.
11163 If @var{infotype} is omitted, then list the possible values for
11164 @var{infotype} and the kind of OS information available for each
11165 @var{infotype}. If the target does not return a list of possible
11166 types, this command will report an error.
11169 @node Memory Region Attributes
11170 @section Memory Region Attributes
11171 @cindex memory region attributes
11173 @dfn{Memory region attributes} allow you to describe special handling
11174 required by regions of your target's memory. @value{GDBN} uses
11175 attributes to determine whether to allow certain types of memory
11176 accesses; whether to use specific width accesses; and whether to cache
11177 target memory. By default the description of memory regions is
11178 fetched from the target (if the current target supports this), but the
11179 user can override the fetched regions.
11181 Defined memory regions can be individually enabled and disabled. When a
11182 memory region is disabled, @value{GDBN} uses the default attributes when
11183 accessing memory in that region. Similarly, if no memory regions have
11184 been defined, @value{GDBN} uses the default attributes when accessing
11187 When a memory region is defined, it is given a number to identify it;
11188 to enable, disable, or remove a memory region, you specify that number.
11192 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11193 Define a memory region bounded by @var{lower} and @var{upper} with
11194 attributes @var{attributes}@dots{}, and add it to the list of regions
11195 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11196 case: it is treated as the target's maximum memory address.
11197 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11200 Discard any user changes to the memory regions and use target-supplied
11201 regions, if available, or no regions if the target does not support.
11204 @item delete mem @var{nums}@dots{}
11205 Remove memory regions @var{nums}@dots{} from the list of regions
11206 monitored by @value{GDBN}.
11208 @kindex disable mem
11209 @item disable mem @var{nums}@dots{}
11210 Disable monitoring of memory regions @var{nums}@dots{}.
11211 A disabled memory region is not forgotten.
11212 It may be enabled again later.
11215 @item enable mem @var{nums}@dots{}
11216 Enable monitoring of memory regions @var{nums}@dots{}.
11220 Print a table of all defined memory regions, with the following columns
11224 @item Memory Region Number
11225 @item Enabled or Disabled.
11226 Enabled memory regions are marked with @samp{y}.
11227 Disabled memory regions are marked with @samp{n}.
11230 The address defining the inclusive lower bound of the memory region.
11233 The address defining the exclusive upper bound of the memory region.
11236 The list of attributes set for this memory region.
11241 @subsection Attributes
11243 @subsubsection Memory Access Mode
11244 The access mode attributes set whether @value{GDBN} may make read or
11245 write accesses to a memory region.
11247 While these attributes prevent @value{GDBN} from performing invalid
11248 memory accesses, they do nothing to prevent the target system, I/O DMA,
11249 etc.@: from accessing memory.
11253 Memory is read only.
11255 Memory is write only.
11257 Memory is read/write. This is the default.
11260 @subsubsection Memory Access Size
11261 The access size attribute tells @value{GDBN} to use specific sized
11262 accesses in the memory region. Often memory mapped device registers
11263 require specific sized accesses. If no access size attribute is
11264 specified, @value{GDBN} may use accesses of any size.
11268 Use 8 bit memory accesses.
11270 Use 16 bit memory accesses.
11272 Use 32 bit memory accesses.
11274 Use 64 bit memory accesses.
11277 @c @subsubsection Hardware/Software Breakpoints
11278 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11279 @c will use hardware or software breakpoints for the internal breakpoints
11280 @c used by the step, next, finish, until, etc. commands.
11284 @c Always use hardware breakpoints
11285 @c @item swbreak (default)
11288 @subsubsection Data Cache
11289 The data cache attributes set whether @value{GDBN} will cache target
11290 memory. While this generally improves performance by reducing debug
11291 protocol overhead, it can lead to incorrect results because @value{GDBN}
11292 does not know about volatile variables or memory mapped device
11297 Enable @value{GDBN} to cache target memory.
11299 Disable @value{GDBN} from caching target memory. This is the default.
11302 @subsection Memory Access Checking
11303 @value{GDBN} can be instructed to refuse accesses to memory that is
11304 not explicitly described. This can be useful if accessing such
11305 regions has undesired effects for a specific target, or to provide
11306 better error checking. The following commands control this behaviour.
11309 @kindex set mem inaccessible-by-default
11310 @item set mem inaccessible-by-default [on|off]
11311 If @code{on} is specified, make @value{GDBN} treat memory not
11312 explicitly described by the memory ranges as non-existent and refuse accesses
11313 to such memory. The checks are only performed if there's at least one
11314 memory range defined. If @code{off} is specified, make @value{GDBN}
11315 treat the memory not explicitly described by the memory ranges as RAM.
11316 The default value is @code{on}.
11317 @kindex show mem inaccessible-by-default
11318 @item show mem inaccessible-by-default
11319 Show the current handling of accesses to unknown memory.
11323 @c @subsubsection Memory Write Verification
11324 @c The memory write verification attributes set whether @value{GDBN}
11325 @c will re-reads data after each write to verify the write was successful.
11329 @c @item noverify (default)
11332 @node Dump/Restore Files
11333 @section Copy Between Memory and a File
11334 @cindex dump/restore files
11335 @cindex append data to a file
11336 @cindex dump data to a file
11337 @cindex restore data from a file
11339 You can use the commands @code{dump}, @code{append}, and
11340 @code{restore} to copy data between target memory and a file. The
11341 @code{dump} and @code{append} commands write data to a file, and the
11342 @code{restore} command reads data from a file back into the inferior's
11343 memory. Files may be in binary, Motorola S-record, Intel hex,
11344 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11345 append to binary files, and cannot read from Verilog Hex files.
11350 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11351 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11352 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11353 or the value of @var{expr}, to @var{filename} in the given format.
11355 The @var{format} parameter may be any one of:
11362 Motorola S-record format.
11364 Tektronix Hex format.
11366 Verilog Hex format.
11369 @value{GDBN} uses the same definitions of these formats as the
11370 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11371 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11375 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11376 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11377 Append the contents of memory from @var{start_addr} to @var{end_addr},
11378 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11379 (@value{GDBN} can only append data to files in raw binary form.)
11382 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11383 Restore the contents of file @var{filename} into memory. The
11384 @code{restore} command can automatically recognize any known @sc{bfd}
11385 file format, except for raw binary. To restore a raw binary file you
11386 must specify the optional keyword @code{binary} after the filename.
11388 If @var{bias} is non-zero, its value will be added to the addresses
11389 contained in the file. Binary files always start at address zero, so
11390 they will be restored at address @var{bias}. Other bfd files have
11391 a built-in location; they will be restored at offset @var{bias}
11392 from that location.
11394 If @var{start} and/or @var{end} are non-zero, then only data between
11395 file offset @var{start} and file offset @var{end} will be restored.
11396 These offsets are relative to the addresses in the file, before
11397 the @var{bias} argument is applied.
11401 @node Core File Generation
11402 @section How to Produce a Core File from Your Program
11403 @cindex dump core from inferior
11405 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11406 image of a running process and its process status (register values
11407 etc.). Its primary use is post-mortem debugging of a program that
11408 crashed while it ran outside a debugger. A program that crashes
11409 automatically produces a core file, unless this feature is disabled by
11410 the user. @xref{Files}, for information on invoking @value{GDBN} in
11411 the post-mortem debugging mode.
11413 Occasionally, you may wish to produce a core file of the program you
11414 are debugging in order to preserve a snapshot of its state.
11415 @value{GDBN} has a special command for that.
11419 @kindex generate-core-file
11420 @item generate-core-file [@var{file}]
11421 @itemx gcore [@var{file}]
11422 Produce a core dump of the inferior process. The optional argument
11423 @var{file} specifies the file name where to put the core dump. If not
11424 specified, the file name defaults to @file{core.@var{pid}}, where
11425 @var{pid} is the inferior process ID.
11427 Note that this command is implemented only for some systems (as of
11428 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11430 On @sc{gnu}/Linux, this command can take into account the value of the
11431 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11432 dump (@pxref{set use-coredump-filter}).
11434 @kindex set use-coredump-filter
11435 @anchor{set use-coredump-filter}
11436 @item set use-coredump-filter on
11437 @itemx set use-coredump-filter off
11438 Enable or disable the use of the file
11439 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11440 files. This file is used by the Linux kernel to decide what types of
11441 memory mappings will be dumped or ignored when generating a core dump
11442 file. @var{pid} is the process ID of a currently running process.
11444 To make use of this feature, you have to write in the
11445 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11446 which is a bit mask representing the memory mapping types. If a bit
11447 is set in the bit mask, then the memory mappings of the corresponding
11448 types will be dumped; otherwise, they will be ignored. This
11449 configuration is inherited by child processes. For more information
11450 about the bits that can be set in the
11451 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11452 manpage of @code{core(5)}.
11454 By default, this option is @code{on}. If this option is turned
11455 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11456 and instead uses the same default value as the Linux kernel in order
11457 to decide which pages will be dumped in the core dump file. This
11458 value is currently @code{0x33}, which means that bits @code{0}
11459 (anonymous private mappings), @code{1} (anonymous shared mappings),
11460 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11461 This will cause these memory mappings to be dumped automatically.
11464 @node Character Sets
11465 @section Character Sets
11466 @cindex character sets
11468 @cindex translating between character sets
11469 @cindex host character set
11470 @cindex target character set
11472 If the program you are debugging uses a different character set to
11473 represent characters and strings than the one @value{GDBN} uses itself,
11474 @value{GDBN} can automatically translate between the character sets for
11475 you. The character set @value{GDBN} uses we call the @dfn{host
11476 character set}; the one the inferior program uses we call the
11477 @dfn{target character set}.
11479 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11480 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11481 remote protocol (@pxref{Remote Debugging}) to debug a program
11482 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11483 then the host character set is Latin-1, and the target character set is
11484 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11485 target-charset EBCDIC-US}, then @value{GDBN} translates between
11486 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11487 character and string literals in expressions.
11489 @value{GDBN} has no way to automatically recognize which character set
11490 the inferior program uses; you must tell it, using the @code{set
11491 target-charset} command, described below.
11493 Here are the commands for controlling @value{GDBN}'s character set
11497 @item set target-charset @var{charset}
11498 @kindex set target-charset
11499 Set the current target character set to @var{charset}. To display the
11500 list of supported target character sets, type
11501 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11503 @item set host-charset @var{charset}
11504 @kindex set host-charset
11505 Set the current host character set to @var{charset}.
11507 By default, @value{GDBN} uses a host character set appropriate to the
11508 system it is running on; you can override that default using the
11509 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11510 automatically determine the appropriate host character set. In this
11511 case, @value{GDBN} uses @samp{UTF-8}.
11513 @value{GDBN} can only use certain character sets as its host character
11514 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11515 @value{GDBN} will list the host character sets it supports.
11517 @item set charset @var{charset}
11518 @kindex set charset
11519 Set the current host and target character sets to @var{charset}. As
11520 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11521 @value{GDBN} will list the names of the character sets that can be used
11522 for both host and target.
11525 @kindex show charset
11526 Show the names of the current host and target character sets.
11528 @item show host-charset
11529 @kindex show host-charset
11530 Show the name of the current host character set.
11532 @item show target-charset
11533 @kindex show target-charset
11534 Show the name of the current target character set.
11536 @item set target-wide-charset @var{charset}
11537 @kindex set target-wide-charset
11538 Set the current target's wide character set to @var{charset}. This is
11539 the character set used by the target's @code{wchar_t} type. To
11540 display the list of supported wide character sets, type
11541 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11543 @item show target-wide-charset
11544 @kindex show target-wide-charset
11545 Show the name of the current target's wide character set.
11548 Here is an example of @value{GDBN}'s character set support in action.
11549 Assume that the following source code has been placed in the file
11550 @file{charset-test.c}:
11556 = @{72, 101, 108, 108, 111, 44, 32, 119,
11557 111, 114, 108, 100, 33, 10, 0@};
11558 char ibm1047_hello[]
11559 = @{200, 133, 147, 147, 150, 107, 64, 166,
11560 150, 153, 147, 132, 90, 37, 0@};
11564 printf ("Hello, world!\n");
11568 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11569 containing the string @samp{Hello, world!} followed by a newline,
11570 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11572 We compile the program, and invoke the debugger on it:
11575 $ gcc -g charset-test.c -o charset-test
11576 $ gdb -nw charset-test
11577 GNU gdb 2001-12-19-cvs
11578 Copyright 2001 Free Software Foundation, Inc.
11583 We can use the @code{show charset} command to see what character sets
11584 @value{GDBN} is currently using to interpret and display characters and
11588 (@value{GDBP}) show charset
11589 The current host and target character set is `ISO-8859-1'.
11593 For the sake of printing this manual, let's use @sc{ascii} as our
11594 initial character set:
11596 (@value{GDBP}) set charset ASCII
11597 (@value{GDBP}) show charset
11598 The current host and target character set is `ASCII'.
11602 Let's assume that @sc{ascii} is indeed the correct character set for our
11603 host system --- in other words, let's assume that if @value{GDBN} prints
11604 characters using the @sc{ascii} character set, our terminal will display
11605 them properly. Since our current target character set is also
11606 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11609 (@value{GDBP}) print ascii_hello
11610 $1 = 0x401698 "Hello, world!\n"
11611 (@value{GDBP}) print ascii_hello[0]
11616 @value{GDBN} uses the target character set for character and string
11617 literals you use in expressions:
11620 (@value{GDBP}) print '+'
11625 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11628 @value{GDBN} relies on the user to tell it which character set the
11629 target program uses. If we print @code{ibm1047_hello} while our target
11630 character set is still @sc{ascii}, we get jibberish:
11633 (@value{GDBP}) print ibm1047_hello
11634 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11635 (@value{GDBP}) print ibm1047_hello[0]
11640 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11641 @value{GDBN} tells us the character sets it supports:
11644 (@value{GDBP}) set target-charset
11645 ASCII EBCDIC-US IBM1047 ISO-8859-1
11646 (@value{GDBP}) set target-charset
11649 We can select @sc{ibm1047} as our target character set, and examine the
11650 program's strings again. Now the @sc{ascii} string is wrong, but
11651 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11652 target character set, @sc{ibm1047}, to the host character set,
11653 @sc{ascii}, and they display correctly:
11656 (@value{GDBP}) set target-charset IBM1047
11657 (@value{GDBP}) show charset
11658 The current host character set is `ASCII'.
11659 The current target character set is `IBM1047'.
11660 (@value{GDBP}) print ascii_hello
11661 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11662 (@value{GDBP}) print ascii_hello[0]
11664 (@value{GDBP}) print ibm1047_hello
11665 $8 = 0x4016a8 "Hello, world!\n"
11666 (@value{GDBP}) print ibm1047_hello[0]
11671 As above, @value{GDBN} uses the target character set for character and
11672 string literals you use in expressions:
11675 (@value{GDBP}) print '+'
11680 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11683 @node Caching Target Data
11684 @section Caching Data of Targets
11685 @cindex caching data of targets
11687 @value{GDBN} caches data exchanged between the debugger and a target.
11688 Each cache is associated with the address space of the inferior.
11689 @xref{Inferiors and Programs}, about inferior and address space.
11690 Such caching generally improves performance in remote debugging
11691 (@pxref{Remote Debugging}), because it reduces the overhead of the
11692 remote protocol by bundling memory reads and writes into large chunks.
11693 Unfortunately, simply caching everything would lead to incorrect results,
11694 since @value{GDBN} does not necessarily know anything about volatile
11695 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11696 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11698 Therefore, by default, @value{GDBN} only caches data
11699 known to be on the stack@footnote{In non-stop mode, it is moderately
11700 rare for a running thread to modify the stack of a stopped thread
11701 in a way that would interfere with a backtrace, and caching of
11702 stack reads provides a significant speed up of remote backtraces.} or
11703 in the code segment.
11704 Other regions of memory can be explicitly marked as
11705 cacheable; @pxref{Memory Region Attributes}.
11708 @kindex set remotecache
11709 @item set remotecache on
11710 @itemx set remotecache off
11711 This option no longer does anything; it exists for compatibility
11714 @kindex show remotecache
11715 @item show remotecache
11716 Show the current state of the obsolete remotecache flag.
11718 @kindex set stack-cache
11719 @item set stack-cache on
11720 @itemx set stack-cache off
11721 Enable or disable caching of stack accesses. When @code{on}, use
11722 caching. By default, this option is @code{on}.
11724 @kindex show stack-cache
11725 @item show stack-cache
11726 Show the current state of data caching for memory accesses.
11728 @kindex set code-cache
11729 @item set code-cache on
11730 @itemx set code-cache off
11731 Enable or disable caching of code segment accesses. When @code{on},
11732 use caching. By default, this option is @code{on}. This improves
11733 performance of disassembly in remote debugging.
11735 @kindex show code-cache
11736 @item show code-cache
11737 Show the current state of target memory cache for code segment
11740 @kindex info dcache
11741 @item info dcache @r{[}line@r{]}
11742 Print the information about the performance of data cache of the
11743 current inferior's address space. The information displayed
11744 includes the dcache width and depth, and for each cache line, its
11745 number, address, and how many times it was referenced. This
11746 command is useful for debugging the data cache operation.
11748 If a line number is specified, the contents of that line will be
11751 @item set dcache size @var{size}
11752 @cindex dcache size
11753 @kindex set dcache size
11754 Set maximum number of entries in dcache (dcache depth above).
11756 @item set dcache line-size @var{line-size}
11757 @cindex dcache line-size
11758 @kindex set dcache line-size
11759 Set number of bytes each dcache entry caches (dcache width above).
11760 Must be a power of 2.
11762 @item show dcache size
11763 @kindex show dcache size
11764 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11766 @item show dcache line-size
11767 @kindex show dcache line-size
11768 Show default size of dcache lines.
11772 @node Searching Memory
11773 @section Search Memory
11774 @cindex searching memory
11776 Memory can be searched for a particular sequence of bytes with the
11777 @code{find} command.
11781 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11782 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11783 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11784 etc. The search begins at address @var{start_addr} and continues for either
11785 @var{len} bytes or through to @var{end_addr} inclusive.
11788 @var{s} and @var{n} are optional parameters.
11789 They may be specified in either order, apart or together.
11792 @item @var{s}, search query size
11793 The size of each search query value.
11799 halfwords (two bytes)
11803 giant words (eight bytes)
11806 All values are interpreted in the current language.
11807 This means, for example, that if the current source language is C/C@t{++}
11808 then searching for the string ``hello'' includes the trailing '\0'.
11810 If the value size is not specified, it is taken from the
11811 value's type in the current language.
11812 This is useful when one wants to specify the search
11813 pattern as a mixture of types.
11814 Note that this means, for example, that in the case of C-like languages
11815 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11816 which is typically four bytes.
11818 @item @var{n}, maximum number of finds
11819 The maximum number of matches to print. The default is to print all finds.
11822 You can use strings as search values. Quote them with double-quotes
11824 The string value is copied into the search pattern byte by byte,
11825 regardless of the endianness of the target and the size specification.
11827 The address of each match found is printed as well as a count of the
11828 number of matches found.
11830 The address of the last value found is stored in convenience variable
11832 A count of the number of matches is stored in @samp{$numfound}.
11834 For example, if stopped at the @code{printf} in this function:
11840 static char hello[] = "hello-hello";
11841 static struct @{ char c; short s; int i; @}
11842 __attribute__ ((packed)) mixed
11843 = @{ 'c', 0x1234, 0x87654321 @};
11844 printf ("%s\n", hello);
11849 you get during debugging:
11852 (gdb) find &hello[0], +sizeof(hello), "hello"
11853 0x804956d <hello.1620+6>
11855 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11856 0x8049567 <hello.1620>
11857 0x804956d <hello.1620+6>
11859 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11860 0x8049567 <hello.1620>
11862 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11863 0x8049560 <mixed.1625>
11865 (gdb) print $numfound
11868 $2 = (void *) 0x8049560
11872 @section Value Sizes
11874 Whenever @value{GDBN} prints a value memory will be allocated within
11875 @value{GDBN} to hold the contents of the value. It is possible in
11876 some languages with dynamic typing systems, that an invalid program
11877 may indicate a value that is incorrectly large, this in turn may cause
11878 @value{GDBN} to try and allocate an overly large ammount of memory.
11881 @kindex set max-value-size
11882 @item set max-value-size @var{bytes}
11883 @itemx set max-value-size unlimited
11884 Set the maximum size of memory that @value{GDBN} will allocate for the
11885 contents of a value to @var{bytes}, trying to display a value that
11886 requires more memory than that will result in an error.
11888 Setting this variable does not effect values that have already been
11889 allocated within @value{GDBN}, only future allocations.
11891 There's a minimum size that @code{max-value-size} can be set to in
11892 order that @value{GDBN} can still operate correctly, this minimum is
11893 currently 16 bytes.
11895 The limit applies to the results of some subexpressions as well as to
11896 complete expressions. For example, an expression denoting a simple
11897 integer component, such as @code{x.y.z}, may fail if the size of
11898 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11899 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11900 @var{A} is an array variable with non-constant size, will generally
11901 succeed regardless of the bounds on @var{A}, as long as the component
11902 size is less than @var{bytes}.
11904 The default value of @code{max-value-size} is currently 64k.
11906 @kindex show max-value-size
11907 @item show max-value-size
11908 Show the maximum size of memory, in bytes, that @value{GDBN} will
11909 allocate for the contents of a value.
11912 @node Optimized Code
11913 @chapter Debugging Optimized Code
11914 @cindex optimized code, debugging
11915 @cindex debugging optimized code
11917 Almost all compilers support optimization. With optimization
11918 disabled, the compiler generates assembly code that corresponds
11919 directly to your source code, in a simplistic way. As the compiler
11920 applies more powerful optimizations, the generated assembly code
11921 diverges from your original source code. With help from debugging
11922 information generated by the compiler, @value{GDBN} can map from
11923 the running program back to constructs from your original source.
11925 @value{GDBN} is more accurate with optimization disabled. If you
11926 can recompile without optimization, it is easier to follow the
11927 progress of your program during debugging. But, there are many cases
11928 where you may need to debug an optimized version.
11930 When you debug a program compiled with @samp{-g -O}, remember that the
11931 optimizer has rearranged your code; the debugger shows you what is
11932 really there. Do not be too surprised when the execution path does not
11933 exactly match your source file! An extreme example: if you define a
11934 variable, but never use it, @value{GDBN} never sees that
11935 variable---because the compiler optimizes it out of existence.
11937 Some things do not work as well with @samp{-g -O} as with just
11938 @samp{-g}, particularly on machines with instruction scheduling. If in
11939 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11940 please report it to us as a bug (including a test case!).
11941 @xref{Variables}, for more information about debugging optimized code.
11944 * Inline Functions:: How @value{GDBN} presents inlining
11945 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11948 @node Inline Functions
11949 @section Inline Functions
11950 @cindex inline functions, debugging
11952 @dfn{Inlining} is an optimization that inserts a copy of the function
11953 body directly at each call site, instead of jumping to a shared
11954 routine. @value{GDBN} displays inlined functions just like
11955 non-inlined functions. They appear in backtraces. You can view their
11956 arguments and local variables, step into them with @code{step}, skip
11957 them with @code{next}, and escape from them with @code{finish}.
11958 You can check whether a function was inlined by using the
11959 @code{info frame} command.
11961 For @value{GDBN} to support inlined functions, the compiler must
11962 record information about inlining in the debug information ---
11963 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11964 other compilers do also. @value{GDBN} only supports inlined functions
11965 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11966 do not emit two required attributes (@samp{DW_AT_call_file} and
11967 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11968 function calls with earlier versions of @value{NGCC}. It instead
11969 displays the arguments and local variables of inlined functions as
11970 local variables in the caller.
11972 The body of an inlined function is directly included at its call site;
11973 unlike a non-inlined function, there are no instructions devoted to
11974 the call. @value{GDBN} still pretends that the call site and the
11975 start of the inlined function are different instructions. Stepping to
11976 the call site shows the call site, and then stepping again shows
11977 the first line of the inlined function, even though no additional
11978 instructions are executed.
11980 This makes source-level debugging much clearer; you can see both the
11981 context of the call and then the effect of the call. Only stepping by
11982 a single instruction using @code{stepi} or @code{nexti} does not do
11983 this; single instruction steps always show the inlined body.
11985 There are some ways that @value{GDBN} does not pretend that inlined
11986 function calls are the same as normal calls:
11990 Setting breakpoints at the call site of an inlined function may not
11991 work, because the call site does not contain any code. @value{GDBN}
11992 may incorrectly move the breakpoint to the next line of the enclosing
11993 function, after the call. This limitation will be removed in a future
11994 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11995 or inside the inlined function instead.
11998 @value{GDBN} cannot locate the return value of inlined calls after
11999 using the @code{finish} command. This is a limitation of compiler-generated
12000 debugging information; after @code{finish}, you can step to the next line
12001 and print a variable where your program stored the return value.
12005 @node Tail Call Frames
12006 @section Tail Call Frames
12007 @cindex tail call frames, debugging
12009 Function @code{B} can call function @code{C} in its very last statement. In
12010 unoptimized compilation the call of @code{C} is immediately followed by return
12011 instruction at the end of @code{B} code. Optimizing compiler may replace the
12012 call and return in function @code{B} into one jump to function @code{C}
12013 instead. Such use of a jump instruction is called @dfn{tail call}.
12015 During execution of function @code{C}, there will be no indication in the
12016 function call stack frames that it was tail-called from @code{B}. If function
12017 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12018 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12019 some cases @value{GDBN} can determine that @code{C} was tail-called from
12020 @code{B}, and it will then create fictitious call frame for that, with the
12021 return address set up as if @code{B} called @code{C} normally.
12023 This functionality is currently supported only by DWARF 2 debugging format and
12024 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
12025 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12028 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12029 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12033 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12035 Stack level 1, frame at 0x7fffffffda30:
12036 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12037 tail call frame, caller of frame at 0x7fffffffda30
12038 source language c++.
12039 Arglist at unknown address.
12040 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12043 The detection of all the possible code path executions can find them ambiguous.
12044 There is no execution history stored (possible @ref{Reverse Execution} is never
12045 used for this purpose) and the last known caller could have reached the known
12046 callee by multiple different jump sequences. In such case @value{GDBN} still
12047 tries to show at least all the unambiguous top tail callers and all the
12048 unambiguous bottom tail calees, if any.
12051 @anchor{set debug entry-values}
12052 @item set debug entry-values
12053 @kindex set debug entry-values
12054 When set to on, enables printing of analysis messages for both frame argument
12055 values at function entry and tail calls. It will show all the possible valid
12056 tail calls code paths it has considered. It will also print the intersection
12057 of them with the final unambiguous (possibly partial or even empty) code path
12060 @item show debug entry-values
12061 @kindex show debug entry-values
12062 Show the current state of analysis messages printing for both frame argument
12063 values at function entry and tail calls.
12066 The analysis messages for tail calls can for example show why the virtual tail
12067 call frame for function @code{c} has not been recognized (due to the indirect
12068 reference by variable @code{x}):
12071 static void __attribute__((noinline, noclone)) c (void);
12072 void (*x) (void) = c;
12073 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12074 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12075 int main (void) @{ x (); return 0; @}
12077 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
12078 DW_TAG_GNU_call_site 0x40039a in main
12080 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12083 #1 0x000000000040039a in main () at t.c:5
12086 Another possibility is an ambiguous virtual tail call frames resolution:
12090 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12091 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12092 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12093 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12094 static void __attribute__((noinline, noclone)) b (void)
12095 @{ if (i) c (); else e (); @}
12096 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12097 int main (void) @{ a (); return 0; @}
12099 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12100 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12101 tailcall: reduced: 0x4004d2(a) |
12104 #1 0x00000000004004d2 in a () at t.c:8
12105 #2 0x0000000000400395 in main () at t.c:9
12108 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12109 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12111 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12112 @ifset HAVE_MAKEINFO_CLICK
12113 @set ARROW @click{}
12114 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12115 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12117 @ifclear HAVE_MAKEINFO_CLICK
12119 @set CALLSEQ1B @value{CALLSEQ1A}
12120 @set CALLSEQ2B @value{CALLSEQ2A}
12123 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12124 The code can have possible execution paths @value{CALLSEQ1B} or
12125 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12127 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12128 has found. It then finds another possible calling sequcen - that one is
12129 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12130 printed as the @code{reduced:} calling sequence. That one could have many
12131 futher @code{compare:} and @code{reduced:} statements as long as there remain
12132 any non-ambiguous sequence entries.
12134 For the frame of function @code{b} in both cases there are different possible
12135 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12136 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12137 therefore this one is displayed to the user while the ambiguous frames are
12140 There can be also reasons why printing of frame argument values at function
12145 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12146 static void __attribute__((noinline, noclone)) a (int i);
12147 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12148 static void __attribute__((noinline, noclone)) a (int i)
12149 @{ if (i) b (i - 1); else c (0); @}
12150 int main (void) @{ a (5); return 0; @}
12153 #0 c (i=i@@entry=0) at t.c:2
12154 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
12155 function "a" at 0x400420 can call itself via tail calls
12156 i=<optimized out>) at t.c:6
12157 #2 0x000000000040036e in main () at t.c:7
12160 @value{GDBN} cannot find out from the inferior state if and how many times did
12161 function @code{a} call itself (via function @code{b}) as these calls would be
12162 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12163 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12164 prints @code{<optimized out>} instead.
12167 @chapter C Preprocessor Macros
12169 Some languages, such as C and C@t{++}, provide a way to define and invoke
12170 ``preprocessor macros'' which expand into strings of tokens.
12171 @value{GDBN} can evaluate expressions containing macro invocations, show
12172 the result of macro expansion, and show a macro's definition, including
12173 where it was defined.
12175 You may need to compile your program specially to provide @value{GDBN}
12176 with information about preprocessor macros. Most compilers do not
12177 include macros in their debugging information, even when you compile
12178 with the @option{-g} flag. @xref{Compilation}.
12180 A program may define a macro at one point, remove that definition later,
12181 and then provide a different definition after that. Thus, at different
12182 points in the program, a macro may have different definitions, or have
12183 no definition at all. If there is a current stack frame, @value{GDBN}
12184 uses the macros in scope at that frame's source code line. Otherwise,
12185 @value{GDBN} uses the macros in scope at the current listing location;
12188 Whenever @value{GDBN} evaluates an expression, it always expands any
12189 macro invocations present in the expression. @value{GDBN} also provides
12190 the following commands for working with macros explicitly.
12194 @kindex macro expand
12195 @cindex macro expansion, showing the results of preprocessor
12196 @cindex preprocessor macro expansion, showing the results of
12197 @cindex expanding preprocessor macros
12198 @item macro expand @var{expression}
12199 @itemx macro exp @var{expression}
12200 Show the results of expanding all preprocessor macro invocations in
12201 @var{expression}. Since @value{GDBN} simply expands macros, but does
12202 not parse the result, @var{expression} need not be a valid expression;
12203 it can be any string of tokens.
12206 @item macro expand-once @var{expression}
12207 @itemx macro exp1 @var{expression}
12208 @cindex expand macro once
12209 @i{(This command is not yet implemented.)} Show the results of
12210 expanding those preprocessor macro invocations that appear explicitly in
12211 @var{expression}. Macro invocations appearing in that expansion are
12212 left unchanged. This command allows you to see the effect of a
12213 particular macro more clearly, without being confused by further
12214 expansions. Since @value{GDBN} simply expands macros, but does not
12215 parse the result, @var{expression} need not be a valid expression; it
12216 can be any string of tokens.
12219 @cindex macro definition, showing
12220 @cindex definition of a macro, showing
12221 @cindex macros, from debug info
12222 @item info macro [-a|-all] [--] @var{macro}
12223 Show the current definition or all definitions of the named @var{macro},
12224 and describe the source location or compiler command-line where that
12225 definition was established. The optional double dash is to signify the end of
12226 argument processing and the beginning of @var{macro} for non C-like macros where
12227 the macro may begin with a hyphen.
12229 @kindex info macros
12230 @item info macros @var{location}
12231 Show all macro definitions that are in effect at the location specified
12232 by @var{location}, and describe the source location or compiler
12233 command-line where those definitions were established.
12235 @kindex macro define
12236 @cindex user-defined macros
12237 @cindex defining macros interactively
12238 @cindex macros, user-defined
12239 @item macro define @var{macro} @var{replacement-list}
12240 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12241 Introduce a definition for a preprocessor macro named @var{macro},
12242 invocations of which are replaced by the tokens given in
12243 @var{replacement-list}. The first form of this command defines an
12244 ``object-like'' macro, which takes no arguments; the second form
12245 defines a ``function-like'' macro, which takes the arguments given in
12248 A definition introduced by this command is in scope in every
12249 expression evaluated in @value{GDBN}, until it is removed with the
12250 @code{macro undef} command, described below. The definition overrides
12251 all definitions for @var{macro} present in the program being debugged,
12252 as well as any previous user-supplied definition.
12254 @kindex macro undef
12255 @item macro undef @var{macro}
12256 Remove any user-supplied definition for the macro named @var{macro}.
12257 This command only affects definitions provided with the @code{macro
12258 define} command, described above; it cannot remove definitions present
12259 in the program being debugged.
12263 List all the macros defined using the @code{macro define} command.
12266 @cindex macros, example of debugging with
12267 Here is a transcript showing the above commands in action. First, we
12268 show our source files:
12273 #include "sample.h"
12276 #define ADD(x) (M + x)
12281 printf ("Hello, world!\n");
12283 printf ("We're so creative.\n");
12285 printf ("Goodbye, world!\n");
12292 Now, we compile the program using the @sc{gnu} C compiler,
12293 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12294 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12295 and @option{-gdwarf-4}; we recommend always choosing the most recent
12296 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12297 includes information about preprocessor macros in the debugging
12301 $ gcc -gdwarf-2 -g3 sample.c -o sample
12305 Now, we start @value{GDBN} on our sample program:
12309 GNU gdb 2002-05-06-cvs
12310 Copyright 2002 Free Software Foundation, Inc.
12311 GDB is free software, @dots{}
12315 We can expand macros and examine their definitions, even when the
12316 program is not running. @value{GDBN} uses the current listing position
12317 to decide which macro definitions are in scope:
12320 (@value{GDBP}) list main
12323 5 #define ADD(x) (M + x)
12328 10 printf ("Hello, world!\n");
12330 12 printf ("We're so creative.\n");
12331 (@value{GDBP}) info macro ADD
12332 Defined at /home/jimb/gdb/macros/play/sample.c:5
12333 #define ADD(x) (M + x)
12334 (@value{GDBP}) info macro Q
12335 Defined at /home/jimb/gdb/macros/play/sample.h:1
12336 included at /home/jimb/gdb/macros/play/sample.c:2
12338 (@value{GDBP}) macro expand ADD(1)
12339 expands to: (42 + 1)
12340 (@value{GDBP}) macro expand-once ADD(1)
12341 expands to: once (M + 1)
12345 In the example above, note that @code{macro expand-once} expands only
12346 the macro invocation explicit in the original text --- the invocation of
12347 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12348 which was introduced by @code{ADD}.
12350 Once the program is running, @value{GDBN} uses the macro definitions in
12351 force at the source line of the current stack frame:
12354 (@value{GDBP}) break main
12355 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12357 Starting program: /home/jimb/gdb/macros/play/sample
12359 Breakpoint 1, main () at sample.c:10
12360 10 printf ("Hello, world!\n");
12364 At line 10, the definition of the macro @code{N} at line 9 is in force:
12367 (@value{GDBP}) info macro N
12368 Defined at /home/jimb/gdb/macros/play/sample.c:9
12370 (@value{GDBP}) macro expand N Q M
12371 expands to: 28 < 42
12372 (@value{GDBP}) print N Q M
12377 As we step over directives that remove @code{N}'s definition, and then
12378 give it a new definition, @value{GDBN} finds the definition (or lack
12379 thereof) in force at each point:
12382 (@value{GDBP}) next
12384 12 printf ("We're so creative.\n");
12385 (@value{GDBP}) info macro N
12386 The symbol `N' has no definition as a C/C++ preprocessor macro
12387 at /home/jimb/gdb/macros/play/sample.c:12
12388 (@value{GDBP}) next
12390 14 printf ("Goodbye, world!\n");
12391 (@value{GDBP}) info macro N
12392 Defined at /home/jimb/gdb/macros/play/sample.c:13
12394 (@value{GDBP}) macro expand N Q M
12395 expands to: 1729 < 42
12396 (@value{GDBP}) print N Q M
12401 In addition to source files, macros can be defined on the compilation command
12402 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12403 such a way, @value{GDBN} displays the location of their definition as line zero
12404 of the source file submitted to the compiler.
12407 (@value{GDBP}) info macro __STDC__
12408 Defined at /home/jimb/gdb/macros/play/sample.c:0
12415 @chapter Tracepoints
12416 @c This chapter is based on the documentation written by Michael
12417 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12419 @cindex tracepoints
12420 In some applications, it is not feasible for the debugger to interrupt
12421 the program's execution long enough for the developer to learn
12422 anything helpful about its behavior. If the program's correctness
12423 depends on its real-time behavior, delays introduced by a debugger
12424 might cause the program to change its behavior drastically, or perhaps
12425 fail, even when the code itself is correct. It is useful to be able
12426 to observe the program's behavior without interrupting it.
12428 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12429 specify locations in the program, called @dfn{tracepoints}, and
12430 arbitrary expressions to evaluate when those tracepoints are reached.
12431 Later, using the @code{tfind} command, you can examine the values
12432 those expressions had when the program hit the tracepoints. The
12433 expressions may also denote objects in memory---structures or arrays,
12434 for example---whose values @value{GDBN} should record; while visiting
12435 a particular tracepoint, you may inspect those objects as if they were
12436 in memory at that moment. However, because @value{GDBN} records these
12437 values without interacting with you, it can do so quickly and
12438 unobtrusively, hopefully not disturbing the program's behavior.
12440 The tracepoint facility is currently available only for remote
12441 targets. @xref{Targets}. In addition, your remote target must know
12442 how to collect trace data. This functionality is implemented in the
12443 remote stub; however, none of the stubs distributed with @value{GDBN}
12444 support tracepoints as of this writing. The format of the remote
12445 packets used to implement tracepoints are described in @ref{Tracepoint
12448 It is also possible to get trace data from a file, in a manner reminiscent
12449 of corefiles; you specify the filename, and use @code{tfind} to search
12450 through the file. @xref{Trace Files}, for more details.
12452 This chapter describes the tracepoint commands and features.
12455 * Set Tracepoints::
12456 * Analyze Collected Data::
12457 * Tracepoint Variables::
12461 @node Set Tracepoints
12462 @section Commands to Set Tracepoints
12464 Before running such a @dfn{trace experiment}, an arbitrary number of
12465 tracepoints can be set. A tracepoint is actually a special type of
12466 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12467 standard breakpoint commands. For instance, as with breakpoints,
12468 tracepoint numbers are successive integers starting from one, and many
12469 of the commands associated with tracepoints take the tracepoint number
12470 as their argument, to identify which tracepoint to work on.
12472 For each tracepoint, you can specify, in advance, some arbitrary set
12473 of data that you want the target to collect in the trace buffer when
12474 it hits that tracepoint. The collected data can include registers,
12475 local variables, or global data. Later, you can use @value{GDBN}
12476 commands to examine the values these data had at the time the
12477 tracepoint was hit.
12479 Tracepoints do not support every breakpoint feature. Ignore counts on
12480 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12481 commands when they are hit. Tracepoints may not be thread-specific
12484 @cindex fast tracepoints
12485 Some targets may support @dfn{fast tracepoints}, which are inserted in
12486 a different way (such as with a jump instead of a trap), that is
12487 faster but possibly restricted in where they may be installed.
12489 @cindex static tracepoints
12490 @cindex markers, static tracepoints
12491 @cindex probing markers, static tracepoints
12492 Regular and fast tracepoints are dynamic tracing facilities, meaning
12493 that they can be used to insert tracepoints at (almost) any location
12494 in the target. Some targets may also support controlling @dfn{static
12495 tracepoints} from @value{GDBN}. With static tracing, a set of
12496 instrumentation points, also known as @dfn{markers}, are embedded in
12497 the target program, and can be activated or deactivated by name or
12498 address. These are usually placed at locations which facilitate
12499 investigating what the target is actually doing. @value{GDBN}'s
12500 support for static tracing includes being able to list instrumentation
12501 points, and attach them with @value{GDBN} defined high level
12502 tracepoints that expose the whole range of convenience of
12503 @value{GDBN}'s tracepoints support. Namely, support for collecting
12504 registers values and values of global or local (to the instrumentation
12505 point) variables; tracepoint conditions and trace state variables.
12506 The act of installing a @value{GDBN} static tracepoint on an
12507 instrumentation point, or marker, is referred to as @dfn{probing} a
12508 static tracepoint marker.
12510 @code{gdbserver} supports tracepoints on some target systems.
12511 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12513 This section describes commands to set tracepoints and associated
12514 conditions and actions.
12517 * Create and Delete Tracepoints::
12518 * Enable and Disable Tracepoints::
12519 * Tracepoint Passcounts::
12520 * Tracepoint Conditions::
12521 * Trace State Variables::
12522 * Tracepoint Actions::
12523 * Listing Tracepoints::
12524 * Listing Static Tracepoint Markers::
12525 * Starting and Stopping Trace Experiments::
12526 * Tracepoint Restrictions::
12529 @node Create and Delete Tracepoints
12530 @subsection Create and Delete Tracepoints
12533 @cindex set tracepoint
12535 @item trace @var{location}
12536 The @code{trace} command is very similar to the @code{break} command.
12537 Its argument @var{location} can be any valid location.
12538 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12539 which is a point in the target program where the debugger will briefly stop,
12540 collect some data, and then allow the program to continue. Setting a tracepoint
12541 or changing its actions takes effect immediately if the remote stub
12542 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12544 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12545 these changes don't take effect until the next @code{tstart}
12546 command, and once a trace experiment is running, further changes will
12547 not have any effect until the next trace experiment starts. In addition,
12548 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12549 address is not yet resolved. (This is similar to pending breakpoints.)
12550 Pending tracepoints are not downloaded to the target and not installed
12551 until they are resolved. The resolution of pending tracepoints requires
12552 @value{GDBN} support---when debugging with the remote target, and
12553 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12554 tracing}), pending tracepoints can not be resolved (and downloaded to
12555 the remote stub) while @value{GDBN} is disconnected.
12557 Here are some examples of using the @code{trace} command:
12560 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12562 (@value{GDBP}) @b{trace +2} // 2 lines forward
12564 (@value{GDBP}) @b{trace my_function} // first source line of function
12566 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12568 (@value{GDBP}) @b{trace *0x2117c4} // an address
12572 You can abbreviate @code{trace} as @code{tr}.
12574 @item trace @var{location} if @var{cond}
12575 Set a tracepoint with condition @var{cond}; evaluate the expression
12576 @var{cond} each time the tracepoint is reached, and collect data only
12577 if the value is nonzero---that is, if @var{cond} evaluates as true.
12578 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12579 information on tracepoint conditions.
12581 @item ftrace @var{location} [ if @var{cond} ]
12582 @cindex set fast tracepoint
12583 @cindex fast tracepoints, setting
12585 The @code{ftrace} command sets a fast tracepoint. For targets that
12586 support them, fast tracepoints will use a more efficient but possibly
12587 less general technique to trigger data collection, such as a jump
12588 instruction instead of a trap, or some sort of hardware support. It
12589 may not be possible to create a fast tracepoint at the desired
12590 location, in which case the command will exit with an explanatory
12593 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12596 On 32-bit x86-architecture systems, fast tracepoints normally need to
12597 be placed at an instruction that is 5 bytes or longer, but can be
12598 placed at 4-byte instructions if the low 64K of memory of the target
12599 program is available to install trampolines. Some Unix-type systems,
12600 such as @sc{gnu}/Linux, exclude low addresses from the program's
12601 address space; but for instance with the Linux kernel it is possible
12602 to let @value{GDBN} use this area by doing a @command{sysctl} command
12603 to set the @code{mmap_min_addr} kernel parameter, as in
12606 sudo sysctl -w vm.mmap_min_addr=32768
12610 which sets the low address to 32K, which leaves plenty of room for
12611 trampolines. The minimum address should be set to a page boundary.
12613 @item strace @var{location} [ if @var{cond} ]
12614 @cindex set static tracepoint
12615 @cindex static tracepoints, setting
12616 @cindex probe static tracepoint marker
12618 The @code{strace} command sets a static tracepoint. For targets that
12619 support it, setting a static tracepoint probes a static
12620 instrumentation point, or marker, found at @var{location}. It may not
12621 be possible to set a static tracepoint at the desired location, in
12622 which case the command will exit with an explanatory message.
12624 @value{GDBN} handles arguments to @code{strace} exactly as for
12625 @code{trace}, with the addition that the user can also specify
12626 @code{-m @var{marker}} as @var{location}. This probes the marker
12627 identified by the @var{marker} string identifier. This identifier
12628 depends on the static tracepoint backend library your program is
12629 using. You can find all the marker identifiers in the @samp{ID} field
12630 of the @code{info static-tracepoint-markers} command output.
12631 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12632 Markers}. For example, in the following small program using the UST
12638 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12643 the marker id is composed of joining the first two arguments to the
12644 @code{trace_mark} call with a slash, which translates to:
12647 (@value{GDBP}) info static-tracepoint-markers
12648 Cnt Enb ID Address What
12649 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12655 so you may probe the marker above with:
12658 (@value{GDBP}) strace -m ust/bar33
12661 Static tracepoints accept an extra collect action --- @code{collect
12662 $_sdata}. This collects arbitrary user data passed in the probe point
12663 call to the tracing library. In the UST example above, you'll see
12664 that the third argument to @code{trace_mark} is a printf-like format
12665 string. The user data is then the result of running that formating
12666 string against the following arguments. Note that @code{info
12667 static-tracepoint-markers} command output lists that format string in
12668 the @samp{Data:} field.
12670 You can inspect this data when analyzing the trace buffer, by printing
12671 the $_sdata variable like any other variable available to
12672 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12675 @cindex last tracepoint number
12676 @cindex recent tracepoint number
12677 @cindex tracepoint number
12678 The convenience variable @code{$tpnum} records the tracepoint number
12679 of the most recently set tracepoint.
12681 @kindex delete tracepoint
12682 @cindex tracepoint deletion
12683 @item delete tracepoint @r{[}@var{num}@r{]}
12684 Permanently delete one or more tracepoints. With no argument, the
12685 default is to delete all tracepoints. Note that the regular
12686 @code{delete} command can remove tracepoints also.
12691 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12693 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12697 You can abbreviate this command as @code{del tr}.
12700 @node Enable and Disable Tracepoints
12701 @subsection Enable and Disable Tracepoints
12703 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12706 @kindex disable tracepoint
12707 @item disable tracepoint @r{[}@var{num}@r{]}
12708 Disable tracepoint @var{num}, or all tracepoints if no argument
12709 @var{num} is given. A disabled tracepoint will have no effect during
12710 a trace experiment, but it is not forgotten. You can re-enable
12711 a disabled tracepoint using the @code{enable tracepoint} command.
12712 If the command is issued during a trace experiment and the debug target
12713 has support for disabling tracepoints during a trace experiment, then the
12714 change will be effective immediately. Otherwise, it will be applied to the
12715 next trace experiment.
12717 @kindex enable tracepoint
12718 @item enable tracepoint @r{[}@var{num}@r{]}
12719 Enable tracepoint @var{num}, or all tracepoints. If this command is
12720 issued during a trace experiment and the debug target supports enabling
12721 tracepoints during a trace experiment, then the enabled tracepoints will
12722 become effective immediately. Otherwise, they will become effective the
12723 next time a trace experiment is run.
12726 @node Tracepoint Passcounts
12727 @subsection Tracepoint Passcounts
12731 @cindex tracepoint pass count
12732 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12733 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12734 automatically stop a trace experiment. If a tracepoint's passcount is
12735 @var{n}, then the trace experiment will be automatically stopped on
12736 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12737 @var{num} is not specified, the @code{passcount} command sets the
12738 passcount of the most recently defined tracepoint. If no passcount is
12739 given, the trace experiment will run until stopped explicitly by the
12745 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12746 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12748 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12749 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12750 (@value{GDBP}) @b{trace foo}
12751 (@value{GDBP}) @b{pass 3}
12752 (@value{GDBP}) @b{trace bar}
12753 (@value{GDBP}) @b{pass 2}
12754 (@value{GDBP}) @b{trace baz}
12755 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12756 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12757 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12758 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12762 @node Tracepoint Conditions
12763 @subsection Tracepoint Conditions
12764 @cindex conditional tracepoints
12765 @cindex tracepoint conditions
12767 The simplest sort of tracepoint collects data every time your program
12768 reaches a specified place. You can also specify a @dfn{condition} for
12769 a tracepoint. A condition is just a Boolean expression in your
12770 programming language (@pxref{Expressions, ,Expressions}). A
12771 tracepoint with a condition evaluates the expression each time your
12772 program reaches it, and data collection happens only if the condition
12775 Tracepoint conditions can be specified when a tracepoint is set, by
12776 using @samp{if} in the arguments to the @code{trace} command.
12777 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12778 also be set or changed at any time with the @code{condition} command,
12779 just as with breakpoints.
12781 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12782 the conditional expression itself. Instead, @value{GDBN} encodes the
12783 expression into an agent expression (@pxref{Agent Expressions})
12784 suitable for execution on the target, independently of @value{GDBN}.
12785 Global variables become raw memory locations, locals become stack
12786 accesses, and so forth.
12788 For instance, suppose you have a function that is usually called
12789 frequently, but should not be called after an error has occurred. You
12790 could use the following tracepoint command to collect data about calls
12791 of that function that happen while the error code is propagating
12792 through the program; an unconditional tracepoint could end up
12793 collecting thousands of useless trace frames that you would have to
12797 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12800 @node Trace State Variables
12801 @subsection Trace State Variables
12802 @cindex trace state variables
12804 A @dfn{trace state variable} is a special type of variable that is
12805 created and managed by target-side code. The syntax is the same as
12806 that for GDB's convenience variables (a string prefixed with ``$''),
12807 but they are stored on the target. They must be created explicitly,
12808 using a @code{tvariable} command. They are always 64-bit signed
12811 Trace state variables are remembered by @value{GDBN}, and downloaded
12812 to the target along with tracepoint information when the trace
12813 experiment starts. There are no intrinsic limits on the number of
12814 trace state variables, beyond memory limitations of the target.
12816 @cindex convenience variables, and trace state variables
12817 Although trace state variables are managed by the target, you can use
12818 them in print commands and expressions as if they were convenience
12819 variables; @value{GDBN} will get the current value from the target
12820 while the trace experiment is running. Trace state variables share
12821 the same namespace as other ``$'' variables, which means that you
12822 cannot have trace state variables with names like @code{$23} or
12823 @code{$pc}, nor can you have a trace state variable and a convenience
12824 variable with the same name.
12828 @item tvariable $@var{name} [ = @var{expression} ]
12830 The @code{tvariable} command creates a new trace state variable named
12831 @code{$@var{name}}, and optionally gives it an initial value of
12832 @var{expression}. The @var{expression} is evaluated when this command is
12833 entered; the result will be converted to an integer if possible,
12834 otherwise @value{GDBN} will report an error. A subsequent
12835 @code{tvariable} command specifying the same name does not create a
12836 variable, but instead assigns the supplied initial value to the
12837 existing variable of that name, overwriting any previous initial
12838 value. The default initial value is 0.
12840 @item info tvariables
12841 @kindex info tvariables
12842 List all the trace state variables along with their initial values.
12843 Their current values may also be displayed, if the trace experiment is
12846 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12847 @kindex delete tvariable
12848 Delete the given trace state variables, or all of them if no arguments
12853 @node Tracepoint Actions
12854 @subsection Tracepoint Action Lists
12858 @cindex tracepoint actions
12859 @item actions @r{[}@var{num}@r{]}
12860 This command will prompt for a list of actions to be taken when the
12861 tracepoint is hit. If the tracepoint number @var{num} is not
12862 specified, this command sets the actions for the one that was most
12863 recently defined (so that you can define a tracepoint and then say
12864 @code{actions} without bothering about its number). You specify the
12865 actions themselves on the following lines, one action at a time, and
12866 terminate the actions list with a line containing just @code{end}. So
12867 far, the only defined actions are @code{collect}, @code{teval}, and
12868 @code{while-stepping}.
12870 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12871 Commands, ,Breakpoint Command Lists}), except that only the defined
12872 actions are allowed; any other @value{GDBN} command is rejected.
12874 @cindex remove actions from a tracepoint
12875 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12876 and follow it immediately with @samp{end}.
12879 (@value{GDBP}) @b{collect @var{data}} // collect some data
12881 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12883 (@value{GDBP}) @b{end} // signals the end of actions.
12886 In the following example, the action list begins with @code{collect}
12887 commands indicating the things to be collected when the tracepoint is
12888 hit. Then, in order to single-step and collect additional data
12889 following the tracepoint, a @code{while-stepping} command is used,
12890 followed by the list of things to be collected after each step in a
12891 sequence of single steps. The @code{while-stepping} command is
12892 terminated by its own separate @code{end} command. Lastly, the action
12893 list is terminated by an @code{end} command.
12896 (@value{GDBP}) @b{trace foo}
12897 (@value{GDBP}) @b{actions}
12898 Enter actions for tracepoint 1, one per line:
12901 > while-stepping 12
12902 > collect $pc, arr[i]
12907 @kindex collect @r{(tracepoints)}
12908 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12909 Collect values of the given expressions when the tracepoint is hit.
12910 This command accepts a comma-separated list of any valid expressions.
12911 In addition to global, static, or local variables, the following
12912 special arguments are supported:
12916 Collect all registers.
12919 Collect all function arguments.
12922 Collect all local variables.
12925 Collect the return address. This is helpful if you want to see more
12928 @emph{Note:} The return address location can not always be reliably
12929 determined up front, and the wrong address / registers may end up
12930 collected instead. On some architectures the reliability is higher
12931 for tracepoints at function entry, while on others it's the opposite.
12932 When this happens, backtracing will stop because the return address is
12933 found unavailable (unless another collect rule happened to match it).
12936 Collects the number of arguments from the static probe at which the
12937 tracepoint is located.
12938 @xref{Static Probe Points}.
12940 @item $_probe_arg@var{n}
12941 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12942 from the static probe at which the tracepoint is located.
12943 @xref{Static Probe Points}.
12946 @vindex $_sdata@r{, collect}
12947 Collect static tracepoint marker specific data. Only available for
12948 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12949 Lists}. On the UST static tracepoints library backend, an
12950 instrumentation point resembles a @code{printf} function call. The
12951 tracing library is able to collect user specified data formatted to a
12952 character string using the format provided by the programmer that
12953 instrumented the program. Other backends have similar mechanisms.
12954 Here's an example of a UST marker call:
12957 const char master_name[] = "$your_name";
12958 trace_mark(channel1, marker1, "hello %s", master_name)
12961 In this case, collecting @code{$_sdata} collects the string
12962 @samp{hello $yourname}. When analyzing the trace buffer, you can
12963 inspect @samp{$_sdata} like any other variable available to
12967 You can give several consecutive @code{collect} commands, each one
12968 with a single argument, or one @code{collect} command with several
12969 arguments separated by commas; the effect is the same.
12971 The optional @var{mods} changes the usual handling of the arguments.
12972 @code{s} requests that pointers to chars be handled as strings, in
12973 particular collecting the contents of the memory being pointed at, up
12974 to the first zero. The upper bound is by default the value of the
12975 @code{print elements} variable; if @code{s} is followed by a decimal
12976 number, that is the upper bound instead. So for instance
12977 @samp{collect/s25 mystr} collects as many as 25 characters at
12980 The command @code{info scope} (@pxref{Symbols, info scope}) is
12981 particularly useful for figuring out what data to collect.
12983 @kindex teval @r{(tracepoints)}
12984 @item teval @var{expr1}, @var{expr2}, @dots{}
12985 Evaluate the given expressions when the tracepoint is hit. This
12986 command accepts a comma-separated list of expressions. The results
12987 are discarded, so this is mainly useful for assigning values to trace
12988 state variables (@pxref{Trace State Variables}) without adding those
12989 values to the trace buffer, as would be the case if the @code{collect}
12992 @kindex while-stepping @r{(tracepoints)}
12993 @item while-stepping @var{n}
12994 Perform @var{n} single-step instruction traces after the tracepoint,
12995 collecting new data after each step. The @code{while-stepping}
12996 command is followed by the list of what to collect while stepping
12997 (followed by its own @code{end} command):
13000 > while-stepping 12
13001 > collect $regs, myglobal
13007 Note that @code{$pc} is not automatically collected by
13008 @code{while-stepping}; you need to explicitly collect that register if
13009 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13012 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13013 @kindex set default-collect
13014 @cindex default collection action
13015 This variable is a list of expressions to collect at each tracepoint
13016 hit. It is effectively an additional @code{collect} action prepended
13017 to every tracepoint action list. The expressions are parsed
13018 individually for each tracepoint, so for instance a variable named
13019 @code{xyz} may be interpreted as a global for one tracepoint, and a
13020 local for another, as appropriate to the tracepoint's location.
13022 @item show default-collect
13023 @kindex show default-collect
13024 Show the list of expressions that are collected by default at each
13029 @node Listing Tracepoints
13030 @subsection Listing Tracepoints
13033 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13034 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13035 @cindex information about tracepoints
13036 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13037 Display information about the tracepoint @var{num}. If you don't
13038 specify a tracepoint number, displays information about all the
13039 tracepoints defined so far. The format is similar to that used for
13040 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13041 command, simply restricting itself to tracepoints.
13043 A tracepoint's listing may include additional information specific to
13048 its passcount as given by the @code{passcount @var{n}} command
13051 the state about installed on target of each location
13055 (@value{GDBP}) @b{info trace}
13056 Num Type Disp Enb Address What
13057 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13059 collect globfoo, $regs
13064 2 tracepoint keep y <MULTIPLE>
13066 2.1 y 0x0804859c in func4 at change-loc.h:35
13067 installed on target
13068 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13069 installed on target
13070 2.3 y <PENDING> set_tracepoint
13071 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13072 not installed on target
13077 This command can be abbreviated @code{info tp}.
13080 @node Listing Static Tracepoint Markers
13081 @subsection Listing Static Tracepoint Markers
13084 @kindex info static-tracepoint-markers
13085 @cindex information about static tracepoint markers
13086 @item info static-tracepoint-markers
13087 Display information about all static tracepoint markers defined in the
13090 For each marker, the following columns are printed:
13094 An incrementing counter, output to help readability. This is not a
13097 The marker ID, as reported by the target.
13098 @item Enabled or Disabled
13099 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13100 that are not enabled.
13102 Where the marker is in your program, as a memory address.
13104 Where the marker is in the source for your program, as a file and line
13105 number. If the debug information included in the program does not
13106 allow @value{GDBN} to locate the source of the marker, this column
13107 will be left blank.
13111 In addition, the following information may be printed for each marker:
13115 User data passed to the tracing library by the marker call. In the
13116 UST backend, this is the format string passed as argument to the
13118 @item Static tracepoints probing the marker
13119 The list of static tracepoints attached to the marker.
13123 (@value{GDBP}) info static-tracepoint-markers
13124 Cnt ID Enb Address What
13125 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13126 Data: number1 %d number2 %d
13127 Probed by static tracepoints: #2
13128 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13134 @node Starting and Stopping Trace Experiments
13135 @subsection Starting and Stopping Trace Experiments
13138 @kindex tstart [ @var{notes} ]
13139 @cindex start a new trace experiment
13140 @cindex collected data discarded
13142 This command starts the trace experiment, and begins collecting data.
13143 It has the side effect of discarding all the data collected in the
13144 trace buffer during the previous trace experiment. If any arguments
13145 are supplied, they are taken as a note and stored with the trace
13146 experiment's state. The notes may be arbitrary text, and are
13147 especially useful with disconnected tracing in a multi-user context;
13148 the notes can explain what the trace is doing, supply user contact
13149 information, and so forth.
13151 @kindex tstop [ @var{notes} ]
13152 @cindex stop a running trace experiment
13154 This command stops the trace experiment. If any arguments are
13155 supplied, they are recorded with the experiment as a note. This is
13156 useful if you are stopping a trace started by someone else, for
13157 instance if the trace is interfering with the system's behavior and
13158 needs to be stopped quickly.
13160 @strong{Note}: a trace experiment and data collection may stop
13161 automatically if any tracepoint's passcount is reached
13162 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13165 @cindex status of trace data collection
13166 @cindex trace experiment, status of
13168 This command displays the status of the current trace data
13172 Here is an example of the commands we described so far:
13175 (@value{GDBP}) @b{trace gdb_c_test}
13176 (@value{GDBP}) @b{actions}
13177 Enter actions for tracepoint #1, one per line.
13178 > collect $regs,$locals,$args
13179 > while-stepping 11
13183 (@value{GDBP}) @b{tstart}
13184 [time passes @dots{}]
13185 (@value{GDBP}) @b{tstop}
13188 @anchor{disconnected tracing}
13189 @cindex disconnected tracing
13190 You can choose to continue running the trace experiment even if
13191 @value{GDBN} disconnects from the target, voluntarily or
13192 involuntarily. For commands such as @code{detach}, the debugger will
13193 ask what you want to do with the trace. But for unexpected
13194 terminations (@value{GDBN} crash, network outage), it would be
13195 unfortunate to lose hard-won trace data, so the variable
13196 @code{disconnected-tracing} lets you decide whether the trace should
13197 continue running without @value{GDBN}.
13200 @item set disconnected-tracing on
13201 @itemx set disconnected-tracing off
13202 @kindex set disconnected-tracing
13203 Choose whether a tracing run should continue to run if @value{GDBN}
13204 has disconnected from the target. Note that @code{detach} or
13205 @code{quit} will ask you directly what to do about a running trace no
13206 matter what this variable's setting, so the variable is mainly useful
13207 for handling unexpected situations, such as loss of the network.
13209 @item show disconnected-tracing
13210 @kindex show disconnected-tracing
13211 Show the current choice for disconnected tracing.
13215 When you reconnect to the target, the trace experiment may or may not
13216 still be running; it might have filled the trace buffer in the
13217 meantime, or stopped for one of the other reasons. If it is running,
13218 it will continue after reconnection.
13220 Upon reconnection, the target will upload information about the
13221 tracepoints in effect. @value{GDBN} will then compare that
13222 information to the set of tracepoints currently defined, and attempt
13223 to match them up, allowing for the possibility that the numbers may
13224 have changed due to creation and deletion in the meantime. If one of
13225 the target's tracepoints does not match any in @value{GDBN}, the
13226 debugger will create a new tracepoint, so that you have a number with
13227 which to specify that tracepoint. This matching-up process is
13228 necessarily heuristic, and it may result in useless tracepoints being
13229 created; you may simply delete them if they are of no use.
13231 @cindex circular trace buffer
13232 If your target agent supports a @dfn{circular trace buffer}, then you
13233 can run a trace experiment indefinitely without filling the trace
13234 buffer; when space runs out, the agent deletes already-collected trace
13235 frames, oldest first, until there is enough room to continue
13236 collecting. This is especially useful if your tracepoints are being
13237 hit too often, and your trace gets terminated prematurely because the
13238 buffer is full. To ask for a circular trace buffer, simply set
13239 @samp{circular-trace-buffer} to on. You can set this at any time,
13240 including during tracing; if the agent can do it, it will change
13241 buffer handling on the fly, otherwise it will not take effect until
13245 @item set circular-trace-buffer on
13246 @itemx set circular-trace-buffer off
13247 @kindex set circular-trace-buffer
13248 Choose whether a tracing run should use a linear or circular buffer
13249 for trace data. A linear buffer will not lose any trace data, but may
13250 fill up prematurely, while a circular buffer will discard old trace
13251 data, but it will have always room for the latest tracepoint hits.
13253 @item show circular-trace-buffer
13254 @kindex show circular-trace-buffer
13255 Show the current choice for the trace buffer. Note that this may not
13256 match the agent's current buffer handling, nor is it guaranteed to
13257 match the setting that might have been in effect during a past run,
13258 for instance if you are looking at frames from a trace file.
13263 @item set trace-buffer-size @var{n}
13264 @itemx set trace-buffer-size unlimited
13265 @kindex set trace-buffer-size
13266 Request that the target use a trace buffer of @var{n} bytes. Not all
13267 targets will honor the request; they may have a compiled-in size for
13268 the trace buffer, or some other limitation. Set to a value of
13269 @code{unlimited} or @code{-1} to let the target use whatever size it
13270 likes. This is also the default.
13272 @item show trace-buffer-size
13273 @kindex show trace-buffer-size
13274 Show the current requested size for the trace buffer. Note that this
13275 will only match the actual size if the target supports size-setting,
13276 and was able to handle the requested size. For instance, if the
13277 target can only change buffer size between runs, this variable will
13278 not reflect the change until the next run starts. Use @code{tstatus}
13279 to get a report of the actual buffer size.
13283 @item set trace-user @var{text}
13284 @kindex set trace-user
13286 @item show trace-user
13287 @kindex show trace-user
13289 @item set trace-notes @var{text}
13290 @kindex set trace-notes
13291 Set the trace run's notes.
13293 @item show trace-notes
13294 @kindex show trace-notes
13295 Show the trace run's notes.
13297 @item set trace-stop-notes @var{text}
13298 @kindex set trace-stop-notes
13299 Set the trace run's stop notes. The handling of the note is as for
13300 @code{tstop} arguments; the set command is convenient way to fix a
13301 stop note that is mistaken or incomplete.
13303 @item show trace-stop-notes
13304 @kindex show trace-stop-notes
13305 Show the trace run's stop notes.
13309 @node Tracepoint Restrictions
13310 @subsection Tracepoint Restrictions
13312 @cindex tracepoint restrictions
13313 There are a number of restrictions on the use of tracepoints. As
13314 described above, tracepoint data gathering occurs on the target
13315 without interaction from @value{GDBN}. Thus the full capabilities of
13316 the debugger are not available during data gathering, and then at data
13317 examination time, you will be limited by only having what was
13318 collected. The following items describe some common problems, but it
13319 is not exhaustive, and you may run into additional difficulties not
13325 Tracepoint expressions are intended to gather objects (lvalues). Thus
13326 the full flexibility of GDB's expression evaluator is not available.
13327 You cannot call functions, cast objects to aggregate types, access
13328 convenience variables or modify values (except by assignment to trace
13329 state variables). Some language features may implicitly call
13330 functions (for instance Objective-C fields with accessors), and therefore
13331 cannot be collected either.
13334 Collection of local variables, either individually or in bulk with
13335 @code{$locals} or @code{$args}, during @code{while-stepping} may
13336 behave erratically. The stepping action may enter a new scope (for
13337 instance by stepping into a function), or the location of the variable
13338 may change (for instance it is loaded into a register). The
13339 tracepoint data recorded uses the location information for the
13340 variables that is correct for the tracepoint location. When the
13341 tracepoint is created, it is not possible, in general, to determine
13342 where the steps of a @code{while-stepping} sequence will advance the
13343 program---particularly if a conditional branch is stepped.
13346 Collection of an incompletely-initialized or partially-destroyed object
13347 may result in something that @value{GDBN} cannot display, or displays
13348 in a misleading way.
13351 When @value{GDBN} displays a pointer to character it automatically
13352 dereferences the pointer to also display characters of the string
13353 being pointed to. However, collecting the pointer during tracing does
13354 not automatically collect the string. You need to explicitly
13355 dereference the pointer and provide size information if you want to
13356 collect not only the pointer, but the memory pointed to. For example,
13357 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13361 It is not possible to collect a complete stack backtrace at a
13362 tracepoint. Instead, you may collect the registers and a few hundred
13363 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13364 (adjust to use the name of the actual stack pointer register on your
13365 target architecture, and the amount of stack you wish to capture).
13366 Then the @code{backtrace} command will show a partial backtrace when
13367 using a trace frame. The number of stack frames that can be examined
13368 depends on the sizes of the frames in the collected stack. Note that
13369 if you ask for a block so large that it goes past the bottom of the
13370 stack, the target agent may report an error trying to read from an
13374 If you do not collect registers at a tracepoint, @value{GDBN} can
13375 infer that the value of @code{$pc} must be the same as the address of
13376 the tracepoint and use that when you are looking at a trace frame
13377 for that tracepoint. However, this cannot work if the tracepoint has
13378 multiple locations (for instance if it was set in a function that was
13379 inlined), or if it has a @code{while-stepping} loop. In those cases
13380 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13385 @node Analyze Collected Data
13386 @section Using the Collected Data
13388 After the tracepoint experiment ends, you use @value{GDBN} commands
13389 for examining the trace data. The basic idea is that each tracepoint
13390 collects a trace @dfn{snapshot} every time it is hit and another
13391 snapshot every time it single-steps. All these snapshots are
13392 consecutively numbered from zero and go into a buffer, and you can
13393 examine them later. The way you examine them is to @dfn{focus} on a
13394 specific trace snapshot. When the remote stub is focused on a trace
13395 snapshot, it will respond to all @value{GDBN} requests for memory and
13396 registers by reading from the buffer which belongs to that snapshot,
13397 rather than from @emph{real} memory or registers of the program being
13398 debugged. This means that @strong{all} @value{GDBN} commands
13399 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13400 behave as if we were currently debugging the program state as it was
13401 when the tracepoint occurred. Any requests for data that are not in
13402 the buffer will fail.
13405 * tfind:: How to select a trace snapshot
13406 * tdump:: How to display all data for a snapshot
13407 * save tracepoints:: How to save tracepoints for a future run
13411 @subsection @code{tfind @var{n}}
13414 @cindex select trace snapshot
13415 @cindex find trace snapshot
13416 The basic command for selecting a trace snapshot from the buffer is
13417 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13418 counting from zero. If no argument @var{n} is given, the next
13419 snapshot is selected.
13421 Here are the various forms of using the @code{tfind} command.
13425 Find the first snapshot in the buffer. This is a synonym for
13426 @code{tfind 0} (since 0 is the number of the first snapshot).
13429 Stop debugging trace snapshots, resume @emph{live} debugging.
13432 Same as @samp{tfind none}.
13435 No argument means find the next trace snapshot or find the first
13436 one if no trace snapshot is selected.
13439 Find the previous trace snapshot before the current one. This permits
13440 retracing earlier steps.
13442 @item tfind tracepoint @var{num}
13443 Find the next snapshot associated with tracepoint @var{num}. Search
13444 proceeds forward from the last examined trace snapshot. If no
13445 argument @var{num} is given, it means find the next snapshot collected
13446 for the same tracepoint as the current snapshot.
13448 @item tfind pc @var{addr}
13449 Find the next snapshot associated with the value @var{addr} of the
13450 program counter. Search proceeds forward from the last examined trace
13451 snapshot. If no argument @var{addr} is given, it means find the next
13452 snapshot with the same value of PC as the current snapshot.
13454 @item tfind outside @var{addr1}, @var{addr2}
13455 Find the next snapshot whose PC is outside the given range of
13456 addresses (exclusive).
13458 @item tfind range @var{addr1}, @var{addr2}
13459 Find the next snapshot whose PC is between @var{addr1} and
13460 @var{addr2} (inclusive).
13462 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13463 Find the next snapshot associated with the source line @var{n}. If
13464 the optional argument @var{file} is given, refer to line @var{n} in
13465 that source file. Search proceeds forward from the last examined
13466 trace snapshot. If no argument @var{n} is given, it means find the
13467 next line other than the one currently being examined; thus saying
13468 @code{tfind line} repeatedly can appear to have the same effect as
13469 stepping from line to line in a @emph{live} debugging session.
13472 The default arguments for the @code{tfind} commands are specifically
13473 designed to make it easy to scan through the trace buffer. For
13474 instance, @code{tfind} with no argument selects the next trace
13475 snapshot, and @code{tfind -} with no argument selects the previous
13476 trace snapshot. So, by giving one @code{tfind} command, and then
13477 simply hitting @key{RET} repeatedly you can examine all the trace
13478 snapshots in order. Or, by saying @code{tfind -} and then hitting
13479 @key{RET} repeatedly you can examine the snapshots in reverse order.
13480 The @code{tfind line} command with no argument selects the snapshot
13481 for the next source line executed. The @code{tfind pc} command with
13482 no argument selects the next snapshot with the same program counter
13483 (PC) as the current frame. The @code{tfind tracepoint} command with
13484 no argument selects the next trace snapshot collected by the same
13485 tracepoint as the current one.
13487 In addition to letting you scan through the trace buffer manually,
13488 these commands make it easy to construct @value{GDBN} scripts that
13489 scan through the trace buffer and print out whatever collected data
13490 you are interested in. Thus, if we want to examine the PC, FP, and SP
13491 registers from each trace frame in the buffer, we can say this:
13494 (@value{GDBP}) @b{tfind start}
13495 (@value{GDBP}) @b{while ($trace_frame != -1)}
13496 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13497 $trace_frame, $pc, $sp, $fp
13501 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13502 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13503 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13504 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13505 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13506 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13507 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13508 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13509 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13510 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13511 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13514 Or, if we want to examine the variable @code{X} at each source line in
13518 (@value{GDBP}) @b{tfind start}
13519 (@value{GDBP}) @b{while ($trace_frame != -1)}
13520 > printf "Frame %d, X == %d\n", $trace_frame, X
13530 @subsection @code{tdump}
13532 @cindex dump all data collected at tracepoint
13533 @cindex tracepoint data, display
13535 This command takes no arguments. It prints all the data collected at
13536 the current trace snapshot.
13539 (@value{GDBP}) @b{trace 444}
13540 (@value{GDBP}) @b{actions}
13541 Enter actions for tracepoint #2, one per line:
13542 > collect $regs, $locals, $args, gdb_long_test
13545 (@value{GDBP}) @b{tstart}
13547 (@value{GDBP}) @b{tfind line 444}
13548 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13550 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13552 (@value{GDBP}) @b{tdump}
13553 Data collected at tracepoint 2, trace frame 1:
13554 d0 0xc4aa0085 -995491707
13558 d4 0x71aea3d 119204413
13561 d7 0x380035 3670069
13562 a0 0x19e24a 1696330
13563 a1 0x3000668 50333288
13565 a3 0x322000 3284992
13566 a4 0x3000698 50333336
13567 a5 0x1ad3cc 1758156
13568 fp 0x30bf3c 0x30bf3c
13569 sp 0x30bf34 0x30bf34
13571 pc 0x20b2c8 0x20b2c8
13575 p = 0x20e5b4 "gdb-test"
13582 gdb_long_test = 17 '\021'
13587 @code{tdump} works by scanning the tracepoint's current collection
13588 actions and printing the value of each expression listed. So
13589 @code{tdump} can fail, if after a run, you change the tracepoint's
13590 actions to mention variables that were not collected during the run.
13592 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13593 uses the collected value of @code{$pc} to distinguish between trace
13594 frames that were collected at the tracepoint hit, and frames that were
13595 collected while stepping. This allows it to correctly choose whether
13596 to display the basic list of collections, or the collections from the
13597 body of the while-stepping loop. However, if @code{$pc} was not collected,
13598 then @code{tdump} will always attempt to dump using the basic collection
13599 list, and may fail if a while-stepping frame does not include all the
13600 same data that is collected at the tracepoint hit.
13601 @c This is getting pretty arcane, example would be good.
13603 @node save tracepoints
13604 @subsection @code{save tracepoints @var{filename}}
13605 @kindex save tracepoints
13606 @kindex save-tracepoints
13607 @cindex save tracepoints for future sessions
13609 This command saves all current tracepoint definitions together with
13610 their actions and passcounts, into a file @file{@var{filename}}
13611 suitable for use in a later debugging session. To read the saved
13612 tracepoint definitions, use the @code{source} command (@pxref{Command
13613 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13614 alias for @w{@code{save tracepoints}}
13616 @node Tracepoint Variables
13617 @section Convenience Variables for Tracepoints
13618 @cindex tracepoint variables
13619 @cindex convenience variables for tracepoints
13622 @vindex $trace_frame
13623 @item (int) $trace_frame
13624 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13625 snapshot is selected.
13627 @vindex $tracepoint
13628 @item (int) $tracepoint
13629 The tracepoint for the current trace snapshot.
13631 @vindex $trace_line
13632 @item (int) $trace_line
13633 The line number for the current trace snapshot.
13635 @vindex $trace_file
13636 @item (char []) $trace_file
13637 The source file for the current trace snapshot.
13639 @vindex $trace_func
13640 @item (char []) $trace_func
13641 The name of the function containing @code{$tracepoint}.
13644 Note: @code{$trace_file} is not suitable for use in @code{printf},
13645 use @code{output} instead.
13647 Here's a simple example of using these convenience variables for
13648 stepping through all the trace snapshots and printing some of their
13649 data. Note that these are not the same as trace state variables,
13650 which are managed by the target.
13653 (@value{GDBP}) @b{tfind start}
13655 (@value{GDBP}) @b{while $trace_frame != -1}
13656 > output $trace_file
13657 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13663 @section Using Trace Files
13664 @cindex trace files
13666 In some situations, the target running a trace experiment may no
13667 longer be available; perhaps it crashed, or the hardware was needed
13668 for a different activity. To handle these cases, you can arrange to
13669 dump the trace data into a file, and later use that file as a source
13670 of trace data, via the @code{target tfile} command.
13675 @item tsave [ -r ] @var{filename}
13676 @itemx tsave [-ctf] @var{dirname}
13677 Save the trace data to @var{filename}. By default, this command
13678 assumes that @var{filename} refers to the host filesystem, so if
13679 necessary @value{GDBN} will copy raw trace data up from the target and
13680 then save it. If the target supports it, you can also supply the
13681 optional argument @code{-r} (``remote'') to direct the target to save
13682 the data directly into @var{filename} in its own filesystem, which may be
13683 more efficient if the trace buffer is very large. (Note, however, that
13684 @code{target tfile} can only read from files accessible to the host.)
13685 By default, this command will save trace frame in tfile format.
13686 You can supply the optional argument @code{-ctf} to save data in CTF
13687 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13688 that can be shared by multiple debugging and tracing tools. Please go to
13689 @indicateurl{http://www.efficios.com/ctf} to get more information.
13691 @kindex target tfile
13695 @item target tfile @var{filename}
13696 @itemx target ctf @var{dirname}
13697 Use the file named @var{filename} or directory named @var{dirname} as
13698 a source of trace data. Commands that examine data work as they do with
13699 a live target, but it is not possible to run any new trace experiments.
13700 @code{tstatus} will report the state of the trace run at the moment
13701 the data was saved, as well as the current trace frame you are examining.
13702 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13706 (@value{GDBP}) target ctf ctf.ctf
13707 (@value{GDBP}) tfind
13708 Found trace frame 0, tracepoint 2
13709 39 ++a; /* set tracepoint 1 here */
13710 (@value{GDBP}) tdump
13711 Data collected at tracepoint 2, trace frame 0:
13715 c = @{"123", "456", "789", "123", "456", "789"@}
13716 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13724 @chapter Debugging Programs That Use Overlays
13727 If your program is too large to fit completely in your target system's
13728 memory, you can sometimes use @dfn{overlays} to work around this
13729 problem. @value{GDBN} provides some support for debugging programs that
13733 * How Overlays Work:: A general explanation of overlays.
13734 * Overlay Commands:: Managing overlays in @value{GDBN}.
13735 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13736 mapped by asking the inferior.
13737 * Overlay Sample Program:: A sample program using overlays.
13740 @node How Overlays Work
13741 @section How Overlays Work
13742 @cindex mapped overlays
13743 @cindex unmapped overlays
13744 @cindex load address, overlay's
13745 @cindex mapped address
13746 @cindex overlay area
13748 Suppose you have a computer whose instruction address space is only 64
13749 kilobytes long, but which has much more memory which can be accessed by
13750 other means: special instructions, segment registers, or memory
13751 management hardware, for example. Suppose further that you want to
13752 adapt a program which is larger than 64 kilobytes to run on this system.
13754 One solution is to identify modules of your program which are relatively
13755 independent, and need not call each other directly; call these modules
13756 @dfn{overlays}. Separate the overlays from the main program, and place
13757 their machine code in the larger memory. Place your main program in
13758 instruction memory, but leave at least enough space there to hold the
13759 largest overlay as well.
13761 Now, to call a function located in an overlay, you must first copy that
13762 overlay's machine code from the large memory into the space set aside
13763 for it in the instruction memory, and then jump to its entry point
13766 @c NB: In the below the mapped area's size is greater or equal to the
13767 @c size of all overlays. This is intentional to remind the developer
13768 @c that overlays don't necessarily need to be the same size.
13772 Data Instruction Larger
13773 Address Space Address Space Address Space
13774 +-----------+ +-----------+ +-----------+
13776 +-----------+ +-----------+ +-----------+<-- overlay 1
13777 | program | | main | .----| overlay 1 | load address
13778 | variables | | program | | +-----------+
13779 | and heap | | | | | |
13780 +-----------+ | | | +-----------+<-- overlay 2
13781 | | +-----------+ | | | load address
13782 +-----------+ | | | .-| overlay 2 |
13784 mapped --->+-----------+ | | +-----------+
13785 address | | | | | |
13786 | overlay | <-' | | |
13787 | area | <---' +-----------+<-- overlay 3
13788 | | <---. | | load address
13789 +-----------+ `--| overlay 3 |
13796 @anchor{A code overlay}A code overlay
13800 The diagram (@pxref{A code overlay}) shows a system with separate data
13801 and instruction address spaces. To map an overlay, the program copies
13802 its code from the larger address space to the instruction address space.
13803 Since the overlays shown here all use the same mapped address, only one
13804 may be mapped at a time. For a system with a single address space for
13805 data and instructions, the diagram would be similar, except that the
13806 program variables and heap would share an address space with the main
13807 program and the overlay area.
13809 An overlay loaded into instruction memory and ready for use is called a
13810 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13811 instruction memory. An overlay not present (or only partially present)
13812 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13813 is its address in the larger memory. The mapped address is also called
13814 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13815 called the @dfn{load memory address}, or @dfn{LMA}.
13817 Unfortunately, overlays are not a completely transparent way to adapt a
13818 program to limited instruction memory. They introduce a new set of
13819 global constraints you must keep in mind as you design your program:
13824 Before calling or returning to a function in an overlay, your program
13825 must make sure that overlay is actually mapped. Otherwise, the call or
13826 return will transfer control to the right address, but in the wrong
13827 overlay, and your program will probably crash.
13830 If the process of mapping an overlay is expensive on your system, you
13831 will need to choose your overlays carefully to minimize their effect on
13832 your program's performance.
13835 The executable file you load onto your system must contain each
13836 overlay's instructions, appearing at the overlay's load address, not its
13837 mapped address. However, each overlay's instructions must be relocated
13838 and its symbols defined as if the overlay were at its mapped address.
13839 You can use GNU linker scripts to specify different load and relocation
13840 addresses for pieces of your program; see @ref{Overlay Description,,,
13841 ld.info, Using ld: the GNU linker}.
13844 The procedure for loading executable files onto your system must be able
13845 to load their contents into the larger address space as well as the
13846 instruction and data spaces.
13850 The overlay system described above is rather simple, and could be
13851 improved in many ways:
13856 If your system has suitable bank switch registers or memory management
13857 hardware, you could use those facilities to make an overlay's load area
13858 contents simply appear at their mapped address in instruction space.
13859 This would probably be faster than copying the overlay to its mapped
13860 area in the usual way.
13863 If your overlays are small enough, you could set aside more than one
13864 overlay area, and have more than one overlay mapped at a time.
13867 You can use overlays to manage data, as well as instructions. In
13868 general, data overlays are even less transparent to your design than
13869 code overlays: whereas code overlays only require care when you call or
13870 return to functions, data overlays require care every time you access
13871 the data. Also, if you change the contents of a data overlay, you
13872 must copy its contents back out to its load address before you can copy a
13873 different data overlay into the same mapped area.
13878 @node Overlay Commands
13879 @section Overlay Commands
13881 To use @value{GDBN}'s overlay support, each overlay in your program must
13882 correspond to a separate section of the executable file. The section's
13883 virtual memory address and load memory address must be the overlay's
13884 mapped and load addresses. Identifying overlays with sections allows
13885 @value{GDBN} to determine the appropriate address of a function or
13886 variable, depending on whether the overlay is mapped or not.
13888 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13889 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13894 Disable @value{GDBN}'s overlay support. When overlay support is
13895 disabled, @value{GDBN} assumes that all functions and variables are
13896 always present at their mapped addresses. By default, @value{GDBN}'s
13897 overlay support is disabled.
13899 @item overlay manual
13900 @cindex manual overlay debugging
13901 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13902 relies on you to tell it which overlays are mapped, and which are not,
13903 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13904 commands described below.
13906 @item overlay map-overlay @var{overlay}
13907 @itemx overlay map @var{overlay}
13908 @cindex map an overlay
13909 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13910 be the name of the object file section containing the overlay. When an
13911 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13912 functions and variables at their mapped addresses. @value{GDBN} assumes
13913 that any other overlays whose mapped ranges overlap that of
13914 @var{overlay} are now unmapped.
13916 @item overlay unmap-overlay @var{overlay}
13917 @itemx overlay unmap @var{overlay}
13918 @cindex unmap an overlay
13919 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13920 must be the name of the object file section containing the overlay.
13921 When an overlay is unmapped, @value{GDBN} assumes it can find the
13922 overlay's functions and variables at their load addresses.
13925 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13926 consults a data structure the overlay manager maintains in the inferior
13927 to see which overlays are mapped. For details, see @ref{Automatic
13928 Overlay Debugging}.
13930 @item overlay load-target
13931 @itemx overlay load
13932 @cindex reloading the overlay table
13933 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13934 re-reads the table @value{GDBN} automatically each time the inferior
13935 stops, so this command should only be necessary if you have changed the
13936 overlay mapping yourself using @value{GDBN}. This command is only
13937 useful when using automatic overlay debugging.
13939 @item overlay list-overlays
13940 @itemx overlay list
13941 @cindex listing mapped overlays
13942 Display a list of the overlays currently mapped, along with their mapped
13943 addresses, load addresses, and sizes.
13947 Normally, when @value{GDBN} prints a code address, it includes the name
13948 of the function the address falls in:
13951 (@value{GDBP}) print main
13952 $3 = @{int ()@} 0x11a0 <main>
13955 When overlay debugging is enabled, @value{GDBN} recognizes code in
13956 unmapped overlays, and prints the names of unmapped functions with
13957 asterisks around them. For example, if @code{foo} is a function in an
13958 unmapped overlay, @value{GDBN} prints it this way:
13961 (@value{GDBP}) overlay list
13962 No sections are mapped.
13963 (@value{GDBP}) print foo
13964 $5 = @{int (int)@} 0x100000 <*foo*>
13967 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13971 (@value{GDBP}) overlay list
13972 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13973 mapped at 0x1016 - 0x104a
13974 (@value{GDBP}) print foo
13975 $6 = @{int (int)@} 0x1016 <foo>
13978 When overlay debugging is enabled, @value{GDBN} can find the correct
13979 address for functions and variables in an overlay, whether or not the
13980 overlay is mapped. This allows most @value{GDBN} commands, like
13981 @code{break} and @code{disassemble}, to work normally, even on unmapped
13982 code. However, @value{GDBN}'s breakpoint support has some limitations:
13986 @cindex breakpoints in overlays
13987 @cindex overlays, setting breakpoints in
13988 You can set breakpoints in functions in unmapped overlays, as long as
13989 @value{GDBN} can write to the overlay at its load address.
13991 @value{GDBN} can not set hardware or simulator-based breakpoints in
13992 unmapped overlays. However, if you set a breakpoint at the end of your
13993 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13994 you are using manual overlay management), @value{GDBN} will re-set its
13995 breakpoints properly.
13999 @node Automatic Overlay Debugging
14000 @section Automatic Overlay Debugging
14001 @cindex automatic overlay debugging
14003 @value{GDBN} can automatically track which overlays are mapped and which
14004 are not, given some simple co-operation from the overlay manager in the
14005 inferior. If you enable automatic overlay debugging with the
14006 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14007 looks in the inferior's memory for certain variables describing the
14008 current state of the overlays.
14010 Here are the variables your overlay manager must define to support
14011 @value{GDBN}'s automatic overlay debugging:
14015 @item @code{_ovly_table}:
14016 This variable must be an array of the following structures:
14021 /* The overlay's mapped address. */
14024 /* The size of the overlay, in bytes. */
14025 unsigned long size;
14027 /* The overlay's load address. */
14030 /* Non-zero if the overlay is currently mapped;
14032 unsigned long mapped;
14036 @item @code{_novlys}:
14037 This variable must be a four-byte signed integer, holding the total
14038 number of elements in @code{_ovly_table}.
14042 To decide whether a particular overlay is mapped or not, @value{GDBN}
14043 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14044 @code{lma} members equal the VMA and LMA of the overlay's section in the
14045 executable file. When @value{GDBN} finds a matching entry, it consults
14046 the entry's @code{mapped} member to determine whether the overlay is
14049 In addition, your overlay manager may define a function called
14050 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14051 will silently set a breakpoint there. If the overlay manager then
14052 calls this function whenever it has changed the overlay table, this
14053 will enable @value{GDBN} to accurately keep track of which overlays
14054 are in program memory, and update any breakpoints that may be set
14055 in overlays. This will allow breakpoints to work even if the
14056 overlays are kept in ROM or other non-writable memory while they
14057 are not being executed.
14059 @node Overlay Sample Program
14060 @section Overlay Sample Program
14061 @cindex overlay example program
14063 When linking a program which uses overlays, you must place the overlays
14064 at their load addresses, while relocating them to run at their mapped
14065 addresses. To do this, you must write a linker script (@pxref{Overlay
14066 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14067 since linker scripts are specific to a particular host system, target
14068 architecture, and target memory layout, this manual cannot provide
14069 portable sample code demonstrating @value{GDBN}'s overlay support.
14071 However, the @value{GDBN} source distribution does contain an overlaid
14072 program, with linker scripts for a few systems, as part of its test
14073 suite. The program consists of the following files from
14074 @file{gdb/testsuite/gdb.base}:
14078 The main program file.
14080 A simple overlay manager, used by @file{overlays.c}.
14085 Overlay modules, loaded and used by @file{overlays.c}.
14088 Linker scripts for linking the test program on the @code{d10v-elf}
14089 and @code{m32r-elf} targets.
14092 You can build the test program using the @code{d10v-elf} GCC
14093 cross-compiler like this:
14096 $ d10v-elf-gcc -g -c overlays.c
14097 $ d10v-elf-gcc -g -c ovlymgr.c
14098 $ d10v-elf-gcc -g -c foo.c
14099 $ d10v-elf-gcc -g -c bar.c
14100 $ d10v-elf-gcc -g -c baz.c
14101 $ d10v-elf-gcc -g -c grbx.c
14102 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14103 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14106 The build process is identical for any other architecture, except that
14107 you must substitute the appropriate compiler and linker script for the
14108 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14112 @chapter Using @value{GDBN} with Different Languages
14115 Although programming languages generally have common aspects, they are
14116 rarely expressed in the same manner. For instance, in ANSI C,
14117 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14118 Modula-2, it is accomplished by @code{p^}. Values can also be
14119 represented (and displayed) differently. Hex numbers in C appear as
14120 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14122 @cindex working language
14123 Language-specific information is built into @value{GDBN} for some languages,
14124 allowing you to express operations like the above in your program's
14125 native language, and allowing @value{GDBN} to output values in a manner
14126 consistent with the syntax of your program's native language. The
14127 language you use to build expressions is called the @dfn{working
14131 * Setting:: Switching between source languages
14132 * Show:: Displaying the language
14133 * Checks:: Type and range checks
14134 * Supported Languages:: Supported languages
14135 * Unsupported Languages:: Unsupported languages
14139 @section Switching Between Source Languages
14141 There are two ways to control the working language---either have @value{GDBN}
14142 set it automatically, or select it manually yourself. You can use the
14143 @code{set language} command for either purpose. On startup, @value{GDBN}
14144 defaults to setting the language automatically. The working language is
14145 used to determine how expressions you type are interpreted, how values
14148 In addition to the working language, every source file that
14149 @value{GDBN} knows about has its own working language. For some object
14150 file formats, the compiler might indicate which language a particular
14151 source file is in. However, most of the time @value{GDBN} infers the
14152 language from the name of the file. The language of a source file
14153 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14154 show each frame appropriately for its own language. There is no way to
14155 set the language of a source file from within @value{GDBN}, but you can
14156 set the language associated with a filename extension. @xref{Show, ,
14157 Displaying the Language}.
14159 This is most commonly a problem when you use a program, such
14160 as @code{cfront} or @code{f2c}, that generates C but is written in
14161 another language. In that case, make the
14162 program use @code{#line} directives in its C output; that way
14163 @value{GDBN} will know the correct language of the source code of the original
14164 program, and will display that source code, not the generated C code.
14167 * Filenames:: Filename extensions and languages.
14168 * Manually:: Setting the working language manually
14169 * Automatically:: Having @value{GDBN} infer the source language
14173 @subsection List of Filename Extensions and Languages
14175 If a source file name ends in one of the following extensions, then
14176 @value{GDBN} infers that its language is the one indicated.
14194 C@t{++} source file
14200 Objective-C source file
14204 Fortran source file
14207 Modula-2 source file
14211 Assembler source file. This actually behaves almost like C, but
14212 @value{GDBN} does not skip over function prologues when stepping.
14215 In addition, you may set the language associated with a filename
14216 extension. @xref{Show, , Displaying the Language}.
14219 @subsection Setting the Working Language
14221 If you allow @value{GDBN} to set the language automatically,
14222 expressions are interpreted the same way in your debugging session and
14225 @kindex set language
14226 If you wish, you may set the language manually. To do this, issue the
14227 command @samp{set language @var{lang}}, where @var{lang} is the name of
14228 a language, such as
14229 @code{c} or @code{modula-2}.
14230 For a list of the supported languages, type @samp{set language}.
14232 Setting the language manually prevents @value{GDBN} from updating the working
14233 language automatically. This can lead to confusion if you try
14234 to debug a program when the working language is not the same as the
14235 source language, when an expression is acceptable to both
14236 languages---but means different things. For instance, if the current
14237 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14245 might not have the effect you intended. In C, this means to add
14246 @code{b} and @code{c} and place the result in @code{a}. The result
14247 printed would be the value of @code{a}. In Modula-2, this means to compare
14248 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14250 @node Automatically
14251 @subsection Having @value{GDBN} Infer the Source Language
14253 To have @value{GDBN} set the working language automatically, use
14254 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14255 then infers the working language. That is, when your program stops in a
14256 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14257 working language to the language recorded for the function in that
14258 frame. If the language for a frame is unknown (that is, if the function
14259 or block corresponding to the frame was defined in a source file that
14260 does not have a recognized extension), the current working language is
14261 not changed, and @value{GDBN} issues a warning.
14263 This may not seem necessary for most programs, which are written
14264 entirely in one source language. However, program modules and libraries
14265 written in one source language can be used by a main program written in
14266 a different source language. Using @samp{set language auto} in this
14267 case frees you from having to set the working language manually.
14270 @section Displaying the Language
14272 The following commands help you find out which language is the
14273 working language, and also what language source files were written in.
14276 @item show language
14277 @anchor{show language}
14278 @kindex show language
14279 Display the current working language. This is the
14280 language you can use with commands such as @code{print} to
14281 build and compute expressions that may involve variables in your program.
14284 @kindex info frame@r{, show the source language}
14285 Display the source language for this frame. This language becomes the
14286 working language if you use an identifier from this frame.
14287 @xref{Frame Info, ,Information about a Frame}, to identify the other
14288 information listed here.
14291 @kindex info source@r{, show the source language}
14292 Display the source language of this source file.
14293 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14294 information listed here.
14297 In unusual circumstances, you may have source files with extensions
14298 not in the standard list. You can then set the extension associated
14299 with a language explicitly:
14302 @item set extension-language @var{ext} @var{language}
14303 @kindex set extension-language
14304 Tell @value{GDBN} that source files with extension @var{ext} are to be
14305 assumed as written in the source language @var{language}.
14307 @item info extensions
14308 @kindex info extensions
14309 List all the filename extensions and the associated languages.
14313 @section Type and Range Checking
14315 Some languages are designed to guard you against making seemingly common
14316 errors through a series of compile- and run-time checks. These include
14317 checking the type of arguments to functions and operators and making
14318 sure mathematical overflows are caught at run time. Checks such as
14319 these help to ensure a program's correctness once it has been compiled
14320 by eliminating type mismatches and providing active checks for range
14321 errors when your program is running.
14323 By default @value{GDBN} checks for these errors according to the
14324 rules of the current source language. Although @value{GDBN} does not check
14325 the statements in your program, it can check expressions entered directly
14326 into @value{GDBN} for evaluation via the @code{print} command, for example.
14329 * Type Checking:: An overview of type checking
14330 * Range Checking:: An overview of range checking
14333 @cindex type checking
14334 @cindex checks, type
14335 @node Type Checking
14336 @subsection An Overview of Type Checking
14338 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14339 arguments to operators and functions have to be of the correct type,
14340 otherwise an error occurs. These checks prevent type mismatch
14341 errors from ever causing any run-time problems. For example,
14344 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14346 (@value{GDBP}) print obj.my_method (0)
14349 (@value{GDBP}) print obj.my_method (0x1234)
14350 Cannot resolve method klass::my_method to any overloaded instance
14353 The second example fails because in C@t{++} the integer constant
14354 @samp{0x1234} is not type-compatible with the pointer parameter type.
14356 For the expressions you use in @value{GDBN} commands, you can tell
14357 @value{GDBN} to not enforce strict type checking or
14358 to treat any mismatches as errors and abandon the expression;
14359 When type checking is disabled, @value{GDBN} successfully evaluates
14360 expressions like the second example above.
14362 Even if type checking is off, there may be other reasons
14363 related to type that prevent @value{GDBN} from evaluating an expression.
14364 For instance, @value{GDBN} does not know how to add an @code{int} and
14365 a @code{struct foo}. These particular type errors have nothing to do
14366 with the language in use and usually arise from expressions which make
14367 little sense to evaluate anyway.
14369 @value{GDBN} provides some additional commands for controlling type checking:
14371 @kindex set check type
14372 @kindex show check type
14374 @item set check type on
14375 @itemx set check type off
14376 Set strict type checking on or off. If any type mismatches occur in
14377 evaluating an expression while type checking is on, @value{GDBN} prints a
14378 message and aborts evaluation of the expression.
14380 @item show check type
14381 Show the current setting of type checking and whether @value{GDBN}
14382 is enforcing strict type checking rules.
14385 @cindex range checking
14386 @cindex checks, range
14387 @node Range Checking
14388 @subsection An Overview of Range Checking
14390 In some languages (such as Modula-2), it is an error to exceed the
14391 bounds of a type; this is enforced with run-time checks. Such range
14392 checking is meant to ensure program correctness by making sure
14393 computations do not overflow, or indices on an array element access do
14394 not exceed the bounds of the array.
14396 For expressions you use in @value{GDBN} commands, you can tell
14397 @value{GDBN} to treat range errors in one of three ways: ignore them,
14398 always treat them as errors and abandon the expression, or issue
14399 warnings but evaluate the expression anyway.
14401 A range error can result from numerical overflow, from exceeding an
14402 array index bound, or when you type a constant that is not a member
14403 of any type. Some languages, however, do not treat overflows as an
14404 error. In many implementations of C, mathematical overflow causes the
14405 result to ``wrap around'' to lower values---for example, if @var{m} is
14406 the largest integer value, and @var{s} is the smallest, then
14409 @var{m} + 1 @result{} @var{s}
14412 This, too, is specific to individual languages, and in some cases
14413 specific to individual compilers or machines. @xref{Supported Languages, ,
14414 Supported Languages}, for further details on specific languages.
14416 @value{GDBN} provides some additional commands for controlling the range checker:
14418 @kindex set check range
14419 @kindex show check range
14421 @item set check range auto
14422 Set range checking on or off based on the current working language.
14423 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14426 @item set check range on
14427 @itemx set check range off
14428 Set range checking on or off, overriding the default setting for the
14429 current working language. A warning is issued if the setting does not
14430 match the language default. If a range error occurs and range checking is on,
14431 then a message is printed and evaluation of the expression is aborted.
14433 @item set check range warn
14434 Output messages when the @value{GDBN} range checker detects a range error,
14435 but attempt to evaluate the expression anyway. Evaluating the
14436 expression may still be impossible for other reasons, such as accessing
14437 memory that the process does not own (a typical example from many Unix
14441 Show the current setting of the range checker, and whether or not it is
14442 being set automatically by @value{GDBN}.
14445 @node Supported Languages
14446 @section Supported Languages
14448 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14449 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14450 @c This is false ...
14451 Some @value{GDBN} features may be used in expressions regardless of the
14452 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14453 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14454 ,Expressions}) can be used with the constructs of any supported
14457 The following sections detail to what degree each source language is
14458 supported by @value{GDBN}. These sections are not meant to be language
14459 tutorials or references, but serve only as a reference guide to what the
14460 @value{GDBN} expression parser accepts, and what input and output
14461 formats should look like for different languages. There are many good
14462 books written on each of these languages; please look to these for a
14463 language reference or tutorial.
14466 * C:: C and C@t{++}
14469 * Objective-C:: Objective-C
14470 * OpenCL C:: OpenCL C
14471 * Fortran:: Fortran
14474 * Modula-2:: Modula-2
14479 @subsection C and C@t{++}
14481 @cindex C and C@t{++}
14482 @cindex expressions in C or C@t{++}
14484 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14485 to both languages. Whenever this is the case, we discuss those languages
14489 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14490 @cindex @sc{gnu} C@t{++}
14491 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14492 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14493 effectively, you must compile your C@t{++} programs with a supported
14494 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14495 compiler (@code{aCC}).
14498 * C Operators:: C and C@t{++} operators
14499 * C Constants:: C and C@t{++} constants
14500 * C Plus Plus Expressions:: C@t{++} expressions
14501 * C Defaults:: Default settings for C and C@t{++}
14502 * C Checks:: C and C@t{++} type and range checks
14503 * Debugging C:: @value{GDBN} and C
14504 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14505 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14509 @subsubsection C and C@t{++} Operators
14511 @cindex C and C@t{++} operators
14513 Operators must be defined on values of specific types. For instance,
14514 @code{+} is defined on numbers, but not on structures. Operators are
14515 often defined on groups of types.
14517 For the purposes of C and C@t{++}, the following definitions hold:
14522 @emph{Integral types} include @code{int} with any of its storage-class
14523 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14526 @emph{Floating-point types} include @code{float}, @code{double}, and
14527 @code{long double} (if supported by the target platform).
14530 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14533 @emph{Scalar types} include all of the above.
14538 The following operators are supported. They are listed here
14539 in order of increasing precedence:
14543 The comma or sequencing operator. Expressions in a comma-separated list
14544 are evaluated from left to right, with the result of the entire
14545 expression being the last expression evaluated.
14548 Assignment. The value of an assignment expression is the value
14549 assigned. Defined on scalar types.
14552 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14553 and translated to @w{@code{@var{a} = @var{a op b}}}.
14554 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14555 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14556 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14559 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14560 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14561 should be of an integral type.
14564 Logical @sc{or}. Defined on integral types.
14567 Logical @sc{and}. Defined on integral types.
14570 Bitwise @sc{or}. Defined on integral types.
14573 Bitwise exclusive-@sc{or}. Defined on integral types.
14576 Bitwise @sc{and}. Defined on integral types.
14579 Equality and inequality. Defined on scalar types. The value of these
14580 expressions is 0 for false and non-zero for true.
14582 @item <@r{, }>@r{, }<=@r{, }>=
14583 Less than, greater than, less than or equal, greater than or equal.
14584 Defined on scalar types. The value of these expressions is 0 for false
14585 and non-zero for true.
14588 left shift, and right shift. Defined on integral types.
14591 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14594 Addition and subtraction. Defined on integral types, floating-point types and
14597 @item *@r{, }/@r{, }%
14598 Multiplication, division, and modulus. Multiplication and division are
14599 defined on integral and floating-point types. Modulus is defined on
14603 Increment and decrement. When appearing before a variable, the
14604 operation is performed before the variable is used in an expression;
14605 when appearing after it, the variable's value is used before the
14606 operation takes place.
14609 Pointer dereferencing. Defined on pointer types. Same precedence as
14613 Address operator. Defined on variables. Same precedence as @code{++}.
14615 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14616 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14617 to examine the address
14618 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14622 Negative. Defined on integral and floating-point types. Same
14623 precedence as @code{++}.
14626 Logical negation. Defined on integral types. Same precedence as
14630 Bitwise complement operator. Defined on integral types. Same precedence as
14635 Structure member, and pointer-to-structure member. For convenience,
14636 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14637 pointer based on the stored type information.
14638 Defined on @code{struct} and @code{union} data.
14641 Dereferences of pointers to members.
14644 Array indexing. @code{@var{a}[@var{i}]} is defined as
14645 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14648 Function parameter list. Same precedence as @code{->}.
14651 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14652 and @code{class} types.
14655 Doubled colons also represent the @value{GDBN} scope operator
14656 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14660 If an operator is redefined in the user code, @value{GDBN} usually
14661 attempts to invoke the redefined version instead of using the operator's
14662 predefined meaning.
14665 @subsubsection C and C@t{++} Constants
14667 @cindex C and C@t{++} constants
14669 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14674 Integer constants are a sequence of digits. Octal constants are
14675 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14676 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14677 @samp{l}, specifying that the constant should be treated as a
14681 Floating point constants are a sequence of digits, followed by a decimal
14682 point, followed by a sequence of digits, and optionally followed by an
14683 exponent. An exponent is of the form:
14684 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14685 sequence of digits. The @samp{+} is optional for positive exponents.
14686 A floating-point constant may also end with a letter @samp{f} or
14687 @samp{F}, specifying that the constant should be treated as being of
14688 the @code{float} (as opposed to the default @code{double}) type; or with
14689 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14693 Enumerated constants consist of enumerated identifiers, or their
14694 integral equivalents.
14697 Character constants are a single character surrounded by single quotes
14698 (@code{'}), or a number---the ordinal value of the corresponding character
14699 (usually its @sc{ascii} value). Within quotes, the single character may
14700 be represented by a letter or by @dfn{escape sequences}, which are of
14701 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14702 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14703 @samp{@var{x}} is a predefined special character---for example,
14704 @samp{\n} for newline.
14706 Wide character constants can be written by prefixing a character
14707 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14708 form of @samp{x}. The target wide character set is used when
14709 computing the value of this constant (@pxref{Character Sets}).
14712 String constants are a sequence of character constants surrounded by
14713 double quotes (@code{"}). Any valid character constant (as described
14714 above) may appear. Double quotes within the string must be preceded by
14715 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14718 Wide string constants can be written by prefixing a string constant
14719 with @samp{L}, as in C. The target wide character set is used when
14720 computing the value of this constant (@pxref{Character Sets}).
14723 Pointer constants are an integral value. You can also write pointers
14724 to constants using the C operator @samp{&}.
14727 Array constants are comma-separated lists surrounded by braces @samp{@{}
14728 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14729 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14730 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14733 @node C Plus Plus Expressions
14734 @subsubsection C@t{++} Expressions
14736 @cindex expressions in C@t{++}
14737 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14739 @cindex debugging C@t{++} programs
14740 @cindex C@t{++} compilers
14741 @cindex debug formats and C@t{++}
14742 @cindex @value{NGCC} and C@t{++}
14744 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14745 the proper compiler and the proper debug format. Currently,
14746 @value{GDBN} works best when debugging C@t{++} code that is compiled
14747 with the most recent version of @value{NGCC} possible. The DWARF
14748 debugging format is preferred; @value{NGCC} defaults to this on most
14749 popular platforms. Other compilers and/or debug formats are likely to
14750 work badly or not at all when using @value{GDBN} to debug C@t{++}
14751 code. @xref{Compilation}.
14756 @cindex member functions
14758 Member function calls are allowed; you can use expressions like
14761 count = aml->GetOriginal(x, y)
14764 @vindex this@r{, inside C@t{++} member functions}
14765 @cindex namespace in C@t{++}
14767 While a member function is active (in the selected stack frame), your
14768 expressions have the same namespace available as the member function;
14769 that is, @value{GDBN} allows implicit references to the class instance
14770 pointer @code{this} following the same rules as C@t{++}. @code{using}
14771 declarations in the current scope are also respected by @value{GDBN}.
14773 @cindex call overloaded functions
14774 @cindex overloaded functions, calling
14775 @cindex type conversions in C@t{++}
14777 You can call overloaded functions; @value{GDBN} resolves the function
14778 call to the right definition, with some restrictions. @value{GDBN} does not
14779 perform overload resolution involving user-defined type conversions,
14780 calls to constructors, or instantiations of templates that do not exist
14781 in the program. It also cannot handle ellipsis argument lists or
14784 It does perform integral conversions and promotions, floating-point
14785 promotions, arithmetic conversions, pointer conversions, conversions of
14786 class objects to base classes, and standard conversions such as those of
14787 functions or arrays to pointers; it requires an exact match on the
14788 number of function arguments.
14790 Overload resolution is always performed, unless you have specified
14791 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14792 ,@value{GDBN} Features for C@t{++}}.
14794 You must specify @code{set overload-resolution off} in order to use an
14795 explicit function signature to call an overloaded function, as in
14797 p 'foo(char,int)'('x', 13)
14800 The @value{GDBN} command-completion facility can simplify this;
14801 see @ref{Completion, ,Command Completion}.
14803 @cindex reference declarations
14805 @value{GDBN} understands variables declared as C@t{++} references; you can use
14806 them in expressions just as you do in C@t{++} source---they are automatically
14809 In the parameter list shown when @value{GDBN} displays a frame, the values of
14810 reference variables are not displayed (unlike other variables); this
14811 avoids clutter, since references are often used for large structures.
14812 The @emph{address} of a reference variable is always shown, unless
14813 you have specified @samp{set print address off}.
14816 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14817 expressions can use it just as expressions in your program do. Since
14818 one scope may be defined in another, you can use @code{::} repeatedly if
14819 necessary, for example in an expression like
14820 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14821 resolving name scope by reference to source files, in both C and C@t{++}
14822 debugging (@pxref{Variables, ,Program Variables}).
14825 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14830 @subsubsection C and C@t{++} Defaults
14832 @cindex C and C@t{++} defaults
14834 If you allow @value{GDBN} to set range checking automatically, it
14835 defaults to @code{off} whenever the working language changes to
14836 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14837 selects the working language.
14839 If you allow @value{GDBN} to set the language automatically, it
14840 recognizes source files whose names end with @file{.c}, @file{.C}, or
14841 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14842 these files, it sets the working language to C or C@t{++}.
14843 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14844 for further details.
14847 @subsubsection C and C@t{++} Type and Range Checks
14849 @cindex C and C@t{++} checks
14851 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14852 checking is used. However, if you turn type checking off, @value{GDBN}
14853 will allow certain non-standard conversions, such as promoting integer
14854 constants to pointers.
14856 Range checking, if turned on, is done on mathematical operations. Array
14857 indices are not checked, since they are often used to index a pointer
14858 that is not itself an array.
14861 @subsubsection @value{GDBN} and C
14863 The @code{set print union} and @code{show print union} commands apply to
14864 the @code{union} type. When set to @samp{on}, any @code{union} that is
14865 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14866 appears as @samp{@{...@}}.
14868 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14869 with pointers and a memory allocation function. @xref{Expressions,
14872 @node Debugging C Plus Plus
14873 @subsubsection @value{GDBN} Features for C@t{++}
14875 @cindex commands for C@t{++}
14877 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14878 designed specifically for use with C@t{++}. Here is a summary:
14881 @cindex break in overloaded functions
14882 @item @r{breakpoint menus}
14883 When you want a breakpoint in a function whose name is overloaded,
14884 @value{GDBN} has the capability to display a menu of possible breakpoint
14885 locations to help you specify which function definition you want.
14886 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14888 @cindex overloading in C@t{++}
14889 @item rbreak @var{regex}
14890 Setting breakpoints using regular expressions is helpful for setting
14891 breakpoints on overloaded functions that are not members of any special
14893 @xref{Set Breaks, ,Setting Breakpoints}.
14895 @cindex C@t{++} exception handling
14897 @itemx catch rethrow
14899 Debug C@t{++} exception handling using these commands. @xref{Set
14900 Catchpoints, , Setting Catchpoints}.
14902 @cindex inheritance
14903 @item ptype @var{typename}
14904 Print inheritance relationships as well as other information for type
14906 @xref{Symbols, ,Examining the Symbol Table}.
14908 @item info vtbl @var{expression}.
14909 The @code{info vtbl} command can be used to display the virtual
14910 method tables of the object computed by @var{expression}. This shows
14911 one entry per virtual table; there may be multiple virtual tables when
14912 multiple inheritance is in use.
14914 @cindex C@t{++} demangling
14915 @item demangle @var{name}
14916 Demangle @var{name}.
14917 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14919 @cindex C@t{++} symbol display
14920 @item set print demangle
14921 @itemx show print demangle
14922 @itemx set print asm-demangle
14923 @itemx show print asm-demangle
14924 Control whether C@t{++} symbols display in their source form, both when
14925 displaying code as C@t{++} source and when displaying disassemblies.
14926 @xref{Print Settings, ,Print Settings}.
14928 @item set print object
14929 @itemx show print object
14930 Choose whether to print derived (actual) or declared types of objects.
14931 @xref{Print Settings, ,Print Settings}.
14933 @item set print vtbl
14934 @itemx show print vtbl
14935 Control the format for printing virtual function tables.
14936 @xref{Print Settings, ,Print Settings}.
14937 (The @code{vtbl} commands do not work on programs compiled with the HP
14938 ANSI C@t{++} compiler (@code{aCC}).)
14940 @kindex set overload-resolution
14941 @cindex overloaded functions, overload resolution
14942 @item set overload-resolution on
14943 Enable overload resolution for C@t{++} expression evaluation. The default
14944 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14945 and searches for a function whose signature matches the argument types,
14946 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14947 Expressions, ,C@t{++} Expressions}, for details).
14948 If it cannot find a match, it emits a message.
14950 @item set overload-resolution off
14951 Disable overload resolution for C@t{++} expression evaluation. For
14952 overloaded functions that are not class member functions, @value{GDBN}
14953 chooses the first function of the specified name that it finds in the
14954 symbol table, whether or not its arguments are of the correct type. For
14955 overloaded functions that are class member functions, @value{GDBN}
14956 searches for a function whose signature @emph{exactly} matches the
14959 @kindex show overload-resolution
14960 @item show overload-resolution
14961 Show the current setting of overload resolution.
14963 @item @r{Overloaded symbol names}
14964 You can specify a particular definition of an overloaded symbol, using
14965 the same notation that is used to declare such symbols in C@t{++}: type
14966 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14967 also use the @value{GDBN} command-line word completion facilities to list the
14968 available choices, or to finish the type list for you.
14969 @xref{Completion,, Command Completion}, for details on how to do this.
14972 @node Decimal Floating Point
14973 @subsubsection Decimal Floating Point format
14974 @cindex decimal floating point format
14976 @value{GDBN} can examine, set and perform computations with numbers in
14977 decimal floating point format, which in the C language correspond to the
14978 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14979 specified by the extension to support decimal floating-point arithmetic.
14981 There are two encodings in use, depending on the architecture: BID (Binary
14982 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14983 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14986 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14987 to manipulate decimal floating point numbers, it is not possible to convert
14988 (using a cast, for example) integers wider than 32-bit to decimal float.
14990 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14991 point computations, error checking in decimal float operations ignores
14992 underflow, overflow and divide by zero exceptions.
14994 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14995 to inspect @code{_Decimal128} values stored in floating point registers.
14996 See @ref{PowerPC,,PowerPC} for more details.
15002 @value{GDBN} can be used to debug programs written in D and compiled with
15003 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15004 specific feature --- dynamic arrays.
15009 @cindex Go (programming language)
15010 @value{GDBN} can be used to debug programs written in Go and compiled with
15011 @file{gccgo} or @file{6g} compilers.
15013 Here is a summary of the Go-specific features and restrictions:
15016 @cindex current Go package
15017 @item The current Go package
15018 The name of the current package does not need to be specified when
15019 specifying global variables and functions.
15021 For example, given the program:
15025 var myglob = "Shall we?"
15031 When stopped inside @code{main} either of these work:
15035 (gdb) p main.myglob
15038 @cindex builtin Go types
15039 @item Builtin Go types
15040 The @code{string} type is recognized by @value{GDBN} and is printed
15043 @cindex builtin Go functions
15044 @item Builtin Go functions
15045 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15046 function and handles it internally.
15048 @cindex restrictions on Go expressions
15049 @item Restrictions on Go expressions
15050 All Go operators are supported except @code{&^}.
15051 The Go @code{_} ``blank identifier'' is not supported.
15052 Automatic dereferencing of pointers is not supported.
15056 @subsection Objective-C
15058 @cindex Objective-C
15059 This section provides information about some commands and command
15060 options that are useful for debugging Objective-C code. See also
15061 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15062 few more commands specific to Objective-C support.
15065 * Method Names in Commands::
15066 * The Print Command with Objective-C::
15069 @node Method Names in Commands
15070 @subsubsection Method Names in Commands
15072 The following commands have been extended to accept Objective-C method
15073 names as line specifications:
15075 @kindex clear@r{, and Objective-C}
15076 @kindex break@r{, and Objective-C}
15077 @kindex info line@r{, and Objective-C}
15078 @kindex jump@r{, and Objective-C}
15079 @kindex list@r{, and Objective-C}
15083 @item @code{info line}
15088 A fully qualified Objective-C method name is specified as
15091 -[@var{Class} @var{methodName}]
15094 where the minus sign is used to indicate an instance method and a
15095 plus sign (not shown) is used to indicate a class method. The class
15096 name @var{Class} and method name @var{methodName} are enclosed in
15097 brackets, similar to the way messages are specified in Objective-C
15098 source code. For example, to set a breakpoint at the @code{create}
15099 instance method of class @code{Fruit} in the program currently being
15103 break -[Fruit create]
15106 To list ten program lines around the @code{initialize} class method,
15110 list +[NSText initialize]
15113 In the current version of @value{GDBN}, the plus or minus sign is
15114 required. In future versions of @value{GDBN}, the plus or minus
15115 sign will be optional, but you can use it to narrow the search. It
15116 is also possible to specify just a method name:
15122 You must specify the complete method name, including any colons. If
15123 your program's source files contain more than one @code{create} method,
15124 you'll be presented with a numbered list of classes that implement that
15125 method. Indicate your choice by number, or type @samp{0} to exit if
15128 As another example, to clear a breakpoint established at the
15129 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15132 clear -[NSWindow makeKeyAndOrderFront:]
15135 @node The Print Command with Objective-C
15136 @subsubsection The Print Command With Objective-C
15137 @cindex Objective-C, print objects
15138 @kindex print-object
15139 @kindex po @r{(@code{print-object})}
15141 The print command has also been extended to accept methods. For example:
15144 print -[@var{object} hash]
15147 @cindex print an Objective-C object description
15148 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15150 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15151 and print the result. Also, an additional command has been added,
15152 @code{print-object} or @code{po} for short, which is meant to print
15153 the description of an object. However, this command may only work
15154 with certain Objective-C libraries that have a particular hook
15155 function, @code{_NSPrintForDebugger}, defined.
15158 @subsection OpenCL C
15161 This section provides information about @value{GDBN}s OpenCL C support.
15164 * OpenCL C Datatypes::
15165 * OpenCL C Expressions::
15166 * OpenCL C Operators::
15169 @node OpenCL C Datatypes
15170 @subsubsection OpenCL C Datatypes
15172 @cindex OpenCL C Datatypes
15173 @value{GDBN} supports the builtin scalar and vector datatypes specified
15174 by OpenCL 1.1. In addition the half- and double-precision floating point
15175 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15176 extensions are also known to @value{GDBN}.
15178 @node OpenCL C Expressions
15179 @subsubsection OpenCL C Expressions
15181 @cindex OpenCL C Expressions
15182 @value{GDBN} supports accesses to vector components including the access as
15183 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15184 supported by @value{GDBN} can be used as well.
15186 @node OpenCL C Operators
15187 @subsubsection OpenCL C Operators
15189 @cindex OpenCL C Operators
15190 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15194 @subsection Fortran
15195 @cindex Fortran-specific support in @value{GDBN}
15197 @value{GDBN} can be used to debug programs written in Fortran, but it
15198 currently supports only the features of Fortran 77 language.
15200 @cindex trailing underscore, in Fortran symbols
15201 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15202 among them) append an underscore to the names of variables and
15203 functions. When you debug programs compiled by those compilers, you
15204 will need to refer to variables and functions with a trailing
15208 * Fortran Operators:: Fortran operators and expressions
15209 * Fortran Defaults:: Default settings for Fortran
15210 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15213 @node Fortran Operators
15214 @subsubsection Fortran Operators and Expressions
15216 @cindex Fortran operators and expressions
15218 Operators must be defined on values of specific types. For instance,
15219 @code{+} is defined on numbers, but not on characters or other non-
15220 arithmetic types. Operators are often defined on groups of types.
15224 The exponentiation operator. It raises the first operand to the power
15228 The range operator. Normally used in the form of array(low:high) to
15229 represent a section of array.
15232 The access component operator. Normally used to access elements in derived
15233 types. Also suitable for unions. As unions aren't part of regular Fortran,
15234 this can only happen when accessing a register that uses a gdbarch-defined
15238 @node Fortran Defaults
15239 @subsubsection Fortran Defaults
15241 @cindex Fortran Defaults
15243 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15244 default uses case-insensitive matches for Fortran symbols. You can
15245 change that with the @samp{set case-insensitive} command, see
15246 @ref{Symbols}, for the details.
15248 @node Special Fortran Commands
15249 @subsubsection Special Fortran Commands
15251 @cindex Special Fortran commands
15253 @value{GDBN} has some commands to support Fortran-specific features,
15254 such as displaying common blocks.
15257 @cindex @code{COMMON} blocks, Fortran
15258 @kindex info common
15259 @item info common @r{[}@var{common-name}@r{]}
15260 This command prints the values contained in the Fortran @code{COMMON}
15261 block whose name is @var{common-name}. With no argument, the names of
15262 all @code{COMMON} blocks visible at the current program location are
15269 @cindex Pascal support in @value{GDBN}, limitations
15270 Debugging Pascal programs which use sets, subranges, file variables, or
15271 nested functions does not currently work. @value{GDBN} does not support
15272 entering expressions, printing values, or similar features using Pascal
15275 The Pascal-specific command @code{set print pascal_static-members}
15276 controls whether static members of Pascal objects are displayed.
15277 @xref{Print Settings, pascal_static-members}.
15282 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15283 Programming Language}. Type- and value-printing, and expression
15284 parsing, are reasonably complete. However, there are a few
15285 peculiarities and holes to be aware of.
15289 Linespecs (@pxref{Specify Location}) are never relative to the current
15290 crate. Instead, they act as if there were a global namespace of
15291 crates, somewhat similar to the way @code{extern crate} behaves.
15293 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15294 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15295 to set a breakpoint in a function named @samp{f} in a crate named
15298 As a consequence of this approach, linespecs also cannot refer to
15299 items using @samp{self::} or @samp{super::}.
15302 Because @value{GDBN} implements Rust name-lookup semantics in
15303 expressions, it will sometimes prepend the current crate to a name.
15304 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15305 @samp{K}, then @code{print ::x::y} will try to find the symbol
15308 However, since it is useful to be able to refer to other crates when
15309 debugging, @value{GDBN} provides the @code{extern} extension to
15310 circumvent this. To use the extension, just put @code{extern} before
15311 a path expression to refer to the otherwise unavailable ``global''
15314 In the above example, if you wanted to refer to the symbol @samp{y} in
15315 the crate @samp{x}, you would use @code{print extern x::y}.
15318 The Rust expression evaluator does not support ``statement-like''
15319 expressions such as @code{if} or @code{match}, or lambda expressions.
15322 Tuple expressions are not implemented.
15325 The Rust expression evaluator does not currently implement the
15326 @code{Drop} trait. Objects that may be created by the evaluator will
15327 never be destroyed.
15330 @value{GDBN} does not implement type inference for generics. In order
15331 to call generic functions or otherwise refer to generic items, you
15332 will have to specify the type parameters manually.
15335 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15336 cases this does not cause any problems. However, in an expression
15337 context, completing a generic function name will give syntactically
15338 invalid results. This happens because Rust requires the @samp{::}
15339 operator between the function name and its generic arguments. For
15340 example, @value{GDBN} might provide a completion like
15341 @code{crate::f<u32>}, where the parser would require
15342 @code{crate::f::<u32>}.
15345 As of this writing, the Rust compiler (version 1.8) has a few holes in
15346 the debugging information it generates. These holes prevent certain
15347 features from being implemented by @value{GDBN}:
15351 Method calls cannot be made via traits.
15354 Trait objects cannot be created or inspected.
15357 Operator overloading is not implemented.
15360 When debugging in a monomorphized function, you cannot use the generic
15364 The type @code{Self} is not available.
15367 @code{use} statements are not available, so some names may not be
15368 available in the crate.
15373 @subsection Modula-2
15375 @cindex Modula-2, @value{GDBN} support
15377 The extensions made to @value{GDBN} to support Modula-2 only support
15378 output from the @sc{gnu} Modula-2 compiler (which is currently being
15379 developed). Other Modula-2 compilers are not currently supported, and
15380 attempting to debug executables produced by them is most likely
15381 to give an error as @value{GDBN} reads in the executable's symbol
15384 @cindex expressions in Modula-2
15386 * M2 Operators:: Built-in operators
15387 * Built-In Func/Proc:: Built-in functions and procedures
15388 * M2 Constants:: Modula-2 constants
15389 * M2 Types:: Modula-2 types
15390 * M2 Defaults:: Default settings for Modula-2
15391 * Deviations:: Deviations from standard Modula-2
15392 * M2 Checks:: Modula-2 type and range checks
15393 * M2 Scope:: The scope operators @code{::} and @code{.}
15394 * GDB/M2:: @value{GDBN} and Modula-2
15398 @subsubsection Operators
15399 @cindex Modula-2 operators
15401 Operators must be defined on values of specific types. For instance,
15402 @code{+} is defined on numbers, but not on structures. Operators are
15403 often defined on groups of types. For the purposes of Modula-2, the
15404 following definitions hold:
15409 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15413 @emph{Character types} consist of @code{CHAR} and its subranges.
15416 @emph{Floating-point types} consist of @code{REAL}.
15419 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15423 @emph{Scalar types} consist of all of the above.
15426 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15429 @emph{Boolean types} consist of @code{BOOLEAN}.
15433 The following operators are supported, and appear in order of
15434 increasing precedence:
15438 Function argument or array index separator.
15441 Assignment. The value of @var{var} @code{:=} @var{value} is
15445 Less than, greater than on integral, floating-point, or enumerated
15449 Less than or equal to, greater than or equal to
15450 on integral, floating-point and enumerated types, or set inclusion on
15451 set types. Same precedence as @code{<}.
15453 @item =@r{, }<>@r{, }#
15454 Equality and two ways of expressing inequality, valid on scalar types.
15455 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15456 available for inequality, since @code{#} conflicts with the script
15460 Set membership. Defined on set types and the types of their members.
15461 Same precedence as @code{<}.
15464 Boolean disjunction. Defined on boolean types.
15467 Boolean conjunction. Defined on boolean types.
15470 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15473 Addition and subtraction on integral and floating-point types, or union
15474 and difference on set types.
15477 Multiplication on integral and floating-point types, or set intersection
15481 Division on floating-point types, or symmetric set difference on set
15482 types. Same precedence as @code{*}.
15485 Integer division and remainder. Defined on integral types. Same
15486 precedence as @code{*}.
15489 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15492 Pointer dereferencing. Defined on pointer types.
15495 Boolean negation. Defined on boolean types. Same precedence as
15499 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15500 precedence as @code{^}.
15503 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15506 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15510 @value{GDBN} and Modula-2 scope operators.
15514 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15515 treats the use of the operator @code{IN}, or the use of operators
15516 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15517 @code{<=}, and @code{>=} on sets as an error.
15521 @node Built-In Func/Proc
15522 @subsubsection Built-in Functions and Procedures
15523 @cindex Modula-2 built-ins
15525 Modula-2 also makes available several built-in procedures and functions.
15526 In describing these, the following metavariables are used:
15531 represents an @code{ARRAY} variable.
15534 represents a @code{CHAR} constant or variable.
15537 represents a variable or constant of integral type.
15540 represents an identifier that belongs to a set. Generally used in the
15541 same function with the metavariable @var{s}. The type of @var{s} should
15542 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15545 represents a variable or constant of integral or floating-point type.
15548 represents a variable or constant of floating-point type.
15554 represents a variable.
15557 represents a variable or constant of one of many types. See the
15558 explanation of the function for details.
15561 All Modula-2 built-in procedures also return a result, described below.
15565 Returns the absolute value of @var{n}.
15568 If @var{c} is a lower case letter, it returns its upper case
15569 equivalent, otherwise it returns its argument.
15572 Returns the character whose ordinal value is @var{i}.
15575 Decrements the value in the variable @var{v} by one. Returns the new value.
15577 @item DEC(@var{v},@var{i})
15578 Decrements the value in the variable @var{v} by @var{i}. Returns the
15581 @item EXCL(@var{m},@var{s})
15582 Removes the element @var{m} from the set @var{s}. Returns the new
15585 @item FLOAT(@var{i})
15586 Returns the floating point equivalent of the integer @var{i}.
15588 @item HIGH(@var{a})
15589 Returns the index of the last member of @var{a}.
15592 Increments the value in the variable @var{v} by one. Returns the new value.
15594 @item INC(@var{v},@var{i})
15595 Increments the value in the variable @var{v} by @var{i}. Returns the
15598 @item INCL(@var{m},@var{s})
15599 Adds the element @var{m} to the set @var{s} if it is not already
15600 there. Returns the new set.
15603 Returns the maximum value of the type @var{t}.
15606 Returns the minimum value of the type @var{t}.
15609 Returns boolean TRUE if @var{i} is an odd number.
15612 Returns the ordinal value of its argument. For example, the ordinal
15613 value of a character is its @sc{ascii} value (on machines supporting
15614 the @sc{ascii} character set). The argument @var{x} must be of an
15615 ordered type, which include integral, character and enumerated types.
15617 @item SIZE(@var{x})
15618 Returns the size of its argument. The argument @var{x} can be a
15619 variable or a type.
15621 @item TRUNC(@var{r})
15622 Returns the integral part of @var{r}.
15624 @item TSIZE(@var{x})
15625 Returns the size of its argument. The argument @var{x} can be a
15626 variable or a type.
15628 @item VAL(@var{t},@var{i})
15629 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15633 @emph{Warning:} Sets and their operations are not yet supported, so
15634 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15638 @cindex Modula-2 constants
15640 @subsubsection Constants
15642 @value{GDBN} allows you to express the constants of Modula-2 in the following
15648 Integer constants are simply a sequence of digits. When used in an
15649 expression, a constant is interpreted to be type-compatible with the
15650 rest of the expression. Hexadecimal integers are specified by a
15651 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15654 Floating point constants appear as a sequence of digits, followed by a
15655 decimal point and another sequence of digits. An optional exponent can
15656 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15657 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15658 digits of the floating point constant must be valid decimal (base 10)
15662 Character constants consist of a single character enclosed by a pair of
15663 like quotes, either single (@code{'}) or double (@code{"}). They may
15664 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15665 followed by a @samp{C}.
15668 String constants consist of a sequence of characters enclosed by a
15669 pair of like quotes, either single (@code{'}) or double (@code{"}).
15670 Escape sequences in the style of C are also allowed. @xref{C
15671 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15675 Enumerated constants consist of an enumerated identifier.
15678 Boolean constants consist of the identifiers @code{TRUE} and
15682 Pointer constants consist of integral values only.
15685 Set constants are not yet supported.
15689 @subsubsection Modula-2 Types
15690 @cindex Modula-2 types
15692 Currently @value{GDBN} can print the following data types in Modula-2
15693 syntax: array types, record types, set types, pointer types, procedure
15694 types, enumerated types, subrange types and base types. You can also
15695 print the contents of variables declared using these type.
15696 This section gives a number of simple source code examples together with
15697 sample @value{GDBN} sessions.
15699 The first example contains the following section of code:
15708 and you can request @value{GDBN} to interrogate the type and value of
15709 @code{r} and @code{s}.
15712 (@value{GDBP}) print s
15714 (@value{GDBP}) ptype s
15716 (@value{GDBP}) print r
15718 (@value{GDBP}) ptype r
15723 Likewise if your source code declares @code{s} as:
15727 s: SET ['A'..'Z'] ;
15731 then you may query the type of @code{s} by:
15734 (@value{GDBP}) ptype s
15735 type = SET ['A'..'Z']
15739 Note that at present you cannot interactively manipulate set
15740 expressions using the debugger.
15742 The following example shows how you might declare an array in Modula-2
15743 and how you can interact with @value{GDBN} to print its type and contents:
15747 s: ARRAY [-10..10] OF CHAR ;
15751 (@value{GDBP}) ptype s
15752 ARRAY [-10..10] OF CHAR
15755 Note that the array handling is not yet complete and although the type
15756 is printed correctly, expression handling still assumes that all
15757 arrays have a lower bound of zero and not @code{-10} as in the example
15760 Here are some more type related Modula-2 examples:
15764 colour = (blue, red, yellow, green) ;
15765 t = [blue..yellow] ;
15773 The @value{GDBN} interaction shows how you can query the data type
15774 and value of a variable.
15777 (@value{GDBP}) print s
15779 (@value{GDBP}) ptype t
15780 type = [blue..yellow]
15784 In this example a Modula-2 array is declared and its contents
15785 displayed. Observe that the contents are written in the same way as
15786 their @code{C} counterparts.
15790 s: ARRAY [1..5] OF CARDINAL ;
15796 (@value{GDBP}) print s
15797 $1 = @{1, 0, 0, 0, 0@}
15798 (@value{GDBP}) ptype s
15799 type = ARRAY [1..5] OF CARDINAL
15802 The Modula-2 language interface to @value{GDBN} also understands
15803 pointer types as shown in this example:
15807 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15814 and you can request that @value{GDBN} describes the type of @code{s}.
15817 (@value{GDBP}) ptype s
15818 type = POINTER TO ARRAY [1..5] OF CARDINAL
15821 @value{GDBN} handles compound types as we can see in this example.
15822 Here we combine array types, record types, pointer types and subrange
15833 myarray = ARRAY myrange OF CARDINAL ;
15834 myrange = [-2..2] ;
15836 s: POINTER TO ARRAY myrange OF foo ;
15840 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15844 (@value{GDBP}) ptype s
15845 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15848 f3 : ARRAY [-2..2] OF CARDINAL;
15853 @subsubsection Modula-2 Defaults
15854 @cindex Modula-2 defaults
15856 If type and range checking are set automatically by @value{GDBN}, they
15857 both default to @code{on} whenever the working language changes to
15858 Modula-2. This happens regardless of whether you or @value{GDBN}
15859 selected the working language.
15861 If you allow @value{GDBN} to set the language automatically, then entering
15862 code compiled from a file whose name ends with @file{.mod} sets the
15863 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15864 Infer the Source Language}, for further details.
15867 @subsubsection Deviations from Standard Modula-2
15868 @cindex Modula-2, deviations from
15870 A few changes have been made to make Modula-2 programs easier to debug.
15871 This is done primarily via loosening its type strictness:
15875 Unlike in standard Modula-2, pointer constants can be formed by
15876 integers. This allows you to modify pointer variables during
15877 debugging. (In standard Modula-2, the actual address contained in a
15878 pointer variable is hidden from you; it can only be modified
15879 through direct assignment to another pointer variable or expression that
15880 returned a pointer.)
15883 C escape sequences can be used in strings and characters to represent
15884 non-printable characters. @value{GDBN} prints out strings with these
15885 escape sequences embedded. Single non-printable characters are
15886 printed using the @samp{CHR(@var{nnn})} format.
15889 The assignment operator (@code{:=}) returns the value of its right-hand
15893 All built-in procedures both modify @emph{and} return their argument.
15897 @subsubsection Modula-2 Type and Range Checks
15898 @cindex Modula-2 checks
15901 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15904 @c FIXME remove warning when type/range checks added
15906 @value{GDBN} considers two Modula-2 variables type equivalent if:
15910 They are of types that have been declared equivalent via a @code{TYPE
15911 @var{t1} = @var{t2}} statement
15914 They have been declared on the same line. (Note: This is true of the
15915 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15918 As long as type checking is enabled, any attempt to combine variables
15919 whose types are not equivalent is an error.
15921 Range checking is done on all mathematical operations, assignment, array
15922 index bounds, and all built-in functions and procedures.
15925 @subsubsection The Scope Operators @code{::} and @code{.}
15927 @cindex @code{.}, Modula-2 scope operator
15928 @cindex colon, doubled as scope operator
15930 @vindex colon-colon@r{, in Modula-2}
15931 @c Info cannot handle :: but TeX can.
15934 @vindex ::@r{, in Modula-2}
15937 There are a few subtle differences between the Modula-2 scope operator
15938 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15943 @var{module} . @var{id}
15944 @var{scope} :: @var{id}
15948 where @var{scope} is the name of a module or a procedure,
15949 @var{module} the name of a module, and @var{id} is any declared
15950 identifier within your program, except another module.
15952 Using the @code{::} operator makes @value{GDBN} search the scope
15953 specified by @var{scope} for the identifier @var{id}. If it is not
15954 found in the specified scope, then @value{GDBN} searches all scopes
15955 enclosing the one specified by @var{scope}.
15957 Using the @code{.} operator makes @value{GDBN} search the current scope for
15958 the identifier specified by @var{id} that was imported from the
15959 definition module specified by @var{module}. With this operator, it is
15960 an error if the identifier @var{id} was not imported from definition
15961 module @var{module}, or if @var{id} is not an identifier in
15965 @subsubsection @value{GDBN} and Modula-2
15967 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15968 Five subcommands of @code{set print} and @code{show print} apply
15969 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15970 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15971 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15972 analogue in Modula-2.
15974 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15975 with any language, is not useful with Modula-2. Its
15976 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15977 created in Modula-2 as they can in C or C@t{++}. However, because an
15978 address can be specified by an integral constant, the construct
15979 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15981 @cindex @code{#} in Modula-2
15982 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15983 interpreted as the beginning of a comment. Use @code{<>} instead.
15989 The extensions made to @value{GDBN} for Ada only support
15990 output from the @sc{gnu} Ada (GNAT) compiler.
15991 Other Ada compilers are not currently supported, and
15992 attempting to debug executables produced by them is most likely
15996 @cindex expressions in Ada
15998 * Ada Mode Intro:: General remarks on the Ada syntax
15999 and semantics supported by Ada mode
16001 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16002 * Additions to Ada:: Extensions of the Ada expression syntax.
16003 * Overloading support for Ada:: Support for expressions involving overloaded
16005 * Stopping Before Main Program:: Debugging the program during elaboration.
16006 * Ada Exceptions:: Ada Exceptions
16007 * Ada Tasks:: Listing and setting breakpoints in tasks.
16008 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16009 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16011 * Ada Glitches:: Known peculiarities of Ada mode.
16014 @node Ada Mode Intro
16015 @subsubsection Introduction
16016 @cindex Ada mode, general
16018 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16019 syntax, with some extensions.
16020 The philosophy behind the design of this subset is
16024 That @value{GDBN} should provide basic literals and access to operations for
16025 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16026 leaving more sophisticated computations to subprograms written into the
16027 program (which therefore may be called from @value{GDBN}).
16030 That type safety and strict adherence to Ada language restrictions
16031 are not particularly important to the @value{GDBN} user.
16034 That brevity is important to the @value{GDBN} user.
16037 Thus, for brevity, the debugger acts as if all names declared in
16038 user-written packages are directly visible, even if they are not visible
16039 according to Ada rules, thus making it unnecessary to fully qualify most
16040 names with their packages, regardless of context. Where this causes
16041 ambiguity, @value{GDBN} asks the user's intent.
16043 The debugger will start in Ada mode if it detects an Ada main program.
16044 As for other languages, it will enter Ada mode when stopped in a program that
16045 was translated from an Ada source file.
16047 While in Ada mode, you may use `@t{--}' for comments. This is useful
16048 mostly for documenting command files. The standard @value{GDBN} comment
16049 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16050 middle (to allow based literals).
16052 @node Omissions from Ada
16053 @subsubsection Omissions from Ada
16054 @cindex Ada, omissions from
16056 Here are the notable omissions from the subset:
16060 Only a subset of the attributes are supported:
16064 @t{'First}, @t{'Last}, and @t{'Length}
16065 on array objects (not on types and subtypes).
16068 @t{'Min} and @t{'Max}.
16071 @t{'Pos} and @t{'Val}.
16077 @t{'Range} on array objects (not subtypes), but only as the right
16078 operand of the membership (@code{in}) operator.
16081 @t{'Access}, @t{'Unchecked_Access}, and
16082 @t{'Unrestricted_Access} (a GNAT extension).
16090 @code{Characters.Latin_1} are not available and
16091 concatenation is not implemented. Thus, escape characters in strings are
16092 not currently available.
16095 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16096 equality of representations. They will generally work correctly
16097 for strings and arrays whose elements have integer or enumeration types.
16098 They may not work correctly for arrays whose element
16099 types have user-defined equality, for arrays of real values
16100 (in particular, IEEE-conformant floating point, because of negative
16101 zeroes and NaNs), and for arrays whose elements contain unused bits with
16102 indeterminate values.
16105 The other component-by-component array operations (@code{and}, @code{or},
16106 @code{xor}, @code{not}, and relational tests other than equality)
16107 are not implemented.
16110 @cindex array aggregates (Ada)
16111 @cindex record aggregates (Ada)
16112 @cindex aggregates (Ada)
16113 There is limited support for array and record aggregates. They are
16114 permitted only on the right sides of assignments, as in these examples:
16117 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16118 (@value{GDBP}) set An_Array := (1, others => 0)
16119 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16120 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16121 (@value{GDBP}) set A_Record := (1, "Peter", True);
16122 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16126 discriminant's value by assigning an aggregate has an
16127 undefined effect if that discriminant is used within the record.
16128 However, you can first modify discriminants by directly assigning to
16129 them (which normally would not be allowed in Ada), and then performing an
16130 aggregate assignment. For example, given a variable @code{A_Rec}
16131 declared to have a type such as:
16134 type Rec (Len : Small_Integer := 0) is record
16136 Vals : IntArray (1 .. Len);
16140 you can assign a value with a different size of @code{Vals} with two
16144 (@value{GDBP}) set A_Rec.Len := 4
16145 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16148 As this example also illustrates, @value{GDBN} is very loose about the usual
16149 rules concerning aggregates. You may leave out some of the
16150 components of an array or record aggregate (such as the @code{Len}
16151 component in the assignment to @code{A_Rec} above); they will retain their
16152 original values upon assignment. You may freely use dynamic values as
16153 indices in component associations. You may even use overlapping or
16154 redundant component associations, although which component values are
16155 assigned in such cases is not defined.
16158 Calls to dispatching subprograms are not implemented.
16161 The overloading algorithm is much more limited (i.e., less selective)
16162 than that of real Ada. It makes only limited use of the context in
16163 which a subexpression appears to resolve its meaning, and it is much
16164 looser in its rules for allowing type matches. As a result, some
16165 function calls will be ambiguous, and the user will be asked to choose
16166 the proper resolution.
16169 The @code{new} operator is not implemented.
16172 Entry calls are not implemented.
16175 Aside from printing, arithmetic operations on the native VAX floating-point
16176 formats are not supported.
16179 It is not possible to slice a packed array.
16182 The names @code{True} and @code{False}, when not part of a qualified name,
16183 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16185 Should your program
16186 redefine these names in a package or procedure (at best a dubious practice),
16187 you will have to use fully qualified names to access their new definitions.
16190 @node Additions to Ada
16191 @subsubsection Additions to Ada
16192 @cindex Ada, deviations from
16194 As it does for other languages, @value{GDBN} makes certain generic
16195 extensions to Ada (@pxref{Expressions}):
16199 If the expression @var{E} is a variable residing in memory (typically
16200 a local variable or array element) and @var{N} is a positive integer,
16201 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16202 @var{N}-1 adjacent variables following it in memory as an array. In
16203 Ada, this operator is generally not necessary, since its prime use is
16204 in displaying parts of an array, and slicing will usually do this in
16205 Ada. However, there are occasional uses when debugging programs in
16206 which certain debugging information has been optimized away.
16209 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16210 appears in function or file @var{B}.'' When @var{B} is a file name,
16211 you must typically surround it in single quotes.
16214 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16215 @var{type} that appears at address @var{addr}.''
16218 A name starting with @samp{$} is a convenience variable
16219 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16222 In addition, @value{GDBN} provides a few other shortcuts and outright
16223 additions specific to Ada:
16227 The assignment statement is allowed as an expression, returning
16228 its right-hand operand as its value. Thus, you may enter
16231 (@value{GDBP}) set x := y + 3
16232 (@value{GDBP}) print A(tmp := y + 1)
16236 The semicolon is allowed as an ``operator,'' returning as its value
16237 the value of its right-hand operand.
16238 This allows, for example,
16239 complex conditional breaks:
16242 (@value{GDBP}) break f
16243 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16247 Rather than use catenation and symbolic character names to introduce special
16248 characters into strings, one may instead use a special bracket notation,
16249 which is also used to print strings. A sequence of characters of the form
16250 @samp{["@var{XX}"]} within a string or character literal denotes the
16251 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16252 sequence of characters @samp{["""]} also denotes a single quotation mark
16253 in strings. For example,
16255 "One line.["0a"]Next line.["0a"]"
16258 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16262 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16263 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16267 (@value{GDBP}) print 'max(x, y)
16271 When printing arrays, @value{GDBN} uses positional notation when the
16272 array has a lower bound of 1, and uses a modified named notation otherwise.
16273 For example, a one-dimensional array of three integers with a lower bound
16274 of 3 might print as
16281 That is, in contrast to valid Ada, only the first component has a @code{=>}
16285 You may abbreviate attributes in expressions with any unique,
16286 multi-character subsequence of
16287 their names (an exact match gets preference).
16288 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16289 in place of @t{a'length}.
16292 @cindex quoting Ada internal identifiers
16293 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16294 to lower case. The GNAT compiler uses upper-case characters for
16295 some of its internal identifiers, which are normally of no interest to users.
16296 For the rare occasions when you actually have to look at them,
16297 enclose them in angle brackets to avoid the lower-case mapping.
16300 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16304 Printing an object of class-wide type or dereferencing an
16305 access-to-class-wide value will display all the components of the object's
16306 specific type (as indicated by its run-time tag). Likewise, component
16307 selection on such a value will operate on the specific type of the
16312 @node Overloading support for Ada
16313 @subsubsection Overloading support for Ada
16314 @cindex overloading, Ada
16316 The debugger supports limited overloading. Given a subprogram call in which
16317 the function symbol has multiple definitions, it will use the number of
16318 actual parameters and some information about their types to attempt to narrow
16319 the set of definitions. It also makes very limited use of context, preferring
16320 procedures to functions in the context of the @code{call} command, and
16321 functions to procedures elsewhere.
16323 If, after narrowing, the set of matching definitions still contains more than
16324 one definition, @value{GDBN} will display a menu to query which one it should
16328 (@value{GDBP}) print f(1)
16329 Multiple matches for f
16331 [1] foo.f (integer) return boolean at foo.adb:23
16332 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16336 In this case, just select one menu entry either to cancel expression evaluation
16337 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16338 instance (type the corresponding number and press @key{RET}).
16340 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16345 @kindex set ada print-signatures
16346 @item set ada print-signatures
16347 Control whether parameter types and return types are displayed in overloads
16348 selection menus. It is @code{on} by default.
16349 @xref{Overloading support for Ada}.
16351 @kindex show ada print-signatures
16352 @item show ada print-signatures
16353 Show the current setting for displaying parameter types and return types in
16354 overloads selection menu.
16355 @xref{Overloading support for Ada}.
16359 @node Stopping Before Main Program
16360 @subsubsection Stopping at the Very Beginning
16362 @cindex breakpointing Ada elaboration code
16363 It is sometimes necessary to debug the program during elaboration, and
16364 before reaching the main procedure.
16365 As defined in the Ada Reference
16366 Manual, the elaboration code is invoked from a procedure called
16367 @code{adainit}. To run your program up to the beginning of
16368 elaboration, simply use the following two commands:
16369 @code{tbreak adainit} and @code{run}.
16371 @node Ada Exceptions
16372 @subsubsection Ada Exceptions
16374 A command is provided to list all Ada exceptions:
16377 @kindex info exceptions
16378 @item info exceptions
16379 @itemx info exceptions @var{regexp}
16380 The @code{info exceptions} command allows you to list all Ada exceptions
16381 defined within the program being debugged, as well as their addresses.
16382 With a regular expression, @var{regexp}, as argument, only those exceptions
16383 whose names match @var{regexp} are listed.
16386 Below is a small example, showing how the command can be used, first
16387 without argument, and next with a regular expression passed as an
16391 (@value{GDBP}) info exceptions
16392 All defined Ada exceptions:
16393 constraint_error: 0x613da0
16394 program_error: 0x613d20
16395 storage_error: 0x613ce0
16396 tasking_error: 0x613ca0
16397 const.aint_global_e: 0x613b00
16398 (@value{GDBP}) info exceptions const.aint
16399 All Ada exceptions matching regular expression "const.aint":
16400 constraint_error: 0x613da0
16401 const.aint_global_e: 0x613b00
16404 It is also possible to ask @value{GDBN} to stop your program's execution
16405 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16408 @subsubsection Extensions for Ada Tasks
16409 @cindex Ada, tasking
16411 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16412 @value{GDBN} provides the following task-related commands:
16417 This command shows a list of current Ada tasks, as in the following example:
16424 (@value{GDBP}) info tasks
16425 ID TID P-ID Pri State Name
16426 1 8088000 0 15 Child Activation Wait main_task
16427 2 80a4000 1 15 Accept Statement b
16428 3 809a800 1 15 Child Activation Wait a
16429 * 4 80ae800 3 15 Runnable c
16434 In this listing, the asterisk before the last task indicates it to be the
16435 task currently being inspected.
16439 Represents @value{GDBN}'s internal task number.
16445 The parent's task ID (@value{GDBN}'s internal task number).
16448 The base priority of the task.
16451 Current state of the task.
16455 The task has been created but has not been activated. It cannot be
16459 The task is not blocked for any reason known to Ada. (It may be waiting
16460 for a mutex, though.) It is conceptually "executing" in normal mode.
16463 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16464 that were waiting on terminate alternatives have been awakened and have
16465 terminated themselves.
16467 @item Child Activation Wait
16468 The task is waiting for created tasks to complete activation.
16470 @item Accept Statement
16471 The task is waiting on an accept or selective wait statement.
16473 @item Waiting on entry call
16474 The task is waiting on an entry call.
16476 @item Async Select Wait
16477 The task is waiting to start the abortable part of an asynchronous
16481 The task is waiting on a select statement with only a delay
16484 @item Child Termination Wait
16485 The task is sleeping having completed a master within itself, and is
16486 waiting for the tasks dependent on that master to become terminated or
16487 waiting on a terminate Phase.
16489 @item Wait Child in Term Alt
16490 The task is sleeping waiting for tasks on terminate alternatives to
16491 finish terminating.
16493 @item Accepting RV with @var{taskno}
16494 The task is accepting a rendez-vous with the task @var{taskno}.
16498 Name of the task in the program.
16502 @kindex info task @var{taskno}
16503 @item info task @var{taskno}
16504 This command shows detailled informations on the specified task, as in
16505 the following example:
16510 (@value{GDBP}) info tasks
16511 ID TID P-ID Pri State Name
16512 1 8077880 0 15 Child Activation Wait main_task
16513 * 2 807c468 1 15 Runnable task_1
16514 (@value{GDBP}) info task 2
16515 Ada Task: 0x807c468
16518 Parent: 1 (main_task)
16524 @kindex task@r{ (Ada)}
16525 @cindex current Ada task ID
16526 This command prints the ID of the current task.
16532 (@value{GDBP}) info tasks
16533 ID TID P-ID Pri State Name
16534 1 8077870 0 15 Child Activation Wait main_task
16535 * 2 807c458 1 15 Runnable t
16536 (@value{GDBP}) task
16537 [Current task is 2]
16540 @item task @var{taskno}
16541 @cindex Ada task switching
16542 This command is like the @code{thread @var{thread-id}}
16543 command (@pxref{Threads}). It switches the context of debugging
16544 from the current task to the given task.
16550 (@value{GDBP}) info tasks
16551 ID TID P-ID Pri State Name
16552 1 8077870 0 15 Child Activation Wait main_task
16553 * 2 807c458 1 15 Runnable t
16554 (@value{GDBP}) task 1
16555 [Switching to task 1]
16556 #0 0x8067726 in pthread_cond_wait ()
16558 #0 0x8067726 in pthread_cond_wait ()
16559 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16560 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16561 #3 0x806153e in system.tasking.stages.activate_tasks ()
16562 #4 0x804aacc in un () at un.adb:5
16565 @item break @var{location} task @var{taskno}
16566 @itemx break @var{location} task @var{taskno} if @dots{}
16567 @cindex breakpoints and tasks, in Ada
16568 @cindex task breakpoints, in Ada
16569 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16570 These commands are like the @code{break @dots{} thread @dots{}}
16571 command (@pxref{Thread Stops}). The
16572 @var{location} argument specifies source lines, as described
16573 in @ref{Specify Location}.
16575 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16576 to specify that you only want @value{GDBN} to stop the program when a
16577 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16578 numeric task identifiers assigned by @value{GDBN}, shown in the first
16579 column of the @samp{info tasks} display.
16581 If you do not specify @samp{task @var{taskno}} when you set a
16582 breakpoint, the breakpoint applies to @emph{all} tasks of your
16585 You can use the @code{task} qualifier on conditional breakpoints as
16586 well; in this case, place @samp{task @var{taskno}} before the
16587 breakpoint condition (before the @code{if}).
16595 (@value{GDBP}) info tasks
16596 ID TID P-ID Pri State Name
16597 1 140022020 0 15 Child Activation Wait main_task
16598 2 140045060 1 15 Accept/Select Wait t2
16599 3 140044840 1 15 Runnable t1
16600 * 4 140056040 1 15 Runnable t3
16601 (@value{GDBP}) b 15 task 2
16602 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16603 (@value{GDBP}) cont
16608 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16610 (@value{GDBP}) info tasks
16611 ID TID P-ID Pri State Name
16612 1 140022020 0 15 Child Activation Wait main_task
16613 * 2 140045060 1 15 Runnable t2
16614 3 140044840 1 15 Runnable t1
16615 4 140056040 1 15 Delay Sleep t3
16619 @node Ada Tasks and Core Files
16620 @subsubsection Tasking Support when Debugging Core Files
16621 @cindex Ada tasking and core file debugging
16623 When inspecting a core file, as opposed to debugging a live program,
16624 tasking support may be limited or even unavailable, depending on
16625 the platform being used.
16626 For instance, on x86-linux, the list of tasks is available, but task
16627 switching is not supported.
16629 On certain platforms, the debugger needs to perform some
16630 memory writes in order to provide Ada tasking support. When inspecting
16631 a core file, this means that the core file must be opened with read-write
16632 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16633 Under these circumstances, you should make a backup copy of the core
16634 file before inspecting it with @value{GDBN}.
16636 @node Ravenscar Profile
16637 @subsubsection Tasking Support when using the Ravenscar Profile
16638 @cindex Ravenscar Profile
16640 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16641 specifically designed for systems with safety-critical real-time
16645 @kindex set ravenscar task-switching on
16646 @cindex task switching with program using Ravenscar Profile
16647 @item set ravenscar task-switching on
16648 Allows task switching when debugging a program that uses the Ravenscar
16649 Profile. This is the default.
16651 @kindex set ravenscar task-switching off
16652 @item set ravenscar task-switching off
16653 Turn off task switching when debugging a program that uses the Ravenscar
16654 Profile. This is mostly intended to disable the code that adds support
16655 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16656 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16657 To be effective, this command should be run before the program is started.
16659 @kindex show ravenscar task-switching
16660 @item show ravenscar task-switching
16661 Show whether it is possible to switch from task to task in a program
16662 using the Ravenscar Profile.
16667 @subsubsection Known Peculiarities of Ada Mode
16668 @cindex Ada, problems
16670 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16671 we know of several problems with and limitations of Ada mode in
16673 some of which will be fixed with planned future releases of the debugger
16674 and the GNU Ada compiler.
16678 Static constants that the compiler chooses not to materialize as objects in
16679 storage are invisible to the debugger.
16682 Named parameter associations in function argument lists are ignored (the
16683 argument lists are treated as positional).
16686 Many useful library packages are currently invisible to the debugger.
16689 Fixed-point arithmetic, conversions, input, and output is carried out using
16690 floating-point arithmetic, and may give results that only approximate those on
16694 The GNAT compiler never generates the prefix @code{Standard} for any of
16695 the standard symbols defined by the Ada language. @value{GDBN} knows about
16696 this: it will strip the prefix from names when you use it, and will never
16697 look for a name you have so qualified among local symbols, nor match against
16698 symbols in other packages or subprograms. If you have
16699 defined entities anywhere in your program other than parameters and
16700 local variables whose simple names match names in @code{Standard},
16701 GNAT's lack of qualification here can cause confusion. When this happens,
16702 you can usually resolve the confusion
16703 by qualifying the problematic names with package
16704 @code{Standard} explicitly.
16707 Older versions of the compiler sometimes generate erroneous debugging
16708 information, resulting in the debugger incorrectly printing the value
16709 of affected entities. In some cases, the debugger is able to work
16710 around an issue automatically. In other cases, the debugger is able
16711 to work around the issue, but the work-around has to be specifically
16714 @kindex set ada trust-PAD-over-XVS
16715 @kindex show ada trust-PAD-over-XVS
16718 @item set ada trust-PAD-over-XVS on
16719 Configure GDB to strictly follow the GNAT encoding when computing the
16720 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16721 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16722 a complete description of the encoding used by the GNAT compiler).
16723 This is the default.
16725 @item set ada trust-PAD-over-XVS off
16726 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16727 sometimes prints the wrong value for certain entities, changing @code{ada
16728 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16729 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16730 @code{off}, but this incurs a slight performance penalty, so it is
16731 recommended to leave this setting to @code{on} unless necessary.
16735 @cindex GNAT descriptive types
16736 @cindex GNAT encoding
16737 Internally, the debugger also relies on the compiler following a number
16738 of conventions known as the @samp{GNAT Encoding}, all documented in
16739 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16740 how the debugging information should be generated for certain types.
16741 In particular, this convention makes use of @dfn{descriptive types},
16742 which are artificial types generated purely to help the debugger.
16744 These encodings were defined at a time when the debugging information
16745 format used was not powerful enough to describe some of the more complex
16746 types available in Ada. Since DWARF allows us to express nearly all
16747 Ada features, the long-term goal is to slowly replace these descriptive
16748 types by their pure DWARF equivalent. To facilitate that transition,
16749 a new maintenance option is available to force the debugger to ignore
16750 those descriptive types. It allows the user to quickly evaluate how
16751 well @value{GDBN} works without them.
16755 @kindex maint ada set ignore-descriptive-types
16756 @item maintenance ada set ignore-descriptive-types [on|off]
16757 Control whether the debugger should ignore descriptive types.
16758 The default is not to ignore descriptives types (@code{off}).
16760 @kindex maint ada show ignore-descriptive-types
16761 @item maintenance ada show ignore-descriptive-types
16762 Show if descriptive types are ignored by @value{GDBN}.
16766 @node Unsupported Languages
16767 @section Unsupported Languages
16769 @cindex unsupported languages
16770 @cindex minimal language
16771 In addition to the other fully-supported programming languages,
16772 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16773 It does not represent a real programming language, but provides a set
16774 of capabilities close to what the C or assembly languages provide.
16775 This should allow most simple operations to be performed while debugging
16776 an application that uses a language currently not supported by @value{GDBN}.
16778 If the language is set to @code{auto}, @value{GDBN} will automatically
16779 select this language if the current frame corresponds to an unsupported
16783 @chapter Examining the Symbol Table
16785 The commands described in this chapter allow you to inquire about the
16786 symbols (names of variables, functions and types) defined in your
16787 program. This information is inherent in the text of your program and
16788 does not change as your program executes. @value{GDBN} finds it in your
16789 program's symbol table, in the file indicated when you started @value{GDBN}
16790 (@pxref{File Options, ,Choosing Files}), or by one of the
16791 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16793 @cindex symbol names
16794 @cindex names of symbols
16795 @cindex quoting names
16796 Occasionally, you may need to refer to symbols that contain unusual
16797 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16798 most frequent case is in referring to static variables in other
16799 source files (@pxref{Variables,,Program Variables}). File names
16800 are recorded in object files as debugging symbols, but @value{GDBN} would
16801 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16802 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16803 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16810 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16813 @cindex case-insensitive symbol names
16814 @cindex case sensitivity in symbol names
16815 @kindex set case-sensitive
16816 @item set case-sensitive on
16817 @itemx set case-sensitive off
16818 @itemx set case-sensitive auto
16819 Normally, when @value{GDBN} looks up symbols, it matches their names
16820 with case sensitivity determined by the current source language.
16821 Occasionally, you may wish to control that. The command @code{set
16822 case-sensitive} lets you do that by specifying @code{on} for
16823 case-sensitive matches or @code{off} for case-insensitive ones. If
16824 you specify @code{auto}, case sensitivity is reset to the default
16825 suitable for the source language. The default is case-sensitive
16826 matches for all languages except for Fortran, for which the default is
16827 case-insensitive matches.
16829 @kindex show case-sensitive
16830 @item show case-sensitive
16831 This command shows the current setting of case sensitivity for symbols
16834 @kindex set print type methods
16835 @item set print type methods
16836 @itemx set print type methods on
16837 @itemx set print type methods off
16838 Normally, when @value{GDBN} prints a class, it displays any methods
16839 declared in that class. You can control this behavior either by
16840 passing the appropriate flag to @code{ptype}, or using @command{set
16841 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16842 display the methods; this is the default. Specifying @code{off} will
16843 cause @value{GDBN} to omit the methods.
16845 @kindex show print type methods
16846 @item show print type methods
16847 This command shows the current setting of method display when printing
16850 @kindex set print type typedefs
16851 @item set print type typedefs
16852 @itemx set print type typedefs on
16853 @itemx set print type typedefs off
16855 Normally, when @value{GDBN} prints a class, it displays any typedefs
16856 defined in that class. You can control this behavior either by
16857 passing the appropriate flag to @code{ptype}, or using @command{set
16858 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16859 display the typedef definitions; this is the default. Specifying
16860 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16861 Note that this controls whether the typedef definition itself is
16862 printed, not whether typedef names are substituted when printing other
16865 @kindex show print type typedefs
16866 @item show print type typedefs
16867 This command shows the current setting of typedef display when
16870 @kindex info address
16871 @cindex address of a symbol
16872 @item info address @var{symbol}
16873 Describe where the data for @var{symbol} is stored. For a register
16874 variable, this says which register it is kept in. For a non-register
16875 local variable, this prints the stack-frame offset at which the variable
16878 Note the contrast with @samp{print &@var{symbol}}, which does not work
16879 at all for a register variable, and for a stack local variable prints
16880 the exact address of the current instantiation of the variable.
16882 @kindex info symbol
16883 @cindex symbol from address
16884 @cindex closest symbol and offset for an address
16885 @item info symbol @var{addr}
16886 Print the name of a symbol which is stored at the address @var{addr}.
16887 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16888 nearest symbol and an offset from it:
16891 (@value{GDBP}) info symbol 0x54320
16892 _initialize_vx + 396 in section .text
16896 This is the opposite of the @code{info address} command. You can use
16897 it to find out the name of a variable or a function given its address.
16899 For dynamically linked executables, the name of executable or shared
16900 library containing the symbol is also printed:
16903 (@value{GDBP}) info symbol 0x400225
16904 _start + 5 in section .text of /tmp/a.out
16905 (@value{GDBP}) info symbol 0x2aaaac2811cf
16906 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16911 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16912 Demangle @var{name}.
16913 If @var{language} is provided it is the name of the language to demangle
16914 @var{name} in. Otherwise @var{name} is demangled in the current language.
16916 The @samp{--} option specifies the end of options,
16917 and is useful when @var{name} begins with a dash.
16919 The parameter @code{demangle-style} specifies how to interpret the kind
16920 of mangling used. @xref{Print Settings}.
16923 @item whatis[/@var{flags}] [@var{arg}]
16924 Print the data type of @var{arg}, which can be either an expression
16925 or a name of a data type. With no argument, print the data type of
16926 @code{$}, the last value in the value history.
16928 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16929 is not actually evaluated, and any side-effecting operations (such as
16930 assignments or function calls) inside it do not take place.
16932 If @var{arg} is a variable or an expression, @code{whatis} prints its
16933 literal type as it is used in the source code. If the type was
16934 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16935 the data type underlying the @code{typedef}. If the type of the
16936 variable or the expression is a compound data type, such as
16937 @code{struct} or @code{class}, @code{whatis} never prints their
16938 fields or methods. It just prints the @code{struct}/@code{class}
16939 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16940 such a compound data type, use @code{ptype}.
16942 If @var{arg} is a type name that was defined using @code{typedef},
16943 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16944 Unrolling means that @code{whatis} will show the underlying type used
16945 in the @code{typedef} declaration of @var{arg}. However, if that
16946 underlying type is also a @code{typedef}, @code{whatis} will not
16949 For C code, the type names may also have the form @samp{class
16950 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16951 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16953 @var{flags} can be used to modify how the type is displayed.
16954 Available flags are:
16958 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16959 parameters and typedefs defined in a class when printing the class'
16960 members. The @code{/r} flag disables this.
16963 Do not print methods defined in the class.
16966 Print methods defined in the class. This is the default, but the flag
16967 exists in case you change the default with @command{set print type methods}.
16970 Do not print typedefs defined in the class. Note that this controls
16971 whether the typedef definition itself is printed, not whether typedef
16972 names are substituted when printing other types.
16975 Print typedefs defined in the class. This is the default, but the flag
16976 exists in case you change the default with @command{set print type typedefs}.
16980 @item ptype[/@var{flags}] [@var{arg}]
16981 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16982 detailed description of the type, instead of just the name of the type.
16983 @xref{Expressions, ,Expressions}.
16985 Contrary to @code{whatis}, @code{ptype} always unrolls any
16986 @code{typedef}s in its argument declaration, whether the argument is
16987 a variable, expression, or a data type. This means that @code{ptype}
16988 of a variable or an expression will not print literally its type as
16989 present in the source code---use @code{whatis} for that. @code{typedef}s at
16990 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16991 fields, methods and inner @code{class typedef}s of @code{struct}s,
16992 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16994 For example, for this variable declaration:
16997 typedef double real_t;
16998 struct complex @{ real_t real; double imag; @};
16999 typedef struct complex complex_t;
17001 real_t *real_pointer_var;
17005 the two commands give this output:
17009 (@value{GDBP}) whatis var
17011 (@value{GDBP}) ptype var
17012 type = struct complex @{
17016 (@value{GDBP}) whatis complex_t
17017 type = struct complex
17018 (@value{GDBP}) whatis struct complex
17019 type = struct complex
17020 (@value{GDBP}) ptype struct complex
17021 type = struct complex @{
17025 (@value{GDBP}) whatis real_pointer_var
17027 (@value{GDBP}) ptype real_pointer_var
17033 As with @code{whatis}, using @code{ptype} without an argument refers to
17034 the type of @code{$}, the last value in the value history.
17036 @cindex incomplete type
17037 Sometimes, programs use opaque data types or incomplete specifications
17038 of complex data structure. If the debug information included in the
17039 program does not allow @value{GDBN} to display a full declaration of
17040 the data type, it will say @samp{<incomplete type>}. For example,
17041 given these declarations:
17045 struct foo *fooptr;
17049 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17052 (@value{GDBP}) ptype foo
17053 $1 = <incomplete type>
17057 ``Incomplete type'' is C terminology for data types that are not
17058 completely specified.
17061 @item info types @var{regexp}
17063 Print a brief description of all types whose names match the regular
17064 expression @var{regexp} (or all types in your program, if you supply
17065 no argument). Each complete typename is matched as though it were a
17066 complete line; thus, @samp{i type value} gives information on all
17067 types in your program whose names include the string @code{value}, but
17068 @samp{i type ^value$} gives information only on types whose complete
17069 name is @code{value}.
17071 This command differs from @code{ptype} in two ways: first, like
17072 @code{whatis}, it does not print a detailed description; second, it
17073 lists all source files where a type is defined.
17075 @kindex info type-printers
17076 @item info type-printers
17077 Versions of @value{GDBN} that ship with Python scripting enabled may
17078 have ``type printers'' available. When using @command{ptype} or
17079 @command{whatis}, these printers are consulted when the name of a type
17080 is needed. @xref{Type Printing API}, for more information on writing
17083 @code{info type-printers} displays all the available type printers.
17085 @kindex enable type-printer
17086 @kindex disable type-printer
17087 @item enable type-printer @var{name}@dots{}
17088 @item disable type-printer @var{name}@dots{}
17089 These commands can be used to enable or disable type printers.
17092 @cindex local variables
17093 @item info scope @var{location}
17094 List all the variables local to a particular scope. This command
17095 accepts a @var{location} argument---a function name, a source line, or
17096 an address preceded by a @samp{*}, and prints all the variables local
17097 to the scope defined by that location. (@xref{Specify Location}, for
17098 details about supported forms of @var{location}.) For example:
17101 (@value{GDBP}) @b{info scope command_line_handler}
17102 Scope for command_line_handler:
17103 Symbol rl is an argument at stack/frame offset 8, length 4.
17104 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17105 Symbol linelength is in static storage at address 0x150a1c, length 4.
17106 Symbol p is a local variable in register $esi, length 4.
17107 Symbol p1 is a local variable in register $ebx, length 4.
17108 Symbol nline is a local variable in register $edx, length 4.
17109 Symbol repeat is a local variable at frame offset -8, length 4.
17113 This command is especially useful for determining what data to collect
17114 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17117 @kindex info source
17119 Show information about the current source file---that is, the source file for
17120 the function containing the current point of execution:
17123 the name of the source file, and the directory containing it,
17125 the directory it was compiled in,
17127 its length, in lines,
17129 which programming language it is written in,
17131 if the debug information provides it, the program that compiled the file
17132 (which may include, e.g., the compiler version and command line arguments),
17134 whether the executable includes debugging information for that file, and
17135 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17137 whether the debugging information includes information about
17138 preprocessor macros.
17142 @kindex info sources
17144 Print the names of all source files in your program for which there is
17145 debugging information, organized into two lists: files whose symbols
17146 have already been read, and files whose symbols will be read when needed.
17148 @kindex info functions
17149 @item info functions
17150 Print the names and data types of all defined functions.
17152 @item info functions @var{regexp}
17153 Print the names and data types of all defined functions
17154 whose names contain a match for regular expression @var{regexp}.
17155 Thus, @samp{info fun step} finds all functions whose names
17156 include @code{step}; @samp{info fun ^step} finds those whose names
17157 start with @code{step}. If a function name contains characters
17158 that conflict with the regular expression language (e.g.@:
17159 @samp{operator*()}), they may be quoted with a backslash.
17161 @kindex info variables
17162 @item info variables
17163 Print the names and data types of all variables that are defined
17164 outside of functions (i.e.@: excluding local variables).
17166 @item info variables @var{regexp}
17167 Print the names and data types of all variables (except for local
17168 variables) whose names contain a match for regular expression
17171 @kindex info classes
17172 @cindex Objective-C, classes and selectors
17174 @itemx info classes @var{regexp}
17175 Display all Objective-C classes in your program, or
17176 (with the @var{regexp} argument) all those matching a particular regular
17179 @kindex info selectors
17180 @item info selectors
17181 @itemx info selectors @var{regexp}
17182 Display all Objective-C selectors in your program, or
17183 (with the @var{regexp} argument) all those matching a particular regular
17187 This was never implemented.
17188 @kindex info methods
17190 @itemx info methods @var{regexp}
17191 The @code{info methods} command permits the user to examine all defined
17192 methods within C@t{++} program, or (with the @var{regexp} argument) a
17193 specific set of methods found in the various C@t{++} classes. Many
17194 C@t{++} classes provide a large number of methods. Thus, the output
17195 from the @code{ptype} command can be overwhelming and hard to use. The
17196 @code{info-methods} command filters the methods, printing only those
17197 which match the regular-expression @var{regexp}.
17200 @cindex opaque data types
17201 @kindex set opaque-type-resolution
17202 @item set opaque-type-resolution on
17203 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17204 declared as a pointer to a @code{struct}, @code{class}, or
17205 @code{union}---for example, @code{struct MyType *}---that is used in one
17206 source file although the full declaration of @code{struct MyType} is in
17207 another source file. The default is on.
17209 A change in the setting of this subcommand will not take effect until
17210 the next time symbols for a file are loaded.
17212 @item set opaque-type-resolution off
17213 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17214 is printed as follows:
17216 @{<no data fields>@}
17219 @kindex show opaque-type-resolution
17220 @item show opaque-type-resolution
17221 Show whether opaque types are resolved or not.
17223 @kindex set print symbol-loading
17224 @cindex print messages when symbols are loaded
17225 @item set print symbol-loading
17226 @itemx set print symbol-loading full
17227 @itemx set print symbol-loading brief
17228 @itemx set print symbol-loading off
17229 The @code{set print symbol-loading} command allows you to control the
17230 printing of messages when @value{GDBN} loads symbol information.
17231 By default a message is printed for the executable and one for each
17232 shared library, and normally this is what you want. However, when
17233 debugging apps with large numbers of shared libraries these messages
17235 When set to @code{brief} a message is printed for each executable,
17236 and when @value{GDBN} loads a collection of shared libraries at once
17237 it will only print one message regardless of the number of shared
17238 libraries. When set to @code{off} no messages are printed.
17240 @kindex show print symbol-loading
17241 @item show print symbol-loading
17242 Show whether messages will be printed when a @value{GDBN} command
17243 entered from the keyboard causes symbol information to be loaded.
17245 @kindex maint print symbols
17246 @cindex symbol dump
17247 @kindex maint print psymbols
17248 @cindex partial symbol dump
17249 @kindex maint print msymbols
17250 @cindex minimal symbol dump
17251 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17252 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17253 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17254 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17255 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17256 Write a dump of debugging symbol data into the file @var{filename} or
17257 the terminal if @var{filename} is unspecified.
17258 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17260 If @code{-pc @var{address}} is specified, only dump symbols for the file
17261 with code at that address. Note that @var{address} may be a symbol like
17263 If @code{-source @var{source}} is specified, only dump symbols for that
17266 These commands are used to debug the @value{GDBN} symbol-reading code.
17267 These commands do not modify internal @value{GDBN} state, therefore
17268 @samp{maint print symbols} will only print symbols for already expanded symbol
17270 You can use the command @code{info sources} to find out which files these are.
17271 If you use @samp{maint print psymbols} instead, the dump shows information
17272 about symbols that @value{GDBN} only knows partially---that is, symbols
17273 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17274 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17277 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17278 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17280 @kindex maint info symtabs
17281 @kindex maint info psymtabs
17282 @cindex listing @value{GDBN}'s internal symbol tables
17283 @cindex symbol tables, listing @value{GDBN}'s internal
17284 @cindex full symbol tables, listing @value{GDBN}'s internal
17285 @cindex partial symbol tables, listing @value{GDBN}'s internal
17286 @item maint info symtabs @r{[} @var{regexp} @r{]}
17287 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17289 List the @code{struct symtab} or @code{struct partial_symtab}
17290 structures whose names match @var{regexp}. If @var{regexp} is not
17291 given, list them all. The output includes expressions which you can
17292 copy into a @value{GDBN} debugging this one to examine a particular
17293 structure in more detail. For example:
17296 (@value{GDBP}) maint info psymtabs dwarf2read
17297 @{ objfile /home/gnu/build/gdb/gdb
17298 ((struct objfile *) 0x82e69d0)
17299 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17300 ((struct partial_symtab *) 0x8474b10)
17303 text addresses 0x814d3c8 -- 0x8158074
17304 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17305 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17306 dependencies (none)
17309 (@value{GDBP}) maint info symtabs
17313 We see that there is one partial symbol table whose filename contains
17314 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17315 and we see that @value{GDBN} has not read in any symtabs yet at all.
17316 If we set a breakpoint on a function, that will cause @value{GDBN} to
17317 read the symtab for the compilation unit containing that function:
17320 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17321 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17323 (@value{GDBP}) maint info symtabs
17324 @{ objfile /home/gnu/build/gdb/gdb
17325 ((struct objfile *) 0x82e69d0)
17326 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17327 ((struct symtab *) 0x86c1f38)
17330 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17331 linetable ((struct linetable *) 0x8370fa0)
17332 debugformat DWARF 2
17338 @kindex maint info line-table
17339 @cindex listing @value{GDBN}'s internal line tables
17340 @cindex line tables, listing @value{GDBN}'s internal
17341 @item maint info line-table @r{[} @var{regexp} @r{]}
17343 List the @code{struct linetable} from all @code{struct symtab}
17344 instances whose name matches @var{regexp}. If @var{regexp} is not
17345 given, list the @code{struct linetable} from all @code{struct symtab}.
17347 @kindex maint set symbol-cache-size
17348 @cindex symbol cache size
17349 @item maint set symbol-cache-size @var{size}
17350 Set the size of the symbol cache to @var{size}.
17351 The default size is intended to be good enough for debugging
17352 most applications. This option exists to allow for experimenting
17353 with different sizes.
17355 @kindex maint show symbol-cache-size
17356 @item maint show symbol-cache-size
17357 Show the size of the symbol cache.
17359 @kindex maint print symbol-cache
17360 @cindex symbol cache, printing its contents
17361 @item maint print symbol-cache
17362 Print the contents of the symbol cache.
17363 This is useful when debugging symbol cache issues.
17365 @kindex maint print symbol-cache-statistics
17366 @cindex symbol cache, printing usage statistics
17367 @item maint print symbol-cache-statistics
17368 Print symbol cache usage statistics.
17369 This helps determine how well the cache is being utilized.
17371 @kindex maint flush-symbol-cache
17372 @cindex symbol cache, flushing
17373 @item maint flush-symbol-cache
17374 Flush the contents of the symbol cache, all entries are removed.
17375 This command is useful when debugging the symbol cache.
17376 It is also useful when collecting performance data.
17381 @chapter Altering Execution
17383 Once you think you have found an error in your program, you might want to
17384 find out for certain whether correcting the apparent error would lead to
17385 correct results in the rest of the run. You can find the answer by
17386 experiment, using the @value{GDBN} features for altering execution of the
17389 For example, you can store new values into variables or memory
17390 locations, give your program a signal, restart it at a different
17391 address, or even return prematurely from a function.
17394 * Assignment:: Assignment to variables
17395 * Jumping:: Continuing at a different address
17396 * Signaling:: Giving your program a signal
17397 * Returning:: Returning from a function
17398 * Calling:: Calling your program's functions
17399 * Patching:: Patching your program
17400 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17404 @section Assignment to Variables
17407 @cindex setting variables
17408 To alter the value of a variable, evaluate an assignment expression.
17409 @xref{Expressions, ,Expressions}. For example,
17416 stores the value 4 into the variable @code{x}, and then prints the
17417 value of the assignment expression (which is 4).
17418 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17419 information on operators in supported languages.
17421 @kindex set variable
17422 @cindex variables, setting
17423 If you are not interested in seeing the value of the assignment, use the
17424 @code{set} command instead of the @code{print} command. @code{set} is
17425 really the same as @code{print} except that the expression's value is
17426 not printed and is not put in the value history (@pxref{Value History,
17427 ,Value History}). The expression is evaluated only for its effects.
17429 If the beginning of the argument string of the @code{set} command
17430 appears identical to a @code{set} subcommand, use the @code{set
17431 variable} command instead of just @code{set}. This command is identical
17432 to @code{set} except for its lack of subcommands. For example, if your
17433 program has a variable @code{width}, you get an error if you try to set
17434 a new value with just @samp{set width=13}, because @value{GDBN} has the
17435 command @code{set width}:
17438 (@value{GDBP}) whatis width
17440 (@value{GDBP}) p width
17442 (@value{GDBP}) set width=47
17443 Invalid syntax in expression.
17447 The invalid expression, of course, is @samp{=47}. In
17448 order to actually set the program's variable @code{width}, use
17451 (@value{GDBP}) set var width=47
17454 Because the @code{set} command has many subcommands that can conflict
17455 with the names of program variables, it is a good idea to use the
17456 @code{set variable} command instead of just @code{set}. For example, if
17457 your program has a variable @code{g}, you run into problems if you try
17458 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17459 the command @code{set gnutarget}, abbreviated @code{set g}:
17463 (@value{GDBP}) whatis g
17467 (@value{GDBP}) set g=4
17471 The program being debugged has been started already.
17472 Start it from the beginning? (y or n) y
17473 Starting program: /home/smith/cc_progs/a.out
17474 "/home/smith/cc_progs/a.out": can't open to read symbols:
17475 Invalid bfd target.
17476 (@value{GDBP}) show g
17477 The current BFD target is "=4".
17482 The program variable @code{g} did not change, and you silently set the
17483 @code{gnutarget} to an invalid value. In order to set the variable
17487 (@value{GDBP}) set var g=4
17490 @value{GDBN} allows more implicit conversions in assignments than C; you can
17491 freely store an integer value into a pointer variable or vice versa,
17492 and you can convert any structure to any other structure that is the
17493 same length or shorter.
17494 @comment FIXME: how do structs align/pad in these conversions?
17495 @comment /doc@cygnus.com 18dec1990
17497 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17498 construct to generate a value of specified type at a specified address
17499 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17500 to memory location @code{0x83040} as an integer (which implies a certain size
17501 and representation in memory), and
17504 set @{int@}0x83040 = 4
17508 stores the value 4 into that memory location.
17511 @section Continuing at a Different Address
17513 Ordinarily, when you continue your program, you do so at the place where
17514 it stopped, with the @code{continue} command. You can instead continue at
17515 an address of your own choosing, with the following commands:
17519 @kindex j @r{(@code{jump})}
17520 @item jump @var{location}
17521 @itemx j @var{location}
17522 Resume execution at @var{location}. Execution stops again immediately
17523 if there is a breakpoint there. @xref{Specify Location}, for a description
17524 of the different forms of @var{location}. It is common
17525 practice to use the @code{tbreak} command in conjunction with
17526 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17528 The @code{jump} command does not change the current stack frame, or
17529 the stack pointer, or the contents of any memory location or any
17530 register other than the program counter. If @var{location} is in
17531 a different function from the one currently executing, the results may
17532 be bizarre if the two functions expect different patterns of arguments or
17533 of local variables. For this reason, the @code{jump} command requests
17534 confirmation if the specified line is not in the function currently
17535 executing. However, even bizarre results are predictable if you are
17536 well acquainted with the machine-language code of your program.
17539 On many systems, you can get much the same effect as the @code{jump}
17540 command by storing a new value into the register @code{$pc}. The
17541 difference is that this does not start your program running; it only
17542 changes the address of where it @emph{will} run when you continue. For
17550 makes the next @code{continue} command or stepping command execute at
17551 address @code{0x485}, rather than at the address where your program stopped.
17552 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17554 The most common occasion to use the @code{jump} command is to back
17555 up---perhaps with more breakpoints set---over a portion of a program
17556 that has already executed, in order to examine its execution in more
17561 @section Giving your Program a Signal
17562 @cindex deliver a signal to a program
17566 @item signal @var{signal}
17567 Resume execution where your program is stopped, but immediately give it the
17568 signal @var{signal}. The @var{signal} can be the name or the number of a
17569 signal. For example, on many systems @code{signal 2} and @code{signal
17570 SIGINT} are both ways of sending an interrupt signal.
17572 Alternatively, if @var{signal} is zero, continue execution without
17573 giving a signal. This is useful when your program stopped on account of
17574 a signal and would ordinarily see the signal when resumed with the
17575 @code{continue} command; @samp{signal 0} causes it to resume without a
17578 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17579 delivered to the currently selected thread, not the thread that last
17580 reported a stop. This includes the situation where a thread was
17581 stopped due to a signal. So if you want to continue execution
17582 suppressing the signal that stopped a thread, you should select that
17583 same thread before issuing the @samp{signal 0} command. If you issue
17584 the @samp{signal 0} command with another thread as the selected one,
17585 @value{GDBN} detects that and asks for confirmation.
17587 Invoking the @code{signal} command is not the same as invoking the
17588 @code{kill} utility from the shell. Sending a signal with @code{kill}
17589 causes @value{GDBN} to decide what to do with the signal depending on
17590 the signal handling tables (@pxref{Signals}). The @code{signal} command
17591 passes the signal directly to your program.
17593 @code{signal} does not repeat when you press @key{RET} a second time
17594 after executing the command.
17596 @kindex queue-signal
17597 @item queue-signal @var{signal}
17598 Queue @var{signal} to be delivered immediately to the current thread
17599 when execution of the thread resumes. The @var{signal} can be the name or
17600 the number of a signal. For example, on many systems @code{signal 2} and
17601 @code{signal SIGINT} are both ways of sending an interrupt signal.
17602 The handling of the signal must be set to pass the signal to the program,
17603 otherwise @value{GDBN} will report an error.
17604 You can control the handling of signals from @value{GDBN} with the
17605 @code{handle} command (@pxref{Signals}).
17607 Alternatively, if @var{signal} is zero, any currently queued signal
17608 for the current thread is discarded and when execution resumes no signal
17609 will be delivered. This is useful when your program stopped on account
17610 of a signal and would ordinarily see the signal when resumed with the
17611 @code{continue} command.
17613 This command differs from the @code{signal} command in that the signal
17614 is just queued, execution is not resumed. And @code{queue-signal} cannot
17615 be used to pass a signal whose handling state has been set to @code{nopass}
17620 @xref{stepping into signal handlers}, for information on how stepping
17621 commands behave when the thread has a signal queued.
17624 @section Returning from a Function
17627 @cindex returning from a function
17630 @itemx return @var{expression}
17631 You can cancel execution of a function call with the @code{return}
17632 command. If you give an
17633 @var{expression} argument, its value is used as the function's return
17637 When you use @code{return}, @value{GDBN} discards the selected stack frame
17638 (and all frames within it). You can think of this as making the
17639 discarded frame return prematurely. If you wish to specify a value to
17640 be returned, give that value as the argument to @code{return}.
17642 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17643 Frame}), and any other frames inside of it, leaving its caller as the
17644 innermost remaining frame. That frame becomes selected. The
17645 specified value is stored in the registers used for returning values
17648 The @code{return} command does not resume execution; it leaves the
17649 program stopped in the state that would exist if the function had just
17650 returned. In contrast, the @code{finish} command (@pxref{Continuing
17651 and Stepping, ,Continuing and Stepping}) resumes execution until the
17652 selected stack frame returns naturally.
17654 @value{GDBN} needs to know how the @var{expression} argument should be set for
17655 the inferior. The concrete registers assignment depends on the OS ABI and the
17656 type being returned by the selected stack frame. For example it is common for
17657 OS ABI to return floating point values in FPU registers while integer values in
17658 CPU registers. Still some ABIs return even floating point values in CPU
17659 registers. Larger integer widths (such as @code{long long int}) also have
17660 specific placement rules. @value{GDBN} already knows the OS ABI from its
17661 current target so it needs to find out also the type being returned to make the
17662 assignment into the right register(s).
17664 Normally, the selected stack frame has debug info. @value{GDBN} will always
17665 use the debug info instead of the implicit type of @var{expression} when the
17666 debug info is available. For example, if you type @kbd{return -1}, and the
17667 function in the current stack frame is declared to return a @code{long long
17668 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17669 into a @code{long long int}:
17672 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17674 (@value{GDBP}) return -1
17675 Make func return now? (y or n) y
17676 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17677 43 printf ("result=%lld\n", func ());
17681 However, if the selected stack frame does not have a debug info, e.g., if the
17682 function was compiled without debug info, @value{GDBN} has to find out the type
17683 to return from user. Specifying a different type by mistake may set the value
17684 in different inferior registers than the caller code expects. For example,
17685 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17686 of a @code{long long int} result for a debug info less function (on 32-bit
17687 architectures). Therefore the user is required to specify the return type by
17688 an appropriate cast explicitly:
17691 Breakpoint 2, 0x0040050b in func ()
17692 (@value{GDBP}) return -1
17693 Return value type not available for selected stack frame.
17694 Please use an explicit cast of the value to return.
17695 (@value{GDBP}) return (long long int) -1
17696 Make selected stack frame return now? (y or n) y
17697 #0 0x00400526 in main ()
17702 @section Calling Program Functions
17705 @cindex calling functions
17706 @cindex inferior functions, calling
17707 @item print @var{expr}
17708 Evaluate the expression @var{expr} and display the resulting value.
17709 The expression may include calls to functions in the program being
17713 @item call @var{expr}
17714 Evaluate the expression @var{expr} without displaying @code{void}
17717 You can use this variant of the @code{print} command if you want to
17718 execute a function from your program that does not return anything
17719 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17720 with @code{void} returned values that @value{GDBN} will otherwise
17721 print. If the result is not void, it is printed and saved in the
17725 It is possible for the function you call via the @code{print} or
17726 @code{call} command to generate a signal (e.g., if there's a bug in
17727 the function, or if you passed it incorrect arguments). What happens
17728 in that case is controlled by the @code{set unwindonsignal} command.
17730 Similarly, with a C@t{++} program it is possible for the function you
17731 call via the @code{print} or @code{call} command to generate an
17732 exception that is not handled due to the constraints of the dummy
17733 frame. In this case, any exception that is raised in the frame, but has
17734 an out-of-frame exception handler will not be found. GDB builds a
17735 dummy-frame for the inferior function call, and the unwinder cannot
17736 seek for exception handlers outside of this dummy-frame. What happens
17737 in that case is controlled by the
17738 @code{set unwind-on-terminating-exception} command.
17741 @item set unwindonsignal
17742 @kindex set unwindonsignal
17743 @cindex unwind stack in called functions
17744 @cindex call dummy stack unwinding
17745 Set unwinding of the stack if a signal is received while in a function
17746 that @value{GDBN} called in the program being debugged. If set to on,
17747 @value{GDBN} unwinds the stack it created for the call and restores
17748 the context to what it was before the call. If set to off (the
17749 default), @value{GDBN} stops in the frame where the signal was
17752 @item show unwindonsignal
17753 @kindex show unwindonsignal
17754 Show the current setting of stack unwinding in the functions called by
17757 @item set unwind-on-terminating-exception
17758 @kindex set unwind-on-terminating-exception
17759 @cindex unwind stack in called functions with unhandled exceptions
17760 @cindex call dummy stack unwinding on unhandled exception.
17761 Set unwinding of the stack if a C@t{++} exception is raised, but left
17762 unhandled while in a function that @value{GDBN} called in the program being
17763 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17764 it created for the call and restores the context to what it was before
17765 the call. If set to off, @value{GDBN} the exception is delivered to
17766 the default C@t{++} exception handler and the inferior terminated.
17768 @item show unwind-on-terminating-exception
17769 @kindex show unwind-on-terminating-exception
17770 Show the current setting of stack unwinding in the functions called by
17775 @cindex weak alias functions
17776 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17777 for another function. In such case, @value{GDBN} might not pick up
17778 the type information, including the types of the function arguments,
17779 which causes @value{GDBN} to call the inferior function incorrectly.
17780 As a result, the called function will function erroneously and may
17781 even crash. A solution to that is to use the name of the aliased
17785 @section Patching Programs
17787 @cindex patching binaries
17788 @cindex writing into executables
17789 @cindex writing into corefiles
17791 By default, @value{GDBN} opens the file containing your program's
17792 executable code (or the corefile) read-only. This prevents accidental
17793 alterations to machine code; but it also prevents you from intentionally
17794 patching your program's binary.
17796 If you'd like to be able to patch the binary, you can specify that
17797 explicitly with the @code{set write} command. For example, you might
17798 want to turn on internal debugging flags, or even to make emergency
17804 @itemx set write off
17805 If you specify @samp{set write on}, @value{GDBN} opens executable and
17806 core files for both reading and writing; if you specify @kbd{set write
17807 off} (the default), @value{GDBN} opens them read-only.
17809 If you have already loaded a file, you must load it again (using the
17810 @code{exec-file} or @code{core-file} command) after changing @code{set
17811 write}, for your new setting to take effect.
17815 Display whether executable files and core files are opened for writing
17816 as well as reading.
17819 @node Compiling and Injecting Code
17820 @section Compiling and injecting code in @value{GDBN}
17821 @cindex injecting code
17822 @cindex writing into executables
17823 @cindex compiling code
17825 @value{GDBN} supports on-demand compilation and code injection into
17826 programs running under @value{GDBN}. GCC 5.0 or higher built with
17827 @file{libcc1.so} must be installed for this functionality to be enabled.
17828 This functionality is implemented with the following commands.
17831 @kindex compile code
17832 @item compile code @var{source-code}
17833 @itemx compile code -raw @var{--} @var{source-code}
17834 Compile @var{source-code} with the compiler language found as the current
17835 language in @value{GDBN} (@pxref{Languages}). If compilation and
17836 injection is not supported with the current language specified in
17837 @value{GDBN}, or the compiler does not support this feature, an error
17838 message will be printed. If @var{source-code} compiles and links
17839 successfully, @value{GDBN} will load the object-code emitted,
17840 and execute it within the context of the currently selected inferior.
17841 It is important to note that the compiled code is executed immediately.
17842 After execution, the compiled code is removed from @value{GDBN} and any
17843 new types or variables you have defined will be deleted.
17845 The command allows you to specify @var{source-code} in two ways.
17846 The simplest method is to provide a single line of code to the command.
17850 compile code printf ("hello world\n");
17853 If you specify options on the command line as well as source code, they
17854 may conflict. The @samp{--} delimiter can be used to separate options
17855 from actual source code. E.g.:
17858 compile code -r -- printf ("hello world\n");
17861 Alternatively you can enter source code as multiple lines of text. To
17862 enter this mode, invoke the @samp{compile code} command without any text
17863 following the command. This will start the multiple-line editor and
17864 allow you to type as many lines of source code as required. When you
17865 have completed typing, enter @samp{end} on its own line to exit the
17870 >printf ("hello\n");
17871 >printf ("world\n");
17875 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17876 provided @var{source-code} in a callable scope. In this case, you must
17877 specify the entry point of the code by defining a function named
17878 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17879 inferior. Using @samp{-raw} option may be needed for example when
17880 @var{source-code} requires @samp{#include} lines which may conflict with
17881 inferior symbols otherwise.
17883 @kindex compile file
17884 @item compile file @var{filename}
17885 @itemx compile file -raw @var{filename}
17886 Like @code{compile code}, but take the source code from @var{filename}.
17889 compile file /home/user/example.c
17894 @item compile print @var{expr}
17895 @itemx compile print /@var{f} @var{expr}
17896 Compile and execute @var{expr} with the compiler language found as the
17897 current language in @value{GDBN} (@pxref{Languages}). By default the
17898 value of @var{expr} is printed in a format appropriate to its data type;
17899 you can choose a different format by specifying @samp{/@var{f}}, where
17900 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17903 @item compile print
17904 @itemx compile print /@var{f}
17905 @cindex reprint the last value
17906 Alternatively you can enter the expression (source code producing it) as
17907 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17908 command without any text following the command. This will start the
17909 multiple-line editor.
17913 The process of compiling and injecting the code can be inspected using:
17916 @anchor{set debug compile}
17917 @item set debug compile
17918 @cindex compile command debugging info
17919 Turns on or off display of @value{GDBN} process of compiling and
17920 injecting the code. The default is off.
17922 @item show debug compile
17923 Displays the current state of displaying @value{GDBN} process of
17924 compiling and injecting the code.
17927 @subsection Compilation options for the @code{compile} command
17929 @value{GDBN} needs to specify the right compilation options for the code
17930 to be injected, in part to make its ABI compatible with the inferior
17931 and in part to make the injected code compatible with @value{GDBN}'s
17935 The options used, in increasing precedence:
17938 @item target architecture and OS options (@code{gdbarch})
17939 These options depend on target processor type and target operating
17940 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17941 (@code{-m64}) compilation option.
17943 @item compilation options recorded in the target
17944 @value{NGCC} (since version 4.7) stores the options used for compilation
17945 into @code{DW_AT_producer} part of DWARF debugging information according
17946 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17947 explicitly specify @code{-g} during inferior compilation otherwise
17948 @value{NGCC} produces no DWARF. This feature is only relevant for
17949 platforms where @code{-g} produces DWARF by default, otherwise one may
17950 try to enforce DWARF by using @code{-gdwarf-4}.
17952 @item compilation options set by @code{set compile-args}
17956 You can override compilation options using the following command:
17959 @item set compile-args
17960 @cindex compile command options override
17961 Set compilation options used for compiling and injecting code with the
17962 @code{compile} commands. These options override any conflicting ones
17963 from the target architecture and/or options stored during inferior
17966 @item show compile-args
17967 Displays the current state of compilation options override.
17968 This does not show all the options actually used during compilation,
17969 use @ref{set debug compile} for that.
17972 @subsection Caveats when using the @code{compile} command
17974 There are a few caveats to keep in mind when using the @code{compile}
17975 command. As the caveats are different per language, the table below
17976 highlights specific issues on a per language basis.
17979 @item C code examples and caveats
17980 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17981 attempt to compile the source code with a @samp{C} compiler. The source
17982 code provided to the @code{compile} command will have much the same
17983 access to variables and types as it normally would if it were part of
17984 the program currently being debugged in @value{GDBN}.
17986 Below is a sample program that forms the basis of the examples that
17987 follow. This program has been compiled and loaded into @value{GDBN},
17988 much like any other normal debugging session.
17991 void function1 (void)
17994 printf ("function 1\n");
17997 void function2 (void)
18012 For the purposes of the examples in this section, the program above has
18013 been compiled, loaded into @value{GDBN}, stopped at the function
18014 @code{main}, and @value{GDBN} is awaiting input from the user.
18016 To access variables and types for any program in @value{GDBN}, the
18017 program must be compiled and packaged with debug information. The
18018 @code{compile} command is not an exception to this rule. Without debug
18019 information, you can still use the @code{compile} command, but you will
18020 be very limited in what variables and types you can access.
18022 So with that in mind, the example above has been compiled with debug
18023 information enabled. The @code{compile} command will have access to
18024 all variables and types (except those that may have been optimized
18025 out). Currently, as @value{GDBN} has stopped the program in the
18026 @code{main} function, the @code{compile} command would have access to
18027 the variable @code{k}. You could invoke the @code{compile} command
18028 and type some source code to set the value of @code{k}. You can also
18029 read it, or do anything with that variable you would normally do in
18030 @code{C}. Be aware that changes to inferior variables in the
18031 @code{compile} command are persistent. In the following example:
18034 compile code k = 3;
18038 the variable @code{k} is now 3. It will retain that value until
18039 something else in the example program changes it, or another
18040 @code{compile} command changes it.
18042 Normal scope and access rules apply to source code compiled and
18043 injected by the @code{compile} command. In the example, the variables
18044 @code{j} and @code{k} are not accessible yet, because the program is
18045 currently stopped in the @code{main} function, where these variables
18046 are not in scope. Therefore, the following command
18049 compile code j = 3;
18053 will result in a compilation error message.
18055 Once the program is continued, execution will bring these variables in
18056 scope, and they will become accessible; then the code you specify via
18057 the @code{compile} command will be able to access them.
18059 You can create variables and types with the @code{compile} command as
18060 part of your source code. Variables and types that are created as part
18061 of the @code{compile} command are not visible to the rest of the program for
18062 the duration of its run. This example is valid:
18065 compile code int ff = 5; printf ("ff is %d\n", ff);
18068 However, if you were to type the following into @value{GDBN} after that
18069 command has completed:
18072 compile code printf ("ff is %d\n'', ff);
18076 a compiler error would be raised as the variable @code{ff} no longer
18077 exists. Object code generated and injected by the @code{compile}
18078 command is removed when its execution ends. Caution is advised
18079 when assigning to program variables values of variables created by the
18080 code submitted to the @code{compile} command. This example is valid:
18083 compile code int ff = 5; k = ff;
18086 The value of the variable @code{ff} is assigned to @code{k}. The variable
18087 @code{k} does not require the existence of @code{ff} to maintain the value
18088 it has been assigned. However, pointers require particular care in
18089 assignment. If the source code compiled with the @code{compile} command
18090 changed the address of a pointer in the example program, perhaps to a
18091 variable created in the @code{compile} command, that pointer would point
18092 to an invalid location when the command exits. The following example
18093 would likely cause issues with your debugged program:
18096 compile code int ff = 5; p = &ff;
18099 In this example, @code{p} would point to @code{ff} when the
18100 @code{compile} command is executing the source code provided to it.
18101 However, as variables in the (example) program persist with their
18102 assigned values, the variable @code{p} would point to an invalid
18103 location when the command exists. A general rule should be followed
18104 in that you should either assign @code{NULL} to any assigned pointers,
18105 or restore a valid location to the pointer before the command exits.
18107 Similar caution must be exercised with any structs, unions, and typedefs
18108 defined in @code{compile} command. Types defined in the @code{compile}
18109 command will no longer be available in the next @code{compile} command.
18110 Therefore, if you cast a variable to a type defined in the
18111 @code{compile} command, care must be taken to ensure that any future
18112 need to resolve the type can be achieved.
18115 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18116 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18117 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18118 Compilation failed.
18119 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18123 Variables that have been optimized away by the compiler are not
18124 accessible to the code submitted to the @code{compile} command.
18125 Access to those variables will generate a compiler error which @value{GDBN}
18126 will print to the console.
18129 @subsection Compiler search for the @code{compile} command
18131 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
18132 may not be obvious for remote targets of different architecture than where
18133 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
18134 shell that executed @value{GDBN}, not the one set by @value{GDBN}
18135 command @code{set environment}). @xref{Environment}. @code{PATH} on
18136 @value{GDBN} host is searched for @value{NGCC} binary matching the
18137 target architecture and operating system.
18139 Specifically @code{PATH} is searched for binaries matching regular expression
18140 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18141 debugged. @var{arch} is processor name --- multiarch is supported, so for
18142 example both @code{i386} and @code{x86_64} targets look for pattern
18143 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18144 for pattern @code{s390x?}. @var{os} is currently supported only for
18145 pattern @code{linux(-gnu)?}.
18148 @chapter @value{GDBN} Files
18150 @value{GDBN} needs to know the file name of the program to be debugged,
18151 both in order to read its symbol table and in order to start your
18152 program. To debug a core dump of a previous run, you must also tell
18153 @value{GDBN} the name of the core dump file.
18156 * Files:: Commands to specify files
18157 * File Caching:: Information about @value{GDBN}'s file caching
18158 * Separate Debug Files:: Debugging information in separate files
18159 * MiniDebugInfo:: Debugging information in a special section
18160 * Index Files:: Index files speed up GDB
18161 * Symbol Errors:: Errors reading symbol files
18162 * Data Files:: GDB data files
18166 @section Commands to Specify Files
18168 @cindex symbol table
18169 @cindex core dump file
18171 You may want to specify executable and core dump file names. The usual
18172 way to do this is at start-up time, using the arguments to
18173 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18174 Out of @value{GDBN}}).
18176 Occasionally it is necessary to change to a different file during a
18177 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18178 specify a file you want to use. Or you are debugging a remote target
18179 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18180 Program}). In these situations the @value{GDBN} commands to specify
18181 new files are useful.
18184 @cindex executable file
18186 @item file @var{filename}
18187 Use @var{filename} as the program to be debugged. It is read for its
18188 symbols and for the contents of pure memory. It is also the program
18189 executed when you use the @code{run} command. If you do not specify a
18190 directory and the file is not found in the @value{GDBN} working directory,
18191 @value{GDBN} uses the environment variable @code{PATH} as a list of
18192 directories to search, just as the shell does when looking for a program
18193 to run. You can change the value of this variable, for both @value{GDBN}
18194 and your program, using the @code{path} command.
18196 @cindex unlinked object files
18197 @cindex patching object files
18198 You can load unlinked object @file{.o} files into @value{GDBN} using
18199 the @code{file} command. You will not be able to ``run'' an object
18200 file, but you can disassemble functions and inspect variables. Also,
18201 if the underlying BFD functionality supports it, you could use
18202 @kbd{gdb -write} to patch object files using this technique. Note
18203 that @value{GDBN} can neither interpret nor modify relocations in this
18204 case, so branches and some initialized variables will appear to go to
18205 the wrong place. But this feature is still handy from time to time.
18208 @code{file} with no argument makes @value{GDBN} discard any information it
18209 has on both executable file and the symbol table.
18212 @item exec-file @r{[} @var{filename} @r{]}
18213 Specify that the program to be run (but not the symbol table) is found
18214 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18215 if necessary to locate your program. Omitting @var{filename} means to
18216 discard information on the executable file.
18218 @kindex symbol-file
18219 @item symbol-file @r{[} @var{filename} @r{]}
18220 Read symbol table information from file @var{filename}. @code{PATH} is
18221 searched when necessary. Use the @code{file} command to get both symbol
18222 table and program to run from the same file.
18224 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18225 program's symbol table.
18227 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18228 some breakpoints and auto-display expressions. This is because they may
18229 contain pointers to the internal data recording symbols and data types,
18230 which are part of the old symbol table data being discarded inside
18233 @code{symbol-file} does not repeat if you press @key{RET} again after
18236 When @value{GDBN} is configured for a particular environment, it
18237 understands debugging information in whatever format is the standard
18238 generated for that environment; you may use either a @sc{gnu} compiler, or
18239 other compilers that adhere to the local conventions.
18240 Best results are usually obtained from @sc{gnu} compilers; for example,
18241 using @code{@value{NGCC}} you can generate debugging information for
18244 For most kinds of object files, with the exception of old SVR3 systems
18245 using COFF, the @code{symbol-file} command does not normally read the
18246 symbol table in full right away. Instead, it scans the symbol table
18247 quickly to find which source files and which symbols are present. The
18248 details are read later, one source file at a time, as they are needed.
18250 The purpose of this two-stage reading strategy is to make @value{GDBN}
18251 start up faster. For the most part, it is invisible except for
18252 occasional pauses while the symbol table details for a particular source
18253 file are being read. (The @code{set verbose} command can turn these
18254 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18255 Warnings and Messages}.)
18257 We have not implemented the two-stage strategy for COFF yet. When the
18258 symbol table is stored in COFF format, @code{symbol-file} reads the
18259 symbol table data in full right away. Note that ``stabs-in-COFF''
18260 still does the two-stage strategy, since the debug info is actually
18264 @cindex reading symbols immediately
18265 @cindex symbols, reading immediately
18266 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18267 @itemx file @r{[} -readnow @r{]} @var{filename}
18268 You can override the @value{GDBN} two-stage strategy for reading symbol
18269 tables by using the @samp{-readnow} option with any of the commands that
18270 load symbol table information, if you want to be sure @value{GDBN} has the
18271 entire symbol table available.
18273 @c FIXME: for now no mention of directories, since this seems to be in
18274 @c flux. 13mar1992 status is that in theory GDB would look either in
18275 @c current dir or in same dir as myprog; but issues like competing
18276 @c GDB's, or clutter in system dirs, mean that in practice right now
18277 @c only current dir is used. FFish says maybe a special GDB hierarchy
18278 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18282 @item core-file @r{[}@var{filename}@r{]}
18284 Specify the whereabouts of a core dump file to be used as the ``contents
18285 of memory''. Traditionally, core files contain only some parts of the
18286 address space of the process that generated them; @value{GDBN} can access the
18287 executable file itself for other parts.
18289 @code{core-file} with no argument specifies that no core file is
18292 Note that the core file is ignored when your program is actually running
18293 under @value{GDBN}. So, if you have been running your program and you
18294 wish to debug a core file instead, you must kill the subprocess in which
18295 the program is running. To do this, use the @code{kill} command
18296 (@pxref{Kill Process, ,Killing the Child Process}).
18298 @kindex add-symbol-file
18299 @cindex dynamic linking
18300 @item add-symbol-file @var{filename} @var{address}
18301 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18302 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18303 The @code{add-symbol-file} command reads additional symbol table
18304 information from the file @var{filename}. You would use this command
18305 when @var{filename} has been dynamically loaded (by some other means)
18306 into the program that is running. The @var{address} should give the memory
18307 address at which the file has been loaded; @value{GDBN} cannot figure
18308 this out for itself. You can additionally specify an arbitrary number
18309 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18310 section name and base address for that section. You can specify any
18311 @var{address} as an expression.
18313 The symbol table of the file @var{filename} is added to the symbol table
18314 originally read with the @code{symbol-file} command. You can use the
18315 @code{add-symbol-file} command any number of times; the new symbol data
18316 thus read is kept in addition to the old.
18318 Changes can be reverted using the command @code{remove-symbol-file}.
18320 @cindex relocatable object files, reading symbols from
18321 @cindex object files, relocatable, reading symbols from
18322 @cindex reading symbols from relocatable object files
18323 @cindex symbols, reading from relocatable object files
18324 @cindex @file{.o} files, reading symbols from
18325 Although @var{filename} is typically a shared library file, an
18326 executable file, or some other object file which has been fully
18327 relocated for loading into a process, you can also load symbolic
18328 information from relocatable @file{.o} files, as long as:
18332 the file's symbolic information refers only to linker symbols defined in
18333 that file, not to symbols defined by other object files,
18335 every section the file's symbolic information refers to has actually
18336 been loaded into the inferior, as it appears in the file, and
18338 you can determine the address at which every section was loaded, and
18339 provide these to the @code{add-symbol-file} command.
18343 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18344 relocatable files into an already running program; such systems
18345 typically make the requirements above easy to meet. However, it's
18346 important to recognize that many native systems use complex link
18347 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18348 assembly, for example) that make the requirements difficult to meet. In
18349 general, one cannot assume that using @code{add-symbol-file} to read a
18350 relocatable object file's symbolic information will have the same effect
18351 as linking the relocatable object file into the program in the normal
18354 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18356 @kindex remove-symbol-file
18357 @item remove-symbol-file @var{filename}
18358 @item remove-symbol-file -a @var{address}
18359 Remove a symbol file added via the @code{add-symbol-file} command. The
18360 file to remove can be identified by its @var{filename} or by an @var{address}
18361 that lies within the boundaries of this symbol file in memory. Example:
18364 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18365 add symbol table from file "/home/user/gdb/mylib.so" at
18366 .text_addr = 0x7ffff7ff9480
18368 Reading symbols from /home/user/gdb/mylib.so...done.
18369 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18370 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18375 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18377 @kindex add-symbol-file-from-memory
18378 @cindex @code{syscall DSO}
18379 @cindex load symbols from memory
18380 @item add-symbol-file-from-memory @var{address}
18381 Load symbols from the given @var{address} in a dynamically loaded
18382 object file whose image is mapped directly into the inferior's memory.
18383 For example, the Linux kernel maps a @code{syscall DSO} into each
18384 process's address space; this DSO provides kernel-specific code for
18385 some system calls. The argument can be any expression whose
18386 evaluation yields the address of the file's shared object file header.
18387 For this command to work, you must have used @code{symbol-file} or
18388 @code{exec-file} commands in advance.
18391 @item section @var{section} @var{addr}
18392 The @code{section} command changes the base address of the named
18393 @var{section} of the exec file to @var{addr}. This can be used if the
18394 exec file does not contain section addresses, (such as in the
18395 @code{a.out} format), or when the addresses specified in the file
18396 itself are wrong. Each section must be changed separately. The
18397 @code{info files} command, described below, lists all the sections and
18401 @kindex info target
18404 @code{info files} and @code{info target} are synonymous; both print the
18405 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18406 including the names of the executable and core dump files currently in
18407 use by @value{GDBN}, and the files from which symbols were loaded. The
18408 command @code{help target} lists all possible targets rather than
18411 @kindex maint info sections
18412 @item maint info sections
18413 Another command that can give you extra information about program sections
18414 is @code{maint info sections}. In addition to the section information
18415 displayed by @code{info files}, this command displays the flags and file
18416 offset of each section in the executable and core dump files. In addition,
18417 @code{maint info sections} provides the following command options (which
18418 may be arbitrarily combined):
18422 Display sections for all loaded object files, including shared libraries.
18423 @item @var{sections}
18424 Display info only for named @var{sections}.
18425 @item @var{section-flags}
18426 Display info only for sections for which @var{section-flags} are true.
18427 The section flags that @value{GDBN} currently knows about are:
18430 Section will have space allocated in the process when loaded.
18431 Set for all sections except those containing debug information.
18433 Section will be loaded from the file into the child process memory.
18434 Set for pre-initialized code and data, clear for @code{.bss} sections.
18436 Section needs to be relocated before loading.
18438 Section cannot be modified by the child process.
18440 Section contains executable code only.
18442 Section contains data only (no executable code).
18444 Section will reside in ROM.
18446 Section contains data for constructor/destructor lists.
18448 Section is not empty.
18450 An instruction to the linker to not output the section.
18451 @item COFF_SHARED_LIBRARY
18452 A notification to the linker that the section contains
18453 COFF shared library information.
18455 Section contains common symbols.
18458 @kindex set trust-readonly-sections
18459 @cindex read-only sections
18460 @item set trust-readonly-sections on
18461 Tell @value{GDBN} that readonly sections in your object file
18462 really are read-only (i.e.@: that their contents will not change).
18463 In that case, @value{GDBN} can fetch values from these sections
18464 out of the object file, rather than from the target program.
18465 For some targets (notably embedded ones), this can be a significant
18466 enhancement to debugging performance.
18468 The default is off.
18470 @item set trust-readonly-sections off
18471 Tell @value{GDBN} not to trust readonly sections. This means that
18472 the contents of the section might change while the program is running,
18473 and must therefore be fetched from the target when needed.
18475 @item show trust-readonly-sections
18476 Show the current setting of trusting readonly sections.
18479 All file-specifying commands allow both absolute and relative file names
18480 as arguments. @value{GDBN} always converts the file name to an absolute file
18481 name and remembers it that way.
18483 @cindex shared libraries
18484 @anchor{Shared Libraries}
18485 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18486 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18487 DSBT (TIC6X) shared libraries.
18489 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18490 shared libraries. @xref{Expat}.
18492 @value{GDBN} automatically loads symbol definitions from shared libraries
18493 when you use the @code{run} command, or when you examine a core file.
18494 (Before you issue the @code{run} command, @value{GDBN} does not understand
18495 references to a function in a shared library, however---unless you are
18496 debugging a core file).
18498 @c FIXME: some @value{GDBN} release may permit some refs to undef
18499 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18500 @c FIXME...lib; check this from time to time when updating manual
18502 There are times, however, when you may wish to not automatically load
18503 symbol definitions from shared libraries, such as when they are
18504 particularly large or there are many of them.
18506 To control the automatic loading of shared library symbols, use the
18510 @kindex set auto-solib-add
18511 @item set auto-solib-add @var{mode}
18512 If @var{mode} is @code{on}, symbols from all shared object libraries
18513 will be loaded automatically when the inferior begins execution, you
18514 attach to an independently started inferior, or when the dynamic linker
18515 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18516 is @code{off}, symbols must be loaded manually, using the
18517 @code{sharedlibrary} command. The default value is @code{on}.
18519 @cindex memory used for symbol tables
18520 If your program uses lots of shared libraries with debug info that
18521 takes large amounts of memory, you can decrease the @value{GDBN}
18522 memory footprint by preventing it from automatically loading the
18523 symbols from shared libraries. To that end, type @kbd{set
18524 auto-solib-add off} before running the inferior, then load each
18525 library whose debug symbols you do need with @kbd{sharedlibrary
18526 @var{regexp}}, where @var{regexp} is a regular expression that matches
18527 the libraries whose symbols you want to be loaded.
18529 @kindex show auto-solib-add
18530 @item show auto-solib-add
18531 Display the current autoloading mode.
18534 @cindex load shared library
18535 To explicitly load shared library symbols, use the @code{sharedlibrary}
18539 @kindex info sharedlibrary
18541 @item info share @var{regex}
18542 @itemx info sharedlibrary @var{regex}
18543 Print the names of the shared libraries which are currently loaded
18544 that match @var{regex}. If @var{regex} is omitted then print
18545 all shared libraries that are loaded.
18548 @item info dll @var{regex}
18549 This is an alias of @code{info sharedlibrary}.
18551 @kindex sharedlibrary
18553 @item sharedlibrary @var{regex}
18554 @itemx share @var{regex}
18555 Load shared object library symbols for files matching a
18556 Unix regular expression.
18557 As with files loaded automatically, it only loads shared libraries
18558 required by your program for a core file or after typing @code{run}. If
18559 @var{regex} is omitted all shared libraries required by your program are
18562 @item nosharedlibrary
18563 @kindex nosharedlibrary
18564 @cindex unload symbols from shared libraries
18565 Unload all shared object library symbols. This discards all symbols
18566 that have been loaded from all shared libraries. Symbols from shared
18567 libraries that were loaded by explicit user requests are not
18571 Sometimes you may wish that @value{GDBN} stops and gives you control
18572 when any of shared library events happen. The best way to do this is
18573 to use @code{catch load} and @code{catch unload} (@pxref{Set
18576 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18577 command for this. This command exists for historical reasons. It is
18578 less useful than setting a catchpoint, because it does not allow for
18579 conditions or commands as a catchpoint does.
18582 @item set stop-on-solib-events
18583 @kindex set stop-on-solib-events
18584 This command controls whether @value{GDBN} should give you control
18585 when the dynamic linker notifies it about some shared library event.
18586 The most common event of interest is loading or unloading of a new
18589 @item show stop-on-solib-events
18590 @kindex show stop-on-solib-events
18591 Show whether @value{GDBN} stops and gives you control when shared
18592 library events happen.
18595 Shared libraries are also supported in many cross or remote debugging
18596 configurations. @value{GDBN} needs to have access to the target's libraries;
18597 this can be accomplished either by providing copies of the libraries
18598 on the host system, or by asking @value{GDBN} to automatically retrieve the
18599 libraries from the target. If copies of the target libraries are
18600 provided, they need to be the same as the target libraries, although the
18601 copies on the target can be stripped as long as the copies on the host are
18604 @cindex where to look for shared libraries
18605 For remote debugging, you need to tell @value{GDBN} where the target
18606 libraries are, so that it can load the correct copies---otherwise, it
18607 may try to load the host's libraries. @value{GDBN} has two variables
18608 to specify the search directories for target libraries.
18611 @cindex prefix for executable and shared library file names
18612 @cindex system root, alternate
18613 @kindex set solib-absolute-prefix
18614 @kindex set sysroot
18615 @item set sysroot @var{path}
18616 Use @var{path} as the system root for the program being debugged. Any
18617 absolute shared library paths will be prefixed with @var{path}; many
18618 runtime loaders store the absolute paths to the shared library in the
18619 target program's memory. When starting processes remotely, and when
18620 attaching to already-running processes (local or remote), their
18621 executable filenames will be prefixed with @var{path} if reported to
18622 @value{GDBN} as absolute by the operating system. If you use
18623 @code{set sysroot} to find executables and shared libraries, they need
18624 to be laid out in the same way that they are on the target, with
18625 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18628 If @var{path} starts with the sequence @file{target:} and the target
18629 system is remote then @value{GDBN} will retrieve the target binaries
18630 from the remote system. This is only supported when using a remote
18631 target that supports the @code{remote get} command (@pxref{File
18632 Transfer,,Sending files to a remote system}). The part of @var{path}
18633 following the initial @file{target:} (if present) is used as system
18634 root prefix on the remote file system. If @var{path} starts with the
18635 sequence @file{remote:} this is converted to the sequence
18636 @file{target:} by @code{set sysroot}@footnote{Historically the
18637 functionality to retrieve binaries from the remote system was
18638 provided by prefixing @var{path} with @file{remote:}}. If you want
18639 to specify a local system root using a directory that happens to be
18640 named @file{target:} or @file{remote:}, you need to use some
18641 equivalent variant of the name like @file{./target:}.
18643 For targets with an MS-DOS based filesystem, such as MS-Windows and
18644 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18645 absolute file name with @var{path}. But first, on Unix hosts,
18646 @value{GDBN} converts all backslash directory separators into forward
18647 slashes, because the backslash is not a directory separator on Unix:
18650 c:\foo\bar.dll @result{} c:/foo/bar.dll
18653 Then, @value{GDBN} attempts prefixing the target file name with
18654 @var{path}, and looks for the resulting file name in the host file
18658 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18661 If that does not find the binary, @value{GDBN} tries removing
18662 the @samp{:} character from the drive spec, both for convenience, and,
18663 for the case of the host file system not supporting file names with
18667 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18670 This makes it possible to have a system root that mirrors a target
18671 with more than one drive. E.g., you may want to setup your local
18672 copies of the target system shared libraries like so (note @samp{c} vs
18676 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18677 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18678 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18682 and point the system root at @file{/path/to/sysroot}, so that
18683 @value{GDBN} can find the correct copies of both
18684 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18686 If that still does not find the binary, @value{GDBN} tries
18687 removing the whole drive spec from the target file name:
18690 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18693 This last lookup makes it possible to not care about the drive name,
18694 if you don't want or need to.
18696 The @code{set solib-absolute-prefix} command is an alias for @code{set
18699 @cindex default system root
18700 @cindex @samp{--with-sysroot}
18701 You can set the default system root by using the configure-time
18702 @samp{--with-sysroot} option. If the system root is inside
18703 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18704 @samp{--exec-prefix}), then the default system root will be updated
18705 automatically if the installed @value{GDBN} is moved to a new
18708 @kindex show sysroot
18710 Display the current executable and shared library prefix.
18712 @kindex set solib-search-path
18713 @item set solib-search-path @var{path}
18714 If this variable is set, @var{path} is a colon-separated list of
18715 directories to search for shared libraries. @samp{solib-search-path}
18716 is used after @samp{sysroot} fails to locate the library, or if the
18717 path to the library is relative instead of absolute. If you want to
18718 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18719 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18720 finding your host's libraries. @samp{sysroot} is preferred; setting
18721 it to a nonexistent directory may interfere with automatic loading
18722 of shared library symbols.
18724 @kindex show solib-search-path
18725 @item show solib-search-path
18726 Display the current shared library search path.
18728 @cindex DOS file-name semantics of file names.
18729 @kindex set target-file-system-kind (unix|dos-based|auto)
18730 @kindex show target-file-system-kind
18731 @item set target-file-system-kind @var{kind}
18732 Set assumed file system kind for target reported file names.
18734 Shared library file names as reported by the target system may not
18735 make sense as is on the system @value{GDBN} is running on. For
18736 example, when remote debugging a target that has MS-DOS based file
18737 system semantics, from a Unix host, the target may be reporting to
18738 @value{GDBN} a list of loaded shared libraries with file names such as
18739 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18740 drive letters, so the @samp{c:\} prefix is not normally understood as
18741 indicating an absolute file name, and neither is the backslash
18742 normally considered a directory separator character. In that case,
18743 the native file system would interpret this whole absolute file name
18744 as a relative file name with no directory components. This would make
18745 it impossible to point @value{GDBN} at a copy of the remote target's
18746 shared libraries on the host using @code{set sysroot}, and impractical
18747 with @code{set solib-search-path}. Setting
18748 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18749 to interpret such file names similarly to how the target would, and to
18750 map them to file names valid on @value{GDBN}'s native file system
18751 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18752 to one of the supported file system kinds. In that case, @value{GDBN}
18753 tries to determine the appropriate file system variant based on the
18754 current target's operating system (@pxref{ABI, ,Configuring the
18755 Current ABI}). The supported file system settings are:
18759 Instruct @value{GDBN} to assume the target file system is of Unix
18760 kind. Only file names starting the forward slash (@samp{/}) character
18761 are considered absolute, and the directory separator character is also
18765 Instruct @value{GDBN} to assume the target file system is DOS based.
18766 File names starting with either a forward slash, or a drive letter
18767 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18768 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18769 considered directory separators.
18772 Instruct @value{GDBN} to use the file system kind associated with the
18773 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18774 This is the default.
18778 @cindex file name canonicalization
18779 @cindex base name differences
18780 When processing file names provided by the user, @value{GDBN}
18781 frequently needs to compare them to the file names recorded in the
18782 program's debug info. Normally, @value{GDBN} compares just the
18783 @dfn{base names} of the files as strings, which is reasonably fast
18784 even for very large programs. (The base name of a file is the last
18785 portion of its name, after stripping all the leading directories.)
18786 This shortcut in comparison is based upon the assumption that files
18787 cannot have more than one base name. This is usually true, but
18788 references to files that use symlinks or similar filesystem
18789 facilities violate that assumption. If your program records files
18790 using such facilities, or if you provide file names to @value{GDBN}
18791 using symlinks etc., you can set @code{basenames-may-differ} to
18792 @code{true} to instruct @value{GDBN} to completely canonicalize each
18793 pair of file names it needs to compare. This will make file-name
18794 comparisons accurate, but at a price of a significant slowdown.
18797 @item set basenames-may-differ
18798 @kindex set basenames-may-differ
18799 Set whether a source file may have multiple base names.
18801 @item show basenames-may-differ
18802 @kindex show basenames-may-differ
18803 Show whether a source file may have multiple base names.
18807 @section File Caching
18808 @cindex caching of opened files
18809 @cindex caching of bfd objects
18811 To speed up file loading, and reduce memory usage, @value{GDBN} will
18812 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18813 BFD, bfd, The Binary File Descriptor Library}. The following commands
18814 allow visibility and control of the caching behavior.
18817 @kindex maint info bfds
18818 @item maint info bfds
18819 This prints information about each @code{bfd} object that is known to
18822 @kindex maint set bfd-sharing
18823 @kindex maint show bfd-sharing
18824 @kindex bfd caching
18825 @item maint set bfd-sharing
18826 @item maint show bfd-sharing
18827 Control whether @code{bfd} objects can be shared. When sharing is
18828 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18829 than reopening the same file. Turning sharing off does not cause
18830 already shared @code{bfd} objects to be unshared, but all future files
18831 that are opened will create a new @code{bfd} object. Similarly,
18832 re-enabling sharing does not cause multiple existing @code{bfd}
18833 objects to be collapsed into a single shared @code{bfd} object.
18835 @kindex set debug bfd-cache @var{level}
18836 @kindex bfd caching
18837 @item set debug bfd-cache @var{level}
18838 Turns on debugging of the bfd cache, setting the level to @var{level}.
18840 @kindex show debug bfd-cache
18841 @kindex bfd caching
18842 @item show debug bfd-cache
18843 Show the current debugging level of the bfd cache.
18846 @node Separate Debug Files
18847 @section Debugging Information in Separate Files
18848 @cindex separate debugging information files
18849 @cindex debugging information in separate files
18850 @cindex @file{.debug} subdirectories
18851 @cindex debugging information directory, global
18852 @cindex global debugging information directories
18853 @cindex build ID, and separate debugging files
18854 @cindex @file{.build-id} directory
18856 @value{GDBN} allows you to put a program's debugging information in a
18857 file separate from the executable itself, in a way that allows
18858 @value{GDBN} to find and load the debugging information automatically.
18859 Since debugging information can be very large---sometimes larger
18860 than the executable code itself---some systems distribute debugging
18861 information for their executables in separate files, which users can
18862 install only when they need to debug a problem.
18864 @value{GDBN} supports two ways of specifying the separate debug info
18869 The executable contains a @dfn{debug link} that specifies the name of
18870 the separate debug info file. The separate debug file's name is
18871 usually @file{@var{executable}.debug}, where @var{executable} is the
18872 name of the corresponding executable file without leading directories
18873 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18874 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18875 checksum for the debug file, which @value{GDBN} uses to validate that
18876 the executable and the debug file came from the same build.
18879 The executable contains a @dfn{build ID}, a unique bit string that is
18880 also present in the corresponding debug info file. (This is supported
18881 only on some operating systems, when using the ELF or PE file formats
18882 for binary files and the @sc{gnu} Binutils.) For more details about
18883 this feature, see the description of the @option{--build-id}
18884 command-line option in @ref{Options, , Command Line Options, ld.info,
18885 The GNU Linker}. The debug info file's name is not specified
18886 explicitly by the build ID, but can be computed from the build ID, see
18890 Depending on the way the debug info file is specified, @value{GDBN}
18891 uses two different methods of looking for the debug file:
18895 For the ``debug link'' method, @value{GDBN} looks up the named file in
18896 the directory of the executable file, then in a subdirectory of that
18897 directory named @file{.debug}, and finally under each one of the global debug
18898 directories, in a subdirectory whose name is identical to the leading
18899 directories of the executable's absolute file name.
18902 For the ``build ID'' method, @value{GDBN} looks in the
18903 @file{.build-id} subdirectory of each one of the global debug directories for
18904 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18905 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18906 are the rest of the bit string. (Real build ID strings are 32 or more
18907 hex characters, not 10.)
18910 So, for example, suppose you ask @value{GDBN} to debug
18911 @file{/usr/bin/ls}, which has a debug link that specifies the
18912 file @file{ls.debug}, and a build ID whose value in hex is
18913 @code{abcdef1234}. If the list of the global debug directories includes
18914 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18915 debug information files, in the indicated order:
18919 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18921 @file{/usr/bin/ls.debug}
18923 @file{/usr/bin/.debug/ls.debug}
18925 @file{/usr/lib/debug/usr/bin/ls.debug}.
18928 @anchor{debug-file-directory}
18929 Global debugging info directories default to what is set by @value{GDBN}
18930 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18931 you can also set the global debugging info directories, and view the list
18932 @value{GDBN} is currently using.
18936 @kindex set debug-file-directory
18937 @item set debug-file-directory @var{directories}
18938 Set the directories which @value{GDBN} searches for separate debugging
18939 information files to @var{directory}. Multiple path components can be set
18940 concatenating them by a path separator.
18942 @kindex show debug-file-directory
18943 @item show debug-file-directory
18944 Show the directories @value{GDBN} searches for separate debugging
18949 @cindex @code{.gnu_debuglink} sections
18950 @cindex debug link sections
18951 A debug link is a special section of the executable file named
18952 @code{.gnu_debuglink}. The section must contain:
18956 A filename, with any leading directory components removed, followed by
18959 zero to three bytes of padding, as needed to reach the next four-byte
18960 boundary within the section, and
18962 a four-byte CRC checksum, stored in the same endianness used for the
18963 executable file itself. The checksum is computed on the debugging
18964 information file's full contents by the function given below, passing
18965 zero as the @var{crc} argument.
18968 Any executable file format can carry a debug link, as long as it can
18969 contain a section named @code{.gnu_debuglink} with the contents
18972 @cindex @code{.note.gnu.build-id} sections
18973 @cindex build ID sections
18974 The build ID is a special section in the executable file (and in other
18975 ELF binary files that @value{GDBN} may consider). This section is
18976 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18977 It contains unique identification for the built files---the ID remains
18978 the same across multiple builds of the same build tree. The default
18979 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18980 content for the build ID string. The same section with an identical
18981 value is present in the original built binary with symbols, in its
18982 stripped variant, and in the separate debugging information file.
18984 The debugging information file itself should be an ordinary
18985 executable, containing a full set of linker symbols, sections, and
18986 debugging information. The sections of the debugging information file
18987 should have the same names, addresses, and sizes as the original file,
18988 but they need not contain any data---much like a @code{.bss} section
18989 in an ordinary executable.
18991 The @sc{gnu} binary utilities (Binutils) package includes the
18992 @samp{objcopy} utility that can produce
18993 the separated executable / debugging information file pairs using the
18994 following commands:
18997 @kbd{objcopy --only-keep-debug foo foo.debug}
19002 These commands remove the debugging
19003 information from the executable file @file{foo} and place it in the file
19004 @file{foo.debug}. You can use the first, second or both methods to link the
19009 The debug link method needs the following additional command to also leave
19010 behind a debug link in @file{foo}:
19013 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19016 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19017 a version of the @code{strip} command such that the command @kbd{strip foo -f
19018 foo.debug} has the same functionality as the two @code{objcopy} commands and
19019 the @code{ln -s} command above, together.
19022 Build ID gets embedded into the main executable using @code{ld --build-id} or
19023 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19024 compatibility fixes for debug files separation are present in @sc{gnu} binary
19025 utilities (Binutils) package since version 2.18.
19030 @cindex CRC algorithm definition
19031 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19032 IEEE 802.3 using the polynomial:
19034 @c TexInfo requires naked braces for multi-digit exponents for Tex
19035 @c output, but this causes HTML output to barf. HTML has to be set using
19036 @c raw commands. So we end up having to specify this equation in 2
19041 <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>
19042 + <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
19048 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19049 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19053 The function is computed byte at a time, taking the least
19054 significant bit of each byte first. The initial pattern
19055 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19056 the final result is inverted to ensure trailing zeros also affect the
19059 @emph{Note:} This is the same CRC polynomial as used in handling the
19060 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19061 However in the case of the Remote Serial Protocol, the CRC is computed
19062 @emph{most} significant bit first, and the result is not inverted, so
19063 trailing zeros have no effect on the CRC value.
19065 To complete the description, we show below the code of the function
19066 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19067 initially supplied @code{crc} argument means that an initial call to
19068 this function passing in zero will start computing the CRC using
19071 @kindex gnu_debuglink_crc32
19074 gnu_debuglink_crc32 (unsigned long crc,
19075 unsigned char *buf, size_t len)
19077 static const unsigned long crc32_table[256] =
19079 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19080 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19081 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19082 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19083 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19084 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19085 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19086 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19087 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19088 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19089 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19090 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19091 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19092 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19093 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19094 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19095 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19096 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19097 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19098 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19099 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19100 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19101 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19102 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19103 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19104 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19105 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19106 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19107 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19108 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19109 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19110 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19111 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19112 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19113 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19114 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19115 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19116 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19117 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19118 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19119 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19120 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19121 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19122 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19123 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19124 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19125 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19126 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19127 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19128 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19129 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19132 unsigned char *end;
19134 crc = ~crc & 0xffffffff;
19135 for (end = buf + len; buf < end; ++buf)
19136 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19137 return ~crc & 0xffffffff;
19142 This computation does not apply to the ``build ID'' method.
19144 @node MiniDebugInfo
19145 @section Debugging information in a special section
19146 @cindex separate debug sections
19147 @cindex @samp{.gnu_debugdata} section
19149 Some systems ship pre-built executables and libraries that have a
19150 special @samp{.gnu_debugdata} section. This feature is called
19151 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19152 is used to supply extra symbols for backtraces.
19154 The intent of this section is to provide extra minimal debugging
19155 information for use in simple backtraces. It is not intended to be a
19156 replacement for full separate debugging information (@pxref{Separate
19157 Debug Files}). The example below shows the intended use; however,
19158 @value{GDBN} does not currently put restrictions on what sort of
19159 debugging information might be included in the section.
19161 @value{GDBN} has support for this extension. If the section exists,
19162 then it is used provided that no other source of debugging information
19163 can be found, and that @value{GDBN} was configured with LZMA support.
19165 This section can be easily created using @command{objcopy} and other
19166 standard utilities:
19169 # Extract the dynamic symbols from the main binary, there is no need
19170 # to also have these in the normal symbol table.
19171 nm -D @var{binary} --format=posix --defined-only \
19172 | awk '@{ print $1 @}' | sort > dynsyms
19174 # Extract all the text (i.e. function) symbols from the debuginfo.
19175 # (Note that we actually also accept "D" symbols, for the benefit
19176 # of platforms like PowerPC64 that use function descriptors.)
19177 nm @var{binary} --format=posix --defined-only \
19178 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19181 # Keep all the function symbols not already in the dynamic symbol
19183 comm -13 dynsyms funcsyms > keep_symbols
19185 # Separate full debug info into debug binary.
19186 objcopy --only-keep-debug @var{binary} debug
19188 # Copy the full debuginfo, keeping only a minimal set of symbols and
19189 # removing some unnecessary sections.
19190 objcopy -S --remove-section .gdb_index --remove-section .comment \
19191 --keep-symbols=keep_symbols debug mini_debuginfo
19193 # Drop the full debug info from the original binary.
19194 strip --strip-all -R .comment @var{binary}
19196 # Inject the compressed data into the .gnu_debugdata section of the
19199 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19203 @section Index Files Speed Up @value{GDBN}
19204 @cindex index files
19205 @cindex @samp{.gdb_index} section
19207 When @value{GDBN} finds a symbol file, it scans the symbols in the
19208 file in order to construct an internal symbol table. This lets most
19209 @value{GDBN} operations work quickly---at the cost of a delay early
19210 on. For large programs, this delay can be quite lengthy, so
19211 @value{GDBN} provides a way to build an index, which speeds up
19214 The index is stored as a section in the symbol file. @value{GDBN} can
19215 write the index to a file, then you can put it into the symbol file
19216 using @command{objcopy}.
19218 To create an index file, use the @code{save gdb-index} command:
19221 @item save gdb-index @var{directory}
19222 @kindex save gdb-index
19223 Create an index file for each symbol file currently known by
19224 @value{GDBN}. Each file is named after its corresponding symbol file,
19225 with @samp{.gdb-index} appended, and is written into the given
19229 Once you have created an index file you can merge it into your symbol
19230 file, here named @file{symfile}, using @command{objcopy}:
19233 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19234 --set-section-flags .gdb_index=readonly symfile symfile
19237 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19238 sections that have been deprecated. Usually they are deprecated because
19239 they are missing a new feature or have performance issues.
19240 To tell @value{GDBN} to use a deprecated index section anyway
19241 specify @code{set use-deprecated-index-sections on}.
19242 The default is @code{off}.
19243 This can speed up startup, but may result in some functionality being lost.
19244 @xref{Index Section Format}.
19246 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19247 must be done before gdb reads the file. The following will not work:
19250 $ gdb -ex "set use-deprecated-index-sections on" <program>
19253 Instead you must do, for example,
19256 $ gdb -iex "set use-deprecated-index-sections on" <program>
19259 There are currently some limitation on indices. They only work when
19260 for DWARF debugging information, not stabs. And, they do not
19261 currently work for programs using Ada.
19263 @node Symbol Errors
19264 @section Errors Reading Symbol Files
19266 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19267 such as symbol types it does not recognize, or known bugs in compiler
19268 output. By default, @value{GDBN} does not notify you of such problems, since
19269 they are relatively common and primarily of interest to people
19270 debugging compilers. If you are interested in seeing information
19271 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19272 only one message about each such type of problem, no matter how many
19273 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19274 to see how many times the problems occur, with the @code{set
19275 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19278 The messages currently printed, and their meanings, include:
19281 @item inner block not inside outer block in @var{symbol}
19283 The symbol information shows where symbol scopes begin and end
19284 (such as at the start of a function or a block of statements). This
19285 error indicates that an inner scope block is not fully contained
19286 in its outer scope blocks.
19288 @value{GDBN} circumvents the problem by treating the inner block as if it had
19289 the same scope as the outer block. In the error message, @var{symbol}
19290 may be shown as ``@code{(don't know)}'' if the outer block is not a
19293 @item block at @var{address} out of order
19295 The symbol information for symbol scope blocks should occur in
19296 order of increasing addresses. This error indicates that it does not
19299 @value{GDBN} does not circumvent this problem, and has trouble
19300 locating symbols in the source file whose symbols it is reading. (You
19301 can often determine what source file is affected by specifying
19302 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19305 @item bad block start address patched
19307 The symbol information for a symbol scope block has a start address
19308 smaller than the address of the preceding source line. This is known
19309 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19311 @value{GDBN} circumvents the problem by treating the symbol scope block as
19312 starting on the previous source line.
19314 @item bad string table offset in symbol @var{n}
19317 Symbol number @var{n} contains a pointer into the string table which is
19318 larger than the size of the string table.
19320 @value{GDBN} circumvents the problem by considering the symbol to have the
19321 name @code{foo}, which may cause other problems if many symbols end up
19324 @item unknown symbol type @code{0x@var{nn}}
19326 The symbol information contains new data types that @value{GDBN} does
19327 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19328 uncomprehended information, in hexadecimal.
19330 @value{GDBN} circumvents the error by ignoring this symbol information.
19331 This usually allows you to debug your program, though certain symbols
19332 are not accessible. If you encounter such a problem and feel like
19333 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19334 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19335 and examine @code{*bufp} to see the symbol.
19337 @item stub type has NULL name
19339 @value{GDBN} could not find the full definition for a struct or class.
19341 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19342 The symbol information for a C@t{++} member function is missing some
19343 information that recent versions of the compiler should have output for
19346 @item info mismatch between compiler and debugger
19348 @value{GDBN} could not parse a type specification output by the compiler.
19353 @section GDB Data Files
19355 @cindex prefix for data files
19356 @value{GDBN} will sometimes read an auxiliary data file. These files
19357 are kept in a directory known as the @dfn{data directory}.
19359 You can set the data directory's name, and view the name @value{GDBN}
19360 is currently using.
19363 @kindex set data-directory
19364 @item set data-directory @var{directory}
19365 Set the directory which @value{GDBN} searches for auxiliary data files
19366 to @var{directory}.
19368 @kindex show data-directory
19369 @item show data-directory
19370 Show the directory @value{GDBN} searches for auxiliary data files.
19373 @cindex default data directory
19374 @cindex @samp{--with-gdb-datadir}
19375 You can set the default data directory by using the configure-time
19376 @samp{--with-gdb-datadir} option. If the data directory is inside
19377 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19378 @samp{--exec-prefix}), then the default data directory will be updated
19379 automatically if the installed @value{GDBN} is moved to a new
19382 The data directory may also be specified with the
19383 @code{--data-directory} command line option.
19384 @xref{Mode Options}.
19387 @chapter Specifying a Debugging Target
19389 @cindex debugging target
19390 A @dfn{target} is the execution environment occupied by your program.
19392 Often, @value{GDBN} runs in the same host environment as your program;
19393 in that case, the debugging target is specified as a side effect when
19394 you use the @code{file} or @code{core} commands. When you need more
19395 flexibility---for example, running @value{GDBN} on a physically separate
19396 host, or controlling a standalone system over a serial port or a
19397 realtime system over a TCP/IP connection---you can use the @code{target}
19398 command to specify one of the target types configured for @value{GDBN}
19399 (@pxref{Target Commands, ,Commands for Managing Targets}).
19401 @cindex target architecture
19402 It is possible to build @value{GDBN} for several different @dfn{target
19403 architectures}. When @value{GDBN} is built like that, you can choose
19404 one of the available architectures with the @kbd{set architecture}
19408 @kindex set architecture
19409 @kindex show architecture
19410 @item set architecture @var{arch}
19411 This command sets the current target architecture to @var{arch}. The
19412 value of @var{arch} can be @code{"auto"}, in addition to one of the
19413 supported architectures.
19415 @item show architecture
19416 Show the current target architecture.
19418 @item set processor
19420 @kindex set processor
19421 @kindex show processor
19422 These are alias commands for, respectively, @code{set architecture}
19423 and @code{show architecture}.
19427 * Active Targets:: Active targets
19428 * Target Commands:: Commands for managing targets
19429 * Byte Order:: Choosing target byte order
19432 @node Active Targets
19433 @section Active Targets
19435 @cindex stacking targets
19436 @cindex active targets
19437 @cindex multiple targets
19439 There are multiple classes of targets such as: processes, executable files or
19440 recording sessions. Core files belong to the process class, making core file
19441 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19442 on multiple active targets, one in each class. This allows you to (for
19443 example) start a process and inspect its activity, while still having access to
19444 the executable file after the process finishes. Or if you start process
19445 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19446 presented a virtual layer of the recording target, while the process target
19447 remains stopped at the chronologically last point of the process execution.
19449 Use the @code{core-file} and @code{exec-file} commands to select a new core
19450 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19451 specify as a target a process that is already running, use the @code{attach}
19452 command (@pxref{Attach, ,Debugging an Already-running Process}).
19454 @node Target Commands
19455 @section Commands for Managing Targets
19458 @item target @var{type} @var{parameters}
19459 Connects the @value{GDBN} host environment to a target machine or
19460 process. A target is typically a protocol for talking to debugging
19461 facilities. You use the argument @var{type} to specify the type or
19462 protocol of the target machine.
19464 Further @var{parameters} are interpreted by the target protocol, but
19465 typically include things like device names or host names to connect
19466 with, process numbers, and baud rates.
19468 The @code{target} command does not repeat if you press @key{RET} again
19469 after executing the command.
19471 @kindex help target
19473 Displays the names of all targets available. To display targets
19474 currently selected, use either @code{info target} or @code{info files}
19475 (@pxref{Files, ,Commands to Specify Files}).
19477 @item help target @var{name}
19478 Describe a particular target, including any parameters necessary to
19481 @kindex set gnutarget
19482 @item set gnutarget @var{args}
19483 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19484 knows whether it is reading an @dfn{executable},
19485 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19486 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19487 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19490 @emph{Warning:} To specify a file format with @code{set gnutarget},
19491 you must know the actual BFD name.
19495 @xref{Files, , Commands to Specify Files}.
19497 @kindex show gnutarget
19498 @item show gnutarget
19499 Use the @code{show gnutarget} command to display what file format
19500 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19501 @value{GDBN} will determine the file format for each file automatically,
19502 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19505 @cindex common targets
19506 Here are some common targets (available, or not, depending on the GDB
19511 @item target exec @var{program}
19512 @cindex executable file target
19513 An executable file. @samp{target exec @var{program}} is the same as
19514 @samp{exec-file @var{program}}.
19516 @item target core @var{filename}
19517 @cindex core dump file target
19518 A core dump file. @samp{target core @var{filename}} is the same as
19519 @samp{core-file @var{filename}}.
19521 @item target remote @var{medium}
19522 @cindex remote target
19523 A remote system connected to @value{GDBN} via a serial line or network
19524 connection. This command tells @value{GDBN} to use its own remote
19525 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19527 For example, if you have a board connected to @file{/dev/ttya} on the
19528 machine running @value{GDBN}, you could say:
19531 target remote /dev/ttya
19534 @code{target remote} supports the @code{load} command. This is only
19535 useful if you have some other way of getting the stub to the target
19536 system, and you can put it somewhere in memory where it won't get
19537 clobbered by the download.
19539 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19540 @cindex built-in simulator target
19541 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19549 works; however, you cannot assume that a specific memory map, device
19550 drivers, or even basic I/O is available, although some simulators do
19551 provide these. For info about any processor-specific simulator details,
19552 see the appropriate section in @ref{Embedded Processors, ,Embedded
19555 @item target native
19556 @cindex native target
19557 Setup for local/native process debugging. Useful to make the
19558 @code{run} command spawn native processes (likewise @code{attach},
19559 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19560 (@pxref{set auto-connect-native-target}).
19564 Different targets are available on different configurations of @value{GDBN};
19565 your configuration may have more or fewer targets.
19567 Many remote targets require you to download the executable's code once
19568 you've successfully established a connection. You may wish to control
19569 various aspects of this process.
19574 @kindex set hash@r{, for remote monitors}
19575 @cindex hash mark while downloading
19576 This command controls whether a hash mark @samp{#} is displayed while
19577 downloading a file to the remote monitor. If on, a hash mark is
19578 displayed after each S-record is successfully downloaded to the
19582 @kindex show hash@r{, for remote monitors}
19583 Show the current status of displaying the hash mark.
19585 @item set debug monitor
19586 @kindex set debug monitor
19587 @cindex display remote monitor communications
19588 Enable or disable display of communications messages between
19589 @value{GDBN} and the remote monitor.
19591 @item show debug monitor
19592 @kindex show debug monitor
19593 Show the current status of displaying communications between
19594 @value{GDBN} and the remote monitor.
19599 @kindex load @var{filename}
19600 @item load @var{filename}
19602 Depending on what remote debugging facilities are configured into
19603 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19604 is meant to make @var{filename} (an executable) available for debugging
19605 on the remote system---by downloading, or dynamic linking, for example.
19606 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19607 the @code{add-symbol-file} command.
19609 If your @value{GDBN} does not have a @code{load} command, attempting to
19610 execute it gets the error message ``@code{You can't do that when your
19611 target is @dots{}}''
19613 The file is loaded at whatever address is specified in the executable.
19614 For some object file formats, you can specify the load address when you
19615 link the program; for other formats, like a.out, the object file format
19616 specifies a fixed address.
19617 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19619 Depending on the remote side capabilities, @value{GDBN} may be able to
19620 load programs into flash memory.
19622 @code{load} does not repeat if you press @key{RET} again after using it.
19627 @kindex flash-erase
19629 @anchor{flash-erase}
19631 Erases all known flash memory regions on the target.
19636 @section Choosing Target Byte Order
19638 @cindex choosing target byte order
19639 @cindex target byte order
19641 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19642 offer the ability to run either big-endian or little-endian byte
19643 orders. Usually the executable or symbol will include a bit to
19644 designate the endian-ness, and you will not need to worry about
19645 which to use. However, you may still find it useful to adjust
19646 @value{GDBN}'s idea of processor endian-ness manually.
19650 @item set endian big
19651 Instruct @value{GDBN} to assume the target is big-endian.
19653 @item set endian little
19654 Instruct @value{GDBN} to assume the target is little-endian.
19656 @item set endian auto
19657 Instruct @value{GDBN} to use the byte order associated with the
19661 Display @value{GDBN}'s current idea of the target byte order.
19665 Note that these commands merely adjust interpretation of symbolic
19666 data on the host, and that they have absolutely no effect on the
19670 @node Remote Debugging
19671 @chapter Debugging Remote Programs
19672 @cindex remote debugging
19674 If you are trying to debug a program running on a machine that cannot run
19675 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19676 For example, you might use remote debugging on an operating system kernel,
19677 or on a small system which does not have a general purpose operating system
19678 powerful enough to run a full-featured debugger.
19680 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19681 to make this work with particular debugging targets. In addition,
19682 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19683 but not specific to any particular target system) which you can use if you
19684 write the remote stubs---the code that runs on the remote system to
19685 communicate with @value{GDBN}.
19687 Other remote targets may be available in your
19688 configuration of @value{GDBN}; use @code{help target} to list them.
19691 * Connecting:: Connecting to a remote target
19692 * File Transfer:: Sending files to a remote system
19693 * Server:: Using the gdbserver program
19694 * Remote Configuration:: Remote configuration
19695 * Remote Stub:: Implementing a remote stub
19699 @section Connecting to a Remote Target
19700 @cindex remote debugging, connecting
19701 @cindex @code{gdbserver}, connecting
19702 @cindex remote debugging, types of connections
19703 @cindex @code{gdbserver}, types of connections
19704 @cindex @code{gdbserver}, @code{target remote} mode
19705 @cindex @code{gdbserver}, @code{target extended-remote} mode
19707 This section describes how to connect to a remote target, including the
19708 types of connections and their differences, how to set up executable and
19709 symbol files on the host and target, and the commands used for
19710 connecting to and disconnecting from the remote target.
19712 @subsection Types of Remote Connections
19714 @value{GDBN} supports two types of remote connections, @code{target remote}
19715 mode and @code{target extended-remote} mode. Note that many remote targets
19716 support only @code{target remote} mode. There are several major
19717 differences between the two types of connections, enumerated here:
19721 @cindex remote debugging, detach and program exit
19722 @item Result of detach or program exit
19723 @strong{With target remote mode:} When the debugged program exits or you
19724 detach from it, @value{GDBN} disconnects from the target. When using
19725 @code{gdbserver}, @code{gdbserver} will exit.
19727 @strong{With target extended-remote mode:} When the debugged program exits or
19728 you detach from it, @value{GDBN} remains connected to the target, even
19729 though no program is running. You can rerun the program, attach to a
19730 running program, or use @code{monitor} commands specific to the target.
19732 When using @code{gdbserver} in this case, it does not exit unless it was
19733 invoked using the @option{--once} option. If the @option{--once} option
19734 was not used, you can ask @code{gdbserver} to exit using the
19735 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19737 @item Specifying the program to debug
19738 For both connection types you use the @code{file} command to specify the
19739 program on the host system. If you are using @code{gdbserver} there are
19740 some differences in how to specify the location of the program on the
19743 @strong{With target remote mode:} You must either specify the program to debug
19744 on the @code{gdbserver} command line or use the @option{--attach} option
19745 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19747 @cindex @option{--multi}, @code{gdbserver} option
19748 @strong{With target extended-remote mode:} You may specify the program to debug
19749 on the @code{gdbserver} command line, or you can load the program or attach
19750 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19752 @anchor{--multi Option in Types of Remote Connnections}
19753 You can start @code{gdbserver} without supplying an initial command to run
19754 or process ID to attach. To do this, use the @option{--multi} command line
19755 option. Then you can connect using @code{target extended-remote} and start
19756 the program you want to debug (see below for details on using the
19757 @code{run} command in this scenario). Note that the conditions under which
19758 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19759 (@code{target remote} or @code{target extended-remote}). The
19760 @option{--multi} option to @code{gdbserver} has no influence on that.
19762 @item The @code{run} command
19763 @strong{With target remote mode:} The @code{run} command is not
19764 supported. Once a connection has been established, you can use all
19765 the usual @value{GDBN} commands to examine and change data. The
19766 remote program is already running, so you can use commands like
19767 @kbd{step} and @kbd{continue}.
19769 @strong{With target extended-remote mode:} The @code{run} command is
19770 supported. The @code{run} command uses the value set by
19771 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19772 the program to run. Command line arguments are supported, except for
19773 wildcard expansion and I/O redirection (@pxref{Arguments}).
19775 If you specify the program to debug on the command line, then the
19776 @code{run} command is not required to start execution, and you can
19777 resume using commands like @kbd{step} and @kbd{continue} as with
19778 @code{target remote} mode.
19780 @anchor{Attaching in Types of Remote Connections}
19782 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19783 not supported. To attach to a running program using @code{gdbserver}, you
19784 must use the @option{--attach} option (@pxref{Running gdbserver}).
19786 @strong{With target extended-remote mode:} To attach to a running program,
19787 you may use the @code{attach} command after the connection has been
19788 established. If you are using @code{gdbserver}, you may also invoke
19789 @code{gdbserver} using the @option{--attach} option
19790 (@pxref{Running gdbserver}).
19794 @anchor{Host and target files}
19795 @subsection Host and Target Files
19796 @cindex remote debugging, symbol files
19797 @cindex symbol files, remote debugging
19799 @value{GDBN}, running on the host, needs access to symbol and debugging
19800 information for your program running on the target. This requires
19801 access to an unstripped copy of your program, and possibly any associated
19802 symbol files. Note that this section applies equally to both @code{target
19803 remote} mode and @code{target extended-remote} mode.
19805 Some remote targets (@pxref{qXfer executable filename read}, and
19806 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19807 the same connection used to communicate with @value{GDBN}. With such a
19808 target, if the remote program is unstripped, the only command you need is
19809 @code{target remote} (or @code{target extended-remote}).
19811 If the remote program is stripped, or the target does not support remote
19812 program file access, start up @value{GDBN} using the name of the local
19813 unstripped copy of your program as the first argument, or use the
19814 @code{file} command. Use @code{set sysroot} to specify the location (on
19815 the host) of target libraries (unless your @value{GDBN} was compiled with
19816 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19817 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19820 The symbol file and target libraries must exactly match the executable
19821 and libraries on the target, with one exception: the files on the host
19822 system should not be stripped, even if the files on the target system
19823 are. Mismatched or missing files will lead to confusing results
19824 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19825 files may also prevent @code{gdbserver} from debugging multi-threaded
19828 @subsection Remote Connection Commands
19829 @cindex remote connection commands
19830 @value{GDBN} can communicate with the target over a serial line, or
19831 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19832 each case, @value{GDBN} uses the same protocol for debugging your
19833 program; only the medium carrying the debugging packets varies. The
19834 @code{target remote} and @code{target extended-remote} commands
19835 establish a connection to the target. Both commands accept the same
19836 arguments, which indicate the medium to use:
19840 @item target remote @var{serial-device}
19841 @itemx target extended-remote @var{serial-device}
19842 @cindex serial line, @code{target remote}
19843 Use @var{serial-device} to communicate with the target. For example,
19844 to use a serial line connected to the device named @file{/dev/ttyb}:
19847 target remote /dev/ttyb
19850 If you're using a serial line, you may want to give @value{GDBN} the
19851 @samp{--baud} option, or use the @code{set serial baud} command
19852 (@pxref{Remote Configuration, set serial baud}) before the
19853 @code{target} command.
19855 @item target remote @code{@var{host}:@var{port}}
19856 @itemx target remote @code{tcp:@var{host}:@var{port}}
19857 @itemx target extended-remote @code{@var{host}:@var{port}}
19858 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19859 @cindex @acronym{TCP} port, @code{target remote}
19860 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19861 The @var{host} may be either a host name or a numeric @acronym{IP}
19862 address; @var{port} must be a decimal number. The @var{host} could be
19863 the target machine itself, if it is directly connected to the net, or
19864 it might be a terminal server which in turn has a serial line to the
19867 For example, to connect to port 2828 on a terminal server named
19871 target remote manyfarms:2828
19874 If your remote target is actually running on the same machine as your
19875 debugger session (e.g.@: a simulator for your target running on the
19876 same host), you can omit the hostname. For example, to connect to
19877 port 1234 on your local machine:
19880 target remote :1234
19884 Note that the colon is still required here.
19886 @item target remote @code{udp:@var{host}:@var{port}}
19887 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19888 @cindex @acronym{UDP} port, @code{target remote}
19889 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19890 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19893 target remote udp:manyfarms:2828
19896 When using a @acronym{UDP} connection for remote debugging, you should
19897 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19898 can silently drop packets on busy or unreliable networks, which will
19899 cause havoc with your debugging session.
19901 @item target remote | @var{command}
19902 @itemx target extended-remote | @var{command}
19903 @cindex pipe, @code{target remote} to
19904 Run @var{command} in the background and communicate with it using a
19905 pipe. The @var{command} is a shell command, to be parsed and expanded
19906 by the system's command shell, @code{/bin/sh}; it should expect remote
19907 protocol packets on its standard input, and send replies on its
19908 standard output. You could use this to run a stand-alone simulator
19909 that speaks the remote debugging protocol, to make net connections
19910 using programs like @code{ssh}, or for other similar tricks.
19912 If @var{command} closes its standard output (perhaps by exiting),
19913 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19914 program has already exited, this will have no effect.)
19918 @cindex interrupting remote programs
19919 @cindex remote programs, interrupting
19920 Whenever @value{GDBN} is waiting for the remote program, if you type the
19921 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19922 program. This may or may not succeed, depending in part on the hardware
19923 and the serial drivers the remote system uses. If you type the
19924 interrupt character once again, @value{GDBN} displays this prompt:
19927 Interrupted while waiting for the program.
19928 Give up (and stop debugging it)? (y or n)
19931 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19932 the remote debugging session. (If you decide you want to try again later,
19933 you can use @kbd{target remote} again to connect once more.) If you type
19934 @kbd{n}, @value{GDBN} goes back to waiting.
19936 In @code{target extended-remote} mode, typing @kbd{n} will leave
19937 @value{GDBN} connected to the target.
19940 @kindex detach (remote)
19942 When you have finished debugging the remote program, you can use the
19943 @code{detach} command to release it from @value{GDBN} control.
19944 Detaching from the target normally resumes its execution, but the results
19945 will depend on your particular remote stub. After the @code{detach}
19946 command in @code{target remote} mode, @value{GDBN} is free to connect to
19947 another target. In @code{target extended-remote} mode, @value{GDBN} is
19948 still connected to the target.
19952 The @code{disconnect} command closes the connection to the target, and
19953 the target is generally not resumed. It will wait for @value{GDBN}
19954 (this instance or another one) to connect and continue debugging. After
19955 the @code{disconnect} command, @value{GDBN} is again free to connect to
19958 @cindex send command to remote monitor
19959 @cindex extend @value{GDBN} for remote targets
19960 @cindex add new commands for external monitor
19962 @item monitor @var{cmd}
19963 This command allows you to send arbitrary commands directly to the
19964 remote monitor. Since @value{GDBN} doesn't care about the commands it
19965 sends like this, this command is the way to extend @value{GDBN}---you
19966 can add new commands that only the external monitor will understand
19970 @node File Transfer
19971 @section Sending files to a remote system
19972 @cindex remote target, file transfer
19973 @cindex file transfer
19974 @cindex sending files to remote systems
19976 Some remote targets offer the ability to transfer files over the same
19977 connection used to communicate with @value{GDBN}. This is convenient
19978 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19979 running @code{gdbserver} over a network interface. For other targets,
19980 e.g.@: embedded devices with only a single serial port, this may be
19981 the only way to upload or download files.
19983 Not all remote targets support these commands.
19987 @item remote put @var{hostfile} @var{targetfile}
19988 Copy file @var{hostfile} from the host system (the machine running
19989 @value{GDBN}) to @var{targetfile} on the target system.
19992 @item remote get @var{targetfile} @var{hostfile}
19993 Copy file @var{targetfile} from the target system to @var{hostfile}
19994 on the host system.
19996 @kindex remote delete
19997 @item remote delete @var{targetfile}
19998 Delete @var{targetfile} from the target system.
20003 @section Using the @code{gdbserver} Program
20006 @cindex remote connection without stubs
20007 @code{gdbserver} is a control program for Unix-like systems, which
20008 allows you to connect your program with a remote @value{GDBN} via
20009 @code{target remote} or @code{target extended-remote}---but without
20010 linking in the usual debugging stub.
20012 @code{gdbserver} is not a complete replacement for the debugging stubs,
20013 because it requires essentially the same operating-system facilities
20014 that @value{GDBN} itself does. In fact, a system that can run
20015 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20016 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20017 because it is a much smaller program than @value{GDBN} itself. It is
20018 also easier to port than all of @value{GDBN}, so you may be able to get
20019 started more quickly on a new system by using @code{gdbserver}.
20020 Finally, if you develop code for real-time systems, you may find that
20021 the tradeoffs involved in real-time operation make it more convenient to
20022 do as much development work as possible on another system, for example
20023 by cross-compiling. You can use @code{gdbserver} to make a similar
20024 choice for debugging.
20026 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20027 or a TCP connection, using the standard @value{GDBN} remote serial
20031 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20032 Do not run @code{gdbserver} connected to any public network; a
20033 @value{GDBN} connection to @code{gdbserver} provides access to the
20034 target system with the same privileges as the user running
20038 @anchor{Running gdbserver}
20039 @subsection Running @code{gdbserver}
20040 @cindex arguments, to @code{gdbserver}
20041 @cindex @code{gdbserver}, command-line arguments
20043 Run @code{gdbserver} on the target system. You need a copy of the
20044 program you want to debug, including any libraries it requires.
20045 @code{gdbserver} does not need your program's symbol table, so you can
20046 strip the program if necessary to save space. @value{GDBN} on the host
20047 system does all the symbol handling.
20049 To use the server, you must tell it how to communicate with @value{GDBN};
20050 the name of your program; and the arguments for your program. The usual
20054 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20057 @var{comm} is either a device name (to use a serial line), or a TCP
20058 hostname and portnumber, or @code{-} or @code{stdio} to use
20059 stdin/stdout of @code{gdbserver}.
20060 For example, to debug Emacs with the argument
20061 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20065 target> gdbserver /dev/com1 emacs foo.txt
20068 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20071 To use a TCP connection instead of a serial line:
20074 target> gdbserver host:2345 emacs foo.txt
20077 The only difference from the previous example is the first argument,
20078 specifying that you are communicating with the host @value{GDBN} via
20079 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20080 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20081 (Currently, the @samp{host} part is ignored.) You can choose any number
20082 you want for the port number as long as it does not conflict with any
20083 TCP ports already in use on the target system (for example, @code{23} is
20084 reserved for @code{telnet}).@footnote{If you choose a port number that
20085 conflicts with another service, @code{gdbserver} prints an error message
20086 and exits.} You must use the same port number with the host @value{GDBN}
20087 @code{target remote} command.
20089 The @code{stdio} connection is useful when starting @code{gdbserver}
20093 (gdb) target remote | ssh -T hostname gdbserver - hello
20096 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20097 and we don't want escape-character handling. Ssh does this by default when
20098 a command is provided, the flag is provided to make it explicit.
20099 You could elide it if you want to.
20101 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20102 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20103 display through a pipe connected to gdbserver.
20104 Both @code{stdout} and @code{stderr} use the same pipe.
20106 @anchor{Attaching to a program}
20107 @subsubsection Attaching to a Running Program
20108 @cindex attach to a program, @code{gdbserver}
20109 @cindex @option{--attach}, @code{gdbserver} option
20111 On some targets, @code{gdbserver} can also attach to running programs.
20112 This is accomplished via the @code{--attach} argument. The syntax is:
20115 target> gdbserver --attach @var{comm} @var{pid}
20118 @var{pid} is the process ID of a currently running process. It isn't
20119 necessary to point @code{gdbserver} at a binary for the running process.
20121 In @code{target extended-remote} mode, you can also attach using the
20122 @value{GDBN} attach command
20123 (@pxref{Attaching in Types of Remote Connections}).
20126 You can debug processes by name instead of process ID if your target has the
20127 @code{pidof} utility:
20130 target> gdbserver --attach @var{comm} `pidof @var{program}`
20133 In case more than one copy of @var{program} is running, or @var{program}
20134 has multiple threads, most versions of @code{pidof} support the
20135 @code{-s} option to only return the first process ID.
20137 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20139 This section applies only when @code{gdbserver} is run to listen on a TCP
20142 @code{gdbserver} normally terminates after all of its debugged processes have
20143 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20144 extended-remote}, @code{gdbserver} stays running even with no processes left.
20145 @value{GDBN} normally terminates the spawned debugged process on its exit,
20146 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20147 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20148 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20149 stays running even in the @kbd{target remote} mode.
20151 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20152 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20153 completeness, at most one @value{GDBN} can be connected at a time.
20155 @cindex @option{--once}, @code{gdbserver} option
20156 By default, @code{gdbserver} keeps the listening TCP port open, so that
20157 subsequent connections are possible. However, if you start @code{gdbserver}
20158 with the @option{--once} option, it will stop listening for any further
20159 connection attempts after connecting to the first @value{GDBN} session. This
20160 means no further connections to @code{gdbserver} will be possible after the
20161 first one. It also means @code{gdbserver} will terminate after the first
20162 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20163 connections and even in the @kbd{target extended-remote} mode. The
20164 @option{--once} option allows reusing the same port number for connecting to
20165 multiple instances of @code{gdbserver} running on the same host, since each
20166 instance closes its port after the first connection.
20168 @anchor{Other Command-Line Arguments for gdbserver}
20169 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20171 You can use the @option{--multi} option to start @code{gdbserver} without
20172 specifying a program to debug or a process to attach to. Then you can
20173 attach in @code{target extended-remote} mode and run or attach to a
20174 program. For more information,
20175 @pxref{--multi Option in Types of Remote Connnections}.
20177 @cindex @option{--debug}, @code{gdbserver} option
20178 The @option{--debug} option tells @code{gdbserver} to display extra
20179 status information about the debugging process.
20180 @cindex @option{--remote-debug}, @code{gdbserver} option
20181 The @option{--remote-debug} option tells @code{gdbserver} to display
20182 remote protocol debug output. These options are intended for
20183 @code{gdbserver} development and for bug reports to the developers.
20185 @cindex @option{--debug-format}, @code{gdbserver} option
20186 The @option{--debug-format=option1[,option2,...]} option tells
20187 @code{gdbserver} to include additional information in each output.
20188 Possible options are:
20192 Turn off all extra information in debugging output.
20194 Turn on all extra information in debugging output.
20196 Include a timestamp in each line of debugging output.
20199 Options are processed in order. Thus, for example, if @option{none}
20200 appears last then no additional information is added to debugging output.
20202 @cindex @option{--wrapper}, @code{gdbserver} option
20203 The @option{--wrapper} option specifies a wrapper to launch programs
20204 for debugging. The option should be followed by the name of the
20205 wrapper, then any command-line arguments to pass to the wrapper, then
20206 @kbd{--} indicating the end of the wrapper arguments.
20208 @code{gdbserver} runs the specified wrapper program with a combined
20209 command line including the wrapper arguments, then the name of the
20210 program to debug, then any arguments to the program. The wrapper
20211 runs until it executes your program, and then @value{GDBN} gains control.
20213 You can use any program that eventually calls @code{execve} with
20214 its arguments as a wrapper. Several standard Unix utilities do
20215 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20216 with @code{exec "$@@"} will also work.
20218 For example, you can use @code{env} to pass an environment variable to
20219 the debugged program, without setting the variable in @code{gdbserver}'s
20223 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20226 @subsection Connecting to @code{gdbserver}
20228 The basic procedure for connecting to the remote target is:
20232 Run @value{GDBN} on the host system.
20235 Make sure you have the necessary symbol files
20236 (@pxref{Host and target files}).
20237 Load symbols for your application using the @code{file} command before you
20238 connect. Use @code{set sysroot} to locate target libraries (unless your
20239 @value{GDBN} was compiled with the correct sysroot using
20240 @code{--with-sysroot}).
20243 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20244 For TCP connections, you must start up @code{gdbserver} prior to using
20245 the @code{target} command. Otherwise you may get an error whose
20246 text depends on the host system, but which usually looks something like
20247 @samp{Connection refused}. Don't use the @code{load}
20248 command in @value{GDBN} when using @code{target remote} mode, since the
20249 program is already on the target.
20253 @anchor{Monitor Commands for gdbserver}
20254 @subsection Monitor Commands for @code{gdbserver}
20255 @cindex monitor commands, for @code{gdbserver}
20257 During a @value{GDBN} session using @code{gdbserver}, you can use the
20258 @code{monitor} command to send special requests to @code{gdbserver}.
20259 Here are the available commands.
20263 List the available monitor commands.
20265 @item monitor set debug 0
20266 @itemx monitor set debug 1
20267 Disable or enable general debugging messages.
20269 @item monitor set remote-debug 0
20270 @itemx monitor set remote-debug 1
20271 Disable or enable specific debugging messages associated with the remote
20272 protocol (@pxref{Remote Protocol}).
20274 @item monitor set debug-format option1@r{[},option2,...@r{]}
20275 Specify additional text to add to debugging messages.
20276 Possible options are:
20280 Turn off all extra information in debugging output.
20282 Turn on all extra information in debugging output.
20284 Include a timestamp in each line of debugging output.
20287 Options are processed in order. Thus, for example, if @option{none}
20288 appears last then no additional information is added to debugging output.
20290 @item monitor set libthread-db-search-path [PATH]
20291 @cindex gdbserver, search path for @code{libthread_db}
20292 When this command is issued, @var{path} is a colon-separated list of
20293 directories to search for @code{libthread_db} (@pxref{Threads,,set
20294 libthread-db-search-path}). If you omit @var{path},
20295 @samp{libthread-db-search-path} will be reset to its default value.
20297 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20298 not supported in @code{gdbserver}.
20301 Tell gdbserver to exit immediately. This command should be followed by
20302 @code{disconnect} to close the debugging session. @code{gdbserver} will
20303 detach from any attached processes and kill any processes it created.
20304 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20305 of a multi-process mode debug session.
20309 @subsection Tracepoints support in @code{gdbserver}
20310 @cindex tracepoints support in @code{gdbserver}
20312 On some targets, @code{gdbserver} supports tracepoints, fast
20313 tracepoints and static tracepoints.
20315 For fast or static tracepoints to work, a special library called the
20316 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20317 This library is built and distributed as an integral part of
20318 @code{gdbserver}. In addition, support for static tracepoints
20319 requires building the in-process agent library with static tracepoints
20320 support. At present, the UST (LTTng Userspace Tracer,
20321 @url{http://lttng.org/ust}) tracing engine is supported. This support
20322 is automatically available if UST development headers are found in the
20323 standard include path when @code{gdbserver} is built, or if
20324 @code{gdbserver} was explicitly configured using @option{--with-ust}
20325 to point at such headers. You can explicitly disable the support
20326 using @option{--with-ust=no}.
20328 There are several ways to load the in-process agent in your program:
20331 @item Specifying it as dependency at link time
20333 You can link your program dynamically with the in-process agent
20334 library. On most systems, this is accomplished by adding
20335 @code{-linproctrace} to the link command.
20337 @item Using the system's preloading mechanisms
20339 You can force loading the in-process agent at startup time by using
20340 your system's support for preloading shared libraries. Many Unixes
20341 support the concept of preloading user defined libraries. In most
20342 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20343 in the environment. See also the description of @code{gdbserver}'s
20344 @option{--wrapper} command line option.
20346 @item Using @value{GDBN} to force loading the agent at run time
20348 On some systems, you can force the inferior to load a shared library,
20349 by calling a dynamic loader function in the inferior that takes care
20350 of dynamically looking up and loading a shared library. On most Unix
20351 systems, the function is @code{dlopen}. You'll use the @code{call}
20352 command for that. For example:
20355 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20358 Note that on most Unix systems, for the @code{dlopen} function to be
20359 available, the program needs to be linked with @code{-ldl}.
20362 On systems that have a userspace dynamic loader, like most Unix
20363 systems, when you connect to @code{gdbserver} using @code{target
20364 remote}, you'll find that the program is stopped at the dynamic
20365 loader's entry point, and no shared library has been loaded in the
20366 program's address space yet, including the in-process agent. In that
20367 case, before being able to use any of the fast or static tracepoints
20368 features, you need to let the loader run and load the shared
20369 libraries. The simplest way to do that is to run the program to the
20370 main procedure. E.g., if debugging a C or C@t{++} program, start
20371 @code{gdbserver} like so:
20374 $ gdbserver :9999 myprogram
20377 Start GDB and connect to @code{gdbserver} like so, and run to main:
20381 (@value{GDBP}) target remote myhost:9999
20382 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20383 (@value{GDBP}) b main
20384 (@value{GDBP}) continue
20387 The in-process tracing agent library should now be loaded into the
20388 process; you can confirm it with the @code{info sharedlibrary}
20389 command, which will list @file{libinproctrace.so} as loaded in the
20390 process. You are now ready to install fast tracepoints, list static
20391 tracepoint markers, probe static tracepoints markers, and start
20394 @node Remote Configuration
20395 @section Remote Configuration
20398 @kindex show remote
20399 This section documents the configuration options available when
20400 debugging remote programs. For the options related to the File I/O
20401 extensions of the remote protocol, see @ref{system,
20402 system-call-allowed}.
20405 @item set remoteaddresssize @var{bits}
20406 @cindex address size for remote targets
20407 @cindex bits in remote address
20408 Set the maximum size of address in a memory packet to the specified
20409 number of bits. @value{GDBN} will mask off the address bits above
20410 that number, when it passes addresses to the remote target. The
20411 default value is the number of bits in the target's address.
20413 @item show remoteaddresssize
20414 Show the current value of remote address size in bits.
20416 @item set serial baud @var{n}
20417 @cindex baud rate for remote targets
20418 Set the baud rate for the remote serial I/O to @var{n} baud. The
20419 value is used to set the speed of the serial port used for debugging
20422 @item show serial baud
20423 Show the current speed of the remote connection.
20425 @item set serial parity @var{parity}
20426 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20427 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20429 @item show serial parity
20430 Show the current parity of the serial port.
20432 @item set remotebreak
20433 @cindex interrupt remote programs
20434 @cindex BREAK signal instead of Ctrl-C
20435 @anchor{set remotebreak}
20436 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20437 when you type @kbd{Ctrl-c} to interrupt the program running
20438 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20439 character instead. The default is off, since most remote systems
20440 expect to see @samp{Ctrl-C} as the interrupt signal.
20442 @item show remotebreak
20443 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20444 interrupt the remote program.
20446 @item set remoteflow on
20447 @itemx set remoteflow off
20448 @kindex set remoteflow
20449 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20450 on the serial port used to communicate to the remote target.
20452 @item show remoteflow
20453 @kindex show remoteflow
20454 Show the current setting of hardware flow control.
20456 @item set remotelogbase @var{base}
20457 Set the base (a.k.a.@: radix) of logging serial protocol
20458 communications to @var{base}. Supported values of @var{base} are:
20459 @code{ascii}, @code{octal}, and @code{hex}. The default is
20462 @item show remotelogbase
20463 Show the current setting of the radix for logging remote serial
20466 @item set remotelogfile @var{file}
20467 @cindex record serial communications on file
20468 Record remote serial communications on the named @var{file}. The
20469 default is not to record at all.
20471 @item show remotelogfile.
20472 Show the current setting of the file name on which to record the
20473 serial communications.
20475 @item set remotetimeout @var{num}
20476 @cindex timeout for serial communications
20477 @cindex remote timeout
20478 Set the timeout limit to wait for the remote target to respond to
20479 @var{num} seconds. The default is 2 seconds.
20481 @item show remotetimeout
20482 Show the current number of seconds to wait for the remote target
20485 @cindex limit hardware breakpoints and watchpoints
20486 @cindex remote target, limit break- and watchpoints
20487 @anchor{set remote hardware-watchpoint-limit}
20488 @anchor{set remote hardware-breakpoint-limit}
20489 @item set remote hardware-watchpoint-limit @var{limit}
20490 @itemx set remote hardware-breakpoint-limit @var{limit}
20491 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20492 watchpoints. A limit of -1, the default, is treated as unlimited.
20494 @cindex limit hardware watchpoints length
20495 @cindex remote target, limit watchpoints length
20496 @anchor{set remote hardware-watchpoint-length-limit}
20497 @item set remote hardware-watchpoint-length-limit @var{limit}
20498 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20499 a remote hardware watchpoint. A limit of -1, the default, is treated
20502 @item show remote hardware-watchpoint-length-limit
20503 Show the current limit (in bytes) of the maximum length of
20504 a remote hardware watchpoint.
20506 @item set remote exec-file @var{filename}
20507 @itemx show remote exec-file
20508 @anchor{set remote exec-file}
20509 @cindex executable file, for remote target
20510 Select the file used for @code{run} with @code{target
20511 extended-remote}. This should be set to a filename valid on the
20512 target system. If it is not set, the target will use a default
20513 filename (e.g.@: the last program run).
20515 @item set remote interrupt-sequence
20516 @cindex interrupt remote programs
20517 @cindex select Ctrl-C, BREAK or BREAK-g
20518 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20519 @samp{BREAK-g} as the
20520 sequence to the remote target in order to interrupt the execution.
20521 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20522 is high level of serial line for some certain time.
20523 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20524 It is @code{BREAK} signal followed by character @code{g}.
20526 @item show interrupt-sequence
20527 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20528 is sent by @value{GDBN} to interrupt the remote program.
20529 @code{BREAK-g} is BREAK signal followed by @code{g} and
20530 also known as Magic SysRq g.
20532 @item set remote interrupt-on-connect
20533 @cindex send interrupt-sequence on start
20534 Specify whether interrupt-sequence is sent to remote target when
20535 @value{GDBN} connects to it. This is mostly needed when you debug
20536 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20537 which is known as Magic SysRq g in order to connect @value{GDBN}.
20539 @item show interrupt-on-connect
20540 Show whether interrupt-sequence is sent
20541 to remote target when @value{GDBN} connects to it.
20545 @item set tcp auto-retry on
20546 @cindex auto-retry, for remote TCP target
20547 Enable auto-retry for remote TCP connections. This is useful if the remote
20548 debugging agent is launched in parallel with @value{GDBN}; there is a race
20549 condition because the agent may not become ready to accept the connection
20550 before @value{GDBN} attempts to connect. When auto-retry is
20551 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20552 to establish the connection using the timeout specified by
20553 @code{set tcp connect-timeout}.
20555 @item set tcp auto-retry off
20556 Do not auto-retry failed TCP connections.
20558 @item show tcp auto-retry
20559 Show the current auto-retry setting.
20561 @item set tcp connect-timeout @var{seconds}
20562 @itemx set tcp connect-timeout unlimited
20563 @cindex connection timeout, for remote TCP target
20564 @cindex timeout, for remote target connection
20565 Set the timeout for establishing a TCP connection to the remote target to
20566 @var{seconds}. The timeout affects both polling to retry failed connections
20567 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20568 that are merely slow to complete, and represents an approximate cumulative
20569 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20570 @value{GDBN} will keep attempting to establish a connection forever,
20571 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20573 @item show tcp connect-timeout
20574 Show the current connection timeout setting.
20577 @cindex remote packets, enabling and disabling
20578 The @value{GDBN} remote protocol autodetects the packets supported by
20579 your debugging stub. If you need to override the autodetection, you
20580 can use these commands to enable or disable individual packets. Each
20581 packet can be set to @samp{on} (the remote target supports this
20582 packet), @samp{off} (the remote target does not support this packet),
20583 or @samp{auto} (detect remote target support for this packet). They
20584 all default to @samp{auto}. For more information about each packet,
20585 see @ref{Remote Protocol}.
20587 During normal use, you should not have to use any of these commands.
20588 If you do, that may be a bug in your remote debugging stub, or a bug
20589 in @value{GDBN}. You may want to report the problem to the
20590 @value{GDBN} developers.
20592 For each packet @var{name}, the command to enable or disable the
20593 packet is @code{set remote @var{name}-packet}. The available settings
20596 @multitable @columnfractions 0.28 0.32 0.25
20599 @tab Related Features
20601 @item @code{fetch-register}
20603 @tab @code{info registers}
20605 @item @code{set-register}
20609 @item @code{binary-download}
20611 @tab @code{load}, @code{set}
20613 @item @code{read-aux-vector}
20614 @tab @code{qXfer:auxv:read}
20615 @tab @code{info auxv}
20617 @item @code{symbol-lookup}
20618 @tab @code{qSymbol}
20619 @tab Detecting multiple threads
20621 @item @code{attach}
20622 @tab @code{vAttach}
20625 @item @code{verbose-resume}
20627 @tab Stepping or resuming multiple threads
20633 @item @code{software-breakpoint}
20637 @item @code{hardware-breakpoint}
20641 @item @code{write-watchpoint}
20645 @item @code{read-watchpoint}
20649 @item @code{access-watchpoint}
20653 @item @code{pid-to-exec-file}
20654 @tab @code{qXfer:exec-file:read}
20655 @tab @code{attach}, @code{run}
20657 @item @code{target-features}
20658 @tab @code{qXfer:features:read}
20659 @tab @code{set architecture}
20661 @item @code{library-info}
20662 @tab @code{qXfer:libraries:read}
20663 @tab @code{info sharedlibrary}
20665 @item @code{memory-map}
20666 @tab @code{qXfer:memory-map:read}
20667 @tab @code{info mem}
20669 @item @code{read-sdata-object}
20670 @tab @code{qXfer:sdata:read}
20671 @tab @code{print $_sdata}
20673 @item @code{read-spu-object}
20674 @tab @code{qXfer:spu:read}
20675 @tab @code{info spu}
20677 @item @code{write-spu-object}
20678 @tab @code{qXfer:spu:write}
20679 @tab @code{info spu}
20681 @item @code{read-siginfo-object}
20682 @tab @code{qXfer:siginfo:read}
20683 @tab @code{print $_siginfo}
20685 @item @code{write-siginfo-object}
20686 @tab @code{qXfer:siginfo:write}
20687 @tab @code{set $_siginfo}
20689 @item @code{threads}
20690 @tab @code{qXfer:threads:read}
20691 @tab @code{info threads}
20693 @item @code{get-thread-local-@*storage-address}
20694 @tab @code{qGetTLSAddr}
20695 @tab Displaying @code{__thread} variables
20697 @item @code{get-thread-information-block-address}
20698 @tab @code{qGetTIBAddr}
20699 @tab Display MS-Windows Thread Information Block.
20701 @item @code{search-memory}
20702 @tab @code{qSearch:memory}
20705 @item @code{supported-packets}
20706 @tab @code{qSupported}
20707 @tab Remote communications parameters
20709 @item @code{catch-syscalls}
20710 @tab @code{QCatchSyscalls}
20711 @tab @code{catch syscall}
20713 @item @code{pass-signals}
20714 @tab @code{QPassSignals}
20715 @tab @code{handle @var{signal}}
20717 @item @code{program-signals}
20718 @tab @code{QProgramSignals}
20719 @tab @code{handle @var{signal}}
20721 @item @code{hostio-close-packet}
20722 @tab @code{vFile:close}
20723 @tab @code{remote get}, @code{remote put}
20725 @item @code{hostio-open-packet}
20726 @tab @code{vFile:open}
20727 @tab @code{remote get}, @code{remote put}
20729 @item @code{hostio-pread-packet}
20730 @tab @code{vFile:pread}
20731 @tab @code{remote get}, @code{remote put}
20733 @item @code{hostio-pwrite-packet}
20734 @tab @code{vFile:pwrite}
20735 @tab @code{remote get}, @code{remote put}
20737 @item @code{hostio-unlink-packet}
20738 @tab @code{vFile:unlink}
20739 @tab @code{remote delete}
20741 @item @code{hostio-readlink-packet}
20742 @tab @code{vFile:readlink}
20745 @item @code{hostio-fstat-packet}
20746 @tab @code{vFile:fstat}
20749 @item @code{hostio-setfs-packet}
20750 @tab @code{vFile:setfs}
20753 @item @code{noack-packet}
20754 @tab @code{QStartNoAckMode}
20755 @tab Packet acknowledgment
20757 @item @code{osdata}
20758 @tab @code{qXfer:osdata:read}
20759 @tab @code{info os}
20761 @item @code{query-attached}
20762 @tab @code{qAttached}
20763 @tab Querying remote process attach state.
20765 @item @code{trace-buffer-size}
20766 @tab @code{QTBuffer:size}
20767 @tab @code{set trace-buffer-size}
20769 @item @code{trace-status}
20770 @tab @code{qTStatus}
20771 @tab @code{tstatus}
20773 @item @code{traceframe-info}
20774 @tab @code{qXfer:traceframe-info:read}
20775 @tab Traceframe info
20777 @item @code{install-in-trace}
20778 @tab @code{InstallInTrace}
20779 @tab Install tracepoint in tracing
20781 @item @code{disable-randomization}
20782 @tab @code{QDisableRandomization}
20783 @tab @code{set disable-randomization}
20785 @item @code{conditional-breakpoints-packet}
20786 @tab @code{Z0 and Z1}
20787 @tab @code{Support for target-side breakpoint condition evaluation}
20789 @item @code{multiprocess-extensions}
20790 @tab @code{multiprocess extensions}
20791 @tab Debug multiple processes and remote process PID awareness
20793 @item @code{swbreak-feature}
20794 @tab @code{swbreak stop reason}
20797 @item @code{hwbreak-feature}
20798 @tab @code{hwbreak stop reason}
20801 @item @code{fork-event-feature}
20802 @tab @code{fork stop reason}
20805 @item @code{vfork-event-feature}
20806 @tab @code{vfork stop reason}
20809 @item @code{exec-event-feature}
20810 @tab @code{exec stop reason}
20813 @item @code{thread-events}
20814 @tab @code{QThreadEvents}
20815 @tab Tracking thread lifetime.
20817 @item @code{no-resumed-stop-reply}
20818 @tab @code{no resumed thread left stop reply}
20819 @tab Tracking thread lifetime.
20824 @section Implementing a Remote Stub
20826 @cindex debugging stub, example
20827 @cindex remote stub, example
20828 @cindex stub example, remote debugging
20829 The stub files provided with @value{GDBN} implement the target side of the
20830 communication protocol, and the @value{GDBN} side is implemented in the
20831 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20832 these subroutines to communicate, and ignore the details. (If you're
20833 implementing your own stub file, you can still ignore the details: start
20834 with one of the existing stub files. @file{sparc-stub.c} is the best
20835 organized, and therefore the easiest to read.)
20837 @cindex remote serial debugging, overview
20838 To debug a program running on another machine (the debugging
20839 @dfn{target} machine), you must first arrange for all the usual
20840 prerequisites for the program to run by itself. For example, for a C
20845 A startup routine to set up the C runtime environment; these usually
20846 have a name like @file{crt0}. The startup routine may be supplied by
20847 your hardware supplier, or you may have to write your own.
20850 A C subroutine library to support your program's
20851 subroutine calls, notably managing input and output.
20854 A way of getting your program to the other machine---for example, a
20855 download program. These are often supplied by the hardware
20856 manufacturer, but you may have to write your own from hardware
20860 The next step is to arrange for your program to use a serial port to
20861 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20862 machine). In general terms, the scheme looks like this:
20866 @value{GDBN} already understands how to use this protocol; when everything
20867 else is set up, you can simply use the @samp{target remote} command
20868 (@pxref{Targets,,Specifying a Debugging Target}).
20870 @item On the target,
20871 you must link with your program a few special-purpose subroutines that
20872 implement the @value{GDBN} remote serial protocol. The file containing these
20873 subroutines is called a @dfn{debugging stub}.
20875 On certain remote targets, you can use an auxiliary program
20876 @code{gdbserver} instead of linking a stub into your program.
20877 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20880 The debugging stub is specific to the architecture of the remote
20881 machine; for example, use @file{sparc-stub.c} to debug programs on
20884 @cindex remote serial stub list
20885 These working remote stubs are distributed with @value{GDBN}:
20890 @cindex @file{i386-stub.c}
20893 For Intel 386 and compatible architectures.
20896 @cindex @file{m68k-stub.c}
20897 @cindex Motorola 680x0
20899 For Motorola 680x0 architectures.
20902 @cindex @file{sh-stub.c}
20905 For Renesas SH architectures.
20908 @cindex @file{sparc-stub.c}
20910 For @sc{sparc} architectures.
20912 @item sparcl-stub.c
20913 @cindex @file{sparcl-stub.c}
20916 For Fujitsu @sc{sparclite} architectures.
20920 The @file{README} file in the @value{GDBN} distribution may list other
20921 recently added stubs.
20924 * Stub Contents:: What the stub can do for you
20925 * Bootstrapping:: What you must do for the stub
20926 * Debug Session:: Putting it all together
20929 @node Stub Contents
20930 @subsection What the Stub Can Do for You
20932 @cindex remote serial stub
20933 The debugging stub for your architecture supplies these three
20937 @item set_debug_traps
20938 @findex set_debug_traps
20939 @cindex remote serial stub, initialization
20940 This routine arranges for @code{handle_exception} to run when your
20941 program stops. You must call this subroutine explicitly in your
20942 program's startup code.
20944 @item handle_exception
20945 @findex handle_exception
20946 @cindex remote serial stub, main routine
20947 This is the central workhorse, but your program never calls it
20948 explicitly---the setup code arranges for @code{handle_exception} to
20949 run when a trap is triggered.
20951 @code{handle_exception} takes control when your program stops during
20952 execution (for example, on a breakpoint), and mediates communications
20953 with @value{GDBN} on the host machine. This is where the communications
20954 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20955 representative on the target machine. It begins by sending summary
20956 information on the state of your program, then continues to execute,
20957 retrieving and transmitting any information @value{GDBN} needs, until you
20958 execute a @value{GDBN} command that makes your program resume; at that point,
20959 @code{handle_exception} returns control to your own code on the target
20963 @cindex @code{breakpoint} subroutine, remote
20964 Use this auxiliary subroutine to make your program contain a
20965 breakpoint. Depending on the particular situation, this may be the only
20966 way for @value{GDBN} to get control. For instance, if your target
20967 machine has some sort of interrupt button, you won't need to call this;
20968 pressing the interrupt button transfers control to
20969 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20970 simply receiving characters on the serial port may also trigger a trap;
20971 again, in that situation, you don't need to call @code{breakpoint} from
20972 your own program---simply running @samp{target remote} from the host
20973 @value{GDBN} session gets control.
20975 Call @code{breakpoint} if none of these is true, or if you simply want
20976 to make certain your program stops at a predetermined point for the
20977 start of your debugging session.
20980 @node Bootstrapping
20981 @subsection What You Must Do for the Stub
20983 @cindex remote stub, support routines
20984 The debugging stubs that come with @value{GDBN} are set up for a particular
20985 chip architecture, but they have no information about the rest of your
20986 debugging target machine.
20988 First of all you need to tell the stub how to communicate with the
20992 @item int getDebugChar()
20993 @findex getDebugChar
20994 Write this subroutine to read a single character from the serial port.
20995 It may be identical to @code{getchar} for your target system; a
20996 different name is used to allow you to distinguish the two if you wish.
20998 @item void putDebugChar(int)
20999 @findex putDebugChar
21000 Write this subroutine to write a single character to the serial port.
21001 It may be identical to @code{putchar} for your target system; a
21002 different name is used to allow you to distinguish the two if you wish.
21005 @cindex control C, and remote debugging
21006 @cindex interrupting remote targets
21007 If you want @value{GDBN} to be able to stop your program while it is
21008 running, you need to use an interrupt-driven serial driver, and arrange
21009 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21010 character). That is the character which @value{GDBN} uses to tell the
21011 remote system to stop.
21013 Getting the debugging target to return the proper status to @value{GDBN}
21014 probably requires changes to the standard stub; one quick and dirty way
21015 is to just execute a breakpoint instruction (the ``dirty'' part is that
21016 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21018 Other routines you need to supply are:
21021 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21022 @findex exceptionHandler
21023 Write this function to install @var{exception_address} in the exception
21024 handling tables. You need to do this because the stub does not have any
21025 way of knowing what the exception handling tables on your target system
21026 are like (for example, the processor's table might be in @sc{rom},
21027 containing entries which point to a table in @sc{ram}).
21028 The @var{exception_number} specifies the exception which should be changed;
21029 its meaning is architecture-dependent (for example, different numbers
21030 might represent divide by zero, misaligned access, etc). When this
21031 exception occurs, control should be transferred directly to
21032 @var{exception_address}, and the processor state (stack, registers,
21033 and so on) should be just as it is when a processor exception occurs. So if
21034 you want to use a jump instruction to reach @var{exception_address}, it
21035 should be a simple jump, not a jump to subroutine.
21037 For the 386, @var{exception_address} should be installed as an interrupt
21038 gate so that interrupts are masked while the handler runs. The gate
21039 should be at privilege level 0 (the most privileged level). The
21040 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21041 help from @code{exceptionHandler}.
21043 @item void flush_i_cache()
21044 @findex flush_i_cache
21045 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21046 instruction cache, if any, on your target machine. If there is no
21047 instruction cache, this subroutine may be a no-op.
21049 On target machines that have instruction caches, @value{GDBN} requires this
21050 function to make certain that the state of your program is stable.
21054 You must also make sure this library routine is available:
21057 @item void *memset(void *, int, int)
21059 This is the standard library function @code{memset} that sets an area of
21060 memory to a known value. If you have one of the free versions of
21061 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21062 either obtain it from your hardware manufacturer, or write your own.
21065 If you do not use the GNU C compiler, you may need other standard
21066 library subroutines as well; this varies from one stub to another,
21067 but in general the stubs are likely to use any of the common library
21068 subroutines which @code{@value{NGCC}} generates as inline code.
21071 @node Debug Session
21072 @subsection Putting it All Together
21074 @cindex remote serial debugging summary
21075 In summary, when your program is ready to debug, you must follow these
21080 Make sure you have defined the supporting low-level routines
21081 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21083 @code{getDebugChar}, @code{putDebugChar},
21084 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21088 Insert these lines in your program's startup code, before the main
21089 procedure is called:
21096 On some machines, when a breakpoint trap is raised, the hardware
21097 automatically makes the PC point to the instruction after the
21098 breakpoint. If your machine doesn't do that, you may need to adjust
21099 @code{handle_exception} to arrange for it to return to the instruction
21100 after the breakpoint on this first invocation, so that your program
21101 doesn't keep hitting the initial breakpoint instead of making
21105 For the 680x0 stub only, you need to provide a variable called
21106 @code{exceptionHook}. Normally you just use:
21109 void (*exceptionHook)() = 0;
21113 but if before calling @code{set_debug_traps}, you set it to point to a
21114 function in your program, that function is called when
21115 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21116 error). The function indicated by @code{exceptionHook} is called with
21117 one parameter: an @code{int} which is the exception number.
21120 Compile and link together: your program, the @value{GDBN} debugging stub for
21121 your target architecture, and the supporting subroutines.
21124 Make sure you have a serial connection between your target machine and
21125 the @value{GDBN} host, and identify the serial port on the host.
21128 @c The "remote" target now provides a `load' command, so we should
21129 @c document that. FIXME.
21130 Download your program to your target machine (or get it there by
21131 whatever means the manufacturer provides), and start it.
21134 Start @value{GDBN} on the host, and connect to the target
21135 (@pxref{Connecting,,Connecting to a Remote Target}).
21139 @node Configurations
21140 @chapter Configuration-Specific Information
21142 While nearly all @value{GDBN} commands are available for all native and
21143 cross versions of the debugger, there are some exceptions. This chapter
21144 describes things that are only available in certain configurations.
21146 There are three major categories of configurations: native
21147 configurations, where the host and target are the same, embedded
21148 operating system configurations, which are usually the same for several
21149 different processor architectures, and bare embedded processors, which
21150 are quite different from each other.
21155 * Embedded Processors::
21162 This section describes details specific to particular native
21166 * BSD libkvm Interface:: Debugging BSD kernel memory images
21167 * SVR4 Process Information:: SVR4 process information
21168 * DJGPP Native:: Features specific to the DJGPP port
21169 * Cygwin Native:: Features specific to the Cygwin port
21170 * Hurd Native:: Features specific to @sc{gnu} Hurd
21171 * Darwin:: Features specific to Darwin
21174 @node BSD libkvm Interface
21175 @subsection BSD libkvm Interface
21178 @cindex kernel memory image
21179 @cindex kernel crash dump
21181 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21182 interface that provides a uniform interface for accessing kernel virtual
21183 memory images, including live systems and crash dumps. @value{GDBN}
21184 uses this interface to allow you to debug live kernels and kernel crash
21185 dumps on many native BSD configurations. This is implemented as a
21186 special @code{kvm} debugging target. For debugging a live system, load
21187 the currently running kernel into @value{GDBN} and connect to the
21191 (@value{GDBP}) @b{target kvm}
21194 For debugging crash dumps, provide the file name of the crash dump as an
21198 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21201 Once connected to the @code{kvm} target, the following commands are
21207 Set current context from the @dfn{Process Control Block} (PCB) address.
21210 Set current context from proc address. This command isn't available on
21211 modern FreeBSD systems.
21214 @node SVR4 Process Information
21215 @subsection SVR4 Process Information
21217 @cindex examine process image
21218 @cindex process info via @file{/proc}
21220 Many versions of SVR4 and compatible systems provide a facility called
21221 @samp{/proc} that can be used to examine the image of a running
21222 process using file-system subroutines.
21224 If @value{GDBN} is configured for an operating system with this
21225 facility, the command @code{info proc} is available to report
21226 information about the process running your program, or about any
21227 process running on your system. This includes, as of this writing,
21228 @sc{gnu}/Linux and Solaris, for example.
21230 This command may also work on core files that were created on a system
21231 that has the @samp{/proc} facility.
21237 @itemx info proc @var{process-id}
21238 Summarize available information about any running process. If a
21239 process ID is specified by @var{process-id}, display information about
21240 that process; otherwise display information about the program being
21241 debugged. The summary includes the debugged process ID, the command
21242 line used to invoke it, its current working directory, and its
21243 executable file's absolute file name.
21245 On some systems, @var{process-id} can be of the form
21246 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21247 within a process. If the optional @var{pid} part is missing, it means
21248 a thread from the process being debugged (the leading @samp{/} still
21249 needs to be present, or else @value{GDBN} will interpret the number as
21250 a process ID rather than a thread ID).
21252 @item info proc cmdline
21253 @cindex info proc cmdline
21254 Show the original command line of the process. This command is
21255 specific to @sc{gnu}/Linux.
21257 @item info proc cwd
21258 @cindex info proc cwd
21259 Show the current working directory of the process. This command is
21260 specific to @sc{gnu}/Linux.
21262 @item info proc exe
21263 @cindex info proc exe
21264 Show the name of executable of the process. This command is specific
21267 @item info proc mappings
21268 @cindex memory address space mappings
21269 Report the memory address space ranges accessible in the program, with
21270 information on whether the process has read, write, or execute access
21271 rights to each range. On @sc{gnu}/Linux systems, each memory range
21272 includes the object file which is mapped to that range, instead of the
21273 memory access rights to that range.
21275 @item info proc stat
21276 @itemx info proc status
21277 @cindex process detailed status information
21278 These subcommands are specific to @sc{gnu}/Linux systems. They show
21279 the process-related information, including the user ID and group ID;
21280 how many threads are there in the process; its virtual memory usage;
21281 the signals that are pending, blocked, and ignored; its TTY; its
21282 consumption of system and user time; its stack size; its @samp{nice}
21283 value; etc. For more information, see the @samp{proc} man page
21284 (type @kbd{man 5 proc} from your shell prompt).
21286 @item info proc all
21287 Show all the information about the process described under all of the
21288 above @code{info proc} subcommands.
21291 @comment These sub-options of 'info proc' were not included when
21292 @comment procfs.c was re-written. Keep their descriptions around
21293 @comment against the day when someone finds the time to put them back in.
21294 @kindex info proc times
21295 @item info proc times
21296 Starting time, user CPU time, and system CPU time for your program and
21299 @kindex info proc id
21301 Report on the process IDs related to your program: its own process ID,
21302 the ID of its parent, the process group ID, and the session ID.
21305 @item set procfs-trace
21306 @kindex set procfs-trace
21307 @cindex @code{procfs} API calls
21308 This command enables and disables tracing of @code{procfs} API calls.
21310 @item show procfs-trace
21311 @kindex show procfs-trace
21312 Show the current state of @code{procfs} API call tracing.
21314 @item set procfs-file @var{file}
21315 @kindex set procfs-file
21316 Tell @value{GDBN} to write @code{procfs} API trace to the named
21317 @var{file}. @value{GDBN} appends the trace info to the previous
21318 contents of the file. The default is to display the trace on the
21321 @item show procfs-file
21322 @kindex show procfs-file
21323 Show the file to which @code{procfs} API trace is written.
21325 @item proc-trace-entry
21326 @itemx proc-trace-exit
21327 @itemx proc-untrace-entry
21328 @itemx proc-untrace-exit
21329 @kindex proc-trace-entry
21330 @kindex proc-trace-exit
21331 @kindex proc-untrace-entry
21332 @kindex proc-untrace-exit
21333 These commands enable and disable tracing of entries into and exits
21334 from the @code{syscall} interface.
21337 @kindex info pidlist
21338 @cindex process list, QNX Neutrino
21339 For QNX Neutrino only, this command displays the list of all the
21340 processes and all the threads within each process.
21343 @kindex info meminfo
21344 @cindex mapinfo list, QNX Neutrino
21345 For QNX Neutrino only, this command displays the list of all mapinfos.
21349 @subsection Features for Debugging @sc{djgpp} Programs
21350 @cindex @sc{djgpp} debugging
21351 @cindex native @sc{djgpp} debugging
21352 @cindex MS-DOS-specific commands
21355 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21356 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21357 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21358 top of real-mode DOS systems and their emulations.
21360 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21361 defines a few commands specific to the @sc{djgpp} port. This
21362 subsection describes those commands.
21367 This is a prefix of @sc{djgpp}-specific commands which print
21368 information about the target system and important OS structures.
21371 @cindex MS-DOS system info
21372 @cindex free memory information (MS-DOS)
21373 @item info dos sysinfo
21374 This command displays assorted information about the underlying
21375 platform: the CPU type and features, the OS version and flavor, the
21376 DPMI version, and the available conventional and DPMI memory.
21381 @cindex segment descriptor tables
21382 @cindex descriptor tables display
21384 @itemx info dos ldt
21385 @itemx info dos idt
21386 These 3 commands display entries from, respectively, Global, Local,
21387 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21388 tables are data structures which store a descriptor for each segment
21389 that is currently in use. The segment's selector is an index into a
21390 descriptor table; the table entry for that index holds the
21391 descriptor's base address and limit, and its attributes and access
21394 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21395 segment (used for both data and the stack), and a DOS segment (which
21396 allows access to DOS/BIOS data structures and absolute addresses in
21397 conventional memory). However, the DPMI host will usually define
21398 additional segments in order to support the DPMI environment.
21400 @cindex garbled pointers
21401 These commands allow to display entries from the descriptor tables.
21402 Without an argument, all entries from the specified table are
21403 displayed. An argument, which should be an integer expression, means
21404 display a single entry whose index is given by the argument. For
21405 example, here's a convenient way to display information about the
21406 debugged program's data segment:
21409 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21410 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21414 This comes in handy when you want to see whether a pointer is outside
21415 the data segment's limit (i.e.@: @dfn{garbled}).
21417 @cindex page tables display (MS-DOS)
21419 @itemx info dos pte
21420 These two commands display entries from, respectively, the Page
21421 Directory and the Page Tables. Page Directories and Page Tables are
21422 data structures which control how virtual memory addresses are mapped
21423 into physical addresses. A Page Table includes an entry for every
21424 page of memory that is mapped into the program's address space; there
21425 may be several Page Tables, each one holding up to 4096 entries. A
21426 Page Directory has up to 4096 entries, one each for every Page Table
21427 that is currently in use.
21429 Without an argument, @kbd{info dos pde} displays the entire Page
21430 Directory, and @kbd{info dos pte} displays all the entries in all of
21431 the Page Tables. An argument, an integer expression, given to the
21432 @kbd{info dos pde} command means display only that entry from the Page
21433 Directory table. An argument given to the @kbd{info dos pte} command
21434 means display entries from a single Page Table, the one pointed to by
21435 the specified entry in the Page Directory.
21437 @cindex direct memory access (DMA) on MS-DOS
21438 These commands are useful when your program uses @dfn{DMA} (Direct
21439 Memory Access), which needs physical addresses to program the DMA
21442 These commands are supported only with some DPMI servers.
21444 @cindex physical address from linear address
21445 @item info dos address-pte @var{addr}
21446 This command displays the Page Table entry for a specified linear
21447 address. The argument @var{addr} is a linear address which should
21448 already have the appropriate segment's base address added to it,
21449 because this command accepts addresses which may belong to @emph{any}
21450 segment. For example, here's how to display the Page Table entry for
21451 the page where a variable @code{i} is stored:
21454 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21455 @exdent @code{Page Table entry for address 0x11a00d30:}
21456 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21460 This says that @code{i} is stored at offset @code{0xd30} from the page
21461 whose physical base address is @code{0x02698000}, and shows all the
21462 attributes of that page.
21464 Note that you must cast the addresses of variables to a @code{char *},
21465 since otherwise the value of @code{__djgpp_base_address}, the base
21466 address of all variables and functions in a @sc{djgpp} program, will
21467 be added using the rules of C pointer arithmetics: if @code{i} is
21468 declared an @code{int}, @value{GDBN} will add 4 times the value of
21469 @code{__djgpp_base_address} to the address of @code{i}.
21471 Here's another example, it displays the Page Table entry for the
21475 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21476 @exdent @code{Page Table entry for address 0x29110:}
21477 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21481 (The @code{+ 3} offset is because the transfer buffer's address is the
21482 3rd member of the @code{_go32_info_block} structure.) The output
21483 clearly shows that this DPMI server maps the addresses in conventional
21484 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21485 linear (@code{0x29110}) addresses are identical.
21487 This command is supported only with some DPMI servers.
21490 @cindex DOS serial data link, remote debugging
21491 In addition to native debugging, the DJGPP port supports remote
21492 debugging via a serial data link. The following commands are specific
21493 to remote serial debugging in the DJGPP port of @value{GDBN}.
21496 @kindex set com1base
21497 @kindex set com1irq
21498 @kindex set com2base
21499 @kindex set com2irq
21500 @kindex set com3base
21501 @kindex set com3irq
21502 @kindex set com4base
21503 @kindex set com4irq
21504 @item set com1base @var{addr}
21505 This command sets the base I/O port address of the @file{COM1} serial
21508 @item set com1irq @var{irq}
21509 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21510 for the @file{COM1} serial port.
21512 There are similar commands @samp{set com2base}, @samp{set com3irq},
21513 etc.@: for setting the port address and the @code{IRQ} lines for the
21516 @kindex show com1base
21517 @kindex show com1irq
21518 @kindex show com2base
21519 @kindex show com2irq
21520 @kindex show com3base
21521 @kindex show com3irq
21522 @kindex show com4base
21523 @kindex show com4irq
21524 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21525 display the current settings of the base address and the @code{IRQ}
21526 lines used by the COM ports.
21529 @kindex info serial
21530 @cindex DOS serial port status
21531 This command prints the status of the 4 DOS serial ports. For each
21532 port, it prints whether it's active or not, its I/O base address and
21533 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21534 counts of various errors encountered so far.
21538 @node Cygwin Native
21539 @subsection Features for Debugging MS Windows PE Executables
21540 @cindex MS Windows debugging
21541 @cindex native Cygwin debugging
21542 @cindex Cygwin-specific commands
21544 @value{GDBN} supports native debugging of MS Windows programs, including
21545 DLLs with and without symbolic debugging information.
21547 @cindex Ctrl-BREAK, MS-Windows
21548 @cindex interrupt debuggee on MS-Windows
21549 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21550 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21551 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21552 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21553 sequence, which can be used to interrupt the debuggee even if it
21556 There are various additional Cygwin-specific commands, described in
21557 this section. Working with DLLs that have no debugging symbols is
21558 described in @ref{Non-debug DLL Symbols}.
21563 This is a prefix of MS Windows-specific commands which print
21564 information about the target system and important OS structures.
21566 @item info w32 selector
21567 This command displays information returned by
21568 the Win32 API @code{GetThreadSelectorEntry} function.
21569 It takes an optional argument that is evaluated to
21570 a long value to give the information about this given selector.
21571 Without argument, this command displays information
21572 about the six segment registers.
21574 @item info w32 thread-information-block
21575 This command displays thread specific information stored in the
21576 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21577 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21579 @kindex signal-event
21580 @item signal-event @var{id}
21581 This command signals an event with user-provided @var{id}. Used to resume
21582 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21584 To use it, create or edit the following keys in
21585 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21586 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21587 (for x86_64 versions):
21591 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21592 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21593 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21595 The first @code{%ld} will be replaced by the process ID of the
21596 crashing process, the second @code{%ld} will be replaced by the ID of
21597 the event that blocks the crashing process, waiting for @value{GDBN}
21601 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21602 make the system run debugger specified by the Debugger key
21603 automatically, @code{0} will cause a dialog box with ``OK'' and
21604 ``Cancel'' buttons to appear, which allows the user to either
21605 terminate the crashing process (OK) or debug it (Cancel).
21608 @kindex set cygwin-exceptions
21609 @cindex debugging the Cygwin DLL
21610 @cindex Cygwin DLL, debugging
21611 @item set cygwin-exceptions @var{mode}
21612 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21613 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21614 @value{GDBN} will delay recognition of exceptions, and may ignore some
21615 exceptions which seem to be caused by internal Cygwin DLL
21616 ``bookkeeping''. This option is meant primarily for debugging the
21617 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21618 @value{GDBN} users with false @code{SIGSEGV} signals.
21620 @kindex show cygwin-exceptions
21621 @item show cygwin-exceptions
21622 Displays whether @value{GDBN} will break on exceptions that happen
21623 inside the Cygwin DLL itself.
21625 @kindex set new-console
21626 @item set new-console @var{mode}
21627 If @var{mode} is @code{on} the debuggee will
21628 be started in a new console on next start.
21629 If @var{mode} is @code{off}, the debuggee will
21630 be started in the same console as the debugger.
21632 @kindex show new-console
21633 @item show new-console
21634 Displays whether a new console is used
21635 when the debuggee is started.
21637 @kindex set new-group
21638 @item set new-group @var{mode}
21639 This boolean value controls whether the debuggee should
21640 start a new group or stay in the same group as the debugger.
21641 This affects the way the Windows OS handles
21644 @kindex show new-group
21645 @item show new-group
21646 Displays current value of new-group boolean.
21648 @kindex set debugevents
21649 @item set debugevents
21650 This boolean value adds debug output concerning kernel events related
21651 to the debuggee seen by the debugger. This includes events that
21652 signal thread and process creation and exit, DLL loading and
21653 unloading, console interrupts, and debugging messages produced by the
21654 Windows @code{OutputDebugString} API call.
21656 @kindex set debugexec
21657 @item set debugexec
21658 This boolean value adds debug output concerning execute events
21659 (such as resume thread) seen by the debugger.
21661 @kindex set debugexceptions
21662 @item set debugexceptions
21663 This boolean value adds debug output concerning exceptions in the
21664 debuggee seen by the debugger.
21666 @kindex set debugmemory
21667 @item set debugmemory
21668 This boolean value adds debug output concerning debuggee memory reads
21669 and writes by the debugger.
21673 This boolean values specifies whether the debuggee is called
21674 via a shell or directly (default value is on).
21678 Displays if the debuggee will be started with a shell.
21683 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21686 @node Non-debug DLL Symbols
21687 @subsubsection Support for DLLs without Debugging Symbols
21688 @cindex DLLs with no debugging symbols
21689 @cindex Minimal symbols and DLLs
21691 Very often on windows, some of the DLLs that your program relies on do
21692 not include symbolic debugging information (for example,
21693 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21694 symbols in a DLL, it relies on the minimal amount of symbolic
21695 information contained in the DLL's export table. This section
21696 describes working with such symbols, known internally to @value{GDBN} as
21697 ``minimal symbols''.
21699 Note that before the debugged program has started execution, no DLLs
21700 will have been loaded. The easiest way around this problem is simply to
21701 start the program --- either by setting a breakpoint or letting the
21702 program run once to completion.
21704 @subsubsection DLL Name Prefixes
21706 In keeping with the naming conventions used by the Microsoft debugging
21707 tools, DLL export symbols are made available with a prefix based on the
21708 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21709 also entered into the symbol table, so @code{CreateFileA} is often
21710 sufficient. In some cases there will be name clashes within a program
21711 (particularly if the executable itself includes full debugging symbols)
21712 necessitating the use of the fully qualified name when referring to the
21713 contents of the DLL. Use single-quotes around the name to avoid the
21714 exclamation mark (``!'') being interpreted as a language operator.
21716 Note that the internal name of the DLL may be all upper-case, even
21717 though the file name of the DLL is lower-case, or vice-versa. Since
21718 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21719 some confusion. If in doubt, try the @code{info functions} and
21720 @code{info variables} commands or even @code{maint print msymbols}
21721 (@pxref{Symbols}). Here's an example:
21724 (@value{GDBP}) info function CreateFileA
21725 All functions matching regular expression "CreateFileA":
21727 Non-debugging symbols:
21728 0x77e885f4 CreateFileA
21729 0x77e885f4 KERNEL32!CreateFileA
21733 (@value{GDBP}) info function !
21734 All functions matching regular expression "!":
21736 Non-debugging symbols:
21737 0x6100114c cygwin1!__assert
21738 0x61004034 cygwin1!_dll_crt0@@0
21739 0x61004240 cygwin1!dll_crt0(per_process *)
21743 @subsubsection Working with Minimal Symbols
21745 Symbols extracted from a DLL's export table do not contain very much
21746 type information. All that @value{GDBN} can do is guess whether a symbol
21747 refers to a function or variable depending on the linker section that
21748 contains the symbol. Also note that the actual contents of the memory
21749 contained in a DLL are not available unless the program is running. This
21750 means that you cannot examine the contents of a variable or disassemble
21751 a function within a DLL without a running program.
21753 Variables are generally treated as pointers and dereferenced
21754 automatically. For this reason, it is often necessary to prefix a
21755 variable name with the address-of operator (``&'') and provide explicit
21756 type information in the command. Here's an example of the type of
21760 (@value{GDBP}) print 'cygwin1!__argv'
21765 (@value{GDBP}) x 'cygwin1!__argv'
21766 0x10021610: "\230y\""
21769 And two possible solutions:
21772 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21773 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21777 (@value{GDBP}) x/2x &'cygwin1!__argv'
21778 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21779 (@value{GDBP}) x/x 0x10021608
21780 0x10021608: 0x0022fd98
21781 (@value{GDBP}) x/s 0x0022fd98
21782 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21785 Setting a break point within a DLL is possible even before the program
21786 starts execution. However, under these circumstances, @value{GDBN} can't
21787 examine the initial instructions of the function in order to skip the
21788 function's frame set-up code. You can work around this by using ``*&''
21789 to set the breakpoint at a raw memory address:
21792 (@value{GDBP}) break *&'python22!PyOS_Readline'
21793 Breakpoint 1 at 0x1e04eff0
21796 The author of these extensions is not entirely convinced that setting a
21797 break point within a shared DLL like @file{kernel32.dll} is completely
21801 @subsection Commands Specific to @sc{gnu} Hurd Systems
21802 @cindex @sc{gnu} Hurd debugging
21804 This subsection describes @value{GDBN} commands specific to the
21805 @sc{gnu} Hurd native debugging.
21810 @kindex set signals@r{, Hurd command}
21811 @kindex set sigs@r{, Hurd command}
21812 This command toggles the state of inferior signal interception by
21813 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21814 affected by this command. @code{sigs} is a shorthand alias for
21819 @kindex show signals@r{, Hurd command}
21820 @kindex show sigs@r{, Hurd command}
21821 Show the current state of intercepting inferior's signals.
21823 @item set signal-thread
21824 @itemx set sigthread
21825 @kindex set signal-thread
21826 @kindex set sigthread
21827 This command tells @value{GDBN} which thread is the @code{libc} signal
21828 thread. That thread is run when a signal is delivered to a running
21829 process. @code{set sigthread} is the shorthand alias of @code{set
21832 @item show signal-thread
21833 @itemx show sigthread
21834 @kindex show signal-thread
21835 @kindex show sigthread
21836 These two commands show which thread will run when the inferior is
21837 delivered a signal.
21840 @kindex set stopped@r{, Hurd command}
21841 This commands tells @value{GDBN} that the inferior process is stopped,
21842 as with the @code{SIGSTOP} signal. The stopped process can be
21843 continued by delivering a signal to it.
21846 @kindex show stopped@r{, Hurd command}
21847 This command shows whether @value{GDBN} thinks the debuggee is
21850 @item set exceptions
21851 @kindex set exceptions@r{, Hurd command}
21852 Use this command to turn off trapping of exceptions in the inferior.
21853 When exception trapping is off, neither breakpoints nor
21854 single-stepping will work. To restore the default, set exception
21857 @item show exceptions
21858 @kindex show exceptions@r{, Hurd command}
21859 Show the current state of trapping exceptions in the inferior.
21861 @item set task pause
21862 @kindex set task@r{, Hurd commands}
21863 @cindex task attributes (@sc{gnu} Hurd)
21864 @cindex pause current task (@sc{gnu} Hurd)
21865 This command toggles task suspension when @value{GDBN} has control.
21866 Setting it to on takes effect immediately, and the task is suspended
21867 whenever @value{GDBN} gets control. Setting it to off will take
21868 effect the next time the inferior is continued. If this option is set
21869 to off, you can use @code{set thread default pause on} or @code{set
21870 thread pause on} (see below) to pause individual threads.
21872 @item show task pause
21873 @kindex show task@r{, Hurd commands}
21874 Show the current state of task suspension.
21876 @item set task detach-suspend-count
21877 @cindex task suspend count
21878 @cindex detach from task, @sc{gnu} Hurd
21879 This command sets the suspend count the task will be left with when
21880 @value{GDBN} detaches from it.
21882 @item show task detach-suspend-count
21883 Show the suspend count the task will be left with when detaching.
21885 @item set task exception-port
21886 @itemx set task excp
21887 @cindex task exception port, @sc{gnu} Hurd
21888 This command sets the task exception port to which @value{GDBN} will
21889 forward exceptions. The argument should be the value of the @dfn{send
21890 rights} of the task. @code{set task excp} is a shorthand alias.
21892 @item set noninvasive
21893 @cindex noninvasive task options
21894 This command switches @value{GDBN} to a mode that is the least
21895 invasive as far as interfering with the inferior is concerned. This
21896 is the same as using @code{set task pause}, @code{set exceptions}, and
21897 @code{set signals} to values opposite to the defaults.
21899 @item info send-rights
21900 @itemx info receive-rights
21901 @itemx info port-rights
21902 @itemx info port-sets
21903 @itemx info dead-names
21906 @cindex send rights, @sc{gnu} Hurd
21907 @cindex receive rights, @sc{gnu} Hurd
21908 @cindex port rights, @sc{gnu} Hurd
21909 @cindex port sets, @sc{gnu} Hurd
21910 @cindex dead names, @sc{gnu} Hurd
21911 These commands display information about, respectively, send rights,
21912 receive rights, port rights, port sets, and dead names of a task.
21913 There are also shorthand aliases: @code{info ports} for @code{info
21914 port-rights} and @code{info psets} for @code{info port-sets}.
21916 @item set thread pause
21917 @kindex set thread@r{, Hurd command}
21918 @cindex thread properties, @sc{gnu} Hurd
21919 @cindex pause current thread (@sc{gnu} Hurd)
21920 This command toggles current thread suspension when @value{GDBN} has
21921 control. Setting it to on takes effect immediately, and the current
21922 thread is suspended whenever @value{GDBN} gets control. Setting it to
21923 off will take effect the next time the inferior is continued.
21924 Normally, this command has no effect, since when @value{GDBN} has
21925 control, the whole task is suspended. However, if you used @code{set
21926 task pause off} (see above), this command comes in handy to suspend
21927 only the current thread.
21929 @item show thread pause
21930 @kindex show thread@r{, Hurd command}
21931 This command shows the state of current thread suspension.
21933 @item set thread run
21934 This command sets whether the current thread is allowed to run.
21936 @item show thread run
21937 Show whether the current thread is allowed to run.
21939 @item set thread detach-suspend-count
21940 @cindex thread suspend count, @sc{gnu} Hurd
21941 @cindex detach from thread, @sc{gnu} Hurd
21942 This command sets the suspend count @value{GDBN} will leave on a
21943 thread when detaching. This number is relative to the suspend count
21944 found by @value{GDBN} when it notices the thread; use @code{set thread
21945 takeover-suspend-count} to force it to an absolute value.
21947 @item show thread detach-suspend-count
21948 Show the suspend count @value{GDBN} will leave on the thread when
21951 @item set thread exception-port
21952 @itemx set thread excp
21953 Set the thread exception port to which to forward exceptions. This
21954 overrides the port set by @code{set task exception-port} (see above).
21955 @code{set thread excp} is the shorthand alias.
21957 @item set thread takeover-suspend-count
21958 Normally, @value{GDBN}'s thread suspend counts are relative to the
21959 value @value{GDBN} finds when it notices each thread. This command
21960 changes the suspend counts to be absolute instead.
21962 @item set thread default
21963 @itemx show thread default
21964 @cindex thread default settings, @sc{gnu} Hurd
21965 Each of the above @code{set thread} commands has a @code{set thread
21966 default} counterpart (e.g., @code{set thread default pause}, @code{set
21967 thread default exception-port}, etc.). The @code{thread default}
21968 variety of commands sets the default thread properties for all
21969 threads; you can then change the properties of individual threads with
21970 the non-default commands.
21977 @value{GDBN} provides the following commands specific to the Darwin target:
21980 @item set debug darwin @var{num}
21981 @kindex set debug darwin
21982 When set to a non zero value, enables debugging messages specific to
21983 the Darwin support. Higher values produce more verbose output.
21985 @item show debug darwin
21986 @kindex show debug darwin
21987 Show the current state of Darwin messages.
21989 @item set debug mach-o @var{num}
21990 @kindex set debug mach-o
21991 When set to a non zero value, enables debugging messages while
21992 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21993 file format used on Darwin for object and executable files.) Higher
21994 values produce more verbose output. This is a command to diagnose
21995 problems internal to @value{GDBN} and should not be needed in normal
21998 @item show debug mach-o
21999 @kindex show debug mach-o
22000 Show the current state of Mach-O file messages.
22002 @item set mach-exceptions on
22003 @itemx set mach-exceptions off
22004 @kindex set mach-exceptions
22005 On Darwin, faults are first reported as a Mach exception and are then
22006 mapped to a Posix signal. Use this command to turn on trapping of
22007 Mach exceptions in the inferior. This might be sometimes useful to
22008 better understand the cause of a fault. The default is off.
22010 @item show mach-exceptions
22011 @kindex show mach-exceptions
22012 Show the current state of exceptions trapping.
22017 @section Embedded Operating Systems
22019 This section describes configurations involving the debugging of
22020 embedded operating systems that are available for several different
22023 @value{GDBN} includes the ability to debug programs running on
22024 various real-time operating systems.
22026 @node Embedded Processors
22027 @section Embedded Processors
22029 This section goes into details specific to particular embedded
22032 @cindex send command to simulator
22033 Whenever a specific embedded processor has a simulator, @value{GDBN}
22034 allows to send an arbitrary command to the simulator.
22037 @item sim @var{command}
22038 @kindex sim@r{, a command}
22039 Send an arbitrary @var{command} string to the simulator. Consult the
22040 documentation for the specific simulator in use for information about
22041 acceptable commands.
22046 * ARC:: Synopsys ARC
22048 * M68K:: Motorola M68K
22049 * MicroBlaze:: Xilinx MicroBlaze
22050 * MIPS Embedded:: MIPS Embedded
22051 * PowerPC Embedded:: PowerPC Embedded
22054 * Super-H:: Renesas Super-H
22058 @subsection Synopsys ARC
22059 @cindex Synopsys ARC
22060 @cindex ARC specific commands
22066 @value{GDBN} provides the following ARC-specific commands:
22069 @item set debug arc
22070 @kindex set debug arc
22071 Control the level of ARC specific debug messages. Use 0 for no messages (the
22072 default) and 1 for debug messages. At present higher values offer no further
22075 @item show debug arc
22076 @kindex show debug arc
22077 Show the level of ARC specific debugging in operation.
22084 @value{GDBN} provides the following ARM-specific commands:
22087 @item set arm disassembler
22089 This commands selects from a list of disassembly styles. The
22090 @code{"std"} style is the standard style.
22092 @item show arm disassembler
22094 Show the current disassembly style.
22096 @item set arm apcs32
22097 @cindex ARM 32-bit mode
22098 This command toggles ARM operation mode between 32-bit and 26-bit.
22100 @item show arm apcs32
22101 Display the current usage of the ARM 32-bit mode.
22103 @item set arm fpu @var{fputype}
22104 This command sets the ARM floating-point unit (FPU) type. The
22105 argument @var{fputype} can be one of these:
22109 Determine the FPU type by querying the OS ABI.
22111 Software FPU, with mixed-endian doubles on little-endian ARM
22114 GCC-compiled FPA co-processor.
22116 Software FPU with pure-endian doubles.
22122 Show the current type of the FPU.
22125 This command forces @value{GDBN} to use the specified ABI.
22128 Show the currently used ABI.
22130 @item set arm fallback-mode (arm|thumb|auto)
22131 @value{GDBN} uses the symbol table, when available, to determine
22132 whether instructions are ARM or Thumb. This command controls
22133 @value{GDBN}'s default behavior when the symbol table is not
22134 available. The default is @samp{auto}, which causes @value{GDBN} to
22135 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22138 @item show arm fallback-mode
22139 Show the current fallback instruction mode.
22141 @item set arm force-mode (arm|thumb|auto)
22142 This command overrides use of the symbol table to determine whether
22143 instructions are ARM or Thumb. The default is @samp{auto}, which
22144 causes @value{GDBN} to use the symbol table and then the setting
22145 of @samp{set arm fallback-mode}.
22147 @item show arm force-mode
22148 Show the current forced instruction mode.
22150 @item set debug arm
22151 Toggle whether to display ARM-specific debugging messages from the ARM
22152 target support subsystem.
22154 @item show debug arm
22155 Show whether ARM-specific debugging messages are enabled.
22159 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22160 The @value{GDBN} ARM simulator accepts the following optional arguments.
22163 @item --swi-support=@var{type}
22164 Tell the simulator which SWI interfaces to support. The argument
22165 @var{type} may be a comma separated list of the following values.
22166 The default value is @code{all}.
22181 The Motorola m68k configuration includes ColdFire support.
22184 @subsection MicroBlaze
22185 @cindex Xilinx MicroBlaze
22186 @cindex XMD, Xilinx Microprocessor Debugger
22188 The MicroBlaze is a soft-core processor supported on various Xilinx
22189 FPGAs, such as Spartan or Virtex series. Boards with these processors
22190 usually have JTAG ports which connect to a host system running the Xilinx
22191 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22192 This host system is used to download the configuration bitstream to
22193 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22194 communicates with the target board using the JTAG interface and
22195 presents a @code{gdbserver} interface to the board. By default
22196 @code{xmd} uses port @code{1234}. (While it is possible to change
22197 this default port, it requires the use of undocumented @code{xmd}
22198 commands. Contact Xilinx support if you need to do this.)
22200 Use these GDB commands to connect to the MicroBlaze target processor.
22203 @item target remote :1234
22204 Use this command to connect to the target if you are running @value{GDBN}
22205 on the same system as @code{xmd}.
22207 @item target remote @var{xmd-host}:1234
22208 Use this command to connect to the target if it is connected to @code{xmd}
22209 running on a different system named @var{xmd-host}.
22212 Use this command to download a program to the MicroBlaze target.
22214 @item set debug microblaze @var{n}
22215 Enable MicroBlaze-specific debugging messages if non-zero.
22217 @item show debug microblaze @var{n}
22218 Show MicroBlaze-specific debugging level.
22221 @node MIPS Embedded
22222 @subsection @acronym{MIPS} Embedded
22225 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22228 @item set mipsfpu double
22229 @itemx set mipsfpu single
22230 @itemx set mipsfpu none
22231 @itemx set mipsfpu auto
22232 @itemx show mipsfpu
22233 @kindex set mipsfpu
22234 @kindex show mipsfpu
22235 @cindex @acronym{MIPS} remote floating point
22236 @cindex floating point, @acronym{MIPS} remote
22237 If your target board does not support the @acronym{MIPS} floating point
22238 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22239 need this, you may wish to put the command in your @value{GDBN} init
22240 file). This tells @value{GDBN} how to find the return value of
22241 functions which return floating point values. It also allows
22242 @value{GDBN} to avoid saving the floating point registers when calling
22243 functions on the board. If you are using a floating point coprocessor
22244 with only single precision floating point support, as on the @sc{r4650}
22245 processor, use the command @samp{set mipsfpu single}. The default
22246 double precision floating point coprocessor may be selected using
22247 @samp{set mipsfpu double}.
22249 In previous versions the only choices were double precision or no
22250 floating point, so @samp{set mipsfpu on} will select double precision
22251 and @samp{set mipsfpu off} will select no floating point.
22253 As usual, you can inquire about the @code{mipsfpu} variable with
22254 @samp{show mipsfpu}.
22257 @node PowerPC Embedded
22258 @subsection PowerPC Embedded
22260 @cindex DVC register
22261 @value{GDBN} supports using the DVC (Data Value Compare) register to
22262 implement in hardware simple hardware watchpoint conditions of the form:
22265 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22266 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22269 The DVC register will be automatically used when @value{GDBN} detects
22270 such pattern in a condition expression, and the created watchpoint uses one
22271 debug register (either the @code{exact-watchpoints} option is on and the
22272 variable is scalar, or the variable has a length of one byte). This feature
22273 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22276 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22277 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22278 in which case watchpoints using only one debug register are created when
22279 watching variables of scalar types.
22281 You can create an artificial array to watch an arbitrary memory
22282 region using one of the following commands (@pxref{Expressions}):
22285 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22286 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22289 PowerPC embedded processors support masked watchpoints. See the discussion
22290 about the @code{mask} argument in @ref{Set Watchpoints}.
22292 @cindex ranged breakpoint
22293 PowerPC embedded processors support hardware accelerated
22294 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22295 the inferior whenever it executes an instruction at any address within
22296 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22297 use the @code{break-range} command.
22299 @value{GDBN} provides the following PowerPC-specific commands:
22302 @kindex break-range
22303 @item break-range @var{start-location}, @var{end-location}
22304 Set a breakpoint for an address range given by
22305 @var{start-location} and @var{end-location}, which can specify a function name,
22306 a line number, an offset of lines from the current line or from the start
22307 location, or an address of an instruction (see @ref{Specify Location},
22308 for a list of all the possible ways to specify a @var{location}.)
22309 The breakpoint will stop execution of the inferior whenever it
22310 executes an instruction at any address within the specified range,
22311 (including @var{start-location} and @var{end-location}.)
22313 @kindex set powerpc
22314 @item set powerpc soft-float
22315 @itemx show powerpc soft-float
22316 Force @value{GDBN} to use (or not use) a software floating point calling
22317 convention. By default, @value{GDBN} selects the calling convention based
22318 on the selected architecture and the provided executable file.
22320 @item set powerpc vector-abi
22321 @itemx show powerpc vector-abi
22322 Force @value{GDBN} to use the specified calling convention for vector
22323 arguments and return values. The valid options are @samp{auto};
22324 @samp{generic}, to avoid vector registers even if they are present;
22325 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22326 registers. By default, @value{GDBN} selects the calling convention
22327 based on the selected architecture and the provided executable file.
22329 @item set powerpc exact-watchpoints
22330 @itemx show powerpc exact-watchpoints
22331 Allow @value{GDBN} to use only one debug register when watching a variable
22332 of scalar type, thus assuming that the variable is accessed through the
22333 address of its first byte.
22338 @subsection Atmel AVR
22341 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22342 following AVR-specific commands:
22345 @item info io_registers
22346 @kindex info io_registers@r{, AVR}
22347 @cindex I/O registers (Atmel AVR)
22348 This command displays information about the AVR I/O registers. For
22349 each register, @value{GDBN} prints its number and value.
22356 When configured for debugging CRIS, @value{GDBN} provides the
22357 following CRIS-specific commands:
22360 @item set cris-version @var{ver}
22361 @cindex CRIS version
22362 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22363 The CRIS version affects register names and sizes. This command is useful in
22364 case autodetection of the CRIS version fails.
22366 @item show cris-version
22367 Show the current CRIS version.
22369 @item set cris-dwarf2-cfi
22370 @cindex DWARF-2 CFI and CRIS
22371 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22372 Change to @samp{off} when using @code{gcc-cris} whose version is below
22375 @item show cris-dwarf2-cfi
22376 Show the current state of using DWARF-2 CFI.
22378 @item set cris-mode @var{mode}
22380 Set the current CRIS mode to @var{mode}. It should only be changed when
22381 debugging in guru mode, in which case it should be set to
22382 @samp{guru} (the default is @samp{normal}).
22384 @item show cris-mode
22385 Show the current CRIS mode.
22389 @subsection Renesas Super-H
22392 For the Renesas Super-H processor, @value{GDBN} provides these
22396 @item set sh calling-convention @var{convention}
22397 @kindex set sh calling-convention
22398 Set the calling-convention used when calling functions from @value{GDBN}.
22399 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22400 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22401 convention. If the DWARF-2 information of the called function specifies
22402 that the function follows the Renesas calling convention, the function
22403 is called using the Renesas calling convention. If the calling convention
22404 is set to @samp{renesas}, the Renesas calling convention is always used,
22405 regardless of the DWARF-2 information. This can be used to override the
22406 default of @samp{gcc} if debug information is missing, or the compiler
22407 does not emit the DWARF-2 calling convention entry for a function.
22409 @item show sh calling-convention
22410 @kindex show sh calling-convention
22411 Show the current calling convention setting.
22416 @node Architectures
22417 @section Architectures
22419 This section describes characteristics of architectures that affect
22420 all uses of @value{GDBN} with the architecture, both native and cross.
22427 * HPPA:: HP PA architecture
22428 * SPU:: Cell Broadband Engine SPU architecture
22434 @subsection AArch64
22435 @cindex AArch64 support
22437 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22438 following special commands:
22441 @item set debug aarch64
22442 @kindex set debug aarch64
22443 This command determines whether AArch64 architecture-specific debugging
22444 messages are to be displayed.
22446 @item show debug aarch64
22447 Show whether AArch64 debugging messages are displayed.
22452 @subsection x86 Architecture-specific Issues
22455 @item set struct-convention @var{mode}
22456 @kindex set struct-convention
22457 @cindex struct return convention
22458 @cindex struct/union returned in registers
22459 Set the convention used by the inferior to return @code{struct}s and
22460 @code{union}s from functions to @var{mode}. Possible values of
22461 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22462 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22463 are returned on the stack, while @code{"reg"} means that a
22464 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22465 be returned in a register.
22467 @item show struct-convention
22468 @kindex show struct-convention
22469 Show the current setting of the convention to return @code{struct}s
22474 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22475 @cindex Intel Memory Protection Extensions (MPX).
22477 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22478 @footnote{The register named with capital letters represent the architecture
22479 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22480 which are the lower bound and upper bound. Bounds are effective addresses or
22481 memory locations. The upper bounds are architecturally represented in 1's
22482 complement form. A bound having lower bound = 0, and upper bound = 0
22483 (1's complement of all bits set) will allow access to the entire address space.
22485 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22486 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22487 display the upper bound performing the complement of one operation on the
22488 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22489 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22490 can also be noted that the upper bounds are inclusive.
22492 As an example, assume that the register BND0 holds bounds for a pointer having
22493 access allowed for the range between 0x32 and 0x71. The values present on
22494 bnd0raw and bnd registers are presented as follows:
22497 bnd0raw = @{0x32, 0xffffffff8e@}
22498 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22501 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22502 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22503 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22504 Python, the display includes the memory size, in bits, accessible to
22507 Bounds can also be stored in bounds tables, which are stored in
22508 application memory. These tables store bounds for pointers by specifying
22509 the bounds pointer's value along with its bounds. Evaluating and changing
22510 bounds located in bound tables is therefore interesting while investigating
22511 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22514 @item show mpx bound @var{pointer}
22515 @kindex show mpx bound
22516 Display bounds of the given @var{pointer}.
22518 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22519 @kindex set mpx bound
22520 Set the bounds of a pointer in the bound table.
22521 This command takes three parameters: @var{pointer} is the pointers
22522 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22523 for lower and upper bounds respectively.
22529 See the following section.
22532 @subsection @acronym{MIPS}
22534 @cindex stack on Alpha
22535 @cindex stack on @acronym{MIPS}
22536 @cindex Alpha stack
22537 @cindex @acronym{MIPS} stack
22538 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22539 sometimes requires @value{GDBN} to search backward in the object code to
22540 find the beginning of a function.
22542 @cindex response time, @acronym{MIPS} debugging
22543 To improve response time (especially for embedded applications, where
22544 @value{GDBN} may be restricted to a slow serial line for this search)
22545 you may want to limit the size of this search, using one of these
22549 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22550 @item set heuristic-fence-post @var{limit}
22551 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22552 search for the beginning of a function. A value of @var{0} (the
22553 default) means there is no limit. However, except for @var{0}, the
22554 larger the limit the more bytes @code{heuristic-fence-post} must search
22555 and therefore the longer it takes to run. You should only need to use
22556 this command when debugging a stripped executable.
22558 @item show heuristic-fence-post
22559 Display the current limit.
22563 These commands are available @emph{only} when @value{GDBN} is configured
22564 for debugging programs on Alpha or @acronym{MIPS} processors.
22566 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22570 @item set mips abi @var{arg}
22571 @kindex set mips abi
22572 @cindex set ABI for @acronym{MIPS}
22573 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22574 values of @var{arg} are:
22578 The default ABI associated with the current binary (this is the
22588 @item show mips abi
22589 @kindex show mips abi
22590 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22592 @item set mips compression @var{arg}
22593 @kindex set mips compression
22594 @cindex code compression, @acronym{MIPS}
22595 Tell @value{GDBN} which @acronym{MIPS} compressed
22596 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22597 inferior. @value{GDBN} uses this for code disassembly and other
22598 internal interpretation purposes. This setting is only referred to
22599 when no executable has been associated with the debugging session or
22600 the executable does not provide information about the encoding it uses.
22601 Otherwise this setting is automatically updated from information
22602 provided by the executable.
22604 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22605 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22606 executables containing @acronym{MIPS16} code frequently are not
22607 identified as such.
22609 This setting is ``sticky''; that is, it retains its value across
22610 debugging sessions until reset either explicitly with this command or
22611 implicitly from an executable.
22613 The compiler and/or assembler typically add symbol table annotations to
22614 identify functions compiled for the @acronym{MIPS16} or
22615 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22616 are present, @value{GDBN} uses them in preference to the global
22617 compressed @acronym{ISA} encoding setting.
22619 @item show mips compression
22620 @kindex show mips compression
22621 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22622 @value{GDBN} to debug the inferior.
22625 @itemx show mipsfpu
22626 @xref{MIPS Embedded, set mipsfpu}.
22628 @item set mips mask-address @var{arg}
22629 @kindex set mips mask-address
22630 @cindex @acronym{MIPS} addresses, masking
22631 This command determines whether the most-significant 32 bits of 64-bit
22632 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22633 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22634 setting, which lets @value{GDBN} determine the correct value.
22636 @item show mips mask-address
22637 @kindex show mips mask-address
22638 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22641 @item set remote-mips64-transfers-32bit-regs
22642 @kindex set remote-mips64-transfers-32bit-regs
22643 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22644 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22645 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22646 and 64 bits for other registers, set this option to @samp{on}.
22648 @item show remote-mips64-transfers-32bit-regs
22649 @kindex show remote-mips64-transfers-32bit-regs
22650 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22652 @item set debug mips
22653 @kindex set debug mips
22654 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22655 target code in @value{GDBN}.
22657 @item show debug mips
22658 @kindex show debug mips
22659 Show the current setting of @acronym{MIPS} debugging messages.
22665 @cindex HPPA support
22667 When @value{GDBN} is debugging the HP PA architecture, it provides the
22668 following special commands:
22671 @item set debug hppa
22672 @kindex set debug hppa
22673 This command determines whether HPPA architecture-specific debugging
22674 messages are to be displayed.
22676 @item show debug hppa
22677 Show whether HPPA debugging messages are displayed.
22679 @item maint print unwind @var{address}
22680 @kindex maint print unwind@r{, HPPA}
22681 This command displays the contents of the unwind table entry at the
22682 given @var{address}.
22688 @subsection Cell Broadband Engine SPU architecture
22689 @cindex Cell Broadband Engine
22692 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22693 it provides the following special commands:
22696 @item info spu event
22698 Display SPU event facility status. Shows current event mask
22699 and pending event status.
22701 @item info spu signal
22702 Display SPU signal notification facility status. Shows pending
22703 signal-control word and signal notification mode of both signal
22704 notification channels.
22706 @item info spu mailbox
22707 Display SPU mailbox facility status. Shows all pending entries,
22708 in order of processing, in each of the SPU Write Outbound,
22709 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22712 Display MFC DMA status. Shows all pending commands in the MFC
22713 DMA queue. For each entry, opcode, tag, class IDs, effective
22714 and local store addresses and transfer size are shown.
22716 @item info spu proxydma
22717 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22718 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22719 and local store addresses and transfer size are shown.
22723 When @value{GDBN} is debugging a combined PowerPC/SPU application
22724 on the Cell Broadband Engine, it provides in addition the following
22728 @item set spu stop-on-load @var{arg}
22730 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22731 will give control to the user when a new SPE thread enters its @code{main}
22732 function. The default is @code{off}.
22734 @item show spu stop-on-load
22736 Show whether to stop for new SPE threads.
22738 @item set spu auto-flush-cache @var{arg}
22739 Set whether to automatically flush the software-managed cache. When set to
22740 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22741 cache to be flushed whenever SPE execution stops. This provides a consistent
22742 view of PowerPC memory that is accessed via the cache. If an application
22743 does not use the software-managed cache, this option has no effect.
22745 @item show spu auto-flush-cache
22746 Show whether to automatically flush the software-managed cache.
22751 @subsection PowerPC
22752 @cindex PowerPC architecture
22754 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22755 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22756 numbers stored in the floating point registers. These values must be stored
22757 in two consecutive registers, always starting at an even register like
22758 @code{f0} or @code{f2}.
22760 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22761 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22762 @code{f2} and @code{f3} for @code{$dl1} and so on.
22764 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22765 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22768 @subsection Nios II
22769 @cindex Nios II architecture
22771 When @value{GDBN} is debugging the Nios II architecture,
22772 it provides the following special commands:
22776 @item set debug nios2
22777 @kindex set debug nios2
22778 This command turns on and off debugging messages for the Nios II
22779 target code in @value{GDBN}.
22781 @item show debug nios2
22782 @kindex show debug nios2
22783 Show the current setting of Nios II debugging messages.
22786 @node Controlling GDB
22787 @chapter Controlling @value{GDBN}
22789 You can alter the way @value{GDBN} interacts with you by using the
22790 @code{set} command. For commands controlling how @value{GDBN} displays
22791 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22796 * Editing:: Command editing
22797 * Command History:: Command history
22798 * Screen Size:: Screen size
22799 * Numbers:: Numbers
22800 * ABI:: Configuring the current ABI
22801 * Auto-loading:: Automatically loading associated files
22802 * Messages/Warnings:: Optional warnings and messages
22803 * Debugging Output:: Optional messages about internal happenings
22804 * Other Misc Settings:: Other Miscellaneous Settings
22812 @value{GDBN} indicates its readiness to read a command by printing a string
22813 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22814 can change the prompt string with the @code{set prompt} command. For
22815 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22816 the prompt in one of the @value{GDBN} sessions so that you can always tell
22817 which one you are talking to.
22819 @emph{Note:} @code{set prompt} does not add a space for you after the
22820 prompt you set. This allows you to set a prompt which ends in a space
22821 or a prompt that does not.
22825 @item set prompt @var{newprompt}
22826 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22828 @kindex show prompt
22830 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22833 Versions of @value{GDBN} that ship with Python scripting enabled have
22834 prompt extensions. The commands for interacting with these extensions
22838 @kindex set extended-prompt
22839 @item set extended-prompt @var{prompt}
22840 Set an extended prompt that allows for substitutions.
22841 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22842 substitution. Any escape sequences specified as part of the prompt
22843 string are replaced with the corresponding strings each time the prompt
22849 set extended-prompt Current working directory: \w (gdb)
22852 Note that when an extended-prompt is set, it takes control of the
22853 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22855 @kindex show extended-prompt
22856 @item show extended-prompt
22857 Prints the extended prompt. Any escape sequences specified as part of
22858 the prompt string with @code{set extended-prompt}, are replaced with the
22859 corresponding strings each time the prompt is displayed.
22863 @section Command Editing
22865 @cindex command line editing
22867 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22868 @sc{gnu} library provides consistent behavior for programs which provide a
22869 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22870 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22871 substitution, and a storage and recall of command history across
22872 debugging sessions.
22874 You may control the behavior of command line editing in @value{GDBN} with the
22875 command @code{set}.
22878 @kindex set editing
22881 @itemx set editing on
22882 Enable command line editing (enabled by default).
22884 @item set editing off
22885 Disable command line editing.
22887 @kindex show editing
22889 Show whether command line editing is enabled.
22892 @ifset SYSTEM_READLINE
22893 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22895 @ifclear SYSTEM_READLINE
22896 @xref{Command Line Editing},
22898 for more details about the Readline
22899 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22900 encouraged to read that chapter.
22902 @node Command History
22903 @section Command History
22904 @cindex command history
22906 @value{GDBN} can keep track of the commands you type during your
22907 debugging sessions, so that you can be certain of precisely what
22908 happened. Use these commands to manage the @value{GDBN} command
22911 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22912 package, to provide the history facility.
22913 @ifset SYSTEM_READLINE
22914 @xref{Using History Interactively, , , history, GNU History Library},
22916 @ifclear SYSTEM_READLINE
22917 @xref{Using History Interactively},
22919 for the detailed description of the History library.
22921 To issue a command to @value{GDBN} without affecting certain aspects of
22922 the state which is seen by users, prefix it with @samp{server }
22923 (@pxref{Server Prefix}). This
22924 means that this command will not affect the command history, nor will it
22925 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22926 pressed on a line by itself.
22928 @cindex @code{server}, command prefix
22929 The server prefix does not affect the recording of values into the value
22930 history; to print a value without recording it into the value history,
22931 use the @code{output} command instead of the @code{print} command.
22933 Here is the description of @value{GDBN} commands related to command
22937 @cindex history substitution
22938 @cindex history file
22939 @kindex set history filename
22940 @cindex @env{GDBHISTFILE}, environment variable
22941 @item set history filename @var{fname}
22942 Set the name of the @value{GDBN} command history file to @var{fname}.
22943 This is the file where @value{GDBN} reads an initial command history
22944 list, and where it writes the command history from this session when it
22945 exits. You can access this list through history expansion or through
22946 the history command editing characters listed below. This file defaults
22947 to the value of the environment variable @code{GDBHISTFILE}, or to
22948 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22951 @cindex save command history
22952 @kindex set history save
22953 @item set history save
22954 @itemx set history save on
22955 Record command history in a file, whose name may be specified with the
22956 @code{set history filename} command. By default, this option is disabled.
22958 @item set history save off
22959 Stop recording command history in a file.
22961 @cindex history size
22962 @kindex set history size
22963 @cindex @env{GDBHISTSIZE}, environment variable
22964 @item set history size @var{size}
22965 @itemx set history size unlimited
22966 Set the number of commands which @value{GDBN} keeps in its history list.
22967 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22968 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22969 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22970 either a negative number or the empty string, then the number of commands
22971 @value{GDBN} keeps in the history list is unlimited.
22973 @cindex remove duplicate history
22974 @kindex set history remove-duplicates
22975 @item set history remove-duplicates @var{count}
22976 @itemx set history remove-duplicates unlimited
22977 Control the removal of duplicate history entries in the command history list.
22978 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22979 history entries and remove the first entry that is a duplicate of the current
22980 entry being added to the command history list. If @var{count} is
22981 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22982 removal of duplicate history entries is disabled.
22984 Only history entries added during the current session are considered for
22985 removal. This option is set to 0 by default.
22989 History expansion assigns special meaning to the character @kbd{!}.
22990 @ifset SYSTEM_READLINE
22991 @xref{Event Designators, , , history, GNU History Library},
22993 @ifclear SYSTEM_READLINE
22994 @xref{Event Designators},
22998 @cindex history expansion, turn on/off
22999 Since @kbd{!} is also the logical not operator in C, history expansion
23000 is off by default. If you decide to enable history expansion with the
23001 @code{set history expansion on} command, you may sometimes need to
23002 follow @kbd{!} (when it is used as logical not, in an expression) with
23003 a space or a tab to prevent it from being expanded. The readline
23004 history facilities do not attempt substitution on the strings
23005 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23007 The commands to control history expansion are:
23010 @item set history expansion on
23011 @itemx set history expansion
23012 @kindex set history expansion
23013 Enable history expansion. History expansion is off by default.
23015 @item set history expansion off
23016 Disable history expansion.
23019 @kindex show history
23021 @itemx show history filename
23022 @itemx show history save
23023 @itemx show history size
23024 @itemx show history expansion
23025 These commands display the state of the @value{GDBN} history parameters.
23026 @code{show history} by itself displays all four states.
23031 @kindex show commands
23032 @cindex show last commands
23033 @cindex display command history
23034 @item show commands
23035 Display the last ten commands in the command history.
23037 @item show commands @var{n}
23038 Print ten commands centered on command number @var{n}.
23040 @item show commands +
23041 Print ten commands just after the commands last printed.
23045 @section Screen Size
23046 @cindex size of screen
23047 @cindex screen size
23050 @cindex pauses in output
23052 Certain commands to @value{GDBN} may produce large amounts of
23053 information output to the screen. To help you read all of it,
23054 @value{GDBN} pauses and asks you for input at the end of each page of
23055 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23056 to discard the remaining output. Also, the screen width setting
23057 determines when to wrap lines of output. Depending on what is being
23058 printed, @value{GDBN} tries to break the line at a readable place,
23059 rather than simply letting it overflow onto the following line.
23061 Normally @value{GDBN} knows the size of the screen from the terminal
23062 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23063 together with the value of the @code{TERM} environment variable and the
23064 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23065 you can override it with the @code{set height} and @code{set
23072 @kindex show height
23073 @item set height @var{lpp}
23074 @itemx set height unlimited
23076 @itemx set width @var{cpl}
23077 @itemx set width unlimited
23079 These @code{set} commands specify a screen height of @var{lpp} lines and
23080 a screen width of @var{cpl} characters. The associated @code{show}
23081 commands display the current settings.
23083 If you specify a height of either @code{unlimited} or zero lines,
23084 @value{GDBN} does not pause during output no matter how long the
23085 output is. This is useful if output is to a file or to an editor
23088 Likewise, you can specify @samp{set width unlimited} or @samp{set
23089 width 0} to prevent @value{GDBN} from wrapping its output.
23091 @item set pagination on
23092 @itemx set pagination off
23093 @kindex set pagination
23094 Turn the output pagination on or off; the default is on. Turning
23095 pagination off is the alternative to @code{set height unlimited}. Note that
23096 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23097 Options, -batch}) also automatically disables pagination.
23099 @item show pagination
23100 @kindex show pagination
23101 Show the current pagination mode.
23106 @cindex number representation
23107 @cindex entering numbers
23109 You can always enter numbers in octal, decimal, or hexadecimal in
23110 @value{GDBN} by the usual conventions: octal numbers begin with
23111 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23112 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23113 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23114 10; likewise, the default display for numbers---when no particular
23115 format is specified---is base 10. You can change the default base for
23116 both input and output with the commands described below.
23119 @kindex set input-radix
23120 @item set input-radix @var{base}
23121 Set the default base for numeric input. Supported choices
23122 for @var{base} are decimal 8, 10, or 16. The base must itself be
23123 specified either unambiguously or using the current input radix; for
23127 set input-radix 012
23128 set input-radix 10.
23129 set input-radix 0xa
23133 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23134 leaves the input radix unchanged, no matter what it was, since
23135 @samp{10}, being without any leading or trailing signs of its base, is
23136 interpreted in the current radix. Thus, if the current radix is 16,
23137 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23140 @kindex set output-radix
23141 @item set output-radix @var{base}
23142 Set the default base for numeric display. Supported choices
23143 for @var{base} are decimal 8, 10, or 16. The base must itself be
23144 specified either unambiguously or using the current input radix.
23146 @kindex show input-radix
23147 @item show input-radix
23148 Display the current default base for numeric input.
23150 @kindex show output-radix
23151 @item show output-radix
23152 Display the current default base for numeric display.
23154 @item set radix @r{[}@var{base}@r{]}
23158 These commands set and show the default base for both input and output
23159 of numbers. @code{set radix} sets the radix of input and output to
23160 the same base; without an argument, it resets the radix back to its
23161 default value of 10.
23166 @section Configuring the Current ABI
23168 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23169 application automatically. However, sometimes you need to override its
23170 conclusions. Use these commands to manage @value{GDBN}'s view of the
23176 @cindex Newlib OS ABI and its influence on the longjmp handling
23178 One @value{GDBN} configuration can debug binaries for multiple operating
23179 system targets, either via remote debugging or native emulation.
23180 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23181 but you can override its conclusion using the @code{set osabi} command.
23182 One example where this is useful is in debugging of binaries which use
23183 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23184 not have the same identifying marks that the standard C library for your
23187 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23188 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23189 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23190 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23194 Show the OS ABI currently in use.
23197 With no argument, show the list of registered available OS ABI's.
23199 @item set osabi @var{abi}
23200 Set the current OS ABI to @var{abi}.
23203 @cindex float promotion
23205 Generally, the way that an argument of type @code{float} is passed to a
23206 function depends on whether the function is prototyped. For a prototyped
23207 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23208 according to the architecture's convention for @code{float}. For unprototyped
23209 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23210 @code{double} and then passed.
23212 Unfortunately, some forms of debug information do not reliably indicate whether
23213 a function is prototyped. If @value{GDBN} calls a function that is not marked
23214 as prototyped, it consults @kbd{set coerce-float-to-double}.
23217 @kindex set coerce-float-to-double
23218 @item set coerce-float-to-double
23219 @itemx set coerce-float-to-double on
23220 Arguments of type @code{float} will be promoted to @code{double} when passed
23221 to an unprototyped function. This is the default setting.
23223 @item set coerce-float-to-double off
23224 Arguments of type @code{float} will be passed directly to unprototyped
23227 @kindex show coerce-float-to-double
23228 @item show coerce-float-to-double
23229 Show the current setting of promoting @code{float} to @code{double}.
23233 @kindex show cp-abi
23234 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23235 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23236 used to build your application. @value{GDBN} only fully supports
23237 programs with a single C@t{++} ABI; if your program contains code using
23238 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23239 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23240 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23241 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23242 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23243 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23248 Show the C@t{++} ABI currently in use.
23251 With no argument, show the list of supported C@t{++} ABI's.
23253 @item set cp-abi @var{abi}
23254 @itemx set cp-abi auto
23255 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23259 @section Automatically loading associated files
23260 @cindex auto-loading
23262 @value{GDBN} sometimes reads files with commands and settings automatically,
23263 without being explicitly told so by the user. We call this feature
23264 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23265 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23266 results or introduce security risks (e.g., if the file comes from untrusted
23270 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23271 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23273 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23274 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23277 There are various kinds of files @value{GDBN} can automatically load.
23278 In addition to these files, @value{GDBN} supports auto-loading code written
23279 in various extension languages. @xref{Auto-loading extensions}.
23281 Note that loading of these associated files (including the local @file{.gdbinit}
23282 file) requires accordingly configured @code{auto-load safe-path}
23283 (@pxref{Auto-loading safe path}).
23285 For these reasons, @value{GDBN} includes commands and options to let you
23286 control when to auto-load files and which files should be auto-loaded.
23289 @anchor{set auto-load off}
23290 @kindex set auto-load off
23291 @item set auto-load off
23292 Globally disable loading of all auto-loaded files.
23293 You may want to use this command with the @samp{-iex} option
23294 (@pxref{Option -init-eval-command}) such as:
23296 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23299 Be aware that system init file (@pxref{System-wide configuration})
23300 and init files from your home directory (@pxref{Home Directory Init File})
23301 still get read (as they come from generally trusted directories).
23302 To prevent @value{GDBN} from auto-loading even those init files, use the
23303 @option{-nx} option (@pxref{Mode Options}), in addition to
23304 @code{set auto-load no}.
23306 @anchor{show auto-load}
23307 @kindex show auto-load
23308 @item show auto-load
23309 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23313 (gdb) show auto-load
23314 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23315 libthread-db: Auto-loading of inferior specific libthread_db is on.
23316 local-gdbinit: Auto-loading of .gdbinit script from current directory
23318 python-scripts: Auto-loading of Python scripts is on.
23319 safe-path: List of directories from which it is safe to auto-load files
23320 is $debugdir:$datadir/auto-load.
23321 scripts-directory: List of directories from which to load auto-loaded scripts
23322 is $debugdir:$datadir/auto-load.
23325 @anchor{info auto-load}
23326 @kindex info auto-load
23327 @item info auto-load
23328 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23332 (gdb) info auto-load
23335 Yes /home/user/gdb/gdb-gdb.gdb
23336 libthread-db: No auto-loaded libthread-db.
23337 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23341 Yes /home/user/gdb/gdb-gdb.py
23345 These are @value{GDBN} control commands for the auto-loading:
23347 @multitable @columnfractions .5 .5
23348 @item @xref{set auto-load off}.
23349 @tab Disable auto-loading globally.
23350 @item @xref{show auto-load}.
23351 @tab Show setting of all kinds of files.
23352 @item @xref{info auto-load}.
23353 @tab Show state of all kinds of files.
23354 @item @xref{set auto-load gdb-scripts}.
23355 @tab Control for @value{GDBN} command scripts.
23356 @item @xref{show auto-load gdb-scripts}.
23357 @tab Show setting of @value{GDBN} command scripts.
23358 @item @xref{info auto-load gdb-scripts}.
23359 @tab Show state of @value{GDBN} command scripts.
23360 @item @xref{set auto-load python-scripts}.
23361 @tab Control for @value{GDBN} Python scripts.
23362 @item @xref{show auto-load python-scripts}.
23363 @tab Show setting of @value{GDBN} Python scripts.
23364 @item @xref{info auto-load python-scripts}.
23365 @tab Show state of @value{GDBN} Python scripts.
23366 @item @xref{set auto-load guile-scripts}.
23367 @tab Control for @value{GDBN} Guile scripts.
23368 @item @xref{show auto-load guile-scripts}.
23369 @tab Show setting of @value{GDBN} Guile scripts.
23370 @item @xref{info auto-load guile-scripts}.
23371 @tab Show state of @value{GDBN} Guile scripts.
23372 @item @xref{set auto-load scripts-directory}.
23373 @tab Control for @value{GDBN} auto-loaded scripts location.
23374 @item @xref{show auto-load scripts-directory}.
23375 @tab Show @value{GDBN} auto-loaded scripts location.
23376 @item @xref{add-auto-load-scripts-directory}.
23377 @tab Add directory for auto-loaded scripts location list.
23378 @item @xref{set auto-load local-gdbinit}.
23379 @tab Control for init file in the current directory.
23380 @item @xref{show auto-load local-gdbinit}.
23381 @tab Show setting of init file in the current directory.
23382 @item @xref{info auto-load local-gdbinit}.
23383 @tab Show state of init file in the current directory.
23384 @item @xref{set auto-load libthread-db}.
23385 @tab Control for thread debugging library.
23386 @item @xref{show auto-load libthread-db}.
23387 @tab Show setting of thread debugging library.
23388 @item @xref{info auto-load libthread-db}.
23389 @tab Show state of thread debugging library.
23390 @item @xref{set auto-load safe-path}.
23391 @tab Control directories trusted for automatic loading.
23392 @item @xref{show auto-load safe-path}.
23393 @tab Show directories trusted for automatic loading.
23394 @item @xref{add-auto-load-safe-path}.
23395 @tab Add directory trusted for automatic loading.
23398 @node Init File in the Current Directory
23399 @subsection Automatically loading init file in the current directory
23400 @cindex auto-loading init file in the current directory
23402 By default, @value{GDBN} reads and executes the canned sequences of commands
23403 from init file (if any) in the current working directory,
23404 see @ref{Init File in the Current Directory during Startup}.
23406 Note that loading of this local @file{.gdbinit} file also requires accordingly
23407 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23410 @anchor{set auto-load local-gdbinit}
23411 @kindex set auto-load local-gdbinit
23412 @item set auto-load local-gdbinit [on|off]
23413 Enable or disable the auto-loading of canned sequences of commands
23414 (@pxref{Sequences}) found in init file in the current directory.
23416 @anchor{show auto-load local-gdbinit}
23417 @kindex show auto-load local-gdbinit
23418 @item show auto-load local-gdbinit
23419 Show whether auto-loading of canned sequences of commands from init file in the
23420 current directory is enabled or disabled.
23422 @anchor{info auto-load local-gdbinit}
23423 @kindex info auto-load local-gdbinit
23424 @item info auto-load local-gdbinit
23425 Print whether canned sequences of commands from init file in the
23426 current directory have been auto-loaded.
23429 @node libthread_db.so.1 file
23430 @subsection Automatically loading thread debugging library
23431 @cindex auto-loading libthread_db.so.1
23433 This feature is currently present only on @sc{gnu}/Linux native hosts.
23435 @value{GDBN} reads in some cases thread debugging library from places specific
23436 to the inferior (@pxref{set libthread-db-search-path}).
23438 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23439 without checking this @samp{set auto-load libthread-db} switch as system
23440 libraries have to be trusted in general. In all other cases of
23441 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23442 auto-load libthread-db} is enabled before trying to open such thread debugging
23445 Note that loading of this debugging library also requires accordingly configured
23446 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23449 @anchor{set auto-load libthread-db}
23450 @kindex set auto-load libthread-db
23451 @item set auto-load libthread-db [on|off]
23452 Enable or disable the auto-loading of inferior specific thread debugging library.
23454 @anchor{show auto-load libthread-db}
23455 @kindex show auto-load libthread-db
23456 @item show auto-load libthread-db
23457 Show whether auto-loading of inferior specific thread debugging library is
23458 enabled or disabled.
23460 @anchor{info auto-load libthread-db}
23461 @kindex info auto-load libthread-db
23462 @item info auto-load libthread-db
23463 Print the list of all loaded inferior specific thread debugging libraries and
23464 for each such library print list of inferior @var{pid}s using it.
23467 @node Auto-loading safe path
23468 @subsection Security restriction for auto-loading
23469 @cindex auto-loading safe-path
23471 As the files of inferior can come from untrusted source (such as submitted by
23472 an application user) @value{GDBN} does not always load any files automatically.
23473 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23474 directories trusted for loading files not explicitly requested by user.
23475 Each directory can also be a shell wildcard pattern.
23477 If the path is not set properly you will see a warning and the file will not
23482 Reading symbols from /home/user/gdb/gdb...done.
23483 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23484 declined by your `auto-load safe-path' set
23485 to "$debugdir:$datadir/auto-load".
23486 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23487 declined by your `auto-load safe-path' set
23488 to "$debugdir:$datadir/auto-load".
23492 To instruct @value{GDBN} to go ahead and use the init files anyway,
23493 invoke @value{GDBN} like this:
23496 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23499 The list of trusted directories is controlled by the following commands:
23502 @anchor{set auto-load safe-path}
23503 @kindex set auto-load safe-path
23504 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23505 Set the list of directories (and their subdirectories) trusted for automatic
23506 loading and execution of scripts. You can also enter a specific trusted file.
23507 Each directory can also be a shell wildcard pattern; wildcards do not match
23508 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23509 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23510 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23511 its default value as specified during @value{GDBN} compilation.
23513 The list of directories uses path separator (@samp{:} on GNU and Unix
23514 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23515 to the @env{PATH} environment variable.
23517 @anchor{show auto-load safe-path}
23518 @kindex show auto-load safe-path
23519 @item show auto-load safe-path
23520 Show the list of directories trusted for automatic loading and execution of
23523 @anchor{add-auto-load-safe-path}
23524 @kindex add-auto-load-safe-path
23525 @item add-auto-load-safe-path
23526 Add an entry (or list of entries) to the list of directories trusted for
23527 automatic loading and execution of scripts. Multiple entries may be delimited
23528 by the host platform path separator in use.
23531 This variable defaults to what @code{--with-auto-load-dir} has been configured
23532 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23533 substitution applies the same as for @ref{set auto-load scripts-directory}.
23534 The default @code{set auto-load safe-path} value can be also overriden by
23535 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23537 Setting this variable to @file{/} disables this security protection,
23538 corresponding @value{GDBN} configuration option is
23539 @option{--without-auto-load-safe-path}.
23540 This variable is supposed to be set to the system directories writable by the
23541 system superuser only. Users can add their source directories in init files in
23542 their home directories (@pxref{Home Directory Init File}). See also deprecated
23543 init file in the current directory
23544 (@pxref{Init File in the Current Directory during Startup}).
23546 To force @value{GDBN} to load the files it declined to load in the previous
23547 example, you could use one of the following ways:
23550 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23551 Specify this trusted directory (or a file) as additional component of the list.
23552 You have to specify also any existing directories displayed by
23553 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23555 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23556 Specify this directory as in the previous case but just for a single
23557 @value{GDBN} session.
23559 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23560 Disable auto-loading safety for a single @value{GDBN} session.
23561 This assumes all the files you debug during this @value{GDBN} session will come
23562 from trusted sources.
23564 @item @kbd{./configure --without-auto-load-safe-path}
23565 During compilation of @value{GDBN} you may disable any auto-loading safety.
23566 This assumes all the files you will ever debug with this @value{GDBN} come from
23570 On the other hand you can also explicitly forbid automatic files loading which
23571 also suppresses any such warning messages:
23574 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23575 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23577 @item @file{~/.gdbinit}: @samp{set auto-load no}
23578 Disable auto-loading globally for the user
23579 (@pxref{Home Directory Init File}). While it is improbable, you could also
23580 use system init file instead (@pxref{System-wide configuration}).
23583 This setting applies to the file names as entered by user. If no entry matches
23584 @value{GDBN} tries as a last resort to also resolve all the file names into
23585 their canonical form (typically resolving symbolic links) and compare the
23586 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23587 own before starting the comparison so a canonical form of directories is
23588 recommended to be entered.
23590 @node Auto-loading verbose mode
23591 @subsection Displaying files tried for auto-load
23592 @cindex auto-loading verbose mode
23594 For better visibility of all the file locations where you can place scripts to
23595 be auto-loaded with inferior --- or to protect yourself against accidental
23596 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23597 all the files attempted to be loaded. Both existing and non-existing files may
23600 For example the list of directories from which it is safe to auto-load files
23601 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23602 may not be too obvious while setting it up.
23605 (gdb) set debug auto-load on
23606 (gdb) file ~/src/t/true
23607 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23608 for objfile "/tmp/true".
23609 auto-load: Updating directories of "/usr:/opt".
23610 auto-load: Using directory "/usr".
23611 auto-load: Using directory "/opt".
23612 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23613 by your `auto-load safe-path' set to "/usr:/opt".
23617 @anchor{set debug auto-load}
23618 @kindex set debug auto-load
23619 @item set debug auto-load [on|off]
23620 Set whether to print the filenames attempted to be auto-loaded.
23622 @anchor{show debug auto-load}
23623 @kindex show debug auto-load
23624 @item show debug auto-load
23625 Show whether printing of the filenames attempted to be auto-loaded is turned
23629 @node Messages/Warnings
23630 @section Optional Warnings and Messages
23632 @cindex verbose operation
23633 @cindex optional warnings
23634 By default, @value{GDBN} is silent about its inner workings. If you are
23635 running on a slow machine, you may want to use the @code{set verbose}
23636 command. This makes @value{GDBN} tell you when it does a lengthy
23637 internal operation, so you will not think it has crashed.
23639 Currently, the messages controlled by @code{set verbose} are those
23640 which announce that the symbol table for a source file is being read;
23641 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23644 @kindex set verbose
23645 @item set verbose on
23646 Enables @value{GDBN} output of certain informational messages.
23648 @item set verbose off
23649 Disables @value{GDBN} output of certain informational messages.
23651 @kindex show verbose
23653 Displays whether @code{set verbose} is on or off.
23656 By default, if @value{GDBN} encounters bugs in the symbol table of an
23657 object file, it is silent; but if you are debugging a compiler, you may
23658 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23663 @kindex set complaints
23664 @item set complaints @var{limit}
23665 Permits @value{GDBN} to output @var{limit} complaints about each type of
23666 unusual symbols before becoming silent about the problem. Set
23667 @var{limit} to zero to suppress all complaints; set it to a large number
23668 to prevent complaints from being suppressed.
23670 @kindex show complaints
23671 @item show complaints
23672 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23676 @anchor{confirmation requests}
23677 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23678 lot of stupid questions to confirm certain commands. For example, if
23679 you try to run a program which is already running:
23683 The program being debugged has been started already.
23684 Start it from the beginning? (y or n)
23687 If you are willing to unflinchingly face the consequences of your own
23688 commands, you can disable this ``feature'':
23692 @kindex set confirm
23694 @cindex confirmation
23695 @cindex stupid questions
23696 @item set confirm off
23697 Disables confirmation requests. Note that running @value{GDBN} with
23698 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23699 automatically disables confirmation requests.
23701 @item set confirm on
23702 Enables confirmation requests (the default).
23704 @kindex show confirm
23706 Displays state of confirmation requests.
23710 @cindex command tracing
23711 If you need to debug user-defined commands or sourced files you may find it
23712 useful to enable @dfn{command tracing}. In this mode each command will be
23713 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23714 quantity denoting the call depth of each command.
23717 @kindex set trace-commands
23718 @cindex command scripts, debugging
23719 @item set trace-commands on
23720 Enable command tracing.
23721 @item set trace-commands off
23722 Disable command tracing.
23723 @item show trace-commands
23724 Display the current state of command tracing.
23727 @node Debugging Output
23728 @section Optional Messages about Internal Happenings
23729 @cindex optional debugging messages
23731 @value{GDBN} has commands that enable optional debugging messages from
23732 various @value{GDBN} subsystems; normally these commands are of
23733 interest to @value{GDBN} maintainers, or when reporting a bug. This
23734 section documents those commands.
23737 @kindex set exec-done-display
23738 @item set exec-done-display
23739 Turns on or off the notification of asynchronous commands'
23740 completion. When on, @value{GDBN} will print a message when an
23741 asynchronous command finishes its execution. The default is off.
23742 @kindex show exec-done-display
23743 @item show exec-done-display
23744 Displays the current setting of asynchronous command completion
23747 @cindex ARM AArch64
23748 @item set debug aarch64
23749 Turns on or off display of debugging messages related to ARM AArch64.
23750 The default is off.
23752 @item show debug aarch64
23753 Displays the current state of displaying debugging messages related to
23755 @cindex gdbarch debugging info
23756 @cindex architecture debugging info
23757 @item set debug arch
23758 Turns on or off display of gdbarch debugging info. The default is off
23759 @item show debug arch
23760 Displays the current state of displaying gdbarch debugging info.
23761 @item set debug aix-solib
23762 @cindex AIX shared library debugging
23763 Control display of debugging messages from the AIX shared library
23764 support module. The default is off.
23765 @item show debug aix-thread
23766 Show the current state of displaying AIX shared library debugging messages.
23767 @item set debug aix-thread
23768 @cindex AIX threads
23769 Display debugging messages about inner workings of the AIX thread
23771 @item show debug aix-thread
23772 Show the current state of AIX thread debugging info display.
23773 @item set debug check-physname
23775 Check the results of the ``physname'' computation. When reading DWARF
23776 debugging information for C@t{++}, @value{GDBN} attempts to compute
23777 each entity's name. @value{GDBN} can do this computation in two
23778 different ways, depending on exactly what information is present.
23779 When enabled, this setting causes @value{GDBN} to compute the names
23780 both ways and display any discrepancies.
23781 @item show debug check-physname
23782 Show the current state of ``physname'' checking.
23783 @item set debug coff-pe-read
23784 @cindex COFF/PE exported symbols
23785 Control display of debugging messages related to reading of COFF/PE
23786 exported symbols. The default is off.
23787 @item show debug coff-pe-read
23788 Displays the current state of displaying debugging messages related to
23789 reading of COFF/PE exported symbols.
23790 @item set debug dwarf-die
23792 Dump DWARF DIEs after they are read in.
23793 The value is the number of nesting levels to print.
23794 A value of zero turns off the display.
23795 @item show debug dwarf-die
23796 Show the current state of DWARF DIE debugging.
23797 @item set debug dwarf-line
23798 @cindex DWARF Line Tables
23799 Turns on or off display of debugging messages related to reading
23800 DWARF line tables. The default is 0 (off).
23801 A value of 1 provides basic information.
23802 A value greater than 1 provides more verbose information.
23803 @item show debug dwarf-line
23804 Show the current state of DWARF line table debugging.
23805 @item set debug dwarf-read
23806 @cindex DWARF Reading
23807 Turns on or off display of debugging messages related to reading
23808 DWARF debug info. The default is 0 (off).
23809 A value of 1 provides basic information.
23810 A value greater than 1 provides more verbose information.
23811 @item show debug dwarf-read
23812 Show the current state of DWARF reader debugging.
23813 @item set debug displaced
23814 @cindex displaced stepping debugging info
23815 Turns on or off display of @value{GDBN} debugging info for the
23816 displaced stepping support. The default is off.
23817 @item show debug displaced
23818 Displays the current state of displaying @value{GDBN} debugging info
23819 related to displaced stepping.
23820 @item set debug event
23821 @cindex event debugging info
23822 Turns on or off display of @value{GDBN} event debugging info. The
23824 @item show debug event
23825 Displays the current state of displaying @value{GDBN} event debugging
23827 @item set debug expression
23828 @cindex expression debugging info
23829 Turns on or off display of debugging info about @value{GDBN}
23830 expression parsing. The default is off.
23831 @item show debug expression
23832 Displays the current state of displaying debugging info about
23833 @value{GDBN} expression parsing.
23834 @item set debug fbsd-lwp
23835 @cindex FreeBSD LWP debug messages
23836 Turns on or off debugging messages from the FreeBSD LWP debug support.
23837 @item show debug fbsd-lwp
23838 Show the current state of FreeBSD LWP debugging messages.
23839 @item set debug frame
23840 @cindex frame debugging info
23841 Turns on or off display of @value{GDBN} frame debugging info. The
23843 @item show debug frame
23844 Displays the current state of displaying @value{GDBN} frame debugging
23846 @item set debug gnu-nat
23847 @cindex @sc{gnu}/Hurd debug messages
23848 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
23849 @item show debug gnu-nat
23850 Show the current state of @sc{gnu}/Hurd debugging messages.
23851 @item set debug infrun
23852 @cindex inferior debugging info
23853 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23854 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23855 for implementing operations such as single-stepping the inferior.
23856 @item show debug infrun
23857 Displays the current state of @value{GDBN} inferior debugging.
23858 @item set debug jit
23859 @cindex just-in-time compilation, debugging messages
23860 Turn on or off debugging messages from JIT debug support.
23861 @item show debug jit
23862 Displays the current state of @value{GDBN} JIT debugging.
23863 @item set debug lin-lwp
23864 @cindex @sc{gnu}/Linux LWP debug messages
23865 @cindex Linux lightweight processes
23866 Turn on or off debugging messages from the Linux LWP debug support.
23867 @item show debug lin-lwp
23868 Show the current state of Linux LWP debugging messages.
23869 @item set debug linux-namespaces
23870 @cindex @sc{gnu}/Linux namespaces debug messages
23871 Turn on or off debugging messages from the Linux namespaces debug support.
23872 @item show debug linux-namespaces
23873 Show the current state of Linux namespaces debugging messages.
23874 @item set debug mach-o
23875 @cindex Mach-O symbols processing
23876 Control display of debugging messages related to Mach-O symbols
23877 processing. The default is off.
23878 @item show debug mach-o
23879 Displays the current state of displaying debugging messages related to
23880 reading of COFF/PE exported symbols.
23881 @item set debug notification
23882 @cindex remote async notification debugging info
23883 Turn on or off debugging messages about remote async notification.
23884 The default is off.
23885 @item show debug notification
23886 Displays the current state of remote async notification debugging messages.
23887 @item set debug observer
23888 @cindex observer debugging info
23889 Turns on or off display of @value{GDBN} observer debugging. This
23890 includes info such as the notification of observable events.
23891 @item show debug observer
23892 Displays the current state of observer debugging.
23893 @item set debug overload
23894 @cindex C@t{++} overload debugging info
23895 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23896 info. This includes info such as ranking of functions, etc. The default
23898 @item show debug overload
23899 Displays the current state of displaying @value{GDBN} C@t{++} overload
23901 @cindex expression parser, debugging info
23902 @cindex debug expression parser
23903 @item set debug parser
23904 Turns on or off the display of expression parser debugging output.
23905 Internally, this sets the @code{yydebug} variable in the expression
23906 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23907 details. The default is off.
23908 @item show debug parser
23909 Show the current state of expression parser debugging.
23910 @cindex packets, reporting on stdout
23911 @cindex serial connections, debugging
23912 @cindex debug remote protocol
23913 @cindex remote protocol debugging
23914 @cindex display remote packets
23915 @item set debug remote
23916 Turns on or off display of reports on all packets sent back and forth across
23917 the serial line to the remote machine. The info is printed on the
23918 @value{GDBN} standard output stream. The default is off.
23919 @item show debug remote
23920 Displays the state of display of remote packets.
23921 @item set debug serial
23922 Turns on or off display of @value{GDBN} serial debugging info. The
23924 @item show debug serial
23925 Displays the current state of displaying @value{GDBN} serial debugging
23927 @item set debug solib-frv
23928 @cindex FR-V shared-library debugging
23929 Turn on or off debugging messages for FR-V shared-library code.
23930 @item show debug solib-frv
23931 Display the current state of FR-V shared-library code debugging
23933 @item set debug symbol-lookup
23934 @cindex symbol lookup
23935 Turns on or off display of debugging messages related to symbol lookup.
23936 The default is 0 (off).
23937 A value of 1 provides basic information.
23938 A value greater than 1 provides more verbose information.
23939 @item show debug symbol-lookup
23940 Show the current state of symbol lookup debugging messages.
23941 @item set debug symfile
23942 @cindex symbol file functions
23943 Turns on or off display of debugging messages related to symbol file functions.
23944 The default is off. @xref{Files}.
23945 @item show debug symfile
23946 Show the current state of symbol file debugging messages.
23947 @item set debug symtab-create
23948 @cindex symbol table creation
23949 Turns on or off display of debugging messages related to symbol table creation.
23950 The default is 0 (off).
23951 A value of 1 provides basic information.
23952 A value greater than 1 provides more verbose information.
23953 @item show debug symtab-create
23954 Show the current state of symbol table creation debugging.
23955 @item set debug target
23956 @cindex target debugging info
23957 Turns on or off display of @value{GDBN} target debugging info. This info
23958 includes what is going on at the target level of GDB, as it happens. The
23959 default is 0. Set it to 1 to track events, and to 2 to also track the
23960 value of large memory transfers.
23961 @item show debug target
23962 Displays the current state of displaying @value{GDBN} target debugging
23964 @item set debug timestamp
23965 @cindex timestampping debugging info
23966 Turns on or off display of timestamps with @value{GDBN} debugging info.
23967 When enabled, seconds and microseconds are displayed before each debugging
23969 @item show debug timestamp
23970 Displays the current state of displaying timestamps with @value{GDBN}
23972 @item set debug varobj
23973 @cindex variable object debugging info
23974 Turns on or off display of @value{GDBN} variable object debugging
23975 info. The default is off.
23976 @item show debug varobj
23977 Displays the current state of displaying @value{GDBN} variable object
23979 @item set debug xml
23980 @cindex XML parser debugging
23981 Turn on or off debugging messages for built-in XML parsers.
23982 @item show debug xml
23983 Displays the current state of XML debugging messages.
23986 @node Other Misc Settings
23987 @section Other Miscellaneous Settings
23988 @cindex miscellaneous settings
23991 @kindex set interactive-mode
23992 @item set interactive-mode
23993 If @code{on}, forces @value{GDBN} to assume that GDB was started
23994 in a terminal. In practice, this means that @value{GDBN} should wait
23995 for the user to answer queries generated by commands entered at
23996 the command prompt. If @code{off}, forces @value{GDBN} to operate
23997 in the opposite mode, and it uses the default answers to all queries.
23998 If @code{auto} (the default), @value{GDBN} tries to determine whether
23999 its standard input is a terminal, and works in interactive-mode if it
24000 is, non-interactively otherwise.
24002 In the vast majority of cases, the debugger should be able to guess
24003 correctly which mode should be used. But this setting can be useful
24004 in certain specific cases, such as running a MinGW @value{GDBN}
24005 inside a cygwin window.
24007 @kindex show interactive-mode
24008 @item show interactive-mode
24009 Displays whether the debugger is operating in interactive mode or not.
24012 @node Extending GDB
24013 @chapter Extending @value{GDBN}
24014 @cindex extending GDB
24016 @value{GDBN} provides several mechanisms for extension.
24017 @value{GDBN} also provides the ability to automatically load
24018 extensions when it reads a file for debugging. This allows the
24019 user to automatically customize @value{GDBN} for the program
24023 * Sequences:: Canned Sequences of @value{GDBN} Commands
24024 * Python:: Extending @value{GDBN} using Python
24025 * Guile:: Extending @value{GDBN} using Guile
24026 * Auto-loading extensions:: Automatically loading extensions
24027 * Multiple Extension Languages:: Working with multiple extension languages
24028 * Aliases:: Creating new spellings of existing commands
24031 To facilitate the use of extension languages, @value{GDBN} is capable
24032 of evaluating the contents of a file. When doing so, @value{GDBN}
24033 can recognize which extension language is being used by looking at
24034 the filename extension. Files with an unrecognized filename extension
24035 are always treated as a @value{GDBN} Command Files.
24036 @xref{Command Files,, Command files}.
24038 You can control how @value{GDBN} evaluates these files with the following
24042 @kindex set script-extension
24043 @kindex show script-extension
24044 @item set script-extension off
24045 All scripts are always evaluated as @value{GDBN} Command Files.
24047 @item set script-extension soft
24048 The debugger determines the scripting language based on filename
24049 extension. If this scripting language is supported, @value{GDBN}
24050 evaluates the script using that language. Otherwise, it evaluates
24051 the file as a @value{GDBN} Command File.
24053 @item set script-extension strict
24054 The debugger determines the scripting language based on filename
24055 extension, and evaluates the script using that language. If the
24056 language is not supported, then the evaluation fails.
24058 @item show script-extension
24059 Display the current value of the @code{script-extension} option.
24064 @section Canned Sequences of Commands
24066 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24067 Command Lists}), @value{GDBN} provides two ways to store sequences of
24068 commands for execution as a unit: user-defined commands and command
24072 * Define:: How to define your own commands
24073 * Hooks:: Hooks for user-defined commands
24074 * Command Files:: How to write scripts of commands to be stored in a file
24075 * Output:: Commands for controlled output
24076 * Auto-loading sequences:: Controlling auto-loaded command files
24080 @subsection User-defined Commands
24082 @cindex user-defined command
24083 @cindex arguments, to user-defined commands
24084 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24085 which you assign a new name as a command. This is done with the
24086 @code{define} command. User commands may accept an unlimited number of arguments
24087 separated by whitespace. Arguments are accessed within the user command
24088 via @code{$arg0@dots{}$argN}. A trivial example:
24092 print $arg0 + $arg1 + $arg2
24097 To execute the command use:
24104 This defines the command @code{adder}, which prints the sum of
24105 its three arguments. Note the arguments are text substitutions, so they may
24106 reference variables, use complex expressions, or even perform inferior
24109 @cindex argument count in user-defined commands
24110 @cindex how many arguments (user-defined commands)
24111 In addition, @code{$argc} may be used to find out how many arguments have
24117 print $arg0 + $arg1
24120 print $arg0 + $arg1 + $arg2
24125 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24126 to process a variable number of arguments:
24133 eval "set $sum = $sum + $arg%d", $i
24143 @item define @var{commandname}
24144 Define a command named @var{commandname}. If there is already a command
24145 by that name, you are asked to confirm that you want to redefine it.
24146 The argument @var{commandname} may be a bare command name consisting of letters,
24147 numbers, dashes, and underscores. It may also start with any predefined
24148 prefix command. For example, @samp{define target my-target} creates
24149 a user-defined @samp{target my-target} command.
24151 The definition of the command is made up of other @value{GDBN} command lines,
24152 which are given following the @code{define} command. The end of these
24153 commands is marked by a line containing @code{end}.
24156 @kindex end@r{ (user-defined commands)}
24157 @item document @var{commandname}
24158 Document the user-defined command @var{commandname}, so that it can be
24159 accessed by @code{help}. The command @var{commandname} must already be
24160 defined. This command reads lines of documentation just as @code{define}
24161 reads the lines of the command definition, ending with @code{end}.
24162 After the @code{document} command is finished, @code{help} on command
24163 @var{commandname} displays the documentation you have written.
24165 You may use the @code{document} command again to change the
24166 documentation of a command. Redefining the command with @code{define}
24167 does not change the documentation.
24169 @kindex dont-repeat
24170 @cindex don't repeat command
24172 Used inside a user-defined command, this tells @value{GDBN} that this
24173 command should not be repeated when the user hits @key{RET}
24174 (@pxref{Command Syntax, repeat last command}).
24176 @kindex help user-defined
24177 @item help user-defined
24178 List all user-defined commands and all python commands defined in class
24179 COMAND_USER. The first line of the documentation or docstring is
24184 @itemx show user @var{commandname}
24185 Display the @value{GDBN} commands used to define @var{commandname} (but
24186 not its documentation). If no @var{commandname} is given, display the
24187 definitions for all user-defined commands.
24188 This does not work for user-defined python commands.
24190 @cindex infinite recursion in user-defined commands
24191 @kindex show max-user-call-depth
24192 @kindex set max-user-call-depth
24193 @item show max-user-call-depth
24194 @itemx set max-user-call-depth
24195 The value of @code{max-user-call-depth} controls how many recursion
24196 levels are allowed in user-defined commands before @value{GDBN} suspects an
24197 infinite recursion and aborts the command.
24198 This does not apply to user-defined python commands.
24201 In addition to the above commands, user-defined commands frequently
24202 use control flow commands, described in @ref{Command Files}.
24204 When user-defined commands are executed, the
24205 commands of the definition are not printed. An error in any command
24206 stops execution of the user-defined command.
24208 If used interactively, commands that would ask for confirmation proceed
24209 without asking when used inside a user-defined command. Many @value{GDBN}
24210 commands that normally print messages to say what they are doing omit the
24211 messages when used in a user-defined command.
24214 @subsection User-defined Command Hooks
24215 @cindex command hooks
24216 @cindex hooks, for commands
24217 @cindex hooks, pre-command
24220 You may define @dfn{hooks}, which are a special kind of user-defined
24221 command. Whenever you run the command @samp{foo}, if the user-defined
24222 command @samp{hook-foo} exists, it is executed (with no arguments)
24223 before that command.
24225 @cindex hooks, post-command
24227 A hook may also be defined which is run after the command you executed.
24228 Whenever you run the command @samp{foo}, if the user-defined command
24229 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24230 that command. Post-execution hooks may exist simultaneously with
24231 pre-execution hooks, for the same command.
24233 It is valid for a hook to call the command which it hooks. If this
24234 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24236 @c It would be nice if hookpost could be passed a parameter indicating
24237 @c if the command it hooks executed properly or not. FIXME!
24239 @kindex stop@r{, a pseudo-command}
24240 In addition, a pseudo-command, @samp{stop} exists. Defining
24241 (@samp{hook-stop}) makes the associated commands execute every time
24242 execution stops in your program: before breakpoint commands are run,
24243 displays are printed, or the stack frame is printed.
24245 For example, to ignore @code{SIGALRM} signals while
24246 single-stepping, but treat them normally during normal execution,
24251 handle SIGALRM nopass
24255 handle SIGALRM pass
24258 define hook-continue
24259 handle SIGALRM pass
24263 As a further example, to hook at the beginning and end of the @code{echo}
24264 command, and to add extra text to the beginning and end of the message,
24272 define hookpost-echo
24276 (@value{GDBP}) echo Hello World
24277 <<<---Hello World--->>>
24282 You can define a hook for any single-word command in @value{GDBN}, but
24283 not for command aliases; you should define a hook for the basic command
24284 name, e.g.@: @code{backtrace} rather than @code{bt}.
24285 @c FIXME! So how does Joe User discover whether a command is an alias
24287 You can hook a multi-word command by adding @code{hook-} or
24288 @code{hookpost-} to the last word of the command, e.g.@:
24289 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24291 If an error occurs during the execution of your hook, execution of
24292 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24293 (before the command that you actually typed had a chance to run).
24295 If you try to define a hook which does not match any known command, you
24296 get a warning from the @code{define} command.
24298 @node Command Files
24299 @subsection Command Files
24301 @cindex command files
24302 @cindex scripting commands
24303 A command file for @value{GDBN} is a text file made of lines that are
24304 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24305 also be included. An empty line in a command file does nothing; it
24306 does not mean to repeat the last command, as it would from the
24309 You can request the execution of a command file with the @code{source}
24310 command. Note that the @code{source} command is also used to evaluate
24311 scripts that are not Command Files. The exact behavior can be configured
24312 using the @code{script-extension} setting.
24313 @xref{Extending GDB,, Extending GDB}.
24317 @cindex execute commands from a file
24318 @item source [-s] [-v] @var{filename}
24319 Execute the command file @var{filename}.
24322 The lines in a command file are generally executed sequentially,
24323 unless the order of execution is changed by one of the
24324 @emph{flow-control commands} described below. The commands are not
24325 printed as they are executed. An error in any command terminates
24326 execution of the command file and control is returned to the console.
24328 @value{GDBN} first searches for @var{filename} in the current directory.
24329 If the file is not found there, and @var{filename} does not specify a
24330 directory, then @value{GDBN} also looks for the file on the source search path
24331 (specified with the @samp{directory} command);
24332 except that @file{$cdir} is not searched because the compilation directory
24333 is not relevant to scripts.
24335 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24336 on the search path even if @var{filename} specifies a directory.
24337 The search is done by appending @var{filename} to each element of the
24338 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24339 and the search path contains @file{/home/user} then @value{GDBN} will
24340 look for the script @file{/home/user/mylib/myscript}.
24341 The search is also done if @var{filename} is an absolute path.
24342 For example, if @var{filename} is @file{/tmp/myscript} and
24343 the search path contains @file{/home/user} then @value{GDBN} will
24344 look for the script @file{/home/user/tmp/myscript}.
24345 For DOS-like systems, if @var{filename} contains a drive specification,
24346 it is stripped before concatenation. For example, if @var{filename} is
24347 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24348 will look for the script @file{c:/tmp/myscript}.
24350 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24351 each command as it is executed. The option must be given before
24352 @var{filename}, and is interpreted as part of the filename anywhere else.
24354 Commands that would ask for confirmation if used interactively proceed
24355 without asking when used in a command file. Many @value{GDBN} commands that
24356 normally print messages to say what they are doing omit the messages
24357 when called from command files.
24359 @value{GDBN} also accepts command input from standard input. In this
24360 mode, normal output goes to standard output and error output goes to
24361 standard error. Errors in a command file supplied on standard input do
24362 not terminate execution of the command file---execution continues with
24366 gdb < cmds > log 2>&1
24369 (The syntax above will vary depending on the shell used.) This example
24370 will execute commands from the file @file{cmds}. All output and errors
24371 would be directed to @file{log}.
24373 Since commands stored on command files tend to be more general than
24374 commands typed interactively, they frequently need to deal with
24375 complicated situations, such as different or unexpected values of
24376 variables and symbols, changes in how the program being debugged is
24377 built, etc. @value{GDBN} provides a set of flow-control commands to
24378 deal with these complexities. Using these commands, you can write
24379 complex scripts that loop over data structures, execute commands
24380 conditionally, etc.
24387 This command allows to include in your script conditionally executed
24388 commands. The @code{if} command takes a single argument, which is an
24389 expression to evaluate. It is followed by a series of commands that
24390 are executed only if the expression is true (its value is nonzero).
24391 There can then optionally be an @code{else} line, followed by a series
24392 of commands that are only executed if the expression was false. The
24393 end of the list is marked by a line containing @code{end}.
24397 This command allows to write loops. Its syntax is similar to
24398 @code{if}: the command takes a single argument, which is an expression
24399 to evaluate, and must be followed by the commands to execute, one per
24400 line, terminated by an @code{end}. These commands are called the
24401 @dfn{body} of the loop. The commands in the body of @code{while} are
24402 executed repeatedly as long as the expression evaluates to true.
24406 This command exits the @code{while} loop in whose body it is included.
24407 Execution of the script continues after that @code{while}s @code{end}
24410 @kindex loop_continue
24411 @item loop_continue
24412 This command skips the execution of the rest of the body of commands
24413 in the @code{while} loop in whose body it is included. Execution
24414 branches to the beginning of the @code{while} loop, where it evaluates
24415 the controlling expression.
24417 @kindex end@r{ (if/else/while commands)}
24419 Terminate the block of commands that are the body of @code{if},
24420 @code{else}, or @code{while} flow-control commands.
24425 @subsection Commands for Controlled Output
24427 During the execution of a command file or a user-defined command, normal
24428 @value{GDBN} output is suppressed; the only output that appears is what is
24429 explicitly printed by the commands in the definition. This section
24430 describes three commands useful for generating exactly the output you
24435 @item echo @var{text}
24436 @c I do not consider backslash-space a standard C escape sequence
24437 @c because it is not in ANSI.
24438 Print @var{text}. Nonprinting characters can be included in
24439 @var{text} using C escape sequences, such as @samp{\n} to print a
24440 newline. @strong{No newline is printed unless you specify one.}
24441 In addition to the standard C escape sequences, a backslash followed
24442 by a space stands for a space. This is useful for displaying a
24443 string with spaces at the beginning or the end, since leading and
24444 trailing spaces are otherwise trimmed from all arguments.
24445 To print @samp{@w{ }and foo =@w{ }}, use the command
24446 @samp{echo \@w{ }and foo = \@w{ }}.
24448 A backslash at the end of @var{text} can be used, as in C, to continue
24449 the command onto subsequent lines. For example,
24452 echo This is some text\n\
24453 which is continued\n\
24454 onto several lines.\n
24457 produces the same output as
24460 echo This is some text\n
24461 echo which is continued\n
24462 echo onto several lines.\n
24466 @item output @var{expression}
24467 Print the value of @var{expression} and nothing but that value: no
24468 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24469 value history either. @xref{Expressions, ,Expressions}, for more information
24472 @item output/@var{fmt} @var{expression}
24473 Print the value of @var{expression} in format @var{fmt}. You can use
24474 the same formats as for @code{print}. @xref{Output Formats,,Output
24475 Formats}, for more information.
24478 @item printf @var{template}, @var{expressions}@dots{}
24479 Print the values of one or more @var{expressions} under the control of
24480 the string @var{template}. To print several values, make
24481 @var{expressions} be a comma-separated list of individual expressions,
24482 which may be either numbers or pointers. Their values are printed as
24483 specified by @var{template}, exactly as a C program would do by
24484 executing the code below:
24487 printf (@var{template}, @var{expressions}@dots{});
24490 As in @code{C} @code{printf}, ordinary characters in @var{template}
24491 are printed verbatim, while @dfn{conversion specification} introduced
24492 by the @samp{%} character cause subsequent @var{expressions} to be
24493 evaluated, their values converted and formatted according to type and
24494 style information encoded in the conversion specifications, and then
24497 For example, you can print two values in hex like this:
24500 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24503 @code{printf} supports all the standard @code{C} conversion
24504 specifications, including the flags and modifiers between the @samp{%}
24505 character and the conversion letter, with the following exceptions:
24509 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24512 The modifier @samp{*} is not supported for specifying precision or
24516 The @samp{'} flag (for separation of digits into groups according to
24517 @code{LC_NUMERIC'}) is not supported.
24520 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24524 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24527 The conversion letters @samp{a} and @samp{A} are not supported.
24531 Note that the @samp{ll} type modifier is supported only if the
24532 underlying @code{C} implementation used to build @value{GDBN} supports
24533 the @code{long long int} type, and the @samp{L} type modifier is
24534 supported only if @code{long double} type is available.
24536 As in @code{C}, @code{printf} supports simple backslash-escape
24537 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24538 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24539 single character. Octal and hexadecimal escape sequences are not
24542 Additionally, @code{printf} supports conversion specifications for DFP
24543 (@dfn{Decimal Floating Point}) types using the following length modifiers
24544 together with a floating point specifier.
24549 @samp{H} for printing @code{Decimal32} types.
24552 @samp{D} for printing @code{Decimal64} types.
24555 @samp{DD} for printing @code{Decimal128} types.
24558 If the underlying @code{C} implementation used to build @value{GDBN} has
24559 support for the three length modifiers for DFP types, other modifiers
24560 such as width and precision will also be available for @value{GDBN} to use.
24562 In case there is no such @code{C} support, no additional modifiers will be
24563 available and the value will be printed in the standard way.
24565 Here's an example of printing DFP types using the above conversion letters:
24567 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24572 @item eval @var{template}, @var{expressions}@dots{}
24573 Convert the values of one or more @var{expressions} under the control of
24574 the string @var{template} to a command line, and call it.
24578 @node Auto-loading sequences
24579 @subsection Controlling auto-loading native @value{GDBN} scripts
24580 @cindex native script auto-loading
24582 When a new object file is read (for example, due to the @code{file}
24583 command, or because the inferior has loaded a shared library),
24584 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24585 @xref{Auto-loading extensions}.
24587 Auto-loading can be enabled or disabled,
24588 and the list of auto-loaded scripts can be printed.
24591 @anchor{set auto-load gdb-scripts}
24592 @kindex set auto-load gdb-scripts
24593 @item set auto-load gdb-scripts [on|off]
24594 Enable or disable the auto-loading of canned sequences of commands scripts.
24596 @anchor{show auto-load gdb-scripts}
24597 @kindex show auto-load gdb-scripts
24598 @item show auto-load gdb-scripts
24599 Show whether auto-loading of canned sequences of commands scripts is enabled or
24602 @anchor{info auto-load gdb-scripts}
24603 @kindex info auto-load gdb-scripts
24604 @cindex print list of auto-loaded canned sequences of commands scripts
24605 @item info auto-load gdb-scripts [@var{regexp}]
24606 Print the list of all canned sequences of commands scripts that @value{GDBN}
24610 If @var{regexp} is supplied only canned sequences of commands scripts with
24611 matching names are printed.
24613 @c Python docs live in a separate file.
24614 @include python.texi
24616 @c Guile docs live in a separate file.
24617 @include guile.texi
24619 @node Auto-loading extensions
24620 @section Auto-loading extensions
24621 @cindex auto-loading extensions
24623 @value{GDBN} provides two mechanisms for automatically loading extensions
24624 when a new object file is read (for example, due to the @code{file}
24625 command, or because the inferior has loaded a shared library):
24626 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24627 section of modern file formats like ELF.
24630 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24631 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24632 * Which flavor to choose?::
24635 The auto-loading feature is useful for supplying application-specific
24636 debugging commands and features.
24638 Auto-loading can be enabled or disabled,
24639 and the list of auto-loaded scripts can be printed.
24640 See the @samp{auto-loading} section of each extension language
24641 for more information.
24642 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24643 For Python files see @ref{Python Auto-loading}.
24645 Note that loading of this script file also requires accordingly configured
24646 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24648 @node objfile-gdbdotext file
24649 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24650 @cindex @file{@var{objfile}-gdb.gdb}
24651 @cindex @file{@var{objfile}-gdb.py}
24652 @cindex @file{@var{objfile}-gdb.scm}
24654 When a new object file is read, @value{GDBN} looks for a file named
24655 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24656 where @var{objfile} is the object file's name and
24657 where @var{ext} is the file extension for the extension language:
24660 @item @file{@var{objfile}-gdb.gdb}
24661 GDB's own command language
24662 @item @file{@var{objfile}-gdb.py}
24664 @item @file{@var{objfile}-gdb.scm}
24668 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24669 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24670 components, and appending the @file{-gdb.@var{ext}} suffix.
24671 If this file exists and is readable, @value{GDBN} will evaluate it as a
24672 script in the specified extension language.
24674 If this file does not exist, then @value{GDBN} will look for
24675 @var{script-name} file in all of the directories as specified below.
24677 Note that loading of these files requires an accordingly configured
24678 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24680 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24681 scripts normally according to its @file{.exe} filename. But if no scripts are
24682 found @value{GDBN} also tries script filenames matching the object file without
24683 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24684 is attempted on any platform. This makes the script filenames compatible
24685 between Unix and MS-Windows hosts.
24688 @anchor{set auto-load scripts-directory}
24689 @kindex set auto-load scripts-directory
24690 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24691 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24692 may be delimited by the host platform path separator in use
24693 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24695 Each entry here needs to be covered also by the security setting
24696 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24698 @anchor{with-auto-load-dir}
24699 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24700 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24701 configuration option @option{--with-auto-load-dir}.
24703 Any reference to @file{$debugdir} will get replaced by
24704 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24705 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24706 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24707 @file{$datadir} must be placed as a directory component --- either alone or
24708 delimited by @file{/} or @file{\} directory separators, depending on the host
24711 The list of directories uses path separator (@samp{:} on GNU and Unix
24712 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24713 to the @env{PATH} environment variable.
24715 @anchor{show auto-load scripts-directory}
24716 @kindex show auto-load scripts-directory
24717 @item show auto-load scripts-directory
24718 Show @value{GDBN} auto-loaded scripts location.
24720 @anchor{add-auto-load-scripts-directory}
24721 @kindex add-auto-load-scripts-directory
24722 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24723 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24724 Multiple entries may be delimited by the host platform path separator in use.
24727 @value{GDBN} does not track which files it has already auto-loaded this way.
24728 @value{GDBN} will load the associated script every time the corresponding
24729 @var{objfile} is opened.
24730 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24731 is evaluated more than once.
24733 @node dotdebug_gdb_scripts section
24734 @subsection The @code{.debug_gdb_scripts} section
24735 @cindex @code{.debug_gdb_scripts} section
24737 For systems using file formats like ELF and COFF,
24738 when @value{GDBN} loads a new object file
24739 it will look for a special section named @code{.debug_gdb_scripts}.
24740 If this section exists, its contents is a list of null-terminated entries
24741 specifying scripts to load. Each entry begins with a non-null prefix byte that
24742 specifies the kind of entry, typically the extension language and whether the
24743 script is in a file or inlined in @code{.debug_gdb_scripts}.
24745 The following entries are supported:
24748 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24749 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24750 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24751 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24754 @subsubsection Script File Entries
24756 If the entry specifies a file, @value{GDBN} will look for the file first
24757 in the current directory and then along the source search path
24758 (@pxref{Source Path, ,Specifying Source Directories}),
24759 except that @file{$cdir} is not searched, since the compilation
24760 directory is not relevant to scripts.
24762 File entries can be placed in section @code{.debug_gdb_scripts} with,
24763 for example, this GCC macro for Python scripts.
24766 /* Note: The "MS" section flags are to remove duplicates. */
24767 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24769 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24770 .byte 1 /* Python */\n\
24771 .asciz \"" script_name "\"\n\
24777 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24778 Then one can reference the macro in a header or source file like this:
24781 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24784 The script name may include directories if desired.
24786 Note that loading of this script file also requires accordingly configured
24787 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24789 If the macro invocation is put in a header, any application or library
24790 using this header will get a reference to the specified script,
24791 and with the use of @code{"MS"} attributes on the section, the linker
24792 will remove duplicates.
24794 @subsubsection Script Text Entries
24796 Script text entries allow to put the executable script in the entry
24797 itself instead of loading it from a file.
24798 The first line of the entry, everything after the prefix byte and up to
24799 the first newline (@code{0xa}) character, is the script name, and must not
24800 contain any kind of space character, e.g., spaces or tabs.
24801 The rest of the entry, up to the trailing null byte, is the script to
24802 execute in the specified language. The name needs to be unique among
24803 all script names, as @value{GDBN} executes each script only once based
24806 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24810 #include "symcat.h"
24811 #include "gdb/section-scripts.h"
24813 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24814 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24815 ".ascii \"gdb.inlined-script\\n\"\n"
24816 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24817 ".ascii \" def __init__ (self):\\n\"\n"
24818 ".ascii \" super (test_cmd, self).__init__ ("
24819 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24820 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24821 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24822 ".ascii \"test_cmd ()\\n\"\n"
24828 Loading of inlined scripts requires a properly configured
24829 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24830 The path to specify in @code{auto-load safe-path} is the path of the file
24831 containing the @code{.debug_gdb_scripts} section.
24833 @node Which flavor to choose?
24834 @subsection Which flavor to choose?
24836 Given the multiple ways of auto-loading extensions, it might not always
24837 be clear which one to choose. This section provides some guidance.
24840 Benefits of the @file{-gdb.@var{ext}} way:
24844 Can be used with file formats that don't support multiple sections.
24847 Ease of finding scripts for public libraries.
24849 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24850 in the source search path.
24851 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24852 isn't a source directory in which to find the script.
24855 Doesn't require source code additions.
24859 Benefits of the @code{.debug_gdb_scripts} way:
24863 Works with static linking.
24865 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24866 trigger their loading. When an application is statically linked the only
24867 objfile available is the executable, and it is cumbersome to attach all the
24868 scripts from all the input libraries to the executable's
24869 @file{-gdb.@var{ext}} script.
24872 Works with classes that are entirely inlined.
24874 Some classes can be entirely inlined, and thus there may not be an associated
24875 shared library to attach a @file{-gdb.@var{ext}} script to.
24878 Scripts needn't be copied out of the source tree.
24880 In some circumstances, apps can be built out of large collections of internal
24881 libraries, and the build infrastructure necessary to install the
24882 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24883 cumbersome. It may be easier to specify the scripts in the
24884 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24885 top of the source tree to the source search path.
24888 @node Multiple Extension Languages
24889 @section Multiple Extension Languages
24891 The Guile and Python extension languages do not share any state,
24892 and generally do not interfere with each other.
24893 There are some things to be aware of, however.
24895 @subsection Python comes first
24897 Python was @value{GDBN}'s first extension language, and to avoid breaking
24898 existing behaviour Python comes first. This is generally solved by the
24899 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24900 extension languages, and when it makes a call to an extension language,
24901 (say to pretty-print a value), it tries each in turn until an extension
24902 language indicates it has performed the request (e.g., has returned the
24903 pretty-printed form of a value).
24904 This extends to errors while performing such requests: If an error happens
24905 while, for example, trying to pretty-print an object then the error is
24906 reported and any following extension languages are not tried.
24909 @section Creating new spellings of existing commands
24910 @cindex aliases for commands
24912 It is often useful to define alternate spellings of existing commands.
24913 For example, if a new @value{GDBN} command defined in Python has
24914 a long name to type, it is handy to have an abbreviated version of it
24915 that involves less typing.
24917 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24918 of the @samp{step} command even though it is otherwise an ambiguous
24919 abbreviation of other commands like @samp{set} and @samp{show}.
24921 Aliases are also used to provide shortened or more common versions
24922 of multi-word commands. For example, @value{GDBN} provides the
24923 @samp{tty} alias of the @samp{set inferior-tty} command.
24925 You can define a new alias with the @samp{alias} command.
24930 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24934 @var{ALIAS} specifies the name of the new alias.
24935 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24938 @var{COMMAND} specifies the name of an existing command
24939 that is being aliased.
24941 The @samp{-a} option specifies that the new alias is an abbreviation
24942 of the command. Abbreviations are not shown in command
24943 lists displayed by the @samp{help} command.
24945 The @samp{--} option specifies the end of options,
24946 and is useful when @var{ALIAS} begins with a dash.
24948 Here is a simple example showing how to make an abbreviation
24949 of a command so that there is less to type.
24950 Suppose you were tired of typing @samp{disas}, the current
24951 shortest unambiguous abbreviation of the @samp{disassemble} command
24952 and you wanted an even shorter version named @samp{di}.
24953 The following will accomplish this.
24956 (gdb) alias -a di = disas
24959 Note that aliases are different from user-defined commands.
24960 With a user-defined command, you also need to write documentation
24961 for it with the @samp{document} command.
24962 An alias automatically picks up the documentation of the existing command.
24964 Here is an example where we make @samp{elms} an abbreviation of
24965 @samp{elements} in the @samp{set print elements} command.
24966 This is to show that you can make an abbreviation of any part
24970 (gdb) alias -a set print elms = set print elements
24971 (gdb) alias -a show print elms = show print elements
24972 (gdb) set p elms 20
24974 Limit on string chars or array elements to print is 200.
24977 Note that if you are defining an alias of a @samp{set} command,
24978 and you want to have an alias for the corresponding @samp{show}
24979 command, then you need to define the latter separately.
24981 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24982 @var{ALIAS}, just as they are normally.
24985 (gdb) alias -a set pr elms = set p ele
24988 Finally, here is an example showing the creation of a one word
24989 alias for a more complex command.
24990 This creates alias @samp{spe} of the command @samp{set print elements}.
24993 (gdb) alias spe = set print elements
24998 @chapter Command Interpreters
24999 @cindex command interpreters
25001 @value{GDBN} supports multiple command interpreters, and some command
25002 infrastructure to allow users or user interface writers to switch
25003 between interpreters or run commands in other interpreters.
25005 @value{GDBN} currently supports two command interpreters, the console
25006 interpreter (sometimes called the command-line interpreter or @sc{cli})
25007 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25008 describes both of these interfaces in great detail.
25010 By default, @value{GDBN} will start with the console interpreter.
25011 However, the user may choose to start @value{GDBN} with another
25012 interpreter by specifying the @option{-i} or @option{--interpreter}
25013 startup options. Defined interpreters include:
25017 @cindex console interpreter
25018 The traditional console or command-line interpreter. This is the most often
25019 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25020 @value{GDBN} will use this interpreter.
25023 @cindex mi interpreter
25024 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25025 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25026 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25030 @cindex mi2 interpreter
25031 The current @sc{gdb/mi} interface.
25034 @cindex mi1 interpreter
25035 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25039 @cindex invoke another interpreter
25041 @kindex interpreter-exec
25042 You may execute commands in any interpreter from the current
25043 interpreter using the appropriate command. If you are running the
25044 console interpreter, simply use the @code{interpreter-exec} command:
25047 interpreter-exec mi "-data-list-register-names"
25050 @sc{gdb/mi} has a similar command, although it is only available in versions of
25051 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25053 Note that @code{interpreter-exec} only changes the interpreter for the
25054 duration of the specified command. It does not change the interpreter
25057 @cindex start a new independent interpreter
25059 Although you may only choose a single interpreter at startup, it is
25060 possible to run an independent interpreter on a specified input/output
25061 device (usually a tty).
25063 For example, consider a debugger GUI or IDE that wants to provide a
25064 @value{GDBN} console view. It may do so by embedding a terminal
25065 emulator widget in its GUI, starting @value{GDBN} in the traditional
25066 command-line mode with stdin/stdout/stderr redirected to that
25067 terminal, and then creating an MI interpreter running on a specified
25068 input/output device. The console interpreter created by @value{GDBN}
25069 at startup handles commands the user types in the terminal widget,
25070 while the GUI controls and synchronizes state with @value{GDBN} using
25071 the separate MI interpreter.
25073 To start a new secondary @dfn{user interface} running MI, use the
25074 @code{new-ui} command:
25077 @cindex new user interface
25079 new-ui @var{interpreter} @var{tty}
25082 The @var{interpreter} parameter specifies the interpreter to run.
25083 This accepts the same values as the @code{interpreter-exec} command.
25084 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25085 @var{tty} parameter specifies the name of the bidirectional file the
25086 interpreter uses for input/output, usually the name of a
25087 pseudoterminal slave on Unix systems. For example:
25090 (@value{GDBP}) new-ui mi /dev/pts/9
25094 runs an MI interpreter on @file{/dev/pts/9}.
25097 @chapter @value{GDBN} Text User Interface
25099 @cindex Text User Interface
25102 * TUI Overview:: TUI overview
25103 * TUI Keys:: TUI key bindings
25104 * TUI Single Key Mode:: TUI single key mode
25105 * TUI Commands:: TUI-specific commands
25106 * TUI Configuration:: TUI configuration variables
25109 The @value{GDBN} Text User Interface (TUI) is a terminal
25110 interface which uses the @code{curses} library to show the source
25111 file, the assembly output, the program registers and @value{GDBN}
25112 commands in separate text windows. The TUI mode is supported only
25113 on platforms where a suitable version of the @code{curses} library
25116 The TUI mode is enabled by default when you invoke @value{GDBN} as
25117 @samp{@value{GDBP} -tui}.
25118 You can also switch in and out of TUI mode while @value{GDBN} runs by
25119 using various TUI commands and key bindings, such as @command{tui
25120 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25121 @ref{TUI Keys, ,TUI Key Bindings}.
25124 @section TUI Overview
25126 In TUI mode, @value{GDBN} can display several text windows:
25130 This window is the @value{GDBN} command window with the @value{GDBN}
25131 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25132 managed using readline.
25135 The source window shows the source file of the program. The current
25136 line and active breakpoints are displayed in this window.
25139 The assembly window shows the disassembly output of the program.
25142 This window shows the processor registers. Registers are highlighted
25143 when their values change.
25146 The source and assembly windows show the current program position
25147 by highlighting the current line and marking it with a @samp{>} marker.
25148 Breakpoints are indicated with two markers. The first marker
25149 indicates the breakpoint type:
25153 Breakpoint which was hit at least once.
25156 Breakpoint which was never hit.
25159 Hardware breakpoint which was hit at least once.
25162 Hardware breakpoint which was never hit.
25165 The second marker indicates whether the breakpoint is enabled or not:
25169 Breakpoint is enabled.
25172 Breakpoint is disabled.
25175 The source, assembly and register windows are updated when the current
25176 thread changes, when the frame changes, or when the program counter
25179 These windows are not all visible at the same time. The command
25180 window is always visible. The others can be arranged in several
25191 source and assembly,
25194 source and registers, or
25197 assembly and registers.
25200 A status line above the command window shows the following information:
25204 Indicates the current @value{GDBN} target.
25205 (@pxref{Targets, ,Specifying a Debugging Target}).
25208 Gives the current process or thread number.
25209 When no process is being debugged, this field is set to @code{No process}.
25212 Gives the current function name for the selected frame.
25213 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25214 When there is no symbol corresponding to the current program counter,
25215 the string @code{??} is displayed.
25218 Indicates the current line number for the selected frame.
25219 When the current line number is not known, the string @code{??} is displayed.
25222 Indicates the current program counter address.
25226 @section TUI Key Bindings
25227 @cindex TUI key bindings
25229 The TUI installs several key bindings in the readline keymaps
25230 @ifset SYSTEM_READLINE
25231 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25233 @ifclear SYSTEM_READLINE
25234 (@pxref{Command Line Editing}).
25236 The following key bindings are installed for both TUI mode and the
25237 @value{GDBN} standard mode.
25246 Enter or leave the TUI mode. When leaving the TUI mode,
25247 the curses window management stops and @value{GDBN} operates using
25248 its standard mode, writing on the terminal directly. When reentering
25249 the TUI mode, control is given back to the curses windows.
25250 The screen is then refreshed.
25254 Use a TUI layout with only one window. The layout will
25255 either be @samp{source} or @samp{assembly}. When the TUI mode
25256 is not active, it will switch to the TUI mode.
25258 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25262 Use a TUI layout with at least two windows. When the current
25263 layout already has two windows, the next layout with two windows is used.
25264 When a new layout is chosen, one window will always be common to the
25265 previous layout and the new one.
25267 Think of it as the Emacs @kbd{C-x 2} binding.
25271 Change the active window. The TUI associates several key bindings
25272 (like scrolling and arrow keys) with the active window. This command
25273 gives the focus to the next TUI window.
25275 Think of it as the Emacs @kbd{C-x o} binding.
25279 Switch in and out of the TUI SingleKey mode that binds single
25280 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25283 The following key bindings only work in the TUI mode:
25288 Scroll the active window one page up.
25292 Scroll the active window one page down.
25296 Scroll the active window one line up.
25300 Scroll the active window one line down.
25304 Scroll the active window one column left.
25308 Scroll the active window one column right.
25312 Refresh the screen.
25315 Because the arrow keys scroll the active window in the TUI mode, they
25316 are not available for their normal use by readline unless the command
25317 window has the focus. When another window is active, you must use
25318 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25319 and @kbd{C-f} to control the command window.
25321 @node TUI Single Key Mode
25322 @section TUI Single Key Mode
25323 @cindex TUI single key mode
25325 The TUI also provides a @dfn{SingleKey} mode, which binds several
25326 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25327 switch into this mode, where the following key bindings are used:
25330 @kindex c @r{(SingleKey TUI key)}
25334 @kindex d @r{(SingleKey TUI key)}
25338 @kindex f @r{(SingleKey TUI key)}
25342 @kindex n @r{(SingleKey TUI key)}
25346 @kindex q @r{(SingleKey TUI key)}
25348 exit the SingleKey mode.
25350 @kindex r @r{(SingleKey TUI key)}
25354 @kindex s @r{(SingleKey TUI key)}
25358 @kindex u @r{(SingleKey TUI key)}
25362 @kindex v @r{(SingleKey TUI key)}
25366 @kindex w @r{(SingleKey TUI key)}
25371 Other keys temporarily switch to the @value{GDBN} command prompt.
25372 The key that was pressed is inserted in the editing buffer so that
25373 it is possible to type most @value{GDBN} commands without interaction
25374 with the TUI SingleKey mode. Once the command is entered the TUI
25375 SingleKey mode is restored. The only way to permanently leave
25376 this mode is by typing @kbd{q} or @kbd{C-x s}.
25380 @section TUI-specific Commands
25381 @cindex TUI commands
25383 The TUI has specific commands to control the text windows.
25384 These commands are always available, even when @value{GDBN} is not in
25385 the TUI mode. When @value{GDBN} is in the standard mode, most
25386 of these commands will automatically switch to the TUI mode.
25388 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25389 terminal, or @value{GDBN} has been started with the machine interface
25390 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25391 these commands will fail with an error, because it would not be
25392 possible or desirable to enable curses window management.
25397 Activate TUI mode. The last active TUI window layout will be used if
25398 TUI mode has prevsiouly been used in the current debugging session,
25399 otherwise a default layout is used.
25402 @kindex tui disable
25403 Disable TUI mode, returning to the console interpreter.
25407 List and give the size of all displayed windows.
25409 @item layout @var{name}
25411 Changes which TUI windows are displayed. In each layout the command
25412 window is always displayed, the @var{name} parameter controls which
25413 additional windows are displayed, and can be any of the following:
25417 Display the next layout.
25420 Display the previous layout.
25423 Display the source and command windows.
25426 Display the assembly and command windows.
25429 Display the source, assembly, and command windows.
25432 When in @code{src} layout display the register, source, and command
25433 windows. When in @code{asm} or @code{split} layout display the
25434 register, assembler, and command windows.
25437 @item focus @var{name}
25439 Changes which TUI window is currently active for scrolling. The
25440 @var{name} parameter can be any of the following:
25444 Make the next window active for scrolling.
25447 Make the previous window active for scrolling.
25450 Make the source window active for scrolling.
25453 Make the assembly window active for scrolling.
25456 Make the register window active for scrolling.
25459 Make the command window active for scrolling.
25464 Refresh the screen. This is similar to typing @kbd{C-L}.
25466 @item tui reg @var{group}
25468 Changes the register group displayed in the tui register window to
25469 @var{group}. If the register window is not currently displayed this
25470 command will cause the register window to be displayed. The list of
25471 register groups, as well as their order is target specific. The
25472 following groups are available on most targets:
25475 Repeatedly selecting this group will cause the display to cycle
25476 through all of the available register groups.
25479 Repeatedly selecting this group will cause the display to cycle
25480 through all of the available register groups in the reverse order to
25484 Display the general registers.
25486 Display the floating point registers.
25488 Display the system registers.
25490 Display the vector registers.
25492 Display all registers.
25497 Update the source window and the current execution point.
25499 @item winheight @var{name} +@var{count}
25500 @itemx winheight @var{name} -@var{count}
25502 Change the height of the window @var{name} by @var{count}
25503 lines. Positive counts increase the height, while negative counts
25504 decrease it. The @var{name} parameter can be one of @code{src} (the
25505 source window), @code{cmd} (the command window), @code{asm} (the
25506 disassembly window), or @code{regs} (the register display window).
25508 @item tabset @var{nchars}
25510 Set the width of tab stops to be @var{nchars} characters. This
25511 setting affects the display of TAB characters in the source and
25515 @node TUI Configuration
25516 @section TUI Configuration Variables
25517 @cindex TUI configuration variables
25519 Several configuration variables control the appearance of TUI windows.
25522 @item set tui border-kind @var{kind}
25523 @kindex set tui border-kind
25524 Select the border appearance for the source, assembly and register windows.
25525 The possible values are the following:
25528 Use a space character to draw the border.
25531 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25534 Use the Alternate Character Set to draw the border. The border is
25535 drawn using character line graphics if the terminal supports them.
25538 @item set tui border-mode @var{mode}
25539 @kindex set tui border-mode
25540 @itemx set tui active-border-mode @var{mode}
25541 @kindex set tui active-border-mode
25542 Select the display attributes for the borders of the inactive windows
25543 or the active window. The @var{mode} can be one of the following:
25546 Use normal attributes to display the border.
25552 Use reverse video mode.
25555 Use half bright mode.
25557 @item half-standout
25558 Use half bright and standout mode.
25561 Use extra bright or bold mode.
25563 @item bold-standout
25564 Use extra bright or bold and standout mode.
25569 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25572 @cindex @sc{gnu} Emacs
25573 A special interface allows you to use @sc{gnu} Emacs to view (and
25574 edit) the source files for the program you are debugging with
25577 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25578 executable file you want to debug as an argument. This command starts
25579 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25580 created Emacs buffer.
25581 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25583 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25588 All ``terminal'' input and output goes through an Emacs buffer, called
25591 This applies both to @value{GDBN} commands and their output, and to the input
25592 and output done by the program you are debugging.
25594 This is useful because it means that you can copy the text of previous
25595 commands and input them again; you can even use parts of the output
25598 All the facilities of Emacs' Shell mode are available for interacting
25599 with your program. In particular, you can send signals the usual
25600 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25604 @value{GDBN} displays source code through Emacs.
25606 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25607 source file for that frame and puts an arrow (@samp{=>}) at the
25608 left margin of the current line. Emacs uses a separate buffer for
25609 source display, and splits the screen to show both your @value{GDBN} session
25612 Explicit @value{GDBN} @code{list} or search commands still produce output as
25613 usual, but you probably have no reason to use them from Emacs.
25616 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25617 a graphical mode, enabled by default, which provides further buffers
25618 that can control the execution and describe the state of your program.
25619 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25621 If you specify an absolute file name when prompted for the @kbd{M-x
25622 gdb} argument, then Emacs sets your current working directory to where
25623 your program resides. If you only specify the file name, then Emacs
25624 sets your current working directory to the directory associated
25625 with the previous buffer. In this case, @value{GDBN} may find your
25626 program by searching your environment's @code{PATH} variable, but on
25627 some operating systems it might not find the source. So, although the
25628 @value{GDBN} input and output session proceeds normally, the auxiliary
25629 buffer does not display the current source and line of execution.
25631 The initial working directory of @value{GDBN} is printed on the top
25632 line of the GUD buffer and this serves as a default for the commands
25633 that specify files for @value{GDBN} to operate on. @xref{Files,
25634 ,Commands to Specify Files}.
25636 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25637 need to call @value{GDBN} by a different name (for example, if you
25638 keep several configurations around, with different names) you can
25639 customize the Emacs variable @code{gud-gdb-command-name} to run the
25642 In the GUD buffer, you can use these special Emacs commands in
25643 addition to the standard Shell mode commands:
25647 Describe the features of Emacs' GUD Mode.
25650 Execute to another source line, like the @value{GDBN} @code{step} command; also
25651 update the display window to show the current file and location.
25654 Execute to next source line in this function, skipping all function
25655 calls, like the @value{GDBN} @code{next} command. Then update the display window
25656 to show the current file and location.
25659 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25660 display window accordingly.
25663 Execute until exit from the selected stack frame, like the @value{GDBN}
25664 @code{finish} command.
25667 Continue execution of your program, like the @value{GDBN} @code{continue}
25671 Go up the number of frames indicated by the numeric argument
25672 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25673 like the @value{GDBN} @code{up} command.
25676 Go down the number of frames indicated by the numeric argument, like the
25677 @value{GDBN} @code{down} command.
25680 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25681 tells @value{GDBN} to set a breakpoint on the source line point is on.
25683 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25684 separate frame which shows a backtrace when the GUD buffer is current.
25685 Move point to any frame in the stack and type @key{RET} to make it
25686 become the current frame and display the associated source in the
25687 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25688 selected frame become the current one. In graphical mode, the
25689 speedbar displays watch expressions.
25691 If you accidentally delete the source-display buffer, an easy way to get
25692 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25693 request a frame display; when you run under Emacs, this recreates
25694 the source buffer if necessary to show you the context of the current
25697 The source files displayed in Emacs are in ordinary Emacs buffers
25698 which are visiting the source files in the usual way. You can edit
25699 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25700 communicates with Emacs in terms of line numbers. If you add or
25701 delete lines from the text, the line numbers that @value{GDBN} knows cease
25702 to correspond properly with the code.
25704 A more detailed description of Emacs' interaction with @value{GDBN} is
25705 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25709 @chapter The @sc{gdb/mi} Interface
25711 @unnumberedsec Function and Purpose
25713 @cindex @sc{gdb/mi}, its purpose
25714 @sc{gdb/mi} is a line based machine oriented text interface to
25715 @value{GDBN} and is activated by specifying using the
25716 @option{--interpreter} command line option (@pxref{Mode Options}). It
25717 is specifically intended to support the development of systems which
25718 use the debugger as just one small component of a larger system.
25720 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25721 in the form of a reference manual.
25723 Note that @sc{gdb/mi} is still under construction, so some of the
25724 features described below are incomplete and subject to change
25725 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25727 @unnumberedsec Notation and Terminology
25729 @cindex notational conventions, for @sc{gdb/mi}
25730 This chapter uses the following notation:
25734 @code{|} separates two alternatives.
25737 @code{[ @var{something} ]} indicates that @var{something} is optional:
25738 it may or may not be given.
25741 @code{( @var{group} )*} means that @var{group} inside the parentheses
25742 may repeat zero or more times.
25745 @code{( @var{group} )+} means that @var{group} inside the parentheses
25746 may repeat one or more times.
25749 @code{"@var{string}"} means a literal @var{string}.
25753 @heading Dependencies
25757 * GDB/MI General Design::
25758 * GDB/MI Command Syntax::
25759 * GDB/MI Compatibility with CLI::
25760 * GDB/MI Development and Front Ends::
25761 * GDB/MI Output Records::
25762 * GDB/MI Simple Examples::
25763 * GDB/MI Command Description Format::
25764 * GDB/MI Breakpoint Commands::
25765 * GDB/MI Catchpoint Commands::
25766 * GDB/MI Program Context::
25767 * GDB/MI Thread Commands::
25768 * GDB/MI Ada Tasking Commands::
25769 * GDB/MI Program Execution::
25770 * GDB/MI Stack Manipulation::
25771 * GDB/MI Variable Objects::
25772 * GDB/MI Data Manipulation::
25773 * GDB/MI Tracepoint Commands::
25774 * GDB/MI Symbol Query::
25775 * GDB/MI File Commands::
25777 * GDB/MI Kod Commands::
25778 * GDB/MI Memory Overlay Commands::
25779 * GDB/MI Signal Handling Commands::
25781 * GDB/MI Target Manipulation::
25782 * GDB/MI File Transfer Commands::
25783 * GDB/MI Ada Exceptions Commands::
25784 * GDB/MI Support Commands::
25785 * GDB/MI Miscellaneous Commands::
25788 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25789 @node GDB/MI General Design
25790 @section @sc{gdb/mi} General Design
25791 @cindex GDB/MI General Design
25793 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25794 parts---commands sent to @value{GDBN}, responses to those commands
25795 and notifications. Each command results in exactly one response,
25796 indicating either successful completion of the command, or an error.
25797 For the commands that do not resume the target, the response contains the
25798 requested information. For the commands that resume the target, the
25799 response only indicates whether the target was successfully resumed.
25800 Notifications is the mechanism for reporting changes in the state of the
25801 target, or in @value{GDBN} state, that cannot conveniently be associated with
25802 a command and reported as part of that command response.
25804 The important examples of notifications are:
25808 Exec notifications. These are used to report changes in
25809 target state---when a target is resumed, or stopped. It would not
25810 be feasible to include this information in response of resuming
25811 commands, because one resume commands can result in multiple events in
25812 different threads. Also, quite some time may pass before any event
25813 happens in the target, while a frontend needs to know whether the resuming
25814 command itself was successfully executed.
25817 Console output, and status notifications. Console output
25818 notifications are used to report output of CLI commands, as well as
25819 diagnostics for other commands. Status notifications are used to
25820 report the progress of a long-running operation. Naturally, including
25821 this information in command response would mean no output is produced
25822 until the command is finished, which is undesirable.
25825 General notifications. Commands may have various side effects on
25826 the @value{GDBN} or target state beyond their official purpose. For example,
25827 a command may change the selected thread. Although such changes can
25828 be included in command response, using notification allows for more
25829 orthogonal frontend design.
25833 There's no guarantee that whenever an MI command reports an error,
25834 @value{GDBN} or the target are in any specific state, and especially,
25835 the state is not reverted to the state before the MI command was
25836 processed. Therefore, whenever an MI command results in an error,
25837 we recommend that the frontend refreshes all the information shown in
25838 the user interface.
25842 * Context management::
25843 * Asynchronous and non-stop modes::
25847 @node Context management
25848 @subsection Context management
25850 @subsubsection Threads and Frames
25852 In most cases when @value{GDBN} accesses the target, this access is
25853 done in context of a specific thread and frame (@pxref{Frames}).
25854 Often, even when accessing global data, the target requires that a thread
25855 be specified. The CLI interface maintains the selected thread and frame,
25856 and supplies them to target on each command. This is convenient,
25857 because a command line user would not want to specify that information
25858 explicitly on each command, and because user interacts with
25859 @value{GDBN} via a single terminal, so no confusion is possible as
25860 to what thread and frame are the current ones.
25862 In the case of MI, the concept of selected thread and frame is less
25863 useful. First, a frontend can easily remember this information
25864 itself. Second, a graphical frontend can have more than one window,
25865 each one used for debugging a different thread, and the frontend might
25866 want to access additional threads for internal purposes. This
25867 increases the risk that by relying on implicitly selected thread, the
25868 frontend may be operating on a wrong one. Therefore, each MI command
25869 should explicitly specify which thread and frame to operate on. To
25870 make it possible, each MI command accepts the @samp{--thread} and
25871 @samp{--frame} options, the value to each is @value{GDBN} global
25872 identifier for thread and frame to operate on.
25874 Usually, each top-level window in a frontend allows the user to select
25875 a thread and a frame, and remembers the user selection for further
25876 operations. However, in some cases @value{GDBN} may suggest that the
25877 current thread or frame be changed. For example, when stopping on a
25878 breakpoint it is reasonable to switch to the thread where breakpoint is
25879 hit. For another example, if the user issues the CLI @samp{thread} or
25880 @samp{frame} commands via the frontend, it is desirable to change the
25881 frontend's selection to the one specified by user. @value{GDBN}
25882 communicates the suggestion to change current thread and frame using the
25883 @samp{=thread-selected} notification.
25885 Note that historically, MI shares the selected thread with CLI, so
25886 frontends used the @code{-thread-select} to execute commands in the
25887 right context. However, getting this to work right is cumbersome. The
25888 simplest way is for frontend to emit @code{-thread-select} command
25889 before every command. This doubles the number of commands that need
25890 to be sent. The alternative approach is to suppress @code{-thread-select}
25891 if the selected thread in @value{GDBN} is supposed to be identical to the
25892 thread the frontend wants to operate on. However, getting this
25893 optimization right can be tricky. In particular, if the frontend
25894 sends several commands to @value{GDBN}, and one of the commands changes the
25895 selected thread, then the behaviour of subsequent commands will
25896 change. So, a frontend should either wait for response from such
25897 problematic commands, or explicitly add @code{-thread-select} for
25898 all subsequent commands. No frontend is known to do this exactly
25899 right, so it is suggested to just always pass the @samp{--thread} and
25900 @samp{--frame} options.
25902 @subsubsection Language
25904 The execution of several commands depends on which language is selected.
25905 By default, the current language (@pxref{show language}) is used.
25906 But for commands known to be language-sensitive, it is recommended
25907 to use the @samp{--language} option. This option takes one argument,
25908 which is the name of the language to use while executing the command.
25912 -data-evaluate-expression --language c "sizeof (void*)"
25917 The valid language names are the same names accepted by the
25918 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25919 @samp{local} or @samp{unknown}.
25921 @node Asynchronous and non-stop modes
25922 @subsection Asynchronous command execution and non-stop mode
25924 On some targets, @value{GDBN} is capable of processing MI commands
25925 even while the target is running. This is called @dfn{asynchronous
25926 command execution} (@pxref{Background Execution}). The frontend may
25927 specify a preferrence for asynchronous execution using the
25928 @code{-gdb-set mi-async 1} command, which should be emitted before
25929 either running the executable or attaching to the target. After the
25930 frontend has started the executable or attached to the target, it can
25931 find if asynchronous execution is enabled using the
25932 @code{-list-target-features} command.
25935 @item -gdb-set mi-async on
25936 @item -gdb-set mi-async off
25937 Set whether MI is in asynchronous mode.
25939 When @code{off}, which is the default, MI execution commands (e.g.,
25940 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25941 for the program to stop before processing further commands.
25943 When @code{on}, MI execution commands are background execution
25944 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25945 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25946 MI commands even while the target is running.
25948 @item -gdb-show mi-async
25949 Show whether MI asynchronous mode is enabled.
25952 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25953 @code{target-async} instead of @code{mi-async}, and it had the effect
25954 of both putting MI in asynchronous mode and making CLI background
25955 commands possible. CLI background commands are now always possible
25956 ``out of the box'' if the target supports them. The old spelling is
25957 kept as a deprecated alias for backwards compatibility.
25959 Even if @value{GDBN} can accept a command while target is running,
25960 many commands that access the target do not work when the target is
25961 running. Therefore, asynchronous command execution is most useful
25962 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25963 it is possible to examine the state of one thread, while other threads
25966 When a given thread is running, MI commands that try to access the
25967 target in the context of that thread may not work, or may work only on
25968 some targets. In particular, commands that try to operate on thread's
25969 stack will not work, on any target. Commands that read memory, or
25970 modify breakpoints, may work or not work, depending on the target. Note
25971 that even commands that operate on global state, such as @code{print},
25972 @code{set}, and breakpoint commands, still access the target in the
25973 context of a specific thread, so frontend should try to find a
25974 stopped thread and perform the operation on that thread (using the
25975 @samp{--thread} option).
25977 Which commands will work in the context of a running thread is
25978 highly target dependent. However, the two commands
25979 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25980 to find the state of a thread, will always work.
25982 @node Thread groups
25983 @subsection Thread groups
25984 @value{GDBN} may be used to debug several processes at the same time.
25985 On some platfroms, @value{GDBN} may support debugging of several
25986 hardware systems, each one having several cores with several different
25987 processes running on each core. This section describes the MI
25988 mechanism to support such debugging scenarios.
25990 The key observation is that regardless of the structure of the
25991 target, MI can have a global list of threads, because most commands that
25992 accept the @samp{--thread} option do not need to know what process that
25993 thread belongs to. Therefore, it is not necessary to introduce
25994 neither additional @samp{--process} option, nor an notion of the
25995 current process in the MI interface. The only strictly new feature
25996 that is required is the ability to find how the threads are grouped
25999 To allow the user to discover such grouping, and to support arbitrary
26000 hierarchy of machines/cores/processes, MI introduces the concept of a
26001 @dfn{thread group}. Thread group is a collection of threads and other
26002 thread groups. A thread group always has a string identifier, a type,
26003 and may have additional attributes specific to the type. A new
26004 command, @code{-list-thread-groups}, returns the list of top-level
26005 thread groups, which correspond to processes that @value{GDBN} is
26006 debugging at the moment. By passing an identifier of a thread group
26007 to the @code{-list-thread-groups} command, it is possible to obtain
26008 the members of specific thread group.
26010 To allow the user to easily discover processes, and other objects, he
26011 wishes to debug, a concept of @dfn{available thread group} is
26012 introduced. Available thread group is an thread group that
26013 @value{GDBN} is not debugging, but that can be attached to, using the
26014 @code{-target-attach} command. The list of available top-level thread
26015 groups can be obtained using @samp{-list-thread-groups --available}.
26016 In general, the content of a thread group may be only retrieved only
26017 after attaching to that thread group.
26019 Thread groups are related to inferiors (@pxref{Inferiors and
26020 Programs}). Each inferior corresponds to a thread group of a special
26021 type @samp{process}, and some additional operations are permitted on
26022 such thread groups.
26024 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26025 @node GDB/MI Command Syntax
26026 @section @sc{gdb/mi} Command Syntax
26029 * GDB/MI Input Syntax::
26030 * GDB/MI Output Syntax::
26033 @node GDB/MI Input Syntax
26034 @subsection @sc{gdb/mi} Input Syntax
26036 @cindex input syntax for @sc{gdb/mi}
26037 @cindex @sc{gdb/mi}, input syntax
26039 @item @var{command} @expansion{}
26040 @code{@var{cli-command} | @var{mi-command}}
26042 @item @var{cli-command} @expansion{}
26043 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26044 @var{cli-command} is any existing @value{GDBN} CLI command.
26046 @item @var{mi-command} @expansion{}
26047 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26048 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26050 @item @var{token} @expansion{}
26051 "any sequence of digits"
26053 @item @var{option} @expansion{}
26054 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26056 @item @var{parameter} @expansion{}
26057 @code{@var{non-blank-sequence} | @var{c-string}}
26059 @item @var{operation} @expansion{}
26060 @emph{any of the operations described in this chapter}
26062 @item @var{non-blank-sequence} @expansion{}
26063 @emph{anything, provided it doesn't contain special characters such as
26064 "-", @var{nl}, """ and of course " "}
26066 @item @var{c-string} @expansion{}
26067 @code{""" @var{seven-bit-iso-c-string-content} """}
26069 @item @var{nl} @expansion{}
26078 The CLI commands are still handled by the @sc{mi} interpreter; their
26079 output is described below.
26082 The @code{@var{token}}, when present, is passed back when the command
26086 Some @sc{mi} commands accept optional arguments as part of the parameter
26087 list. Each option is identified by a leading @samp{-} (dash) and may be
26088 followed by an optional argument parameter. Options occur first in the
26089 parameter list and can be delimited from normal parameters using
26090 @samp{--} (this is useful when some parameters begin with a dash).
26097 We want easy access to the existing CLI syntax (for debugging).
26100 We want it to be easy to spot a @sc{mi} operation.
26103 @node GDB/MI Output Syntax
26104 @subsection @sc{gdb/mi} Output Syntax
26106 @cindex output syntax of @sc{gdb/mi}
26107 @cindex @sc{gdb/mi}, output syntax
26108 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26109 followed, optionally, by a single result record. This result record
26110 is for the most recent command. The sequence of output records is
26111 terminated by @samp{(gdb)}.
26113 If an input command was prefixed with a @code{@var{token}} then the
26114 corresponding output for that command will also be prefixed by that same
26118 @item @var{output} @expansion{}
26119 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26121 @item @var{result-record} @expansion{}
26122 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26124 @item @var{out-of-band-record} @expansion{}
26125 @code{@var{async-record} | @var{stream-record}}
26127 @item @var{async-record} @expansion{}
26128 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26130 @item @var{exec-async-output} @expansion{}
26131 @code{[ @var{token} ] "*" @var{async-output nl}}
26133 @item @var{status-async-output} @expansion{}
26134 @code{[ @var{token} ] "+" @var{async-output nl}}
26136 @item @var{notify-async-output} @expansion{}
26137 @code{[ @var{token} ] "=" @var{async-output nl}}
26139 @item @var{async-output} @expansion{}
26140 @code{@var{async-class} ( "," @var{result} )*}
26142 @item @var{result-class} @expansion{}
26143 @code{"done" | "running" | "connected" | "error" | "exit"}
26145 @item @var{async-class} @expansion{}
26146 @code{"stopped" | @var{others}} (where @var{others} will be added
26147 depending on the needs---this is still in development).
26149 @item @var{result} @expansion{}
26150 @code{ @var{variable} "=" @var{value}}
26152 @item @var{variable} @expansion{}
26153 @code{ @var{string} }
26155 @item @var{value} @expansion{}
26156 @code{ @var{const} | @var{tuple} | @var{list} }
26158 @item @var{const} @expansion{}
26159 @code{@var{c-string}}
26161 @item @var{tuple} @expansion{}
26162 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26164 @item @var{list} @expansion{}
26165 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26166 @var{result} ( "," @var{result} )* "]" }
26168 @item @var{stream-record} @expansion{}
26169 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26171 @item @var{console-stream-output} @expansion{}
26172 @code{"~" @var{c-string nl}}
26174 @item @var{target-stream-output} @expansion{}
26175 @code{"@@" @var{c-string nl}}
26177 @item @var{log-stream-output} @expansion{}
26178 @code{"&" @var{c-string nl}}
26180 @item @var{nl} @expansion{}
26183 @item @var{token} @expansion{}
26184 @emph{any sequence of digits}.
26192 All output sequences end in a single line containing a period.
26195 The @code{@var{token}} is from the corresponding request. Note that
26196 for all async output, while the token is allowed by the grammar and
26197 may be output by future versions of @value{GDBN} for select async
26198 output messages, it is generally omitted. Frontends should treat
26199 all async output as reporting general changes in the state of the
26200 target and there should be no need to associate async output to any
26204 @cindex status output in @sc{gdb/mi}
26205 @var{status-async-output} contains on-going status information about the
26206 progress of a slow operation. It can be discarded. All status output is
26207 prefixed by @samp{+}.
26210 @cindex async output in @sc{gdb/mi}
26211 @var{exec-async-output} contains asynchronous state change on the target
26212 (stopped, started, disappeared). All async output is prefixed by
26216 @cindex notify output in @sc{gdb/mi}
26217 @var{notify-async-output} contains supplementary information that the
26218 client should handle (e.g., a new breakpoint information). All notify
26219 output is prefixed by @samp{=}.
26222 @cindex console output in @sc{gdb/mi}
26223 @var{console-stream-output} is output that should be displayed as is in the
26224 console. It is the textual response to a CLI command. All the console
26225 output is prefixed by @samp{~}.
26228 @cindex target output in @sc{gdb/mi}
26229 @var{target-stream-output} is the output produced by the target program.
26230 All the target output is prefixed by @samp{@@}.
26233 @cindex log output in @sc{gdb/mi}
26234 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26235 instance messages that should be displayed as part of an error log. All
26236 the log output is prefixed by @samp{&}.
26239 @cindex list output in @sc{gdb/mi}
26240 New @sc{gdb/mi} commands should only output @var{lists} containing
26246 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26247 details about the various output records.
26249 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26250 @node GDB/MI Compatibility with CLI
26251 @section @sc{gdb/mi} Compatibility with CLI
26253 @cindex compatibility, @sc{gdb/mi} and CLI
26254 @cindex @sc{gdb/mi}, compatibility with CLI
26256 For the developers convenience CLI commands can be entered directly,
26257 but there may be some unexpected behaviour. For example, commands
26258 that query the user will behave as if the user replied yes, breakpoint
26259 command lists are not executed and some CLI commands, such as
26260 @code{if}, @code{when} and @code{define}, prompt for further input with
26261 @samp{>}, which is not valid MI output.
26263 This feature may be removed at some stage in the future and it is
26264 recommended that front ends use the @code{-interpreter-exec} command
26265 (@pxref{-interpreter-exec}).
26267 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26268 @node GDB/MI Development and Front Ends
26269 @section @sc{gdb/mi} Development and Front Ends
26270 @cindex @sc{gdb/mi} development
26272 The application which takes the MI output and presents the state of the
26273 program being debugged to the user is called a @dfn{front end}.
26275 Although @sc{gdb/mi} is still incomplete, it is currently being used
26276 by a variety of front ends to @value{GDBN}. This makes it difficult
26277 to introduce new functionality without breaking existing usage. This
26278 section tries to minimize the problems by describing how the protocol
26281 Some changes in MI need not break a carefully designed front end, and
26282 for these the MI version will remain unchanged. The following is a
26283 list of changes that may occur within one level, so front ends should
26284 parse MI output in a way that can handle them:
26288 New MI commands may be added.
26291 New fields may be added to the output of any MI command.
26294 The range of values for fields with specified values, e.g.,
26295 @code{in_scope} (@pxref{-var-update}) may be extended.
26297 @c The format of field's content e.g type prefix, may change so parse it
26298 @c at your own risk. Yes, in general?
26300 @c The order of fields may change? Shouldn't really matter but it might
26301 @c resolve inconsistencies.
26304 If the changes are likely to break front ends, the MI version level
26305 will be increased by one. This will allow the front end to parse the
26306 output according to the MI version. Apart from mi0, new versions of
26307 @value{GDBN} will not support old versions of MI and it will be the
26308 responsibility of the front end to work with the new one.
26310 @c Starting with mi3, add a new command -mi-version that prints the MI
26313 The best way to avoid unexpected changes in MI that might break your front
26314 end is to make your project known to @value{GDBN} developers and
26315 follow development on @email{gdb@@sourceware.org} and
26316 @email{gdb-patches@@sourceware.org}.
26317 @cindex mailing lists
26319 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26320 @node GDB/MI Output Records
26321 @section @sc{gdb/mi} Output Records
26324 * GDB/MI Result Records::
26325 * GDB/MI Stream Records::
26326 * GDB/MI Async Records::
26327 * GDB/MI Breakpoint Information::
26328 * GDB/MI Frame Information::
26329 * GDB/MI Thread Information::
26330 * GDB/MI Ada Exception Information::
26333 @node GDB/MI Result Records
26334 @subsection @sc{gdb/mi} Result Records
26336 @cindex result records in @sc{gdb/mi}
26337 @cindex @sc{gdb/mi}, result records
26338 In addition to a number of out-of-band notifications, the response to a
26339 @sc{gdb/mi} command includes one of the following result indications:
26343 @item "^done" [ "," @var{results} ]
26344 The synchronous operation was successful, @code{@var{results}} are the return
26349 This result record is equivalent to @samp{^done}. Historically, it
26350 was output instead of @samp{^done} if the command has resumed the
26351 target. This behaviour is maintained for backward compatibility, but
26352 all frontends should treat @samp{^done} and @samp{^running}
26353 identically and rely on the @samp{*running} output record to determine
26354 which threads are resumed.
26358 @value{GDBN} has connected to a remote target.
26360 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26362 The operation failed. The @code{msg=@var{c-string}} variable contains
26363 the corresponding error message.
26365 If present, the @code{code=@var{c-string}} variable provides an error
26366 code on which consumers can rely on to detect the corresponding
26367 error condition. At present, only one error code is defined:
26370 @item "undefined-command"
26371 Indicates that the command causing the error does not exist.
26376 @value{GDBN} has terminated.
26380 @node GDB/MI Stream Records
26381 @subsection @sc{gdb/mi} Stream Records
26383 @cindex @sc{gdb/mi}, stream records
26384 @cindex stream records in @sc{gdb/mi}
26385 @value{GDBN} internally maintains a number of output streams: the console, the
26386 target, and the log. The output intended for each of these streams is
26387 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26389 Each stream record begins with a unique @dfn{prefix character} which
26390 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26391 Syntax}). In addition to the prefix, each stream record contains a
26392 @code{@var{string-output}}. This is either raw text (with an implicit new
26393 line) or a quoted C string (which does not contain an implicit newline).
26396 @item "~" @var{string-output}
26397 The console output stream contains text that should be displayed in the
26398 CLI console window. It contains the textual responses to CLI commands.
26400 @item "@@" @var{string-output}
26401 The target output stream contains any textual output from the running
26402 target. This is only present when GDB's event loop is truly
26403 asynchronous, which is currently only the case for remote targets.
26405 @item "&" @var{string-output}
26406 The log stream contains debugging messages being produced by @value{GDBN}'s
26410 @node GDB/MI Async Records
26411 @subsection @sc{gdb/mi} Async Records
26413 @cindex async records in @sc{gdb/mi}
26414 @cindex @sc{gdb/mi}, async records
26415 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26416 additional changes that have occurred. Those changes can either be a
26417 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26418 target activity (e.g., target stopped).
26420 The following is the list of possible async records:
26424 @item *running,thread-id="@var{thread}"
26425 The target is now running. The @var{thread} field can be the global
26426 thread ID of the the thread that is now running, and it can be
26427 @samp{all} if all threads are running. The frontend should assume
26428 that no interaction with a running thread is possible after this
26429 notification is produced. The frontend should not assume that this
26430 notification is output only once for any command. @value{GDBN} may
26431 emit this notification several times, either for different threads,
26432 because it cannot resume all threads together, or even for a single
26433 thread, if the thread must be stepped though some code before letting
26436 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26437 The target has stopped. The @var{reason} field can have one of the
26441 @item breakpoint-hit
26442 A breakpoint was reached.
26443 @item watchpoint-trigger
26444 A watchpoint was triggered.
26445 @item read-watchpoint-trigger
26446 A read watchpoint was triggered.
26447 @item access-watchpoint-trigger
26448 An access watchpoint was triggered.
26449 @item function-finished
26450 An -exec-finish or similar CLI command was accomplished.
26451 @item location-reached
26452 An -exec-until or similar CLI command was accomplished.
26453 @item watchpoint-scope
26454 A watchpoint has gone out of scope.
26455 @item end-stepping-range
26456 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26457 similar CLI command was accomplished.
26458 @item exited-signalled
26459 The inferior exited because of a signal.
26461 The inferior exited.
26462 @item exited-normally
26463 The inferior exited normally.
26464 @item signal-received
26465 A signal was received by the inferior.
26467 The inferior has stopped due to a library being loaded or unloaded.
26468 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26469 set or when a @code{catch load} or @code{catch unload} catchpoint is
26470 in use (@pxref{Set Catchpoints}).
26472 The inferior has forked. This is reported when @code{catch fork}
26473 (@pxref{Set Catchpoints}) has been used.
26475 The inferior has vforked. This is reported in when @code{catch vfork}
26476 (@pxref{Set Catchpoints}) has been used.
26477 @item syscall-entry
26478 The inferior entered a system call. This is reported when @code{catch
26479 syscall} (@pxref{Set Catchpoints}) has been used.
26480 @item syscall-return
26481 The inferior returned from a system call. This is reported when
26482 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26484 The inferior called @code{exec}. This is reported when @code{catch exec}
26485 (@pxref{Set Catchpoints}) has been used.
26488 The @var{id} field identifies the global thread ID of the thread
26489 that directly caused the stop -- for example by hitting a breakpoint.
26490 Depending on whether all-stop
26491 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26492 stop all threads, or only the thread that directly triggered the stop.
26493 If all threads are stopped, the @var{stopped} field will have the
26494 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26495 field will be a list of thread identifiers. Presently, this list will
26496 always include a single thread, but frontend should be prepared to see
26497 several threads in the list. The @var{core} field reports the
26498 processor core on which the stop event has happened. This field may be absent
26499 if such information is not available.
26501 @item =thread-group-added,id="@var{id}"
26502 @itemx =thread-group-removed,id="@var{id}"
26503 A thread group was either added or removed. The @var{id} field
26504 contains the @value{GDBN} identifier of the thread group. When a thread
26505 group is added, it generally might not be associated with a running
26506 process. When a thread group is removed, its id becomes invalid and
26507 cannot be used in any way.
26509 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26510 A thread group became associated with a running program,
26511 either because the program was just started or the thread group
26512 was attached to a program. The @var{id} field contains the
26513 @value{GDBN} identifier of the thread group. The @var{pid} field
26514 contains process identifier, specific to the operating system.
26516 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26517 A thread group is no longer associated with a running program,
26518 either because the program has exited, or because it was detached
26519 from. The @var{id} field contains the @value{GDBN} identifier of the
26520 thread group. The @var{code} field is the exit code of the inferior; it exists
26521 only when the inferior exited with some code.
26523 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26524 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26525 A thread either was created, or has exited. The @var{id} field
26526 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26527 field identifies the thread group this thread belongs to.
26529 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26530 Informs that the selected thread or frame were changed. This notification
26531 is not emitted as result of the @code{-thread-select} or
26532 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26533 that is not documented to change the selected thread and frame actually
26534 changes them. In particular, invoking, directly or indirectly
26535 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26536 will generate this notification. Changing the thread or frame from another
26537 user interface (see @ref{Interpreters}) will also generate this notification.
26539 The @var{frame} field is only present if the newly selected thread is
26540 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
26542 We suggest that in response to this notification, front ends
26543 highlight the selected thread and cause subsequent commands to apply to
26546 @item =library-loaded,...
26547 Reports that a new library file was loaded by the program. This
26548 notification has 4 fields---@var{id}, @var{target-name},
26549 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26550 opaque identifier of the library. For remote debugging case,
26551 @var{target-name} and @var{host-name} fields give the name of the
26552 library file on the target, and on the host respectively. For native
26553 debugging, both those fields have the same value. The
26554 @var{symbols-loaded} field is emitted only for backward compatibility
26555 and should not be relied on to convey any useful information. The
26556 @var{thread-group} field, if present, specifies the id of the thread
26557 group in whose context the library was loaded. If the field is
26558 absent, it means the library was loaded in the context of all present
26561 @item =library-unloaded,...
26562 Reports that a library was unloaded by the program. This notification
26563 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26564 the same meaning as for the @code{=library-loaded} notification.
26565 The @var{thread-group} field, if present, specifies the id of the
26566 thread group in whose context the library was unloaded. If the field is
26567 absent, it means the library was unloaded in the context of all present
26570 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26571 @itemx =traceframe-changed,end
26572 Reports that the trace frame was changed and its new number is
26573 @var{tfnum}. The number of the tracepoint associated with this trace
26574 frame is @var{tpnum}.
26576 @item =tsv-created,name=@var{name},initial=@var{initial}
26577 Reports that the new trace state variable @var{name} is created with
26578 initial value @var{initial}.
26580 @item =tsv-deleted,name=@var{name}
26581 @itemx =tsv-deleted
26582 Reports that the trace state variable @var{name} is deleted or all
26583 trace state variables are deleted.
26585 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26586 Reports that the trace state variable @var{name} is modified with
26587 the initial value @var{initial}. The current value @var{current} of
26588 trace state variable is optional and is reported if the current
26589 value of trace state variable is known.
26591 @item =breakpoint-created,bkpt=@{...@}
26592 @itemx =breakpoint-modified,bkpt=@{...@}
26593 @itemx =breakpoint-deleted,id=@var{number}
26594 Reports that a breakpoint was created, modified, or deleted,
26595 respectively. Only user-visible breakpoints are reported to the MI
26598 The @var{bkpt} argument is of the same form as returned by the various
26599 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26600 @var{number} is the ordinal number of the breakpoint.
26602 Note that if a breakpoint is emitted in the result record of a
26603 command, then it will not also be emitted in an async record.
26605 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26606 @itemx =record-stopped,thread-group="@var{id}"
26607 Execution log recording was either started or stopped on an
26608 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26609 group corresponding to the affected inferior.
26611 The @var{method} field indicates the method used to record execution. If the
26612 method in use supports multiple recording formats, @var{format} will be present
26613 and contain the currently used format. @xref{Process Record and Replay},
26614 for existing method and format values.
26616 @item =cmd-param-changed,param=@var{param},value=@var{value}
26617 Reports that a parameter of the command @code{set @var{param}} is
26618 changed to @var{value}. In the multi-word @code{set} command,
26619 the @var{param} is the whole parameter list to @code{set} command.
26620 For example, In command @code{set check type on}, @var{param}
26621 is @code{check type} and @var{value} is @code{on}.
26623 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26624 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26625 written in an inferior. The @var{id} is the identifier of the
26626 thread group corresponding to the affected inferior. The optional
26627 @code{type="code"} part is reported if the memory written to holds
26631 @node GDB/MI Breakpoint Information
26632 @subsection @sc{gdb/mi} Breakpoint Information
26634 When @value{GDBN} reports information about a breakpoint, a
26635 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26640 The breakpoint number. For a breakpoint that represents one location
26641 of a multi-location breakpoint, this will be a dotted pair, like
26645 The type of the breakpoint. For ordinary breakpoints this will be
26646 @samp{breakpoint}, but many values are possible.
26649 If the type of the breakpoint is @samp{catchpoint}, then this
26650 indicates the exact type of catchpoint.
26653 This is the breakpoint disposition---either @samp{del}, meaning that
26654 the breakpoint will be deleted at the next stop, or @samp{keep},
26655 meaning that the breakpoint will not be deleted.
26658 This indicates whether the breakpoint is enabled, in which case the
26659 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26660 Note that this is not the same as the field @code{enable}.
26663 The address of the breakpoint. This may be a hexidecimal number,
26664 giving the address; or the string @samp{<PENDING>}, for a pending
26665 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26666 multiple locations. This field will not be present if no address can
26667 be determined. For example, a watchpoint does not have an address.
26670 If known, the function in which the breakpoint appears.
26671 If not known, this field is not present.
26674 The name of the source file which contains this function, if known.
26675 If not known, this field is not present.
26678 The full file name of the source file which contains this function, if
26679 known. If not known, this field is not present.
26682 The line number at which this breakpoint appears, if known.
26683 If not known, this field is not present.
26686 If the source file is not known, this field may be provided. If
26687 provided, this holds the address of the breakpoint, possibly followed
26691 If this breakpoint is pending, this field is present and holds the
26692 text used to set the breakpoint, as entered by the user.
26695 Where this breakpoint's condition is evaluated, either @samp{host} or
26699 If this is a thread-specific breakpoint, then this identifies the
26700 thread in which the breakpoint can trigger.
26703 If this breakpoint is restricted to a particular Ada task, then this
26704 field will hold the task identifier.
26707 If the breakpoint is conditional, this is the condition expression.
26710 The ignore count of the breakpoint.
26713 The enable count of the breakpoint.
26715 @item traceframe-usage
26718 @item static-tracepoint-marker-string-id
26719 For a static tracepoint, the name of the static tracepoint marker.
26722 For a masked watchpoint, this is the mask.
26725 A tracepoint's pass count.
26727 @item original-location
26728 The location of the breakpoint as originally specified by the user.
26729 This field is optional.
26732 The number of times the breakpoint has been hit.
26735 This field is only given for tracepoints. This is either @samp{y},
26736 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26740 Some extra data, the exact contents of which are type-dependent.
26744 For example, here is what the output of @code{-break-insert}
26745 (@pxref{GDB/MI Breakpoint Commands}) might be:
26748 -> -break-insert main
26749 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26750 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26751 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26756 @node GDB/MI Frame Information
26757 @subsection @sc{gdb/mi} Frame Information
26759 Response from many MI commands includes an information about stack
26760 frame. This information is a tuple that may have the following
26765 The level of the stack frame. The innermost frame has the level of
26766 zero. This field is always present.
26769 The name of the function corresponding to the frame. This field may
26770 be absent if @value{GDBN} is unable to determine the function name.
26773 The code address for the frame. This field is always present.
26776 The name of the source files that correspond to the frame's code
26777 address. This field may be absent.
26780 The source line corresponding to the frames' code address. This field
26784 The name of the binary file (either executable or shared library) the
26785 corresponds to the frame's code address. This field may be absent.
26789 @node GDB/MI Thread Information
26790 @subsection @sc{gdb/mi} Thread Information
26792 Whenever @value{GDBN} has to report an information about a thread, it
26793 uses a tuple with the following fields:
26797 The global numeric id assigned to the thread by @value{GDBN}. This field is
26801 Target-specific string identifying the thread. This field is always present.
26804 Additional information about the thread provided by the target.
26805 It is supposed to be human-readable and not interpreted by the
26806 frontend. This field is optional.
26809 Either @samp{stopped} or @samp{running}, depending on whether the
26810 thread is presently running. This field is always present.
26813 The value of this field is an integer number of the processor core the
26814 thread was last seen on. This field is optional.
26817 @node GDB/MI Ada Exception Information
26818 @subsection @sc{gdb/mi} Ada Exception Information
26820 Whenever a @code{*stopped} record is emitted because the program
26821 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26822 @value{GDBN} provides the name of the exception that was raised via
26823 the @code{exception-name} field.
26825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26826 @node GDB/MI Simple Examples
26827 @section Simple Examples of @sc{gdb/mi} Interaction
26828 @cindex @sc{gdb/mi}, simple examples
26830 This subsection presents several simple examples of interaction using
26831 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26832 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26833 the output received from @sc{gdb/mi}.
26835 Note the line breaks shown in the examples are here only for
26836 readability, they don't appear in the real output.
26838 @subheading Setting a Breakpoint
26840 Setting a breakpoint generates synchronous output which contains detailed
26841 information of the breakpoint.
26844 -> -break-insert main
26845 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26846 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26847 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26852 @subheading Program Execution
26854 Program execution generates asynchronous records and MI gives the
26855 reason that execution stopped.
26861 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26862 frame=@{addr="0x08048564",func="main",
26863 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26864 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26869 <- *stopped,reason="exited-normally"
26873 @subheading Quitting @value{GDBN}
26875 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26883 Please note that @samp{^exit} is printed immediately, but it might
26884 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26885 performs necessary cleanups, including killing programs being debugged
26886 or disconnecting from debug hardware, so the frontend should wait till
26887 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26888 fails to exit in reasonable time.
26890 @subheading A Bad Command
26892 Here's what happens if you pass a non-existent command:
26896 <- ^error,msg="Undefined MI command: rubbish"
26901 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26902 @node GDB/MI Command Description Format
26903 @section @sc{gdb/mi} Command Description Format
26905 The remaining sections describe blocks of commands. Each block of
26906 commands is laid out in a fashion similar to this section.
26908 @subheading Motivation
26910 The motivation for this collection of commands.
26912 @subheading Introduction
26914 A brief introduction to this collection of commands as a whole.
26916 @subheading Commands
26918 For each command in the block, the following is described:
26920 @subsubheading Synopsis
26923 -command @var{args}@dots{}
26926 @subsubheading Result
26928 @subsubheading @value{GDBN} Command
26930 The corresponding @value{GDBN} CLI command(s), if any.
26932 @subsubheading Example
26934 Example(s) formatted for readability. Some of the described commands have
26935 not been implemented yet and these are labeled N.A.@: (not available).
26938 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26939 @node GDB/MI Breakpoint Commands
26940 @section @sc{gdb/mi} Breakpoint Commands
26942 @cindex breakpoint commands for @sc{gdb/mi}
26943 @cindex @sc{gdb/mi}, breakpoint commands
26944 This section documents @sc{gdb/mi} commands for manipulating
26947 @subheading The @code{-break-after} Command
26948 @findex -break-after
26950 @subsubheading Synopsis
26953 -break-after @var{number} @var{count}
26956 The breakpoint number @var{number} is not in effect until it has been
26957 hit @var{count} times. To see how this is reflected in the output of
26958 the @samp{-break-list} command, see the description of the
26959 @samp{-break-list} command below.
26961 @subsubheading @value{GDBN} Command
26963 The corresponding @value{GDBN} command is @samp{ignore}.
26965 @subsubheading Example
26970 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26971 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26972 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26980 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26981 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26982 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26983 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26984 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26985 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26986 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26987 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26988 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26989 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26994 @subheading The @code{-break-catch} Command
26995 @findex -break-catch
26998 @subheading The @code{-break-commands} Command
26999 @findex -break-commands
27001 @subsubheading Synopsis
27004 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27007 Specifies the CLI commands that should be executed when breakpoint
27008 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27009 are the commands. If no command is specified, any previously-set
27010 commands are cleared. @xref{Break Commands}. Typical use of this
27011 functionality is tracing a program, that is, printing of values of
27012 some variables whenever breakpoint is hit and then continuing.
27014 @subsubheading @value{GDBN} Command
27016 The corresponding @value{GDBN} command is @samp{commands}.
27018 @subsubheading Example
27023 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27024 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27025 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27028 -break-commands 1 "print v" "continue"
27033 @subheading The @code{-break-condition} Command
27034 @findex -break-condition
27036 @subsubheading Synopsis
27039 -break-condition @var{number} @var{expr}
27042 Breakpoint @var{number} will stop the program only if the condition in
27043 @var{expr} is true. The condition becomes part of the
27044 @samp{-break-list} output (see the description of the @samp{-break-list}
27047 @subsubheading @value{GDBN} Command
27049 The corresponding @value{GDBN} command is @samp{condition}.
27051 @subsubheading Example
27055 -break-condition 1 1
27059 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27060 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27061 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27062 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27063 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27064 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27065 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27066 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27067 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27068 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27072 @subheading The @code{-break-delete} Command
27073 @findex -break-delete
27075 @subsubheading Synopsis
27078 -break-delete ( @var{breakpoint} )+
27081 Delete the breakpoint(s) whose number(s) are specified in the argument
27082 list. This is obviously reflected in the breakpoint list.
27084 @subsubheading @value{GDBN} Command
27086 The corresponding @value{GDBN} command is @samp{delete}.
27088 @subsubheading Example
27096 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27097 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27098 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27099 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27100 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27101 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27102 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27107 @subheading The @code{-break-disable} Command
27108 @findex -break-disable
27110 @subsubheading Synopsis
27113 -break-disable ( @var{breakpoint} )+
27116 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27117 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27119 @subsubheading @value{GDBN} Command
27121 The corresponding @value{GDBN} command is @samp{disable}.
27123 @subsubheading Example
27131 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27132 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27133 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27134 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27135 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27136 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27137 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27138 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27139 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27140 line="5",thread-groups=["i1"],times="0"@}]@}
27144 @subheading The @code{-break-enable} Command
27145 @findex -break-enable
27147 @subsubheading Synopsis
27150 -break-enable ( @var{breakpoint} )+
27153 Enable (previously disabled) @var{breakpoint}(s).
27155 @subsubheading @value{GDBN} Command
27157 The corresponding @value{GDBN} command is @samp{enable}.
27159 @subsubheading Example
27167 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27168 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27169 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27170 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27171 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27172 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27173 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27174 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27175 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27176 line="5",thread-groups=["i1"],times="0"@}]@}
27180 @subheading The @code{-break-info} Command
27181 @findex -break-info
27183 @subsubheading Synopsis
27186 -break-info @var{breakpoint}
27190 Get information about a single breakpoint.
27192 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27193 Information}, for details on the format of each breakpoint in the
27196 @subsubheading @value{GDBN} Command
27198 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27200 @subsubheading Example
27203 @subheading The @code{-break-insert} Command
27204 @findex -break-insert
27205 @anchor{-break-insert}
27207 @subsubheading Synopsis
27210 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27211 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27212 [ -p @var{thread-id} ] [ @var{location} ]
27216 If specified, @var{location}, can be one of:
27219 @item linespec location
27220 A linespec location. @xref{Linespec Locations}.
27222 @item explicit location
27223 An explicit location. @sc{gdb/mi} explicit locations are
27224 analogous to the CLI's explicit locations using the option names
27225 listed below. @xref{Explicit Locations}.
27228 @item --source @var{filename}
27229 The source file name of the location. This option requires the use
27230 of either @samp{--function} or @samp{--line}.
27232 @item --function @var{function}
27233 The name of a function or method.
27235 @item --label @var{label}
27236 The name of a label.
27238 @item --line @var{lineoffset}
27239 An absolute or relative line offset from the start of the location.
27242 @item address location
27243 An address location, *@var{address}. @xref{Address Locations}.
27247 The possible optional parameters of this command are:
27251 Insert a temporary breakpoint.
27253 Insert a hardware breakpoint.
27255 If @var{location} cannot be parsed (for example if it
27256 refers to unknown files or functions), create a pending
27257 breakpoint. Without this flag, @value{GDBN} will report
27258 an error, and won't create a breakpoint, if @var{location}
27261 Create a disabled breakpoint.
27263 Create a tracepoint. @xref{Tracepoints}. When this parameter
27264 is used together with @samp{-h}, a fast tracepoint is created.
27265 @item -c @var{condition}
27266 Make the breakpoint conditional on @var{condition}.
27267 @item -i @var{ignore-count}
27268 Initialize the @var{ignore-count}.
27269 @item -p @var{thread-id}
27270 Restrict the breakpoint to the thread with the specified global
27274 @subsubheading Result
27276 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27277 resulting breakpoint.
27279 Note: this format is open to change.
27280 @c An out-of-band breakpoint instead of part of the result?
27282 @subsubheading @value{GDBN} Command
27284 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27285 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27287 @subsubheading Example
27292 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27293 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27296 -break-insert -t foo
27297 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27298 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27302 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27303 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27304 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27305 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27306 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27307 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27308 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27309 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27310 addr="0x0001072c", func="main",file="recursive2.c",
27311 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27313 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27314 addr="0x00010774",func="foo",file="recursive2.c",
27315 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27318 @c -break-insert -r foo.*
27319 @c ~int foo(int, int);
27320 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27321 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27326 @subheading The @code{-dprintf-insert} Command
27327 @findex -dprintf-insert
27329 @subsubheading Synopsis
27332 -dprintf-insert [ -t ] [ -f ] [ -d ]
27333 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27334 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27339 If supplied, @var{location} may be specified the same way as for
27340 the @code{-break-insert} command. @xref{-break-insert}.
27342 The possible optional parameters of this command are:
27346 Insert a temporary breakpoint.
27348 If @var{location} cannot be parsed (for example, if it
27349 refers to unknown files or functions), create a pending
27350 breakpoint. Without this flag, @value{GDBN} will report
27351 an error, and won't create a breakpoint, if @var{location}
27354 Create a disabled breakpoint.
27355 @item -c @var{condition}
27356 Make the breakpoint conditional on @var{condition}.
27357 @item -i @var{ignore-count}
27358 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27359 to @var{ignore-count}.
27360 @item -p @var{thread-id}
27361 Restrict the breakpoint to the thread with the specified global
27365 @subsubheading Result
27367 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27368 resulting breakpoint.
27370 @c An out-of-band breakpoint instead of part of the result?
27372 @subsubheading @value{GDBN} Command
27374 The corresponding @value{GDBN} command is @samp{dprintf}.
27376 @subsubheading Example
27380 4-dprintf-insert foo "At foo entry\n"
27381 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27382 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27383 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27384 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27385 original-location="foo"@}
27387 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27388 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27389 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27390 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27391 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27392 original-location="mi-dprintf.c:26"@}
27396 @subheading The @code{-break-list} Command
27397 @findex -break-list
27399 @subsubheading Synopsis
27405 Displays the list of inserted breakpoints, showing the following fields:
27409 number of the breakpoint
27411 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27413 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27416 is the breakpoint enabled or no: @samp{y} or @samp{n}
27418 memory location at which the breakpoint is set
27420 logical location of the breakpoint, expressed by function name, file
27422 @item Thread-groups
27423 list of thread groups to which this breakpoint applies
27425 number of times the breakpoint has been hit
27428 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27429 @code{body} field is an empty list.
27431 @subsubheading @value{GDBN} Command
27433 The corresponding @value{GDBN} command is @samp{info break}.
27435 @subsubheading Example
27440 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27441 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27442 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27443 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27444 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27445 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27446 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27447 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27448 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27450 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27451 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27452 line="13",thread-groups=["i1"],times="0"@}]@}
27456 Here's an example of the result when there are no breakpoints:
27461 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27462 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27463 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27464 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27465 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27466 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27467 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27472 @subheading The @code{-break-passcount} Command
27473 @findex -break-passcount
27475 @subsubheading Synopsis
27478 -break-passcount @var{tracepoint-number} @var{passcount}
27481 Set the passcount for tracepoint @var{tracepoint-number} to
27482 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27483 is not a tracepoint, error is emitted. This corresponds to CLI
27484 command @samp{passcount}.
27486 @subheading The @code{-break-watch} Command
27487 @findex -break-watch
27489 @subsubheading Synopsis
27492 -break-watch [ -a | -r ]
27495 Create a watchpoint. With the @samp{-a} option it will create an
27496 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27497 read from or on a write to the memory location. With the @samp{-r}
27498 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27499 trigger only when the memory location is accessed for reading. Without
27500 either of the options, the watchpoint created is a regular watchpoint,
27501 i.e., it will trigger when the memory location is accessed for writing.
27502 @xref{Set Watchpoints, , Setting Watchpoints}.
27504 Note that @samp{-break-list} will report a single list of watchpoints and
27505 breakpoints inserted.
27507 @subsubheading @value{GDBN} Command
27509 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27512 @subsubheading Example
27514 Setting a watchpoint on a variable in the @code{main} function:
27519 ^done,wpt=@{number="2",exp="x"@}
27524 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27525 value=@{old="-268439212",new="55"@},
27526 frame=@{func="main",args=[],file="recursive2.c",
27527 fullname="/home/foo/bar/recursive2.c",line="5"@}
27531 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27532 the program execution twice: first for the variable changing value, then
27533 for the watchpoint going out of scope.
27538 ^done,wpt=@{number="5",exp="C"@}
27543 *stopped,reason="watchpoint-trigger",
27544 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27545 frame=@{func="callee4",args=[],
27546 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27547 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27552 *stopped,reason="watchpoint-scope",wpnum="5",
27553 frame=@{func="callee3",args=[@{name="strarg",
27554 value="0x11940 \"A string argument.\""@}],
27555 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27556 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27560 Listing breakpoints and watchpoints, at different points in the program
27561 execution. Note that once the watchpoint goes out of scope, it is
27567 ^done,wpt=@{number="2",exp="C"@}
27570 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27571 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27572 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27573 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27574 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27575 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27576 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27577 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27578 addr="0x00010734",func="callee4",
27579 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27580 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27582 bkpt=@{number="2",type="watchpoint",disp="keep",
27583 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27588 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27589 value=@{old="-276895068",new="3"@},
27590 frame=@{func="callee4",args=[],
27591 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27592 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27595 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27596 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27597 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27598 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27599 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27600 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27601 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27602 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27603 addr="0x00010734",func="callee4",
27604 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27605 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27607 bkpt=@{number="2",type="watchpoint",disp="keep",
27608 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27612 ^done,reason="watchpoint-scope",wpnum="2",
27613 frame=@{func="callee3",args=[@{name="strarg",
27614 value="0x11940 \"A string argument.\""@}],
27615 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27616 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27619 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27620 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27621 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27622 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27623 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27624 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27625 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27626 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27627 addr="0x00010734",func="callee4",
27628 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27629 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27630 thread-groups=["i1"],times="1"@}]@}
27635 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27636 @node GDB/MI Catchpoint Commands
27637 @section @sc{gdb/mi} Catchpoint Commands
27639 This section documents @sc{gdb/mi} commands for manipulating
27643 * Shared Library GDB/MI Catchpoint Commands::
27644 * Ada Exception GDB/MI Catchpoint Commands::
27647 @node Shared Library GDB/MI Catchpoint Commands
27648 @subsection Shared Library @sc{gdb/mi} Catchpoints
27650 @subheading The @code{-catch-load} Command
27651 @findex -catch-load
27653 @subsubheading Synopsis
27656 -catch-load [ -t ] [ -d ] @var{regexp}
27659 Add a catchpoint for library load events. If the @samp{-t} option is used,
27660 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27661 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27662 in a disabled state. The @samp{regexp} argument is a regular
27663 expression used to match the name of the loaded library.
27666 @subsubheading @value{GDBN} Command
27668 The corresponding @value{GDBN} command is @samp{catch load}.
27670 @subsubheading Example
27673 -catch-load -t foo.so
27674 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27675 what="load of library matching foo.so",catch-type="load",times="0"@}
27680 @subheading The @code{-catch-unload} Command
27681 @findex -catch-unload
27683 @subsubheading Synopsis
27686 -catch-unload [ -t ] [ -d ] @var{regexp}
27689 Add a catchpoint for library unload events. If the @samp{-t} option is
27690 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27691 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27692 created in a disabled state. The @samp{regexp} argument is a regular
27693 expression used to match the name of the unloaded library.
27695 @subsubheading @value{GDBN} Command
27697 The corresponding @value{GDBN} command is @samp{catch unload}.
27699 @subsubheading Example
27702 -catch-unload -d bar.so
27703 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27704 what="load of library matching bar.so",catch-type="unload",times="0"@}
27708 @node Ada Exception GDB/MI Catchpoint Commands
27709 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27711 The following @sc{gdb/mi} commands can be used to create catchpoints
27712 that stop the execution when Ada exceptions are being raised.
27714 @subheading The @code{-catch-assert} Command
27715 @findex -catch-assert
27717 @subsubheading Synopsis
27720 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27723 Add a catchpoint for failed Ada assertions.
27725 The possible optional parameters for this command are:
27728 @item -c @var{condition}
27729 Make the catchpoint conditional on @var{condition}.
27731 Create a disabled catchpoint.
27733 Create a temporary catchpoint.
27736 @subsubheading @value{GDBN} Command
27738 The corresponding @value{GDBN} command is @samp{catch assert}.
27740 @subsubheading Example
27744 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27745 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27746 thread-groups=["i1"],times="0",
27747 original-location="__gnat_debug_raise_assert_failure"@}
27751 @subheading The @code{-catch-exception} Command
27752 @findex -catch-exception
27754 @subsubheading Synopsis
27757 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27761 Add a catchpoint stopping when Ada exceptions are raised.
27762 By default, the command stops the program when any Ada exception
27763 gets raised. But it is also possible, by using some of the
27764 optional parameters described below, to create more selective
27767 The possible optional parameters for this command are:
27770 @item -c @var{condition}
27771 Make the catchpoint conditional on @var{condition}.
27773 Create a disabled catchpoint.
27774 @item -e @var{exception-name}
27775 Only stop when @var{exception-name} is raised. This option cannot
27776 be used combined with @samp{-u}.
27778 Create a temporary catchpoint.
27780 Stop only when an unhandled exception gets raised. This option
27781 cannot be used combined with @samp{-e}.
27784 @subsubheading @value{GDBN} Command
27786 The corresponding @value{GDBN} commands are @samp{catch exception}
27787 and @samp{catch exception unhandled}.
27789 @subsubheading Example
27792 -catch-exception -e Program_Error
27793 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27794 enabled="y",addr="0x0000000000404874",
27795 what="`Program_Error' Ada exception", thread-groups=["i1"],
27796 times="0",original-location="__gnat_debug_raise_exception"@}
27800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27801 @node GDB/MI Program Context
27802 @section @sc{gdb/mi} Program Context
27804 @subheading The @code{-exec-arguments} Command
27805 @findex -exec-arguments
27808 @subsubheading Synopsis
27811 -exec-arguments @var{args}
27814 Set the inferior program arguments, to be used in the next
27817 @subsubheading @value{GDBN} Command
27819 The corresponding @value{GDBN} command is @samp{set args}.
27821 @subsubheading Example
27825 -exec-arguments -v word
27832 @subheading The @code{-exec-show-arguments} Command
27833 @findex -exec-show-arguments
27835 @subsubheading Synopsis
27838 -exec-show-arguments
27841 Print the arguments of the program.
27843 @subsubheading @value{GDBN} Command
27845 The corresponding @value{GDBN} command is @samp{show args}.
27847 @subsubheading Example
27852 @subheading The @code{-environment-cd} Command
27853 @findex -environment-cd
27855 @subsubheading Synopsis
27858 -environment-cd @var{pathdir}
27861 Set @value{GDBN}'s working directory.
27863 @subsubheading @value{GDBN} Command
27865 The corresponding @value{GDBN} command is @samp{cd}.
27867 @subsubheading Example
27871 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27877 @subheading The @code{-environment-directory} Command
27878 @findex -environment-directory
27880 @subsubheading Synopsis
27883 -environment-directory [ -r ] [ @var{pathdir} ]+
27886 Add directories @var{pathdir} to beginning of search path for source files.
27887 If the @samp{-r} option is used, the search path is reset to the default
27888 search path. If directories @var{pathdir} are supplied in addition to the
27889 @samp{-r} option, the search path is first reset and then addition
27891 Multiple directories may be specified, separated by blanks. Specifying
27892 multiple directories in a single command
27893 results in the directories added to the beginning of the
27894 search path in the same order they were presented in the command.
27895 If blanks are needed as
27896 part of a directory name, double-quotes should be used around
27897 the name. In the command output, the path will show up separated
27898 by the system directory-separator character. The directory-separator
27899 character must not be used
27900 in any directory name.
27901 If no directories are specified, the current search path is displayed.
27903 @subsubheading @value{GDBN} Command
27905 The corresponding @value{GDBN} command is @samp{dir}.
27907 @subsubheading Example
27911 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27912 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27914 -environment-directory ""
27915 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27917 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27918 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27920 -environment-directory -r
27921 ^done,source-path="$cdir:$cwd"
27926 @subheading The @code{-environment-path} Command
27927 @findex -environment-path
27929 @subsubheading Synopsis
27932 -environment-path [ -r ] [ @var{pathdir} ]+
27935 Add directories @var{pathdir} to beginning of search path for object files.
27936 If the @samp{-r} option is used, the search path is reset to the original
27937 search path that existed at gdb start-up. If directories @var{pathdir} are
27938 supplied in addition to the
27939 @samp{-r} option, the search path is first reset and then addition
27941 Multiple directories may be specified, separated by blanks. Specifying
27942 multiple directories in a single command
27943 results in the directories added to the beginning of the
27944 search path in the same order they were presented in the command.
27945 If blanks are needed as
27946 part of a directory name, double-quotes should be used around
27947 the name. In the command output, the path will show up separated
27948 by the system directory-separator character. The directory-separator
27949 character must not be used
27950 in any directory name.
27951 If no directories are specified, the current path is displayed.
27954 @subsubheading @value{GDBN} Command
27956 The corresponding @value{GDBN} command is @samp{path}.
27958 @subsubheading Example
27963 ^done,path="/usr/bin"
27965 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27966 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27968 -environment-path -r /usr/local/bin
27969 ^done,path="/usr/local/bin:/usr/bin"
27974 @subheading The @code{-environment-pwd} Command
27975 @findex -environment-pwd
27977 @subsubheading Synopsis
27983 Show the current working directory.
27985 @subsubheading @value{GDBN} Command
27987 The corresponding @value{GDBN} command is @samp{pwd}.
27989 @subsubheading Example
27994 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27999 @node GDB/MI Thread Commands
28000 @section @sc{gdb/mi} Thread Commands
28003 @subheading The @code{-thread-info} Command
28004 @findex -thread-info
28006 @subsubheading Synopsis
28009 -thread-info [ @var{thread-id} ]
28012 Reports information about either a specific thread, if the
28013 @var{thread-id} parameter is present, or about all threads.
28014 @var{thread-id} is the thread's global thread ID. When printing
28015 information about all threads, also reports the global ID of the
28018 @subsubheading @value{GDBN} Command
28020 The @samp{info thread} command prints the same information
28023 @subsubheading Result
28025 The result is a list of threads. The following attributes are
28026 defined for a given thread:
28030 This field exists only for the current thread. It has the value @samp{*}.
28033 The global identifier that @value{GDBN} uses to refer to the thread.
28036 The identifier that the target uses to refer to the thread.
28039 Extra information about the thread, in a target-specific format. This
28043 The name of the thread. If the user specified a name using the
28044 @code{thread name} command, then this name is given. Otherwise, if
28045 @value{GDBN} can extract the thread name from the target, then that
28046 name is given. If @value{GDBN} cannot find the thread name, then this
28050 The stack frame currently executing in the thread.
28053 The thread's state. The @samp{state} field may have the following
28058 The thread is stopped. Frame information is available for stopped
28062 The thread is running. There's no frame information for running
28068 If @value{GDBN} can find the CPU core on which this thread is running,
28069 then this field is the core identifier. This field is optional.
28073 @subsubheading Example
28078 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28079 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28080 args=[]@},state="running"@},
28081 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28082 frame=@{level="0",addr="0x0804891f",func="foo",
28083 args=[@{name="i",value="10"@}],
28084 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28085 state="running"@}],
28086 current-thread-id="1"
28090 @subheading The @code{-thread-list-ids} Command
28091 @findex -thread-list-ids
28093 @subsubheading Synopsis
28099 Produces a list of the currently known global @value{GDBN} thread ids.
28100 At the end of the list it also prints the total number of such
28103 This command is retained for historical reasons, the
28104 @code{-thread-info} command should be used instead.
28106 @subsubheading @value{GDBN} Command
28108 Part of @samp{info threads} supplies the same information.
28110 @subsubheading Example
28115 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28116 current-thread-id="1",number-of-threads="3"
28121 @subheading The @code{-thread-select} Command
28122 @findex -thread-select
28124 @subsubheading Synopsis
28127 -thread-select @var{thread-id}
28130 Make thread with global thread number @var{thread-id} the current
28131 thread. It prints the number of the new current thread, and the
28132 topmost frame for that thread.
28134 This command is deprecated in favor of explicitly using the
28135 @samp{--thread} option to each command.
28137 @subsubheading @value{GDBN} Command
28139 The corresponding @value{GDBN} command is @samp{thread}.
28141 @subsubheading Example
28148 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28149 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28153 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28154 number-of-threads="3"
28157 ^done,new-thread-id="3",
28158 frame=@{level="0",func="vprintf",
28159 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28160 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28164 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28165 @node GDB/MI Ada Tasking Commands
28166 @section @sc{gdb/mi} Ada Tasking Commands
28168 @subheading The @code{-ada-task-info} Command
28169 @findex -ada-task-info
28171 @subsubheading Synopsis
28174 -ada-task-info [ @var{task-id} ]
28177 Reports information about either a specific Ada task, if the
28178 @var{task-id} parameter is present, or about all Ada tasks.
28180 @subsubheading @value{GDBN} Command
28182 The @samp{info tasks} command prints the same information
28183 about all Ada tasks (@pxref{Ada Tasks}).
28185 @subsubheading Result
28187 The result is a table of Ada tasks. The following columns are
28188 defined for each Ada task:
28192 This field exists only for the current thread. It has the value @samp{*}.
28195 The identifier that @value{GDBN} uses to refer to the Ada task.
28198 The identifier that the target uses to refer to the Ada task.
28201 The global thread identifier of the thread corresponding to the Ada
28204 This field should always exist, as Ada tasks are always implemented
28205 on top of a thread. But if @value{GDBN} cannot find this corresponding
28206 thread for any reason, the field is omitted.
28209 This field exists only when the task was created by another task.
28210 In this case, it provides the ID of the parent task.
28213 The base priority of the task.
28216 The current state of the task. For a detailed description of the
28217 possible states, see @ref{Ada Tasks}.
28220 The name of the task.
28224 @subsubheading Example
28228 ^done,tasks=@{nr_rows="3",nr_cols="8",
28229 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28230 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28231 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28232 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28233 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28234 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28235 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28236 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28237 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28238 state="Child Termination Wait",name="main_task"@}]@}
28242 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28243 @node GDB/MI Program Execution
28244 @section @sc{gdb/mi} Program Execution
28246 These are the asynchronous commands which generate the out-of-band
28247 record @samp{*stopped}. Currently @value{GDBN} only really executes
28248 asynchronously with remote targets and this interaction is mimicked in
28251 @subheading The @code{-exec-continue} Command
28252 @findex -exec-continue
28254 @subsubheading Synopsis
28257 -exec-continue [--reverse] [--all|--thread-group N]
28260 Resumes the execution of the inferior program, which will continue
28261 to execute until it reaches a debugger stop event. If the
28262 @samp{--reverse} option is specified, execution resumes in reverse until
28263 it reaches a stop event. Stop events may include
28266 breakpoints or watchpoints
28268 signals or exceptions
28270 the end of the process (or its beginning under @samp{--reverse})
28272 the end or beginning of a replay log if one is being used.
28274 In all-stop mode (@pxref{All-Stop
28275 Mode}), may resume only one thread, or all threads, depending on the
28276 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28277 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28278 ignored in all-stop mode. If the @samp{--thread-group} options is
28279 specified, then all threads in that thread group are resumed.
28281 @subsubheading @value{GDBN} Command
28283 The corresponding @value{GDBN} corresponding is @samp{continue}.
28285 @subsubheading Example
28292 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28293 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28299 @subheading The @code{-exec-finish} Command
28300 @findex -exec-finish
28302 @subsubheading Synopsis
28305 -exec-finish [--reverse]
28308 Resumes the execution of the inferior program until the current
28309 function is exited. Displays the results returned by the function.
28310 If the @samp{--reverse} option is specified, resumes the reverse
28311 execution of the inferior program until the point where current
28312 function was called.
28314 @subsubheading @value{GDBN} Command
28316 The corresponding @value{GDBN} command is @samp{finish}.
28318 @subsubheading Example
28320 Function returning @code{void}.
28327 *stopped,reason="function-finished",frame=@{func="main",args=[],
28328 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28332 Function returning other than @code{void}. The name of the internal
28333 @value{GDBN} variable storing the result is printed, together with the
28340 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28341 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28342 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28343 gdb-result-var="$1",return-value="0"
28348 @subheading The @code{-exec-interrupt} Command
28349 @findex -exec-interrupt
28351 @subsubheading Synopsis
28354 -exec-interrupt [--all|--thread-group N]
28357 Interrupts the background execution of the target. Note how the token
28358 associated with the stop message is the one for the execution command
28359 that has been interrupted. The token for the interrupt itself only
28360 appears in the @samp{^done} output. If the user is trying to
28361 interrupt a non-running program, an error message will be printed.
28363 Note that when asynchronous execution is enabled, this command is
28364 asynchronous just like other execution commands. That is, first the
28365 @samp{^done} response will be printed, and the target stop will be
28366 reported after that using the @samp{*stopped} notification.
28368 In non-stop mode, only the context thread is interrupted by default.
28369 All threads (in all inferiors) will be interrupted if the
28370 @samp{--all} option is specified. If the @samp{--thread-group}
28371 option is specified, all threads in that group will be interrupted.
28373 @subsubheading @value{GDBN} Command
28375 The corresponding @value{GDBN} command is @samp{interrupt}.
28377 @subsubheading Example
28388 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28389 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28390 fullname="/home/foo/bar/try.c",line="13"@}
28395 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28399 @subheading The @code{-exec-jump} Command
28402 @subsubheading Synopsis
28405 -exec-jump @var{location}
28408 Resumes execution of the inferior program at the location specified by
28409 parameter. @xref{Specify Location}, for a description of the
28410 different forms of @var{location}.
28412 @subsubheading @value{GDBN} Command
28414 The corresponding @value{GDBN} command is @samp{jump}.
28416 @subsubheading Example
28419 -exec-jump foo.c:10
28420 *running,thread-id="all"
28425 @subheading The @code{-exec-next} Command
28428 @subsubheading Synopsis
28431 -exec-next [--reverse]
28434 Resumes execution of the inferior program, stopping when the beginning
28435 of the next source line is reached.
28437 If the @samp{--reverse} option is specified, resumes reverse execution
28438 of the inferior program, stopping at the beginning of the previous
28439 source line. If you issue this command on the first line of a
28440 function, it will take you back to the caller of that function, to the
28441 source line where the function was called.
28444 @subsubheading @value{GDBN} Command
28446 The corresponding @value{GDBN} command is @samp{next}.
28448 @subsubheading Example
28454 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28459 @subheading The @code{-exec-next-instruction} Command
28460 @findex -exec-next-instruction
28462 @subsubheading Synopsis
28465 -exec-next-instruction [--reverse]
28468 Executes one machine instruction. If the instruction is a function
28469 call, continues until the function returns. If the program stops at an
28470 instruction in the middle of a source line, the address will be
28473 If the @samp{--reverse} option is specified, resumes reverse execution
28474 of the inferior program, stopping at the previous instruction. If the
28475 previously executed instruction was a return from another function,
28476 it will continue to execute in reverse until the call to that function
28477 (from the current stack frame) is reached.
28479 @subsubheading @value{GDBN} Command
28481 The corresponding @value{GDBN} command is @samp{nexti}.
28483 @subsubheading Example
28487 -exec-next-instruction
28491 *stopped,reason="end-stepping-range",
28492 addr="0x000100d4",line="5",file="hello.c"
28497 @subheading The @code{-exec-return} Command
28498 @findex -exec-return
28500 @subsubheading Synopsis
28506 Makes current function return immediately. Doesn't execute the inferior.
28507 Displays the new current frame.
28509 @subsubheading @value{GDBN} Command
28511 The corresponding @value{GDBN} command is @samp{return}.
28513 @subsubheading Example
28517 200-break-insert callee4
28518 200^done,bkpt=@{number="1",addr="0x00010734",
28519 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28524 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28525 frame=@{func="callee4",args=[],
28526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28527 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28533 111^done,frame=@{level="0",func="callee3",
28534 args=[@{name="strarg",
28535 value="0x11940 \"A string argument.\""@}],
28536 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28537 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28542 @subheading The @code{-exec-run} Command
28545 @subsubheading Synopsis
28548 -exec-run [ --all | --thread-group N ] [ --start ]
28551 Starts execution of the inferior from the beginning. The inferior
28552 executes until either a breakpoint is encountered or the program
28553 exits. In the latter case the output will include an exit code, if
28554 the program has exited exceptionally.
28556 When neither the @samp{--all} nor the @samp{--thread-group} option
28557 is specified, the current inferior is started. If the
28558 @samp{--thread-group} option is specified, it should refer to a thread
28559 group of type @samp{process}, and that thread group will be started.
28560 If the @samp{--all} option is specified, then all inferiors will be started.
28562 Using the @samp{--start} option instructs the debugger to stop
28563 the execution at the start of the inferior's main subprogram,
28564 following the same behavior as the @code{start} command
28565 (@pxref{Starting}).
28567 @subsubheading @value{GDBN} Command
28569 The corresponding @value{GDBN} command is @samp{run}.
28571 @subsubheading Examples
28576 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28581 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28582 frame=@{func="main",args=[],file="recursive2.c",
28583 fullname="/home/foo/bar/recursive2.c",line="4"@}
28588 Program exited normally:
28596 *stopped,reason="exited-normally"
28601 Program exited exceptionally:
28609 *stopped,reason="exited",exit-code="01"
28613 Another way the program can terminate is if it receives a signal such as
28614 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28618 *stopped,reason="exited-signalled",signal-name="SIGINT",
28619 signal-meaning="Interrupt"
28623 @c @subheading -exec-signal
28626 @subheading The @code{-exec-step} Command
28629 @subsubheading Synopsis
28632 -exec-step [--reverse]
28635 Resumes execution of the inferior program, stopping when the beginning
28636 of the next source line is reached, if the next source line is not a
28637 function call. If it is, stop at the first instruction of the called
28638 function. If the @samp{--reverse} option is specified, resumes reverse
28639 execution of the inferior program, stopping at the beginning of the
28640 previously executed source line.
28642 @subsubheading @value{GDBN} Command
28644 The corresponding @value{GDBN} command is @samp{step}.
28646 @subsubheading Example
28648 Stepping into a function:
28654 *stopped,reason="end-stepping-range",
28655 frame=@{func="foo",args=[@{name="a",value="10"@},
28656 @{name="b",value="0"@}],file="recursive2.c",
28657 fullname="/home/foo/bar/recursive2.c",line="11"@}
28667 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28672 @subheading The @code{-exec-step-instruction} Command
28673 @findex -exec-step-instruction
28675 @subsubheading Synopsis
28678 -exec-step-instruction [--reverse]
28681 Resumes the inferior which executes one machine instruction. If the
28682 @samp{--reverse} option is specified, resumes reverse execution of the
28683 inferior program, stopping at the previously executed instruction.
28684 The output, once @value{GDBN} has stopped, will vary depending on
28685 whether we have stopped in the middle of a source line or not. In the
28686 former case, the address at which the program stopped will be printed
28689 @subsubheading @value{GDBN} Command
28691 The corresponding @value{GDBN} command is @samp{stepi}.
28693 @subsubheading Example
28697 -exec-step-instruction
28701 *stopped,reason="end-stepping-range",
28702 frame=@{func="foo",args=[],file="try.c",
28703 fullname="/home/foo/bar/try.c",line="10"@}
28705 -exec-step-instruction
28709 *stopped,reason="end-stepping-range",
28710 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28711 fullname="/home/foo/bar/try.c",line="10"@}
28716 @subheading The @code{-exec-until} Command
28717 @findex -exec-until
28719 @subsubheading Synopsis
28722 -exec-until [ @var{location} ]
28725 Executes the inferior until the @var{location} specified in the
28726 argument is reached. If there is no argument, the inferior executes
28727 until a source line greater than the current one is reached. The
28728 reason for stopping in this case will be @samp{location-reached}.
28730 @subsubheading @value{GDBN} Command
28732 The corresponding @value{GDBN} command is @samp{until}.
28734 @subsubheading Example
28738 -exec-until recursive2.c:6
28742 *stopped,reason="location-reached",frame=@{func="main",args=[],
28743 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28748 @subheading -file-clear
28749 Is this going away????
28752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28753 @node GDB/MI Stack Manipulation
28754 @section @sc{gdb/mi} Stack Manipulation Commands
28756 @subheading The @code{-enable-frame-filters} Command
28757 @findex -enable-frame-filters
28760 -enable-frame-filters
28763 @value{GDBN} allows Python-based frame filters to affect the output of
28764 the MI commands relating to stack traces. As there is no way to
28765 implement this in a fully backward-compatible way, a front end must
28766 request that this functionality be enabled.
28768 Once enabled, this feature cannot be disabled.
28770 Note that if Python support has not been compiled into @value{GDBN},
28771 this command will still succeed (and do nothing).
28773 @subheading The @code{-stack-info-frame} Command
28774 @findex -stack-info-frame
28776 @subsubheading Synopsis
28782 Get info on the selected frame.
28784 @subsubheading @value{GDBN} Command
28786 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28787 (without arguments).
28789 @subsubheading Example
28794 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28795 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28796 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28800 @subheading The @code{-stack-info-depth} Command
28801 @findex -stack-info-depth
28803 @subsubheading Synopsis
28806 -stack-info-depth [ @var{max-depth} ]
28809 Return the depth of the stack. If the integer argument @var{max-depth}
28810 is specified, do not count beyond @var{max-depth} frames.
28812 @subsubheading @value{GDBN} Command
28814 There's no equivalent @value{GDBN} command.
28816 @subsubheading Example
28818 For a stack with frame levels 0 through 11:
28825 -stack-info-depth 4
28828 -stack-info-depth 12
28831 -stack-info-depth 11
28834 -stack-info-depth 13
28839 @anchor{-stack-list-arguments}
28840 @subheading The @code{-stack-list-arguments} Command
28841 @findex -stack-list-arguments
28843 @subsubheading Synopsis
28846 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28847 [ @var{low-frame} @var{high-frame} ]
28850 Display a list of the arguments for the frames between @var{low-frame}
28851 and @var{high-frame} (inclusive). If @var{low-frame} and
28852 @var{high-frame} are not provided, list the arguments for the whole
28853 call stack. If the two arguments are equal, show the single frame
28854 at the corresponding level. It is an error if @var{low-frame} is
28855 larger than the actual number of frames. On the other hand,
28856 @var{high-frame} may be larger than the actual number of frames, in
28857 which case only existing frames will be returned.
28859 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28860 the variables; if it is 1 or @code{--all-values}, print also their
28861 values; and if it is 2 or @code{--simple-values}, print the name,
28862 type and value for simple data types, and the name and type for arrays,
28863 structures and unions. If the option @code{--no-frame-filters} is
28864 supplied, then Python frame filters will not be executed.
28866 If the @code{--skip-unavailable} option is specified, arguments that
28867 are not available are not listed. Partially available arguments
28868 are still displayed, however.
28870 Use of this command to obtain arguments in a single frame is
28871 deprecated in favor of the @samp{-stack-list-variables} command.
28873 @subsubheading @value{GDBN} Command
28875 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28876 @samp{gdb_get_args} command which partially overlaps with the
28877 functionality of @samp{-stack-list-arguments}.
28879 @subsubheading Example
28886 frame=@{level="0",addr="0x00010734",func="callee4",
28887 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28888 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28889 frame=@{level="1",addr="0x0001076c",func="callee3",
28890 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28891 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28892 frame=@{level="2",addr="0x0001078c",func="callee2",
28893 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28894 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28895 frame=@{level="3",addr="0x000107b4",func="callee1",
28896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28897 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28898 frame=@{level="4",addr="0x000107e0",func="main",
28899 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28900 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28902 -stack-list-arguments 0
28905 frame=@{level="0",args=[]@},
28906 frame=@{level="1",args=[name="strarg"]@},
28907 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28908 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28909 frame=@{level="4",args=[]@}]
28911 -stack-list-arguments 1
28914 frame=@{level="0",args=[]@},
28916 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28917 frame=@{level="2",args=[
28918 @{name="intarg",value="2"@},
28919 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28920 @{frame=@{level="3",args=[
28921 @{name="intarg",value="2"@},
28922 @{name="strarg",value="0x11940 \"A string argument.\""@},
28923 @{name="fltarg",value="3.5"@}]@},
28924 frame=@{level="4",args=[]@}]
28926 -stack-list-arguments 0 2 2
28927 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28929 -stack-list-arguments 1 2 2
28930 ^done,stack-args=[frame=@{level="2",
28931 args=[@{name="intarg",value="2"@},
28932 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28936 @c @subheading -stack-list-exception-handlers
28939 @anchor{-stack-list-frames}
28940 @subheading The @code{-stack-list-frames} Command
28941 @findex -stack-list-frames
28943 @subsubheading Synopsis
28946 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28949 List the frames currently on the stack. For each frame it displays the
28954 The frame number, 0 being the topmost frame, i.e., the innermost function.
28956 The @code{$pc} value for that frame.
28960 File name of the source file where the function lives.
28961 @item @var{fullname}
28962 The full file name of the source file where the function lives.
28964 Line number corresponding to the @code{$pc}.
28966 The shared library where this function is defined. This is only given
28967 if the frame's function is not known.
28970 If invoked without arguments, this command prints a backtrace for the
28971 whole stack. If given two integer arguments, it shows the frames whose
28972 levels are between the two arguments (inclusive). If the two arguments
28973 are equal, it shows the single frame at the corresponding level. It is
28974 an error if @var{low-frame} is larger than the actual number of
28975 frames. On the other hand, @var{high-frame} may be larger than the
28976 actual number of frames, in which case only existing frames will be
28977 returned. If the option @code{--no-frame-filters} is supplied, then
28978 Python frame filters will not be executed.
28980 @subsubheading @value{GDBN} Command
28982 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28984 @subsubheading Example
28986 Full stack backtrace:
28992 [frame=@{level="0",addr="0x0001076c",func="foo",
28993 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28994 frame=@{level="1",addr="0x000107a4",func="foo",
28995 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28996 frame=@{level="2",addr="0x000107a4",func="foo",
28997 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28998 frame=@{level="3",addr="0x000107a4",func="foo",
28999 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29000 frame=@{level="4",addr="0x000107a4",func="foo",
29001 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29002 frame=@{level="5",addr="0x000107a4",func="foo",
29003 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29004 frame=@{level="6",addr="0x000107a4",func="foo",
29005 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29006 frame=@{level="7",addr="0x000107a4",func="foo",
29007 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29008 frame=@{level="8",addr="0x000107a4",func="foo",
29009 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29010 frame=@{level="9",addr="0x000107a4",func="foo",
29011 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29012 frame=@{level="10",addr="0x000107a4",func="foo",
29013 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29014 frame=@{level="11",addr="0x00010738",func="main",
29015 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29019 Show frames between @var{low_frame} and @var{high_frame}:
29023 -stack-list-frames 3 5
29025 [frame=@{level="3",addr="0x000107a4",func="foo",
29026 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29027 frame=@{level="4",addr="0x000107a4",func="foo",
29028 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29029 frame=@{level="5",addr="0x000107a4",func="foo",
29030 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29034 Show a single frame:
29038 -stack-list-frames 3 3
29040 [frame=@{level="3",addr="0x000107a4",func="foo",
29041 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29046 @subheading The @code{-stack-list-locals} Command
29047 @findex -stack-list-locals
29048 @anchor{-stack-list-locals}
29050 @subsubheading Synopsis
29053 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29056 Display the local variable names for the selected frame. If
29057 @var{print-values} is 0 or @code{--no-values}, print only the names of
29058 the variables; if it is 1 or @code{--all-values}, print also their
29059 values; and if it is 2 or @code{--simple-values}, print the name,
29060 type and value for simple data types, and the name and type for arrays,
29061 structures and unions. In this last case, a frontend can immediately
29062 display the value of simple data types and create variable objects for
29063 other data types when the user wishes to explore their values in
29064 more detail. If the option @code{--no-frame-filters} is supplied, then
29065 Python frame filters will not be executed.
29067 If the @code{--skip-unavailable} option is specified, local variables
29068 that are not available are not listed. Partially available local
29069 variables are still displayed, however.
29071 This command is deprecated in favor of the
29072 @samp{-stack-list-variables} command.
29074 @subsubheading @value{GDBN} Command
29076 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29078 @subsubheading Example
29082 -stack-list-locals 0
29083 ^done,locals=[name="A",name="B",name="C"]
29085 -stack-list-locals --all-values
29086 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29087 @{name="C",value="@{1, 2, 3@}"@}]
29088 -stack-list-locals --simple-values
29089 ^done,locals=[@{name="A",type="int",value="1"@},
29090 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29094 @anchor{-stack-list-variables}
29095 @subheading The @code{-stack-list-variables} Command
29096 @findex -stack-list-variables
29098 @subsubheading Synopsis
29101 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29104 Display the names of local variables and function arguments for the selected frame. If
29105 @var{print-values} is 0 or @code{--no-values}, print only the names of
29106 the variables; if it is 1 or @code{--all-values}, print also their
29107 values; and if it is 2 or @code{--simple-values}, print the name,
29108 type and value for simple data types, and the name and type for arrays,
29109 structures and unions. If the option @code{--no-frame-filters} is
29110 supplied, then Python frame filters will not be executed.
29112 If the @code{--skip-unavailable} option is specified, local variables
29113 and arguments that are not available are not listed. Partially
29114 available arguments and local variables are still displayed, however.
29116 @subsubheading Example
29120 -stack-list-variables --thread 1 --frame 0 --all-values
29121 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29126 @subheading The @code{-stack-select-frame} Command
29127 @findex -stack-select-frame
29129 @subsubheading Synopsis
29132 -stack-select-frame @var{framenum}
29135 Change the selected frame. Select a different frame @var{framenum} on
29138 This command in deprecated in favor of passing the @samp{--frame}
29139 option to every command.
29141 @subsubheading @value{GDBN} Command
29143 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29144 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29146 @subsubheading Example
29150 -stack-select-frame 2
29155 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29156 @node GDB/MI Variable Objects
29157 @section @sc{gdb/mi} Variable Objects
29161 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29163 For the implementation of a variable debugger window (locals, watched
29164 expressions, etc.), we are proposing the adaptation of the existing code
29165 used by @code{Insight}.
29167 The two main reasons for that are:
29171 It has been proven in practice (it is already on its second generation).
29174 It will shorten development time (needless to say how important it is
29178 The original interface was designed to be used by Tcl code, so it was
29179 slightly changed so it could be used through @sc{gdb/mi}. This section
29180 describes the @sc{gdb/mi} operations that will be available and gives some
29181 hints about their use.
29183 @emph{Note}: In addition to the set of operations described here, we
29184 expect the @sc{gui} implementation of a variable window to require, at
29185 least, the following operations:
29188 @item @code{-gdb-show} @code{output-radix}
29189 @item @code{-stack-list-arguments}
29190 @item @code{-stack-list-locals}
29191 @item @code{-stack-select-frame}
29196 @subheading Introduction to Variable Objects
29198 @cindex variable objects in @sc{gdb/mi}
29200 Variable objects are "object-oriented" MI interface for examining and
29201 changing values of expressions. Unlike some other MI interfaces that
29202 work with expressions, variable objects are specifically designed for
29203 simple and efficient presentation in the frontend. A variable object
29204 is identified by string name. When a variable object is created, the
29205 frontend specifies the expression for that variable object. The
29206 expression can be a simple variable, or it can be an arbitrary complex
29207 expression, and can even involve CPU registers. After creating a
29208 variable object, the frontend can invoke other variable object
29209 operations---for example to obtain or change the value of a variable
29210 object, or to change display format.
29212 Variable objects have hierarchical tree structure. Any variable object
29213 that corresponds to a composite type, such as structure in C, has
29214 a number of child variable objects, for example corresponding to each
29215 element of a structure. A child variable object can itself have
29216 children, recursively. Recursion ends when we reach
29217 leaf variable objects, which always have built-in types. Child variable
29218 objects are created only by explicit request, so if a frontend
29219 is not interested in the children of a particular variable object, no
29220 child will be created.
29222 For a leaf variable object it is possible to obtain its value as a
29223 string, or set the value from a string. String value can be also
29224 obtained for a non-leaf variable object, but it's generally a string
29225 that only indicates the type of the object, and does not list its
29226 contents. Assignment to a non-leaf variable object is not allowed.
29228 A frontend does not need to read the values of all variable objects each time
29229 the program stops. Instead, MI provides an update command that lists all
29230 variable objects whose values has changed since the last update
29231 operation. This considerably reduces the amount of data that must
29232 be transferred to the frontend. As noted above, children variable
29233 objects are created on demand, and only leaf variable objects have a
29234 real value. As result, gdb will read target memory only for leaf
29235 variables that frontend has created.
29237 The automatic update is not always desirable. For example, a frontend
29238 might want to keep a value of some expression for future reference,
29239 and never update it. For another example, fetching memory is
29240 relatively slow for embedded targets, so a frontend might want
29241 to disable automatic update for the variables that are either not
29242 visible on the screen, or ``closed''. This is possible using so
29243 called ``frozen variable objects''. Such variable objects are never
29244 implicitly updated.
29246 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29247 fixed variable object, the expression is parsed when the variable
29248 object is created, including associating identifiers to specific
29249 variables. The meaning of expression never changes. For a floating
29250 variable object the values of variables whose names appear in the
29251 expressions are re-evaluated every time in the context of the current
29252 frame. Consider this example:
29257 struct work_state state;
29264 If a fixed variable object for the @code{state} variable is created in
29265 this function, and we enter the recursive call, the variable
29266 object will report the value of @code{state} in the top-level
29267 @code{do_work} invocation. On the other hand, a floating variable
29268 object will report the value of @code{state} in the current frame.
29270 If an expression specified when creating a fixed variable object
29271 refers to a local variable, the variable object becomes bound to the
29272 thread and frame in which the variable object is created. When such
29273 variable object is updated, @value{GDBN} makes sure that the
29274 thread/frame combination the variable object is bound to still exists,
29275 and re-evaluates the variable object in context of that thread/frame.
29277 The following is the complete set of @sc{gdb/mi} operations defined to
29278 access this functionality:
29280 @multitable @columnfractions .4 .6
29281 @item @strong{Operation}
29282 @tab @strong{Description}
29284 @item @code{-enable-pretty-printing}
29285 @tab enable Python-based pretty-printing
29286 @item @code{-var-create}
29287 @tab create a variable object
29288 @item @code{-var-delete}
29289 @tab delete the variable object and/or its children
29290 @item @code{-var-set-format}
29291 @tab set the display format of this variable
29292 @item @code{-var-show-format}
29293 @tab show the display format of this variable
29294 @item @code{-var-info-num-children}
29295 @tab tells how many children this object has
29296 @item @code{-var-list-children}
29297 @tab return a list of the object's children
29298 @item @code{-var-info-type}
29299 @tab show the type of this variable object
29300 @item @code{-var-info-expression}
29301 @tab print parent-relative expression that this variable object represents
29302 @item @code{-var-info-path-expression}
29303 @tab print full expression that this variable object represents
29304 @item @code{-var-show-attributes}
29305 @tab is this variable editable? does it exist here?
29306 @item @code{-var-evaluate-expression}
29307 @tab get the value of this variable
29308 @item @code{-var-assign}
29309 @tab set the value of this variable
29310 @item @code{-var-update}
29311 @tab update the variable and its children
29312 @item @code{-var-set-frozen}
29313 @tab set frozeness attribute
29314 @item @code{-var-set-update-range}
29315 @tab set range of children to display on update
29318 In the next subsection we describe each operation in detail and suggest
29319 how it can be used.
29321 @subheading Description And Use of Operations on Variable Objects
29323 @subheading The @code{-enable-pretty-printing} Command
29324 @findex -enable-pretty-printing
29327 -enable-pretty-printing
29330 @value{GDBN} allows Python-based visualizers to affect the output of the
29331 MI variable object commands. However, because there was no way to
29332 implement this in a fully backward-compatible way, a front end must
29333 request that this functionality be enabled.
29335 Once enabled, this feature cannot be disabled.
29337 Note that if Python support has not been compiled into @value{GDBN},
29338 this command will still succeed (and do nothing).
29340 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29341 may work differently in future versions of @value{GDBN}.
29343 @subheading The @code{-var-create} Command
29344 @findex -var-create
29346 @subsubheading Synopsis
29349 -var-create @{@var{name} | "-"@}
29350 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29353 This operation creates a variable object, which allows the monitoring of
29354 a variable, the result of an expression, a memory cell or a CPU
29357 The @var{name} parameter is the string by which the object can be
29358 referenced. It must be unique. If @samp{-} is specified, the varobj
29359 system will generate a string ``varNNNNNN'' automatically. It will be
29360 unique provided that one does not specify @var{name} of that format.
29361 The command fails if a duplicate name is found.
29363 The frame under which the expression should be evaluated can be
29364 specified by @var{frame-addr}. A @samp{*} indicates that the current
29365 frame should be used. A @samp{@@} indicates that a floating variable
29366 object must be created.
29368 @var{expression} is any expression valid on the current language set (must not
29369 begin with a @samp{*}), or one of the following:
29373 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29376 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29379 @samp{$@var{regname}} --- a CPU register name
29382 @cindex dynamic varobj
29383 A varobj's contents may be provided by a Python-based pretty-printer. In this
29384 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29385 have slightly different semantics in some cases. If the
29386 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29387 will never create a dynamic varobj. This ensures backward
29388 compatibility for existing clients.
29390 @subsubheading Result
29392 This operation returns attributes of the newly-created varobj. These
29397 The name of the varobj.
29400 The number of children of the varobj. This number is not necessarily
29401 reliable for a dynamic varobj. Instead, you must examine the
29402 @samp{has_more} attribute.
29405 The varobj's scalar value. For a varobj whose type is some sort of
29406 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29407 will not be interesting.
29410 The varobj's type. This is a string representation of the type, as
29411 would be printed by the @value{GDBN} CLI. If @samp{print object}
29412 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29413 @emph{actual} (derived) type of the object is shown rather than the
29414 @emph{declared} one.
29417 If a variable object is bound to a specific thread, then this is the
29418 thread's global identifier.
29421 For a dynamic varobj, this indicates whether there appear to be any
29422 children available. For a non-dynamic varobj, this will be 0.
29425 This attribute will be present and have the value @samp{1} if the
29426 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29427 then this attribute will not be present.
29430 A dynamic varobj can supply a display hint to the front end. The
29431 value comes directly from the Python pretty-printer object's
29432 @code{display_hint} method. @xref{Pretty Printing API}.
29435 Typical output will look like this:
29438 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29439 has_more="@var{has_more}"
29443 @subheading The @code{-var-delete} Command
29444 @findex -var-delete
29446 @subsubheading Synopsis
29449 -var-delete [ -c ] @var{name}
29452 Deletes a previously created variable object and all of its children.
29453 With the @samp{-c} option, just deletes the children.
29455 Returns an error if the object @var{name} is not found.
29458 @subheading The @code{-var-set-format} Command
29459 @findex -var-set-format
29461 @subsubheading Synopsis
29464 -var-set-format @var{name} @var{format-spec}
29467 Sets the output format for the value of the object @var{name} to be
29470 @anchor{-var-set-format}
29471 The syntax for the @var{format-spec} is as follows:
29474 @var{format-spec} @expansion{}
29475 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29478 The natural format is the default format choosen automatically
29479 based on the variable type (like decimal for an @code{int}, hex
29480 for pointers, etc.).
29482 The zero-hexadecimal format has a representation similar to hexadecimal
29483 but with padding zeroes to the left of the value. For example, a 32-bit
29484 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29485 zero-hexadecimal format.
29487 For a variable with children, the format is set only on the
29488 variable itself, and the children are not affected.
29490 @subheading The @code{-var-show-format} Command
29491 @findex -var-show-format
29493 @subsubheading Synopsis
29496 -var-show-format @var{name}
29499 Returns the format used to display the value of the object @var{name}.
29502 @var{format} @expansion{}
29507 @subheading The @code{-var-info-num-children} Command
29508 @findex -var-info-num-children
29510 @subsubheading Synopsis
29513 -var-info-num-children @var{name}
29516 Returns the number of children of a variable object @var{name}:
29522 Note that this number is not completely reliable for a dynamic varobj.
29523 It will return the current number of children, but more children may
29527 @subheading The @code{-var-list-children} Command
29528 @findex -var-list-children
29530 @subsubheading Synopsis
29533 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29535 @anchor{-var-list-children}
29537 Return a list of the children of the specified variable object and
29538 create variable objects for them, if they do not already exist. With
29539 a single argument or if @var{print-values} has a value of 0 or
29540 @code{--no-values}, print only the names of the variables; if
29541 @var{print-values} is 1 or @code{--all-values}, also print their
29542 values; and if it is 2 or @code{--simple-values} print the name and
29543 value for simple data types and just the name for arrays, structures
29546 @var{from} and @var{to}, if specified, indicate the range of children
29547 to report. If @var{from} or @var{to} is less than zero, the range is
29548 reset and all children will be reported. Otherwise, children starting
29549 at @var{from} (zero-based) and up to and excluding @var{to} will be
29552 If a child range is requested, it will only affect the current call to
29553 @code{-var-list-children}, but not future calls to @code{-var-update}.
29554 For this, you must instead use @code{-var-set-update-range}. The
29555 intent of this approach is to enable a front end to implement any
29556 update approach it likes; for example, scrolling a view may cause the
29557 front end to request more children with @code{-var-list-children}, and
29558 then the front end could call @code{-var-set-update-range} with a
29559 different range to ensure that future updates are restricted to just
29562 For each child the following results are returned:
29567 Name of the variable object created for this child.
29570 The expression to be shown to the user by the front end to designate this child.
29571 For example this may be the name of a structure member.
29573 For a dynamic varobj, this value cannot be used to form an
29574 expression. There is no way to do this at all with a dynamic varobj.
29576 For C/C@t{++} structures there are several pseudo children returned to
29577 designate access qualifiers. For these pseudo children @var{exp} is
29578 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29579 type and value are not present.
29581 A dynamic varobj will not report the access qualifying
29582 pseudo-children, regardless of the language. This information is not
29583 available at all with a dynamic varobj.
29586 Number of children this child has. For a dynamic varobj, this will be
29590 The type of the child. If @samp{print object}
29591 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29592 @emph{actual} (derived) type of the object is shown rather than the
29593 @emph{declared} one.
29596 If values were requested, this is the value.
29599 If this variable object is associated with a thread, this is the
29600 thread's global thread id. Otherwise this result is not present.
29603 If the variable object is frozen, this variable will be present with a value of 1.
29606 A dynamic varobj can supply a display hint to the front end. The
29607 value comes directly from the Python pretty-printer object's
29608 @code{display_hint} method. @xref{Pretty Printing API}.
29611 This attribute will be present and have the value @samp{1} if the
29612 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29613 then this attribute will not be present.
29617 The result may have its own attributes:
29621 A dynamic varobj can supply a display hint to the front end. The
29622 value comes directly from the Python pretty-printer object's
29623 @code{display_hint} method. @xref{Pretty Printing API}.
29626 This is an integer attribute which is nonzero if there are children
29627 remaining after the end of the selected range.
29630 @subsubheading Example
29634 -var-list-children n
29635 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29636 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29638 -var-list-children --all-values n
29639 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29640 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29644 @subheading The @code{-var-info-type} Command
29645 @findex -var-info-type
29647 @subsubheading Synopsis
29650 -var-info-type @var{name}
29653 Returns the type of the specified variable @var{name}. The type is
29654 returned as a string in the same format as it is output by the
29658 type=@var{typename}
29662 @subheading The @code{-var-info-expression} Command
29663 @findex -var-info-expression
29665 @subsubheading Synopsis
29668 -var-info-expression @var{name}
29671 Returns a string that is suitable for presenting this
29672 variable object in user interface. The string is generally
29673 not valid expression in the current language, and cannot be evaluated.
29675 For example, if @code{a} is an array, and variable object
29676 @code{A} was created for @code{a}, then we'll get this output:
29679 (gdb) -var-info-expression A.1
29680 ^done,lang="C",exp="1"
29684 Here, the value of @code{lang} is the language name, which can be
29685 found in @ref{Supported Languages}.
29687 Note that the output of the @code{-var-list-children} command also
29688 includes those expressions, so the @code{-var-info-expression} command
29691 @subheading The @code{-var-info-path-expression} Command
29692 @findex -var-info-path-expression
29694 @subsubheading Synopsis
29697 -var-info-path-expression @var{name}
29700 Returns an expression that can be evaluated in the current
29701 context and will yield the same value that a variable object has.
29702 Compare this with the @code{-var-info-expression} command, which
29703 result can be used only for UI presentation. Typical use of
29704 the @code{-var-info-path-expression} command is creating a
29705 watchpoint from a variable object.
29707 This command is currently not valid for children of a dynamic varobj,
29708 and will give an error when invoked on one.
29710 For example, suppose @code{C} is a C@t{++} class, derived from class
29711 @code{Base}, and that the @code{Base} class has a member called
29712 @code{m_size}. Assume a variable @code{c} is has the type of
29713 @code{C} and a variable object @code{C} was created for variable
29714 @code{c}. Then, we'll get this output:
29716 (gdb) -var-info-path-expression C.Base.public.m_size
29717 ^done,path_expr=((Base)c).m_size)
29720 @subheading The @code{-var-show-attributes} Command
29721 @findex -var-show-attributes
29723 @subsubheading Synopsis
29726 -var-show-attributes @var{name}
29729 List attributes of the specified variable object @var{name}:
29732 status=@var{attr} [ ( ,@var{attr} )* ]
29736 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29738 @subheading The @code{-var-evaluate-expression} Command
29739 @findex -var-evaluate-expression
29741 @subsubheading Synopsis
29744 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29747 Evaluates the expression that is represented by the specified variable
29748 object and returns its value as a string. The format of the string
29749 can be specified with the @samp{-f} option. The possible values of
29750 this option are the same as for @code{-var-set-format}
29751 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29752 the current display format will be used. The current display format
29753 can be changed using the @code{-var-set-format} command.
29759 Note that one must invoke @code{-var-list-children} for a variable
29760 before the value of a child variable can be evaluated.
29762 @subheading The @code{-var-assign} Command
29763 @findex -var-assign
29765 @subsubheading Synopsis
29768 -var-assign @var{name} @var{expression}
29771 Assigns the value of @var{expression} to the variable object specified
29772 by @var{name}. The object must be @samp{editable}. If the variable's
29773 value is altered by the assign, the variable will show up in any
29774 subsequent @code{-var-update} list.
29776 @subsubheading Example
29784 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29788 @subheading The @code{-var-update} Command
29789 @findex -var-update
29791 @subsubheading Synopsis
29794 -var-update [@var{print-values}] @{@var{name} | "*"@}
29797 Reevaluate the expressions corresponding to the variable object
29798 @var{name} and all its direct and indirect children, and return the
29799 list of variable objects whose values have changed; @var{name} must
29800 be a root variable object. Here, ``changed'' means that the result of
29801 @code{-var-evaluate-expression} before and after the
29802 @code{-var-update} is different. If @samp{*} is used as the variable
29803 object names, all existing variable objects are updated, except
29804 for frozen ones (@pxref{-var-set-frozen}). The option
29805 @var{print-values} determines whether both names and values, or just
29806 names are printed. The possible values of this option are the same
29807 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29808 recommended to use the @samp{--all-values} option, to reduce the
29809 number of MI commands needed on each program stop.
29811 With the @samp{*} parameter, if a variable object is bound to a
29812 currently running thread, it will not be updated, without any
29815 If @code{-var-set-update-range} was previously used on a varobj, then
29816 only the selected range of children will be reported.
29818 @code{-var-update} reports all the changed varobjs in a tuple named
29821 Each item in the change list is itself a tuple holding:
29825 The name of the varobj.
29828 If values were requested for this update, then this field will be
29829 present and will hold the value of the varobj.
29832 @anchor{-var-update}
29833 This field is a string which may take one of three values:
29837 The variable object's current value is valid.
29840 The variable object does not currently hold a valid value but it may
29841 hold one in the future if its associated expression comes back into
29845 The variable object no longer holds a valid value.
29846 This can occur when the executable file being debugged has changed,
29847 either through recompilation or by using the @value{GDBN} @code{file}
29848 command. The front end should normally choose to delete these variable
29852 In the future new values may be added to this list so the front should
29853 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29856 This is only present if the varobj is still valid. If the type
29857 changed, then this will be the string @samp{true}; otherwise it will
29860 When a varobj's type changes, its children are also likely to have
29861 become incorrect. Therefore, the varobj's children are automatically
29862 deleted when this attribute is @samp{true}. Also, the varobj's update
29863 range, when set using the @code{-var-set-update-range} command, is
29867 If the varobj's type changed, then this field will be present and will
29870 @item new_num_children
29871 For a dynamic varobj, if the number of children changed, or if the
29872 type changed, this will be the new number of children.
29874 The @samp{numchild} field in other varobj responses is generally not
29875 valid for a dynamic varobj -- it will show the number of children that
29876 @value{GDBN} knows about, but because dynamic varobjs lazily
29877 instantiate their children, this will not reflect the number of
29878 children which may be available.
29880 The @samp{new_num_children} attribute only reports changes to the
29881 number of children known by @value{GDBN}. This is the only way to
29882 detect whether an update has removed children (which necessarily can
29883 only happen at the end of the update range).
29886 The display hint, if any.
29889 This is an integer value, which will be 1 if there are more children
29890 available outside the varobj's update range.
29893 This attribute will be present and have the value @samp{1} if the
29894 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29895 then this attribute will not be present.
29898 If new children were added to a dynamic varobj within the selected
29899 update range (as set by @code{-var-set-update-range}), then they will
29900 be listed in this attribute.
29903 @subsubheading Example
29910 -var-update --all-values var1
29911 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29912 type_changed="false"@}]
29916 @subheading The @code{-var-set-frozen} Command
29917 @findex -var-set-frozen
29918 @anchor{-var-set-frozen}
29920 @subsubheading Synopsis
29923 -var-set-frozen @var{name} @var{flag}
29926 Set the frozenness flag on the variable object @var{name}. The
29927 @var{flag} parameter should be either @samp{1} to make the variable
29928 frozen or @samp{0} to make it unfrozen. If a variable object is
29929 frozen, then neither itself, nor any of its children, are
29930 implicitly updated by @code{-var-update} of
29931 a parent variable or by @code{-var-update *}. Only
29932 @code{-var-update} of the variable itself will update its value and
29933 values of its children. After a variable object is unfrozen, it is
29934 implicitly updated by all subsequent @code{-var-update} operations.
29935 Unfreezing a variable does not update it, only subsequent
29936 @code{-var-update} does.
29938 @subsubheading Example
29942 -var-set-frozen V 1
29947 @subheading The @code{-var-set-update-range} command
29948 @findex -var-set-update-range
29949 @anchor{-var-set-update-range}
29951 @subsubheading Synopsis
29954 -var-set-update-range @var{name} @var{from} @var{to}
29957 Set the range of children to be returned by future invocations of
29958 @code{-var-update}.
29960 @var{from} and @var{to} indicate the range of children to report. If
29961 @var{from} or @var{to} is less than zero, the range is reset and all
29962 children will be reported. Otherwise, children starting at @var{from}
29963 (zero-based) and up to and excluding @var{to} will be reported.
29965 @subsubheading Example
29969 -var-set-update-range V 1 2
29973 @subheading The @code{-var-set-visualizer} command
29974 @findex -var-set-visualizer
29975 @anchor{-var-set-visualizer}
29977 @subsubheading Synopsis
29980 -var-set-visualizer @var{name} @var{visualizer}
29983 Set a visualizer for the variable object @var{name}.
29985 @var{visualizer} is the visualizer to use. The special value
29986 @samp{None} means to disable any visualizer in use.
29988 If not @samp{None}, @var{visualizer} must be a Python expression.
29989 This expression must evaluate to a callable object which accepts a
29990 single argument. @value{GDBN} will call this object with the value of
29991 the varobj @var{name} as an argument (this is done so that the same
29992 Python pretty-printing code can be used for both the CLI and MI).
29993 When called, this object must return an object which conforms to the
29994 pretty-printing interface (@pxref{Pretty Printing API}).
29996 The pre-defined function @code{gdb.default_visualizer} may be used to
29997 select a visualizer by following the built-in process
29998 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29999 a varobj is created, and so ordinarily is not needed.
30001 This feature is only available if Python support is enabled. The MI
30002 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30003 can be used to check this.
30005 @subsubheading Example
30007 Resetting the visualizer:
30011 -var-set-visualizer V None
30015 Reselecting the default (type-based) visualizer:
30019 -var-set-visualizer V gdb.default_visualizer
30023 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30024 can be used to instantiate this class for a varobj:
30028 -var-set-visualizer V "lambda val: SomeClass()"
30032 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30033 @node GDB/MI Data Manipulation
30034 @section @sc{gdb/mi} Data Manipulation
30036 @cindex data manipulation, in @sc{gdb/mi}
30037 @cindex @sc{gdb/mi}, data manipulation
30038 This section describes the @sc{gdb/mi} commands that manipulate data:
30039 examine memory and registers, evaluate expressions, etc.
30041 For details about what an addressable memory unit is,
30042 @pxref{addressable memory unit}.
30044 @c REMOVED FROM THE INTERFACE.
30045 @c @subheading -data-assign
30046 @c Change the value of a program variable. Plenty of side effects.
30047 @c @subsubheading GDB Command
30049 @c @subsubheading Example
30052 @subheading The @code{-data-disassemble} Command
30053 @findex -data-disassemble
30055 @subsubheading Synopsis
30059 [ -s @var{start-addr} -e @var{end-addr} ]
30060 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30068 @item @var{start-addr}
30069 is the beginning address (or @code{$pc})
30070 @item @var{end-addr}
30072 @item @var{filename}
30073 is the name of the file to disassemble
30074 @item @var{linenum}
30075 is the line number to disassemble around
30077 is the number of disassembly lines to be produced. If it is -1,
30078 the whole function will be disassembled, in case no @var{end-addr} is
30079 specified. If @var{end-addr} is specified as a non-zero value, and
30080 @var{lines} is lower than the number of disassembly lines between
30081 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30082 displayed; if @var{lines} is higher than the number of lines between
30083 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30088 @item 0 disassembly only
30089 @item 1 mixed source and disassembly (deprecated)
30090 @item 2 disassembly with raw opcodes
30091 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30092 @item 4 mixed source and disassembly
30093 @item 5 mixed source and disassembly with raw opcodes
30096 Modes 1 and 3 are deprecated. The output is ``source centric''
30097 which hasn't proved useful in practice.
30098 @xref{Machine Code}, for a discussion of the difference between
30099 @code{/m} and @code{/s} output of the @code{disassemble} command.
30102 @subsubheading Result
30104 The result of the @code{-data-disassemble} command will be a list named
30105 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30106 used with the @code{-data-disassemble} command.
30108 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30113 The address at which this instruction was disassembled.
30116 The name of the function this instruction is within.
30119 The decimal offset in bytes from the start of @samp{func-name}.
30122 The text disassembly for this @samp{address}.
30125 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30126 bytes for the @samp{inst} field.
30130 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30131 @samp{src_and_asm_line}, each of which has the following fields:
30135 The line number within @samp{file}.
30138 The file name from the compilation unit. This might be an absolute
30139 file name or a relative file name depending on the compile command
30143 Absolute file name of @samp{file}. It is converted to a canonical form
30144 using the source file search path
30145 (@pxref{Source Path, ,Specifying Source Directories})
30146 and after resolving all the symbolic links.
30148 If the source file is not found this field will contain the path as
30149 present in the debug information.
30151 @item line_asm_insn
30152 This is a list of tuples containing the disassembly for @samp{line} in
30153 @samp{file}. The fields of each tuple are the same as for
30154 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30155 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30160 Note that whatever included in the @samp{inst} field, is not
30161 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30164 @subsubheading @value{GDBN} Command
30166 The corresponding @value{GDBN} command is @samp{disassemble}.
30168 @subsubheading Example
30170 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30174 -data-disassemble -s $pc -e "$pc + 20" -- 0
30177 @{address="0x000107c0",func-name="main",offset="4",
30178 inst="mov 2, %o0"@},
30179 @{address="0x000107c4",func-name="main",offset="8",
30180 inst="sethi %hi(0x11800), %o2"@},
30181 @{address="0x000107c8",func-name="main",offset="12",
30182 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30183 @{address="0x000107cc",func-name="main",offset="16",
30184 inst="sethi %hi(0x11800), %o2"@},
30185 @{address="0x000107d0",func-name="main",offset="20",
30186 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30190 Disassemble the whole @code{main} function. Line 32 is part of
30194 -data-disassemble -f basics.c -l 32 -- 0
30196 @{address="0x000107bc",func-name="main",offset="0",
30197 inst="save %sp, -112, %sp"@},
30198 @{address="0x000107c0",func-name="main",offset="4",
30199 inst="mov 2, %o0"@},
30200 @{address="0x000107c4",func-name="main",offset="8",
30201 inst="sethi %hi(0x11800), %o2"@},
30203 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30204 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30208 Disassemble 3 instructions from the start of @code{main}:
30212 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30214 @{address="0x000107bc",func-name="main",offset="0",
30215 inst="save %sp, -112, %sp"@},
30216 @{address="0x000107c0",func-name="main",offset="4",
30217 inst="mov 2, %o0"@},
30218 @{address="0x000107c4",func-name="main",offset="8",
30219 inst="sethi %hi(0x11800), %o2"@}]
30223 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30227 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30229 src_and_asm_line=@{line="31",
30230 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30231 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30232 line_asm_insn=[@{address="0x000107bc",
30233 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30234 src_and_asm_line=@{line="32",
30235 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30236 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30237 line_asm_insn=[@{address="0x000107c0",
30238 func-name="main",offset="4",inst="mov 2, %o0"@},
30239 @{address="0x000107c4",func-name="main",offset="8",
30240 inst="sethi %hi(0x11800), %o2"@}]@}]
30245 @subheading The @code{-data-evaluate-expression} Command
30246 @findex -data-evaluate-expression
30248 @subsubheading Synopsis
30251 -data-evaluate-expression @var{expr}
30254 Evaluate @var{expr} as an expression. The expression could contain an
30255 inferior function call. The function call will execute synchronously.
30256 If the expression contains spaces, it must be enclosed in double quotes.
30258 @subsubheading @value{GDBN} Command
30260 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30261 @samp{call}. In @code{gdbtk} only, there's a corresponding
30262 @samp{gdb_eval} command.
30264 @subsubheading Example
30266 In the following example, the numbers that precede the commands are the
30267 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30268 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30272 211-data-evaluate-expression A
30275 311-data-evaluate-expression &A
30276 311^done,value="0xefffeb7c"
30278 411-data-evaluate-expression A+3
30281 511-data-evaluate-expression "A + 3"
30287 @subheading The @code{-data-list-changed-registers} Command
30288 @findex -data-list-changed-registers
30290 @subsubheading Synopsis
30293 -data-list-changed-registers
30296 Display a list of the registers that have changed.
30298 @subsubheading @value{GDBN} Command
30300 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30301 has the corresponding command @samp{gdb_changed_register_list}.
30303 @subsubheading Example
30305 On a PPC MBX board:
30313 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30314 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30317 -data-list-changed-registers
30318 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30319 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30320 "24","25","26","27","28","30","31","64","65","66","67","69"]
30325 @subheading The @code{-data-list-register-names} Command
30326 @findex -data-list-register-names
30328 @subsubheading Synopsis
30331 -data-list-register-names [ ( @var{regno} )+ ]
30334 Show a list of register names for the current target. If no arguments
30335 are given, it shows a list of the names of all the registers. If
30336 integer numbers are given as arguments, it will print a list of the
30337 names of the registers corresponding to the arguments. To ensure
30338 consistency between a register name and its number, the output list may
30339 include empty register names.
30341 @subsubheading @value{GDBN} Command
30343 @value{GDBN} does not have a command which corresponds to
30344 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30345 corresponding command @samp{gdb_regnames}.
30347 @subsubheading Example
30349 For the PPC MBX board:
30352 -data-list-register-names
30353 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30354 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30355 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30356 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30357 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30358 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30359 "", "pc","ps","cr","lr","ctr","xer"]
30361 -data-list-register-names 1 2 3
30362 ^done,register-names=["r1","r2","r3"]
30366 @subheading The @code{-data-list-register-values} Command
30367 @findex -data-list-register-values
30369 @subsubheading Synopsis
30372 -data-list-register-values
30373 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30376 Display the registers' contents. The format according to which the
30377 registers' contents are to be returned is given by @var{fmt}, followed
30378 by an optional list of numbers specifying the registers to display. A
30379 missing list of numbers indicates that the contents of all the
30380 registers must be returned. The @code{--skip-unavailable} option
30381 indicates that only the available registers are to be returned.
30383 Allowed formats for @var{fmt} are:
30400 @subsubheading @value{GDBN} Command
30402 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30403 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30405 @subsubheading Example
30407 For a PPC MBX board (note: line breaks are for readability only, they
30408 don't appear in the actual output):
30412 -data-list-register-values r 64 65
30413 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30414 @{number="65",value="0x00029002"@}]
30416 -data-list-register-values x
30417 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30418 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30419 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30420 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30421 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30422 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30423 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30424 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30425 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30426 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30427 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30428 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30429 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30430 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30431 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30432 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30433 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30434 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30435 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30436 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30437 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30438 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30439 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30440 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30441 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30442 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30443 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30444 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30445 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30446 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30447 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30448 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30449 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30450 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30451 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30452 @{number="69",value="0x20002b03"@}]
30457 @subheading The @code{-data-read-memory} Command
30458 @findex -data-read-memory
30460 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30462 @subsubheading Synopsis
30465 -data-read-memory [ -o @var{byte-offset} ]
30466 @var{address} @var{word-format} @var{word-size}
30467 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30474 @item @var{address}
30475 An expression specifying the address of the first memory word to be
30476 read. Complex expressions containing embedded white space should be
30477 quoted using the C convention.
30479 @item @var{word-format}
30480 The format to be used to print the memory words. The notation is the
30481 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30484 @item @var{word-size}
30485 The size of each memory word in bytes.
30487 @item @var{nr-rows}
30488 The number of rows in the output table.
30490 @item @var{nr-cols}
30491 The number of columns in the output table.
30494 If present, indicates that each row should include an @sc{ascii} dump. The
30495 value of @var{aschar} is used as a padding character when a byte is not a
30496 member of the printable @sc{ascii} character set (printable @sc{ascii}
30497 characters are those whose code is between 32 and 126, inclusively).
30499 @item @var{byte-offset}
30500 An offset to add to the @var{address} before fetching memory.
30503 This command displays memory contents as a table of @var{nr-rows} by
30504 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30505 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30506 (returned as @samp{total-bytes}). Should less than the requested number
30507 of bytes be returned by the target, the missing words are identified
30508 using @samp{N/A}. The number of bytes read from the target is returned
30509 in @samp{nr-bytes} and the starting address used to read memory in
30512 The address of the next/previous row or page is available in
30513 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30516 @subsubheading @value{GDBN} Command
30518 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30519 @samp{gdb_get_mem} memory read command.
30521 @subsubheading Example
30523 Read six bytes of memory starting at @code{bytes+6} but then offset by
30524 @code{-6} bytes. Format as three rows of two columns. One byte per
30525 word. Display each word in hex.
30529 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30530 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30531 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30532 prev-page="0x0000138a",memory=[
30533 @{addr="0x00001390",data=["0x00","0x01"]@},
30534 @{addr="0x00001392",data=["0x02","0x03"]@},
30535 @{addr="0x00001394",data=["0x04","0x05"]@}]
30539 Read two bytes of memory starting at address @code{shorts + 64} and
30540 display as a single word formatted in decimal.
30544 5-data-read-memory shorts+64 d 2 1 1
30545 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30546 next-row="0x00001512",prev-row="0x0000150e",
30547 next-page="0x00001512",prev-page="0x0000150e",memory=[
30548 @{addr="0x00001510",data=["128"]@}]
30552 Read thirty two bytes of memory starting at @code{bytes+16} and format
30553 as eight rows of four columns. Include a string encoding with @samp{x}
30554 used as the non-printable character.
30558 4-data-read-memory bytes+16 x 1 8 4 x
30559 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30560 next-row="0x000013c0",prev-row="0x0000139c",
30561 next-page="0x000013c0",prev-page="0x00001380",memory=[
30562 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30563 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30564 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30565 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30566 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30567 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30568 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30569 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30573 @subheading The @code{-data-read-memory-bytes} Command
30574 @findex -data-read-memory-bytes
30576 @subsubheading Synopsis
30579 -data-read-memory-bytes [ -o @var{offset} ]
30580 @var{address} @var{count}
30587 @item @var{address}
30588 An expression specifying the address of the first addressable memory unit
30589 to be read. Complex expressions containing embedded white space should be
30590 quoted using the C convention.
30593 The number of addressable memory units to read. This should be an integer
30597 The offset relative to @var{address} at which to start reading. This
30598 should be an integer literal. This option is provided so that a frontend
30599 is not required to first evaluate address and then perform address
30600 arithmetics itself.
30604 This command attempts to read all accessible memory regions in the
30605 specified range. First, all regions marked as unreadable in the memory
30606 map (if one is defined) will be skipped. @xref{Memory Region
30607 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30608 regions. For each one, if reading full region results in an errors,
30609 @value{GDBN} will try to read a subset of the region.
30611 In general, every single memory unit in the region may be readable or not,
30612 and the only way to read every readable unit is to try a read at
30613 every address, which is not practical. Therefore, @value{GDBN} will
30614 attempt to read all accessible memory units at either beginning or the end
30615 of the region, using a binary division scheme. This heuristic works
30616 well for reading accross a memory map boundary. Note that if a region
30617 has a readable range that is neither at the beginning or the end,
30618 @value{GDBN} will not read it.
30620 The result record (@pxref{GDB/MI Result Records}) that is output of
30621 the command includes a field named @samp{memory} whose content is a
30622 list of tuples. Each tuple represent a successfully read memory block
30623 and has the following fields:
30627 The start address of the memory block, as hexadecimal literal.
30630 The end address of the memory block, as hexadecimal literal.
30633 The offset of the memory block, as hexadecimal literal, relative to
30634 the start address passed to @code{-data-read-memory-bytes}.
30637 The contents of the memory block, in hex.
30643 @subsubheading @value{GDBN} Command
30645 The corresponding @value{GDBN} command is @samp{x}.
30647 @subsubheading Example
30651 -data-read-memory-bytes &a 10
30652 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30654 contents="01000000020000000300"@}]
30659 @subheading The @code{-data-write-memory-bytes} Command
30660 @findex -data-write-memory-bytes
30662 @subsubheading Synopsis
30665 -data-write-memory-bytes @var{address} @var{contents}
30666 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30673 @item @var{address}
30674 An expression specifying the address of the first addressable memory unit
30675 to be written. Complex expressions containing embedded white space should
30676 be quoted using the C convention.
30678 @item @var{contents}
30679 The hex-encoded data to write. It is an error if @var{contents} does
30680 not represent an integral number of addressable memory units.
30683 Optional argument indicating the number of addressable memory units to be
30684 written. If @var{count} is greater than @var{contents}' length,
30685 @value{GDBN} will repeatedly write @var{contents} until it fills
30686 @var{count} memory units.
30690 @subsubheading @value{GDBN} Command
30692 There's no corresponding @value{GDBN} command.
30694 @subsubheading Example
30698 -data-write-memory-bytes &a "aabbccdd"
30705 -data-write-memory-bytes &a "aabbccdd" 16e
30710 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30711 @node GDB/MI Tracepoint Commands
30712 @section @sc{gdb/mi} Tracepoint Commands
30714 The commands defined in this section implement MI support for
30715 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30717 @subheading The @code{-trace-find} Command
30718 @findex -trace-find
30720 @subsubheading Synopsis
30723 -trace-find @var{mode} [@var{parameters}@dots{}]
30726 Find a trace frame using criteria defined by @var{mode} and
30727 @var{parameters}. The following table lists permissible
30728 modes and their parameters. For details of operation, see @ref{tfind}.
30733 No parameters are required. Stops examining trace frames.
30736 An integer is required as parameter. Selects tracepoint frame with
30739 @item tracepoint-number
30740 An integer is required as parameter. Finds next
30741 trace frame that corresponds to tracepoint with the specified number.
30744 An address is required as parameter. Finds
30745 next trace frame that corresponds to any tracepoint at the specified
30748 @item pc-inside-range
30749 Two addresses are required as parameters. Finds next trace
30750 frame that corresponds to a tracepoint at an address inside the
30751 specified range. Both bounds are considered to be inside the range.
30753 @item pc-outside-range
30754 Two addresses are required as parameters. Finds
30755 next trace frame that corresponds to a tracepoint at an address outside
30756 the specified range. Both bounds are considered to be inside the range.
30759 Line specification is required as parameter. @xref{Specify Location}.
30760 Finds next trace frame that corresponds to a tracepoint at
30761 the specified location.
30765 If @samp{none} was passed as @var{mode}, the response does not
30766 have fields. Otherwise, the response may have the following fields:
30770 This field has either @samp{0} or @samp{1} as the value, depending
30771 on whether a matching tracepoint was found.
30774 The index of the found traceframe. This field is present iff
30775 the @samp{found} field has value of @samp{1}.
30778 The index of the found tracepoint. This field is present iff
30779 the @samp{found} field has value of @samp{1}.
30782 The information about the frame corresponding to the found trace
30783 frame. This field is present only if a trace frame was found.
30784 @xref{GDB/MI Frame Information}, for description of this field.
30788 @subsubheading @value{GDBN} Command
30790 The corresponding @value{GDBN} command is @samp{tfind}.
30792 @subheading -trace-define-variable
30793 @findex -trace-define-variable
30795 @subsubheading Synopsis
30798 -trace-define-variable @var{name} [ @var{value} ]
30801 Create trace variable @var{name} if it does not exist. If
30802 @var{value} is specified, sets the initial value of the specified
30803 trace variable to that value. Note that the @var{name} should start
30804 with the @samp{$} character.
30806 @subsubheading @value{GDBN} Command
30808 The corresponding @value{GDBN} command is @samp{tvariable}.
30810 @subheading The @code{-trace-frame-collected} Command
30811 @findex -trace-frame-collected
30813 @subsubheading Synopsis
30816 -trace-frame-collected
30817 [--var-print-values @var{var_pval}]
30818 [--comp-print-values @var{comp_pval}]
30819 [--registers-format @var{regformat}]
30820 [--memory-contents]
30823 This command returns the set of collected objects, register names,
30824 trace state variable names, memory ranges and computed expressions
30825 that have been collected at a particular trace frame. The optional
30826 parameters to the command affect the output format in different ways.
30827 See the output description table below for more details.
30829 The reported names can be used in the normal manner to create
30830 varobjs and inspect the objects themselves. The items returned by
30831 this command are categorized so that it is clear which is a variable,
30832 which is a register, which is a trace state variable, which is a
30833 memory range and which is a computed expression.
30835 For instance, if the actions were
30837 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30838 collect *(int*)0xaf02bef0@@40
30842 the object collected in its entirety would be @code{myVar}. The
30843 object @code{myArray} would be partially collected, because only the
30844 element at index @code{myIndex} would be collected. The remaining
30845 objects would be computed expressions.
30847 An example output would be:
30851 -trace-frame-collected
30853 explicit-variables=[@{name="myVar",value="1"@}],
30854 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30855 @{name="myObj.field",value="0"@},
30856 @{name="myPtr->field",value="1"@},
30857 @{name="myCount + 2",value="3"@},
30858 @{name="$tvar1 + 1",value="43970027"@}],
30859 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30860 @{number="1",value="0x0"@},
30861 @{number="2",value="0x4"@},
30863 @{number="125",value="0x0"@}],
30864 tvars=[@{name="$tvar1",current="43970026"@}],
30865 memory=[@{address="0x0000000000602264",length="4"@},
30866 @{address="0x0000000000615bc0",length="4"@}]
30873 @item explicit-variables
30874 The set of objects that have been collected in their entirety (as
30875 opposed to collecting just a few elements of an array or a few struct
30876 members). For each object, its name and value are printed.
30877 The @code{--var-print-values} option affects how or whether the value
30878 field is output. If @var{var_pval} is 0, then print only the names;
30879 if it is 1, print also their values; and if it is 2, print the name,
30880 type and value for simple data types, and the name and type for
30881 arrays, structures and unions.
30883 @item computed-expressions
30884 The set of computed expressions that have been collected at the
30885 current trace frame. The @code{--comp-print-values} option affects
30886 this set like the @code{--var-print-values} option affects the
30887 @code{explicit-variables} set. See above.
30890 The registers that have been collected at the current trace frame.
30891 For each register collected, the name and current value are returned.
30892 The value is formatted according to the @code{--registers-format}
30893 option. See the @command{-data-list-register-values} command for a
30894 list of the allowed formats. The default is @samp{x}.
30897 The trace state variables that have been collected at the current
30898 trace frame. For each trace state variable collected, the name and
30899 current value are returned.
30902 The set of memory ranges that have been collected at the current trace
30903 frame. Its content is a list of tuples. Each tuple represents a
30904 collected memory range and has the following fields:
30908 The start address of the memory range, as hexadecimal literal.
30911 The length of the memory range, as decimal literal.
30914 The contents of the memory block, in hex. This field is only present
30915 if the @code{--memory-contents} option is specified.
30921 @subsubheading @value{GDBN} Command
30923 There is no corresponding @value{GDBN} command.
30925 @subsubheading Example
30927 @subheading -trace-list-variables
30928 @findex -trace-list-variables
30930 @subsubheading Synopsis
30933 -trace-list-variables
30936 Return a table of all defined trace variables. Each element of the
30937 table has the following fields:
30941 The name of the trace variable. This field is always present.
30944 The initial value. This is a 64-bit signed integer. This
30945 field is always present.
30948 The value the trace variable has at the moment. This is a 64-bit
30949 signed integer. This field is absent iff current value is
30950 not defined, for example if the trace was never run, or is
30955 @subsubheading @value{GDBN} Command
30957 The corresponding @value{GDBN} command is @samp{tvariables}.
30959 @subsubheading Example
30963 -trace-list-variables
30964 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30965 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30966 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30967 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30968 body=[variable=@{name="$trace_timestamp",initial="0"@}
30969 variable=@{name="$foo",initial="10",current="15"@}]@}
30973 @subheading -trace-save
30974 @findex -trace-save
30976 @subsubheading Synopsis
30979 -trace-save [ -r ] [ -ctf ] @var{filename}
30982 Saves the collected trace data to @var{filename}. Without the
30983 @samp{-r} option, the data is downloaded from the target and saved
30984 in a local file. With the @samp{-r} option the target is asked
30985 to perform the save.
30987 By default, this command will save the trace in the tfile format. You can
30988 supply the optional @samp{-ctf} argument to save it the CTF format. See
30989 @ref{Trace Files} for more information about CTF.
30991 @subsubheading @value{GDBN} Command
30993 The corresponding @value{GDBN} command is @samp{tsave}.
30996 @subheading -trace-start
30997 @findex -trace-start
30999 @subsubheading Synopsis
31005 Starts a tracing experiment. The result of this command does not
31008 @subsubheading @value{GDBN} Command
31010 The corresponding @value{GDBN} command is @samp{tstart}.
31012 @subheading -trace-status
31013 @findex -trace-status
31015 @subsubheading Synopsis
31021 Obtains the status of a tracing experiment. The result may include
31022 the following fields:
31027 May have a value of either @samp{0}, when no tracing operations are
31028 supported, @samp{1}, when all tracing operations are supported, or
31029 @samp{file} when examining trace file. In the latter case, examining
31030 of trace frame is possible but new tracing experiement cannot be
31031 started. This field is always present.
31034 May have a value of either @samp{0} or @samp{1} depending on whether
31035 tracing experiement is in progress on target. This field is present
31036 if @samp{supported} field is not @samp{0}.
31039 Report the reason why the tracing was stopped last time. This field
31040 may be absent iff tracing was never stopped on target yet. The
31041 value of @samp{request} means the tracing was stopped as result of
31042 the @code{-trace-stop} command. The value of @samp{overflow} means
31043 the tracing buffer is full. The value of @samp{disconnection} means
31044 tracing was automatically stopped when @value{GDBN} has disconnected.
31045 The value of @samp{passcount} means tracing was stopped when a
31046 tracepoint was passed a maximal number of times for that tracepoint.
31047 This field is present if @samp{supported} field is not @samp{0}.
31049 @item stopping-tracepoint
31050 The number of tracepoint whose passcount as exceeded. This field is
31051 present iff the @samp{stop-reason} field has the value of
31055 @itemx frames-created
31056 The @samp{frames} field is a count of the total number of trace frames
31057 in the trace buffer, while @samp{frames-created} is the total created
31058 during the run, including ones that were discarded, such as when a
31059 circular trace buffer filled up. Both fields are optional.
31063 These fields tell the current size of the tracing buffer and the
31064 remaining space. These fields are optional.
31067 The value of the circular trace buffer flag. @code{1} means that the
31068 trace buffer is circular and old trace frames will be discarded if
31069 necessary to make room, @code{0} means that the trace buffer is linear
31073 The value of the disconnected tracing flag. @code{1} means that
31074 tracing will continue after @value{GDBN} disconnects, @code{0} means
31075 that the trace run will stop.
31078 The filename of the trace file being examined. This field is
31079 optional, and only present when examining a trace file.
31083 @subsubheading @value{GDBN} Command
31085 The corresponding @value{GDBN} command is @samp{tstatus}.
31087 @subheading -trace-stop
31088 @findex -trace-stop
31090 @subsubheading Synopsis
31096 Stops a tracing experiment. The result of this command has the same
31097 fields as @code{-trace-status}, except that the @samp{supported} and
31098 @samp{running} fields are not output.
31100 @subsubheading @value{GDBN} Command
31102 The corresponding @value{GDBN} command is @samp{tstop}.
31105 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31106 @node GDB/MI Symbol Query
31107 @section @sc{gdb/mi} Symbol Query Commands
31111 @subheading The @code{-symbol-info-address} Command
31112 @findex -symbol-info-address
31114 @subsubheading Synopsis
31117 -symbol-info-address @var{symbol}
31120 Describe where @var{symbol} is stored.
31122 @subsubheading @value{GDBN} Command
31124 The corresponding @value{GDBN} command is @samp{info address}.
31126 @subsubheading Example
31130 @subheading The @code{-symbol-info-file} Command
31131 @findex -symbol-info-file
31133 @subsubheading Synopsis
31139 Show the file for the symbol.
31141 @subsubheading @value{GDBN} Command
31143 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31144 @samp{gdb_find_file}.
31146 @subsubheading Example
31150 @subheading The @code{-symbol-info-function} Command
31151 @findex -symbol-info-function
31153 @subsubheading Synopsis
31156 -symbol-info-function
31159 Show which function the symbol lives in.
31161 @subsubheading @value{GDBN} Command
31163 @samp{gdb_get_function} in @code{gdbtk}.
31165 @subsubheading Example
31169 @subheading The @code{-symbol-info-line} Command
31170 @findex -symbol-info-line
31172 @subsubheading Synopsis
31178 Show the core addresses of the code for a source line.
31180 @subsubheading @value{GDBN} Command
31182 The corresponding @value{GDBN} command is @samp{info line}.
31183 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31185 @subsubheading Example
31189 @subheading The @code{-symbol-info-symbol} Command
31190 @findex -symbol-info-symbol
31192 @subsubheading Synopsis
31195 -symbol-info-symbol @var{addr}
31198 Describe what symbol is at location @var{addr}.
31200 @subsubheading @value{GDBN} Command
31202 The corresponding @value{GDBN} command is @samp{info symbol}.
31204 @subsubheading Example
31208 @subheading The @code{-symbol-list-functions} Command
31209 @findex -symbol-list-functions
31211 @subsubheading Synopsis
31214 -symbol-list-functions
31217 List the functions in the executable.
31219 @subsubheading @value{GDBN} Command
31221 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31222 @samp{gdb_search} in @code{gdbtk}.
31224 @subsubheading Example
31229 @subheading The @code{-symbol-list-lines} Command
31230 @findex -symbol-list-lines
31232 @subsubheading Synopsis
31235 -symbol-list-lines @var{filename}
31238 Print the list of lines that contain code and their associated program
31239 addresses for the given source filename. The entries are sorted in
31240 ascending PC order.
31242 @subsubheading @value{GDBN} Command
31244 There is no corresponding @value{GDBN} command.
31246 @subsubheading Example
31249 -symbol-list-lines basics.c
31250 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31256 @subheading The @code{-symbol-list-types} Command
31257 @findex -symbol-list-types
31259 @subsubheading Synopsis
31265 List all the type names.
31267 @subsubheading @value{GDBN} Command
31269 The corresponding commands are @samp{info types} in @value{GDBN},
31270 @samp{gdb_search} in @code{gdbtk}.
31272 @subsubheading Example
31276 @subheading The @code{-symbol-list-variables} Command
31277 @findex -symbol-list-variables
31279 @subsubheading Synopsis
31282 -symbol-list-variables
31285 List all the global and static variable names.
31287 @subsubheading @value{GDBN} Command
31289 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31291 @subsubheading Example
31295 @subheading The @code{-symbol-locate} Command
31296 @findex -symbol-locate
31298 @subsubheading Synopsis
31304 @subsubheading @value{GDBN} Command
31306 @samp{gdb_loc} in @code{gdbtk}.
31308 @subsubheading Example
31312 @subheading The @code{-symbol-type} Command
31313 @findex -symbol-type
31315 @subsubheading Synopsis
31318 -symbol-type @var{variable}
31321 Show type of @var{variable}.
31323 @subsubheading @value{GDBN} Command
31325 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31326 @samp{gdb_obj_variable}.
31328 @subsubheading Example
31333 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31334 @node GDB/MI File Commands
31335 @section @sc{gdb/mi} File Commands
31337 This section describes the GDB/MI commands to specify executable file names
31338 and to read in and obtain symbol table information.
31340 @subheading The @code{-file-exec-and-symbols} Command
31341 @findex -file-exec-and-symbols
31343 @subsubheading Synopsis
31346 -file-exec-and-symbols @var{file}
31349 Specify the executable file to be debugged. This file is the one from
31350 which the symbol table is also read. If no file is specified, the
31351 command clears the executable and symbol information. If breakpoints
31352 are set when using this command with no arguments, @value{GDBN} will produce
31353 error messages. Otherwise, no output is produced, except a completion
31356 @subsubheading @value{GDBN} Command
31358 The corresponding @value{GDBN} command is @samp{file}.
31360 @subsubheading Example
31364 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31370 @subheading The @code{-file-exec-file} Command
31371 @findex -file-exec-file
31373 @subsubheading Synopsis
31376 -file-exec-file @var{file}
31379 Specify the executable file to be debugged. Unlike
31380 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31381 from this file. If used without argument, @value{GDBN} clears the information
31382 about the executable file. No output is produced, except a completion
31385 @subsubheading @value{GDBN} Command
31387 The corresponding @value{GDBN} command is @samp{exec-file}.
31389 @subsubheading Example
31393 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31400 @subheading The @code{-file-list-exec-sections} Command
31401 @findex -file-list-exec-sections
31403 @subsubheading Synopsis
31406 -file-list-exec-sections
31409 List the sections of the current executable file.
31411 @subsubheading @value{GDBN} Command
31413 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31414 information as this command. @code{gdbtk} has a corresponding command
31415 @samp{gdb_load_info}.
31417 @subsubheading Example
31422 @subheading The @code{-file-list-exec-source-file} Command
31423 @findex -file-list-exec-source-file
31425 @subsubheading Synopsis
31428 -file-list-exec-source-file
31431 List the line number, the current source file, and the absolute path
31432 to the current source file for the current executable. The macro
31433 information field has a value of @samp{1} or @samp{0} depending on
31434 whether or not the file includes preprocessor macro information.
31436 @subsubheading @value{GDBN} Command
31438 The @value{GDBN} equivalent is @samp{info source}
31440 @subsubheading Example
31444 123-file-list-exec-source-file
31445 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31450 @subheading The @code{-file-list-exec-source-files} Command
31451 @findex -file-list-exec-source-files
31453 @subsubheading Synopsis
31456 -file-list-exec-source-files
31459 List the source files for the current executable.
31461 It will always output both the filename and fullname (absolute file
31462 name) of a source file.
31464 @subsubheading @value{GDBN} Command
31466 The @value{GDBN} equivalent is @samp{info sources}.
31467 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31469 @subsubheading Example
31472 -file-list-exec-source-files
31474 @{file=foo.c,fullname=/home/foo.c@},
31475 @{file=/home/bar.c,fullname=/home/bar.c@},
31476 @{file=gdb_could_not_find_fullpath.c@}]
31481 @subheading The @code{-file-list-shared-libraries} Command
31482 @findex -file-list-shared-libraries
31484 @subsubheading Synopsis
31487 -file-list-shared-libraries
31490 List the shared libraries in the program.
31492 @subsubheading @value{GDBN} Command
31494 The corresponding @value{GDBN} command is @samp{info shared}.
31496 @subsubheading Example
31500 @subheading The @code{-file-list-symbol-files} Command
31501 @findex -file-list-symbol-files
31503 @subsubheading Synopsis
31506 -file-list-symbol-files
31511 @subsubheading @value{GDBN} Command
31513 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31515 @subsubheading Example
31520 @subheading The @code{-file-symbol-file} Command
31521 @findex -file-symbol-file
31523 @subsubheading Synopsis
31526 -file-symbol-file @var{file}
31529 Read symbol table info from the specified @var{file} argument. When
31530 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31531 produced, except for a completion notification.
31533 @subsubheading @value{GDBN} Command
31535 The corresponding @value{GDBN} command is @samp{symbol-file}.
31537 @subsubheading Example
31541 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31547 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31548 @node GDB/MI Memory Overlay Commands
31549 @section @sc{gdb/mi} Memory Overlay Commands
31551 The memory overlay commands are not implemented.
31553 @c @subheading -overlay-auto
31555 @c @subheading -overlay-list-mapping-state
31557 @c @subheading -overlay-list-overlays
31559 @c @subheading -overlay-map
31561 @c @subheading -overlay-off
31563 @c @subheading -overlay-on
31565 @c @subheading -overlay-unmap
31567 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31568 @node GDB/MI Signal Handling Commands
31569 @section @sc{gdb/mi} Signal Handling Commands
31571 Signal handling commands are not implemented.
31573 @c @subheading -signal-handle
31575 @c @subheading -signal-list-handle-actions
31577 @c @subheading -signal-list-signal-types
31581 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31582 @node GDB/MI Target Manipulation
31583 @section @sc{gdb/mi} Target Manipulation Commands
31586 @subheading The @code{-target-attach} Command
31587 @findex -target-attach
31589 @subsubheading Synopsis
31592 -target-attach @var{pid} | @var{gid} | @var{file}
31595 Attach to a process @var{pid} or a file @var{file} outside of
31596 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31597 group, the id previously returned by
31598 @samp{-list-thread-groups --available} must be used.
31600 @subsubheading @value{GDBN} Command
31602 The corresponding @value{GDBN} command is @samp{attach}.
31604 @subsubheading Example
31608 =thread-created,id="1"
31609 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31615 @subheading The @code{-target-compare-sections} Command
31616 @findex -target-compare-sections
31618 @subsubheading Synopsis
31621 -target-compare-sections [ @var{section} ]
31624 Compare data of section @var{section} on target to the exec file.
31625 Without the argument, all sections are compared.
31627 @subsubheading @value{GDBN} Command
31629 The @value{GDBN} equivalent is @samp{compare-sections}.
31631 @subsubheading Example
31636 @subheading The @code{-target-detach} Command
31637 @findex -target-detach
31639 @subsubheading Synopsis
31642 -target-detach [ @var{pid} | @var{gid} ]
31645 Detach from the remote target which normally resumes its execution.
31646 If either @var{pid} or @var{gid} is specified, detaches from either
31647 the specified process, or specified thread group. There's no output.
31649 @subsubheading @value{GDBN} Command
31651 The corresponding @value{GDBN} command is @samp{detach}.
31653 @subsubheading Example
31663 @subheading The @code{-target-disconnect} Command
31664 @findex -target-disconnect
31666 @subsubheading Synopsis
31672 Disconnect from the remote target. There's no output and the target is
31673 generally not resumed.
31675 @subsubheading @value{GDBN} Command
31677 The corresponding @value{GDBN} command is @samp{disconnect}.
31679 @subsubheading Example
31689 @subheading The @code{-target-download} Command
31690 @findex -target-download
31692 @subsubheading Synopsis
31698 Loads the executable onto the remote target.
31699 It prints out an update message every half second, which includes the fields:
31703 The name of the section.
31705 The size of what has been sent so far for that section.
31707 The size of the section.
31709 The total size of what was sent so far (the current and the previous sections).
31711 The size of the overall executable to download.
31715 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31716 @sc{gdb/mi} Output Syntax}).
31718 In addition, it prints the name and size of the sections, as they are
31719 downloaded. These messages include the following fields:
31723 The name of the section.
31725 The size of the section.
31727 The size of the overall executable to download.
31731 At the end, a summary is printed.
31733 @subsubheading @value{GDBN} Command
31735 The corresponding @value{GDBN} command is @samp{load}.
31737 @subsubheading Example
31739 Note: each status message appears on a single line. Here the messages
31740 have been broken down so that they can fit onto a page.
31745 +download,@{section=".text",section-size="6668",total-size="9880"@}
31746 +download,@{section=".text",section-sent="512",section-size="6668",
31747 total-sent="512",total-size="9880"@}
31748 +download,@{section=".text",section-sent="1024",section-size="6668",
31749 total-sent="1024",total-size="9880"@}
31750 +download,@{section=".text",section-sent="1536",section-size="6668",
31751 total-sent="1536",total-size="9880"@}
31752 +download,@{section=".text",section-sent="2048",section-size="6668",
31753 total-sent="2048",total-size="9880"@}
31754 +download,@{section=".text",section-sent="2560",section-size="6668",
31755 total-sent="2560",total-size="9880"@}
31756 +download,@{section=".text",section-sent="3072",section-size="6668",
31757 total-sent="3072",total-size="9880"@}
31758 +download,@{section=".text",section-sent="3584",section-size="6668",
31759 total-sent="3584",total-size="9880"@}
31760 +download,@{section=".text",section-sent="4096",section-size="6668",
31761 total-sent="4096",total-size="9880"@}
31762 +download,@{section=".text",section-sent="4608",section-size="6668",
31763 total-sent="4608",total-size="9880"@}
31764 +download,@{section=".text",section-sent="5120",section-size="6668",
31765 total-sent="5120",total-size="9880"@}
31766 +download,@{section=".text",section-sent="5632",section-size="6668",
31767 total-sent="5632",total-size="9880"@}
31768 +download,@{section=".text",section-sent="6144",section-size="6668",
31769 total-sent="6144",total-size="9880"@}
31770 +download,@{section=".text",section-sent="6656",section-size="6668",
31771 total-sent="6656",total-size="9880"@}
31772 +download,@{section=".init",section-size="28",total-size="9880"@}
31773 +download,@{section=".fini",section-size="28",total-size="9880"@}
31774 +download,@{section=".data",section-size="3156",total-size="9880"@}
31775 +download,@{section=".data",section-sent="512",section-size="3156",
31776 total-sent="7236",total-size="9880"@}
31777 +download,@{section=".data",section-sent="1024",section-size="3156",
31778 total-sent="7748",total-size="9880"@}
31779 +download,@{section=".data",section-sent="1536",section-size="3156",
31780 total-sent="8260",total-size="9880"@}
31781 +download,@{section=".data",section-sent="2048",section-size="3156",
31782 total-sent="8772",total-size="9880"@}
31783 +download,@{section=".data",section-sent="2560",section-size="3156",
31784 total-sent="9284",total-size="9880"@}
31785 +download,@{section=".data",section-sent="3072",section-size="3156",
31786 total-sent="9796",total-size="9880"@}
31787 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31794 @subheading The @code{-target-exec-status} Command
31795 @findex -target-exec-status
31797 @subsubheading Synopsis
31800 -target-exec-status
31803 Provide information on the state of the target (whether it is running or
31804 not, for instance).
31806 @subsubheading @value{GDBN} Command
31808 There's no equivalent @value{GDBN} command.
31810 @subsubheading Example
31814 @subheading The @code{-target-list-available-targets} Command
31815 @findex -target-list-available-targets
31817 @subsubheading Synopsis
31820 -target-list-available-targets
31823 List the possible targets to connect to.
31825 @subsubheading @value{GDBN} Command
31827 The corresponding @value{GDBN} command is @samp{help target}.
31829 @subsubheading Example
31833 @subheading The @code{-target-list-current-targets} Command
31834 @findex -target-list-current-targets
31836 @subsubheading Synopsis
31839 -target-list-current-targets
31842 Describe the current target.
31844 @subsubheading @value{GDBN} Command
31846 The corresponding information is printed by @samp{info file} (among
31849 @subsubheading Example
31853 @subheading The @code{-target-list-parameters} Command
31854 @findex -target-list-parameters
31856 @subsubheading Synopsis
31859 -target-list-parameters
31865 @subsubheading @value{GDBN} Command
31869 @subsubheading Example
31872 @subheading The @code{-target-flash-erase} Command
31873 @findex -target-flash-erase
31875 @subsubheading Synopsis
31878 -target-flash-erase
31881 Erases all known flash memory regions on the target.
31883 The corresponding @value{GDBN} command is @samp{flash-erase}.
31885 The output is a list of flash regions that have been erased, with starting
31886 addresses and memory region sizes.
31890 -target-flash-erase
31891 ^done,erased-regions=@{address="0x0",size="0x40000"@}
31895 @subheading The @code{-target-select} Command
31896 @findex -target-select
31898 @subsubheading Synopsis
31901 -target-select @var{type} @var{parameters @dots{}}
31904 Connect @value{GDBN} to the remote target. This command takes two args:
31908 The type of target, for instance @samp{remote}, etc.
31909 @item @var{parameters}
31910 Device names, host names and the like. @xref{Target Commands, ,
31911 Commands for Managing Targets}, for more details.
31914 The output is a connection notification, followed by the address at
31915 which the target program is, in the following form:
31918 ^connected,addr="@var{address}",func="@var{function name}",
31919 args=[@var{arg list}]
31922 @subsubheading @value{GDBN} Command
31924 The corresponding @value{GDBN} command is @samp{target}.
31926 @subsubheading Example
31930 -target-select remote /dev/ttya
31931 ^connected,addr="0xfe00a300",func="??",args=[]
31935 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31936 @node GDB/MI File Transfer Commands
31937 @section @sc{gdb/mi} File Transfer Commands
31940 @subheading The @code{-target-file-put} Command
31941 @findex -target-file-put
31943 @subsubheading Synopsis
31946 -target-file-put @var{hostfile} @var{targetfile}
31949 Copy file @var{hostfile} from the host system (the machine running
31950 @value{GDBN}) to @var{targetfile} on the target system.
31952 @subsubheading @value{GDBN} Command
31954 The corresponding @value{GDBN} command is @samp{remote put}.
31956 @subsubheading Example
31960 -target-file-put localfile remotefile
31966 @subheading The @code{-target-file-get} Command
31967 @findex -target-file-get
31969 @subsubheading Synopsis
31972 -target-file-get @var{targetfile} @var{hostfile}
31975 Copy file @var{targetfile} from the target system to @var{hostfile}
31976 on the host system.
31978 @subsubheading @value{GDBN} Command
31980 The corresponding @value{GDBN} command is @samp{remote get}.
31982 @subsubheading Example
31986 -target-file-get remotefile localfile
31992 @subheading The @code{-target-file-delete} Command
31993 @findex -target-file-delete
31995 @subsubheading Synopsis
31998 -target-file-delete @var{targetfile}
32001 Delete @var{targetfile} from the target system.
32003 @subsubheading @value{GDBN} Command
32005 The corresponding @value{GDBN} command is @samp{remote delete}.
32007 @subsubheading Example
32011 -target-file-delete remotefile
32017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32018 @node GDB/MI Ada Exceptions Commands
32019 @section Ada Exceptions @sc{gdb/mi} Commands
32021 @subheading The @code{-info-ada-exceptions} Command
32022 @findex -info-ada-exceptions
32024 @subsubheading Synopsis
32027 -info-ada-exceptions [ @var{regexp}]
32030 List all Ada exceptions defined within the program being debugged.
32031 With a regular expression @var{regexp}, only those exceptions whose
32032 names match @var{regexp} are listed.
32034 @subsubheading @value{GDBN} Command
32036 The corresponding @value{GDBN} command is @samp{info exceptions}.
32038 @subsubheading Result
32040 The result is a table of Ada exceptions. The following columns are
32041 defined for each exception:
32045 The name of the exception.
32048 The address of the exception.
32052 @subsubheading Example
32055 -info-ada-exceptions aint
32056 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32057 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32058 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32059 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32060 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32063 @subheading Catching Ada Exceptions
32065 The commands describing how to ask @value{GDBN} to stop when a program
32066 raises an exception are described at @ref{Ada Exception GDB/MI
32067 Catchpoint Commands}.
32070 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32071 @node GDB/MI Support Commands
32072 @section @sc{gdb/mi} Support Commands
32074 Since new commands and features get regularly added to @sc{gdb/mi},
32075 some commands are available to help front-ends query the debugger
32076 about support for these capabilities. Similarly, it is also possible
32077 to query @value{GDBN} about target support of certain features.
32079 @subheading The @code{-info-gdb-mi-command} Command
32080 @cindex @code{-info-gdb-mi-command}
32081 @findex -info-gdb-mi-command
32083 @subsubheading Synopsis
32086 -info-gdb-mi-command @var{cmd_name}
32089 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32091 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32092 is technically not part of the command name (@pxref{GDB/MI Input
32093 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32094 for ease of use, this command also accepts the form with the leading
32097 @subsubheading @value{GDBN} Command
32099 There is no corresponding @value{GDBN} command.
32101 @subsubheading Result
32103 The result is a tuple. There is currently only one field:
32107 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32108 @code{"false"} otherwise.
32112 @subsubheading Example
32114 Here is an example where the @sc{gdb/mi} command does not exist:
32117 -info-gdb-mi-command unsupported-command
32118 ^done,command=@{exists="false"@}
32122 And here is an example where the @sc{gdb/mi} command is known
32126 -info-gdb-mi-command symbol-list-lines
32127 ^done,command=@{exists="true"@}
32130 @subheading The @code{-list-features} Command
32131 @findex -list-features
32132 @cindex supported @sc{gdb/mi} features, list
32134 Returns a list of particular features of the MI protocol that
32135 this version of gdb implements. A feature can be a command,
32136 or a new field in an output of some command, or even an
32137 important bugfix. While a frontend can sometimes detect presence
32138 of a feature at runtime, it is easier to perform detection at debugger
32141 The command returns a list of strings, with each string naming an
32142 available feature. Each returned string is just a name, it does not
32143 have any internal structure. The list of possible feature names
32149 (gdb) -list-features
32150 ^done,result=["feature1","feature2"]
32153 The current list of features is:
32156 @item frozen-varobjs
32157 Indicates support for the @code{-var-set-frozen} command, as well
32158 as possible presense of the @code{frozen} field in the output
32159 of @code{-varobj-create}.
32160 @item pending-breakpoints
32161 Indicates support for the @option{-f} option to the @code{-break-insert}
32164 Indicates Python scripting support, Python-based
32165 pretty-printing commands, and possible presence of the
32166 @samp{display_hint} field in the output of @code{-var-list-children}
32168 Indicates support for the @code{-thread-info} command.
32169 @item data-read-memory-bytes
32170 Indicates support for the @code{-data-read-memory-bytes} and the
32171 @code{-data-write-memory-bytes} commands.
32172 @item breakpoint-notifications
32173 Indicates that changes to breakpoints and breakpoints created via the
32174 CLI will be announced via async records.
32175 @item ada-task-info
32176 Indicates support for the @code{-ada-task-info} command.
32177 @item language-option
32178 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32179 option (@pxref{Context management}).
32180 @item info-gdb-mi-command
32181 Indicates support for the @code{-info-gdb-mi-command} command.
32182 @item undefined-command-error-code
32183 Indicates support for the "undefined-command" error code in error result
32184 records, produced when trying to execute an undefined @sc{gdb/mi} command
32185 (@pxref{GDB/MI Result Records}).
32186 @item exec-run-start-option
32187 Indicates that the @code{-exec-run} command supports the @option{--start}
32188 option (@pxref{GDB/MI Program Execution}).
32191 @subheading The @code{-list-target-features} Command
32192 @findex -list-target-features
32194 Returns a list of particular features that are supported by the
32195 target. Those features affect the permitted MI commands, but
32196 unlike the features reported by the @code{-list-features} command, the
32197 features depend on which target GDB is using at the moment. Whenever
32198 a target can change, due to commands such as @code{-target-select},
32199 @code{-target-attach} or @code{-exec-run}, the list of target features
32200 may change, and the frontend should obtain it again.
32204 (gdb) -list-target-features
32205 ^done,result=["async"]
32208 The current list of features is:
32212 Indicates that the target is capable of asynchronous command
32213 execution, which means that @value{GDBN} will accept further commands
32214 while the target is running.
32217 Indicates that the target is capable of reverse execution.
32218 @xref{Reverse Execution}, for more information.
32222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32223 @node GDB/MI Miscellaneous Commands
32224 @section Miscellaneous @sc{gdb/mi} Commands
32226 @c @subheading -gdb-complete
32228 @subheading The @code{-gdb-exit} Command
32231 @subsubheading Synopsis
32237 Exit @value{GDBN} immediately.
32239 @subsubheading @value{GDBN} Command
32241 Approximately corresponds to @samp{quit}.
32243 @subsubheading Example
32253 @subheading The @code{-exec-abort} Command
32254 @findex -exec-abort
32256 @subsubheading Synopsis
32262 Kill the inferior running program.
32264 @subsubheading @value{GDBN} Command
32266 The corresponding @value{GDBN} command is @samp{kill}.
32268 @subsubheading Example
32273 @subheading The @code{-gdb-set} Command
32276 @subsubheading Synopsis
32282 Set an internal @value{GDBN} variable.
32283 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32285 @subsubheading @value{GDBN} Command
32287 The corresponding @value{GDBN} command is @samp{set}.
32289 @subsubheading Example
32299 @subheading The @code{-gdb-show} Command
32302 @subsubheading Synopsis
32308 Show the current value of a @value{GDBN} variable.
32310 @subsubheading @value{GDBN} Command
32312 The corresponding @value{GDBN} command is @samp{show}.
32314 @subsubheading Example
32323 @c @subheading -gdb-source
32326 @subheading The @code{-gdb-version} Command
32327 @findex -gdb-version
32329 @subsubheading Synopsis
32335 Show version information for @value{GDBN}. Used mostly in testing.
32337 @subsubheading @value{GDBN} Command
32339 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32340 default shows this information when you start an interactive session.
32342 @subsubheading Example
32344 @c This example modifies the actual output from GDB to avoid overfull
32350 ~Copyright 2000 Free Software Foundation, Inc.
32351 ~GDB is free software, covered by the GNU General Public License, and
32352 ~you are welcome to change it and/or distribute copies of it under
32353 ~ certain conditions.
32354 ~Type "show copying" to see the conditions.
32355 ~There is absolutely no warranty for GDB. Type "show warranty" for
32357 ~This GDB was configured as
32358 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32363 @subheading The @code{-list-thread-groups} Command
32364 @findex -list-thread-groups
32366 @subheading Synopsis
32369 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32372 Lists thread groups (@pxref{Thread groups}). When a single thread
32373 group is passed as the argument, lists the children of that group.
32374 When several thread group are passed, lists information about those
32375 thread groups. Without any parameters, lists information about all
32376 top-level thread groups.
32378 Normally, thread groups that are being debugged are reported.
32379 With the @samp{--available} option, @value{GDBN} reports thread groups
32380 available on the target.
32382 The output of this command may have either a @samp{threads} result or
32383 a @samp{groups} result. The @samp{thread} result has a list of tuples
32384 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32385 Information}). The @samp{groups} result has a list of tuples as value,
32386 each tuple describing a thread group. If top-level groups are
32387 requested (that is, no parameter is passed), or when several groups
32388 are passed, the output always has a @samp{groups} result. The format
32389 of the @samp{group} result is described below.
32391 To reduce the number of roundtrips it's possible to list thread groups
32392 together with their children, by passing the @samp{--recurse} option
32393 and the recursion depth. Presently, only recursion depth of 1 is
32394 permitted. If this option is present, then every reported thread group
32395 will also include its children, either as @samp{group} or
32396 @samp{threads} field.
32398 In general, any combination of option and parameters is permitted, with
32399 the following caveats:
32403 When a single thread group is passed, the output will typically
32404 be the @samp{threads} result. Because threads may not contain
32405 anything, the @samp{recurse} option will be ignored.
32408 When the @samp{--available} option is passed, limited information may
32409 be available. In particular, the list of threads of a process might
32410 be inaccessible. Further, specifying specific thread groups might
32411 not give any performance advantage over listing all thread groups.
32412 The frontend should assume that @samp{-list-thread-groups --available}
32413 is always an expensive operation and cache the results.
32417 The @samp{groups} result is a list of tuples, where each tuple may
32418 have the following fields:
32422 Identifier of the thread group. This field is always present.
32423 The identifier is an opaque string; frontends should not try to
32424 convert it to an integer, even though it might look like one.
32427 The type of the thread group. At present, only @samp{process} is a
32431 The target-specific process identifier. This field is only present
32432 for thread groups of type @samp{process} and only if the process exists.
32435 The exit code of this group's last exited thread, formatted in octal.
32436 This field is only present for thread groups of type @samp{process} and
32437 only if the process is not running.
32440 The number of children this thread group has. This field may be
32441 absent for an available thread group.
32444 This field has a list of tuples as value, each tuple describing a
32445 thread. It may be present if the @samp{--recurse} option is
32446 specified, and it's actually possible to obtain the threads.
32449 This field is a list of integers, each identifying a core that one
32450 thread of the group is running on. This field may be absent if
32451 such information is not available.
32454 The name of the executable file that corresponds to this thread group.
32455 The field is only present for thread groups of type @samp{process},
32456 and only if there is a corresponding executable file.
32460 @subheading Example
32464 -list-thread-groups
32465 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32466 -list-thread-groups 17
32467 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32468 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32469 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32470 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32471 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32472 -list-thread-groups --available
32473 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32474 -list-thread-groups --available --recurse 1
32475 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32476 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32477 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32478 -list-thread-groups --available --recurse 1 17 18
32479 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32480 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32481 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32484 @subheading The @code{-info-os} Command
32487 @subsubheading Synopsis
32490 -info-os [ @var{type} ]
32493 If no argument is supplied, the command returns a table of available
32494 operating-system-specific information types. If one of these types is
32495 supplied as an argument @var{type}, then the command returns a table
32496 of data of that type.
32498 The types of information available depend on the target operating
32501 @subsubheading @value{GDBN} Command
32503 The corresponding @value{GDBN} command is @samp{info os}.
32505 @subsubheading Example
32507 When run on a @sc{gnu}/Linux system, the output will look something
32513 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32514 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32515 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32516 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32517 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32519 item=@{col0="files",col1="Listing of all file descriptors",
32520 col2="File descriptors"@},
32521 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32522 col2="Kernel modules"@},
32523 item=@{col0="msg",col1="Listing of all message queues",
32524 col2="Message queues"@},
32525 item=@{col0="processes",col1="Listing of all processes",
32526 col2="Processes"@},
32527 item=@{col0="procgroups",col1="Listing of all process groups",
32528 col2="Process groups"@},
32529 item=@{col0="semaphores",col1="Listing of all semaphores",
32530 col2="Semaphores"@},
32531 item=@{col0="shm",col1="Listing of all shared-memory regions",
32532 col2="Shared-memory regions"@},
32533 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32535 item=@{col0="threads",col1="Listing of all threads",
32539 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32540 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32541 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32542 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32543 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32544 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32545 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32546 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32548 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32549 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32553 (Note that the MI output here includes a @code{"Title"} column that
32554 does not appear in command-line @code{info os}; this column is useful
32555 for MI clients that want to enumerate the types of data, such as in a
32556 popup menu, but is needless clutter on the command line, and
32557 @code{info os} omits it.)
32559 @subheading The @code{-add-inferior} Command
32560 @findex -add-inferior
32562 @subheading Synopsis
32568 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32569 inferior is not associated with any executable. Such association may
32570 be established with the @samp{-file-exec-and-symbols} command
32571 (@pxref{GDB/MI File Commands}). The command response has a single
32572 field, @samp{inferior}, whose value is the identifier of the
32573 thread group corresponding to the new inferior.
32575 @subheading Example
32580 ^done,inferior="i3"
32583 @subheading The @code{-interpreter-exec} Command
32584 @findex -interpreter-exec
32586 @subheading Synopsis
32589 -interpreter-exec @var{interpreter} @var{command}
32591 @anchor{-interpreter-exec}
32593 Execute the specified @var{command} in the given @var{interpreter}.
32595 @subheading @value{GDBN} Command
32597 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32599 @subheading Example
32603 -interpreter-exec console "break main"
32604 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32605 &"During symbol reading, bad structure-type format.\n"
32606 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32611 @subheading The @code{-inferior-tty-set} Command
32612 @findex -inferior-tty-set
32614 @subheading Synopsis
32617 -inferior-tty-set /dev/pts/1
32620 Set terminal for future runs of the program being debugged.
32622 @subheading @value{GDBN} Command
32624 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32626 @subheading Example
32630 -inferior-tty-set /dev/pts/1
32635 @subheading The @code{-inferior-tty-show} Command
32636 @findex -inferior-tty-show
32638 @subheading Synopsis
32644 Show terminal for future runs of program being debugged.
32646 @subheading @value{GDBN} Command
32648 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32650 @subheading Example
32654 -inferior-tty-set /dev/pts/1
32658 ^done,inferior_tty_terminal="/dev/pts/1"
32662 @subheading The @code{-enable-timings} Command
32663 @findex -enable-timings
32665 @subheading Synopsis
32668 -enable-timings [yes | no]
32671 Toggle the printing of the wallclock, user and system times for an MI
32672 command as a field in its output. This command is to help frontend
32673 developers optimize the performance of their code. No argument is
32674 equivalent to @samp{yes}.
32676 @subheading @value{GDBN} Command
32680 @subheading Example
32688 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32689 addr="0x080484ed",func="main",file="myprog.c",
32690 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32692 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32700 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32701 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32702 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32703 fullname="/home/nickrob/myprog.c",line="73"@}
32708 @chapter @value{GDBN} Annotations
32710 This chapter describes annotations in @value{GDBN}. Annotations were
32711 designed to interface @value{GDBN} to graphical user interfaces or other
32712 similar programs which want to interact with @value{GDBN} at a
32713 relatively high level.
32715 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32719 This is Edition @value{EDITION}, @value{DATE}.
32723 * Annotations Overview:: What annotations are; the general syntax.
32724 * Server Prefix:: Issuing a command without affecting user state.
32725 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32726 * Errors:: Annotations for error messages.
32727 * Invalidation:: Some annotations describe things now invalid.
32728 * Annotations for Running::
32729 Whether the program is running, how it stopped, etc.
32730 * Source Annotations:: Annotations describing source code.
32733 @node Annotations Overview
32734 @section What is an Annotation?
32735 @cindex annotations
32737 Annotations start with a newline character, two @samp{control-z}
32738 characters, and the name of the annotation. If there is no additional
32739 information associated with this annotation, the name of the annotation
32740 is followed immediately by a newline. If there is additional
32741 information, the name of the annotation is followed by a space, the
32742 additional information, and a newline. The additional information
32743 cannot contain newline characters.
32745 Any output not beginning with a newline and two @samp{control-z}
32746 characters denotes literal output from @value{GDBN}. Currently there is
32747 no need for @value{GDBN} to output a newline followed by two
32748 @samp{control-z} characters, but if there was such a need, the
32749 annotations could be extended with an @samp{escape} annotation which
32750 means those three characters as output.
32752 The annotation @var{level}, which is specified using the
32753 @option{--annotate} command line option (@pxref{Mode Options}), controls
32754 how much information @value{GDBN} prints together with its prompt,
32755 values of expressions, source lines, and other types of output. Level 0
32756 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32757 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32758 for programs that control @value{GDBN}, and level 2 annotations have
32759 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32760 Interface, annotate, GDB's Obsolete Annotations}).
32763 @kindex set annotate
32764 @item set annotate @var{level}
32765 The @value{GDBN} command @code{set annotate} sets the level of
32766 annotations to the specified @var{level}.
32768 @item show annotate
32769 @kindex show annotate
32770 Show the current annotation level.
32773 This chapter describes level 3 annotations.
32775 A simple example of starting up @value{GDBN} with annotations is:
32778 $ @kbd{gdb --annotate=3}
32780 Copyright 2003 Free Software Foundation, Inc.
32781 GDB is free software, covered by the GNU General Public License,
32782 and you are welcome to change it and/or distribute copies of it
32783 under certain conditions.
32784 Type "show copying" to see the conditions.
32785 There is absolutely no warranty for GDB. Type "show warranty"
32787 This GDB was configured as "i386-pc-linux-gnu"
32798 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32799 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32800 denotes a @samp{control-z} character) are annotations; the rest is
32801 output from @value{GDBN}.
32803 @node Server Prefix
32804 @section The Server Prefix
32805 @cindex server prefix
32807 If you prefix a command with @samp{server } then it will not affect
32808 the command history, nor will it affect @value{GDBN}'s notion of which
32809 command to repeat if @key{RET} is pressed on a line by itself. This
32810 means that commands can be run behind a user's back by a front-end in
32811 a transparent manner.
32813 The @code{server } prefix does not affect the recording of values into
32814 the value history; to print a value without recording it into the
32815 value history, use the @code{output} command instead of the
32816 @code{print} command.
32818 Using this prefix also disables confirmation requests
32819 (@pxref{confirmation requests}).
32822 @section Annotation for @value{GDBN} Input
32824 @cindex annotations for prompts
32825 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32826 to know when to send output, when the output from a given command is
32829 Different kinds of input each have a different @dfn{input type}. Each
32830 input type has three annotations: a @code{pre-} annotation, which
32831 denotes the beginning of any prompt which is being output, a plain
32832 annotation, which denotes the end of the prompt, and then a @code{post-}
32833 annotation which denotes the end of any echo which may (or may not) be
32834 associated with the input. For example, the @code{prompt} input type
32835 features the following annotations:
32843 The input types are
32846 @findex pre-prompt annotation
32847 @findex prompt annotation
32848 @findex post-prompt annotation
32850 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32852 @findex pre-commands annotation
32853 @findex commands annotation
32854 @findex post-commands annotation
32856 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32857 command. The annotations are repeated for each command which is input.
32859 @findex pre-overload-choice annotation
32860 @findex overload-choice annotation
32861 @findex post-overload-choice annotation
32862 @item overload-choice
32863 When @value{GDBN} wants the user to select between various overloaded functions.
32865 @findex pre-query annotation
32866 @findex query annotation
32867 @findex post-query annotation
32869 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32871 @findex pre-prompt-for-continue annotation
32872 @findex prompt-for-continue annotation
32873 @findex post-prompt-for-continue annotation
32874 @item prompt-for-continue
32875 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32876 expect this to work well; instead use @code{set height 0} to disable
32877 prompting. This is because the counting of lines is buggy in the
32878 presence of annotations.
32883 @cindex annotations for errors, warnings and interrupts
32885 @findex quit annotation
32890 This annotation occurs right before @value{GDBN} responds to an interrupt.
32892 @findex error annotation
32897 This annotation occurs right before @value{GDBN} responds to an error.
32899 Quit and error annotations indicate that any annotations which @value{GDBN} was
32900 in the middle of may end abruptly. For example, if a
32901 @code{value-history-begin} annotation is followed by a @code{error}, one
32902 cannot expect to receive the matching @code{value-history-end}. One
32903 cannot expect not to receive it either, however; an error annotation
32904 does not necessarily mean that @value{GDBN} is immediately returning all the way
32907 @findex error-begin annotation
32908 A quit or error annotation may be preceded by
32914 Any output between that and the quit or error annotation is the error
32917 Warning messages are not yet annotated.
32918 @c If we want to change that, need to fix warning(), type_error(),
32919 @c range_error(), and possibly other places.
32922 @section Invalidation Notices
32924 @cindex annotations for invalidation messages
32925 The following annotations say that certain pieces of state may have
32929 @findex frames-invalid annotation
32930 @item ^Z^Zframes-invalid
32932 The frames (for example, output from the @code{backtrace} command) may
32935 @findex breakpoints-invalid annotation
32936 @item ^Z^Zbreakpoints-invalid
32938 The breakpoints may have changed. For example, the user just added or
32939 deleted a breakpoint.
32942 @node Annotations for Running
32943 @section Running the Program
32944 @cindex annotations for running programs
32946 @findex starting annotation
32947 @findex stopping annotation
32948 When the program starts executing due to a @value{GDBN} command such as
32949 @code{step} or @code{continue},
32955 is output. When the program stops,
32961 is output. Before the @code{stopped} annotation, a variety of
32962 annotations describe how the program stopped.
32965 @findex exited annotation
32966 @item ^Z^Zexited @var{exit-status}
32967 The program exited, and @var{exit-status} is the exit status (zero for
32968 successful exit, otherwise nonzero).
32970 @findex signalled annotation
32971 @findex signal-name annotation
32972 @findex signal-name-end annotation
32973 @findex signal-string annotation
32974 @findex signal-string-end annotation
32975 @item ^Z^Zsignalled
32976 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32977 annotation continues:
32983 ^Z^Zsignal-name-end
32987 ^Z^Zsignal-string-end
32992 where @var{name} is the name of the signal, such as @code{SIGILL} or
32993 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32994 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32995 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32996 user's benefit and have no particular format.
32998 @findex signal annotation
33000 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33001 just saying that the program received the signal, not that it was
33002 terminated with it.
33004 @findex breakpoint annotation
33005 @item ^Z^Zbreakpoint @var{number}
33006 The program hit breakpoint number @var{number}.
33008 @findex watchpoint annotation
33009 @item ^Z^Zwatchpoint @var{number}
33010 The program hit watchpoint number @var{number}.
33013 @node Source Annotations
33014 @section Displaying Source
33015 @cindex annotations for source display
33017 @findex source annotation
33018 The following annotation is used instead of displaying source code:
33021 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33024 where @var{filename} is an absolute file name indicating which source
33025 file, @var{line} is the line number within that file (where 1 is the
33026 first line in the file), @var{character} is the character position
33027 within the file (where 0 is the first character in the file) (for most
33028 debug formats this will necessarily point to the beginning of a line),
33029 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33030 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33031 @var{addr} is the address in the target program associated with the
33032 source which is being displayed. The @var{addr} is in the form @samp{0x}
33033 followed by one or more lowercase hex digits (note that this does not
33034 depend on the language).
33036 @node JIT Interface
33037 @chapter JIT Compilation Interface
33038 @cindex just-in-time compilation
33039 @cindex JIT compilation interface
33041 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33042 interface. A JIT compiler is a program or library that generates native
33043 executable code at runtime and executes it, usually in order to achieve good
33044 performance while maintaining platform independence.
33046 Programs that use JIT compilation are normally difficult to debug because
33047 portions of their code are generated at runtime, instead of being loaded from
33048 object files, which is where @value{GDBN} normally finds the program's symbols
33049 and debug information. In order to debug programs that use JIT compilation,
33050 @value{GDBN} has an interface that allows the program to register in-memory
33051 symbol files with @value{GDBN} at runtime.
33053 If you are using @value{GDBN} to debug a program that uses this interface, then
33054 it should work transparently so long as you have not stripped the binary. If
33055 you are developing a JIT compiler, then the interface is documented in the rest
33056 of this chapter. At this time, the only known client of this interface is the
33059 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33060 JIT compiler communicates with @value{GDBN} by writing data into a global
33061 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33062 attaches, it reads a linked list of symbol files from the global variable to
33063 find existing code, and puts a breakpoint in the function so that it can find
33064 out about additional code.
33067 * Declarations:: Relevant C struct declarations
33068 * Registering Code:: Steps to register code
33069 * Unregistering Code:: Steps to unregister code
33070 * Custom Debug Info:: Emit debug information in a custom format
33074 @section JIT Declarations
33076 These are the relevant struct declarations that a C program should include to
33077 implement the interface:
33087 struct jit_code_entry
33089 struct jit_code_entry *next_entry;
33090 struct jit_code_entry *prev_entry;
33091 const char *symfile_addr;
33092 uint64_t symfile_size;
33095 struct jit_descriptor
33098 /* This type should be jit_actions_t, but we use uint32_t
33099 to be explicit about the bitwidth. */
33100 uint32_t action_flag;
33101 struct jit_code_entry *relevant_entry;
33102 struct jit_code_entry *first_entry;
33105 /* GDB puts a breakpoint in this function. */
33106 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33108 /* Make sure to specify the version statically, because the
33109 debugger may check the version before we can set it. */
33110 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33113 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33114 modifications to this global data properly, which can easily be done by putting
33115 a global mutex around modifications to these structures.
33117 @node Registering Code
33118 @section Registering Code
33120 To register code with @value{GDBN}, the JIT should follow this protocol:
33124 Generate an object file in memory with symbols and other desired debug
33125 information. The file must include the virtual addresses of the sections.
33128 Create a code entry for the file, which gives the start and size of the symbol
33132 Add it to the linked list in the JIT descriptor.
33135 Point the relevant_entry field of the descriptor at the entry.
33138 Set @code{action_flag} to @code{JIT_REGISTER} and call
33139 @code{__jit_debug_register_code}.
33142 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33143 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33144 new code. However, the linked list must still be maintained in order to allow
33145 @value{GDBN} to attach to a running process and still find the symbol files.
33147 @node Unregistering Code
33148 @section Unregistering Code
33150 If code is freed, then the JIT should use the following protocol:
33154 Remove the code entry corresponding to the code from the linked list.
33157 Point the @code{relevant_entry} field of the descriptor at the code entry.
33160 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33161 @code{__jit_debug_register_code}.
33164 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33165 and the JIT will leak the memory used for the associated symbol files.
33167 @node Custom Debug Info
33168 @section Custom Debug Info
33169 @cindex custom JIT debug info
33170 @cindex JIT debug info reader
33172 Generating debug information in platform-native file formats (like ELF
33173 or COFF) may be an overkill for JIT compilers; especially if all the
33174 debug info is used for is displaying a meaningful backtrace. The
33175 issue can be resolved by having the JIT writers decide on a debug info
33176 format and also provide a reader that parses the debug info generated
33177 by the JIT compiler. This section gives a brief overview on writing
33178 such a parser. More specific details can be found in the source file
33179 @file{gdb/jit-reader.in}, which is also installed as a header at
33180 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33182 The reader is implemented as a shared object (so this functionality is
33183 not available on platforms which don't allow loading shared objects at
33184 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33185 @code{jit-reader-unload} are provided, to be used to load and unload
33186 the readers from a preconfigured directory. Once loaded, the shared
33187 object is used the parse the debug information emitted by the JIT
33191 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33192 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33195 @node Using JIT Debug Info Readers
33196 @subsection Using JIT Debug Info Readers
33197 @kindex jit-reader-load
33198 @kindex jit-reader-unload
33200 Readers can be loaded and unloaded using the @code{jit-reader-load}
33201 and @code{jit-reader-unload} commands.
33204 @item jit-reader-load @var{reader}
33205 Load the JIT reader named @var{reader}, which is a shared
33206 object specified as either an absolute or a relative file name. In
33207 the latter case, @value{GDBN} will try to load the reader from a
33208 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33209 system (here @var{libdir} is the system library directory, often
33210 @file{/usr/local/lib}).
33212 Only one reader can be active at a time; trying to load a second
33213 reader when one is already loaded will result in @value{GDBN}
33214 reporting an error. A new JIT reader can be loaded by first unloading
33215 the current one using @code{jit-reader-unload} and then invoking
33216 @code{jit-reader-load}.
33218 @item jit-reader-unload
33219 Unload the currently loaded JIT reader.
33223 @node Writing JIT Debug Info Readers
33224 @subsection Writing JIT Debug Info Readers
33225 @cindex writing JIT debug info readers
33227 As mentioned, a reader is essentially a shared object conforming to a
33228 certain ABI. This ABI is described in @file{jit-reader.h}.
33230 @file{jit-reader.h} defines the structures, macros and functions
33231 required to write a reader. It is installed (along with
33232 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33233 the system include directory.
33235 Readers need to be released under a GPL compatible license. A reader
33236 can be declared as released under such a license by placing the macro
33237 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33239 The entry point for readers is the symbol @code{gdb_init_reader},
33240 which is expected to be a function with the prototype
33242 @findex gdb_init_reader
33244 extern struct gdb_reader_funcs *gdb_init_reader (void);
33247 @cindex @code{struct gdb_reader_funcs}
33249 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33250 functions. These functions are executed to read the debug info
33251 generated by the JIT compiler (@code{read}), to unwind stack frames
33252 (@code{unwind}) and to create canonical frame IDs
33253 (@code{get_Frame_id}). It also has a callback that is called when the
33254 reader is being unloaded (@code{destroy}). The struct looks like this
33257 struct gdb_reader_funcs
33259 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33260 int reader_version;
33262 /* For use by the reader. */
33265 gdb_read_debug_info *read;
33266 gdb_unwind_frame *unwind;
33267 gdb_get_frame_id *get_frame_id;
33268 gdb_destroy_reader *destroy;
33272 @cindex @code{struct gdb_symbol_callbacks}
33273 @cindex @code{struct gdb_unwind_callbacks}
33275 The callbacks are provided with another set of callbacks by
33276 @value{GDBN} to do their job. For @code{read}, these callbacks are
33277 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33278 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33279 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33280 files and new symbol tables inside those object files. @code{struct
33281 gdb_unwind_callbacks} has callbacks to read registers off the current
33282 frame and to write out the values of the registers in the previous
33283 frame. Both have a callback (@code{target_read}) to read bytes off the
33284 target's address space.
33286 @node In-Process Agent
33287 @chapter In-Process Agent
33288 @cindex debugging agent
33289 The traditional debugging model is conceptually low-speed, but works fine,
33290 because most bugs can be reproduced in debugging-mode execution. However,
33291 as multi-core or many-core processors are becoming mainstream, and
33292 multi-threaded programs become more and more popular, there should be more
33293 and more bugs that only manifest themselves at normal-mode execution, for
33294 example, thread races, because debugger's interference with the program's
33295 timing may conceal the bugs. On the other hand, in some applications,
33296 it is not feasible for the debugger to interrupt the program's execution
33297 long enough for the developer to learn anything helpful about its behavior.
33298 If the program's correctness depends on its real-time behavior, delays
33299 introduced by a debugger might cause the program to fail, even when the
33300 code itself is correct. It is useful to be able to observe the program's
33301 behavior without interrupting it.
33303 Therefore, traditional debugging model is too intrusive to reproduce
33304 some bugs. In order to reduce the interference with the program, we can
33305 reduce the number of operations performed by debugger. The
33306 @dfn{In-Process Agent}, a shared library, is running within the same
33307 process with inferior, and is able to perform some debugging operations
33308 itself. As a result, debugger is only involved when necessary, and
33309 performance of debugging can be improved accordingly. Note that
33310 interference with program can be reduced but can't be removed completely,
33311 because the in-process agent will still stop or slow down the program.
33313 The in-process agent can interpret and execute Agent Expressions
33314 (@pxref{Agent Expressions}) during performing debugging operations. The
33315 agent expressions can be used for different purposes, such as collecting
33316 data in tracepoints, and condition evaluation in breakpoints.
33318 @anchor{Control Agent}
33319 You can control whether the in-process agent is used as an aid for
33320 debugging with the following commands:
33323 @kindex set agent on
33325 Causes the in-process agent to perform some operations on behalf of the
33326 debugger. Just which operations requested by the user will be done
33327 by the in-process agent depends on the its capabilities. For example,
33328 if you request to evaluate breakpoint conditions in the in-process agent,
33329 and the in-process agent has such capability as well, then breakpoint
33330 conditions will be evaluated in the in-process agent.
33332 @kindex set agent off
33333 @item set agent off
33334 Disables execution of debugging operations by the in-process agent. All
33335 of the operations will be performed by @value{GDBN}.
33339 Display the current setting of execution of debugging operations by
33340 the in-process agent.
33344 * In-Process Agent Protocol::
33347 @node In-Process Agent Protocol
33348 @section In-Process Agent Protocol
33349 @cindex in-process agent protocol
33351 The in-process agent is able to communicate with both @value{GDBN} and
33352 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33353 used for communications between @value{GDBN} or GDBserver and the IPA.
33354 In general, @value{GDBN} or GDBserver sends commands
33355 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33356 in-process agent replies back with the return result of the command, or
33357 some other information. The data sent to in-process agent is composed
33358 of primitive data types, such as 4-byte or 8-byte type, and composite
33359 types, which are called objects (@pxref{IPA Protocol Objects}).
33362 * IPA Protocol Objects::
33363 * IPA Protocol Commands::
33366 @node IPA Protocol Objects
33367 @subsection IPA Protocol Objects
33368 @cindex ipa protocol objects
33370 The commands sent to and results received from agent may contain some
33371 complex data types called @dfn{objects}.
33373 The in-process agent is running on the same machine with @value{GDBN}
33374 or GDBserver, so it doesn't have to handle as much differences between
33375 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33376 However, there are still some differences of two ends in two processes:
33380 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33381 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33383 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33384 GDBserver is compiled with one, and in-process agent is compiled with
33388 Here are the IPA Protocol Objects:
33392 agent expression object. It represents an agent expression
33393 (@pxref{Agent Expressions}).
33394 @anchor{agent expression object}
33396 tracepoint action object. It represents a tracepoint action
33397 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33398 memory, static trace data and to evaluate expression.
33399 @anchor{tracepoint action object}
33401 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33402 @anchor{tracepoint object}
33406 The following table describes important attributes of each IPA protocol
33409 @multitable @columnfractions .30 .20 .50
33410 @headitem Name @tab Size @tab Description
33411 @item @emph{agent expression object} @tab @tab
33412 @item length @tab 4 @tab length of bytes code
33413 @item byte code @tab @var{length} @tab contents of byte code
33414 @item @emph{tracepoint action for collecting memory} @tab @tab
33415 @item 'M' @tab 1 @tab type of tracepoint action
33416 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33417 address of the lowest byte to collect, otherwise @var{addr} is the offset
33418 of @var{basereg} for memory collecting.
33419 @item len @tab 8 @tab length of memory for collecting
33420 @item basereg @tab 4 @tab the register number containing the starting
33421 memory address for collecting.
33422 @item @emph{tracepoint action for collecting registers} @tab @tab
33423 @item 'R' @tab 1 @tab type of tracepoint action
33424 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33425 @item 'L' @tab 1 @tab type of tracepoint action
33426 @item @emph{tracepoint action for expression evaluation} @tab @tab
33427 @item 'X' @tab 1 @tab type of tracepoint action
33428 @item agent expression @tab length of @tab @ref{agent expression object}
33429 @item @emph{tracepoint object} @tab @tab
33430 @item number @tab 4 @tab number of tracepoint
33431 @item address @tab 8 @tab address of tracepoint inserted on
33432 @item type @tab 4 @tab type of tracepoint
33433 @item enabled @tab 1 @tab enable or disable of tracepoint
33434 @item step_count @tab 8 @tab step
33435 @item pass_count @tab 8 @tab pass
33436 @item numactions @tab 4 @tab number of tracepoint actions
33437 @item hit count @tab 8 @tab hit count
33438 @item trace frame usage @tab 8 @tab trace frame usage
33439 @item compiled_cond @tab 8 @tab compiled condition
33440 @item orig_size @tab 8 @tab orig size
33441 @item condition @tab 4 if condition is NULL otherwise length of
33442 @ref{agent expression object}
33443 @tab zero if condition is NULL, otherwise is
33444 @ref{agent expression object}
33445 @item actions @tab variable
33446 @tab numactions number of @ref{tracepoint action object}
33449 @node IPA Protocol Commands
33450 @subsection IPA Protocol Commands
33451 @cindex ipa protocol commands
33453 The spaces in each command are delimiters to ease reading this commands
33454 specification. They don't exist in real commands.
33458 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33459 Installs a new fast tracepoint described by @var{tracepoint_object}
33460 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33461 head of @dfn{jumppad}, which is used to jump to data collection routine
33466 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33467 @var{target_address} is address of tracepoint in the inferior.
33468 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33469 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33470 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33471 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33478 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33479 is about to kill inferiors.
33487 @item probe_marker_at:@var{address}
33488 Asks in-process agent to probe the marker at @var{address}.
33495 @item unprobe_marker_at:@var{address}
33496 Asks in-process agent to unprobe the marker at @var{address}.
33500 @chapter Reporting Bugs in @value{GDBN}
33501 @cindex bugs in @value{GDBN}
33502 @cindex reporting bugs in @value{GDBN}
33504 Your bug reports play an essential role in making @value{GDBN} reliable.
33506 Reporting a bug may help you by bringing a solution to your problem, or it
33507 may not. But in any case the principal function of a bug report is to help
33508 the entire community by making the next version of @value{GDBN} work better. Bug
33509 reports are your contribution to the maintenance of @value{GDBN}.
33511 In order for a bug report to serve its purpose, you must include the
33512 information that enables us to fix the bug.
33515 * Bug Criteria:: Have you found a bug?
33516 * Bug Reporting:: How to report bugs
33520 @section Have You Found a Bug?
33521 @cindex bug criteria
33523 If you are not sure whether you have found a bug, here are some guidelines:
33526 @cindex fatal signal
33527 @cindex debugger crash
33528 @cindex crash of debugger
33530 If the debugger gets a fatal signal, for any input whatever, that is a
33531 @value{GDBN} bug. Reliable debuggers never crash.
33533 @cindex error on valid input
33535 If @value{GDBN} produces an error message for valid input, that is a
33536 bug. (Note that if you're cross debugging, the problem may also be
33537 somewhere in the connection to the target.)
33539 @cindex invalid input
33541 If @value{GDBN} does not produce an error message for invalid input,
33542 that is a bug. However, you should note that your idea of
33543 ``invalid input'' might be our idea of ``an extension'' or ``support
33544 for traditional practice''.
33547 If you are an experienced user of debugging tools, your suggestions
33548 for improvement of @value{GDBN} are welcome in any case.
33551 @node Bug Reporting
33552 @section How to Report Bugs
33553 @cindex bug reports
33554 @cindex @value{GDBN} bugs, reporting
33556 A number of companies and individuals offer support for @sc{gnu} products.
33557 If you obtained @value{GDBN} from a support organization, we recommend you
33558 contact that organization first.
33560 You can find contact information for many support companies and
33561 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33563 @c should add a web page ref...
33566 @ifset BUGURL_DEFAULT
33567 In any event, we also recommend that you submit bug reports for
33568 @value{GDBN}. The preferred method is to submit them directly using
33569 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33570 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33573 @strong{Do not send bug reports to @samp{info-gdb}, or to
33574 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33575 not want to receive bug reports. Those that do have arranged to receive
33578 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33579 serves as a repeater. The mailing list and the newsgroup carry exactly
33580 the same messages. Often people think of posting bug reports to the
33581 newsgroup instead of mailing them. This appears to work, but it has one
33582 problem which can be crucial: a newsgroup posting often lacks a mail
33583 path back to the sender. Thus, if we need to ask for more information,
33584 we may be unable to reach you. For this reason, it is better to send
33585 bug reports to the mailing list.
33587 @ifclear BUGURL_DEFAULT
33588 In any event, we also recommend that you submit bug reports for
33589 @value{GDBN} to @value{BUGURL}.
33593 The fundamental principle of reporting bugs usefully is this:
33594 @strong{report all the facts}. If you are not sure whether to state a
33595 fact or leave it out, state it!
33597 Often people omit facts because they think they know what causes the
33598 problem and assume that some details do not matter. Thus, you might
33599 assume that the name of the variable you use in an example does not matter.
33600 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33601 stray memory reference which happens to fetch from the location where that
33602 name is stored in memory; perhaps, if the name were different, the contents
33603 of that location would fool the debugger into doing the right thing despite
33604 the bug. Play it safe and give a specific, complete example. That is the
33605 easiest thing for you to do, and the most helpful.
33607 Keep in mind that the purpose of a bug report is to enable us to fix the
33608 bug. It may be that the bug has been reported previously, but neither
33609 you nor we can know that unless your bug report is complete and
33612 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33613 bell?'' Those bug reports are useless, and we urge everyone to
33614 @emph{refuse to respond to them} except to chide the sender to report
33617 To enable us to fix the bug, you should include all these things:
33621 The version of @value{GDBN}. @value{GDBN} announces it if you start
33622 with no arguments; you can also print it at any time using @code{show
33625 Without this, we will not know whether there is any point in looking for
33626 the bug in the current version of @value{GDBN}.
33629 The type of machine you are using, and the operating system name and
33633 The details of the @value{GDBN} build-time configuration.
33634 @value{GDBN} shows these details if you invoke it with the
33635 @option{--configuration} command-line option, or if you type
33636 @code{show configuration} at @value{GDBN}'s prompt.
33639 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33640 ``@value{GCC}--2.8.1''.
33643 What compiler (and its version) was used to compile the program you are
33644 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33645 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33646 to get this information; for other compilers, see the documentation for
33650 The command arguments you gave the compiler to compile your example and
33651 observe the bug. For example, did you use @samp{-O}? To guarantee
33652 you will not omit something important, list them all. A copy of the
33653 Makefile (or the output from make) is sufficient.
33655 If we were to try to guess the arguments, we would probably guess wrong
33656 and then we might not encounter the bug.
33659 A complete input script, and all necessary source files, that will
33663 A description of what behavior you observe that you believe is
33664 incorrect. For example, ``It gets a fatal signal.''
33666 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33667 will certainly notice it. But if the bug is incorrect output, we might
33668 not notice unless it is glaringly wrong. You might as well not give us
33669 a chance to make a mistake.
33671 Even if the problem you experience is a fatal signal, you should still
33672 say so explicitly. Suppose something strange is going on, such as, your
33673 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33674 the C library on your system. (This has happened!) Your copy might
33675 crash and ours would not. If you told us to expect a crash, then when
33676 ours fails to crash, we would know that the bug was not happening for
33677 us. If you had not told us to expect a crash, then we would not be able
33678 to draw any conclusion from our observations.
33681 @cindex recording a session script
33682 To collect all this information, you can use a session recording program
33683 such as @command{script}, which is available on many Unix systems.
33684 Just run your @value{GDBN} session inside @command{script} and then
33685 include the @file{typescript} file with your bug report.
33687 Another way to record a @value{GDBN} session is to run @value{GDBN}
33688 inside Emacs and then save the entire buffer to a file.
33691 If you wish to suggest changes to the @value{GDBN} source, send us context
33692 diffs. If you even discuss something in the @value{GDBN} source, refer to
33693 it by context, not by line number.
33695 The line numbers in our development sources will not match those in your
33696 sources. Your line numbers would convey no useful information to us.
33700 Here are some things that are not necessary:
33704 A description of the envelope of the bug.
33706 Often people who encounter a bug spend a lot of time investigating
33707 which changes to the input file will make the bug go away and which
33708 changes will not affect it.
33710 This is often time consuming and not very useful, because the way we
33711 will find the bug is by running a single example under the debugger
33712 with breakpoints, not by pure deduction from a series of examples.
33713 We recommend that you save your time for something else.
33715 Of course, if you can find a simpler example to report @emph{instead}
33716 of the original one, that is a convenience for us. Errors in the
33717 output will be easier to spot, running under the debugger will take
33718 less time, and so on.
33720 However, simplification is not vital; if you do not want to do this,
33721 report the bug anyway and send us the entire test case you used.
33724 A patch for the bug.
33726 A patch for the bug does help us if it is a good one. But do not omit
33727 the necessary information, such as the test case, on the assumption that
33728 a patch is all we need. We might see problems with your patch and decide
33729 to fix the problem another way, or we might not understand it at all.
33731 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33732 construct an example that will make the program follow a certain path
33733 through the code. If you do not send us the example, we will not be able
33734 to construct one, so we will not be able to verify that the bug is fixed.
33736 And if we cannot understand what bug you are trying to fix, or why your
33737 patch should be an improvement, we will not install it. A test case will
33738 help us to understand.
33741 A guess about what the bug is or what it depends on.
33743 Such guesses are usually wrong. Even we cannot guess right about such
33744 things without first using the debugger to find the facts.
33747 @c The readline documentation is distributed with the readline code
33748 @c and consists of the two following files:
33751 @c Use -I with makeinfo to point to the appropriate directory,
33752 @c environment var TEXINPUTS with TeX.
33753 @ifclear SYSTEM_READLINE
33754 @include rluser.texi
33755 @include hsuser.texi
33759 @appendix In Memoriam
33761 The @value{GDBN} project mourns the loss of the following long-time
33766 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33767 to Free Software in general. Outside of @value{GDBN}, he was known in
33768 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33770 @item Michael Snyder
33771 Michael was one of the Global Maintainers of the @value{GDBN} project,
33772 with contributions recorded as early as 1996, until 2011. In addition
33773 to his day to day participation, he was a large driving force behind
33774 adding Reverse Debugging to @value{GDBN}.
33777 Beyond their technical contributions to the project, they were also
33778 enjoyable members of the Free Software Community. We will miss them.
33780 @node Formatting Documentation
33781 @appendix Formatting Documentation
33783 @cindex @value{GDBN} reference card
33784 @cindex reference card
33785 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33786 for printing with PostScript or Ghostscript, in the @file{gdb}
33787 subdirectory of the main source directory@footnote{In
33788 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33789 release.}. If you can use PostScript or Ghostscript with your printer,
33790 you can print the reference card immediately with @file{refcard.ps}.
33792 The release also includes the source for the reference card. You
33793 can format it, using @TeX{}, by typing:
33799 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33800 mode on US ``letter'' size paper;
33801 that is, on a sheet 11 inches wide by 8.5 inches
33802 high. You will need to specify this form of printing as an option to
33803 your @sc{dvi} output program.
33805 @cindex documentation
33807 All the documentation for @value{GDBN} comes as part of the machine-readable
33808 distribution. The documentation is written in Texinfo format, which is
33809 a documentation system that uses a single source file to produce both
33810 on-line information and a printed manual. You can use one of the Info
33811 formatting commands to create the on-line version of the documentation
33812 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33814 @value{GDBN} includes an already formatted copy of the on-line Info
33815 version of this manual in the @file{gdb} subdirectory. The main Info
33816 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33817 subordinate files matching @samp{gdb.info*} in the same directory. If
33818 necessary, you can print out these files, or read them with any editor;
33819 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33820 Emacs or the standalone @code{info} program, available as part of the
33821 @sc{gnu} Texinfo distribution.
33823 If you want to format these Info files yourself, you need one of the
33824 Info formatting programs, such as @code{texinfo-format-buffer} or
33827 If you have @code{makeinfo} installed, and are in the top level
33828 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33829 version @value{GDBVN}), you can make the Info file by typing:
33836 If you want to typeset and print copies of this manual, you need @TeX{},
33837 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33838 Texinfo definitions file.
33840 @TeX{} is a typesetting program; it does not print files directly, but
33841 produces output files called @sc{dvi} files. To print a typeset
33842 document, you need a program to print @sc{dvi} files. If your system
33843 has @TeX{} installed, chances are it has such a program. The precise
33844 command to use depends on your system; @kbd{lpr -d} is common; another
33845 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33846 require a file name without any extension or a @samp{.dvi} extension.
33848 @TeX{} also requires a macro definitions file called
33849 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33850 written in Texinfo format. On its own, @TeX{} cannot either read or
33851 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33852 and is located in the @file{gdb-@var{version-number}/texinfo}
33855 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33856 typeset and print this manual. First switch to the @file{gdb}
33857 subdirectory of the main source directory (for example, to
33858 @file{gdb-@value{GDBVN}/gdb}) and type:
33864 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33866 @node Installing GDB
33867 @appendix Installing @value{GDBN}
33868 @cindex installation
33871 * Requirements:: Requirements for building @value{GDBN}
33872 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33873 * Separate Objdir:: Compiling @value{GDBN} in another directory
33874 * Config Names:: Specifying names for hosts and targets
33875 * Configure Options:: Summary of options for configure
33876 * System-wide configuration:: Having a system-wide init file
33880 @section Requirements for Building @value{GDBN}
33881 @cindex building @value{GDBN}, requirements for
33883 Building @value{GDBN} requires various tools and packages to be available.
33884 Other packages will be used only if they are found.
33886 @heading Tools/Packages Necessary for Building @value{GDBN}
33888 @item ISO C90 compiler
33889 @value{GDBN} is written in ISO C90. It should be buildable with any
33890 working C90 compiler, e.g.@: GCC.
33894 @heading Tools/Packages Optional for Building @value{GDBN}
33898 @value{GDBN} can use the Expat XML parsing library. This library may be
33899 included with your operating system distribution; if it is not, you
33900 can get the latest version from @url{http://expat.sourceforge.net}.
33901 The @file{configure} script will search for this library in several
33902 standard locations; if it is installed in an unusual path, you can
33903 use the @option{--with-libexpat-prefix} option to specify its location.
33909 Remote protocol memory maps (@pxref{Memory Map Format})
33911 Target descriptions (@pxref{Target Descriptions})
33913 Remote shared library lists (@xref{Library List Format},
33914 or alternatively @pxref{Library List Format for SVR4 Targets})
33916 MS-Windows shared libraries (@pxref{Shared Libraries})
33918 Traceframe info (@pxref{Traceframe Info Format})
33920 Branch trace (@pxref{Branch Trace Format},
33921 @pxref{Branch Trace Configuration Format})
33925 @cindex compressed debug sections
33926 @value{GDBN} will use the @samp{zlib} library, if available, to read
33927 compressed debug sections. Some linkers, such as GNU gold, are capable
33928 of producing binaries with compressed debug sections. If @value{GDBN}
33929 is compiled with @samp{zlib}, it will be able to read the debug
33930 information in such binaries.
33932 The @samp{zlib} library is likely included with your operating system
33933 distribution; if it is not, you can get the latest version from
33934 @url{http://zlib.net}.
33937 @value{GDBN}'s features related to character sets (@pxref{Character
33938 Sets}) require a functioning @code{iconv} implementation. If you are
33939 on a GNU system, then this is provided by the GNU C Library. Some
33940 other systems also provide a working @code{iconv}.
33942 If @value{GDBN} is using the @code{iconv} program which is installed
33943 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33944 This is done with @option{--with-iconv-bin} which specifies the
33945 directory that contains the @code{iconv} program.
33947 On systems without @code{iconv}, you can install GNU Libiconv. If you
33948 have previously installed Libiconv, you can use the
33949 @option{--with-libiconv-prefix} option to configure.
33951 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33952 arrange to build Libiconv if a directory named @file{libiconv} appears
33953 in the top-most source directory. If Libiconv is built this way, and
33954 if the operating system does not provide a suitable @code{iconv}
33955 implementation, then the just-built library will automatically be used
33956 by @value{GDBN}. One easy way to set this up is to download GNU
33957 Libiconv, unpack it, and then rename the directory holding the
33958 Libiconv source code to @samp{libiconv}.
33961 @node Running Configure
33962 @section Invoking the @value{GDBN} @file{configure} Script
33963 @cindex configuring @value{GDBN}
33964 @value{GDBN} comes with a @file{configure} script that automates the process
33965 of preparing @value{GDBN} for installation; you can then use @code{make} to
33966 build the @code{gdb} program.
33968 @c irrelevant in info file; it's as current as the code it lives with.
33969 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33970 look at the @file{README} file in the sources; we may have improved the
33971 installation procedures since publishing this manual.}
33974 The @value{GDBN} distribution includes all the source code you need for
33975 @value{GDBN} in a single directory, whose name is usually composed by
33976 appending the version number to @samp{gdb}.
33978 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33979 @file{gdb-@value{GDBVN}} directory. That directory contains:
33982 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33983 script for configuring @value{GDBN} and all its supporting libraries
33985 @item gdb-@value{GDBVN}/gdb
33986 the source specific to @value{GDBN} itself
33988 @item gdb-@value{GDBVN}/bfd
33989 source for the Binary File Descriptor library
33991 @item gdb-@value{GDBVN}/include
33992 @sc{gnu} include files
33994 @item gdb-@value{GDBVN}/libiberty
33995 source for the @samp{-liberty} free software library
33997 @item gdb-@value{GDBVN}/opcodes
33998 source for the library of opcode tables and disassemblers
34000 @item gdb-@value{GDBVN}/readline
34001 source for the @sc{gnu} command-line interface
34003 @item gdb-@value{GDBVN}/glob
34004 source for the @sc{gnu} filename pattern-matching subroutine
34006 @item gdb-@value{GDBVN}/mmalloc
34007 source for the @sc{gnu} memory-mapped malloc package
34010 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34011 from the @file{gdb-@var{version-number}} source directory, which in
34012 this example is the @file{gdb-@value{GDBVN}} directory.
34014 First switch to the @file{gdb-@var{version-number}} source directory
34015 if you are not already in it; then run @file{configure}. Pass the
34016 identifier for the platform on which @value{GDBN} will run as an
34022 cd gdb-@value{GDBVN}
34023 ./configure @var{host}
34028 where @var{host} is an identifier such as @samp{sun4} or
34029 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34030 (You can often leave off @var{host}; @file{configure} tries to guess the
34031 correct value by examining your system.)
34033 Running @samp{configure @var{host}} and then running @code{make} builds the
34034 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34035 libraries, then @code{gdb} itself. The configured source files, and the
34036 binaries, are left in the corresponding source directories.
34039 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34040 system does not recognize this automatically when you run a different
34041 shell, you may need to run @code{sh} on it explicitly:
34044 sh configure @var{host}
34047 If you run @file{configure} from a directory that contains source
34048 directories for multiple libraries or programs, such as the
34049 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34051 creates configuration files for every directory level underneath (unless
34052 you tell it not to, with the @samp{--norecursion} option).
34054 You should run the @file{configure} script from the top directory in the
34055 source tree, the @file{gdb-@var{version-number}} directory. If you run
34056 @file{configure} from one of the subdirectories, you will configure only
34057 that subdirectory. That is usually not what you want. In particular,
34058 if you run the first @file{configure} from the @file{gdb} subdirectory
34059 of the @file{gdb-@var{version-number}} directory, you will omit the
34060 configuration of @file{bfd}, @file{readline}, and other sibling
34061 directories of the @file{gdb} subdirectory. This leads to build errors
34062 about missing include files such as @file{bfd/bfd.h}.
34064 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34065 However, you should make sure that the shell on your path (named by
34066 the @samp{SHELL} environment variable) is publicly readable. Remember
34067 that @value{GDBN} uses the shell to start your program---some systems refuse to
34068 let @value{GDBN} debug child processes whose programs are not readable.
34070 @node Separate Objdir
34071 @section Compiling @value{GDBN} in Another Directory
34073 If you want to run @value{GDBN} versions for several host or target machines,
34074 you need a different @code{gdb} compiled for each combination of
34075 host and target. @file{configure} is designed to make this easy by
34076 allowing you to generate each configuration in a separate subdirectory,
34077 rather than in the source directory. If your @code{make} program
34078 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34079 @code{make} in each of these directories builds the @code{gdb}
34080 program specified there.
34082 To build @code{gdb} in a separate directory, run @file{configure}
34083 with the @samp{--srcdir} option to specify where to find the source.
34084 (You also need to specify a path to find @file{configure}
34085 itself from your working directory. If the path to @file{configure}
34086 would be the same as the argument to @samp{--srcdir}, you can leave out
34087 the @samp{--srcdir} option; it is assumed.)
34089 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34090 separate directory for a Sun 4 like this:
34094 cd gdb-@value{GDBVN}
34097 ../gdb-@value{GDBVN}/configure sun4
34102 When @file{configure} builds a configuration using a remote source
34103 directory, it creates a tree for the binaries with the same structure
34104 (and using the same names) as the tree under the source directory. In
34105 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34106 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34107 @file{gdb-sun4/gdb}.
34109 Make sure that your path to the @file{configure} script has just one
34110 instance of @file{gdb} in it. If your path to @file{configure} looks
34111 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34112 one subdirectory of @value{GDBN}, not the whole package. This leads to
34113 build errors about missing include files such as @file{bfd/bfd.h}.
34115 One popular reason to build several @value{GDBN} configurations in separate
34116 directories is to configure @value{GDBN} for cross-compiling (where
34117 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34118 programs that run on another machine---the @dfn{target}).
34119 You specify a cross-debugging target by
34120 giving the @samp{--target=@var{target}} option to @file{configure}.
34122 When you run @code{make} to build a program or library, you must run
34123 it in a configured directory---whatever directory you were in when you
34124 called @file{configure} (or one of its subdirectories).
34126 The @code{Makefile} that @file{configure} generates in each source
34127 directory also runs recursively. If you type @code{make} in a source
34128 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34129 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34130 will build all the required libraries, and then build GDB.
34132 When you have multiple hosts or targets configured in separate
34133 directories, you can run @code{make} on them in parallel (for example,
34134 if they are NFS-mounted on each of the hosts); they will not interfere
34138 @section Specifying Names for Hosts and Targets
34140 The specifications used for hosts and targets in the @file{configure}
34141 script are based on a three-part naming scheme, but some short predefined
34142 aliases are also supported. The full naming scheme encodes three pieces
34143 of information in the following pattern:
34146 @var{architecture}-@var{vendor}-@var{os}
34149 For example, you can use the alias @code{sun4} as a @var{host} argument,
34150 or as the value for @var{target} in a @code{--target=@var{target}}
34151 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34153 The @file{configure} script accompanying @value{GDBN} does not provide
34154 any query facility to list all supported host and target names or
34155 aliases. @file{configure} calls the Bourne shell script
34156 @code{config.sub} to map abbreviations to full names; you can read the
34157 script, if you wish, or you can use it to test your guesses on
34158 abbreviations---for example:
34161 % sh config.sub i386-linux
34163 % sh config.sub alpha-linux
34164 alpha-unknown-linux-gnu
34165 % sh config.sub hp9k700
34167 % sh config.sub sun4
34168 sparc-sun-sunos4.1.1
34169 % sh config.sub sun3
34170 m68k-sun-sunos4.1.1
34171 % sh config.sub i986v
34172 Invalid configuration `i986v': machine `i986v' not recognized
34176 @code{config.sub} is also distributed in the @value{GDBN} source
34177 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34179 @node Configure Options
34180 @section @file{configure} Options
34182 Here is a summary of the @file{configure} options and arguments that
34183 are most often useful for building @value{GDBN}. @file{configure} also has
34184 several other options not listed here. @inforef{What Configure
34185 Does,,configure.info}, for a full explanation of @file{configure}.
34188 configure @r{[}--help@r{]}
34189 @r{[}--prefix=@var{dir}@r{]}
34190 @r{[}--exec-prefix=@var{dir}@r{]}
34191 @r{[}--srcdir=@var{dirname}@r{]}
34192 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34193 @r{[}--target=@var{target}@r{]}
34198 You may introduce options with a single @samp{-} rather than
34199 @samp{--} if you prefer; but you may abbreviate option names if you use
34204 Display a quick summary of how to invoke @file{configure}.
34206 @item --prefix=@var{dir}
34207 Configure the source to install programs and files under directory
34210 @item --exec-prefix=@var{dir}
34211 Configure the source to install programs under directory
34214 @c avoid splitting the warning from the explanation:
34216 @item --srcdir=@var{dirname}
34217 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34218 @code{make} that implements the @code{VPATH} feature.}@*
34219 Use this option to make configurations in directories separate from the
34220 @value{GDBN} source directories. Among other things, you can use this to
34221 build (or maintain) several configurations simultaneously, in separate
34222 directories. @file{configure} writes configuration-specific files in
34223 the current directory, but arranges for them to use the source in the
34224 directory @var{dirname}. @file{configure} creates directories under
34225 the working directory in parallel to the source directories below
34228 @item --norecursion
34229 Configure only the directory level where @file{configure} is executed; do not
34230 propagate configuration to subdirectories.
34232 @item --target=@var{target}
34233 Configure @value{GDBN} for cross-debugging programs running on the specified
34234 @var{target}. Without this option, @value{GDBN} is configured to debug
34235 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34237 There is no convenient way to generate a list of all available targets.
34239 @item @var{host} @dots{}
34240 Configure @value{GDBN} to run on the specified @var{host}.
34242 There is no convenient way to generate a list of all available hosts.
34245 There are many other options available as well, but they are generally
34246 needed for special purposes only.
34248 @node System-wide configuration
34249 @section System-wide configuration and settings
34250 @cindex system-wide init file
34252 @value{GDBN} can be configured to have a system-wide init file;
34253 this file will be read and executed at startup (@pxref{Startup, , What
34254 @value{GDBN} does during startup}).
34256 Here is the corresponding configure option:
34259 @item --with-system-gdbinit=@var{file}
34260 Specify that the default location of the system-wide init file is
34264 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34265 it may be subject to relocation. Two possible cases:
34269 If the default location of this init file contains @file{$prefix},
34270 it will be subject to relocation. Suppose that the configure options
34271 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34272 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34273 init file is looked for as @file{$install/etc/gdbinit} instead of
34274 @file{$prefix/etc/gdbinit}.
34277 By contrast, if the default location does not contain the prefix,
34278 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34279 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34280 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34281 wherever @value{GDBN} is installed.
34284 If the configured location of the system-wide init file (as given by the
34285 @option{--with-system-gdbinit} option at configure time) is in the
34286 data-directory (as specified by @option{--with-gdb-datadir} at configure
34287 time) or in one of its subdirectories, then @value{GDBN} will look for the
34288 system-wide init file in the directory specified by the
34289 @option{--data-directory} command-line option.
34290 Note that the system-wide init file is only read once, during @value{GDBN}
34291 initialization. If the data-directory is changed after @value{GDBN} has
34292 started with the @code{set data-directory} command, the file will not be
34296 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34299 @node System-wide Configuration Scripts
34300 @subsection Installed System-wide Configuration Scripts
34301 @cindex system-wide configuration scripts
34303 The @file{system-gdbinit} directory, located inside the data-directory
34304 (as specified by @option{--with-gdb-datadir} at configure time) contains
34305 a number of scripts which can be used as system-wide init files. To
34306 automatically source those scripts at startup, @value{GDBN} should be
34307 configured with @option{--with-system-gdbinit}. Otherwise, any user
34308 should be able to source them by hand as needed.
34310 The following scripts are currently available:
34313 @item @file{elinos.py}
34315 @cindex ELinOS system-wide configuration script
34316 This script is useful when debugging a program on an ELinOS target.
34317 It takes advantage of the environment variables defined in a standard
34318 ELinOS environment in order to determine the location of the system
34319 shared libraries, and then sets the @samp{solib-absolute-prefix}
34320 and @samp{solib-search-path} variables appropriately.
34322 @item @file{wrs-linux.py}
34323 @pindex wrs-linux.py
34324 @cindex Wind River Linux system-wide configuration script
34325 This script is useful when debugging a program on a target running
34326 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34327 the host-side sysroot used by the target system.
34331 @node Maintenance Commands
34332 @appendix Maintenance Commands
34333 @cindex maintenance commands
34334 @cindex internal commands
34336 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34337 includes a number of commands intended for @value{GDBN} developers,
34338 that are not documented elsewhere in this manual. These commands are
34339 provided here for reference. (For commands that turn on debugging
34340 messages, see @ref{Debugging Output}.)
34343 @kindex maint agent
34344 @kindex maint agent-eval
34345 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34346 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34347 Translate the given @var{expression} into remote agent bytecodes.
34348 This command is useful for debugging the Agent Expression mechanism
34349 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34350 expression useful for data collection, such as by tracepoints, while
34351 @samp{maint agent-eval} produces an expression that evaluates directly
34352 to a result. For instance, a collection expression for @code{globa +
34353 globb} will include bytecodes to record four bytes of memory at each
34354 of the addresses of @code{globa} and @code{globb}, while discarding
34355 the result of the addition, while an evaluation expression will do the
34356 addition and return the sum.
34357 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34358 If not, generate remote agent bytecode for current frame PC address.
34360 @kindex maint agent-printf
34361 @item maint agent-printf @var{format},@var{expr},...
34362 Translate the given format string and list of argument expressions
34363 into remote agent bytecodes and display them as a disassembled list.
34364 This command is useful for debugging the agent version of dynamic
34365 printf (@pxref{Dynamic Printf}).
34367 @kindex maint info breakpoints
34368 @item @anchor{maint info breakpoints}maint info breakpoints
34369 Using the same format as @samp{info breakpoints}, display both the
34370 breakpoints you've set explicitly, and those @value{GDBN} is using for
34371 internal purposes. Internal breakpoints are shown with negative
34372 breakpoint numbers. The type column identifies what kind of breakpoint
34377 Normal, explicitly set breakpoint.
34380 Normal, explicitly set watchpoint.
34383 Internal breakpoint, used to handle correctly stepping through
34384 @code{longjmp} calls.
34386 @item longjmp resume
34387 Internal breakpoint at the target of a @code{longjmp}.
34390 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34393 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34396 Shared library events.
34400 @kindex maint info btrace
34401 @item maint info btrace
34402 Pint information about raw branch tracing data.
34404 @kindex maint btrace packet-history
34405 @item maint btrace packet-history
34406 Print the raw branch trace packets that are used to compute the
34407 execution history for the @samp{record btrace} command. Both the
34408 information and the format in which it is printed depend on the btrace
34413 For the BTS recording format, print a list of blocks of sequential
34414 code. For each block, the following information is printed:
34418 Newer blocks have higher numbers. The oldest block has number zero.
34419 @item Lowest @samp{PC}
34420 @item Highest @samp{PC}
34424 For the Intel Processor Trace recording format, print a list of
34425 Intel Processor Trace packets. For each packet, the following
34426 information is printed:
34429 @item Packet number
34430 Newer packets have higher numbers. The oldest packet has number zero.
34432 The packet's offset in the trace stream.
34433 @item Packet opcode and payload
34437 @kindex maint btrace clear-packet-history
34438 @item maint btrace clear-packet-history
34439 Discards the cached packet history printed by the @samp{maint btrace
34440 packet-history} command. The history will be computed again when
34443 @kindex maint btrace clear
34444 @item maint btrace clear
34445 Discard the branch trace data. The data will be fetched anew and the
34446 branch trace will be recomputed when needed.
34448 This implicitly truncates the branch trace to a single branch trace
34449 buffer. When updating branch trace incrementally, the branch trace
34450 available to @value{GDBN} may be bigger than a single branch trace
34453 @kindex maint set btrace pt skip-pad
34454 @item maint set btrace pt skip-pad
34455 @kindex maint show btrace pt skip-pad
34456 @item maint show btrace pt skip-pad
34457 Control whether @value{GDBN} will skip PAD packets when computing the
34460 @kindex set displaced-stepping
34461 @kindex show displaced-stepping
34462 @cindex displaced stepping support
34463 @cindex out-of-line single-stepping
34464 @item set displaced-stepping
34465 @itemx show displaced-stepping
34466 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34467 if the target supports it. Displaced stepping is a way to single-step
34468 over breakpoints without removing them from the inferior, by executing
34469 an out-of-line copy of the instruction that was originally at the
34470 breakpoint location. It is also known as out-of-line single-stepping.
34473 @item set displaced-stepping on
34474 If the target architecture supports it, @value{GDBN} will use
34475 displaced stepping to step over breakpoints.
34477 @item set displaced-stepping off
34478 @value{GDBN} will not use displaced stepping to step over breakpoints,
34479 even if such is supported by the target architecture.
34481 @cindex non-stop mode, and @samp{set displaced-stepping}
34482 @item set displaced-stepping auto
34483 This is the default mode. @value{GDBN} will use displaced stepping
34484 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34485 architecture supports displaced stepping.
34488 @kindex maint check-psymtabs
34489 @item maint check-psymtabs
34490 Check the consistency of currently expanded psymtabs versus symtabs.
34491 Use this to check, for example, whether a symbol is in one but not the other.
34493 @kindex maint check-symtabs
34494 @item maint check-symtabs
34495 Check the consistency of currently expanded symtabs.
34497 @kindex maint expand-symtabs
34498 @item maint expand-symtabs [@var{regexp}]
34499 Expand symbol tables.
34500 If @var{regexp} is specified, only expand symbol tables for file
34501 names matching @var{regexp}.
34503 @kindex maint set catch-demangler-crashes
34504 @kindex maint show catch-demangler-crashes
34505 @cindex demangler crashes
34506 @item maint set catch-demangler-crashes [on|off]
34507 @itemx maint show catch-demangler-crashes
34508 Control whether @value{GDBN} should attempt to catch crashes in the
34509 symbol name demangler. The default is to attempt to catch crashes.
34510 If enabled, the first time a crash is caught, a core file is created,
34511 the offending symbol is displayed and the user is presented with the
34512 option to terminate the current session.
34514 @kindex maint cplus first_component
34515 @item maint cplus first_component @var{name}
34516 Print the first C@t{++} class/namespace component of @var{name}.
34518 @kindex maint cplus namespace
34519 @item maint cplus namespace
34520 Print the list of possible C@t{++} namespaces.
34522 @kindex maint deprecate
34523 @kindex maint undeprecate
34524 @cindex deprecated commands
34525 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34526 @itemx maint undeprecate @var{command}
34527 Deprecate or undeprecate the named @var{command}. Deprecated commands
34528 cause @value{GDBN} to issue a warning when you use them. The optional
34529 argument @var{replacement} says which newer command should be used in
34530 favor of the deprecated one; if it is given, @value{GDBN} will mention
34531 the replacement as part of the warning.
34533 @kindex maint dump-me
34534 @item maint dump-me
34535 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34536 Cause a fatal signal in the debugger and force it to dump its core.
34537 This is supported only on systems which support aborting a program
34538 with the @code{SIGQUIT} signal.
34540 @kindex maint internal-error
34541 @kindex maint internal-warning
34542 @kindex maint demangler-warning
34543 @cindex demangler crashes
34544 @item maint internal-error @r{[}@var{message-text}@r{]}
34545 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34546 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34548 Cause @value{GDBN} to call the internal function @code{internal_error},
34549 @code{internal_warning} or @code{demangler_warning} and hence behave
34550 as though an internal problem has been detected. In addition to
34551 reporting the internal problem, these functions give the user the
34552 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34553 and @code{internal_warning}) create a core file of the current
34554 @value{GDBN} session.
34556 These commands take an optional parameter @var{message-text} that is
34557 used as the text of the error or warning message.
34559 Here's an example of using @code{internal-error}:
34562 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34563 @dots{}/maint.c:121: internal-error: testing, 1, 2
34564 A problem internal to GDB has been detected. Further
34565 debugging may prove unreliable.
34566 Quit this debugging session? (y or n) @kbd{n}
34567 Create a core file? (y or n) @kbd{n}
34571 @cindex @value{GDBN} internal error
34572 @cindex internal errors, control of @value{GDBN} behavior
34573 @cindex demangler crashes
34575 @kindex maint set internal-error
34576 @kindex maint show internal-error
34577 @kindex maint set internal-warning
34578 @kindex maint show internal-warning
34579 @kindex maint set demangler-warning
34580 @kindex maint show demangler-warning
34581 @item maint set internal-error @var{action} [ask|yes|no]
34582 @itemx maint show internal-error @var{action}
34583 @itemx maint set internal-warning @var{action} [ask|yes|no]
34584 @itemx maint show internal-warning @var{action}
34585 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34586 @itemx maint show demangler-warning @var{action}
34587 When @value{GDBN} reports an internal problem (error or warning) it
34588 gives the user the opportunity to both quit @value{GDBN} and create a
34589 core file of the current @value{GDBN} session. These commands let you
34590 override the default behaviour for each particular @var{action},
34591 described in the table below.
34595 You can specify that @value{GDBN} should always (yes) or never (no)
34596 quit. The default is to ask the user what to do.
34599 You can specify that @value{GDBN} should always (yes) or never (no)
34600 create a core file. The default is to ask the user what to do. Note
34601 that there is no @code{corefile} option for @code{demangler-warning}:
34602 demangler warnings always create a core file and this cannot be
34606 @kindex maint packet
34607 @item maint packet @var{text}
34608 If @value{GDBN} is talking to an inferior via the serial protocol,
34609 then this command sends the string @var{text} to the inferior, and
34610 displays the response packet. @value{GDBN} supplies the initial
34611 @samp{$} character, the terminating @samp{#} character, and the
34614 @kindex maint print architecture
34615 @item maint print architecture @r{[}@var{file}@r{]}
34616 Print the entire architecture configuration. The optional argument
34617 @var{file} names the file where the output goes.
34619 @kindex maint print c-tdesc
34620 @item maint print c-tdesc
34621 Print the current target description (@pxref{Target Descriptions}) as
34622 a C source file. The created source file can be used in @value{GDBN}
34623 when an XML parser is not available to parse the description.
34625 @kindex maint print dummy-frames
34626 @item maint print dummy-frames
34627 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34630 (@value{GDBP}) @kbd{b add}
34632 (@value{GDBP}) @kbd{print add(2,3)}
34633 Breakpoint 2, add (a=2, b=3) at @dots{}
34635 The program being debugged stopped while in a function called from GDB.
34637 (@value{GDBP}) @kbd{maint print dummy-frames}
34638 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34642 Takes an optional file parameter.
34644 @kindex maint print registers
34645 @kindex maint print raw-registers
34646 @kindex maint print cooked-registers
34647 @kindex maint print register-groups
34648 @kindex maint print remote-registers
34649 @item maint print registers @r{[}@var{file}@r{]}
34650 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34651 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34652 @itemx maint print register-groups @r{[}@var{file}@r{]}
34653 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34654 Print @value{GDBN}'s internal register data structures.
34656 The command @code{maint print raw-registers} includes the contents of
34657 the raw register cache; the command @code{maint print
34658 cooked-registers} includes the (cooked) value of all registers,
34659 including registers which aren't available on the target nor visible
34660 to user; the command @code{maint print register-groups} includes the
34661 groups that each register is a member of; and the command @code{maint
34662 print remote-registers} includes the remote target's register numbers
34663 and offsets in the `G' packets.
34665 These commands take an optional parameter, a file name to which to
34666 write the information.
34668 @kindex maint print reggroups
34669 @item maint print reggroups @r{[}@var{file}@r{]}
34670 Print @value{GDBN}'s internal register group data structures. The
34671 optional argument @var{file} tells to what file to write the
34674 The register groups info looks like this:
34677 (@value{GDBP}) @kbd{maint print reggroups}
34690 This command forces @value{GDBN} to flush its internal register cache.
34692 @kindex maint print objfiles
34693 @cindex info for known object files
34694 @item maint print objfiles @r{[}@var{regexp}@r{]}
34695 Print a dump of all known object files.
34696 If @var{regexp} is specified, only print object files whose names
34697 match @var{regexp}. For each object file, this command prints its name,
34698 address in memory, and all of its psymtabs and symtabs.
34700 @kindex maint print user-registers
34701 @cindex user registers
34702 @item maint print user-registers
34703 List all currently available @dfn{user registers}. User registers
34704 typically provide alternate names for actual hardware registers. They
34705 include the four ``standard'' registers @code{$fp}, @code{$pc},
34706 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34707 registers can be used in expressions in the same way as the canonical
34708 register names, but only the latter are listed by the @code{info
34709 registers} and @code{maint print registers} commands.
34711 @kindex maint print section-scripts
34712 @cindex info for known .debug_gdb_scripts-loaded scripts
34713 @item maint print section-scripts [@var{regexp}]
34714 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34715 If @var{regexp} is specified, only print scripts loaded by object files
34716 matching @var{regexp}.
34717 For each script, this command prints its name as specified in the objfile,
34718 and the full path if known.
34719 @xref{dotdebug_gdb_scripts section}.
34721 @kindex maint print statistics
34722 @cindex bcache statistics
34723 @item maint print statistics
34724 This command prints, for each object file in the program, various data
34725 about that object file followed by the byte cache (@dfn{bcache})
34726 statistics for the object file. The objfile data includes the number
34727 of minimal, partial, full, and stabs symbols, the number of types
34728 defined by the objfile, the number of as yet unexpanded psym tables,
34729 the number of line tables and string tables, and the amount of memory
34730 used by the various tables. The bcache statistics include the counts,
34731 sizes, and counts of duplicates of all and unique objects, max,
34732 average, and median entry size, total memory used and its overhead and
34733 savings, and various measures of the hash table size and chain
34736 @kindex maint print target-stack
34737 @cindex target stack description
34738 @item maint print target-stack
34739 A @dfn{target} is an interface between the debugger and a particular
34740 kind of file or process. Targets can be stacked in @dfn{strata},
34741 so that more than one target can potentially respond to a request.
34742 In particular, memory accesses will walk down the stack of targets
34743 until they find a target that is interested in handling that particular
34746 This command prints a short description of each layer that was pushed on
34747 the @dfn{target stack}, starting from the top layer down to the bottom one.
34749 @kindex maint print type
34750 @cindex type chain of a data type
34751 @item maint print type @var{expr}
34752 Print the type chain for a type specified by @var{expr}. The argument
34753 can be either a type name or a symbol. If it is a symbol, the type of
34754 that symbol is described. The type chain produced by this command is
34755 a recursive definition of the data type as stored in @value{GDBN}'s
34756 data structures, including its flags and contained types.
34758 @kindex maint selftest
34760 Run any self tests that were compiled in to @value{GDBN}. This will
34761 print a message showing how many tests were run, and how many failed.
34763 @kindex maint set dwarf always-disassemble
34764 @kindex maint show dwarf always-disassemble
34765 @item maint set dwarf always-disassemble
34766 @item maint show dwarf always-disassemble
34767 Control the behavior of @code{info address} when using DWARF debugging
34770 The default is @code{off}, which means that @value{GDBN} should try to
34771 describe a variable's location in an easily readable format. When
34772 @code{on}, @value{GDBN} will instead display the DWARF location
34773 expression in an assembly-like format. Note that some locations are
34774 too complex for @value{GDBN} to describe simply; in this case you will
34775 always see the disassembly form.
34777 Here is an example of the resulting disassembly:
34780 (gdb) info addr argc
34781 Symbol "argc" is a complex DWARF expression:
34785 For more information on these expressions, see
34786 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34788 @kindex maint set dwarf max-cache-age
34789 @kindex maint show dwarf max-cache-age
34790 @item maint set dwarf max-cache-age
34791 @itemx maint show dwarf max-cache-age
34792 Control the DWARF compilation unit cache.
34794 @cindex DWARF compilation units cache
34795 In object files with inter-compilation-unit references, such as those
34796 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34797 reader needs to frequently refer to previously read compilation units.
34798 This setting controls how long a compilation unit will remain in the
34799 cache if it is not referenced. A higher limit means that cached
34800 compilation units will be stored in memory longer, and more total
34801 memory will be used. Setting it to zero disables caching, which will
34802 slow down @value{GDBN} startup, but reduce memory consumption.
34804 @kindex maint set profile
34805 @kindex maint show profile
34806 @cindex profiling GDB
34807 @item maint set profile
34808 @itemx maint show profile
34809 Control profiling of @value{GDBN}.
34811 Profiling will be disabled until you use the @samp{maint set profile}
34812 command to enable it. When you enable profiling, the system will begin
34813 collecting timing and execution count data; when you disable profiling or
34814 exit @value{GDBN}, the results will be written to a log file. Remember that
34815 if you use profiling, @value{GDBN} will overwrite the profiling log file
34816 (often called @file{gmon.out}). If you have a record of important profiling
34817 data in a @file{gmon.out} file, be sure to move it to a safe location.
34819 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34820 compiled with the @samp{-pg} compiler option.
34822 @kindex maint set show-debug-regs
34823 @kindex maint show show-debug-regs
34824 @cindex hardware debug registers
34825 @item maint set show-debug-regs
34826 @itemx maint show show-debug-regs
34827 Control whether to show variables that mirror the hardware debug
34828 registers. Use @code{on} to enable, @code{off} to disable. If
34829 enabled, the debug registers values are shown when @value{GDBN} inserts or
34830 removes a hardware breakpoint or watchpoint, and when the inferior
34831 triggers a hardware-assisted breakpoint or watchpoint.
34833 @kindex maint set show-all-tib
34834 @kindex maint show show-all-tib
34835 @item maint set show-all-tib
34836 @itemx maint show show-all-tib
34837 Control whether to show all non zero areas within a 1k block starting
34838 at thread local base, when using the @samp{info w32 thread-information-block}
34841 @kindex maint set target-async
34842 @kindex maint show target-async
34843 @item maint set target-async
34844 @itemx maint show target-async
34845 This controls whether @value{GDBN} targets operate in synchronous or
34846 asynchronous mode (@pxref{Background Execution}). Normally the
34847 default is asynchronous, if it is available; but this can be changed
34848 to more easily debug problems occurring only in synchronous mode.
34850 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34851 @kindex maint show target-non-stop
34852 @item maint set target-non-stop
34853 @itemx maint show target-non-stop
34855 This controls whether @value{GDBN} targets always operate in non-stop
34856 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34857 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34858 if supported by the target.
34861 @item maint set target-non-stop auto
34862 This is the default mode. @value{GDBN} controls the target in
34863 non-stop mode if the target supports it.
34865 @item maint set target-non-stop on
34866 @value{GDBN} controls the target in non-stop mode even if the target
34867 does not indicate support.
34869 @item maint set target-non-stop off
34870 @value{GDBN} does not control the target in non-stop mode even if the
34871 target supports it.
34874 @kindex maint set per-command
34875 @kindex maint show per-command
34876 @item maint set per-command
34877 @itemx maint show per-command
34878 @cindex resources used by commands
34880 @value{GDBN} can display the resources used by each command.
34881 This is useful in debugging performance problems.
34884 @item maint set per-command space [on|off]
34885 @itemx maint show per-command space
34886 Enable or disable the printing of the memory used by GDB for each command.
34887 If enabled, @value{GDBN} will display how much memory each command
34888 took, following the command's own output.
34889 This can also be requested by invoking @value{GDBN} with the
34890 @option{--statistics} command-line switch (@pxref{Mode Options}).
34892 @item maint set per-command time [on|off]
34893 @itemx maint show per-command time
34894 Enable or disable the printing of the execution time of @value{GDBN}
34896 If enabled, @value{GDBN} will display how much time it
34897 took to execute each command, following the command's own output.
34898 Both CPU time and wallclock time are printed.
34899 Printing both is useful when trying to determine whether the cost is
34900 CPU or, e.g., disk/network latency.
34901 Note that the CPU time printed is for @value{GDBN} only, it does not include
34902 the execution time of the inferior because there's no mechanism currently
34903 to compute how much time was spent by @value{GDBN} and how much time was
34904 spent by the program been debugged.
34905 This can also be requested by invoking @value{GDBN} with the
34906 @option{--statistics} command-line switch (@pxref{Mode Options}).
34908 @item maint set per-command symtab [on|off]
34909 @itemx maint show per-command symtab
34910 Enable or disable the printing of basic symbol table statistics
34912 If enabled, @value{GDBN} will display the following information:
34916 number of symbol tables
34918 number of primary symbol tables
34920 number of blocks in the blockvector
34924 @kindex maint space
34925 @cindex memory used by commands
34926 @item maint space @var{value}
34927 An alias for @code{maint set per-command space}.
34928 A non-zero value enables it, zero disables it.
34931 @cindex time of command execution
34932 @item maint time @var{value}
34933 An alias for @code{maint set per-command time}.
34934 A non-zero value enables it, zero disables it.
34936 @kindex maint translate-address
34937 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34938 Find the symbol stored at the location specified by the address
34939 @var{addr} and an optional section name @var{section}. If found,
34940 @value{GDBN} prints the name of the closest symbol and an offset from
34941 the symbol's location to the specified address. This is similar to
34942 the @code{info address} command (@pxref{Symbols}), except that this
34943 command also allows to find symbols in other sections.
34945 If section was not specified, the section in which the symbol was found
34946 is also printed. For dynamically linked executables, the name of
34947 executable or shared library containing the symbol is printed as well.
34951 The following command is useful for non-interactive invocations of
34952 @value{GDBN}, such as in the test suite.
34955 @item set watchdog @var{nsec}
34956 @kindex set watchdog
34957 @cindex watchdog timer
34958 @cindex timeout for commands
34959 Set the maximum number of seconds @value{GDBN} will wait for the
34960 target operation to finish. If this time expires, @value{GDBN}
34961 reports and error and the command is aborted.
34963 @item show watchdog
34964 Show the current setting of the target wait timeout.
34967 @node Remote Protocol
34968 @appendix @value{GDBN} Remote Serial Protocol
34973 * Stop Reply Packets::
34974 * General Query Packets::
34975 * Architecture-Specific Protocol Details::
34976 * Tracepoint Packets::
34977 * Host I/O Packets::
34979 * Notification Packets::
34980 * Remote Non-Stop::
34981 * Packet Acknowledgment::
34983 * File-I/O Remote Protocol Extension::
34984 * Library List Format::
34985 * Library List Format for SVR4 Targets::
34986 * Memory Map Format::
34987 * Thread List Format::
34988 * Traceframe Info Format::
34989 * Branch Trace Format::
34990 * Branch Trace Configuration Format::
34996 There may be occasions when you need to know something about the
34997 protocol---for example, if there is only one serial port to your target
34998 machine, you might want your program to do something special if it
34999 recognizes a packet meant for @value{GDBN}.
35001 In the examples below, @samp{->} and @samp{<-} are used to indicate
35002 transmitted and received data, respectively.
35004 @cindex protocol, @value{GDBN} remote serial
35005 @cindex serial protocol, @value{GDBN} remote
35006 @cindex remote serial protocol
35007 All @value{GDBN} commands and responses (other than acknowledgments
35008 and notifications, see @ref{Notification Packets}) are sent as a
35009 @var{packet}. A @var{packet} is introduced with the character
35010 @samp{$}, the actual @var{packet-data}, and the terminating character
35011 @samp{#} followed by a two-digit @var{checksum}:
35014 @code{$}@var{packet-data}@code{#}@var{checksum}
35018 @cindex checksum, for @value{GDBN} remote
35020 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35021 characters between the leading @samp{$} and the trailing @samp{#} (an
35022 eight bit unsigned checksum).
35024 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35025 specification also included an optional two-digit @var{sequence-id}:
35028 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35031 @cindex sequence-id, for @value{GDBN} remote
35033 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35034 has never output @var{sequence-id}s. Stubs that handle packets added
35035 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35037 When either the host or the target machine receives a packet, the first
35038 response expected is an acknowledgment: either @samp{+} (to indicate
35039 the package was received correctly) or @samp{-} (to request
35043 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35048 The @samp{+}/@samp{-} acknowledgments can be disabled
35049 once a connection is established.
35050 @xref{Packet Acknowledgment}, for details.
35052 The host (@value{GDBN}) sends @var{command}s, and the target (the
35053 debugging stub incorporated in your program) sends a @var{response}. In
35054 the case of step and continue @var{command}s, the response is only sent
35055 when the operation has completed, and the target has again stopped all
35056 threads in all attached processes. This is the default all-stop mode
35057 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35058 execution mode; see @ref{Remote Non-Stop}, for details.
35060 @var{packet-data} consists of a sequence of characters with the
35061 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35064 @cindex remote protocol, field separator
35065 Fields within the packet should be separated using @samp{,} @samp{;} or
35066 @samp{:}. Except where otherwise noted all numbers are represented in
35067 @sc{hex} with leading zeros suppressed.
35069 Implementors should note that prior to @value{GDBN} 5.0, the character
35070 @samp{:} could not appear as the third character in a packet (as it
35071 would potentially conflict with the @var{sequence-id}).
35073 @cindex remote protocol, binary data
35074 @anchor{Binary Data}
35075 Binary data in most packets is encoded either as two hexadecimal
35076 digits per byte of binary data. This allowed the traditional remote
35077 protocol to work over connections which were only seven-bit clean.
35078 Some packets designed more recently assume an eight-bit clean
35079 connection, and use a more efficient encoding to send and receive
35082 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35083 as an escape character. Any escaped byte is transmitted as the escape
35084 character followed by the original character XORed with @code{0x20}.
35085 For example, the byte @code{0x7d} would be transmitted as the two
35086 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35087 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35088 @samp{@}}) must always be escaped. Responses sent by the stub
35089 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35090 is not interpreted as the start of a run-length encoded sequence
35093 Response @var{data} can be run-length encoded to save space.
35094 Run-length encoding replaces runs of identical characters with one
35095 instance of the repeated character, followed by a @samp{*} and a
35096 repeat count. The repeat count is itself sent encoded, to avoid
35097 binary characters in @var{data}: a value of @var{n} is sent as
35098 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35099 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35100 code 32) for a repeat count of 3. (This is because run-length
35101 encoding starts to win for counts 3 or more.) Thus, for example,
35102 @samp{0* } is a run-length encoding of ``0000'': the space character
35103 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35106 The printable characters @samp{#} and @samp{$} or with a numeric value
35107 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35108 seven repeats (@samp{$}) can be expanded using a repeat count of only
35109 five (@samp{"}). For example, @samp{00000000} can be encoded as
35112 The error response returned for some packets includes a two character
35113 error number. That number is not well defined.
35115 @cindex empty response, for unsupported packets
35116 For any @var{command} not supported by the stub, an empty response
35117 (@samp{$#00}) should be returned. That way it is possible to extend the
35118 protocol. A newer @value{GDBN} can tell if a packet is supported based
35121 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35122 commands for register access, and the @samp{m} and @samp{M} commands
35123 for memory access. Stubs that only control single-threaded targets
35124 can implement run control with the @samp{c} (continue), and @samp{s}
35125 (step) commands. Stubs that support multi-threading targets should
35126 support the @samp{vCont} command. All other commands are optional.
35131 The following table provides a complete list of all currently defined
35132 @var{command}s and their corresponding response @var{data}.
35133 @xref{File-I/O Remote Protocol Extension}, for details about the File
35134 I/O extension of the remote protocol.
35136 Each packet's description has a template showing the packet's overall
35137 syntax, followed by an explanation of the packet's meaning. We
35138 include spaces in some of the templates for clarity; these are not
35139 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35140 separate its components. For example, a template like @samp{foo
35141 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35142 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35143 @var{baz}. @value{GDBN} does not transmit a space character between the
35144 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35147 @cindex @var{thread-id}, in remote protocol
35148 @anchor{thread-id syntax}
35149 Several packets and replies include a @var{thread-id} field to identify
35150 a thread. Normally these are positive numbers with a target-specific
35151 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35152 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35155 In addition, the remote protocol supports a multiprocess feature in
35156 which the @var{thread-id} syntax is extended to optionally include both
35157 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35158 The @var{pid} (process) and @var{tid} (thread) components each have the
35159 format described above: a positive number with target-specific
35160 interpretation formatted as a big-endian hex string, literal @samp{-1}
35161 to indicate all processes or threads (respectively), or @samp{0} to
35162 indicate an arbitrary process or thread. Specifying just a process, as
35163 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35164 error to specify all processes but a specific thread, such as
35165 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35166 for those packets and replies explicitly documented to include a process
35167 ID, rather than a @var{thread-id}.
35169 The multiprocess @var{thread-id} syntax extensions are only used if both
35170 @value{GDBN} and the stub report support for the @samp{multiprocess}
35171 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35174 Note that all packet forms beginning with an upper- or lower-case
35175 letter, other than those described here, are reserved for future use.
35177 Here are the packet descriptions.
35182 @cindex @samp{!} packet
35183 @anchor{extended mode}
35184 Enable extended mode. In extended mode, the remote server is made
35185 persistent. The @samp{R} packet is used to restart the program being
35191 The remote target both supports and has enabled extended mode.
35195 @cindex @samp{?} packet
35197 Indicate the reason the target halted. The reply is the same as for
35198 step and continue. This packet has a special interpretation when the
35199 target is in non-stop mode; see @ref{Remote Non-Stop}.
35202 @xref{Stop Reply Packets}, for the reply specifications.
35204 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35205 @cindex @samp{A} packet
35206 Initialized @code{argv[]} array passed into program. @var{arglen}
35207 specifies the number of bytes in the hex encoded byte stream
35208 @var{arg}. See @code{gdbserver} for more details.
35213 The arguments were set.
35219 @cindex @samp{b} packet
35220 (Don't use this packet; its behavior is not well-defined.)
35221 Change the serial line speed to @var{baud}.
35223 JTC: @emph{When does the transport layer state change? When it's
35224 received, or after the ACK is transmitted. In either case, there are
35225 problems if the command or the acknowledgment packet is dropped.}
35227 Stan: @emph{If people really wanted to add something like this, and get
35228 it working for the first time, they ought to modify ser-unix.c to send
35229 some kind of out-of-band message to a specially-setup stub and have the
35230 switch happen "in between" packets, so that from remote protocol's point
35231 of view, nothing actually happened.}
35233 @item B @var{addr},@var{mode}
35234 @cindex @samp{B} packet
35235 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35236 breakpoint at @var{addr}.
35238 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35239 (@pxref{insert breakpoint or watchpoint packet}).
35241 @cindex @samp{bc} packet
35244 Backward continue. Execute the target system in reverse. No parameter.
35245 @xref{Reverse Execution}, for more information.
35248 @xref{Stop Reply Packets}, for the reply specifications.
35250 @cindex @samp{bs} packet
35253 Backward single step. Execute one instruction in reverse. No parameter.
35254 @xref{Reverse Execution}, for more information.
35257 @xref{Stop Reply Packets}, for the reply specifications.
35259 @item c @r{[}@var{addr}@r{]}
35260 @cindex @samp{c} packet
35261 Continue at @var{addr}, which is the address to resume. If @var{addr}
35262 is omitted, resume at current address.
35264 This packet is deprecated for multi-threading support. @xref{vCont
35268 @xref{Stop Reply Packets}, for the reply specifications.
35270 @item C @var{sig}@r{[};@var{addr}@r{]}
35271 @cindex @samp{C} packet
35272 Continue with signal @var{sig} (hex signal number). If
35273 @samp{;@var{addr}} is omitted, resume at same address.
35275 This packet is deprecated for multi-threading support. @xref{vCont
35279 @xref{Stop Reply Packets}, for the reply specifications.
35282 @cindex @samp{d} packet
35285 Don't use this packet; instead, define a general set packet
35286 (@pxref{General Query Packets}).
35290 @cindex @samp{D} packet
35291 The first form of the packet is used to detach @value{GDBN} from the
35292 remote system. It is sent to the remote target
35293 before @value{GDBN} disconnects via the @code{detach} command.
35295 The second form, including a process ID, is used when multiprocess
35296 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35297 detach only a specific process. The @var{pid} is specified as a
35298 big-endian hex string.
35308 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35309 @cindex @samp{F} packet
35310 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35311 This is part of the File-I/O protocol extension. @xref{File-I/O
35312 Remote Protocol Extension}, for the specification.
35315 @anchor{read registers packet}
35316 @cindex @samp{g} packet
35317 Read general registers.
35321 @item @var{XX@dots{}}
35322 Each byte of register data is described by two hex digits. The bytes
35323 with the register are transmitted in target byte order. The size of
35324 each register and their position within the @samp{g} packet are
35325 determined by the @value{GDBN} internal gdbarch functions
35326 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35328 When reading registers from a trace frame (@pxref{Analyze Collected
35329 Data,,Using the Collected Data}), the stub may also return a string of
35330 literal @samp{x}'s in place of the register data digits, to indicate
35331 that the corresponding register has not been collected, thus its value
35332 is unavailable. For example, for an architecture with 4 registers of
35333 4 bytes each, the following reply indicates to @value{GDBN} that
35334 registers 0 and 2 have not been collected, while registers 1 and 3
35335 have been collected, and both have zero value:
35339 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35346 @item G @var{XX@dots{}}
35347 @cindex @samp{G} packet
35348 Write general registers. @xref{read registers packet}, for a
35349 description of the @var{XX@dots{}} data.
35359 @item H @var{op} @var{thread-id}
35360 @cindex @samp{H} packet
35361 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35362 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35363 should be @samp{c} for step and continue operations (note that this
35364 is deprecated, supporting the @samp{vCont} command is a better
35365 option), and @samp{g} for other operations. The thread designator
35366 @var{thread-id} has the format and interpretation described in
35367 @ref{thread-id syntax}.
35378 @c 'H': How restrictive (or permissive) is the thread model. If a
35379 @c thread is selected and stopped, are other threads allowed
35380 @c to continue to execute? As I mentioned above, I think the
35381 @c semantics of each command when a thread is selected must be
35382 @c described. For example:
35384 @c 'g': If the stub supports threads and a specific thread is
35385 @c selected, returns the register block from that thread;
35386 @c otherwise returns current registers.
35388 @c 'G' If the stub supports threads and a specific thread is
35389 @c selected, sets the registers of the register block of
35390 @c that thread; otherwise sets current registers.
35392 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35393 @anchor{cycle step packet}
35394 @cindex @samp{i} packet
35395 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35396 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35397 step starting at that address.
35400 @cindex @samp{I} packet
35401 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35405 @cindex @samp{k} packet
35408 The exact effect of this packet is not specified.
35410 For a bare-metal target, it may power cycle or reset the target
35411 system. For that reason, the @samp{k} packet has no reply.
35413 For a single-process target, it may kill that process if possible.
35415 A multiple-process target may choose to kill just one process, or all
35416 that are under @value{GDBN}'s control. For more precise control, use
35417 the vKill packet (@pxref{vKill packet}).
35419 If the target system immediately closes the connection in response to
35420 @samp{k}, @value{GDBN} does not consider the lack of packet
35421 acknowledgment to be an error, and assumes the kill was successful.
35423 If connected using @kbd{target extended-remote}, and the target does
35424 not close the connection in response to a kill request, @value{GDBN}
35425 probes the target state as if a new connection was opened
35426 (@pxref{? packet}).
35428 @item m @var{addr},@var{length}
35429 @cindex @samp{m} packet
35430 Read @var{length} addressable memory units starting at address @var{addr}
35431 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35432 any particular boundary.
35434 The stub need not use any particular size or alignment when gathering
35435 data from memory for the response; even if @var{addr} is word-aligned
35436 and @var{length} is a multiple of the word size, the stub is free to
35437 use byte accesses, or not. For this reason, this packet may not be
35438 suitable for accessing memory-mapped I/O devices.
35439 @cindex alignment of remote memory accesses
35440 @cindex size of remote memory accesses
35441 @cindex memory, alignment and size of remote accesses
35445 @item @var{XX@dots{}}
35446 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35447 The reply may contain fewer addressable memory units than requested if the
35448 server was able to read only part of the region of memory.
35453 @item M @var{addr},@var{length}:@var{XX@dots{}}
35454 @cindex @samp{M} packet
35455 Write @var{length} addressable memory units starting at address @var{addr}
35456 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35457 byte is transmitted as a two-digit hexadecimal number.
35464 for an error (this includes the case where only part of the data was
35469 @cindex @samp{p} packet
35470 Read the value of register @var{n}; @var{n} is in hex.
35471 @xref{read registers packet}, for a description of how the returned
35472 register value is encoded.
35476 @item @var{XX@dots{}}
35477 the register's value
35481 Indicating an unrecognized @var{query}.
35484 @item P @var{n@dots{}}=@var{r@dots{}}
35485 @anchor{write register packet}
35486 @cindex @samp{P} packet
35487 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35488 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35489 digits for each byte in the register (target byte order).
35499 @item q @var{name} @var{params}@dots{}
35500 @itemx Q @var{name} @var{params}@dots{}
35501 @cindex @samp{q} packet
35502 @cindex @samp{Q} packet
35503 General query (@samp{q}) and set (@samp{Q}). These packets are
35504 described fully in @ref{General Query Packets}.
35507 @cindex @samp{r} packet
35508 Reset the entire system.
35510 Don't use this packet; use the @samp{R} packet instead.
35513 @cindex @samp{R} packet
35514 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35515 This packet is only available in extended mode (@pxref{extended mode}).
35517 The @samp{R} packet has no reply.
35519 @item s @r{[}@var{addr}@r{]}
35520 @cindex @samp{s} packet
35521 Single step, resuming at @var{addr}. If
35522 @var{addr} is omitted, resume at same address.
35524 This packet is deprecated for multi-threading support. @xref{vCont
35528 @xref{Stop Reply Packets}, for the reply specifications.
35530 @item S @var{sig}@r{[};@var{addr}@r{]}
35531 @anchor{step with signal packet}
35532 @cindex @samp{S} packet
35533 Step with signal. This is analogous to the @samp{C} packet, but
35534 requests a single-step, rather than a normal resumption of execution.
35536 This packet is deprecated for multi-threading support. @xref{vCont
35540 @xref{Stop Reply Packets}, for the reply specifications.
35542 @item t @var{addr}:@var{PP},@var{MM}
35543 @cindex @samp{t} packet
35544 Search backwards starting at address @var{addr} for a match with pattern
35545 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35546 There must be at least 3 digits in @var{addr}.
35548 @item T @var{thread-id}
35549 @cindex @samp{T} packet
35550 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35555 thread is still alive
35561 Packets starting with @samp{v} are identified by a multi-letter name,
35562 up to the first @samp{;} or @samp{?} (or the end of the packet).
35564 @item vAttach;@var{pid}
35565 @cindex @samp{vAttach} packet
35566 Attach to a new process with the specified process ID @var{pid}.
35567 The process ID is a
35568 hexadecimal integer identifying the process. In all-stop mode, all
35569 threads in the attached process are stopped; in non-stop mode, it may be
35570 attached without being stopped if that is supported by the target.
35572 @c In non-stop mode, on a successful vAttach, the stub should set the
35573 @c current thread to a thread of the newly-attached process. After
35574 @c attaching, GDB queries for the attached process's thread ID with qC.
35575 @c Also note that, from a user perspective, whether or not the
35576 @c target is stopped on attach in non-stop mode depends on whether you
35577 @c use the foreground or background version of the attach command, not
35578 @c on what vAttach does; GDB does the right thing with respect to either
35579 @c stopping or restarting threads.
35581 This packet is only available in extended mode (@pxref{extended mode}).
35587 @item @r{Any stop packet}
35588 for success in all-stop mode (@pxref{Stop Reply Packets})
35590 for success in non-stop mode (@pxref{Remote Non-Stop})
35593 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35594 @cindex @samp{vCont} packet
35595 @anchor{vCont packet}
35596 Resume the inferior, specifying different actions for each thread.
35598 For each inferior thread, the leftmost action with a matching
35599 @var{thread-id} is applied. Threads that don't match any action
35600 remain in their current state. Thread IDs are specified using the
35601 syntax described in @ref{thread-id syntax}. If multiprocess
35602 extensions (@pxref{multiprocess extensions}) are supported, actions
35603 can be specified to match all threads in a process by using the
35604 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
35605 @var{thread-id} matches all threads. Specifying no actions is an
35608 Currently supported actions are:
35614 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35618 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35621 @item r @var{start},@var{end}
35622 Step once, and then keep stepping as long as the thread stops at
35623 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35624 The remote stub reports a stop reply when either the thread goes out
35625 of the range or is stopped due to an unrelated reason, such as hitting
35626 a breakpoint. @xref{range stepping}.
35628 If the range is empty (@var{start} == @var{end}), then the action
35629 becomes equivalent to the @samp{s} action. In other words,
35630 single-step once, and report the stop (even if the stepped instruction
35631 jumps to @var{start}).
35633 (A stop reply may be sent at any point even if the PC is still within
35634 the stepping range; for example, it is valid to implement this packet
35635 in a degenerate way as a single instruction step operation.)
35639 The optional argument @var{addr} normally associated with the
35640 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35641 not supported in @samp{vCont}.
35643 The @samp{t} action is only relevant in non-stop mode
35644 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35645 A stop reply should be generated for any affected thread not already stopped.
35646 When a thread is stopped by means of a @samp{t} action,
35647 the corresponding stop reply should indicate that the thread has stopped with
35648 signal @samp{0}, regardless of whether the target uses some other signal
35649 as an implementation detail.
35651 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
35652 @samp{r} actions for threads that are already running. Conversely,
35653 the server must ignore @samp{t} actions for threads that are already
35656 @emph{Note:} In non-stop mode, a thread is considered running until
35657 @value{GDBN} acknowleges an asynchronous stop notification for it with
35658 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
35660 The stub must support @samp{vCont} if it reports support for
35661 multiprocess extensions (@pxref{multiprocess extensions}).
35664 @xref{Stop Reply Packets}, for the reply specifications.
35667 @cindex @samp{vCont?} packet
35668 Request a list of actions supported by the @samp{vCont} packet.
35672 @item vCont@r{[};@var{action}@dots{}@r{]}
35673 The @samp{vCont} packet is supported. Each @var{action} is a supported
35674 command in the @samp{vCont} packet.
35676 The @samp{vCont} packet is not supported.
35679 @anchor{vCtrlC packet}
35681 @cindex @samp{vCtrlC} packet
35682 Interrupt remote target as if a control-C was pressed on the remote
35683 terminal. This is the equivalent to reacting to the @code{^C}
35684 (@samp{\003}, the control-C character) character in all-stop mode
35685 while the target is running, except this works in non-stop mode.
35686 @xref{interrupting remote targets}, for more info on the all-stop
35697 @item vFile:@var{operation}:@var{parameter}@dots{}
35698 @cindex @samp{vFile} packet
35699 Perform a file operation on the target system. For details,
35700 see @ref{Host I/O Packets}.
35702 @item vFlashErase:@var{addr},@var{length}
35703 @cindex @samp{vFlashErase} packet
35704 Direct the stub to erase @var{length} bytes of flash starting at
35705 @var{addr}. The region may enclose any number of flash blocks, but
35706 its start and end must fall on block boundaries, as indicated by the
35707 flash block size appearing in the memory map (@pxref{Memory Map
35708 Format}). @value{GDBN} groups flash memory programming operations
35709 together, and sends a @samp{vFlashDone} request after each group; the
35710 stub is allowed to delay erase operation until the @samp{vFlashDone}
35711 packet is received.
35721 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35722 @cindex @samp{vFlashWrite} packet
35723 Direct the stub to write data to flash address @var{addr}. The data
35724 is passed in binary form using the same encoding as for the @samp{X}
35725 packet (@pxref{Binary Data}). The memory ranges specified by
35726 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35727 not overlap, and must appear in order of increasing addresses
35728 (although @samp{vFlashErase} packets for higher addresses may already
35729 have been received; the ordering is guaranteed only between
35730 @samp{vFlashWrite} packets). If a packet writes to an address that was
35731 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35732 target-specific method, the results are unpredictable.
35740 for vFlashWrite addressing non-flash memory
35746 @cindex @samp{vFlashDone} packet
35747 Indicate to the stub that flash programming operation is finished.
35748 The stub is permitted to delay or batch the effects of a group of
35749 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35750 @samp{vFlashDone} packet is received. The contents of the affected
35751 regions of flash memory are unpredictable until the @samp{vFlashDone}
35752 request is completed.
35754 @item vKill;@var{pid}
35755 @cindex @samp{vKill} packet
35756 @anchor{vKill packet}
35757 Kill the process with the specified process ID @var{pid}, which is a
35758 hexadecimal integer identifying the process. This packet is used in
35759 preference to @samp{k} when multiprocess protocol extensions are
35760 supported; see @ref{multiprocess extensions}.
35770 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35771 @cindex @samp{vRun} packet
35772 Run the program @var{filename}, passing it each @var{argument} on its
35773 command line. The file and arguments are hex-encoded strings. If
35774 @var{filename} is an empty string, the stub may use a default program
35775 (e.g.@: the last program run). The program is created in the stopped
35778 @c FIXME: What about non-stop mode?
35780 This packet is only available in extended mode (@pxref{extended mode}).
35786 @item @r{Any stop packet}
35787 for success (@pxref{Stop Reply Packets})
35791 @cindex @samp{vStopped} packet
35792 @xref{Notification Packets}.
35794 @item X @var{addr},@var{length}:@var{XX@dots{}}
35796 @cindex @samp{X} packet
35797 Write data to memory, where the data is transmitted in binary.
35798 Memory is specified by its address @var{addr} and number of addressable memory
35799 units @var{length} (@pxref{addressable memory unit});
35800 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35810 @item z @var{type},@var{addr},@var{kind}
35811 @itemx Z @var{type},@var{addr},@var{kind}
35812 @anchor{insert breakpoint or watchpoint packet}
35813 @cindex @samp{z} packet
35814 @cindex @samp{Z} packets
35815 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35816 watchpoint starting at address @var{address} of kind @var{kind}.
35818 Each breakpoint and watchpoint packet @var{type} is documented
35821 @emph{Implementation notes: A remote target shall return an empty string
35822 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35823 remote target shall support either both or neither of a given
35824 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35825 avoid potential problems with duplicate packets, the operations should
35826 be implemented in an idempotent way.}
35828 @item z0,@var{addr},@var{kind}
35829 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35830 @cindex @samp{z0} packet
35831 @cindex @samp{Z0} packet
35832 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
35833 @var{addr} of type @var{kind}.
35835 A software breakpoint is implemented by replacing the instruction at
35836 @var{addr} with a software breakpoint or trap instruction. The
35837 @var{kind} is target-specific and typically indicates the size of the
35838 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
35839 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35840 architectures have additional meanings for @var{kind}
35841 (@pxref{Architecture-Specific Protocol Details}); if no
35842 architecture-specific value is being used, it should be @samp{0}.
35843 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
35844 conditional expressions in bytecode form that should be evaluated on
35845 the target's side. These are the conditions that should be taken into
35846 consideration when deciding if the breakpoint trigger should be
35847 reported back to @value{GDBN}.
35849 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35850 for how to best report a software breakpoint event to @value{GDBN}.
35852 The @var{cond_list} parameter is comprised of a series of expressions,
35853 concatenated without separators. Each expression has the following form:
35857 @item X @var{len},@var{expr}
35858 @var{len} is the length of the bytecode expression and @var{expr} is the
35859 actual conditional expression in bytecode form.
35863 The optional @var{cmd_list} parameter introduces commands that may be
35864 run on the target, rather than being reported back to @value{GDBN}.
35865 The parameter starts with a numeric flag @var{persist}; if the flag is
35866 nonzero, then the breakpoint may remain active and the commands
35867 continue to be run even when @value{GDBN} disconnects from the target.
35868 Following this flag is a series of expressions concatenated with no
35869 separators. Each expression has the following form:
35873 @item X @var{len},@var{expr}
35874 @var{len} is the length of the bytecode expression and @var{expr} is the
35875 actual conditional expression in bytecode form.
35879 @emph{Implementation note: It is possible for a target to copy or move
35880 code that contains software breakpoints (e.g., when implementing
35881 overlays). The behavior of this packet, in the presence of such a
35882 target, is not defined.}
35894 @item z1,@var{addr},@var{kind}
35895 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35896 @cindex @samp{z1} packet
35897 @cindex @samp{Z1} packet
35898 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35899 address @var{addr}.
35901 A hardware breakpoint is implemented using a mechanism that is not
35902 dependent on being able to modify the target's memory. The
35903 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
35904 same meaning as in @samp{Z0} packets.
35906 @emph{Implementation note: A hardware breakpoint is not affected by code
35919 @item z2,@var{addr},@var{kind}
35920 @itemx Z2,@var{addr},@var{kind}
35921 @cindex @samp{z2} packet
35922 @cindex @samp{Z2} packet
35923 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35924 The number of bytes to watch is specified by @var{kind}.
35936 @item z3,@var{addr},@var{kind}
35937 @itemx Z3,@var{addr},@var{kind}
35938 @cindex @samp{z3} packet
35939 @cindex @samp{Z3} packet
35940 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35941 The number of bytes to watch is specified by @var{kind}.
35953 @item z4,@var{addr},@var{kind}
35954 @itemx Z4,@var{addr},@var{kind}
35955 @cindex @samp{z4} packet
35956 @cindex @samp{Z4} packet
35957 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35958 The number of bytes to watch is specified by @var{kind}.
35972 @node Stop Reply Packets
35973 @section Stop Reply Packets
35974 @cindex stop reply packets
35976 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35977 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35978 receive any of the below as a reply. Except for @samp{?}
35979 and @samp{vStopped}, that reply is only returned
35980 when the target halts. In the below the exact meaning of @dfn{signal
35981 number} is defined by the header @file{include/gdb/signals.h} in the
35982 @value{GDBN} source code.
35984 In non-stop mode, the server will simply reply @samp{OK} to commands
35985 such as @samp{vCont}; any stop will be the subject of a future
35986 notification. @xref{Remote Non-Stop}.
35988 As in the description of request packets, we include spaces in the
35989 reply templates for clarity; these are not part of the reply packet's
35990 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35996 The program received signal number @var{AA} (a two-digit hexadecimal
35997 number). This is equivalent to a @samp{T} response with no
35998 @var{n}:@var{r} pairs.
36000 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36001 @cindex @samp{T} packet reply
36002 The program received signal number @var{AA} (a two-digit hexadecimal
36003 number). This is equivalent to an @samp{S} response, except that the
36004 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36005 and other information directly in the stop reply packet, reducing
36006 round-trip latency. Single-step and breakpoint traps are reported
36007 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36011 If @var{n} is a hexadecimal number, it is a register number, and the
36012 corresponding @var{r} gives that register's value. The data @var{r} is a
36013 series of bytes in target byte order, with each byte given by a
36014 two-digit hex number.
36017 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36018 the stopped thread, as specified in @ref{thread-id syntax}.
36021 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36022 the core on which the stop event was detected.
36025 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36026 specific event that stopped the target. The currently defined stop
36027 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36028 signal. At most one stop reason should be present.
36031 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36032 and go on to the next; this allows us to extend the protocol in the
36036 The currently defined stop reasons are:
36042 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36045 @item syscall_entry
36046 @itemx syscall_return
36047 The packet indicates a syscall entry or return, and @var{r} is the
36048 syscall number, in hex.
36050 @cindex shared library events, remote reply
36052 The packet indicates that the loaded libraries have changed.
36053 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36054 list of loaded libraries. The @var{r} part is ignored.
36056 @cindex replay log events, remote reply
36058 The packet indicates that the target cannot continue replaying
36059 logged execution events, because it has reached the end (or the
36060 beginning when executing backward) of the log. The value of @var{r}
36061 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36062 for more information.
36065 @anchor{swbreak stop reason}
36066 The packet indicates a software breakpoint instruction was executed,
36067 irrespective of whether it was @value{GDBN} that planted the
36068 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36069 part must be left empty.
36071 On some architectures, such as x86, at the architecture level, when a
36072 breakpoint instruction executes the program counter points at the
36073 breakpoint address plus an offset. On such targets, the stub is
36074 responsible for adjusting the PC to point back at the breakpoint
36077 This packet should not be sent by default; older @value{GDBN} versions
36078 did not support it. @value{GDBN} requests it, by supplying an
36079 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36080 remote stub must also supply the appropriate @samp{qSupported} feature
36081 indicating support.
36083 This packet is required for correct non-stop mode operation.
36086 The packet indicates the target stopped for a hardware breakpoint.
36087 The @var{r} part must be left empty.
36089 The same remarks about @samp{qSupported} and non-stop mode above
36092 @cindex fork events, remote reply
36094 The packet indicates that @code{fork} was called, and @var{r}
36095 is the thread ID of the new child process. Refer to
36096 @ref{thread-id syntax} for the format of the @var{thread-id}
36097 field. This packet is only applicable to targets that support
36100 This packet should not be sent by default; older @value{GDBN} versions
36101 did not support it. @value{GDBN} requests it, by supplying an
36102 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36103 remote stub must also supply the appropriate @samp{qSupported} feature
36104 indicating support.
36106 @cindex vfork events, remote reply
36108 The packet indicates that @code{vfork} was called, and @var{r}
36109 is the thread ID of the new child process. Refer to
36110 @ref{thread-id syntax} for the format of the @var{thread-id}
36111 field. This packet is only applicable to targets that support
36114 This packet should not be sent by default; older @value{GDBN} versions
36115 did not support it. @value{GDBN} requests it, by supplying an
36116 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36117 remote stub must also supply the appropriate @samp{qSupported} feature
36118 indicating support.
36120 @cindex vforkdone events, remote reply
36122 The packet indicates that a child process created by a vfork
36123 has either called @code{exec} or terminated, so that the
36124 address spaces of the parent and child process are no longer
36125 shared. The @var{r} part is ignored. This packet is only
36126 applicable to targets that support vforkdone events.
36128 This packet should not be sent by default; older @value{GDBN} versions
36129 did not support it. @value{GDBN} requests it, by supplying an
36130 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36131 remote stub must also supply the appropriate @samp{qSupported} feature
36132 indicating support.
36134 @cindex exec events, remote reply
36136 The packet indicates that @code{execve} was called, and @var{r}
36137 is the absolute pathname of the file that was executed, in hex.
36138 This packet is only applicable to targets that support exec events.
36140 This packet should not be sent by default; older @value{GDBN} versions
36141 did not support it. @value{GDBN} requests it, by supplying an
36142 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36143 remote stub must also supply the appropriate @samp{qSupported} feature
36144 indicating support.
36146 @cindex thread create event, remote reply
36147 @anchor{thread create event}
36149 The packet indicates that the thread was just created. The new thread
36150 is stopped until @value{GDBN} sets it running with a resumption packet
36151 (@pxref{vCont packet}). This packet should not be sent by default;
36152 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36153 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36154 @var{r} part is ignored.
36159 @itemx W @var{AA} ; process:@var{pid}
36160 The process exited, and @var{AA} is the exit status. This is only
36161 applicable to certain targets.
36163 The second form of the response, including the process ID of the
36164 exited process, can be used only when @value{GDBN} has reported
36165 support for multiprocess protocol extensions; see @ref{multiprocess
36166 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36170 @itemx X @var{AA} ; process:@var{pid}
36171 The process terminated with signal @var{AA}.
36173 The second form of the response, including the process ID of the
36174 terminated process, can be used only when @value{GDBN} has reported
36175 support for multiprocess protocol extensions; see @ref{multiprocess
36176 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36179 @anchor{thread exit event}
36180 @cindex thread exit event, remote reply
36181 @item w @var{AA} ; @var{tid}
36183 The thread exited, and @var{AA} is the exit status. This response
36184 should not be sent by default; @value{GDBN} requests it with the
36185 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36186 @var{AA} is formatted as a big-endian hex string.
36189 There are no resumed threads left in the target. In other words, even
36190 though the process is alive, the last resumed thread has exited. For
36191 example, say the target process has two threads: thread 1 and thread
36192 2. The client leaves thread 1 stopped, and resumes thread 2, which
36193 subsequently exits. At this point, even though the process is still
36194 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36195 executing either. The @samp{N} stop reply thus informs the client
36196 that it can stop waiting for stop replies. This packet should not be
36197 sent by default; older @value{GDBN} versions did not support it.
36198 @value{GDBN} requests it, by supplying an appropriate
36199 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36200 also supply the appropriate @samp{qSupported} feature indicating
36203 @item O @var{XX}@dots{}
36204 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36205 written as the program's console output. This can happen at any time
36206 while the program is running and the debugger should continue to wait
36207 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36209 @item F @var{call-id},@var{parameter}@dots{}
36210 @var{call-id} is the identifier which says which host system call should
36211 be called. This is just the name of the function. Translation into the
36212 correct system call is only applicable as it's defined in @value{GDBN}.
36213 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36216 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36217 this very system call.
36219 The target replies with this packet when it expects @value{GDBN} to
36220 call a host system call on behalf of the target. @value{GDBN} replies
36221 with an appropriate @samp{F} packet and keeps up waiting for the next
36222 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36223 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36224 Protocol Extension}, for more details.
36228 @node General Query Packets
36229 @section General Query Packets
36230 @cindex remote query requests
36232 Packets starting with @samp{q} are @dfn{general query packets};
36233 packets starting with @samp{Q} are @dfn{general set packets}. General
36234 query and set packets are a semi-unified form for retrieving and
36235 sending information to and from the stub.
36237 The initial letter of a query or set packet is followed by a name
36238 indicating what sort of thing the packet applies to. For example,
36239 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36240 definitions with the stub. These packet names follow some
36245 The name must not contain commas, colons or semicolons.
36247 Most @value{GDBN} query and set packets have a leading upper case
36250 The names of custom vendor packets should use a company prefix, in
36251 lower case, followed by a period. For example, packets designed at
36252 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36253 foos) or @samp{Qacme.bar} (for setting bars).
36256 The name of a query or set packet should be separated from any
36257 parameters by a @samp{:}; the parameters themselves should be
36258 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36259 full packet name, and check for a separator or the end of the packet,
36260 in case two packet names share a common prefix. New packets should not begin
36261 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36262 packets predate these conventions, and have arguments without any terminator
36263 for the packet name; we suspect they are in widespread use in places that
36264 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36265 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36268 Like the descriptions of the other packets, each description here
36269 has a template showing the packet's overall syntax, followed by an
36270 explanation of the packet's meaning. We include spaces in some of the
36271 templates for clarity; these are not part of the packet's syntax. No
36272 @value{GDBN} packet uses spaces to separate its components.
36274 Here are the currently defined query and set packets:
36280 Turn on or off the agent as a helper to perform some debugging operations
36281 delegated from @value{GDBN} (@pxref{Control Agent}).
36283 @item QAllow:@var{op}:@var{val}@dots{}
36284 @cindex @samp{QAllow} packet
36285 Specify which operations @value{GDBN} expects to request of the
36286 target, as a semicolon-separated list of operation name and value
36287 pairs. Possible values for @var{op} include @samp{WriteReg},
36288 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36289 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36290 indicating that @value{GDBN} will not request the operation, or 1,
36291 indicating that it may. (The target can then use this to set up its
36292 own internals optimally, for instance if the debugger never expects to
36293 insert breakpoints, it may not need to install its own trap handler.)
36296 @cindex current thread, remote request
36297 @cindex @samp{qC} packet
36298 Return the current thread ID.
36302 @item QC @var{thread-id}
36303 Where @var{thread-id} is a thread ID as documented in
36304 @ref{thread-id syntax}.
36305 @item @r{(anything else)}
36306 Any other reply implies the old thread ID.
36309 @item qCRC:@var{addr},@var{length}
36310 @cindex CRC of memory block, remote request
36311 @cindex @samp{qCRC} packet
36312 @anchor{qCRC packet}
36313 Compute the CRC checksum of a block of memory using CRC-32 defined in
36314 IEEE 802.3. The CRC is computed byte at a time, taking the most
36315 significant bit of each byte first. The initial pattern code
36316 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36318 @emph{Note:} This is the same CRC used in validating separate debug
36319 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36320 Files}). However the algorithm is slightly different. When validating
36321 separate debug files, the CRC is computed taking the @emph{least}
36322 significant bit of each byte first, and the final result is inverted to
36323 detect trailing zeros.
36328 An error (such as memory fault)
36329 @item C @var{crc32}
36330 The specified memory region's checksum is @var{crc32}.
36333 @item QDisableRandomization:@var{value}
36334 @cindex disable address space randomization, remote request
36335 @cindex @samp{QDisableRandomization} packet
36336 Some target operating systems will randomize the virtual address space
36337 of the inferior process as a security feature, but provide a feature
36338 to disable such randomization, e.g.@: to allow for a more deterministic
36339 debugging experience. On such systems, this packet with a @var{value}
36340 of 1 directs the target to disable address space randomization for
36341 processes subsequently started via @samp{vRun} packets, while a packet
36342 with a @var{value} of 0 tells the target to enable address space
36345 This packet is only available in extended mode (@pxref{extended mode}).
36350 The request succeeded.
36353 An error occurred. The error number @var{nn} is given as hex digits.
36356 An empty reply indicates that @samp{QDisableRandomization} is not supported
36360 This packet is not probed by default; the remote stub must request it,
36361 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36362 This should only be done on targets that actually support disabling
36363 address space randomization.
36366 @itemx qsThreadInfo
36367 @cindex list active threads, remote request
36368 @cindex @samp{qfThreadInfo} packet
36369 @cindex @samp{qsThreadInfo} packet
36370 Obtain a list of all active thread IDs from the target (OS). Since there
36371 may be too many active threads to fit into one reply packet, this query
36372 works iteratively: it may require more than one query/reply sequence to
36373 obtain the entire list of threads. The first query of the sequence will
36374 be the @samp{qfThreadInfo} query; subsequent queries in the
36375 sequence will be the @samp{qsThreadInfo} query.
36377 NOTE: This packet replaces the @samp{qL} query (see below).
36381 @item m @var{thread-id}
36383 @item m @var{thread-id},@var{thread-id}@dots{}
36384 a comma-separated list of thread IDs
36386 (lower case letter @samp{L}) denotes end of list.
36389 In response to each query, the target will reply with a list of one or
36390 more thread IDs, separated by commas.
36391 @value{GDBN} will respond to each reply with a request for more thread
36392 ids (using the @samp{qs} form of the query), until the target responds
36393 with @samp{l} (lower-case ell, for @dfn{last}).
36394 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36397 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36398 initial connection with the remote target, and the very first thread ID
36399 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36400 message. Therefore, the stub should ensure that the first thread ID in
36401 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36403 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36404 @cindex get thread-local storage address, remote request
36405 @cindex @samp{qGetTLSAddr} packet
36406 Fetch the address associated with thread local storage specified
36407 by @var{thread-id}, @var{offset}, and @var{lm}.
36409 @var{thread-id} is the thread ID associated with the
36410 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36412 @var{offset} is the (big endian, hex encoded) offset associated with the
36413 thread local variable. (This offset is obtained from the debug
36414 information associated with the variable.)
36416 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36417 load module associated with the thread local storage. For example,
36418 a @sc{gnu}/Linux system will pass the link map address of the shared
36419 object associated with the thread local storage under consideration.
36420 Other operating environments may choose to represent the load module
36421 differently, so the precise meaning of this parameter will vary.
36425 @item @var{XX}@dots{}
36426 Hex encoded (big endian) bytes representing the address of the thread
36427 local storage requested.
36430 An error occurred. The error number @var{nn} is given as hex digits.
36433 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36436 @item qGetTIBAddr:@var{thread-id}
36437 @cindex get thread information block address
36438 @cindex @samp{qGetTIBAddr} packet
36439 Fetch address of the Windows OS specific Thread Information Block.
36441 @var{thread-id} is the thread ID associated with the thread.
36445 @item @var{XX}@dots{}
36446 Hex encoded (big endian) bytes representing the linear address of the
36447 thread information block.
36450 An error occured. This means that either the thread was not found, or the
36451 address could not be retrieved.
36454 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36457 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36458 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36459 digit) is one to indicate the first query and zero to indicate a
36460 subsequent query; @var{threadcount} (two hex digits) is the maximum
36461 number of threads the response packet can contain; and @var{nextthread}
36462 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36463 returned in the response as @var{argthread}.
36465 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36469 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36470 Where: @var{count} (two hex digits) is the number of threads being
36471 returned; @var{done} (one hex digit) is zero to indicate more threads
36472 and one indicates no further threads; @var{argthreadid} (eight hex
36473 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36474 is a sequence of thread IDs, @var{threadid} (eight hex
36475 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36479 @cindex section offsets, remote request
36480 @cindex @samp{qOffsets} packet
36481 Get section offsets that the target used when relocating the downloaded
36486 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36487 Relocate the @code{Text} section by @var{xxx} from its original address.
36488 Relocate the @code{Data} section by @var{yyy} from its original address.
36489 If the object file format provides segment information (e.g.@: @sc{elf}
36490 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36491 segments by the supplied offsets.
36493 @emph{Note: while a @code{Bss} offset may be included in the response,
36494 @value{GDBN} ignores this and instead applies the @code{Data} offset
36495 to the @code{Bss} section.}
36497 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36498 Relocate the first segment of the object file, which conventionally
36499 contains program code, to a starting address of @var{xxx}. If
36500 @samp{DataSeg} is specified, relocate the second segment, which
36501 conventionally contains modifiable data, to a starting address of
36502 @var{yyy}. @value{GDBN} will report an error if the object file
36503 does not contain segment information, or does not contain at least
36504 as many segments as mentioned in the reply. Extra segments are
36505 kept at fixed offsets relative to the last relocated segment.
36508 @item qP @var{mode} @var{thread-id}
36509 @cindex thread information, remote request
36510 @cindex @samp{qP} packet
36511 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36512 encoded 32 bit mode; @var{thread-id} is a thread ID
36513 (@pxref{thread-id syntax}).
36515 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36518 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36522 @cindex non-stop mode, remote request
36523 @cindex @samp{QNonStop} packet
36525 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36526 @xref{Remote Non-Stop}, for more information.
36531 The request succeeded.
36534 An error occurred. The error number @var{nn} is given as hex digits.
36537 An empty reply indicates that @samp{QNonStop} is not supported by
36541 This packet is not probed by default; the remote stub must request it,
36542 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36543 Use of this packet is controlled by the @code{set non-stop} command;
36544 @pxref{Non-Stop Mode}.
36546 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36547 @itemx QCatchSyscalls:0
36548 @cindex catch syscalls from inferior, remote request
36549 @cindex @samp{QCatchSyscalls} packet
36550 @anchor{QCatchSyscalls}
36551 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36552 catching syscalls from the inferior process.
36554 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36555 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36556 is listed, every system call should be reported.
36558 Note that if a syscall not in the list is reported, @value{GDBN} will
36559 still filter the event according to its own list from all corresponding
36560 @code{catch syscall} commands. However, it is more efficient to only
36561 report the requested syscalls.
36563 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36564 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36566 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36567 kept for the new process too. On targets where exec may affect syscall
36568 numbers, for example with exec between 32 and 64-bit processes, the
36569 client should send a new packet with the new syscall list.
36574 The request succeeded.
36577 An error occurred. @var{nn} are hex digits.
36580 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36584 Use of this packet is controlled by the @code{set remote catch-syscalls}
36585 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36586 This packet is not probed by default; the remote stub must request it,
36587 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36589 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36590 @cindex pass signals to inferior, remote request
36591 @cindex @samp{QPassSignals} packet
36592 @anchor{QPassSignals}
36593 Each listed @var{signal} should be passed directly to the inferior process.
36594 Signals are numbered identically to continue packets and stop replies
36595 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36596 strictly greater than the previous item. These signals do not need to stop
36597 the inferior, or be reported to @value{GDBN}. All other signals should be
36598 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36599 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36600 new list. This packet improves performance when using @samp{handle
36601 @var{signal} nostop noprint pass}.
36606 The request succeeded.
36609 An error occurred. The error number @var{nn} is given as hex digits.
36612 An empty reply indicates that @samp{QPassSignals} is not supported by
36616 Use of this packet is controlled by the @code{set remote pass-signals}
36617 command (@pxref{Remote Configuration, set remote pass-signals}).
36618 This packet is not probed by default; the remote stub must request it,
36619 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36621 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36622 @cindex signals the inferior may see, remote request
36623 @cindex @samp{QProgramSignals} packet
36624 @anchor{QProgramSignals}
36625 Each listed @var{signal} may be delivered to the inferior process.
36626 Others should be silently discarded.
36628 In some cases, the remote stub may need to decide whether to deliver a
36629 signal to the program or not without @value{GDBN} involvement. One
36630 example of that is while detaching --- the program's threads may have
36631 stopped for signals that haven't yet had a chance of being reported to
36632 @value{GDBN}, and so the remote stub can use the signal list specified
36633 by this packet to know whether to deliver or ignore those pending
36636 This does not influence whether to deliver a signal as requested by a
36637 resumption packet (@pxref{vCont packet}).
36639 Signals are numbered identically to continue packets and stop replies
36640 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36641 strictly greater than the previous item. Multiple
36642 @samp{QProgramSignals} packets do not combine; any earlier
36643 @samp{QProgramSignals} list is completely replaced by the new list.
36648 The request succeeded.
36651 An error occurred. The error number @var{nn} is given as hex digits.
36654 An empty reply indicates that @samp{QProgramSignals} is not supported
36658 Use of this packet is controlled by the @code{set remote program-signals}
36659 command (@pxref{Remote Configuration, set remote program-signals}).
36660 This packet is not probed by default; the remote stub must request it,
36661 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36663 @anchor{QThreadEvents}
36664 @item QThreadEvents:1
36665 @itemx QThreadEvents:0
36666 @cindex thread create/exit events, remote request
36667 @cindex @samp{QThreadEvents} packet
36669 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36670 reporting of thread create and exit events. @xref{thread create
36671 event}, for the reply specifications. For example, this is used in
36672 non-stop mode when @value{GDBN} stops a set of threads and
36673 synchronously waits for the their corresponding stop replies. Without
36674 exit events, if one of the threads exits, @value{GDBN} would hang
36675 forever not knowing that it should no longer expect a stop for that
36676 same thread. @value{GDBN} does not enable this feature unless the
36677 stub reports that it supports it by including @samp{QThreadEvents+} in
36678 its @samp{qSupported} reply.
36683 The request succeeded.
36686 An error occurred. The error number @var{nn} is given as hex digits.
36689 An empty reply indicates that @samp{QThreadEvents} is not supported by
36693 Use of this packet is controlled by the @code{set remote thread-events}
36694 command (@pxref{Remote Configuration, set remote thread-events}).
36696 @item qRcmd,@var{command}
36697 @cindex execute remote command, remote request
36698 @cindex @samp{qRcmd} packet
36699 @var{command} (hex encoded) is passed to the local interpreter for
36700 execution. Invalid commands should be reported using the output
36701 string. Before the final result packet, the target may also respond
36702 with a number of intermediate @samp{O@var{output}} console output
36703 packets. @emph{Implementors should note that providing access to a
36704 stubs's interpreter may have security implications}.
36709 A command response with no output.
36711 A command response with the hex encoded output string @var{OUTPUT}.
36713 Indicate a badly formed request.
36715 An empty reply indicates that @samp{qRcmd} is not recognized.
36718 (Note that the @code{qRcmd} packet's name is separated from the
36719 command by a @samp{,}, not a @samp{:}, contrary to the naming
36720 conventions above. Please don't use this packet as a model for new
36723 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36724 @cindex searching memory, in remote debugging
36726 @cindex @samp{qSearch:memory} packet
36728 @cindex @samp{qSearch memory} packet
36729 @anchor{qSearch memory}
36730 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36731 Both @var{address} and @var{length} are encoded in hex;
36732 @var{search-pattern} is a sequence of bytes, also hex encoded.
36737 The pattern was not found.
36739 The pattern was found at @var{address}.
36741 A badly formed request or an error was encountered while searching memory.
36743 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36746 @item QStartNoAckMode
36747 @cindex @samp{QStartNoAckMode} packet
36748 @anchor{QStartNoAckMode}
36749 Request that the remote stub disable the normal @samp{+}/@samp{-}
36750 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36755 The stub has switched to no-acknowledgment mode.
36756 @value{GDBN} acknowledges this reponse,
36757 but neither the stub nor @value{GDBN} shall send or expect further
36758 @samp{+}/@samp{-} acknowledgments in the current connection.
36760 An empty reply indicates that the stub does not support no-acknowledgment mode.
36763 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36764 @cindex supported packets, remote query
36765 @cindex features of the remote protocol
36766 @cindex @samp{qSupported} packet
36767 @anchor{qSupported}
36768 Tell the remote stub about features supported by @value{GDBN}, and
36769 query the stub for features it supports. This packet allows
36770 @value{GDBN} and the remote stub to take advantage of each others'
36771 features. @samp{qSupported} also consolidates multiple feature probes
36772 at startup, to improve @value{GDBN} performance---a single larger
36773 packet performs better than multiple smaller probe packets on
36774 high-latency links. Some features may enable behavior which must not
36775 be on by default, e.g.@: because it would confuse older clients or
36776 stubs. Other features may describe packets which could be
36777 automatically probed for, but are not. These features must be
36778 reported before @value{GDBN} will use them. This ``default
36779 unsupported'' behavior is not appropriate for all packets, but it
36780 helps to keep the initial connection time under control with new
36781 versions of @value{GDBN} which support increasing numbers of packets.
36785 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36786 The stub supports or does not support each returned @var{stubfeature},
36787 depending on the form of each @var{stubfeature} (see below for the
36790 An empty reply indicates that @samp{qSupported} is not recognized,
36791 or that no features needed to be reported to @value{GDBN}.
36794 The allowed forms for each feature (either a @var{gdbfeature} in the
36795 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36799 @item @var{name}=@var{value}
36800 The remote protocol feature @var{name} is supported, and associated
36801 with the specified @var{value}. The format of @var{value} depends
36802 on the feature, but it must not include a semicolon.
36804 The remote protocol feature @var{name} is supported, and does not
36805 need an associated value.
36807 The remote protocol feature @var{name} is not supported.
36809 The remote protocol feature @var{name} may be supported, and
36810 @value{GDBN} should auto-detect support in some other way when it is
36811 needed. This form will not be used for @var{gdbfeature} notifications,
36812 but may be used for @var{stubfeature} responses.
36815 Whenever the stub receives a @samp{qSupported} request, the
36816 supplied set of @value{GDBN} features should override any previous
36817 request. This allows @value{GDBN} to put the stub in a known
36818 state, even if the stub had previously been communicating with
36819 a different version of @value{GDBN}.
36821 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36826 This feature indicates whether @value{GDBN} supports multiprocess
36827 extensions to the remote protocol. @value{GDBN} does not use such
36828 extensions unless the stub also reports that it supports them by
36829 including @samp{multiprocess+} in its @samp{qSupported} reply.
36830 @xref{multiprocess extensions}, for details.
36833 This feature indicates that @value{GDBN} supports the XML target
36834 description. If the stub sees @samp{xmlRegisters=} with target
36835 specific strings separated by a comma, it will report register
36839 This feature indicates whether @value{GDBN} supports the
36840 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36841 instruction reply packet}).
36844 This feature indicates whether @value{GDBN} supports the swbreak stop
36845 reason in stop replies. @xref{swbreak stop reason}, for details.
36848 This feature indicates whether @value{GDBN} supports the hwbreak stop
36849 reason in stop replies. @xref{swbreak stop reason}, for details.
36852 This feature indicates whether @value{GDBN} supports fork event
36853 extensions to the remote protocol. @value{GDBN} does not use such
36854 extensions unless the stub also reports that it supports them by
36855 including @samp{fork-events+} in its @samp{qSupported} reply.
36858 This feature indicates whether @value{GDBN} supports vfork event
36859 extensions to the remote protocol. @value{GDBN} does not use such
36860 extensions unless the stub also reports that it supports them by
36861 including @samp{vfork-events+} in its @samp{qSupported} reply.
36864 This feature indicates whether @value{GDBN} supports exec event
36865 extensions to the remote protocol. @value{GDBN} does not use such
36866 extensions unless the stub also reports that it supports them by
36867 including @samp{exec-events+} in its @samp{qSupported} reply.
36869 @item vContSupported
36870 This feature indicates whether @value{GDBN} wants to know the
36871 supported actions in the reply to @samp{vCont?} packet.
36874 Stubs should ignore any unknown values for
36875 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36876 packet supports receiving packets of unlimited length (earlier
36877 versions of @value{GDBN} may reject overly long responses). Additional values
36878 for @var{gdbfeature} may be defined in the future to let the stub take
36879 advantage of new features in @value{GDBN}, e.g.@: incompatible
36880 improvements in the remote protocol---the @samp{multiprocess} feature is
36881 an example of such a feature. The stub's reply should be independent
36882 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36883 describes all the features it supports, and then the stub replies with
36884 all the features it supports.
36886 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36887 responses, as long as each response uses one of the standard forms.
36889 Some features are flags. A stub which supports a flag feature
36890 should respond with a @samp{+} form response. Other features
36891 require values, and the stub should respond with an @samp{=}
36894 Each feature has a default value, which @value{GDBN} will use if
36895 @samp{qSupported} is not available or if the feature is not mentioned
36896 in the @samp{qSupported} response. The default values are fixed; a
36897 stub is free to omit any feature responses that match the defaults.
36899 Not all features can be probed, but for those which can, the probing
36900 mechanism is useful: in some cases, a stub's internal
36901 architecture may not allow the protocol layer to know some information
36902 about the underlying target in advance. This is especially common in
36903 stubs which may be configured for multiple targets.
36905 These are the currently defined stub features and their properties:
36907 @multitable @columnfractions 0.35 0.2 0.12 0.2
36908 @c NOTE: The first row should be @headitem, but we do not yet require
36909 @c a new enough version of Texinfo (4.7) to use @headitem.
36911 @tab Value Required
36915 @item @samp{PacketSize}
36920 @item @samp{qXfer:auxv:read}
36925 @item @samp{qXfer:btrace:read}
36930 @item @samp{qXfer:btrace-conf:read}
36935 @item @samp{qXfer:exec-file:read}
36940 @item @samp{qXfer:features:read}
36945 @item @samp{qXfer:libraries:read}
36950 @item @samp{qXfer:libraries-svr4:read}
36955 @item @samp{augmented-libraries-svr4-read}
36960 @item @samp{qXfer:memory-map:read}
36965 @item @samp{qXfer:sdata:read}
36970 @item @samp{qXfer:spu:read}
36975 @item @samp{qXfer:spu:write}
36980 @item @samp{qXfer:siginfo:read}
36985 @item @samp{qXfer:siginfo:write}
36990 @item @samp{qXfer:threads:read}
36995 @item @samp{qXfer:traceframe-info:read}
37000 @item @samp{qXfer:uib:read}
37005 @item @samp{qXfer:fdpic:read}
37010 @item @samp{Qbtrace:off}
37015 @item @samp{Qbtrace:bts}
37020 @item @samp{Qbtrace:pt}
37025 @item @samp{Qbtrace-conf:bts:size}
37030 @item @samp{Qbtrace-conf:pt:size}
37035 @item @samp{QNonStop}
37040 @item @samp{QCatchSyscalls}
37045 @item @samp{QPassSignals}
37050 @item @samp{QStartNoAckMode}
37055 @item @samp{multiprocess}
37060 @item @samp{ConditionalBreakpoints}
37065 @item @samp{ConditionalTracepoints}
37070 @item @samp{ReverseContinue}
37075 @item @samp{ReverseStep}
37080 @item @samp{TracepointSource}
37085 @item @samp{QAgent}
37090 @item @samp{QAllow}
37095 @item @samp{QDisableRandomization}
37100 @item @samp{EnableDisableTracepoints}
37105 @item @samp{QTBuffer:size}
37110 @item @samp{tracenz}
37115 @item @samp{BreakpointCommands}
37120 @item @samp{swbreak}
37125 @item @samp{hwbreak}
37130 @item @samp{fork-events}
37135 @item @samp{vfork-events}
37140 @item @samp{exec-events}
37145 @item @samp{QThreadEvents}
37150 @item @samp{no-resumed}
37157 These are the currently defined stub features, in more detail:
37160 @cindex packet size, remote protocol
37161 @item PacketSize=@var{bytes}
37162 The remote stub can accept packets up to at least @var{bytes} in
37163 length. @value{GDBN} will send packets up to this size for bulk
37164 transfers, and will never send larger packets. This is a limit on the
37165 data characters in the packet, including the frame and checksum.
37166 There is no trailing NUL byte in a remote protocol packet; if the stub
37167 stores packets in a NUL-terminated format, it should allow an extra
37168 byte in its buffer for the NUL. If this stub feature is not supported,
37169 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37171 @item qXfer:auxv:read
37172 The remote stub understands the @samp{qXfer:auxv:read} packet
37173 (@pxref{qXfer auxiliary vector read}).
37175 @item qXfer:btrace:read
37176 The remote stub understands the @samp{qXfer:btrace:read}
37177 packet (@pxref{qXfer btrace read}).
37179 @item qXfer:btrace-conf:read
37180 The remote stub understands the @samp{qXfer:btrace-conf:read}
37181 packet (@pxref{qXfer btrace-conf read}).
37183 @item qXfer:exec-file:read
37184 The remote stub understands the @samp{qXfer:exec-file:read} packet
37185 (@pxref{qXfer executable filename read}).
37187 @item qXfer:features:read
37188 The remote stub understands the @samp{qXfer:features:read} packet
37189 (@pxref{qXfer target description read}).
37191 @item qXfer:libraries:read
37192 The remote stub understands the @samp{qXfer:libraries:read} packet
37193 (@pxref{qXfer library list read}).
37195 @item qXfer:libraries-svr4:read
37196 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37197 (@pxref{qXfer svr4 library list read}).
37199 @item augmented-libraries-svr4-read
37200 The remote stub understands the augmented form of the
37201 @samp{qXfer:libraries-svr4:read} packet
37202 (@pxref{qXfer svr4 library list read}).
37204 @item qXfer:memory-map:read
37205 The remote stub understands the @samp{qXfer:memory-map:read} packet
37206 (@pxref{qXfer memory map read}).
37208 @item qXfer:sdata:read
37209 The remote stub understands the @samp{qXfer:sdata:read} packet
37210 (@pxref{qXfer sdata read}).
37212 @item qXfer:spu:read
37213 The remote stub understands the @samp{qXfer:spu:read} packet
37214 (@pxref{qXfer spu read}).
37216 @item qXfer:spu:write
37217 The remote stub understands the @samp{qXfer:spu:write} packet
37218 (@pxref{qXfer spu write}).
37220 @item qXfer:siginfo:read
37221 The remote stub understands the @samp{qXfer:siginfo:read} packet
37222 (@pxref{qXfer siginfo read}).
37224 @item qXfer:siginfo:write
37225 The remote stub understands the @samp{qXfer:siginfo:write} packet
37226 (@pxref{qXfer siginfo write}).
37228 @item qXfer:threads:read
37229 The remote stub understands the @samp{qXfer:threads:read} packet
37230 (@pxref{qXfer threads read}).
37232 @item qXfer:traceframe-info:read
37233 The remote stub understands the @samp{qXfer:traceframe-info:read}
37234 packet (@pxref{qXfer traceframe info read}).
37236 @item qXfer:uib:read
37237 The remote stub understands the @samp{qXfer:uib:read}
37238 packet (@pxref{qXfer unwind info block}).
37240 @item qXfer:fdpic:read
37241 The remote stub understands the @samp{qXfer:fdpic:read}
37242 packet (@pxref{qXfer fdpic loadmap read}).
37245 The remote stub understands the @samp{QNonStop} packet
37246 (@pxref{QNonStop}).
37248 @item QCatchSyscalls
37249 The remote stub understands the @samp{QCatchSyscalls} packet
37250 (@pxref{QCatchSyscalls}).
37253 The remote stub understands the @samp{QPassSignals} packet
37254 (@pxref{QPassSignals}).
37256 @item QStartNoAckMode
37257 The remote stub understands the @samp{QStartNoAckMode} packet and
37258 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37261 @anchor{multiprocess extensions}
37262 @cindex multiprocess extensions, in remote protocol
37263 The remote stub understands the multiprocess extensions to the remote
37264 protocol syntax. The multiprocess extensions affect the syntax of
37265 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37266 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37267 replies. Note that reporting this feature indicates support for the
37268 syntactic extensions only, not that the stub necessarily supports
37269 debugging of more than one process at a time. The stub must not use
37270 multiprocess extensions in packet replies unless @value{GDBN} has also
37271 indicated it supports them in its @samp{qSupported} request.
37273 @item qXfer:osdata:read
37274 The remote stub understands the @samp{qXfer:osdata:read} packet
37275 ((@pxref{qXfer osdata read}).
37277 @item ConditionalBreakpoints
37278 The target accepts and implements evaluation of conditional expressions
37279 defined for breakpoints. The target will only report breakpoint triggers
37280 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37282 @item ConditionalTracepoints
37283 The remote stub accepts and implements conditional expressions defined
37284 for tracepoints (@pxref{Tracepoint Conditions}).
37286 @item ReverseContinue
37287 The remote stub accepts and implements the reverse continue packet
37291 The remote stub accepts and implements the reverse step packet
37294 @item TracepointSource
37295 The remote stub understands the @samp{QTDPsrc} packet that supplies
37296 the source form of tracepoint definitions.
37299 The remote stub understands the @samp{QAgent} packet.
37302 The remote stub understands the @samp{QAllow} packet.
37304 @item QDisableRandomization
37305 The remote stub understands the @samp{QDisableRandomization} packet.
37307 @item StaticTracepoint
37308 @cindex static tracepoints, in remote protocol
37309 The remote stub supports static tracepoints.
37311 @item InstallInTrace
37312 @anchor{install tracepoint in tracing}
37313 The remote stub supports installing tracepoint in tracing.
37315 @item EnableDisableTracepoints
37316 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37317 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37318 to be enabled and disabled while a trace experiment is running.
37320 @item QTBuffer:size
37321 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37322 packet that allows to change the size of the trace buffer.
37325 @cindex string tracing, in remote protocol
37326 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37327 See @ref{Bytecode Descriptions} for details about the bytecode.
37329 @item BreakpointCommands
37330 @cindex breakpoint commands, in remote protocol
37331 The remote stub supports running a breakpoint's command list itself,
37332 rather than reporting the hit to @value{GDBN}.
37335 The remote stub understands the @samp{Qbtrace:off} packet.
37338 The remote stub understands the @samp{Qbtrace:bts} packet.
37341 The remote stub understands the @samp{Qbtrace:pt} packet.
37343 @item Qbtrace-conf:bts:size
37344 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37346 @item Qbtrace-conf:pt:size
37347 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37350 The remote stub reports the @samp{swbreak} stop reason for memory
37354 The remote stub reports the @samp{hwbreak} stop reason for hardware
37358 The remote stub reports the @samp{fork} stop reason for fork events.
37361 The remote stub reports the @samp{vfork} stop reason for vfork events
37362 and vforkdone events.
37365 The remote stub reports the @samp{exec} stop reason for exec events.
37367 @item vContSupported
37368 The remote stub reports the supported actions in the reply to
37369 @samp{vCont?} packet.
37371 @item QThreadEvents
37372 The remote stub understands the @samp{QThreadEvents} packet.
37375 The remote stub reports the @samp{N} stop reply.
37380 @cindex symbol lookup, remote request
37381 @cindex @samp{qSymbol} packet
37382 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37383 requests. Accept requests from the target for the values of symbols.
37388 The target does not need to look up any (more) symbols.
37389 @item qSymbol:@var{sym_name}
37390 The target requests the value of symbol @var{sym_name} (hex encoded).
37391 @value{GDBN} may provide the value by using the
37392 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37396 @item qSymbol:@var{sym_value}:@var{sym_name}
37397 Set the value of @var{sym_name} to @var{sym_value}.
37399 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37400 target has previously requested.
37402 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37403 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37409 The target does not need to look up any (more) symbols.
37410 @item qSymbol:@var{sym_name}
37411 The target requests the value of a new symbol @var{sym_name} (hex
37412 encoded). @value{GDBN} will continue to supply the values of symbols
37413 (if available), until the target ceases to request them.
37418 @itemx QTDisconnected
37425 @itemx qTMinFTPILen
37427 @xref{Tracepoint Packets}.
37429 @item qThreadExtraInfo,@var{thread-id}
37430 @cindex thread attributes info, remote request
37431 @cindex @samp{qThreadExtraInfo} packet
37432 Obtain from the target OS a printable string description of thread
37433 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37434 for the forms of @var{thread-id}. This
37435 string may contain anything that the target OS thinks is interesting
37436 for @value{GDBN} to tell the user about the thread. The string is
37437 displayed in @value{GDBN}'s @code{info threads} display. Some
37438 examples of possible thread extra info strings are @samp{Runnable}, or
37439 @samp{Blocked on Mutex}.
37443 @item @var{XX}@dots{}
37444 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37445 comprising the printable string containing the extra information about
37446 the thread's attributes.
37449 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37450 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37451 conventions above. Please don't use this packet as a model for new
37470 @xref{Tracepoint Packets}.
37472 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37473 @cindex read special object, remote request
37474 @cindex @samp{qXfer} packet
37475 @anchor{qXfer read}
37476 Read uninterpreted bytes from the target's special data area
37477 identified by the keyword @var{object}. Request @var{length} bytes
37478 starting at @var{offset} bytes into the data. The content and
37479 encoding of @var{annex} is specific to @var{object}; it can supply
37480 additional details about what data to access.
37485 Data @var{data} (@pxref{Binary Data}) has been read from the
37486 target. There may be more data at a higher address (although
37487 it is permitted to return @samp{m} even for the last valid
37488 block of data, as long as at least one byte of data was read).
37489 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37493 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37494 There is no more data to be read. It is possible for @var{data} to
37495 have fewer bytes than the @var{length} in the request.
37498 The @var{offset} in the request is at the end of the data.
37499 There is no more data to be read.
37502 The request was malformed, or @var{annex} was invalid.
37505 The offset was invalid, or there was an error encountered reading the data.
37506 The @var{nn} part is a hex-encoded @code{errno} value.
37509 An empty reply indicates the @var{object} string was not recognized by
37510 the stub, or that the object does not support reading.
37513 Here are the specific requests of this form defined so far. All the
37514 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37515 formats, listed above.
37518 @item qXfer:auxv:read::@var{offset},@var{length}
37519 @anchor{qXfer auxiliary vector read}
37520 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37521 auxiliary vector}. Note @var{annex} must be empty.
37523 This packet is not probed by default; the remote stub must request it,
37524 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37526 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37527 @anchor{qXfer btrace read}
37529 Return a description of the current branch trace.
37530 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37531 packet may have one of the following values:
37535 Returns all available branch trace.
37538 Returns all available branch trace if the branch trace changed since
37539 the last read request.
37542 Returns the new branch trace since the last read request. Adds a new
37543 block to the end of the trace that begins at zero and ends at the source
37544 location of the first branch in the trace buffer. This extra block is
37545 used to stitch traces together.
37547 If the trace buffer overflowed, returns an error indicating the overflow.
37550 This packet is not probed by default; the remote stub must request it
37551 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37553 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37554 @anchor{qXfer btrace-conf read}
37556 Return a description of the current branch trace configuration.
37557 @xref{Branch Trace Configuration Format}.
37559 This packet is not probed by default; the remote stub must request it
37560 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37562 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37563 @anchor{qXfer executable filename read}
37564 Return the full absolute name of the file that was executed to create
37565 a process running on the remote system. The annex specifies the
37566 numeric process ID of the process to query, encoded as a hexadecimal
37567 number. If the annex part is empty the remote stub should return the
37568 filename corresponding to the currently executing process.
37570 This packet is not probed by default; the remote stub must request it,
37571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37573 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37574 @anchor{qXfer target description read}
37575 Access the @dfn{target description}. @xref{Target Descriptions}. The
37576 annex specifies which XML document to access. The main description is
37577 always loaded from the @samp{target.xml} annex.
37579 This packet is not probed by default; the remote stub must request it,
37580 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37582 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37583 @anchor{qXfer library list read}
37584 Access the target's list of loaded libraries. @xref{Library List Format}.
37585 The annex part of the generic @samp{qXfer} packet must be empty
37586 (@pxref{qXfer read}).
37588 Targets which maintain a list of libraries in the program's memory do
37589 not need to implement this packet; it is designed for platforms where
37590 the operating system manages the list of loaded libraries.
37592 This packet is not probed by default; the remote stub must request it,
37593 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37595 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37596 @anchor{qXfer svr4 library list read}
37597 Access the target's list of loaded libraries when the target is an SVR4
37598 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37599 of the generic @samp{qXfer} packet must be empty unless the remote
37600 stub indicated it supports the augmented form of this packet
37601 by supplying an appropriate @samp{qSupported} response
37602 (@pxref{qXfer read}, @ref{qSupported}).
37604 This packet is optional for better performance on SVR4 targets.
37605 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37607 This packet is not probed by default; the remote stub must request it,
37608 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37610 If the remote stub indicates it supports the augmented form of this
37611 packet then the annex part of the generic @samp{qXfer} packet may
37612 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37613 arguments. The currently supported arguments are:
37616 @item start=@var{address}
37617 A hexadecimal number specifying the address of the @samp{struct
37618 link_map} to start reading the library list from. If unset or zero
37619 then the first @samp{struct link_map} in the library list will be
37620 chosen as the starting point.
37622 @item prev=@var{address}
37623 A hexadecimal number specifying the address of the @samp{struct
37624 link_map} immediately preceding the @samp{struct link_map}
37625 specified by the @samp{start} argument. If unset or zero then
37626 the remote stub will expect that no @samp{struct link_map}
37627 exists prior to the starting point.
37631 Arguments that are not understood by the remote stub will be silently
37634 @item qXfer:memory-map:read::@var{offset},@var{length}
37635 @anchor{qXfer memory map read}
37636 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37637 annex part of the generic @samp{qXfer} packet must be empty
37638 (@pxref{qXfer read}).
37640 This packet is not probed by default; the remote stub must request it,
37641 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37643 @item qXfer:sdata:read::@var{offset},@var{length}
37644 @anchor{qXfer sdata read}
37646 Read contents of the extra collected static tracepoint marker
37647 information. The annex part of the generic @samp{qXfer} packet must
37648 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37651 This packet is not probed by default; the remote stub must request it,
37652 by supplying an appropriate @samp{qSupported} response
37653 (@pxref{qSupported}).
37655 @item qXfer:siginfo:read::@var{offset},@var{length}
37656 @anchor{qXfer siginfo read}
37657 Read contents of the extra signal information on the target
37658 system. The annex part of the generic @samp{qXfer} packet must be
37659 empty (@pxref{qXfer read}).
37661 This packet is not probed by default; the remote stub must request it,
37662 by supplying an appropriate @samp{qSupported} response
37663 (@pxref{qSupported}).
37665 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37666 @anchor{qXfer spu read}
37667 Read contents of an @code{spufs} file on the target system. The
37668 annex specifies which file to read; it must be of the form
37669 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37670 in the target process, and @var{name} identifes the @code{spufs} file
37671 in that context to be accessed.
37673 This packet is not probed by default; the remote stub must request it,
37674 by supplying an appropriate @samp{qSupported} response
37675 (@pxref{qSupported}).
37677 @item qXfer:threads:read::@var{offset},@var{length}
37678 @anchor{qXfer threads read}
37679 Access the list of threads on target. @xref{Thread List Format}. The
37680 annex part of the generic @samp{qXfer} packet must be empty
37681 (@pxref{qXfer read}).
37683 This packet is not probed by default; the remote stub must request it,
37684 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37686 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37687 @anchor{qXfer traceframe info read}
37689 Return a description of the current traceframe's contents.
37690 @xref{Traceframe Info Format}. The annex part of the generic
37691 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37693 This packet is not probed by default; the remote stub must request it,
37694 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37696 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37697 @anchor{qXfer unwind info block}
37699 Return the unwind information block for @var{pc}. This packet is used
37700 on OpenVMS/ia64 to ask the kernel unwind information.
37702 This packet is not probed by default.
37704 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37705 @anchor{qXfer fdpic loadmap read}
37706 Read contents of @code{loadmap}s on the target system. The
37707 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37708 executable @code{loadmap} or interpreter @code{loadmap} to read.
37710 This packet is not probed by default; the remote stub must request it,
37711 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37713 @item qXfer:osdata:read::@var{offset},@var{length}
37714 @anchor{qXfer osdata read}
37715 Access the target's @dfn{operating system information}.
37716 @xref{Operating System Information}.
37720 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37721 @cindex write data into object, remote request
37722 @anchor{qXfer write}
37723 Write uninterpreted bytes into the target's special data area
37724 identified by the keyword @var{object}, starting at @var{offset} bytes
37725 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37726 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37727 is specific to @var{object}; it can supply additional details about what data
37733 @var{nn} (hex encoded) is the number of bytes written.
37734 This may be fewer bytes than supplied in the request.
37737 The request was malformed, or @var{annex} was invalid.
37740 The offset was invalid, or there was an error encountered writing the data.
37741 The @var{nn} part is a hex-encoded @code{errno} value.
37744 An empty reply indicates the @var{object} string was not
37745 recognized by the stub, or that the object does not support writing.
37748 Here are the specific requests of this form defined so far. All the
37749 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37750 formats, listed above.
37753 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37754 @anchor{qXfer siginfo write}
37755 Write @var{data} to the extra signal information on the target system.
37756 The annex part of the generic @samp{qXfer} packet must be
37757 empty (@pxref{qXfer write}).
37759 This packet is not probed by default; the remote stub must request it,
37760 by supplying an appropriate @samp{qSupported} response
37761 (@pxref{qSupported}).
37763 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37764 @anchor{qXfer spu write}
37765 Write @var{data} to an @code{spufs} file on the target system. The
37766 annex specifies which file to write; it must be of the form
37767 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37768 in the target process, and @var{name} identifes the @code{spufs} file
37769 in that context to be accessed.
37771 This packet is not probed by default; the remote stub must request it,
37772 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37775 @item qXfer:@var{object}:@var{operation}:@dots{}
37776 Requests of this form may be added in the future. When a stub does
37777 not recognize the @var{object} keyword, or its support for
37778 @var{object} does not recognize the @var{operation} keyword, the stub
37779 must respond with an empty packet.
37781 @item qAttached:@var{pid}
37782 @cindex query attached, remote request
37783 @cindex @samp{qAttached} packet
37784 Return an indication of whether the remote server attached to an
37785 existing process or created a new process. When the multiprocess
37786 protocol extensions are supported (@pxref{multiprocess extensions}),
37787 @var{pid} is an integer in hexadecimal format identifying the target
37788 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37789 the query packet will be simplified as @samp{qAttached}.
37791 This query is used, for example, to know whether the remote process
37792 should be detached or killed when a @value{GDBN} session is ended with
37793 the @code{quit} command.
37798 The remote server attached to an existing process.
37800 The remote server created a new process.
37802 A badly formed request or an error was encountered.
37806 Enable branch tracing for the current thread using Branch Trace Store.
37811 Branch tracing has been enabled.
37813 A badly formed request or an error was encountered.
37817 Enable branch tracing for the current thread using Intel Processor Trace.
37822 Branch tracing has been enabled.
37824 A badly formed request or an error was encountered.
37828 Disable branch tracing for the current thread.
37833 Branch tracing has been disabled.
37835 A badly formed request or an error was encountered.
37838 @item Qbtrace-conf:bts:size=@var{value}
37839 Set the requested ring buffer size for new threads that use the
37840 btrace recording method in bts format.
37845 The ring buffer size has been set.
37847 A badly formed request or an error was encountered.
37850 @item Qbtrace-conf:pt:size=@var{value}
37851 Set the requested ring buffer size for new threads that use the
37852 btrace recording method in pt format.
37857 The ring buffer size has been set.
37859 A badly formed request or an error was encountered.
37864 @node Architecture-Specific Protocol Details
37865 @section Architecture-Specific Protocol Details
37867 This section describes how the remote protocol is applied to specific
37868 target architectures. Also see @ref{Standard Target Features}, for
37869 details of XML target descriptions for each architecture.
37872 * ARM-Specific Protocol Details::
37873 * MIPS-Specific Protocol Details::
37876 @node ARM-Specific Protocol Details
37877 @subsection @acronym{ARM}-specific Protocol Details
37880 * ARM Breakpoint Kinds::
37883 @node ARM Breakpoint Kinds
37884 @subsubsection @acronym{ARM} Breakpoint Kinds
37885 @cindex breakpoint kinds, @acronym{ARM}
37887 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37892 16-bit Thumb mode breakpoint.
37895 32-bit Thumb mode (Thumb-2) breakpoint.
37898 32-bit @acronym{ARM} mode breakpoint.
37902 @node MIPS-Specific Protocol Details
37903 @subsection @acronym{MIPS}-specific Protocol Details
37906 * MIPS Register packet Format::
37907 * MIPS Breakpoint Kinds::
37910 @node MIPS Register packet Format
37911 @subsubsection @acronym{MIPS} Register Packet Format
37912 @cindex register packet format, @acronym{MIPS}
37914 The following @code{g}/@code{G} packets have previously been defined.
37915 In the below, some thirty-two bit registers are transferred as
37916 sixty-four bits. Those registers should be zero/sign extended (which?)
37917 to fill the space allocated. Register bytes are transferred in target
37918 byte order. The two nibbles within a register byte are transferred
37919 most-significant -- least-significant.
37924 All registers are transferred as thirty-two bit quantities in the order:
37925 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37926 registers; fsr; fir; fp.
37929 All registers are transferred as sixty-four bit quantities (including
37930 thirty-two bit registers such as @code{sr}). The ordering is the same
37935 @node MIPS Breakpoint Kinds
37936 @subsubsection @acronym{MIPS} Breakpoint Kinds
37937 @cindex breakpoint kinds, @acronym{MIPS}
37939 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37944 16-bit @acronym{MIPS16} mode breakpoint.
37947 16-bit @acronym{microMIPS} mode breakpoint.
37950 32-bit standard @acronym{MIPS} mode breakpoint.
37953 32-bit @acronym{microMIPS} mode breakpoint.
37957 @node Tracepoint Packets
37958 @section Tracepoint Packets
37959 @cindex tracepoint packets
37960 @cindex packets, tracepoint
37962 Here we describe the packets @value{GDBN} uses to implement
37963 tracepoints (@pxref{Tracepoints}).
37967 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37968 @cindex @samp{QTDP} packet
37969 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37970 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37971 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37972 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37973 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37974 the number of bytes that the target should copy elsewhere to make room
37975 for the tracepoint. If an @samp{X} is present, it introduces a
37976 tracepoint condition, which consists of a hexadecimal length, followed
37977 by a comma and hex-encoded bytes, in a manner similar to action
37978 encodings as described below. If the trailing @samp{-} is present,
37979 further @samp{QTDP} packets will follow to specify this tracepoint's
37985 The packet was understood and carried out.
37987 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37989 The packet was not recognized.
37992 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37993 Define actions to be taken when a tracepoint is hit. The @var{n} and
37994 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37995 this tracepoint. This packet may only be sent immediately after
37996 another @samp{QTDP} packet that ended with a @samp{-}. If the
37997 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37998 specifying more actions for this tracepoint.
38000 In the series of action packets for a given tracepoint, at most one
38001 can have an @samp{S} before its first @var{action}. If such a packet
38002 is sent, it and the following packets define ``while-stepping''
38003 actions. Any prior packets define ordinary actions --- that is, those
38004 taken when the tracepoint is first hit. If no action packet has an
38005 @samp{S}, then all the packets in the series specify ordinary
38006 tracepoint actions.
38008 The @samp{@var{action}@dots{}} portion of the packet is a series of
38009 actions, concatenated without separators. Each action has one of the
38015 Collect the registers whose bits are set in @var{mask},
38016 a hexadecimal number whose @var{i}'th bit is set if register number
38017 @var{i} should be collected. (The least significant bit is numbered
38018 zero.) Note that @var{mask} may be any number of digits long; it may
38019 not fit in a 32-bit word.
38021 @item M @var{basereg},@var{offset},@var{len}
38022 Collect @var{len} bytes of memory starting at the address in register
38023 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38024 @samp{-1}, then the range has a fixed address: @var{offset} is the
38025 address of the lowest byte to collect. The @var{basereg},
38026 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38027 values (the @samp{-1} value for @var{basereg} is a special case).
38029 @item X @var{len},@var{expr}
38030 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38031 it directs. The agent expression @var{expr} is as described in
38032 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38033 two-digit hex number in the packet; @var{len} is the number of bytes
38034 in the expression (and thus one-half the number of hex digits in the
38039 Any number of actions may be packed together in a single @samp{QTDP}
38040 packet, as long as the packet does not exceed the maximum packet
38041 length (400 bytes, for many stubs). There may be only one @samp{R}
38042 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38043 actions. Any registers referred to by @samp{M} and @samp{X} actions
38044 must be collected by a preceding @samp{R} action. (The
38045 ``while-stepping'' actions are treated as if they were attached to a
38046 separate tracepoint, as far as these restrictions are concerned.)
38051 The packet was understood and carried out.
38053 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38055 The packet was not recognized.
38058 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38059 @cindex @samp{QTDPsrc} packet
38060 Specify a source string of tracepoint @var{n} at address @var{addr}.
38061 This is useful to get accurate reproduction of the tracepoints
38062 originally downloaded at the beginning of the trace run. The @var{type}
38063 is the name of the tracepoint part, such as @samp{cond} for the
38064 tracepoint's conditional expression (see below for a list of types), while
38065 @var{bytes} is the string, encoded in hexadecimal.
38067 @var{start} is the offset of the @var{bytes} within the overall source
38068 string, while @var{slen} is the total length of the source string.
38069 This is intended for handling source strings that are longer than will
38070 fit in a single packet.
38071 @c Add detailed example when this info is moved into a dedicated
38072 @c tracepoint descriptions section.
38074 The available string types are @samp{at} for the location,
38075 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38076 @value{GDBN} sends a separate packet for each command in the action
38077 list, in the same order in which the commands are stored in the list.
38079 The target does not need to do anything with source strings except
38080 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38083 Although this packet is optional, and @value{GDBN} will only send it
38084 if the target replies with @samp{TracepointSource} @xref{General
38085 Query Packets}, it makes both disconnected tracing and trace files
38086 much easier to use. Otherwise the user must be careful that the
38087 tracepoints in effect while looking at trace frames are identical to
38088 the ones in effect during the trace run; even a small discrepancy
38089 could cause @samp{tdump} not to work, or a particular trace frame not
38092 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38093 @cindex define trace state variable, remote request
38094 @cindex @samp{QTDV} packet
38095 Create a new trace state variable, number @var{n}, with an initial
38096 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38097 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38098 the option of not using this packet for initial values of zero; the
38099 target should simply create the trace state variables as they are
38100 mentioned in expressions. The value @var{builtin} should be 1 (one)
38101 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38102 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38103 @samp{qTsV} packet had it set. The contents of @var{name} is the
38104 hex-encoded name (without the leading @samp{$}) of the trace state
38107 @item QTFrame:@var{n}
38108 @cindex @samp{QTFrame} packet
38109 Select the @var{n}'th tracepoint frame from the buffer, and use the
38110 register and memory contents recorded there to answer subsequent
38111 request packets from @value{GDBN}.
38113 A successful reply from the stub indicates that the stub has found the
38114 requested frame. The response is a series of parts, concatenated
38115 without separators, describing the frame we selected. Each part has
38116 one of the following forms:
38120 The selected frame is number @var{n} in the trace frame buffer;
38121 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38122 was no frame matching the criteria in the request packet.
38125 The selected trace frame records a hit of tracepoint number @var{t};
38126 @var{t} is a hexadecimal number.
38130 @item QTFrame:pc:@var{addr}
38131 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38132 currently selected frame whose PC is @var{addr};
38133 @var{addr} is a hexadecimal number.
38135 @item QTFrame:tdp:@var{t}
38136 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38137 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38138 is a hexadecimal number.
38140 @item QTFrame:range:@var{start}:@var{end}
38141 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38142 currently selected frame whose PC is between @var{start} (inclusive)
38143 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38146 @item QTFrame:outside:@var{start}:@var{end}
38147 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38148 frame @emph{outside} the given range of addresses (exclusive).
38151 @cindex @samp{qTMinFTPILen} packet
38152 This packet requests the minimum length of instruction at which a fast
38153 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38154 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38155 it depends on the target system being able to create trampolines in
38156 the first 64K of memory, which might or might not be possible for that
38157 system. So the reply to this packet will be 4 if it is able to
38164 The minimum instruction length is currently unknown.
38166 The minimum instruction length is @var{length}, where @var{length}
38167 is a hexadecimal number greater or equal to 1. A reply
38168 of 1 means that a fast tracepoint may be placed on any instruction
38169 regardless of size.
38171 An error has occurred.
38173 An empty reply indicates that the request is not supported by the stub.
38177 @cindex @samp{QTStart} packet
38178 Begin the tracepoint experiment. Begin collecting data from
38179 tracepoint hits in the trace frame buffer. This packet supports the
38180 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38181 instruction reply packet}).
38184 @cindex @samp{QTStop} packet
38185 End the tracepoint experiment. Stop collecting trace frames.
38187 @item QTEnable:@var{n}:@var{addr}
38189 @cindex @samp{QTEnable} packet
38190 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38191 experiment. If the tracepoint was previously disabled, then collection
38192 of data from it will resume.
38194 @item QTDisable:@var{n}:@var{addr}
38196 @cindex @samp{QTDisable} packet
38197 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38198 experiment. No more data will be collected from the tracepoint unless
38199 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38202 @cindex @samp{QTinit} packet
38203 Clear the table of tracepoints, and empty the trace frame buffer.
38205 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38206 @cindex @samp{QTro} packet
38207 Establish the given ranges of memory as ``transparent''. The stub
38208 will answer requests for these ranges from memory's current contents,
38209 if they were not collected as part of the tracepoint hit.
38211 @value{GDBN} uses this to mark read-only regions of memory, like those
38212 containing program code. Since these areas never change, they should
38213 still have the same contents they did when the tracepoint was hit, so
38214 there's no reason for the stub to refuse to provide their contents.
38216 @item QTDisconnected:@var{value}
38217 @cindex @samp{QTDisconnected} packet
38218 Set the choice to what to do with the tracing run when @value{GDBN}
38219 disconnects from the target. A @var{value} of 1 directs the target to
38220 continue the tracing run, while 0 tells the target to stop tracing if
38221 @value{GDBN} is no longer in the picture.
38224 @cindex @samp{qTStatus} packet
38225 Ask the stub if there is a trace experiment running right now.
38227 The reply has the form:
38231 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38232 @var{running} is a single digit @code{1} if the trace is presently
38233 running, or @code{0} if not. It is followed by semicolon-separated
38234 optional fields that an agent may use to report additional status.
38238 If the trace is not running, the agent may report any of several
38239 explanations as one of the optional fields:
38244 No trace has been run yet.
38246 @item tstop[:@var{text}]:0
38247 The trace was stopped by a user-originated stop command. The optional
38248 @var{text} field is a user-supplied string supplied as part of the
38249 stop command (for instance, an explanation of why the trace was
38250 stopped manually). It is hex-encoded.
38253 The trace stopped because the trace buffer filled up.
38255 @item tdisconnected:0
38256 The trace stopped because @value{GDBN} disconnected from the target.
38258 @item tpasscount:@var{tpnum}
38259 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38261 @item terror:@var{text}:@var{tpnum}
38262 The trace stopped because tracepoint @var{tpnum} had an error. The
38263 string @var{text} is available to describe the nature of the error
38264 (for instance, a divide by zero in the condition expression); it
38268 The trace stopped for some other reason.
38272 Additional optional fields supply statistical and other information.
38273 Although not required, they are extremely useful for users monitoring
38274 the progress of a trace run. If a trace has stopped, and these
38275 numbers are reported, they must reflect the state of the just-stopped
38280 @item tframes:@var{n}
38281 The number of trace frames in the buffer.
38283 @item tcreated:@var{n}
38284 The total number of trace frames created during the run. This may
38285 be larger than the trace frame count, if the buffer is circular.
38287 @item tsize:@var{n}
38288 The total size of the trace buffer, in bytes.
38290 @item tfree:@var{n}
38291 The number of bytes still unused in the buffer.
38293 @item circular:@var{n}
38294 The value of the circular trace buffer flag. @code{1} means that the
38295 trace buffer is circular and old trace frames will be discarded if
38296 necessary to make room, @code{0} means that the trace buffer is linear
38299 @item disconn:@var{n}
38300 The value of the disconnected tracing flag. @code{1} means that
38301 tracing will continue after @value{GDBN} disconnects, @code{0} means
38302 that the trace run will stop.
38306 @item qTP:@var{tp}:@var{addr}
38307 @cindex tracepoint status, remote request
38308 @cindex @samp{qTP} packet
38309 Ask the stub for the current state of tracepoint number @var{tp} at
38310 address @var{addr}.
38314 @item V@var{hits}:@var{usage}
38315 The tracepoint has been hit @var{hits} times so far during the trace
38316 run, and accounts for @var{usage} in the trace buffer. Note that
38317 @code{while-stepping} steps are not counted as separate hits, but the
38318 steps' space consumption is added into the usage number.
38322 @item qTV:@var{var}
38323 @cindex trace state variable value, remote request
38324 @cindex @samp{qTV} packet
38325 Ask the stub for the value of the trace state variable number @var{var}.
38330 The value of the variable is @var{value}. This will be the current
38331 value of the variable if the user is examining a running target, or a
38332 saved value if the variable was collected in the trace frame that the
38333 user is looking at. Note that multiple requests may result in
38334 different reply values, such as when requesting values while the
38335 program is running.
38338 The value of the variable is unknown. This would occur, for example,
38339 if the user is examining a trace frame in which the requested variable
38344 @cindex @samp{qTfP} packet
38346 @cindex @samp{qTsP} packet
38347 These packets request data about tracepoints that are being used by
38348 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38349 of data, and multiple @code{qTsP} to get additional pieces. Replies
38350 to these packets generally take the form of the @code{QTDP} packets
38351 that define tracepoints. (FIXME add detailed syntax)
38354 @cindex @samp{qTfV} packet
38356 @cindex @samp{qTsV} packet
38357 These packets request data about trace state variables that are on the
38358 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38359 and multiple @code{qTsV} to get additional variables. Replies to
38360 these packets follow the syntax of the @code{QTDV} packets that define
38361 trace state variables.
38367 @cindex @samp{qTfSTM} packet
38368 @cindex @samp{qTsSTM} packet
38369 These packets request data about static tracepoint markers that exist
38370 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38371 first piece of data, and multiple @code{qTsSTM} to get additional
38372 pieces. Replies to these packets take the following form:
38376 @item m @var{address}:@var{id}:@var{extra}
38378 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38379 a comma-separated list of markers
38381 (lower case letter @samp{L}) denotes end of list.
38383 An error occurred. The error number @var{nn} is given as hex digits.
38385 An empty reply indicates that the request is not supported by the
38389 The @var{address} is encoded in hex;
38390 @var{id} and @var{extra} are strings encoded in hex.
38392 In response to each query, the target will reply with a list of one or
38393 more markers, separated by commas. @value{GDBN} will respond to each
38394 reply with a request for more markers (using the @samp{qs} form of the
38395 query), until the target responds with @samp{l} (lower-case ell, for
38398 @item qTSTMat:@var{address}
38400 @cindex @samp{qTSTMat} packet
38401 This packets requests data about static tracepoint markers in the
38402 target program at @var{address}. Replies to this packet follow the
38403 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38404 tracepoint markers.
38406 @item QTSave:@var{filename}
38407 @cindex @samp{QTSave} packet
38408 This packet directs the target to save trace data to the file name
38409 @var{filename} in the target's filesystem. The @var{filename} is encoded
38410 as a hex string; the interpretation of the file name (relative vs
38411 absolute, wild cards, etc) is up to the target.
38413 @item qTBuffer:@var{offset},@var{len}
38414 @cindex @samp{qTBuffer} packet
38415 Return up to @var{len} bytes of the current contents of trace buffer,
38416 starting at @var{offset}. The trace buffer is treated as if it were
38417 a contiguous collection of traceframes, as per the trace file format.
38418 The reply consists as many hex-encoded bytes as the target can deliver
38419 in a packet; it is not an error to return fewer than were asked for.
38420 A reply consisting of just @code{l} indicates that no bytes are
38423 @item QTBuffer:circular:@var{value}
38424 This packet directs the target to use a circular trace buffer if
38425 @var{value} is 1, or a linear buffer if the value is 0.
38427 @item QTBuffer:size:@var{size}
38428 @anchor{QTBuffer-size}
38429 @cindex @samp{QTBuffer size} packet
38430 This packet directs the target to make the trace buffer be of size
38431 @var{size} if possible. A value of @code{-1} tells the target to
38432 use whatever size it prefers.
38434 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38435 @cindex @samp{QTNotes} packet
38436 This packet adds optional textual notes to the trace run. Allowable
38437 types include @code{user}, @code{notes}, and @code{tstop}, the
38438 @var{text} fields are arbitrary strings, hex-encoded.
38442 @subsection Relocate instruction reply packet
38443 When installing fast tracepoints in memory, the target may need to
38444 relocate the instruction currently at the tracepoint address to a
38445 different address in memory. For most instructions, a simple copy is
38446 enough, but, for example, call instructions that implicitly push the
38447 return address on the stack, and relative branches or other
38448 PC-relative instructions require offset adjustment, so that the effect
38449 of executing the instruction at a different address is the same as if
38450 it had executed in the original location.
38452 In response to several of the tracepoint packets, the target may also
38453 respond with a number of intermediate @samp{qRelocInsn} request
38454 packets before the final result packet, to have @value{GDBN} handle
38455 this relocation operation. If a packet supports this mechanism, its
38456 documentation will explicitly say so. See for example the above
38457 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38458 format of the request is:
38461 @item qRelocInsn:@var{from};@var{to}
38463 This requests @value{GDBN} to copy instruction at address @var{from}
38464 to address @var{to}, possibly adjusted so that executing the
38465 instruction at @var{to} has the same effect as executing it at
38466 @var{from}. @value{GDBN} writes the adjusted instruction to target
38467 memory starting at @var{to}.
38472 @item qRelocInsn:@var{adjusted_size}
38473 Informs the stub the relocation is complete. The @var{adjusted_size} is
38474 the length in bytes of resulting relocated instruction sequence.
38476 A badly formed request was detected, or an error was encountered while
38477 relocating the instruction.
38480 @node Host I/O Packets
38481 @section Host I/O Packets
38482 @cindex Host I/O, remote protocol
38483 @cindex file transfer, remote protocol
38485 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38486 operations on the far side of a remote link. For example, Host I/O is
38487 used to upload and download files to a remote target with its own
38488 filesystem. Host I/O uses the same constant values and data structure
38489 layout as the target-initiated File-I/O protocol. However, the
38490 Host I/O packets are structured differently. The target-initiated
38491 protocol relies on target memory to store parameters and buffers.
38492 Host I/O requests are initiated by @value{GDBN}, and the
38493 target's memory is not involved. @xref{File-I/O Remote Protocol
38494 Extension}, for more details on the target-initiated protocol.
38496 The Host I/O request packets all encode a single operation along with
38497 its arguments. They have this format:
38501 @item vFile:@var{operation}: @var{parameter}@dots{}
38502 @var{operation} is the name of the particular request; the target
38503 should compare the entire packet name up to the second colon when checking
38504 for a supported operation. The format of @var{parameter} depends on
38505 the operation. Numbers are always passed in hexadecimal. Negative
38506 numbers have an explicit minus sign (i.e.@: two's complement is not
38507 used). Strings (e.g.@: filenames) are encoded as a series of
38508 hexadecimal bytes. The last argument to a system call may be a
38509 buffer of escaped binary data (@pxref{Binary Data}).
38513 The valid responses to Host I/O packets are:
38517 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38518 @var{result} is the integer value returned by this operation, usually
38519 non-negative for success and -1 for errors. If an error has occured,
38520 @var{errno} will be included in the result specifying a
38521 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38522 operations which return data, @var{attachment} supplies the data as a
38523 binary buffer. Binary buffers in response packets are escaped in the
38524 normal way (@pxref{Binary Data}). See the individual packet
38525 documentation for the interpretation of @var{result} and
38529 An empty response indicates that this operation is not recognized.
38533 These are the supported Host I/O operations:
38536 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38537 Open a file at @var{filename} and return a file descriptor for it, or
38538 return -1 if an error occurs. The @var{filename} is a string,
38539 @var{flags} is an integer indicating a mask of open flags
38540 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38541 of mode bits to use if the file is created (@pxref{mode_t Values}).
38542 @xref{open}, for details of the open flags and mode values.
38544 @item vFile:close: @var{fd}
38545 Close the open file corresponding to @var{fd} and return 0, or
38546 -1 if an error occurs.
38548 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38549 Read data from the open file corresponding to @var{fd}. Up to
38550 @var{count} bytes will be read from the file, starting at @var{offset}
38551 relative to the start of the file. The target may read fewer bytes;
38552 common reasons include packet size limits and an end-of-file
38553 condition. The number of bytes read is returned. Zero should only be
38554 returned for a successful read at the end of the file, or if
38555 @var{count} was zero.
38557 The data read should be returned as a binary attachment on success.
38558 If zero bytes were read, the response should include an empty binary
38559 attachment (i.e.@: a trailing semicolon). The return value is the
38560 number of target bytes read; the binary attachment may be longer if
38561 some characters were escaped.
38563 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38564 Write @var{data} (a binary buffer) to the open file corresponding
38565 to @var{fd}. Start the write at @var{offset} from the start of the
38566 file. Unlike many @code{write} system calls, there is no
38567 separate @var{count} argument; the length of @var{data} in the
38568 packet is used. @samp{vFile:write} returns the number of bytes written,
38569 which may be shorter than the length of @var{data}, or -1 if an
38572 @item vFile:fstat: @var{fd}
38573 Get information about the open file corresponding to @var{fd}.
38574 On success the information is returned as a binary attachment
38575 and the return value is the size of this attachment in bytes.
38576 If an error occurs the return value is -1. The format of the
38577 returned binary attachment is as described in @ref{struct stat}.
38579 @item vFile:unlink: @var{filename}
38580 Delete the file at @var{filename} on the target. Return 0,
38581 or -1 if an error occurs. The @var{filename} is a string.
38583 @item vFile:readlink: @var{filename}
38584 Read value of symbolic link @var{filename} on the target. Return
38585 the number of bytes read, or -1 if an error occurs.
38587 The data read should be returned as a binary attachment on success.
38588 If zero bytes were read, the response should include an empty binary
38589 attachment (i.e.@: a trailing semicolon). The return value is the
38590 number of target bytes read; the binary attachment may be longer if
38591 some characters were escaped.
38593 @item vFile:setfs: @var{pid}
38594 Select the filesystem on which @code{vFile} operations with
38595 @var{filename} arguments will operate. This is required for
38596 @value{GDBN} to be able to access files on remote targets where
38597 the remote stub does not share a common filesystem with the
38600 If @var{pid} is nonzero, select the filesystem as seen by process
38601 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38602 the remote stub. Return 0 on success, or -1 if an error occurs.
38603 If @code{vFile:setfs:} indicates success, the selected filesystem
38604 remains selected until the next successful @code{vFile:setfs:}
38610 @section Interrupts
38611 @cindex interrupts (remote protocol)
38612 @anchor{interrupting remote targets}
38614 In all-stop mode, when a program on the remote target is running,
38615 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38616 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38617 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38619 The precise meaning of @code{BREAK} is defined by the transport
38620 mechanism and may, in fact, be undefined. @value{GDBN} does not
38621 currently define a @code{BREAK} mechanism for any of the network
38622 interfaces except for TCP, in which case @value{GDBN} sends the
38623 @code{telnet} BREAK sequence.
38625 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38626 transport mechanisms. It is represented by sending the single byte
38627 @code{0x03} without any of the usual packet overhead described in
38628 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38629 transmitted as part of a packet, it is considered to be packet data
38630 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38631 (@pxref{X packet}), used for binary downloads, may include an unescaped
38632 @code{0x03} as part of its packet.
38634 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38635 When Linux kernel receives this sequence from serial port,
38636 it stops execution and connects to gdb.
38638 In non-stop mode, because packet resumptions are asynchronous
38639 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38640 command to the remote stub, even when the target is running. For that
38641 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38642 packet}) with the usual packet framing instead of the single byte
38645 Stubs are not required to recognize these interrupt mechanisms and the
38646 precise meaning associated with receipt of the interrupt is
38647 implementation defined. If the target supports debugging of multiple
38648 threads and/or processes, it should attempt to interrupt all
38649 currently-executing threads and processes.
38650 If the stub is successful at interrupting the
38651 running program, it should send one of the stop
38652 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38653 of successfully stopping the program in all-stop mode, and a stop reply
38654 for each stopped thread in non-stop mode.
38655 Interrupts received while the
38656 program is stopped are queued and the program will be interrupted when
38657 it is resumed next time.
38659 @node Notification Packets
38660 @section Notification Packets
38661 @cindex notification packets
38662 @cindex packets, notification
38664 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38665 packets that require no acknowledgment. Both the GDB and the stub
38666 may send notifications (although the only notifications defined at
38667 present are sent by the stub). Notifications carry information
38668 without incurring the round-trip latency of an acknowledgment, and so
38669 are useful for low-impact communications where occasional packet loss
38672 A notification packet has the form @samp{% @var{data} #
38673 @var{checksum}}, where @var{data} is the content of the notification,
38674 and @var{checksum} is a checksum of @var{data}, computed and formatted
38675 as for ordinary @value{GDBN} packets. A notification's @var{data}
38676 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38677 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38678 to acknowledge the notification's receipt or to report its corruption.
38680 Every notification's @var{data} begins with a name, which contains no
38681 colon characters, followed by a colon character.
38683 Recipients should silently ignore corrupted notifications and
38684 notifications they do not understand. Recipients should restart
38685 timeout periods on receipt of a well-formed notification, whether or
38686 not they understand it.
38688 Senders should only send the notifications described here when this
38689 protocol description specifies that they are permitted. In the
38690 future, we may extend the protocol to permit existing notifications in
38691 new contexts; this rule helps older senders avoid confusing newer
38694 (Older versions of @value{GDBN} ignore bytes received until they see
38695 the @samp{$} byte that begins an ordinary packet, so new stubs may
38696 transmit notifications without fear of confusing older clients. There
38697 are no notifications defined for @value{GDBN} to send at the moment, but we
38698 assume that most older stubs would ignore them, as well.)
38700 Each notification is comprised of three parts:
38702 @item @var{name}:@var{event}
38703 The notification packet is sent by the side that initiates the
38704 exchange (currently, only the stub does that), with @var{event}
38705 carrying the specific information about the notification, and
38706 @var{name} specifying the name of the notification.
38708 The acknowledge sent by the other side, usually @value{GDBN}, to
38709 acknowledge the exchange and request the event.
38712 The purpose of an asynchronous notification mechanism is to report to
38713 @value{GDBN} that something interesting happened in the remote stub.
38715 The remote stub may send notification @var{name}:@var{event}
38716 at any time, but @value{GDBN} acknowledges the notification when
38717 appropriate. The notification event is pending before @value{GDBN}
38718 acknowledges. Only one notification at a time may be pending; if
38719 additional events occur before @value{GDBN} has acknowledged the
38720 previous notification, they must be queued by the stub for later
38721 synchronous transmission in response to @var{ack} packets from
38722 @value{GDBN}. Because the notification mechanism is unreliable,
38723 the stub is permitted to resend a notification if it believes
38724 @value{GDBN} may not have received it.
38726 Specifically, notifications may appear when @value{GDBN} is not
38727 otherwise reading input from the stub, or when @value{GDBN} is
38728 expecting to read a normal synchronous response or a
38729 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38730 Notification packets are distinct from any other communication from
38731 the stub so there is no ambiguity.
38733 After receiving a notification, @value{GDBN} shall acknowledge it by
38734 sending a @var{ack} packet as a regular, synchronous request to the
38735 stub. Such acknowledgment is not required to happen immediately, as
38736 @value{GDBN} is permitted to send other, unrelated packets to the
38737 stub first, which the stub should process normally.
38739 Upon receiving a @var{ack} packet, if the stub has other queued
38740 events to report to @value{GDBN}, it shall respond by sending a
38741 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38742 packet to solicit further responses; again, it is permitted to send
38743 other, unrelated packets as well which the stub should process
38746 If the stub receives a @var{ack} packet and there are no additional
38747 @var{event} to report, the stub shall return an @samp{OK} response.
38748 At this point, @value{GDBN} has finished processing a notification
38749 and the stub has completed sending any queued events. @value{GDBN}
38750 won't accept any new notifications until the final @samp{OK} is
38751 received . If further notification events occur, the stub shall send
38752 a new notification, @value{GDBN} shall accept the notification, and
38753 the process shall be repeated.
38755 The process of asynchronous notification can be illustrated by the
38758 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38761 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38763 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38768 The following notifications are defined:
38769 @multitable @columnfractions 0.12 0.12 0.38 0.38
38778 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38779 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38780 for information on how these notifications are acknowledged by
38782 @tab Report an asynchronous stop event in non-stop mode.
38786 @node Remote Non-Stop
38787 @section Remote Protocol Support for Non-Stop Mode
38789 @value{GDBN}'s remote protocol supports non-stop debugging of
38790 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38791 supports non-stop mode, it should report that to @value{GDBN} by including
38792 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38794 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38795 establishing a new connection with the stub. Entering non-stop mode
38796 does not alter the state of any currently-running threads, but targets
38797 must stop all threads in any already-attached processes when entering
38798 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38799 probe the target state after a mode change.
38801 In non-stop mode, when an attached process encounters an event that
38802 would otherwise be reported with a stop reply, it uses the
38803 asynchronous notification mechanism (@pxref{Notification Packets}) to
38804 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38805 in all processes are stopped when a stop reply is sent, in non-stop
38806 mode only the thread reporting the stop event is stopped. That is,
38807 when reporting a @samp{S} or @samp{T} response to indicate completion
38808 of a step operation, hitting a breakpoint, or a fault, only the
38809 affected thread is stopped; any other still-running threads continue
38810 to run. When reporting a @samp{W} or @samp{X} response, all running
38811 threads belonging to other attached processes continue to run.
38813 In non-stop mode, the target shall respond to the @samp{?} packet as
38814 follows. First, any incomplete stop reply notification/@samp{vStopped}
38815 sequence in progress is abandoned. The target must begin a new
38816 sequence reporting stop events for all stopped threads, whether or not
38817 it has previously reported those events to @value{GDBN}. The first
38818 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38819 subsequent stop replies are sent as responses to @samp{vStopped} packets
38820 using the mechanism described above. The target must not send
38821 asynchronous stop reply notifications until the sequence is complete.
38822 If all threads are running when the target receives the @samp{?} packet,
38823 or if the target is not attached to any process, it shall respond
38826 If the stub supports non-stop mode, it should also support the
38827 @samp{swbreak} stop reason if software breakpoints are supported, and
38828 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38829 (@pxref{swbreak stop reason}). This is because given the asynchronous
38830 nature of non-stop mode, between the time a thread hits a breakpoint
38831 and the time the event is finally processed by @value{GDBN}, the
38832 breakpoint may have already been removed from the target. Due to
38833 this, @value{GDBN} needs to be able to tell whether a trap stop was
38834 caused by a delayed breakpoint event, which should be ignored, as
38835 opposed to a random trap signal, which should be reported to the user.
38836 Note the @samp{swbreak} feature implies that the target is responsible
38837 for adjusting the PC when a software breakpoint triggers, if
38838 necessary, such as on the x86 architecture.
38840 @node Packet Acknowledgment
38841 @section Packet Acknowledgment
38843 @cindex acknowledgment, for @value{GDBN} remote
38844 @cindex packet acknowledgment, for @value{GDBN} remote
38845 By default, when either the host or the target machine receives a packet,
38846 the first response expected is an acknowledgment: either @samp{+} (to indicate
38847 the package was received correctly) or @samp{-} (to request retransmission).
38848 This mechanism allows the @value{GDBN} remote protocol to operate over
38849 unreliable transport mechanisms, such as a serial line.
38851 In cases where the transport mechanism is itself reliable (such as a pipe or
38852 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38853 It may be desirable to disable them in that case to reduce communication
38854 overhead, or for other reasons. This can be accomplished by means of the
38855 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38857 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38858 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38859 and response format still includes the normal checksum, as described in
38860 @ref{Overview}, but the checksum may be ignored by the receiver.
38862 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38863 no-acknowledgment mode, it should report that to @value{GDBN}
38864 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38865 @pxref{qSupported}.
38866 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38867 disabled via the @code{set remote noack-packet off} command
38868 (@pxref{Remote Configuration}),
38869 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38870 Only then may the stub actually turn off packet acknowledgments.
38871 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38872 response, which can be safely ignored by the stub.
38874 Note that @code{set remote noack-packet} command only affects negotiation
38875 between @value{GDBN} and the stub when subsequent connections are made;
38876 it does not affect the protocol acknowledgment state for any current
38878 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38879 new connection is established,
38880 there is also no protocol request to re-enable the acknowledgments
38881 for the current connection, once disabled.
38886 Example sequence of a target being re-started. Notice how the restart
38887 does not get any direct output:
38892 @emph{target restarts}
38895 <- @code{T001:1234123412341234}
38899 Example sequence of a target being stepped by a single instruction:
38902 -> @code{G1445@dots{}}
38907 <- @code{T001:1234123412341234}
38911 <- @code{1455@dots{}}
38915 @node File-I/O Remote Protocol Extension
38916 @section File-I/O Remote Protocol Extension
38917 @cindex File-I/O remote protocol extension
38920 * File-I/O Overview::
38921 * Protocol Basics::
38922 * The F Request Packet::
38923 * The F Reply Packet::
38924 * The Ctrl-C Message::
38926 * List of Supported Calls::
38927 * Protocol-specific Representation of Datatypes::
38929 * File-I/O Examples::
38932 @node File-I/O Overview
38933 @subsection File-I/O Overview
38934 @cindex file-i/o overview
38936 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38937 target to use the host's file system and console I/O to perform various
38938 system calls. System calls on the target system are translated into a
38939 remote protocol packet to the host system, which then performs the needed
38940 actions and returns a response packet to the target system.
38941 This simulates file system operations even on targets that lack file systems.
38943 The protocol is defined to be independent of both the host and target systems.
38944 It uses its own internal representation of datatypes and values. Both
38945 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38946 translating the system-dependent value representations into the internal
38947 protocol representations when data is transmitted.
38949 The communication is synchronous. A system call is possible only when
38950 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38951 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38952 the target is stopped to allow deterministic access to the target's
38953 memory. Therefore File-I/O is not interruptible by target signals. On
38954 the other hand, it is possible to interrupt File-I/O by a user interrupt
38955 (@samp{Ctrl-C}) within @value{GDBN}.
38957 The target's request to perform a host system call does not finish
38958 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38959 after finishing the system call, the target returns to continuing the
38960 previous activity (continue, step). No additional continue or step
38961 request from @value{GDBN} is required.
38964 (@value{GDBP}) continue
38965 <- target requests 'system call X'
38966 target is stopped, @value{GDBN} executes system call
38967 -> @value{GDBN} returns result
38968 ... target continues, @value{GDBN} returns to wait for the target
38969 <- target hits breakpoint and sends a Txx packet
38972 The protocol only supports I/O on the console and to regular files on
38973 the host file system. Character or block special devices, pipes,
38974 named pipes, sockets or any other communication method on the host
38975 system are not supported by this protocol.
38977 File I/O is not supported in non-stop mode.
38979 @node Protocol Basics
38980 @subsection Protocol Basics
38981 @cindex protocol basics, file-i/o
38983 The File-I/O protocol uses the @code{F} packet as the request as well
38984 as reply packet. Since a File-I/O system call can only occur when
38985 @value{GDBN} is waiting for a response from the continuing or stepping target,
38986 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38987 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38988 This @code{F} packet contains all information needed to allow @value{GDBN}
38989 to call the appropriate host system call:
38993 A unique identifier for the requested system call.
38996 All parameters to the system call. Pointers are given as addresses
38997 in the target memory address space. Pointers to strings are given as
38998 pointer/length pair. Numerical values are given as they are.
38999 Numerical control flags are given in a protocol-specific representation.
39003 At this point, @value{GDBN} has to perform the following actions.
39007 If the parameters include pointer values to data needed as input to a
39008 system call, @value{GDBN} requests this data from the target with a
39009 standard @code{m} packet request. This additional communication has to be
39010 expected by the target implementation and is handled as any other @code{m}
39014 @value{GDBN} translates all value from protocol representation to host
39015 representation as needed. Datatypes are coerced into the host types.
39018 @value{GDBN} calls the system call.
39021 It then coerces datatypes back to protocol representation.
39024 If the system call is expected to return data in buffer space specified
39025 by pointer parameters to the call, the data is transmitted to the
39026 target using a @code{M} or @code{X} packet. This packet has to be expected
39027 by the target implementation and is handled as any other @code{M} or @code{X}
39032 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39033 necessary information for the target to continue. This at least contains
39040 @code{errno}, if has been changed by the system call.
39047 After having done the needed type and value coercion, the target continues
39048 the latest continue or step action.
39050 @node The F Request Packet
39051 @subsection The @code{F} Request Packet
39052 @cindex file-i/o request packet
39053 @cindex @code{F} request packet
39055 The @code{F} request packet has the following format:
39058 @item F@var{call-id},@var{parameter@dots{}}
39060 @var{call-id} is the identifier to indicate the host system call to be called.
39061 This is just the name of the function.
39063 @var{parameter@dots{}} are the parameters to the system call.
39064 Parameters are hexadecimal integer values, either the actual values in case
39065 of scalar datatypes, pointers to target buffer space in case of compound
39066 datatypes and unspecified memory areas, or pointer/length pairs in case
39067 of string parameters. These are appended to the @var{call-id} as a
39068 comma-delimited list. All values are transmitted in ASCII
39069 string representation, pointer/length pairs separated by a slash.
39075 @node The F Reply Packet
39076 @subsection The @code{F} Reply Packet
39077 @cindex file-i/o reply packet
39078 @cindex @code{F} reply packet
39080 The @code{F} reply packet has the following format:
39084 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39086 @var{retcode} is the return code of the system call as hexadecimal value.
39088 @var{errno} is the @code{errno} set by the call, in protocol-specific
39090 This parameter can be omitted if the call was successful.
39092 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39093 case, @var{errno} must be sent as well, even if the call was successful.
39094 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39101 or, if the call was interrupted before the host call has been performed:
39108 assuming 4 is the protocol-specific representation of @code{EINTR}.
39113 @node The Ctrl-C Message
39114 @subsection The @samp{Ctrl-C} Message
39115 @cindex ctrl-c message, in file-i/o protocol
39117 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39118 reply packet (@pxref{The F Reply Packet}),
39119 the target should behave as if it had
39120 gotten a break message. The meaning for the target is ``system call
39121 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39122 (as with a break message) and return to @value{GDBN} with a @code{T02}
39125 It's important for the target to know in which
39126 state the system call was interrupted. There are two possible cases:
39130 The system call hasn't been performed on the host yet.
39133 The system call on the host has been finished.
39137 These two states can be distinguished by the target by the value of the
39138 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39139 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39140 on POSIX systems. In any other case, the target may presume that the
39141 system call has been finished --- successfully or not --- and should behave
39142 as if the break message arrived right after the system call.
39144 @value{GDBN} must behave reliably. If the system call has not been called
39145 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39146 @code{errno} in the packet. If the system call on the host has been finished
39147 before the user requests a break, the full action must be finished by
39148 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39149 The @code{F} packet may only be sent when either nothing has happened
39150 or the full action has been completed.
39153 @subsection Console I/O
39154 @cindex console i/o as part of file-i/o
39156 By default and if not explicitly closed by the target system, the file
39157 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39158 on the @value{GDBN} console is handled as any other file output operation
39159 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39160 by @value{GDBN} so that after the target read request from file descriptor
39161 0 all following typing is buffered until either one of the following
39166 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39168 system call is treated as finished.
39171 The user presses @key{RET}. This is treated as end of input with a trailing
39175 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39176 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39180 If the user has typed more characters than fit in the buffer given to
39181 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39182 either another @code{read(0, @dots{})} is requested by the target, or debugging
39183 is stopped at the user's request.
39186 @node List of Supported Calls
39187 @subsection List of Supported Calls
39188 @cindex list of supported file-i/o calls
39205 @unnumberedsubsubsec open
39206 @cindex open, file-i/o system call
39211 int open(const char *pathname, int flags);
39212 int open(const char *pathname, int flags, mode_t mode);
39216 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39219 @var{flags} is the bitwise @code{OR} of the following values:
39223 If the file does not exist it will be created. The host
39224 rules apply as far as file ownership and time stamps
39228 When used with @code{O_CREAT}, if the file already exists it is
39229 an error and open() fails.
39232 If the file already exists and the open mode allows
39233 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39234 truncated to zero length.
39237 The file is opened in append mode.
39240 The file is opened for reading only.
39243 The file is opened for writing only.
39246 The file is opened for reading and writing.
39250 Other bits are silently ignored.
39254 @var{mode} is the bitwise @code{OR} of the following values:
39258 User has read permission.
39261 User has write permission.
39264 Group has read permission.
39267 Group has write permission.
39270 Others have read permission.
39273 Others have write permission.
39277 Other bits are silently ignored.
39280 @item Return value:
39281 @code{open} returns the new file descriptor or -1 if an error
39288 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39291 @var{pathname} refers to a directory.
39294 The requested access is not allowed.
39297 @var{pathname} was too long.
39300 A directory component in @var{pathname} does not exist.
39303 @var{pathname} refers to a device, pipe, named pipe or socket.
39306 @var{pathname} refers to a file on a read-only filesystem and
39307 write access was requested.
39310 @var{pathname} is an invalid pointer value.
39313 No space on device to create the file.
39316 The process already has the maximum number of files open.
39319 The limit on the total number of files open on the system
39323 The call was interrupted by the user.
39329 @unnumberedsubsubsec close
39330 @cindex close, file-i/o system call
39339 @samp{Fclose,@var{fd}}
39341 @item Return value:
39342 @code{close} returns zero on success, or -1 if an error occurred.
39348 @var{fd} isn't a valid open file descriptor.
39351 The call was interrupted by the user.
39357 @unnumberedsubsubsec read
39358 @cindex read, file-i/o system call
39363 int read(int fd, void *buf, unsigned int count);
39367 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39369 @item Return value:
39370 On success, the number of bytes read is returned.
39371 Zero indicates end of file. If count is zero, read
39372 returns zero as well. On error, -1 is returned.
39378 @var{fd} is not a valid file descriptor or is not open for
39382 @var{bufptr} is an invalid pointer value.
39385 The call was interrupted by the user.
39391 @unnumberedsubsubsec write
39392 @cindex write, file-i/o system call
39397 int write(int fd, const void *buf, unsigned int count);
39401 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39403 @item Return value:
39404 On success, the number of bytes written are returned.
39405 Zero indicates nothing was written. On error, -1
39412 @var{fd} is not a valid file descriptor or is not open for
39416 @var{bufptr} is an invalid pointer value.
39419 An attempt was made to write a file that exceeds the
39420 host-specific maximum file size allowed.
39423 No space on device to write the data.
39426 The call was interrupted by the user.
39432 @unnumberedsubsubsec lseek
39433 @cindex lseek, file-i/o system call
39438 long lseek (int fd, long offset, int flag);
39442 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39444 @var{flag} is one of:
39448 The offset is set to @var{offset} bytes.
39451 The offset is set to its current location plus @var{offset}
39455 The offset is set to the size of the file plus @var{offset}
39459 @item Return value:
39460 On success, the resulting unsigned offset in bytes from
39461 the beginning of the file is returned. Otherwise, a
39462 value of -1 is returned.
39468 @var{fd} is not a valid open file descriptor.
39471 @var{fd} is associated with the @value{GDBN} console.
39474 @var{flag} is not a proper value.
39477 The call was interrupted by the user.
39483 @unnumberedsubsubsec rename
39484 @cindex rename, file-i/o system call
39489 int rename(const char *oldpath, const char *newpath);
39493 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39495 @item Return value:
39496 On success, zero is returned. On error, -1 is returned.
39502 @var{newpath} is an existing directory, but @var{oldpath} is not a
39506 @var{newpath} is a non-empty directory.
39509 @var{oldpath} or @var{newpath} is a directory that is in use by some
39513 An attempt was made to make a directory a subdirectory
39517 A component used as a directory in @var{oldpath} or new
39518 path is not a directory. Or @var{oldpath} is a directory
39519 and @var{newpath} exists but is not a directory.
39522 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39525 No access to the file or the path of the file.
39529 @var{oldpath} or @var{newpath} was too long.
39532 A directory component in @var{oldpath} or @var{newpath} does not exist.
39535 The file is on a read-only filesystem.
39538 The device containing the file has no room for the new
39542 The call was interrupted by the user.
39548 @unnumberedsubsubsec unlink
39549 @cindex unlink, file-i/o system call
39554 int unlink(const char *pathname);
39558 @samp{Funlink,@var{pathnameptr}/@var{len}}
39560 @item Return value:
39561 On success, zero is returned. On error, -1 is returned.
39567 No access to the file or the path of the file.
39570 The system does not allow unlinking of directories.
39573 The file @var{pathname} cannot be unlinked because it's
39574 being used by another process.
39577 @var{pathnameptr} is an invalid pointer value.
39580 @var{pathname} was too long.
39583 A directory component in @var{pathname} does not exist.
39586 A component of the path is not a directory.
39589 The file is on a read-only filesystem.
39592 The call was interrupted by the user.
39598 @unnumberedsubsubsec stat/fstat
39599 @cindex fstat, file-i/o system call
39600 @cindex stat, file-i/o system call
39605 int stat(const char *pathname, struct stat *buf);
39606 int fstat(int fd, struct stat *buf);
39610 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39611 @samp{Ffstat,@var{fd},@var{bufptr}}
39613 @item Return value:
39614 On success, zero is returned. On error, -1 is returned.
39620 @var{fd} is not a valid open file.
39623 A directory component in @var{pathname} does not exist or the
39624 path is an empty string.
39627 A component of the path is not a directory.
39630 @var{pathnameptr} is an invalid pointer value.
39633 No access to the file or the path of the file.
39636 @var{pathname} was too long.
39639 The call was interrupted by the user.
39645 @unnumberedsubsubsec gettimeofday
39646 @cindex gettimeofday, file-i/o system call
39651 int gettimeofday(struct timeval *tv, void *tz);
39655 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39657 @item Return value:
39658 On success, 0 is returned, -1 otherwise.
39664 @var{tz} is a non-NULL pointer.
39667 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39673 @unnumberedsubsubsec isatty
39674 @cindex isatty, file-i/o system call
39679 int isatty(int fd);
39683 @samp{Fisatty,@var{fd}}
39685 @item Return value:
39686 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39692 The call was interrupted by the user.
39697 Note that the @code{isatty} call is treated as a special case: it returns
39698 1 to the target if the file descriptor is attached
39699 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39700 would require implementing @code{ioctl} and would be more complex than
39705 @unnumberedsubsubsec system
39706 @cindex system, file-i/o system call
39711 int system(const char *command);
39715 @samp{Fsystem,@var{commandptr}/@var{len}}
39717 @item Return value:
39718 If @var{len} is zero, the return value indicates whether a shell is
39719 available. A zero return value indicates a shell is not available.
39720 For non-zero @var{len}, the value returned is -1 on error and the
39721 return status of the command otherwise. Only the exit status of the
39722 command is returned, which is extracted from the host's @code{system}
39723 return value by calling @code{WEXITSTATUS(retval)}. In case
39724 @file{/bin/sh} could not be executed, 127 is returned.
39730 The call was interrupted by the user.
39735 @value{GDBN} takes over the full task of calling the necessary host calls
39736 to perform the @code{system} call. The return value of @code{system} on
39737 the host is simplified before it's returned
39738 to the target. Any termination signal information from the child process
39739 is discarded, and the return value consists
39740 entirely of the exit status of the called command.
39742 Due to security concerns, the @code{system} call is by default refused
39743 by @value{GDBN}. The user has to allow this call explicitly with the
39744 @code{set remote system-call-allowed 1} command.
39747 @item set remote system-call-allowed
39748 @kindex set remote system-call-allowed
39749 Control whether to allow the @code{system} calls in the File I/O
39750 protocol for the remote target. The default is zero (disabled).
39752 @item show remote system-call-allowed
39753 @kindex show remote system-call-allowed
39754 Show whether the @code{system} calls are allowed in the File I/O
39758 @node Protocol-specific Representation of Datatypes
39759 @subsection Protocol-specific Representation of Datatypes
39760 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39763 * Integral Datatypes::
39765 * Memory Transfer::
39770 @node Integral Datatypes
39771 @unnumberedsubsubsec Integral Datatypes
39772 @cindex integral datatypes, in file-i/o protocol
39774 The integral datatypes used in the system calls are @code{int},
39775 @code{unsigned int}, @code{long}, @code{unsigned long},
39776 @code{mode_t}, and @code{time_t}.
39778 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39779 implemented as 32 bit values in this protocol.
39781 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39783 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39784 in @file{limits.h}) to allow range checking on host and target.
39786 @code{time_t} datatypes are defined as seconds since the Epoch.
39788 All integral datatypes transferred as part of a memory read or write of a
39789 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39792 @node Pointer Values
39793 @unnumberedsubsubsec Pointer Values
39794 @cindex pointer values, in file-i/o protocol
39796 Pointers to target data are transmitted as they are. An exception
39797 is made for pointers to buffers for which the length isn't
39798 transmitted as part of the function call, namely strings. Strings
39799 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39806 which is a pointer to data of length 18 bytes at position 0x1aaf.
39807 The length is defined as the full string length in bytes, including
39808 the trailing null byte. For example, the string @code{"hello world"}
39809 at address 0x123456 is transmitted as
39815 @node Memory Transfer
39816 @unnumberedsubsubsec Memory Transfer
39817 @cindex memory transfer, in file-i/o protocol
39819 Structured data which is transferred using a memory read or write (for
39820 example, a @code{struct stat}) is expected to be in a protocol-specific format
39821 with all scalar multibyte datatypes being big endian. Translation to
39822 this representation needs to be done both by the target before the @code{F}
39823 packet is sent, and by @value{GDBN} before
39824 it transfers memory to the target. Transferred pointers to structured
39825 data should point to the already-coerced data at any time.
39829 @unnumberedsubsubsec struct stat
39830 @cindex struct stat, in file-i/o protocol
39832 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39833 is defined as follows:
39837 unsigned int st_dev; /* device */
39838 unsigned int st_ino; /* inode */
39839 mode_t st_mode; /* protection */
39840 unsigned int st_nlink; /* number of hard links */
39841 unsigned int st_uid; /* user ID of owner */
39842 unsigned int st_gid; /* group ID of owner */
39843 unsigned int st_rdev; /* device type (if inode device) */
39844 unsigned long st_size; /* total size, in bytes */
39845 unsigned long st_blksize; /* blocksize for filesystem I/O */
39846 unsigned long st_blocks; /* number of blocks allocated */
39847 time_t st_atime; /* time of last access */
39848 time_t st_mtime; /* time of last modification */
39849 time_t st_ctime; /* time of last change */
39853 The integral datatypes conform to the definitions given in the
39854 appropriate section (see @ref{Integral Datatypes}, for details) so this
39855 structure is of size 64 bytes.
39857 The values of several fields have a restricted meaning and/or
39863 A value of 0 represents a file, 1 the console.
39866 No valid meaning for the target. Transmitted unchanged.
39869 Valid mode bits are described in @ref{Constants}. Any other
39870 bits have currently no meaning for the target.
39875 No valid meaning for the target. Transmitted unchanged.
39880 These values have a host and file system dependent
39881 accuracy. Especially on Windows hosts, the file system may not
39882 support exact timing values.
39885 The target gets a @code{struct stat} of the above representation and is
39886 responsible for coercing it to the target representation before
39889 Note that due to size differences between the host, target, and protocol
39890 representations of @code{struct stat} members, these members could eventually
39891 get truncated on the target.
39893 @node struct timeval
39894 @unnumberedsubsubsec struct timeval
39895 @cindex struct timeval, in file-i/o protocol
39897 The buffer of type @code{struct timeval} used by the File-I/O protocol
39898 is defined as follows:
39902 time_t tv_sec; /* second */
39903 long tv_usec; /* microsecond */
39907 The integral datatypes conform to the definitions given in the
39908 appropriate section (see @ref{Integral Datatypes}, for details) so this
39909 structure is of size 8 bytes.
39912 @subsection Constants
39913 @cindex constants, in file-i/o protocol
39915 The following values are used for the constants inside of the
39916 protocol. @value{GDBN} and target are responsible for translating these
39917 values before and after the call as needed.
39928 @unnumberedsubsubsec Open Flags
39929 @cindex open flags, in file-i/o protocol
39931 All values are given in hexadecimal representation.
39943 @node mode_t Values
39944 @unnumberedsubsubsec mode_t Values
39945 @cindex mode_t values, in file-i/o protocol
39947 All values are given in octal representation.
39964 @unnumberedsubsubsec Errno Values
39965 @cindex errno values, in file-i/o protocol
39967 All values are given in decimal representation.
39992 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39993 any error value not in the list of supported error numbers.
39996 @unnumberedsubsubsec Lseek Flags
39997 @cindex lseek flags, in file-i/o protocol
40006 @unnumberedsubsubsec Limits
40007 @cindex limits, in file-i/o protocol
40009 All values are given in decimal representation.
40012 INT_MIN -2147483648
40014 UINT_MAX 4294967295
40015 LONG_MIN -9223372036854775808
40016 LONG_MAX 9223372036854775807
40017 ULONG_MAX 18446744073709551615
40020 @node File-I/O Examples
40021 @subsection File-I/O Examples
40022 @cindex file-i/o examples
40024 Example sequence of a write call, file descriptor 3, buffer is at target
40025 address 0x1234, 6 bytes should be written:
40028 <- @code{Fwrite,3,1234,6}
40029 @emph{request memory read from target}
40032 @emph{return "6 bytes written"}
40036 Example sequence of a read call, file descriptor 3, buffer is at target
40037 address 0x1234, 6 bytes should be read:
40040 <- @code{Fread,3,1234,6}
40041 @emph{request memory write to target}
40042 -> @code{X1234,6:XXXXXX}
40043 @emph{return "6 bytes read"}
40047 Example sequence of a read call, call fails on the host due to invalid
40048 file descriptor (@code{EBADF}):
40051 <- @code{Fread,3,1234,6}
40055 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40059 <- @code{Fread,3,1234,6}
40064 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40068 <- @code{Fread,3,1234,6}
40069 -> @code{X1234,6:XXXXXX}
40073 @node Library List Format
40074 @section Library List Format
40075 @cindex library list format, remote protocol
40077 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40078 same process as your application to manage libraries. In this case,
40079 @value{GDBN} can use the loader's symbol table and normal memory
40080 operations to maintain a list of shared libraries. On other
40081 platforms, the operating system manages loaded libraries.
40082 @value{GDBN} can not retrieve the list of currently loaded libraries
40083 through memory operations, so it uses the @samp{qXfer:libraries:read}
40084 packet (@pxref{qXfer library list read}) instead. The remote stub
40085 queries the target's operating system and reports which libraries
40088 The @samp{qXfer:libraries:read} packet returns an XML document which
40089 lists loaded libraries and their offsets. Each library has an
40090 associated name and one or more segment or section base addresses,
40091 which report where the library was loaded in memory.
40093 For the common case of libraries that are fully linked binaries, the
40094 library should have a list of segments. If the target supports
40095 dynamic linking of a relocatable object file, its library XML element
40096 should instead include a list of allocated sections. The segment or
40097 section bases are start addresses, not relocation offsets; they do not
40098 depend on the library's link-time base addresses.
40100 @value{GDBN} must be linked with the Expat library to support XML
40101 library lists. @xref{Expat}.
40103 A simple memory map, with one loaded library relocated by a single
40104 offset, looks like this:
40108 <library name="/lib/libc.so.6">
40109 <segment address="0x10000000"/>
40114 Another simple memory map, with one loaded library with three
40115 allocated sections (.text, .data, .bss), looks like this:
40119 <library name="sharedlib.o">
40120 <section address="0x10000000"/>
40121 <section address="0x20000000"/>
40122 <section address="0x30000000"/>
40127 The format of a library list is described by this DTD:
40130 <!-- library-list: Root element with versioning -->
40131 <!ELEMENT library-list (library)*>
40132 <!ATTLIST library-list version CDATA #FIXED "1.0">
40133 <!ELEMENT library (segment*, section*)>
40134 <!ATTLIST library name CDATA #REQUIRED>
40135 <!ELEMENT segment EMPTY>
40136 <!ATTLIST segment address CDATA #REQUIRED>
40137 <!ELEMENT section EMPTY>
40138 <!ATTLIST section address CDATA #REQUIRED>
40141 In addition, segments and section descriptors cannot be mixed within a
40142 single library element, and you must supply at least one segment or
40143 section for each library.
40145 @node Library List Format for SVR4 Targets
40146 @section Library List Format for SVR4 Targets
40147 @cindex library list format, remote protocol
40149 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40150 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40151 shared libraries. Still a special library list provided by this packet is
40152 more efficient for the @value{GDBN} remote protocol.
40154 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40155 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40156 target, the following parameters are reported:
40160 @code{name}, the absolute file name from the @code{l_name} field of
40161 @code{struct link_map}.
40163 @code{lm} with address of @code{struct link_map} used for TLS
40164 (Thread Local Storage) access.
40166 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40167 @code{struct link_map}. For prelinked libraries this is not an absolute
40168 memory address. It is a displacement of absolute memory address against
40169 address the file was prelinked to during the library load.
40171 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40174 Additionally the single @code{main-lm} attribute specifies address of
40175 @code{struct link_map} used for the main executable. This parameter is used
40176 for TLS access and its presence is optional.
40178 @value{GDBN} must be linked with the Expat library to support XML
40179 SVR4 library lists. @xref{Expat}.
40181 A simple memory map, with two loaded libraries (which do not use prelink),
40185 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40186 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40188 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40190 </library-list-svr>
40193 The format of an SVR4 library list is described by this DTD:
40196 <!-- library-list-svr4: Root element with versioning -->
40197 <!ELEMENT library-list-svr4 (library)*>
40198 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40199 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40200 <!ELEMENT library EMPTY>
40201 <!ATTLIST library name CDATA #REQUIRED>
40202 <!ATTLIST library lm CDATA #REQUIRED>
40203 <!ATTLIST library l_addr CDATA #REQUIRED>
40204 <!ATTLIST library l_ld CDATA #REQUIRED>
40207 @node Memory Map Format
40208 @section Memory Map Format
40209 @cindex memory map format
40211 To be able to write into flash memory, @value{GDBN} needs to obtain a
40212 memory map from the target. This section describes the format of the
40215 The memory map is obtained using the @samp{qXfer:memory-map:read}
40216 (@pxref{qXfer memory map read}) packet and is an XML document that
40217 lists memory regions.
40219 @value{GDBN} must be linked with the Expat library to support XML
40220 memory maps. @xref{Expat}.
40222 The top-level structure of the document is shown below:
40225 <?xml version="1.0"?>
40226 <!DOCTYPE memory-map
40227 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40228 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40234 Each region can be either:
40239 A region of RAM starting at @var{addr} and extending for @var{length}
40243 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40248 A region of read-only memory:
40251 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40256 A region of flash memory, with erasure blocks @var{blocksize}
40260 <memory type="flash" start="@var{addr}" length="@var{length}">
40261 <property name="blocksize">@var{blocksize}</property>
40267 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40268 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40269 packets to write to addresses in such ranges.
40271 The formal DTD for memory map format is given below:
40274 <!-- ................................................... -->
40275 <!-- Memory Map XML DTD ................................ -->
40276 <!-- File: memory-map.dtd .............................. -->
40277 <!-- .................................... .............. -->
40278 <!-- memory-map.dtd -->
40279 <!-- memory-map: Root element with versioning -->
40280 <!ELEMENT memory-map (memory | property)>
40281 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40282 <!ELEMENT memory (property)>
40283 <!-- memory: Specifies a memory region,
40284 and its type, or device. -->
40285 <!ATTLIST memory type CDATA #REQUIRED
40286 start CDATA #REQUIRED
40287 length CDATA #REQUIRED
40288 device CDATA #IMPLIED>
40289 <!-- property: Generic attribute tag -->
40290 <!ELEMENT property (#PCDATA | property)*>
40291 <!ATTLIST property name CDATA #REQUIRED>
40294 @node Thread List Format
40295 @section Thread List Format
40296 @cindex thread list format
40298 To efficiently update the list of threads and their attributes,
40299 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40300 (@pxref{qXfer threads read}) and obtains the XML document with
40301 the following structure:
40304 <?xml version="1.0"?>
40306 <thread id="id" core="0" name="name">
40307 ... description ...
40312 Each @samp{thread} element must have the @samp{id} attribute that
40313 identifies the thread (@pxref{thread-id syntax}). The
40314 @samp{core} attribute, if present, specifies which processor core
40315 the thread was last executing on. The @samp{name} attribute, if
40316 present, specifies the human-readable name of the thread. The content
40317 of the of @samp{thread} element is interpreted as human-readable
40318 auxiliary information.
40320 @node Traceframe Info Format
40321 @section Traceframe Info Format
40322 @cindex traceframe info format
40324 To be able to know which objects in the inferior can be examined when
40325 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40326 memory ranges, registers and trace state variables that have been
40327 collected in a traceframe.
40329 This list is obtained using the @samp{qXfer:traceframe-info:read}
40330 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40332 @value{GDBN} must be linked with the Expat library to support XML
40333 traceframe info discovery. @xref{Expat}.
40335 The top-level structure of the document is shown below:
40338 <?xml version="1.0"?>
40339 <!DOCTYPE traceframe-info
40340 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40341 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40347 Each traceframe block can be either:
40352 A region of collected memory starting at @var{addr} and extending for
40353 @var{length} bytes from there:
40356 <memory start="@var{addr}" length="@var{length}"/>
40360 A block indicating trace state variable numbered @var{number} has been
40364 <tvar id="@var{number}"/>
40369 The formal DTD for the traceframe info format is given below:
40372 <!ELEMENT traceframe-info (memory | tvar)* >
40373 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40375 <!ELEMENT memory EMPTY>
40376 <!ATTLIST memory start CDATA #REQUIRED
40377 length CDATA #REQUIRED>
40379 <!ATTLIST tvar id CDATA #REQUIRED>
40382 @node Branch Trace Format
40383 @section Branch Trace Format
40384 @cindex branch trace format
40386 In order to display the branch trace of an inferior thread,
40387 @value{GDBN} needs to obtain the list of branches. This list is
40388 represented as list of sequential code blocks that are connected via
40389 branches. The code in each block has been executed sequentially.
40391 This list is obtained using the @samp{qXfer:btrace:read}
40392 (@pxref{qXfer btrace read}) packet and is an XML document.
40394 @value{GDBN} must be linked with the Expat library to support XML
40395 traceframe info discovery. @xref{Expat}.
40397 The top-level structure of the document is shown below:
40400 <?xml version="1.0"?>
40402 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40403 "http://sourceware.org/gdb/gdb-btrace.dtd">
40412 A block of sequentially executed instructions starting at @var{begin}
40413 and ending at @var{end}:
40416 <block begin="@var{begin}" end="@var{end}"/>
40421 The formal DTD for the branch trace format is given below:
40424 <!ELEMENT btrace (block* | pt) >
40425 <!ATTLIST btrace version CDATA #FIXED "1.0">
40427 <!ELEMENT block EMPTY>
40428 <!ATTLIST block begin CDATA #REQUIRED
40429 end CDATA #REQUIRED>
40431 <!ELEMENT pt (pt-config?, raw?)>
40433 <!ELEMENT pt-config (cpu?)>
40435 <!ELEMENT cpu EMPTY>
40436 <!ATTLIST cpu vendor CDATA #REQUIRED
40437 family CDATA #REQUIRED
40438 model CDATA #REQUIRED
40439 stepping CDATA #REQUIRED>
40441 <!ELEMENT raw (#PCDATA)>
40444 @node Branch Trace Configuration Format
40445 @section Branch Trace Configuration Format
40446 @cindex branch trace configuration format
40448 For each inferior thread, @value{GDBN} can obtain the branch trace
40449 configuration using the @samp{qXfer:btrace-conf:read}
40450 (@pxref{qXfer btrace-conf read}) packet.
40452 The configuration describes the branch trace format and configuration
40453 settings for that format. The following information is described:
40457 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40460 The size of the @acronym{BTS} ring buffer in bytes.
40463 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40467 The size of the @acronym{Intel PT} ring buffer in bytes.
40471 @value{GDBN} must be linked with the Expat library to support XML
40472 branch trace configuration discovery. @xref{Expat}.
40474 The formal DTD for the branch trace configuration format is given below:
40477 <!ELEMENT btrace-conf (bts?, pt?)>
40478 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40480 <!ELEMENT bts EMPTY>
40481 <!ATTLIST bts size CDATA #IMPLIED>
40483 <!ELEMENT pt EMPTY>
40484 <!ATTLIST pt size CDATA #IMPLIED>
40487 @include agentexpr.texi
40489 @node Target Descriptions
40490 @appendix Target Descriptions
40491 @cindex target descriptions
40493 One of the challenges of using @value{GDBN} to debug embedded systems
40494 is that there are so many minor variants of each processor
40495 architecture in use. It is common practice for vendors to start with
40496 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40497 and then make changes to adapt it to a particular market niche. Some
40498 architectures have hundreds of variants, available from dozens of
40499 vendors. This leads to a number of problems:
40503 With so many different customized processors, it is difficult for
40504 the @value{GDBN} maintainers to keep up with the changes.
40506 Since individual variants may have short lifetimes or limited
40507 audiences, it may not be worthwhile to carry information about every
40508 variant in the @value{GDBN} source tree.
40510 When @value{GDBN} does support the architecture of the embedded system
40511 at hand, the task of finding the correct architecture name to give the
40512 @command{set architecture} command can be error-prone.
40515 To address these problems, the @value{GDBN} remote protocol allows a
40516 target system to not only identify itself to @value{GDBN}, but to
40517 actually describe its own features. This lets @value{GDBN} support
40518 processor variants it has never seen before --- to the extent that the
40519 descriptions are accurate, and that @value{GDBN} understands them.
40521 @value{GDBN} must be linked with the Expat library to support XML
40522 target descriptions. @xref{Expat}.
40525 * Retrieving Descriptions:: How descriptions are fetched from a target.
40526 * Target Description Format:: The contents of a target description.
40527 * Predefined Target Types:: Standard types available for target
40529 * Enum Target Types:: How to define enum target types.
40530 * Standard Target Features:: Features @value{GDBN} knows about.
40533 @node Retrieving Descriptions
40534 @section Retrieving Descriptions
40536 Target descriptions can be read from the target automatically, or
40537 specified by the user manually. The default behavior is to read the
40538 description from the target. @value{GDBN} retrieves it via the remote
40539 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40540 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40541 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40542 XML document, of the form described in @ref{Target Description
40545 Alternatively, you can specify a file to read for the target description.
40546 If a file is set, the target will not be queried. The commands to
40547 specify a file are:
40550 @cindex set tdesc filename
40551 @item set tdesc filename @var{path}
40552 Read the target description from @var{path}.
40554 @cindex unset tdesc filename
40555 @item unset tdesc filename
40556 Do not read the XML target description from a file. @value{GDBN}
40557 will use the description supplied by the current target.
40559 @cindex show tdesc filename
40560 @item show tdesc filename
40561 Show the filename to read for a target description, if any.
40565 @node Target Description Format
40566 @section Target Description Format
40567 @cindex target descriptions, XML format
40569 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40570 document which complies with the Document Type Definition provided in
40571 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40572 means you can use generally available tools like @command{xmllint} to
40573 check that your feature descriptions are well-formed and valid.
40574 However, to help people unfamiliar with XML write descriptions for
40575 their targets, we also describe the grammar here.
40577 Target descriptions can identify the architecture of the remote target
40578 and (for some architectures) provide information about custom register
40579 sets. They can also identify the OS ABI of the remote target.
40580 @value{GDBN} can use this information to autoconfigure for your
40581 target, or to warn you if you connect to an unsupported target.
40583 Here is a simple target description:
40586 <target version="1.0">
40587 <architecture>i386:x86-64</architecture>
40592 This minimal description only says that the target uses
40593 the x86-64 architecture.
40595 A target description has the following overall form, with [ ] marking
40596 optional elements and @dots{} marking repeatable elements. The elements
40597 are explained further below.
40600 <?xml version="1.0"?>
40601 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40602 <target version="1.0">
40603 @r{[}@var{architecture}@r{]}
40604 @r{[}@var{osabi}@r{]}
40605 @r{[}@var{compatible}@r{]}
40606 @r{[}@var{feature}@dots{}@r{]}
40611 The description is generally insensitive to whitespace and line
40612 breaks, under the usual common-sense rules. The XML version
40613 declaration and document type declaration can generally be omitted
40614 (@value{GDBN} does not require them), but specifying them may be
40615 useful for XML validation tools. The @samp{version} attribute for
40616 @samp{<target>} may also be omitted, but we recommend
40617 including it; if future versions of @value{GDBN} use an incompatible
40618 revision of @file{gdb-target.dtd}, they will detect and report
40619 the version mismatch.
40621 @subsection Inclusion
40622 @cindex target descriptions, inclusion
40625 @cindex <xi:include>
40628 It can sometimes be valuable to split a target description up into
40629 several different annexes, either for organizational purposes, or to
40630 share files between different possible target descriptions. You can
40631 divide a description into multiple files by replacing any element of
40632 the target description with an inclusion directive of the form:
40635 <xi:include href="@var{document}"/>
40639 When @value{GDBN} encounters an element of this form, it will retrieve
40640 the named XML @var{document}, and replace the inclusion directive with
40641 the contents of that document. If the current description was read
40642 using @samp{qXfer}, then so will be the included document;
40643 @var{document} will be interpreted as the name of an annex. If the
40644 current description was read from a file, @value{GDBN} will look for
40645 @var{document} as a file in the same directory where it found the
40646 original description.
40648 @subsection Architecture
40649 @cindex <architecture>
40651 An @samp{<architecture>} element has this form:
40654 <architecture>@var{arch}</architecture>
40657 @var{arch} is one of the architectures from the set accepted by
40658 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40661 @cindex @code{<osabi>}
40663 This optional field was introduced in @value{GDBN} version 7.0.
40664 Previous versions of @value{GDBN} ignore it.
40666 An @samp{<osabi>} element has this form:
40669 <osabi>@var{abi-name}</osabi>
40672 @var{abi-name} is an OS ABI name from the same selection accepted by
40673 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40675 @subsection Compatible Architecture
40676 @cindex @code{<compatible>}
40678 This optional field was introduced in @value{GDBN} version 7.0.
40679 Previous versions of @value{GDBN} ignore it.
40681 A @samp{<compatible>} element has this form:
40684 <compatible>@var{arch}</compatible>
40687 @var{arch} is one of the architectures from the set accepted by
40688 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40690 A @samp{<compatible>} element is used to specify that the target
40691 is able to run binaries in some other than the main target architecture
40692 given by the @samp{<architecture>} element. For example, on the
40693 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40694 or @code{powerpc:common64}, but the system is able to run binaries
40695 in the @code{spu} architecture as well. The way to describe this
40696 capability with @samp{<compatible>} is as follows:
40699 <architecture>powerpc:common</architecture>
40700 <compatible>spu</compatible>
40703 @subsection Features
40706 Each @samp{<feature>} describes some logical portion of the target
40707 system. Features are currently used to describe available CPU
40708 registers and the types of their contents. A @samp{<feature>} element
40712 <feature name="@var{name}">
40713 @r{[}@var{type}@dots{}@r{]}
40719 Each feature's name should be unique within the description. The name
40720 of a feature does not matter unless @value{GDBN} has some special
40721 knowledge of the contents of that feature; if it does, the feature
40722 should have its standard name. @xref{Standard Target Features}.
40726 Any register's value is a collection of bits which @value{GDBN} must
40727 interpret. The default interpretation is a two's complement integer,
40728 but other types can be requested by name in the register description.
40729 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40730 Target Types}), and the description can define additional composite
40733 Each type element must have an @samp{id} attribute, which gives
40734 a unique (within the containing @samp{<feature>}) name to the type.
40735 Types must be defined before they are used.
40738 Some targets offer vector registers, which can be treated as arrays
40739 of scalar elements. These types are written as @samp{<vector>} elements,
40740 specifying the array element type, @var{type}, and the number of elements,
40744 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40748 If a register's value is usefully viewed in multiple ways, define it
40749 with a union type containing the useful representations. The
40750 @samp{<union>} element contains one or more @samp{<field>} elements,
40751 each of which has a @var{name} and a @var{type}:
40754 <union id="@var{id}">
40755 <field name="@var{name}" type="@var{type}"/>
40762 If a register's value is composed from several separate values, define
40763 it with either a structure type or a flags type.
40764 A flags type may only contain bitfields.
40765 A structure type may either contain only bitfields or contain no bitfields.
40766 If the value contains only bitfields, its total size in bytes must be
40769 Non-bitfield values have a @var{name} and @var{type}.
40772 <struct id="@var{id}">
40773 <field name="@var{name}" type="@var{type}"/>
40778 Both @var{name} and @var{type} values are required.
40779 No implicit padding is added.
40781 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
40784 <struct id="@var{id}" size="@var{size}">
40785 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40791 <flags id="@var{id}" size="@var{size}">
40792 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40797 The @var{name} value is required.
40798 Bitfield values may be named with the empty string, @samp{""},
40799 in which case the field is ``filler'' and its value is not printed.
40800 Not all bits need to be specified, so ``filler'' fields are optional.
40802 The @var{start} and @var{end} values are required, and @var{type}
40804 The field's @var{start} must be less than or equal to its @var{end},
40805 and zero represents the least significant bit.
40807 The default value of @var{type} is @code{bool} for single bit fields,
40808 and an unsigned integer otherwise.
40810 Which to choose? Structures or flags?
40812 Registers defined with @samp{flags} have these advantages over
40813 defining them with @samp{struct}:
40817 Arithmetic may be performed on them as if they were integers.
40819 They are printed in a more readable fashion.
40822 Registers defined with @samp{struct} have one advantage over
40823 defining them with @samp{flags}:
40827 One can fetch individual fields like in @samp{C}.
40830 (gdb) print $my_struct_reg.field3
40836 @subsection Registers
40839 Each register is represented as an element with this form:
40842 <reg name="@var{name}"
40843 bitsize="@var{size}"
40844 @r{[}regnum="@var{num}"@r{]}
40845 @r{[}save-restore="@var{save-restore}"@r{]}
40846 @r{[}type="@var{type}"@r{]}
40847 @r{[}group="@var{group}"@r{]}/>
40851 The components are as follows:
40856 The register's name; it must be unique within the target description.
40859 The register's size, in bits.
40862 The register's number. If omitted, a register's number is one greater
40863 than that of the previous register (either in the current feature or in
40864 a preceding feature); the first register in the target description
40865 defaults to zero. This register number is used to read or write
40866 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40867 packets, and registers appear in the @code{g} and @code{G} packets
40868 in order of increasing register number.
40871 Whether the register should be preserved across inferior function
40872 calls; this must be either @code{yes} or @code{no}. The default is
40873 @code{yes}, which is appropriate for most registers except for
40874 some system control registers; this is not related to the target's
40878 The type of the register. It may be a predefined type, a type
40879 defined in the current feature, or one of the special types @code{int}
40880 and @code{float}. @code{int} is an integer type of the correct size
40881 for @var{bitsize}, and @code{float} is a floating point type (in the
40882 architecture's normal floating point format) of the correct size for
40883 @var{bitsize}. The default is @code{int}.
40886 The register group to which this register belongs. It must
40887 be either @code{general}, @code{float}, or @code{vector}. If no
40888 @var{group} is specified, @value{GDBN} will not display the register
40889 in @code{info registers}.
40893 @node Predefined Target Types
40894 @section Predefined Target Types
40895 @cindex target descriptions, predefined types
40897 Type definitions in the self-description can build up composite types
40898 from basic building blocks, but can not define fundamental types. Instead,
40899 standard identifiers are provided by @value{GDBN} for the fundamental
40900 types. The currently supported types are:
40905 Boolean type, occupying a single bit.
40912 Signed integer types holding the specified number of bits.
40919 Unsigned integer types holding the specified number of bits.
40923 Pointers to unspecified code and data. The program counter and
40924 any dedicated return address register may be marked as code
40925 pointers; printing a code pointer converts it into a symbolic
40926 address. The stack pointer and any dedicated address registers
40927 may be marked as data pointers.
40930 Single precision IEEE floating point.
40933 Double precision IEEE floating point.
40936 The 12-byte extended precision format used by ARM FPA registers.
40939 The 10-byte extended precision format used by x87 registers.
40942 32bit @sc{eflags} register used by x86.
40945 32bit @sc{mxcsr} register used by x86.
40949 @node Enum Target Types
40950 @section Enum Target Types
40951 @cindex target descriptions, enum types
40953 Enum target types are useful in @samp{struct} and @samp{flags}
40954 register descriptions. @xref{Target Description Format}.
40956 Enum types have a name, size and a list of name/value pairs.
40959 <enum id="@var{id}" size="@var{size}">
40960 <evalue name="@var{name}" value="@var{value}"/>
40965 Enums must be defined before they are used.
40968 <enum id="levels_type" size="4">
40969 <evalue name="low" value="0"/>
40970 <evalue name="high" value="1"/>
40972 <flags id="flags_type" size="4">
40973 <field name="X" start="0"/>
40974 <field name="LEVEL" start="1" end="1" type="levels_type"/>
40976 <reg name="flags" bitsize="32" type="flags_type"/>
40979 Given that description, a value of 3 for the @samp{flags} register
40980 would be printed as:
40983 (gdb) info register flags
40984 flags 0x3 [ X LEVEL=high ]
40987 @node Standard Target Features
40988 @section Standard Target Features
40989 @cindex target descriptions, standard features
40991 A target description must contain either no registers or all the
40992 target's registers. If the description contains no registers, then
40993 @value{GDBN} will assume a default register layout, selected based on
40994 the architecture. If the description contains any registers, the
40995 default layout will not be used; the standard registers must be
40996 described in the target description, in such a way that @value{GDBN}
40997 can recognize them.
40999 This is accomplished by giving specific names to feature elements
41000 which contain standard registers. @value{GDBN} will look for features
41001 with those names and verify that they contain the expected registers;
41002 if any known feature is missing required registers, or if any required
41003 feature is missing, @value{GDBN} will reject the target
41004 description. You can add additional registers to any of the
41005 standard features --- @value{GDBN} will display them just as if
41006 they were added to an unrecognized feature.
41008 This section lists the known features and their expected contents.
41009 Sample XML documents for these features are included in the
41010 @value{GDBN} source tree, in the directory @file{gdb/features}.
41012 Names recognized by @value{GDBN} should include the name of the
41013 company or organization which selected the name, and the overall
41014 architecture to which the feature applies; so e.g.@: the feature
41015 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41017 The names of registers are not case sensitive for the purpose
41018 of recognizing standard features, but @value{GDBN} will only display
41019 registers using the capitalization used in the description.
41022 * AArch64 Features::
41026 * MicroBlaze Features::
41030 * Nios II Features::
41031 * PowerPC Features::
41032 * S/390 and System z Features::
41037 @node AArch64 Features
41038 @subsection AArch64 Features
41039 @cindex target descriptions, AArch64 features
41041 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41042 targets. It should contain registers @samp{x0} through @samp{x30},
41043 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41045 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41046 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41050 @subsection ARC Features
41051 @cindex target descriptions, ARC Features
41053 ARC processors are highly configurable, so even core registers and their number
41054 are not completely predetermined. In addition flags and PC registers which are
41055 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41056 that one of the core registers features is present.
41057 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41059 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41060 targets with a normal register file. It should contain registers @samp{r0}
41061 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41062 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41063 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41064 @samp{ilink} and extension core registers are not available to read/write, when
41065 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41067 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41068 ARC HS targets with a reduced register file. It should contain registers
41069 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41070 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41071 This feature may contain register @samp{ilink} and any of extension core
41072 registers @samp{r32} through @samp{r59/acch}.
41074 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41075 targets with a normal register file. It should contain registers @samp{r0}
41076 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41077 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41078 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41079 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41080 registers are not available when debugging GNU/Linux applications. The only
41081 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41082 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41083 ARC v2, but @samp{ilink2} is optional on ARCompact.
41085 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41086 targets. It should contain registers @samp{pc} and @samp{status32}.
41089 @subsection ARM Features
41090 @cindex target descriptions, ARM features
41092 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41094 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41095 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41097 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41098 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41099 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41102 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41103 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41105 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41106 it should contain at least registers @samp{wR0} through @samp{wR15} and
41107 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41108 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41110 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41111 should contain at least registers @samp{d0} through @samp{d15}. If
41112 they are present, @samp{d16} through @samp{d31} should also be included.
41113 @value{GDBN} will synthesize the single-precision registers from
41114 halves of the double-precision registers.
41116 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41117 need to contain registers; it instructs @value{GDBN} to display the
41118 VFP double-precision registers as vectors and to synthesize the
41119 quad-precision registers from pairs of double-precision registers.
41120 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41121 be present and include 32 double-precision registers.
41123 @node i386 Features
41124 @subsection i386 Features
41125 @cindex target descriptions, i386 features
41127 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41128 targets. It should describe the following registers:
41132 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41134 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41136 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41137 @samp{fs}, @samp{gs}
41139 @samp{st0} through @samp{st7}
41141 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41142 @samp{foseg}, @samp{fooff} and @samp{fop}
41145 The register sets may be different, depending on the target.
41147 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41148 describe registers:
41152 @samp{xmm0} through @samp{xmm7} for i386
41154 @samp{xmm0} through @samp{xmm15} for amd64
41159 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41160 @samp{org.gnu.gdb.i386.sse} feature. It should
41161 describe the upper 128 bits of @sc{ymm} registers:
41165 @samp{ymm0h} through @samp{ymm7h} for i386
41167 @samp{ymm0h} through @samp{ymm15h} for amd64
41170 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41171 Memory Protection Extension (MPX). It should describe the following registers:
41175 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41177 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41180 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41181 describe a single register, @samp{orig_eax}.
41183 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41184 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41186 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41187 @samp{org.gnu.gdb.i386.avx} feature. It should
41188 describe additional @sc{xmm} registers:
41192 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41195 It should describe the upper 128 bits of additional @sc{ymm} registers:
41199 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41203 describe the upper 256 bits of @sc{zmm} registers:
41207 @samp{zmm0h} through @samp{zmm7h} for i386.
41209 @samp{zmm0h} through @samp{zmm15h} for amd64.
41213 describe the additional @sc{zmm} registers:
41217 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41220 @node MicroBlaze Features
41221 @subsection MicroBlaze Features
41222 @cindex target descriptions, MicroBlaze features
41224 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41225 targets. It should contain registers @samp{r0} through @samp{r31},
41226 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41227 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41228 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41230 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41231 If present, it should contain registers @samp{rshr} and @samp{rslr}
41233 @node MIPS Features
41234 @subsection @acronym{MIPS} Features
41235 @cindex target descriptions, @acronym{MIPS} features
41237 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41238 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41239 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41242 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41243 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41244 registers. They may be 32-bit or 64-bit depending on the target.
41246 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41247 it may be optional in a future version of @value{GDBN}. It should
41248 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41249 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41251 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41252 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41253 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41254 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41256 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41257 contain a single register, @samp{restart}, which is used by the
41258 Linux kernel to control restartable syscalls.
41260 @node M68K Features
41261 @subsection M68K Features
41262 @cindex target descriptions, M68K features
41265 @item @samp{org.gnu.gdb.m68k.core}
41266 @itemx @samp{org.gnu.gdb.coldfire.core}
41267 @itemx @samp{org.gnu.gdb.fido.core}
41268 One of those features must be always present.
41269 The feature that is present determines which flavor of m68k is
41270 used. The feature that is present should contain registers
41271 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41272 @samp{sp}, @samp{ps} and @samp{pc}.
41274 @item @samp{org.gnu.gdb.coldfire.fp}
41275 This feature is optional. If present, it should contain registers
41276 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41280 @node NDS32 Features
41281 @subsection NDS32 Features
41282 @cindex target descriptions, NDS32 features
41284 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41285 targets. It should contain at least registers @samp{r0} through
41286 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41289 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41290 it should contain 64-bit double-precision floating-point registers
41291 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41292 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41294 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41295 registers are overlapped with the thirty-two 32-bit single-precision
41296 floating-point registers. The 32-bit single-precision registers, if
41297 not being listed explicitly, will be synthesized from halves of the
41298 overlapping 64-bit double-precision registers. Listing 32-bit
41299 single-precision registers explicitly is deprecated, and the
41300 support to it could be totally removed some day.
41302 @node Nios II Features
41303 @subsection Nios II Features
41304 @cindex target descriptions, Nios II features
41306 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41307 targets. It should contain the 32 core registers (@samp{zero},
41308 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41309 @samp{pc}, and the 16 control registers (@samp{status} through
41312 @node PowerPC Features
41313 @subsection PowerPC Features
41314 @cindex target descriptions, PowerPC features
41316 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41317 targets. It should contain registers @samp{r0} through @samp{r31},
41318 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41319 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41321 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41322 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41324 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41325 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41328 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41329 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41330 will combine these registers with the floating point registers
41331 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41332 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41333 through @samp{vs63}, the set of vector registers for POWER7.
41335 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41336 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41337 @samp{spefscr}. SPE targets should provide 32-bit registers in
41338 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41339 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41340 these to present registers @samp{ev0} through @samp{ev31} to the
41343 @node S/390 and System z Features
41344 @subsection S/390 and System z Features
41345 @cindex target descriptions, S/390 features
41346 @cindex target descriptions, System z features
41348 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41349 System z targets. It should contain the PSW and the 16 general
41350 registers. In particular, System z targets should provide the 64-bit
41351 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41352 S/390 targets should provide the 32-bit versions of these registers.
41353 A System z target that runs in 31-bit addressing mode should provide
41354 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41355 register's upper halves @samp{r0h} through @samp{r15h}, and their
41356 lower halves @samp{r0l} through @samp{r15l}.
41358 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41359 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41362 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41363 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41365 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41366 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41367 targets and 32-bit otherwise. In addition, the feature may contain
41368 the @samp{last_break} register, whose width depends on the addressing
41369 mode, as well as the @samp{system_call} register, which is always
41372 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41373 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41374 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41376 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41377 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41378 combined by @value{GDBN} with the floating point registers @samp{f0}
41379 through @samp{f15} to present the 128-bit wide vector registers
41380 @samp{v0} through @samp{v15}. In addition, this feature should
41381 contain the 128-bit wide vector registers @samp{v16} through
41384 @node TIC6x Features
41385 @subsection TMS320C6x Features
41386 @cindex target descriptions, TIC6x features
41387 @cindex target descriptions, TMS320C6x features
41388 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41389 targets. It should contain registers @samp{A0} through @samp{A15},
41390 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41392 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41393 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41394 through @samp{B31}.
41396 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41397 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41399 @node Operating System Information
41400 @appendix Operating System Information
41401 @cindex operating system information
41407 Users of @value{GDBN} often wish to obtain information about the state of
41408 the operating system running on the target---for example the list of
41409 processes, or the list of open files. This section describes the
41410 mechanism that makes it possible. This mechanism is similar to the
41411 target features mechanism (@pxref{Target Descriptions}), but focuses
41412 on a different aspect of target.
41414 Operating system information is retrived from the target via the
41415 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41416 read}). The object name in the request should be @samp{osdata}, and
41417 the @var{annex} identifies the data to be fetched.
41420 @appendixsection Process list
41421 @cindex operating system information, process list
41423 When requesting the process list, the @var{annex} field in the
41424 @samp{qXfer} request should be @samp{processes}. The returned data is
41425 an XML document. The formal syntax of this document is defined in
41426 @file{gdb/features/osdata.dtd}.
41428 An example document is:
41431 <?xml version="1.0"?>
41432 <!DOCTYPE target SYSTEM "osdata.dtd">
41433 <osdata type="processes">
41435 <column name="pid">1</column>
41436 <column name="user">root</column>
41437 <column name="command">/sbin/init</column>
41438 <column name="cores">1,2,3</column>
41443 Each item should include a column whose name is @samp{pid}. The value
41444 of that column should identify the process on the target. The
41445 @samp{user} and @samp{command} columns are optional, and will be
41446 displayed by @value{GDBN}. The @samp{cores} column, if present,
41447 should contain a comma-separated list of cores that this process
41448 is running on. Target may provide additional columns,
41449 which @value{GDBN} currently ignores.
41451 @node Trace File Format
41452 @appendix Trace File Format
41453 @cindex trace file format
41455 The trace file comes in three parts: a header, a textual description
41456 section, and a trace frame section with binary data.
41458 The header has the form @code{\x7fTRACE0\n}. The first byte is
41459 @code{0x7f} so as to indicate that the file contains binary data,
41460 while the @code{0} is a version number that may have different values
41463 The description section consists of multiple lines of @sc{ascii} text
41464 separated by newline characters (@code{0xa}). The lines may include a
41465 variety of optional descriptive or context-setting information, such
41466 as tracepoint definitions or register set size. @value{GDBN} will
41467 ignore any line that it does not recognize. An empty line marks the end
41472 Specifies the size of a register block in bytes. This is equal to the
41473 size of a @code{g} packet payload in the remote protocol. @var{size}
41474 is an ascii decimal number. There should be only one such line in
41475 a single trace file.
41477 @item status @var{status}
41478 Trace status. @var{status} has the same format as a @code{qTStatus}
41479 remote packet reply. There should be only one such line in a single trace
41482 @item tp @var{payload}
41483 Tracepoint definition. The @var{payload} has the same format as
41484 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41485 may take multiple lines of definition, corresponding to the multiple
41488 @item tsv @var{payload}
41489 Trace state variable definition. The @var{payload} has the same format as
41490 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41491 may take multiple lines of definition, corresponding to the multiple
41494 @item tdesc @var{payload}
41495 Target description in XML format. The @var{payload} is a single line of
41496 the XML file. All such lines should be concatenated together to get
41497 the original XML file. This file is in the same format as @code{qXfer}
41498 @code{features} payload, and corresponds to the main @code{target.xml}
41499 file. Includes are not allowed.
41503 The trace frame section consists of a number of consecutive frames.
41504 Each frame begins with a two-byte tracepoint number, followed by a
41505 four-byte size giving the amount of data in the frame. The data in
41506 the frame consists of a number of blocks, each introduced by a
41507 character indicating its type (at least register, memory, and trace
41508 state variable). The data in this section is raw binary, not a
41509 hexadecimal or other encoding; its endianness matches the target's
41512 @c FIXME bi-arch may require endianness/arch info in description section
41515 @item R @var{bytes}
41516 Register block. The number and ordering of bytes matches that of a
41517 @code{g} packet in the remote protocol. Note that these are the
41518 actual bytes, in target order, not a hexadecimal encoding.
41520 @item M @var{address} @var{length} @var{bytes}...
41521 Memory block. This is a contiguous block of memory, at the 8-byte
41522 address @var{address}, with a 2-byte length @var{length}, followed by
41523 @var{length} bytes.
41525 @item V @var{number} @var{value}
41526 Trace state variable block. This records the 8-byte signed value
41527 @var{value} of trace state variable numbered @var{number}.
41531 Future enhancements of the trace file format may include additional types
41534 @node Index Section Format
41535 @appendix @code{.gdb_index} section format
41536 @cindex .gdb_index section format
41537 @cindex index section format
41539 This section documents the index section that is created by @code{save
41540 gdb-index} (@pxref{Index Files}). The index section is
41541 DWARF-specific; some knowledge of DWARF is assumed in this
41544 The mapped index file format is designed to be directly
41545 @code{mmap}able on any architecture. In most cases, a datum is
41546 represented using a little-endian 32-bit integer value, called an
41547 @code{offset_type}. Big endian machines must byte-swap the values
41548 before using them. Exceptions to this rule are noted. The data is
41549 laid out such that alignment is always respected.
41551 A mapped index consists of several areas, laid out in order.
41555 The file header. This is a sequence of values, of @code{offset_type}
41556 unless otherwise noted:
41560 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41561 Version 4 uses a different hashing function from versions 5 and 6.
41562 Version 6 includes symbols for inlined functions, whereas versions 4
41563 and 5 do not. Version 7 adds attributes to the CU indices in the
41564 symbol table. Version 8 specifies that symbols from DWARF type units
41565 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41566 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41568 @value{GDBN} will only read version 4, 5, or 6 indices
41569 by specifying @code{set use-deprecated-index-sections on}.
41570 GDB has a workaround for potentially broken version 7 indices so it is
41571 currently not flagged as deprecated.
41574 The offset, from the start of the file, of the CU list.
41577 The offset, from the start of the file, of the types CU list. Note
41578 that this area can be empty, in which case this offset will be equal
41579 to the next offset.
41582 The offset, from the start of the file, of the address area.
41585 The offset, from the start of the file, of the symbol table.
41588 The offset, from the start of the file, of the constant pool.
41592 The CU list. This is a sequence of pairs of 64-bit little-endian
41593 values, sorted by the CU offset. The first element in each pair is
41594 the offset of a CU in the @code{.debug_info} section. The second
41595 element in each pair is the length of that CU. References to a CU
41596 elsewhere in the map are done using a CU index, which is just the
41597 0-based index into this table. Note that if there are type CUs, then
41598 conceptually CUs and type CUs form a single list for the purposes of
41602 The types CU list. This is a sequence of triplets of 64-bit
41603 little-endian values. In a triplet, the first value is the CU offset,
41604 the second value is the type offset in the CU, and the third value is
41605 the type signature. The types CU list is not sorted.
41608 The address area. The address area consists of a sequence of address
41609 entries. Each address entry has three elements:
41613 The low address. This is a 64-bit little-endian value.
41616 The high address. This is a 64-bit little-endian value. Like
41617 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41620 The CU index. This is an @code{offset_type} value.
41624 The symbol table. This is an open-addressed hash table. The size of
41625 the hash table is always a power of 2.
41627 Each slot in the hash table consists of a pair of @code{offset_type}
41628 values. The first value is the offset of the symbol's name in the
41629 constant pool. The second value is the offset of the CU vector in the
41632 If both values are 0, then this slot in the hash table is empty. This
41633 is ok because while 0 is a valid constant pool index, it cannot be a
41634 valid index for both a string and a CU vector.
41636 The hash value for a table entry is computed by applying an
41637 iterative hash function to the symbol's name. Starting with an
41638 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41639 the string is incorporated into the hash using the formula depending on the
41644 The formula is @code{r = r * 67 + c - 113}.
41646 @item Versions 5 to 7
41647 The formula is @code{r = r * 67 + tolower (c) - 113}.
41650 The terminating @samp{\0} is not incorporated into the hash.
41652 The step size used in the hash table is computed via
41653 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41654 value, and @samp{size} is the size of the hash table. The step size
41655 is used to find the next candidate slot when handling a hash
41658 The names of C@t{++} symbols in the hash table are canonicalized. We
41659 don't currently have a simple description of the canonicalization
41660 algorithm; if you intend to create new index sections, you must read
41664 The constant pool. This is simply a bunch of bytes. It is organized
41665 so that alignment is correct: CU vectors are stored first, followed by
41668 A CU vector in the constant pool is a sequence of @code{offset_type}
41669 values. The first value is the number of CU indices in the vector.
41670 Each subsequent value is the index and symbol attributes of a CU in
41671 the CU list. This element in the hash table is used to indicate which
41672 CUs define the symbol and how the symbol is used.
41673 See below for the format of each CU index+attributes entry.
41675 A string in the constant pool is zero-terminated.
41678 Attributes were added to CU index values in @code{.gdb_index} version 7.
41679 If a symbol has multiple uses within a CU then there is one
41680 CU index+attributes value for each use.
41682 The format of each CU index+attributes entry is as follows
41688 This is the index of the CU in the CU list.
41690 These bits are reserved for future purposes and must be zero.
41692 The kind of the symbol in the CU.
41696 This value is reserved and should not be used.
41697 By reserving zero the full @code{offset_type} value is backwards compatible
41698 with previous versions of the index.
41700 The symbol is a type.
41702 The symbol is a variable or an enum value.
41704 The symbol is a function.
41706 Any other kind of symbol.
41708 These values are reserved.
41712 This bit is zero if the value is global and one if it is static.
41714 The determination of whether a symbol is global or static is complicated.
41715 The authorative reference is the file @file{dwarf2read.c} in
41716 @value{GDBN} sources.
41720 This pseudo-code describes the computation of a symbol's kind and
41721 global/static attributes in the index.
41724 is_external = get_attribute (die, DW_AT_external);
41725 language = get_attribute (cu_die, DW_AT_language);
41728 case DW_TAG_typedef:
41729 case DW_TAG_base_type:
41730 case DW_TAG_subrange_type:
41734 case DW_TAG_enumerator:
41736 is_static = language != CPLUS;
41738 case DW_TAG_subprogram:
41740 is_static = ! (is_external || language == ADA);
41742 case DW_TAG_constant:
41744 is_static = ! is_external;
41746 case DW_TAG_variable:
41748 is_static = ! is_external;
41750 case DW_TAG_namespace:
41754 case DW_TAG_class_type:
41755 case DW_TAG_interface_type:
41756 case DW_TAG_structure_type:
41757 case DW_TAG_union_type:
41758 case DW_TAG_enumeration_type:
41760 is_static = language != CPLUS;
41768 @appendix Manual pages
41772 * gdb man:: The GNU Debugger man page
41773 * gdbserver man:: Remote Server for the GNU Debugger man page
41774 * gcore man:: Generate a core file of a running program
41775 * gdbinit man:: gdbinit scripts
41781 @c man title gdb The GNU Debugger
41783 @c man begin SYNOPSIS gdb
41784 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41785 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41786 [@option{-b}@w{ }@var{bps}]
41787 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41788 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41789 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41790 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41791 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41794 @c man begin DESCRIPTION gdb
41795 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41796 going on ``inside'' another program while it executes -- or what another
41797 program was doing at the moment it crashed.
41799 @value{GDBN} can do four main kinds of things (plus other things in support of
41800 these) to help you catch bugs in the act:
41804 Start your program, specifying anything that might affect its behavior.
41807 Make your program stop on specified conditions.
41810 Examine what has happened, when your program has stopped.
41813 Change things in your program, so you can experiment with correcting the
41814 effects of one bug and go on to learn about another.
41817 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41820 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41821 commands from the terminal until you tell it to exit with the @value{GDBN}
41822 command @code{quit}. You can get online help from @value{GDBN} itself
41823 by using the command @code{help}.
41825 You can run @code{gdb} with no arguments or options; but the most
41826 usual way to start @value{GDBN} is with one argument or two, specifying an
41827 executable program as the argument:
41833 You can also start with both an executable program and a core file specified:
41839 You can, instead, specify a process ID as a second argument, if you want
41840 to debug a running process:
41848 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41849 named @file{1234}; @value{GDBN} does check for a core file first).
41850 With option @option{-p} you can omit the @var{program} filename.
41852 Here are some of the most frequently needed @value{GDBN} commands:
41854 @c pod2man highlights the right hand side of the @item lines.
41856 @item break [@var{file}:]@var{function}
41857 Set a breakpoint at @var{function} (in @var{file}).
41859 @item run [@var{arglist}]
41860 Start your program (with @var{arglist}, if specified).
41863 Backtrace: display the program stack.
41865 @item print @var{expr}
41866 Display the value of an expression.
41869 Continue running your program (after stopping, e.g. at a breakpoint).
41872 Execute next program line (after stopping); step @emph{over} any
41873 function calls in the line.
41875 @item edit [@var{file}:]@var{function}
41876 look at the program line where it is presently stopped.
41878 @item list [@var{file}:]@var{function}
41879 type the text of the program in the vicinity of where it is presently stopped.
41882 Execute next program line (after stopping); step @emph{into} any
41883 function calls in the line.
41885 @item help [@var{name}]
41886 Show information about @value{GDBN} command @var{name}, or general information
41887 about using @value{GDBN}.
41890 Exit from @value{GDBN}.
41894 For full details on @value{GDBN},
41895 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41896 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41897 as the @code{gdb} entry in the @code{info} program.
41901 @c man begin OPTIONS gdb
41902 Any arguments other than options specify an executable
41903 file and core file (or process ID); that is, the first argument
41904 encountered with no
41905 associated option flag is equivalent to a @option{-se} option, and the second,
41906 if any, is equivalent to a @option{-c} option if it's the name of a file.
41908 both long and short forms; both are shown here. The long forms are also
41909 recognized if you truncate them, so long as enough of the option is
41910 present to be unambiguous. (If you prefer, you can flag option
41911 arguments with @option{+} rather than @option{-}, though we illustrate the
41912 more usual convention.)
41914 All the options and command line arguments you give are processed
41915 in sequential order. The order makes a difference when the @option{-x}
41921 List all options, with brief explanations.
41923 @item -symbols=@var{file}
41924 @itemx -s @var{file}
41925 Read symbol table from file @var{file}.
41928 Enable writing into executable and core files.
41930 @item -exec=@var{file}
41931 @itemx -e @var{file}
41932 Use file @var{file} as the executable file to execute when
41933 appropriate, and for examining pure data in conjunction with a core
41936 @item -se=@var{file}
41937 Read symbol table from file @var{file} and use it as the executable
41940 @item -core=@var{file}
41941 @itemx -c @var{file}
41942 Use file @var{file} as a core dump to examine.
41944 @item -command=@var{file}
41945 @itemx -x @var{file}
41946 Execute @value{GDBN} commands from file @var{file}.
41948 @item -ex @var{command}
41949 Execute given @value{GDBN} @var{command}.
41951 @item -directory=@var{directory}
41952 @itemx -d @var{directory}
41953 Add @var{directory} to the path to search for source files.
41956 Do not execute commands from @file{~/.gdbinit}.
41960 Do not execute commands from any @file{.gdbinit} initialization files.
41964 ``Quiet''. Do not print the introductory and copyright messages. These
41965 messages are also suppressed in batch mode.
41968 Run in batch mode. Exit with status @code{0} after processing all the command
41969 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41970 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41971 commands in the command files.
41973 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41974 download and run a program on another computer; in order to make this
41975 more useful, the message
41978 Program exited normally.
41982 (which is ordinarily issued whenever a program running under @value{GDBN} control
41983 terminates) is not issued when running in batch mode.
41985 @item -cd=@var{directory}
41986 Run @value{GDBN} using @var{directory} as its working directory,
41987 instead of the current directory.
41991 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41992 @value{GDBN} to output the full file name and line number in a standard,
41993 recognizable fashion each time a stack frame is displayed (which
41994 includes each time the program stops). This recognizable format looks
41995 like two @samp{\032} characters, followed by the file name, line number
41996 and character position separated by colons, and a newline. The
41997 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41998 characters as a signal to display the source code for the frame.
42001 Set the line speed (baud rate or bits per second) of any serial
42002 interface used by @value{GDBN} for remote debugging.
42004 @item -tty=@var{device}
42005 Run using @var{device} for your program's standard input and output.
42009 @c man begin SEEALSO gdb
42011 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42012 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42013 documentation are properly installed at your site, the command
42020 should give you access to the complete manual.
42022 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42023 Richard M. Stallman and Roland H. Pesch, July 1991.
42027 @node gdbserver man
42028 @heading gdbserver man
42030 @c man title gdbserver Remote Server for the GNU Debugger
42032 @c man begin SYNOPSIS gdbserver
42033 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42035 gdbserver --attach @var{comm} @var{pid}
42037 gdbserver --multi @var{comm}
42041 @c man begin DESCRIPTION gdbserver
42042 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42043 than the one which is running the program being debugged.
42046 @subheading Usage (server (target) side)
42049 Usage (server (target) side):
42052 First, you need to have a copy of the program you want to debug put onto
42053 the target system. The program can be stripped to save space if needed, as
42054 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42055 the @value{GDBN} running on the host system.
42057 To use the server, you log on to the target system, and run the @command{gdbserver}
42058 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42059 your program, and (c) its arguments. The general syntax is:
42062 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42065 For example, using a serial port, you might say:
42069 @c @file would wrap it as F</dev/com1>.
42070 target> gdbserver /dev/com1 emacs foo.txt
42073 target> gdbserver @file{/dev/com1} emacs foo.txt
42077 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42078 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42079 waits patiently for the host @value{GDBN} to communicate with it.
42081 To use a TCP connection, you could say:
42084 target> gdbserver host:2345 emacs foo.txt
42087 This says pretty much the same thing as the last example, except that we are
42088 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42089 that we are expecting to see a TCP connection from @code{host} to local TCP port
42090 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42091 want for the port number as long as it does not conflict with any existing TCP
42092 ports on the target system. This same port number must be used in the host
42093 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42094 you chose a port number that conflicts with another service, @command{gdbserver} will
42095 print an error message and exit.
42097 @command{gdbserver} can also attach to running programs.
42098 This is accomplished via the @option{--attach} argument. The syntax is:
42101 target> gdbserver --attach @var{comm} @var{pid}
42104 @var{pid} is the process ID of a currently running process. It isn't
42105 necessary to point @command{gdbserver} at a binary for the running process.
42107 To start @code{gdbserver} without supplying an initial command to run
42108 or process ID to attach, use the @option{--multi} command line option.
42109 In such case you should connect using @kbd{target extended-remote} to start
42110 the program you want to debug.
42113 target> gdbserver --multi @var{comm}
42117 @subheading Usage (host side)
42123 You need an unstripped copy of the target program on your host system, since
42124 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42125 would, with the target program as the first argument. (You may need to use the
42126 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42127 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42128 new command you need to know about is @code{target remote}
42129 (or @code{target extended-remote}). Its argument is either
42130 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42131 descriptor. For example:
42135 @c @file would wrap it as F</dev/ttyb>.
42136 (gdb) target remote /dev/ttyb
42139 (gdb) target remote @file{/dev/ttyb}
42144 communicates with the server via serial line @file{/dev/ttyb}, and:
42147 (gdb) target remote the-target:2345
42151 communicates via a TCP connection to port 2345 on host `the-target', where
42152 you previously started up @command{gdbserver} with the same port number. Note that for
42153 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42154 command, otherwise you may get an error that looks something like
42155 `Connection refused'.
42157 @command{gdbserver} can also debug multiple inferiors at once,
42160 the @value{GDBN} manual in node @code{Inferiors and Programs}
42161 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42164 @ref{Inferiors and Programs}.
42166 In such case use the @code{extended-remote} @value{GDBN} command variant:
42169 (gdb) target extended-remote the-target:2345
42172 The @command{gdbserver} option @option{--multi} may or may not be used in such
42176 @c man begin OPTIONS gdbserver
42177 There are three different modes for invoking @command{gdbserver}:
42182 Debug a specific program specified by its program name:
42185 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42188 The @var{comm} parameter specifies how should the server communicate
42189 with @value{GDBN}; it is either a device name (to use a serial line),
42190 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42191 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42192 debug in @var{prog}. Any remaining arguments will be passed to the
42193 program verbatim. When the program exits, @value{GDBN} will close the
42194 connection, and @code{gdbserver} will exit.
42197 Debug a specific program by specifying the process ID of a running
42201 gdbserver --attach @var{comm} @var{pid}
42204 The @var{comm} parameter is as described above. Supply the process ID
42205 of a running program in @var{pid}; @value{GDBN} will do everything
42206 else. Like with the previous mode, when the process @var{pid} exits,
42207 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42210 Multi-process mode -- debug more than one program/process:
42213 gdbserver --multi @var{comm}
42216 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42217 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42218 close the connection when a process being debugged exits, so you can
42219 debug several processes in the same session.
42222 In each of the modes you may specify these options:
42227 List all options, with brief explanations.
42230 This option causes @command{gdbserver} to print its version number and exit.
42233 @command{gdbserver} will attach to a running program. The syntax is:
42236 target> gdbserver --attach @var{comm} @var{pid}
42239 @var{pid} is the process ID of a currently running process. It isn't
42240 necessary to point @command{gdbserver} at a binary for the running process.
42243 To start @code{gdbserver} without supplying an initial command to run
42244 or process ID to attach, use this command line option.
42245 Then you can connect using @kbd{target extended-remote} and start
42246 the program you want to debug. The syntax is:
42249 target> gdbserver --multi @var{comm}
42253 Instruct @code{gdbserver} to display extra status information about the debugging
42255 This option is intended for @code{gdbserver} development and for bug reports to
42258 @item --remote-debug
42259 Instruct @code{gdbserver} to display remote protocol debug output.
42260 This option is intended for @code{gdbserver} development and for bug reports to
42263 @item --debug-format=option1@r{[},option2,...@r{]}
42264 Instruct @code{gdbserver} to include extra information in each line
42265 of debugging output.
42266 @xref{Other Command-Line Arguments for gdbserver}.
42269 Specify a wrapper to launch programs
42270 for debugging. The option should be followed by the name of the
42271 wrapper, then any command-line arguments to pass to the wrapper, then
42272 @kbd{--} indicating the end of the wrapper arguments.
42275 By default, @command{gdbserver} keeps the listening TCP port open, so that
42276 additional connections are possible. However, if you start @code{gdbserver}
42277 with the @option{--once} option, it will stop listening for any further
42278 connection attempts after connecting to the first @value{GDBN} session.
42280 @c --disable-packet is not documented for users.
42282 @c --disable-randomization and --no-disable-randomization are superseded by
42283 @c QDisableRandomization.
42288 @c man begin SEEALSO gdbserver
42290 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42291 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42292 documentation are properly installed at your site, the command
42298 should give you access to the complete manual.
42300 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42301 Richard M. Stallman and Roland H. Pesch, July 1991.
42308 @c man title gcore Generate a core file of a running program
42311 @c man begin SYNOPSIS gcore
42312 gcore [-o @var{filename}] @var{pid}
42316 @c man begin DESCRIPTION gcore
42317 Generate a core dump of a running program with process ID @var{pid}.
42318 Produced file is equivalent to a kernel produced core file as if the process
42319 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42320 limit). Unlike after a crash, after @command{gcore} the program remains
42321 running without any change.
42324 @c man begin OPTIONS gcore
42326 @item -o @var{filename}
42327 The optional argument
42328 @var{filename} specifies the file name where to put the core dump.
42329 If not specified, the file name defaults to @file{core.@var{pid}},
42330 where @var{pid} is the running program process ID.
42334 @c man begin SEEALSO gcore
42336 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42337 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42338 documentation are properly installed at your site, the command
42345 should give you access to the complete manual.
42347 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42348 Richard M. Stallman and Roland H. Pesch, July 1991.
42355 @c man title gdbinit GDB initialization scripts
42358 @c man begin SYNOPSIS gdbinit
42359 @ifset SYSTEM_GDBINIT
42360 @value{SYSTEM_GDBINIT}
42369 @c man begin DESCRIPTION gdbinit
42370 These files contain @value{GDBN} commands to automatically execute during
42371 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42374 the @value{GDBN} manual in node @code{Sequences}
42375 -- shell command @code{info -f gdb -n Sequences}.
42381 Please read more in
42383 the @value{GDBN} manual in node @code{Startup}
42384 -- shell command @code{info -f gdb -n Startup}.
42391 @ifset SYSTEM_GDBINIT
42392 @item @value{SYSTEM_GDBINIT}
42394 @ifclear SYSTEM_GDBINIT
42395 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42397 System-wide initialization file. It is executed unless user specified
42398 @value{GDBN} option @code{-nx} or @code{-n}.
42401 the @value{GDBN} manual in node @code{System-wide configuration}
42402 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42405 @ref{System-wide configuration}.
42409 User initialization file. It is executed unless user specified
42410 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42413 Initialization file for current directory. It may need to be enabled with
42414 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42417 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42418 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42421 @ref{Init File in the Current Directory}.
42426 @c man begin SEEALSO gdbinit
42428 gdb(1), @code{info -f gdb -n Startup}
42430 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42431 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42432 documentation are properly installed at your site, the command
42438 should give you access to the complete manual.
42440 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42441 Richard M. Stallman and Roland H. Pesch, July 1991.
42447 @node GNU Free Documentation License
42448 @appendix GNU Free Documentation License
42451 @node Concept Index
42452 @unnumbered Concept Index
42456 @node Command and Variable Index
42457 @unnumbered Command, Variable, and Function Index
42462 % I think something like @@colophon should be in texinfo. In the
42464 \long\def\colophon{\hbox to0pt{}\vfill
42465 \centerline{The body of this manual is set in}
42466 \centerline{\fontname\tenrm,}
42467 \centerline{with headings in {\bf\fontname\tenbf}}
42468 \centerline{and examples in {\tt\fontname\tentt}.}
42469 \centerline{{\it\fontname\tenit\/},}
42470 \centerline{{\bf\fontname\tenbf}, and}
42471 \centerline{{\sl\fontname\tensl\/}}
42472 \centerline{are used for emphasis.}\vfill}
42474 % Blame: doc@@cygnus.com, 1991.